Summary of the invention
Based on this, being necessary affects its problem to the applicability of national grid for existing photovoltaic air-conditioning system, and a kind of photovoltaic DC-to-AC converter and photovoltaic air-conditioning system are provided.
A kind of photovoltaic DC-to-AC converter providing for realizing the object of the invention, comprises inverter circuit, and described inverter circuit comprises IPM module, and described IPM module is three-phase bridge circuit;
Described three-phase bridge circuit comprises the device for power switching with anti-paralleled diode;
Described device for power switching forms upper arm and underarm, and described upper arm and described underarm are a phase brachium pontis;
The described three-phase bridge circuit of three-phase brachium pontis formation in parallel;
Described three-phase bridge circuit can connect three phase mains or single phase poaer supply;
When described three-phase bridge circuit connects described three phase mains, described three phase mains accesses the described upper arm of each phase brachium pontis of described three-phase bridge circuit and the junction of described underarm;
When described three-phase bridge circuit connects described single phase poaer supply, described single phase poaer supply accesses in the three-phase brachium pontis of described three-phase bridge circuit the described upper arm of two-phase brachium pontis and the junction of described underarm arbitrarily.
In an embodiment, the described upper arm of the described two-phase brachium pontis being connected with described single phase poaer supply in described three-phase bridge circuit is without bridge construction therein.
In an embodiment, described inverter circuit also comprises phase current sampling circuit, line voltage sampling circuit, busbar voltage sample circuit and dsp controller therein;
The output of described phase current sampling circuit, the output of the output of described line voltage sampling circuit and described busbar voltage sample circuit is all connected with the input of described dsp controller, the phase current of exporting for the described AC power that described phase current sampling circuit is gathered, the DC bus-bar voltage of the phase voltage of the described AC power output of described line voltage sampling circuit collection and the solar battery array output of described busbar voltage sample circuit collection inputs to described dsp controller;
Described dsp controller, according to the described phase current of described AC power output, the described DC bus-bar voltage of the described phase voltage of described AC power output and the output of described solar battery array, to described IPM module input pulse width modulation signal, control described device for power switching conducting or disconnection.
In an embodiment, described inverter circuit also comprises the first reactor, the second reactor and the 3rd reactor therein;
The first-phase of described three phase mains accesses the upper arm of first-phase brachium pontis and the junction of underarm of described three-phase bridge circuit through the first reactor;
The second-phase of described three phase mains accesses the upper arm of second-phase brachium pontis and the junction of underarm of described three-phase bridge circuit through the second reactor;
The third phase of described three phase mains accesses the upper arm of third phase brachium pontis and the junction of underarm of described three-phase bridge circuit through the 3rd reactor.
In an embodiment, described inverter circuit also comprises capacitance group and grading resistor therein, and described capacitance group is in parallel with described grading resistor;
The junction of the described upper arm of three-phase brachium pontis described in described three-phase bridge circuit is accessed in one end after described capacitance group is in parallel with described grading resistor, and the other end accesses the junction of the described underarm of three-phase brachium pontis described in described three-phase bridge circuit.
In an embodiment, also comprise booster circuit therein, the input of described booster circuit is electrically connected to the output of described solar battery array;
The output of described booster circuit, by DC bus, is electrically connected to the output of described inverter circuit.
In an embodiment, described booster circuit comprises the first control unit circuit, the first device for power switching, the first inductance, the first diode and the 3rd electric capacity therein;
The output of described the first control unit circuit is connected with the input of described the first device for power switching, for inputting the first pulse width modulating signal to described the first device for power switching, controls conducting and the disconnection of described the first device for power switching;
The first output of described the first device for power switching is electrically connected to the output of described solar battery array, and the second output of described the first device for power switching is electrically connected to one end of described the first inductance;
One end of described the first diode is electrically connected to one end of described the first inductance, and the other end of described the first diode is connected with one end of described the 3rd electric capacity;
The other end of described the 3rd electric capacity is electrically connected to the other end of described the first inductance.
In an embodiment, described booster circuit comprises the second control unit, the second device for power switching, the second inductance, the second diode and the 4th electric capacity therein;
The output of described the second control unit is connected with the input of described the second device for power switching, for inputting the second pulse width modulating signal to described the second device for power switching, controls conducting and the disconnection of described the second device for power switching;
The first output of described the second device for power switching is electrically connected to one end of described the second inductance;
The second output of described the second device for power switching, is connected with the other end of described the second inductance by described solar battery array;
One end of described the second diode is electrically connected to the second output of described the second device for power switching, and the other end of described the second diode is electrically connected to one end of described the 4th electric capacity;
The other end of described the 4th electric capacity is electrically connected to the second output of described the second device for power switching.
