COMPUTER- IMPLEMENTED METHOD FOR MANAGING A VIRTUAL POWER PLANT
TECHNICAL FIELD
[0001 ] The present disclosure relates to distributed energy storage systems , and more particularly to a computer-implemented method for managing a virtual power plant , a site controller, a virtual power plant , and a computer program product .
BACKGROUND
[0002] A virtual power plant can comprise a large number of sites that can be used for power grid frequency balancing . In some applications , such as frequency containment reserve for disturbances ( FCR-D) , power grid frequency balancing may need to be performed with a small delay . However, many technical limitations can make this challenging .
SUMMARY
[0003] This summary is provided to introduce a selection of concepts in a s implif ied form that are further described below in the detailed description . This summary is not intended to identify key features or essential features of the claimed subj ect matter, nor is it intended to be used to limit the scope of the claimed subj ect matter . [0004] It is an obj ective to provide a computer-implemented method for managing a virtual power plant , a site controller , a virtual power plant , and a computer program product . The foregoing and other obj ectives are achieved by the features of the independent claims . Further implementation forms are apparent from the dependent claims , the description and the figures .
[0005] According to a first aspect, a computer-implemented method for controlling a virtual power plant , wherein the virtual power plant comprises at least one battery unit and a rectifier electrically coupled to the at least one battery unit and configured to charge and discharge the at least one battery unit , comprises : receiving a signal to enable a rectifier ramp down or ramp up preparation ; obtaining a rectifier ramp down or ramp up preparation voltage interval ; and performing rectifier ramp down or ramp up preparation by controlling the recti fier to set a rectifier output voltage within the recti fier ramp down or ramp up preparation voltage interval . The method can, for example , reduce the delay in rectifier ramp down or ramp up .
[0006] In an implementation form of the first aspect , the method further comprising, in response to the rectifier output voltage being within the rectifier ramp down or ramp up preparation voltage interval , transmitting, by a site of the virtual power plant , a signal indicating that the site is ready for rectifier ramp down or ramp up . [0007] In another implementation form of the first aspect , the method further compri ses , in response to receiving a regulation activation signal , ramping down the rectifier output voltage to discharge the at least one battery unit or ramping up the rectifier output voltage to charge the at least one battery unit according to the regulation activation signal .
[0008] In another implementation form of the first aspect , the method further compri ses , in response to receiving a signal to disable the rectifier ramp down or ramp up preparation after receiving the signal to enable the rectif ier ramp down or ramp up preparation, disabling the rectifier ramp down or ramp up preparation .
[0009] In another implementation form of the first aspect , the controlling the rectifier to set the rectifier output voltage within the rectifier ramp down or ramp up preparation voltage interval comprises at least one of : directly controlling the rectifier output voltage via a controller of the recti fier ; enabling a nobattery-charging mode of the rectifier, wherein the rectifier is configured to , when in the no-battery-charging mode , adj ust the rectifier output voltage so that the at least one battery unit is not substantially charged; and/or l imiting a charging current of the at least one battery unit .
[0010] In another implementation form of the first aspect , the method further comprises , after the ramping down the rectifier output voltage to discharge the at least one battery unit or the ramping up the rectif ier output voltage to charge the at least one battery unit according to the regulation activation signal , returning to nominal operation without rectifier ramp down or ramp up preparation .
[001 1 ] According to a second aspect , a computer-implemented method for managing a plurality of sites of a virtual power plant , wherein each site in the plurality of sites comprises at least one battery unit and a rectifier electrically coupled to the at least one battery unit and configured to charge and discharge the at least one battery unit , comprises : transmitting a signal to enable a recti fier ramp down or ramp up preparation to a first set of sites out of the plurality of sites of the virtual power plant ; in response detecting a need for a change in power grid frequency balancing, trans mitting a regulation activation signal to at least a second set of sites out of a plurality of sites of the virtual power plant , wherein the regulation activation signal instructs the second set of sites to ramp down the rectifier output voltage to discharge the at least one battery unit or to ramp up the rectifier output voltage to charge the at least one battery unit .
[001 2] In an implementation form of the second aspect , the method further comprises : in response detecting that the need for the change in power grid frequency balancing requires rectifier ramp down or ramp up preparation, transmitting the regulation activation signal to the first set of sites out of a plurality of sites of the virtual power plant .
[001 3] In another implementation form of the second aspect , the detecting the need for the change in power grid frequency balancing comprises : receiving an activation signal for power grid frequency balancing; and/or detecting a change in power grid frequency .
[0014] According to a third aspect , a site controller of a virtual power plant comprises at least one processor and at least one memory including computer program code , the at least one memory and the computer program code configured to , with the at least one processor, cause the site controller to perform the method according to the first aspect .
[001 5] According to a fourth aspect , a central controller of a virtual power plant comprises at least one processor and at least one memory including computer program code , the at least one memory and the computer program code conf igured to , with the at least one processor, cause the central controller to perform the method according to the second aspect .
[001 6] According to a fifth aspect , a virtual power plant comprises the site controller according to the third aspect and the central controller according to the fourth aspect .
[001 7] According to a sixth aspect , a computer program product comprises program code configured to perform the method according to the f irst aspect or the second aspect when the computer program product is executed on a computer .
[0018] Many of the attendant features wil l be more readily appreciated as they become better understood by reference to the following detailed description considered in connection with the accompanying drawings .
DESCRIPTION OF THE DRAWINGS
[0019] In the following, example embodiments are described in more detail with reference to the attached figures and drawings , in which :
[0020] Fig . 1 illustrates a flow chart representation of a method according to an embodiment ;
[0021 ] Fig . 2 illustrates a flow chart representation of a method according to an embodiment ;
[0022] Fig . 3 illustrates a schematic representation of a site of a virtual power plant according to an embodiment ;
[0023] Fig . 4 illustrates a plot representation of rectifier voltage according to a comparative example .
[0024] Fig . 5 illustrates a plot representation of rectifier voltage according to a comparative example .
[0025] Fig . 6 illustrates a plot representation of rectifier voltage according to an embodiment .
[0026] Fig . 7 illustrates a plot representation of rectifier voltage according to another embodiment . [0027] Fig . 8 illustrates a flow chart representation of an implementation of a method according to an embodiment ;
[0028] Fig . 9 illustrates a schematic representation of a site controller according to an embodiment ;
[0029] Fig . 10 illustrates a schematic representation of a central controller according to an embodiment ; and [0030] Fig . 11 illustrates a schematic representation of a virtual power plant according to an embodiment .
[0031 ] In the following, like reference numerals are used to des ignate li ke parts in the accompanying drawings .
DETAILED DESCRIPTION
[0032] In the following description, reference is made to the accompanying drawings , which form part of the disclosure , and in which are shown, by way of illustration, specific aspects in which the present disclosure may be placed . It is understood that other aspects may be utilised, and structural or logical changes may be made without departing from the scope of the present disclosure . The following detailed description, therefore , is not to be taken in a limiting sense , as the scope of the present disclosure is defined by the appended claims .
[0033] For instance , it is understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa . For example , if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or il lustrated in the f igures . On the other hand, for example , if a specific apparatus is described based on functional units , a corresponding method may include a step performing the described functionality, even if such step is not explicitly described or illustrated in the figures . Further, it is understood that the features of the various example aspects described herein may be combined with each other, unless specifically noted otherwise .
[0034] Fig . 1 illustrates a flow chart representation of a method according to an embodiment .
[0035] According to an embodiment , a computer-implemented method 100 for controlling a virtual power plant , wherein the virtual power plant comprises at least one battery unit and a rectifier electrically coupled to the at least one battery unit and configured to charge and di scharge the at least one battery unit , comprises receiving 101 a signal to enable a rectifier ramp down or ramp up preparation .
[0036] The virtual power plant (VPP) may comprise , for example , a distributed energy storage ( DES ) system .
[0037] The rectifier ramp down or ramp up preparation may also be referred to as launch control or similar . Similarly, ramping down or ramping up the rectifier output voltage may be referred to as "launching down" or "launching up" , respectively, or simply "launching" . [0038] For example , a site of the VPP can comprise the at least one battery unit and the rectif ier . Herein, a site may also be referred to as a physical asset , a node , a unit , a distributed energy resource , an asset , a battery site , or similar .
[0039] The at least one battery unit may also be referred to as at least one battery, a battery, or similar . [0040] Herein, a virtual power plant may refer to a distributed power plant comprising a plurality of sites . A VPP can aggregate the capacities of the plurality of sites .
[0041 ] The signal to enable a recti fier ramp down or ramp up preparation can be received by, for example , a site controller of a site of the VPP . The signal can be transmitted by, for example , another component of the site , a central controller, or any other part of the VPP .
[0042] The method 100 may further comprise obtaining 102 a rectifier ramp down or ramp up preparation voltage interval .
[0043] The obtaining 102 the rectifier ramp down or ramp up preparation voltage interval may comprise , for example, obtaining the interval from memory . The rectifier ramp down or ramp up preparation voltage interval may be , for example , preconfigured and stored in the memory . Alternatively, the rectifier ramp down or ramp up preparation voltage interval may be obtained by, for example , receiving the rectifier ramp down or ramp up preparation voltage interval in a message . [0044] The rectifier ramp down or ramp up preparation voltage interval may also be referred to as an accepted launch control interval (ALCI ) or similar .