In an embodiment, described booster circuit comprises the 3rd control unit, the 3rd device for power switching, the 4th device for power switching, the 3rd inductance, the 4th inductance, the 3rd diode, the 4th diode and the 5th electric capacity therein;
The first output of described the 3rd control unit, the second output are connected with the input of described the 4th device for power switching with the input of described the 3rd device for power switching respectively;
The first output of described the 3rd device for power switching is electrically connected to one end of described the 3rd inductance, and the second output of described the 3rd device for power switching is electrically connected to the other end of described the 3rd inductance by described solar battery array;
The first output of described the 4th device for power switching is electrically connected to one end of described the 4th inductance, and the second output of described the 4th device for power switching is electrically connected to the other end of described the 4th inductance by described solar battery array;
One end of described the 3rd diode is electrically connected to one end of described the 3rd inductance, and the other end of described the 3rd diode is electrically connected to one end of described the 5th electric capacity;
One end of described the 4th diode is electrically connected to one end of described the 4th inductance, and the other end of described the 4th diode is electrically connected to one end of described the 5th electric capacity;
The other end of described the 5th electric capacity is electrically connected to the second output of described the 4th device for power switching.
Accordingly, the present invention also provides a kind of photovoltaic air-conditioning system, comprises above-mentioned any photovoltaic DC-to-AC converter.
The beneficial effect of above-mentioned photovoltaic DC-to-AC converter and photovoltaic air-conditioning system: it by arranging the photovoltaic DC-to-AC converter with inverter circuit in photovoltaic air-conditioning system, and this inverter circuit comprises the IPM module of three-phase bridge circuit.Its three-phase bridge circuit is become by the set of power switches with anti-paralleled diode.The device for power switching with anti-paralleled diode forms upper arm and the underarm of three-phase bridge circuit, and upper arm and underarm are a phase brachium pontis.By the above-mentioned brachium pontis of three-phase, form three-phase bridge circuit, thereby being connected of three phase mains and photovoltaic DC-to-AC converter realized in the three-phase that makes the three phase mains upper arm of three-phase brachium pontis and the junction of underarm of corresponding access three-phase bridge circuit respectively.Make photovoltaic air-conditioning system be applicable to three phase mains.
And, when photovoltaic air-conditioning system need to be used single phase poaer supply, only in the three-phase brachium pontis of need control three-phase bridge circuit, any upper arm of two-phase brachium pontis and the junction of underarm are connected with single phase poaer supply, can realize being connected of single phase poaer supply and photovoltaic DC-to-AC converter, and then realize being connected of photovoltaic air-conditioning system and single phase poaer supply.It,, by controlling the connected mode of the IPM module of the inverter circuit in photovoltaic DC-to-AC converter, can make photovoltaic air-conditioning system be applicable to three phase mains and single phase poaer supply simultaneously, has improved the adaptability of photovoltaic air-conditioning system.Efficiently solve existing photovoltaic air-conditioning system and affect its problem to the applicability of national grid.
Embodiment
For making technical solution of the present invention clearer, below in conjunction with drawings and the specific embodiments, the present invention is described in further details.
It should be noted that, while relating to the first-phase, second-phase of three phase mains and third phase in following examples, all take first-phase as R phase, second-phase is S phase, and third phase is that T is mutually for example describes.
Photovoltaic DC-to-AC converter as a specific embodiment, comprises inverter circuit, and inverter circuit comprises IPM module, and IPM module is three-phase bridge circuit.Three-phase bridge circuit comprises the device for power switching with anti-paralleled diode.Device for power switching forms upper arm and underarm, and upper arm and underarm are a phase brachium pontis.The three-phase brachium pontis three-phase bridge circuit that forms in parallel.
Three-phase bridge circuit can connect three phase mains or single phase poaer supply.When three-phase bridge circuit connects three phase mains, the upper arm of each phase brachium pontis and the junction of underarm of three phase mains access three-phase bridge circuit.
When three-phase bridge circuit connects single phase poaer supply, any upper arm of two-phase brachium pontis and the junction of underarm in the three-phase brachium pontis of single phase poaer supply access three-phase bridge circuit.
It by arranging the photovoltaic DC-to-AC converter with inverter circuit in photovoltaic air-conditioning system, and this inverter circuit comprises the IPM module of three-phase bridge circuit.Its three-phase bridge circuit is become by the set of power switches with anti-paralleled diode.The device for power switching with anti-paralleled diode forms upper arm and the underarm of three-phase bridge circuit, and upper arm and underarm are a phase brachium pontis.By the above-mentioned brachium pontis of three-phase, form three-phase bridge circuit, thereby make the three-phase of three phase mains access respectively the upper arm of three-phase brachium pontis and the junction of underarm of three-phase bridge circuit, realize being connected of three phase mains and photovoltaic DC-to-AC converter.Make photovoltaic air-conditioning system be applicable to three phase mains.
And, when photovoltaic air-conditioning system need to be used single phase poaer supply, only in the three-phase brachium pontis of need control three-phase bridge circuit, any upper arm of two-phase brachium pontis and the junction of underarm are connected with single phase poaer supply, can realize being connected of single phase poaer supply and photovoltaic DC-to-AC converter, and then realize being connected of photovoltaic air-conditioning system and single phase poaer supply.It,, by controlling the connected mode of the IPM module of the inverter circuit in photovoltaic DC-to-AC converter, can make photovoltaic air-conditioning system be applicable to three phase mains and single phase poaer supply simultaneously, has improved the adaptability of photovoltaic air-conditioning system.Efficiently solve existing photovoltaic air-conditioning system and affect its problem to the applicability of national grid.
Wherein, device for power switching can be IGBT (Insulated Gate Bipolar Transistor, insulated gate bipolar transistor), the compound full-control type voltage driven type power semiconductor that it is comprised of BJT (double pole triode) and MOS (insulating gate type field effect tube), has the advantage of the high input impedance of MOSFET and low conduction voltage drop two aspects of GTR concurrently.
Concrete, when AC power is three phase mains, referring to Fig. 1, device for power switching Q1 and anti-paralleled diode D1 form the first upper arm of three-phase bridge circuit.Device for power switching Q2 and anti-paralleled diode D2 form the first underarm of three-phase bridge circuit.The first upper arm and the first underarm are connected in series the first-phase brachium pontis that forms three-phase bridge circuit.
Device for power switching Q3 and anti-paralleled diode D3 form the second upper arm of three-phase bridge circuit.Device for power switching Q4 and anti-paralleled diode D4 form the second underarm of three-phase bridge circuit.The second upper arm and the second underarm are connected in series the second-phase brachium pontis that forms three-phase bridge circuit.
Device for power switching Q5 and anti-paralleled diode D5 form the 3rd upper arm of three-phase bridge circuit.Device for power switching Q6 and anti-paralleled diode D6 form the 3rd underarm of three-phase bridge circuit.The 3rd upper arm and the 3rd underarm are connected in series the third phase brachium pontis that forms three-phase bridge circuit.
Above-mentioned three-phase brachium pontis (first-phase brachium pontis, second-phase brachium pontis and the third phase brachium pontis) three-phase bridge circuit that forms in parallel.
When AC power is three phase mains, the first-phase R of three phase mains can pass through the first reactor L mutuallyraccess the junction Ua of the first upper arm and the first underarm.The second-phase S of three phase mains can pass through the second reactor L mutuallysaccess the junction Ub of the second upper arm and the second underarm.The third phase T of three phase mains can pass through the 3rd reactor L mutuallytaccess the junction Uc of the 3rd upper arm and the 3rd underarm.Thereby realize being connected of photovoltaic DC-to-AC converter and three phase mains.
Meanwhile, the DC side parallel of three-phase bridge circuit has capacitance group C, and this capacitance group C is for filtering.
When photovoltaic DC-to-AC converter works in inversion grid connection pattern, this capacitance group C carries out filtering to the direct current of solar battery array output.
When photovoltaic DC-to-AC converter works in full-controlled rectifier pattern, this capacitance group C carries out filtering to the direct current after photovoltaic DC-to-AC converter inversion.
And the DC side of three-phase bridge circuit is parallel with grading resistor simultaneously, this grading resistor can be comprised of two resistance that are connected in series, and referring to Fig. 1, this grading resistor can be R13 and the R14 being connected in series.
Its concrete connected mode is: the junction of the upper arm of three-phase brachium pontis (first-phase brachium pontis, second-phase brachium pontis and third phase brachium pontis) in one end access three-phase bridge circuit after capacitance group C is in parallel with grading resistor, the junction of the underarm of three-phase brachium pontis in other end access three-phase bridge circuit.Wherein, capacitance group C and grading resistor are similarly and are connected in parallel.
Meanwhile, inverter circuit also comprises phase current sampling circuit, line voltage sampling circuit, busbar voltage sample circuit and dsp controller.
The output of phase current sampling circuit, the output of the output of line voltage sampling circuit and busbar voltage sample circuit is all connected with the input of dsp controller, the phase current of exporting for the AC power that phase current sampling circuit is gathered, the DC bus-bar voltage of the phase voltage of the AC power output of line voltage sampling circuit collection and the solar battery array output of busbar voltage sample circuit collection inputs to dsp controller.
Dsp controller, according to the phase current of AC power output, the DC bus-bar voltage of the phase voltage of AC power output and solar battery array output, to IPM module input pulse width modulation signal, the conducting of power ratio control switching device or disconnection.
Concrete, referring to Fig. 1, phase current sampling circuit comprises first-phase (R phase) phase current (I being comprised of the first current sensor, the 9th resistance R 9, the tenth resistance R 10 and operational amplifier OP3r) sample circuit, and second-phase (S phase) phase current (I being formed by the second current sensor, the 11 resistance R the 11, the 12 resistance R 12 and operational amplifier OP4s) sample circuit.