[0045] The method 100 may further comprise performing 103 recti fier ramp down or ramp up preparation by controlling the rectifier to set a rectifier output voltage within the rectifier ramp down or ramp up preparation voltage interval .
[0046] The rectifier output voltage can be controlled in various ways , such as those disclosed herein . The recti fier output voltage can be controlled by, for example , a rectifier controller .
[0047] The rectifier output voltage can also be referred to as a rectifier voltage or similar .
[0048] According to an embodiment , the method 100 further comprises , in response to the rectifier output voltage being within the rectifier ramp down or ramp up preparation voltage interval , transmitting, by a site of the virtual power plant , a signal indicating that the site is ready for rectifier ramp down or ramp up .
[0049] The signal indicating that the site is ready for rectifier ramp down or ramp up can be transmitted by, for example , a site controller to a central controller .
[0050] For example , in telecommunications applications , simple network management protocol ( SNMP) can be used to transmit the signal indicating that the site is ready for rectifier ramp down or ramp up . In residential applications , for example , modbus transmission control protocol ( TCP) can be used .
[0051 ] According to an embodiment , the method 100 further comprises , in response to receiving a regulation activation signal , ramping down the rectifier output voltage to discharge the at least one battery unit or ramping up the rectifier output voltage to charge the at least one battery unit according to the regulation activation signal .
[0052] Recti fier ramp down and rectifier ramp up may also be referred to as ramp down and ramp up, respectively .
[0053] In response to a site can receiving the acti vation command, the real-time operating system (RTOS ) of the site can detect the incoming request on, for example , the input simple network management protocol ( SNMP ) buffer . The delay of this proces s can depend on hardware vendor and can be up to seconds .
[0054] The RTOS of the site can activate the needed rectifiers using, for example , gate driver metal-oxide- semiconductor field-effect transistors (MOSFETs ) and/or other needed electrical components to control the current flow in the desired direction in/from the at least one battery unit .
[0055] Fig . 2 illustrates a flow chart representation of a method according to an embodiment .
[0056] According to an embodiment , a computer-implemented method 200 for managing a plurality of s ites of a virtual power plant , wherein each site in the plurality of s ites comprises at least one battery unit and a rectifier electrically coupled to the at least one battery unit and configured to charge and discharge the at least one battery unit , comprises transmitting 201 a signal to enable a rectifier ramp down or ramp up preparation to a first set of sites out of the plurality of sites of the virtual power plant .
[0057] The s ignal to enable a rectif ier ramp down or ramp up preparation can be transmitted by, for example , a central controller or any other component /device of the VPP .
[0058] The first set of sites can comprise at least one site . In some embodiments , the first set of sites can comprise a first plurality of sites .
[0059] The method 200 may further comprise in response detecting a need for a change in power grid frequency balancing, transmitting 202 a regulation activation signal to at least a second set of sites out of a plurality of sites of the virtual power plant , wherein the regulation activation signal instructs the second set of sites to ramp down the rectifier output voltage to discharge the at least one battery unit or to ramp up the rectifier output voltage to charge the at least one battery unit .
[0060] The second set of s ites can compri se , for example , the first set of sites , a subset of the first set of sites , and/or sites that are not in the first set of sites . [0061 ] The regulation activation signal may comprise any signal that instructs the second set of sites to ramp down the rectifier output voltage to discharge the at least one battery unit or to ramp up the rectifier output voltage to charge the at least one battery unit . For example , the regulation activation signal may be a separate signal /message or be part of another sig- nal /message .
[0062] In some embodiments , the method 200 may comprise determining whether the recti fier ramp down or ramp up preparation is needed for the power grid frequency balancing . For example , if fast response is needed, the regulation activation signal can be transmitted at least to the first set of sites . I f fast response is not needed, the regulation activation signal can be transmitted to sites not in the first set of sites , such as sites that do not have rectifier ramp down or ramp up preparation activated .
[0063] According to an embodiment , the detecting the need for the change in power grid frequency balancing comprises : receiving an activation signal for power grid frequency balancing; and/or detecting a change in power grid frequency .
[0064] For example , the change in the power grid frequency should deviate enough from the baseline , such as 50 Hertz (Hz ) , for the VPP to react to the change . Otherwise , there may be no action .
[0065] For example , a change in activation level can be needed, and this can be detected by an apparatus of the VPP as , for example, a signal from the transmission system operator ( TSO) or directly from a hardware device measuring the power grid frequency .
[0066] The VPP can receive the signal and determine which sites to select for activation . The VPP can transmit the activation request to a site over, for example , an internet protocol ( I P) network .
[0067] According to an embodiment , the method 200 further comprises , in response detecting that the need for the change in power grid frequency balancing requires rectifier ramp down or ramp up preparation, transmitting the regulation activation signal to the first set of sites out of a plurality of s ites of the virtual power plant .