Line voltage sampling circuit comprises by the first resistance R 1, the second resistance R 2, the 3rd resistance R 3, the 4th resistance R 4, the 5th resistance R 5, the 6th resistance R 6, the 7th resistance R 7, the 8th resistance R 8, and operational amplifier OP1, operational amplifier OP2 and reference voltage VrEFthe line voltage V formingrSwith line voltage VtRsample circuit.
Busbar voltage sample circuit can be comprised of grading resistor R13 and R14.
The first-phase phase current I of the AC power output gathering through phase current sampling circuitrwith second-phase phase current Isanalog quantity, the first-phase of the AC power output that line voltage sampling circuit gathers and the phase voltage V between second-phaserSand the phase voltage V between third phase and first-phasetRanalog quantity, and the DC bus-bar voltage of the solar battery array output that gathers of busbar voltage sample circuit (is the DC bus-bar voltage V of the DC side of photovoltaic DC-to-AC converterdC) analog quantity all by the input of dsp controller, input to dsp controller.
Dsp controller carries out three-phase PFC control method calculation process according to above-mentioned analog quantity, according to SPWM rule output pulse width modulation (Pulse Width Modulation, PWM) signal PWM1-PWM6.Pulse width modulating signal PWM1-PWM6 is conducting or the disconnection of power ratio control switching device Q1, device for power switching Q2, device for power switching Q3, device for power switching Q4, device for power switching Q5 and device for power switching Q6 respectively, make R phase, the S phase of three phase mains output, the phase current of T phase according to certain rule through the first reactor Lr, the second reactor Ls, the 3rd reactor Lt, and Q1-Q6 in device for power switching and fly-wheel diode (D1-D6) and the capacitance group C of conducting.At the first reactor Lr, the second reactor Ls, and the 3rd reactor Ltinterior storage power and releasing energy, thus make the current phase of R phase, S phase and T phase three-phase follow in real time corresponding voltage-phase, to reach the object that improves power factor.Also improve simultaneously and stablized DC bus-bar voltage VdCnumerical value in appointment.
What deserves to be explained is, dsp controller, through the control method calculation process of three-phase PFC, is finally respectively by the duty ratio of the PWM1-PWM6 of SPWM rule outputx=R, S, T).
When AC power is single phase poaer supply, can, by suitable software control, select any two-phase brachium pontis in three-phase brachium pontis as single-phase main topological circuit, can realize the photovoltaic DC-to-AC converter main circuit of single phase poaer supply.By the connected mode of each device for power switching and AC power in change three-phase bridge circuit, single phase poaer supply is accessed in the three-phase brachium pontis of three-phase bridge circuit to the upper arm of two-phase brachium pontis and the junction of underarm arbitrarily, can realize being connected of single phase poaer supply and photovoltaic DC-to-AC converter.
Its control procedure is as follows: select Q1 and Q2, Q3 and Q4, in tri-groups of Q5 and Q6 any two groups as single-phase main topological circuit.As: select Q1 and Q2, two groups of Q3 and Q4, while phase voltage sample circuit, phase current sampling circuit, the first reactor, the second reactor and the 3rd reactor be corresponding selection two-way also, only needs pulse-width signal PWM1-PWM4 work.Concrete:
Referring to Fig. 2, to select Q1 and Q2, two groups of Q3 and Q4 are example.Wherein, device for power switching Q1 and anti-paralleled diode D1 form the first upper arm of three-phase bridge circuit.Device for power switching Q2 and anti-paralleled diode D2 form the first underarm of three-phase bridge circuit.The first upper arm and the first underarm are connected in series the first-phase brachium pontis that forms three-phase bridge circuit.
Device for power switching Q3 and anti-paralleled diode D3 form the second upper arm of three-phase bridge circuit.Device for power switching Q4 and anti-paralleled diode D4 form the second underarm of three-phase bridge circuit.The second upper arm and the second underarm are connected in series the second-phase brachium pontis that forms three-phase bridge circuit.
The upper arm of first-phase brachium pontis and the junction of underarm the first reactor Lrbe connected with single phase poaer supply.The upper arm of second-phase brachium pontis and the junction of underarm the second reactor Lsbe connected with single phase poaer supply.
Meanwhile, the capacitance group C that is connected in parallel on three-phase bridge circuit DC side can be composed in series by the first capacitor C 1 and the second capacitor C 2.
Accordingly, phase current sampling circuit, line voltage sampling circuit and busbar voltage sample circuit can be selected corresponding two-way according to the device for power switching of selecting, the analog quantity that dsp controller is gathered respectively according to phase current sampling circuit, line voltage sampling circuit and busbar voltage sample circuit is carried out three-phase PFC control method calculation process, according to SPWM rule output pulse width modulation signal PWM1-PWM4.Pulse width modulating signal PWM1-PWM4 is conducting or the disconnection of power ratio control switching device Q1, device for power switching Q2, device for power switching Q3, device for power switching Q4 respectively.
In like manner, also can select Q1 and Q2, two groups of Q5 and Q6, or Q3 and Q4, two groups of Q5 and Q6.
Referring to Fig. 3, in order further to optimize the radiating effect of photovoltaic DC-to-AC converter, when realizing single-phase rectifier PFC function, inverter circuit also can adopt without bridge construction.The upper arm that is the two-phase brachium pontis that is connected with single phase poaer supply in three-phase bridge circuit is without bridge construction.
Because the upper arm of the two-phase brachium pontis being connected with single phase poaer supply is without bridge construction, thereby reduced the work of two device for power switching of upper arm, made the energy that consumes less, the heat of generation still less.And improved the efficiency of photovoltaic DC-to-AC converter.
According to the power output of solar battery array, the software work of photovoltaic DC-to-AC converter can be divided into rectification and grid-connected two states.The grid-connected module of commutation inversion (being inverter circuit) in photovoltaic DC-to-AC converter is the current transforming unit of energy capable of bidirectional flowing.Mainly realize the control to electrical network (AC power), when the power output deficiency of solar battery array, realize full-controlled rectifier, from electrical network power taking, supply air-conditioning unit consumed energy required.When the power output abundance of solar battery array, excess energy inversion telegram in reply net, realize grid-connected object.
Referring to Fig. 4, the three phase mains of take access photovoltaic DC-to-AC converter is example, and when photovoltaic DC-to-AC converter works in full-controlled rectifier pattern, inverter circuit works in full-controlled rectifier pattern equally.Now, energy flows into photovoltaic DC-to-AC converter by electrical network (now, electrical network output is three-phase electricity).The booster circuit on its circuit structure Wei San road, operation principle is: the R of take is example mutually, when device for power switching Q2 conducting, electric current from R through the first reactor Lr, flowing into device for power switching Q2, flow through diode D4 or diode D6, arrive S phase or T phase and the second reactor Lsor the 3rd reactor Lt.In device for power switching Q2 conduction period, the first reactor Lrcurrent rise, storage power; When device for power switching Q2 turn-offs, be stored in the first reactor Lrenergy through diode D1, flow into the capacitance group (being C1 and C2) on inverter DC bus, thereby realize energy, by electrical network, flow into photovoltaic DC-to-AC converter.
Under full-controlled rectifier pattern, the waveform phase that must regulate in real time the waveform phase of three-phase phase current Ix (x=R, S, T) to follow phase voltage Vx (x=R, S, T), thus improve power factor, reduce harmonic components and content.When photovoltaic DC-to-AC converter is connected with three phase mains, can realize independently outer voltage, the double closed-loop PID of current inner loop regulates.Respectively R phase, S phase and T are carried out to independent control mutually, when it has not only solved input voltage imbalance, the applicability problem of photovoltaic DC-to-AC converter to electrical network.Meanwhile, the software function when being also applicable to photovoltaic DC-to-AC converter and being connected with single phase poaer supply, has improved the versatility of software and hardware, has also greatly improved the reliability of photovoltaic DC-to-AC converter, strengthens the fault-tolerant ability of photovoltaic DC-to-AC converter to hardware.
Referring to Fig. 5, its control method adopts two closed loops (outer voltage, current inner loop) to control.Take R mutually as example describes.Outer shroud is Voltage loop, and major control inverter DC bus-bar voltage is fixed value VdC_REF.Interior ring is electric current loop, the current reference value I of R phaser_REFthe value and power reference Pm and the actual phase voltage Vx (x=R, S, T) that by outer voltage, through PID, control output obtain after multiplier M.Current reference value Ir_REFwith actual detected value Irdifference carry out PID control, after its Output rusults and actual phase voltage Vx (x=R, S, T) are added, after conversion, obtain the reference value V of each phase phase voltagepWM_X(x=R, S, T), then adopts SPWM modulator approach, by VpWM_X(x=R, S, T) makes comparisons with triangular carrier, produces the pwm signal of power ratio control switching device conducting or disconnection.
Referring to Fig. 6, when R is carried out to two closed-loop control mutually, the power ratio control switching device conducting of generation or the pwm signal of disconnection are respectively: the PWM2 signal of the PWM1 signal of power ratio control switching device Q1 and power ratio control switching device Q2.
When S is carried out to two closed-loop control mutually, the power ratio control switching device conducting of generation or the pwm signal of disconnection are: the PWM4 signal of the PWM3 signal of power ratio control switching device Q3 and power ratio control switching device Q4.
When T is carried out to two closed-loop control mutually, the power ratio control switching device conducting of generation or the pwm signal of disconnection are: the PWM6 signal of the PWM5 signal of power ratio control switching device Q5 and power ratio control switching device Q6.
It should be noted that, for each phase, the pwm signal of controlling upper arm device for power switching is complementary with the pwm signal of controlling underarm device for power switching.It is the conducting simultaneously of upper arm device for power switching and underarm device for power switching.