[0068] For example , if the grid frequency keeps decreasing and approaching, for example , 49 . 9 Hz , this can function as an indicator that the need for the change in power grid frequency balancing requires rectifier ramp down or ramp up preparation .
[0069] The need for the change in power grid frequency balancing can require rectifier ramp down or ramp up preparation when, for example , a fast response is needed . A fast response may be needed when, for example , in response to a frequency containment reserve for disturbances ( FCR-D) activation .
[0070] In the case of FCR-D, there may be no activation signal from the TSO . Instead, the VPP can perform frequency measurements and detect a change in power grid frequency . Thus , the VPP can detect the need for the change in power grid frequency balancing as the change in the power grid frequency and transmit the regulation activation signal to the f irst set of s ites out of the plurality of sites of the VPP .
[0071 ] In FCR-D, there may be an activation if the frequency deviation from the baseline , such as 50 . 0 Hz , is large enough . For example , the grid frequency being less than 49 . 9 Hz or greater than 50 . 1 Hz can result in up regulation activation and down regulation activation, respectively . This can be different from frequency containment reserve - normal ( FCR-N) which can always activate if the power grid frequency is not equal to the baseline .
[0072] At least some embodiments disclosed herein can reduce the delay from the site has receiving the signal to the current flowing in the desired direction either charging or discharging the at least one battery unit . Thus , the embodiments can be used to speed up the process to , for example , meet the requirements of FCR-D-like use-cases .
[0073] Fig . 3 illustrates a schematic representation of a site of a virtual power plant according to an embodiment .
[0074] A site 300 can comprise a rectifier 301 and at least one battery unit 302 . The rectifier 301 can be electrically coupled to the power grid . The rectifier
301 can be used to charge the at least one battery unit
302 using power from the power grid . [0075] The site 300 can further comprise at least one inverter 303 that can be electrically coupled to the at least one battery unit 302 and to the power grid . The at least one inverter 303 can be used to push electricity back to the power grid from the at least one battery unit 302 .
[0076] The rectifier 301 can convert the alternating current (AC) from the power grid to direct current ( DC) compatible with the site 300 . For example , the rectifier 301 can convert 230 -volt AC to 48 -volt DC . The recti fier 301 can also be used to drive a site load 304 .
[0077] The at least one battery unit 302 can be used to drive the site load 304 when being controlled to , and to receive charge from the rectifier 301 during recharge periods .
[0078] The at least one battery unit 302 can be discharged by, for example , feeding power from the at least one battery unit 302 to the power grid via the inverter 303 and/or by feeding power from the at least one battery unit 302 to the site load 304 .
[0079] The site load 304 can comprise , for example , various equipment consuming power, the type of the equipment can be essentially anything consuming electricity .
[0080] For example , the site 300 may be embodied in a base station of a telecommunication network . The site load 304 may comprise equipment of the base station . The at least one battery unit 302 can be used for power redundancy of the base station in addition to power grid frequency balancing .
[0081 ] For example , the site 300 may correspond to an electrical system of a building and may comprise DC equipment , such as heating, ventilation, and air conditioning (HVAC) equipment , fluid-based cooling equipment , variable speed motor equipment ( also known as variable frequency drives or VFD' s ) , LED lighting equipment , or auxiliary battery equipment , such as electric vehicle (EV) battery and related DC charging equipment , for example .
[0082] The site 300 may further comprise other components not illustrated in the embodiment of Fig . 3 . For example , in some embodiments , the site 300 may further comprise at least one inverter arranged between the at least one battery unit 302 and the site load 304 . For example , the site load 304 may comprise an AC site load and the at least one inverter may be configured to provide power to the AC site load from the at least one battery unit 302 .
[0083] According to an embodiment , the controlling the rectifier to set the rectifier output voltage within the recti fier ramp down or ramp up preparation voltage interval comprises at least one of : directly controlling the rectifier output voltage via a controller of the rectifier ; enabling a no-battery-charging mode of the rectifier, wherein the rectifier is configured to, when in the no-battery-charging mode , adj ust the rectifier output voltage so that the at least one battery unit is not substantially charged; and/or limiting a charging current of the at least one battery unit .
[0084] When the rectifier output voltage is adj usted so that the at least one battery unit is not substantially charged, the at least one battery unit can still be charged or discharged a small amount because of load fluctuations affecting the voltages but the charg- ing/discharging is close to zero .
[0085] The output terminal voltage of the at least one battery unit may not be externally controlled using, for example , a DC-DC converter . The at least one battery unit may be embodied in, for example , a battery management system (BMS ) based solution or the at least one battery unit may be coupled to a DC-DC converter not actively altering the output voltage of the at least one battery unit .