That is to say that the PWM1 signal of power ratio control switching device Q1 and the PWM2 signal of power ratio control switching device Q2 are complementary signal, device for power switching Q1 and device for power switching Q2 conducting simultaneously.The PWM4 signal of the PWM3 signal of power ratio control switching device Q3 and power ratio control switching device Q4 is similarly complementary signal, device for power switching Q3 and device for power switching Q4 conducting simultaneously.The PWM6 signal of the PWM5 signal of power ratio control switching device Q5 and power ratio control switching device Q6 is similarly complementary signal, device for power switching Q5 and device for power switching Q6 conducting simultaneously.
When photovoltaic DC-to-AC converter works in inversion grid connection pattern, inverter circuit works in inversion grid connection pattern equally.Now, energy flows into electrical network by photovoltaic DC-to-AC converter.Its operation principle is: because photovoltaic DC-to-AC converter is connected with line voltage, therefore, the output voltage of photovoltaic DC-to-AC converter is determined by line voltage, therefore can pass through the electric current of control inputs electrical network, reaches the object toward electrical network input power.Meanwhile, the current harmonic content of input electrical network must meet GB requirement, so the necessary phase place of detection of grid voltage simultaneously, to guarantee that the electric current of inputting electrical network reaches and the same requirement of homophase frequently of line voltage.
Referring to Fig. 7, the two closed-loop controls of same employing under inversion grid connection pattern.Outer shroud is Voltage loop, and major control inverter DC bus-bar voltage is fixed value VdC_REFand need be higher than line voltage.Interior ring is electric current loop, its reference value Ir_REFgiven by outer voltage and voltage phase-locked loop (Phase Locked Loop, PLL).By to current inner loop reference value Ir_REFwith actual detected value Irdifference carry out PI control, obtain the reference value of the every phase output voltage U of photovoltaic DC-to-AC converter x (x=a, b, c), adopt SPWM modulator approach, Ux (x=a, b, c) is made comparisons with triangular carrier, by SVPWM signal generator, produced the pwm signal of power ratio control switching device.Wherein, a, b, c difference corresponding R, S, T.
In like manner, for each phase, the pwm signal of controlling upper arm device for power switching is also complementary with the pwm signal of controlling underarm device for power switching, i.e. upper arm device for power switching and underarm device for power switching conducting simultaneously.PLL phase-locked loop, mainly for detection of each phase voltage phase place, reaches with line voltage with frequency homophase to reach the electric current of control inputs electrical network.
Referring to Fig. 8, while connecting single phase poaer supply for photovoltaic DC-to-AC converter, carry out the software control figure of two closed-loop controls.When photovoltaic DC-to-AC converter connects single phase poaer supply, same according to the power output of solar battery array, the software work of photovoltaic DC-to-AC converter can be divided into rectification and grid-connected two states.
When photovoltaic DC-to-AC converter works in full-controlled rectifier pattern, adopt two closed loops (outer voltage, current inner loop) to control.Outer shroud is Voltage loop, and major control inverter DC bus-bar voltage is fixed value VdC_REF.Interior ring is electric current loop, the current reference value I of R phaser_REFthe value and power reference Pm and the actual phase voltage Vx (x=R, S, T) that by outer voltage, through PID I, control output obtain after multiplier M.Current reference value Ir_REFwith actual detected value Irdifference carry out the control of PID II, after its Output rusults and actual phase voltage Vx (x=R, S, T) are added, after conversion, obtain the reference value V of each phase phase voltagepWM_X(x=R, S, T), then adopts SPWM modulator approach, by VpWM_X(x=R, S, T) makes comparisons with triangular carrier, produces the pwm signal of power ratio control switching device.
Referring to Fig. 9, when above-mentioned photovoltaic DC-to-AC converter is applied to photovoltaic air-conditioning system, connecting valve power supply on the DC bus of this system, direct voltage user interface, three-phase (single-phase) air-conditioning system etc.The Converting Unit of three-phase and single phase poaer supply (being photovoltaic DC-to-AC converter) difference, but its mode of operation is identical.It is according to the mode of operation of the output power photovoltaic DC-to-AC converter of solar battery array.Concrete:
By dsp controller, detect output voltage V pv and the output current Ipv of solar battery array, calculate the maximum power Ppv of solar battery array output.By maximum power Ppv and the air-conditioning unit consumed power P of the solar battery array output calculatingair-conditioningsubtract each other, draw the power of the grid-connected module of commutation inversion (inverter circuit), thereby determine the mode of operation of the grid-connected module of commutation inversion (inverter circuit).
Making Δ P is the power of the grid-connected module of commutation inversion (inverter circuit), Δ P=Ppv-Pair-conditioning.
When Δ P=0, the maximum power Ppv of solar battery array output is all for air-conditioning unit consumed power Pair-conditioning, the grid-connected module of commutation inversion is in holding state.
When Δ P>0, the maximum power Ppv of solar battery array output is greater than air-conditioning unit consumed power Pair-conditioning, the grid-connected module of commutation inversion works in inversion grid connection state.
When Δ P<0, the maximum power Ppv of solar battery array output is less than air-conditioning unit consumed power Pair-conditioning, the grid-connected module of commutation inversion works in full-controlled rectifier state.
As Ppv>0 and Pair-conditioning=0 o'clock, the standby of air-conditioning unit, the grid-connected module of commutation inversion works in inversion grid connection state.
As Ppv=0 and Pair-conditioningduring >0, air-conditioning consumed power is all taken from electrical network, and the grid-connected module of commutation inversion works in full-controlled rectifier state.
Adopt the photovoltaic air-conditioner control system of above-mentioned photovoltaic DC-to-AC converter to be applicable to three phase mains and single phase poaer supply simultaneously, not only can maximally utilise solar battery array generating, and when the power output of solar battery array is less than air-conditioning unit consumed power, from electrical network (three phase mains or single phase poaer supply), supply the energy lacking, run on mixed net PFC function.When the power output of solar battery array is greater than air-conditioning unit consumed power, unnecessary energy inversion feedback grid can be used for miscellaneous equipment, run on grid-connectedly or from net function, not only realize the optimal utilization of solar battery array generating, and can create considerable economic well-being of workers and staff.Meanwhile, also can be applicable to family expenses and the business air conditioner unit of the level power supplies such as different capacity (three phase mains or single phase poaer supply).
Referring to Fig. 9, it should be noted that, photovoltaic DC-to-AC converter also comprises booster circuit.The input of booster circuit is electrically connected to the output of solar battery array.
The output of booster circuit, by DC bus, is electrically connected to the output of inverter circuit.
Booster circuit in photovoltaic DC-to-AC converter, DC-DC voltage conversion circuit is mainly to control by the output voltage to solar battery array, realizes the maximum power point tracking (MPPT) of solar battery array.Thereby the power output of real-time ensuring solar battery array is peak power output, effectively improve the utilance of solar battery array.
As the booster circuit of a specific embodiment, referring to Figure 10, be step-up/step-down circuit, i.e. BOOST/BUCK circuit.It comprises the first control unit (not shown), the first device for power switching Q7, the first inductance L 1, the first diode D7 and the 3rd capacitor C 3.
The output of the first control unit is connected with the input of the first device for power switching Q7, for inputting the first pulse width modulating signal to the first device for power switching Q7, controls conducting and the disconnection of the first device for power switching Q7.
The first output of the first device for power switching Q7 is electrically connected to the output of solar battery array, and the second output of the first device for power switching Q7 is electrically connected to one end of the first inductance L 1.
One end of the first diode D7 is electrically connected to one end of the first inductance L 1, and the other end of the first diode D7 is connected with one end of the 3rd capacitor C 3.The other end of the 3rd capacitor C 3 is electrically connected to the other end of the first inductance L 1.
Its operation principle is: when the first device for power switching Q7 conducting, solar battery array makes its storing energy through Q7 to the first inductance L 1 power supply.Now electric current is i1, and direction as shown in figure 10.Meanwhile, the 3rd capacitor C 3 maintains output voltage substantially constant.
When controlling the first device for power switching Q7 disconnection, the energy of storing in the first inductance L 1 is to load Rloaddischarge, electric current is i2, and direction as shown in figure 10.The output voltage of booster circuit is:
Wherein, toncharacterize ON time, T characterizes switch periods.
If change conduction ratio α, both output voltage V of comparable solar battery array of the output voltage of booster circuitpVheight, the also output voltage V of comparable solar battery arraypVlow.When 0< α <0.5, the output voltage of booster circuit is less than the output voltage V of solar battery arraypV, be step-down.When 0.5< α <1, the output voltage of booster circuit is greater than the output voltage V of solar battery arraypV, for boosting.
By changing conduction ratio α, thereby the output energy of solar battery array is forwarded on DC bus.Wherein the control signal PWM7 of the first device for power switching Q7 is produced by the first control unit.
Wherein, the first control unit, by the flow through direct current of solar battery array output of above-mentioned booster circuit of basis, carries out outer voltage, two closed-loop adjustment of current inner loop, export variable control signal PWM7, thereby regulate solar battery array constantly to operate in maximum power point MPPT.
As the booster circuit of a specific embodiment, widened the output voltage range 280V-1000V of solar battery array.When intensity of illumination is large, when the output voltage of solar battery array is greater than the DC bus-bar voltage of appointment, realize BUCK buck functionality.When intensity of illumination hour, when the output voltage of solar battery array is less than the DC bus-bar voltage of appointment, realize BOOST boost function.
As the booster circuit of another specific embodiment, referring to Figure 11, comprise the second control unit, the second device for power switching Q8, the second inductance L 2, the second diode D8 and the 4th capacitor C 4.