[0086] Altering the voltage of the rectifier output can be performed in various ways depending on, for example , the software implementation of the rectifier control .
[0087] For example , if the rectifier supports directly altering the rectifier output voltage , the VPP can write a new output voltage value in the recti fier control ler or the float voltage directly . The rectifier can then ramp up or down until this voltage is achieved .
[0088] I f the rectifier supports a so-called no-bat- tery-charging function, this functionality can adj ust the rectifier voltage dynamically so that the battery is not charged even with a fluctuating load . In this case , the no-battery-charging function can be enabled to adj ust the rectifier voltage .
[0089] I f the rectifier supports functionality to limit the battery charging current, which can be similar to the no-battery-charging functionality but it may be further possible to allow dynamic battery charging higher than 0 amps . In this case , the functionality can be enabled and a low value can be configured as the limit , such as 0 -2 amps .
[0090] Any other implementation of voltage regulation can also be possible and/or a combination of all of the above-mentioned methods can be used .
[0091 ] DES or other virtual power plant solution can control up to thousands of individual sites by sending out activation signals using, for example , an internet protocol ( I P) network . Herein, "activation" may refer to the switch over from charging the at least one battery unit to discharging the at least one battery unit or vice versa .
[0092] Different use-cases can require different reaction times from when the activation signal is sent to the sites until the actual current to/ from the battery unit is flowing in the desired direction . For use-cases like automatic frequency restoration reserve ( aFRR) , there may be no need to speed up the site activation time because the real-time requirements are not typically strict . For use-cases like FCR-D, there may be a requirement of activation . This requirement can be as short as 7 . 5 seconds . For some aspects of the VPP, the requirement can be even shorter . For example , for the " Static FCR-D" vers ion, there needs to be some activation already after 2 . 5 seconds . With these levels of requirements , many of current hardware implementations are too slow to activate charging or discharging without changes to the internal software in the rectifiers .
[0093] At least some embodiments disclose herein can reduce the delay of the activation .
[0094] Fig . 4 illustrates a plot representation of rectifier voltage according to a comparative example .
[0095] The charging, discharging, or keeping the state of charge of the battery ( called zero regulation) depends on the difference between the rectifier voltage and the battery voltage . I f the rectifier voltage is higher than the battery voltage, the battery is charged until a full state of charge . Here it is assumed that BMS or DC-DC converter restrictions have not been triggered .
[0096] To start charging or discharging the battery, a ramp up or ramp down for voltage output can be implemented via the rectifier . This ramp has typically a significant delay . Typically, the ramp-up ( increase in voltage ) is slower than the ramp-down .
[0097] In the comparative example of Fig . 4 , rectifier voltage is illustrated as a function of time during a ramp-down .
[0098] When the rectifier voltage is within range 410 , the battery is charging . When the recti fier voltage is within range 411 , the state of charge of the battery is steady. When the rectifier voltage is within range 412, the battery is discharging.
[0099] At point 401, the battery is in high-voltage steady state and the battery is charging. This can be the default setting for the rectifier controller.
[0100] At point 402, a signal is sent to the controller of the rectifier to start discharging the battery while the battery is in the high-voltage steady state. The rectifier voltage starts to ramp down.
[0101] At point 403, after many seconds or even minutes, the voltage has ramped down to a level that keeps the state of charge steady, i.e. not charging or discharging. For lithium f errophosphate (LFP) batteries, this is often around 50.2 volts (V) , depending on the state of charge and the current load on the system. [0102] At point 404, the rectifier voltage continues to ramp down to the point where the battery starts to discharge .
[0103] At point 405, the rectifier has a lower voltage than the battery and the battery is fully discharging.
[0104] The time delay 420 between points 402 and 404 can be several second or even minutes.
[0105] Fig. 5 illustrates a plot representation of rectifier voltage according to another comparative examp 1 e .
[0106] In the comparative example of Fig. 5, rectifier voltage is illustrated as a function of time during a ramp-up . [0107] At point 501, the battery is in a low-voltage steady state and the battery is discharging.
[0108] At point 502, a signal is sent to the rectifier controller to start battery charging while the battery is in the low-voltage steady state. The rectifier voltage starts to ramp up.
[0109] At point 503, after many seconds or even minutes, the rectifier voltage has ramped up to levels which keeps the battery state of charge steady, not charging or discharging. For LFP batteries this is often around 50.2V, depending on the state of charge and the current load on the system.
[0110] At point 504, the rectifier voltage continues to ramp up to the point where the battery starts to charge .
[0111] At point 505, the rectifier has now a higher voltage than the battery and the battery is fully charging .
[0112] The time delay 520 between points 502 and 504 can be several second or even minutes.
[0113] Fig. 6 illustrates a plot representation of rectifier voltage according to an embodiment.
[0114] In the embodiment of Fig. 6, rectifier voltage is illustrated as a function of time during a ramp-down. [0115] At point 401, the battery is in high voltage steady-state and the battery is charging. This can be the default setting for the rectifier.
[0116] At point 601, rectifier ramp down preparation is enabled, and the rectifier voltage is reduced until it is inside the rectifier ramp down preparation voltage interval 610. Now the ramp down preparation is ready.
[0117] Although 49.9 - 50.4 V is illustrated as an example of the rectifier ramp down preparation voltage interval 610 in the embodiment of Fig. 6, the rectifier ramp down preparation voltage interval 610 can correspond to any other voltages depending on, for example, the implementation of the at least one battery unit.
[0118] In the embodiment of Fig. 6, three different voltage end points 602_l, 602_2, 602_3 are illustrated for the rectifier ramp down preparation. In other embodiments, the rectifier ramp down preparation can leave the rectifier voltage to any voltage within the rectifier ramp down preparation voltage interval 610.
[0119] When the rectifier voltage is inside the rectifier ramp down preparation voltage interval 610, it can be possible to perform up regulation (discharging the battery) quicker than, for example, from the point of high voltage steady-state 402.
[0120] Once the rectifier ramp down preparation is activated, the VPP can monitor the site with a short interval, such as every 5 seconds, until the site has reached the rectifier ramp down or ramp up preparation voltage interval. If the rectifier voltage is below the rectifier ramp down or ramp up preparation voltage interval, then in addition, the battery discharge functionality can be disabled.
[0121] When the rectifier ramp down or ramp up preparation voltage interval is reached, the site can signal indicating that the site is ready for rectifier ramp down or ramp up and normal monitoring can resume , for example every 5 minutes .
[0122] Ramping down the rectifier voltage can be performed in order to perform frequency balancing up regulation . When the rectifier voltage is ramped down, the at least one battery unit can be discharged for up regulation .
[0123] In some embodiments , the rectifier voltage can also be ramped up from the rectifier ramp down preparation voltage interval 610 . This can be done , for example , in response to rectifier ramp up being triggered . [0124] At point 404 , the rectifier voltage is low enough to discharge the battery .
[0125] At point 405 , the battery is fully discharging . [0126] As is illustrated in the embodiment of Fig . 6 , by performing the rectifier ramp down preparation, the delay 622 between the rectifier ramp down being triggered and the rectifier voltage being low enough to discharge the battery can be reduced compared to , for example , the delay 420 in the comparative example of Fig . 4 .
[0127] Fig . 7 illustrates a plot representation of rectifier voltage according to another embodiment .
[0128] In the embodiment of Fig . 7 , rectifier voltage is illustrated as a function of time during a ramp-up .
[0129] At point 501 , the battery is in a low-voltage steady-state and the battery is discharging . [01 30] At point 701 , rectifier ramp up preparation is enabled, and the rectifier voltage is increased until it is inside the rectif ier ramp up preparation voltage interval 710 . Now the ramp up preparation is ready .
[01 31 ] Although 49 . 9 - 50 . 4 V is illustrated as an example of the rectifier ramp up preparation voltage interval 710 in the embodiment of Fig . 7 , the rectifier ramp up preparation voltage interval 710 can correspond to any other voltages depending on, for example , the implementation of the at least one battery unit .
[01 32] In the embodiment of Fig . 7 , three different voltage end points 702_l , 702_2 , 702_3 are illustrated for the rectifier ramp up preparation . In other embodiments , the rectifier ramp up preparation can leave the rectifier voltage to any voltage within the rectifier ramp up preparation voltage interval 710 .
[01 33] When the rectifier voltage is inside the rectifier ramp up preparation voltage interval 710 , it can be possible to perform down regulation (discharging the battery) quicker than, for example , from the point of low-voltage steady-state 502 .
[01 34] Ramping up the rectifier voltage can be performed in order to perform frequency balancing down regulation . When the rectifier voltage is ramped up, the at least one battery unit can be charged for down regulation .
[01 35] In some embodiments , the rectifier voltage can be ramped down from the rectifier ramp up preparation voltage interval 710 . This can be done , for example , in response to rectifier ramp down being triggered .
[01 36] At point 504 , the rectifier voltage is high enough to charge the battery .
[01 37] At point 505 , the battery is fully charging .
[01 38] As is illustrated in the embodiment of Fig . 7 , by performing the rectifier ramp up preparation, the delay 722 between the rectifier ramp up being triggered and the rectifier voltage being high enough to charge the battery can be reduced compared to , for example , the delay 520 in the comparative example of Fig . 5 .