The output of the second control unit is connected with the input of the second device for power switching Q8, for inputting the second pulse width modulating signal to the second device for power switching Q8, controls conducting and the disconnection of the second device for power switching Q8.
The first output of the second device for power switching Q8 is electrically connected to one end of the second inductance L 2.
The second output of the second device for power switching Q8, is connected with the other end of the second inductance L 2 by solar battery array.
One end of the second diode D8 is electrically connected to the second output of the second device for power switching Q8, and the other end of the second diode D8 is electrically connected to one end of the 4th capacitor C 4.
The other end of the 4th capacitor C 4 is electrically connected to the second output of the second device for power switching Q8.
The booster circuit that is single channel as the booster circuit of another specific embodiment.Its operation principle is: when the second device for power switching Q8 conducting, the electric current of second inductance L 2 of flowing through increases.Because inductance has the characteristic that electric current can not suddenly change, at the second device for power switching Q8 off period, the voltage producing in the second inductance L 2 adds the output voltage of solar battery array, through the second diode D8, in the 4th capacitor C 4, charge, thereby the energy of solar battery array output is forwarded on inverter DC bus.Wherein the control signal PWM8 of the second device for power switching Q8 is produced by the second control unit.
In like manner, the second control unit is by the flow through direct current of solar battery array output of booster circuit of above-mentioned single channel of basis, carry out outer voltage, two closed-loop adjustment of current inner loop, export variable control signal PWM8, thereby regulate solar battery array constantly to operate in maximum power point MPPT.
Booster circuit as another specific embodiment, referring to Figure 12, comprise the 3rd control unit, the 3rd device for power switching Q9, the 4th device for power switching Q10, the 3rd inductance L 3, the 4th inductance L 4, the 3rd diode D9, the 4th diode D10 and the 5th capacitor C 5.
The first output of the 3rd control unit, the second output are connected with the input of the 4th device for power switching Q10 with the input of the 3rd device for power switching Q9 respectively.
The first output of the 3rd device for power switching Q9 is electrically connected to one end of the 3rd inductance L 3, and the second output of the 3rd device for power switching Q9 is electrically connected to the other end of the 3rd inductance L 3 by solar battery array.
The first output of the 4th device for power switching Q10 is electrically connected to one end of the 4th inductance L 4, and the second output of the 4th device for power switching Q10 is electrically connected to the other end of the 4th inductance L 4 by solar battery array.
One end of the 3rd diode D9 is electrically connected to one end of the 3rd inductance L 3, and the other end of the 3rd diode D9 is electrically connected to one end of the 5th capacitor C 5.
One end of the 4th diode D10 is electrically connected to one end of the 4th inductance L 4, and the other end of the 4th diode D10 is electrically connected to one end of the 5th capacitor C 5.
The other end of the 5th capacitor C 5 is electrically connected to the second output of the 4th device for power switching Q10.
Booster circuit as another specific embodiment is two-way interleaved boost circuit, and the operation principle of two-way booster circuit is identical with the operation principle of the booster circuit of above-mentioned single channel, therefore repeats part and repeats no more.
It should be noted that, the pulse width modulating signal PWM9 and the PWM10 that control the 3rd device for power switching Q9 and the 4th device for power switching Q10 are produced by the 3rd control unit.Differing of PWM9 and PWM10 is 180 °.Owing to being that two-way is staggered, control, therefore, the Primary Component in circuit is only required to be half of rated capacity of corresponding device in the booster circuit of single channel as the rated capacity of the 3rd inductance, the 4th inductance, the 3rd diode, the 4th diode, the 3rd device for power switching Q9 and the 4th device for power switching Q10 etc.
In like manner, the 3rd control unit and the 4th control unit circuit are respectively by the flow through direct current of solar battery array output of above-mentioned two-way interleaved boost circuit of basis, carry out outer voltage, two closed-loop adjustment of current inner loop, export variable pulse width modulating signal PWM9 and PWM10, thereby regulate solar battery array constantly to operate in maximum power point MPPT.
The photovoltaic air-conditioning system that adopts above-mentioned any photovoltaic DC-to-AC converter, is three-phase bridge circuit by the inverter circuit arranging in photovoltaic DC-to-AC converter, has realized the object of the shared photovoltaic air-conditioning system of three phase mains and single phase poaer supply.Effectively solve existing photovoltaic air-conditioning system and be not suitable for three phase mains problem.
Meanwhile, by checking, adopt the photovoltaic air-conditioning system of above-mentioned any photovoltaic DC-to-AC converter, with respect to the capacity usage ratio lifting 97% of traditional frequency conversion air-conditioning.And can generate electricity by way of merging two or more grid systems, thereby improve power grid quality, power factor is 0.98, THDi (Total Harmonic Distortion of current on input, the Current harmonic distortion sum of input line) <5%.
The above embodiment has only expressed several execution mode of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to the scope of the claims of the present invention.It should be pointed out that for the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection range of patent of the present invention should be as the criterion with claims.