[01 39] Although the rectifier ramp down preparation and the rectifier ramp up preparation are illustrated as separate procedures in the embodiments of Figs . 6 and 7 , in some embodiments , the rectif ier ramp down preparation and the rectifier ramp up preparation can be combined into one procedure . For example , in some embodiments , the signal to enable a rectifier ramp down or ramp up preparation may not indicate whether recti fier ramp down or rectifier ramp up should be prepared . Thus , for example , the site may control the rectifier to set a recti fier output voltage within the rectif ier ramp down or ramp up preparation voltage interval based on whether the rectifier output voltage is below or above the rectifier ramp down or ramp up preparation voltage interval .
[0140] In other embodiments , the signal to enable a rectifier ramp down or ramp up preparation may indicate whether rectifier ramp down or rectifier ramp up should be prepared . For example , there may be a separate signal to enable a recti fier ramp down preparation and a separate signal to enable a rectifier ramp up preparation . Herein, a "signal to enable a rectifier ramp down or ramp up preparation" may refer to a signal that does not indicate whether rectifier ramp down or rectifier ramp up should be prepared or to a signal that indicates whether rectifier ramp down or rectifier ramp up should be prepared .
[0141 ] In some embodiments , the rectifier ramp down preparation voltage interval 610 can be different form the rectifier ramp up preparation voltage interval 710 . In other embodiments , the same interval can be used as the rectifier ramp down preparation voltage interval 610 and as the rectifier ramp up preparation voltage interval 710 . Any of these intervals can be referred to as a "rectifier ramp down or ramp up preparation voltage interval" .
[0142] It should be appreciated that the voltage values i llustrate in the embodiments of Figs . 6 and 7 are only exemplary and the voltage values may change based on, for example , the used battery technology . For example, sodium batteries may not use the same voltage values . However, any embodiment disclosed herein can also be used for such batteries . Further, sodium batteries may require the use of DC-DC converters because the natural voltage range of sodium batteries can be 2 . 5V to 4 . 5V per cell . A DC-DC converter can be used to make such sodium batteries compatible with sites using other voltages , such as 48V .
[0143] Fig . 8 illustrates a flow chart representation of an implementation of a method according to an embodiment .
[0144] The site can start 801 in nominal operation 802 . The site may not have ramp down/up preparation enabled and the rectifier voltage can have any value within the normal operations .
[0145] The VPP can enable launch control . The VPP can determine 803 whether the site needs to ramp up or down . The VPP can also determine the mechanism for ramping the voltage depending on, for example , the rectifier vendor and/or software version .
[0146] I f the rectifier voltage is above the ALCI , ramp down can be configured 804 . I f the rectifier voltage is below the ALCI , ramp up can be configured 805 .
[0147] Once the voltage is within the acceptable launch control interval , the launch control is ready 806 , and the VPP can signal the site is ready to launch . [0148] According to an embodiment , the method 100 further comprises , in response to receiving a signal to di sable the recti fier ramp down or ramp up preparation after receiving the signal to enable the rectifier ramp down or ramp up preparation, disabling the rectifier ramp down or ramp up preparation .
[0149] I f the site is now signaled to disable launch control 807 , the site can resume nominal operations 802 in the zero-regulation state (no charging, no discharging) .
[01 50] According to an embodiment , the method further comprises , after the ramping down the rectifier output voltage to discharge the at least one battery unit or the ramping up the rectifier output voltage to charge the at least one battery unit according to the regulation activation signal , returning to nominal operation without rectifier ramp down or ramp up preparation .
[01 51 ] I f rectifier ramp up or down is performed for a use-case that requires launch control , such as FCR-D, the VPP can select to activate sites amongst the sites with active launch control .
[01 52] The activated sites are now either in up or down regulation state 808 depending on the activation signal . The sites can return to nominal operations 802 whilst in the up or down regulation state and remain in this state until deactivated .
[01 53] When the sites are deactivated, they return as normal to the zero-regulation state and launch control is deactivated . I f the sites are again needed for thi s use-case , the VPP will re-enable launch control and the same cycle can repeat .
[01 54] Fig . 9 illustrates a schematic representation of a site controller according to an embodiment .
[01 55] According to an embodiment , a site controller 900 comprises at least one processor 901 and at least one memory 902 including computer program code , the at least one memory 902 and the computer program code configured to, with the at least one processor 901, cause the site controller 900 to perform the method 100.
[0156] The site controller 900 may comprise at least one processor 901. The at least one processor 901 may comprise, for example, one or more of various processing devices, such as a co-processor, a microprocessor, a digital signal processor (DSP) , a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) , a microprocessor unit (MCU) , a hardware accelerator, a special-purpose computer chip, or the like.
[0157] The site controller 900 may further comprise a memory 902. The memory 902 may be configured to store, for example, computer programs and the like. The memory 902 may comprise one or more volatile memory devices, one or more non-volatile memory devices, and/or a combination of one or more volatile memory devices and nonvolatile memory devices. For example, the memory 902 may be embodied as magnetic storage devices (such as hard disk drives, magnetic tapes, etc.) , optical magnetic storage devices, and semiconductor memories (such as mask ROM, PROM (programmable ROM) , EPROM (erasable PROM) , flash ROM, RAM (random access memory) , etc.) .
[0158] The site controller 900 may further comprise other components not illustrated in the embodiment of Fig . 9 . The site controller 900 may comprise , for example , an input/output bus for connecting the site controller 900 to other devices .
[01 59] When the site controller 900 is configured to implement some functionality, some component and/or components of the site controller 900 , such as the at least one processor 901 and/or the memory 902 , may be configured to implement this functionality . Furthermore, when the at least one processor 901 is configured to implement some functionality, this functionality may be implemented using program code comprised, for example , in the memory .
[0160] The site controller 900 may be implemented at least partially using, for example , a computer, some other site controller, or similar .
[0161 ] Fig . 10 illustrates a schematic representation of a central controller according to an embodiment .
[0162] According to an embodiment, a central controller 1000 comprises at least one processor 1001 and at least one memory 1002 including computer program code , the at least one memory 1002 and the computer program code configured to , with the at least one processor 1001 , cause the central controller 1000 to perform the method 200 .
[0163] The central controller 1000 may comprise at least one processor 1001 . The at least one processor 1001 may comprise , for example , one or more of various processing devices , such as a co-proces sor, a microprocessor, a digital signal processor ( DSP) , a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) , a microprocessor unit (MCU) , a hardware accelerator, a special-purpose computer chip, or the like. [0164] The central controller 1000 may further comprise a memory 1002. The memory 1002 may be configured to store, for example, computer programs and the like. The memory 1002 may comprise one or more volatile memory devices, one or more non-volatile memory devices, and/or a combination of one or more volatile memory devices and non-volatile memory devices. For example, the memory 1002 may be embodied as magnetic storage devices (such as hard disk drives, magnetic tapes, etc.) , optical magnetic storage devices, and semiconductor memories (such as mask ROM, PROM (programmable ROM) , EPROM (erasable PROM) , flash ROM, RAM (random access memory) , etc.) .
[0165] The central controller 1000 may further comprise other components not illustrated in the embodiment of Fig. 10. The central controller 1000 may comprise, for example, an input/output bus for connecting the central controller 1000 to other devices.
[0166] When the central controller 1000 is configured to implement some functionality, some component and/or components of the central controller 1000, such as the at least one processor 1001 and/or the memory 1002, may be configured to implement this functionality. Furthermore, when the at least one processor 1001 is configured to implement some functionality, this functionality may be implemented using program code comprised, for example , in the memory .
[0167] The central controller 1000 may be implemented at least partially using, for example , a computer, some other site controller, or similar .
[0168] Fig . 11 illustrates a schematic representation of a virtual power plant according to an embodiment .
[0169] According to an embodiment , a virtual power plant 1100 comprising the site controller 900 and the central controller 1000 .
[01 70] The central controller 1000 can function as a centrali zed control system for a plurality of sites 300 . Each site 300 can comprise the site controller 900 . The central controller 1000 can control each site according to the method 200 . The central controller 1000 may also be referred to as a centrali zed controller, a virtual power plant controller, a DES controller, a centrali zed control system, a virtual power plant control system, or similar .
[01 71 ] The virtual power plant 1100 may also be referred to as a virtual power plant system, a distributed energy storage system, or similar .
[01 72] Each site 300 in the plurality of sites may be coupled to the central controller 1000 and to a power grid 1101 . Each site 300 can be coupled to the central controller 1000 via, for example , a telecommunication network . Thus , the central controller 1000 may be configured to control each site in the plural ity of sites 300 according to the method 200 .
[01 73] Any range or device value given herein may be extended or altered without losing the effect sought . Also any embodiment may be combined with another embodiment unless explicitly disallowed .
[01 74] Although the subj ect matter has been described in language specific to structural features and/or acts , it is to be understood that the subj ect matter defined in the appended claims is not necessarily limited to the specific features or acts described above . Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims .
[01 75] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments . The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages . It wil l further be understood that reference to ' an ' item may refer to one or more of those items .
[01 76] The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate . Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subj ect matter described herein . Aspects of any of the embodiments described above may be combined with aspects of any of the other embodiments described to form further embodiments without losing the effect sought .
[01 77] The term ' comprising ' is used herein to mean including the method, blocks or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements .
[01 78] It will be understood that the above description is given by way of example only and that various modif ications may be made by those ski lled in the art . The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments . Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments , those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this specification .