技术领域technical field
本发明涉及一种发电机控制技术，特别涉及一种基于虚拟同步发电机的不平衡电压控制方法。The invention relates to a generator control technology, in particular to an unbalanced voltage control method based on a virtual synchronous generator.
背景技术Background technique
随着经济的快速发展，全球能源危机和环境问题的日益加强。同时，煤、石油等传统能源对环境的污染加重，因此，针对新能源合理应用的分布式发电得到越来越多的关注。由于大多数分布式能源都要通过逆变器接入电网，所以逆变器控制技术的研究显得尤为重要。伴随着更多的控制方法的研究与应用，一些更为先进的控制策略被逐步应用在系统中。其中，智能控制更是被越来越广泛的应用。With the rapid development of the economy, the global energy crisis and environmental problems are increasingly intensified. At the same time, traditional energy sources such as coal and oil have aggravated environmental pollution. Therefore, distributed power generation for the rational application of new energy sources has received more and more attention. Since most distributed energy sources are connected to the grid through inverters, the research on inverter control technology is particularly important. With the research and application of more control methods, some more advanced control strategies are gradually applied in the system. Among them, intelligent control is more and more widely used.
虚拟同步发电机，是在基于电力电子逆变器并网的分布式发电系统中，借助配备的储能环节，并采用适当的并网逆变器控制算法，使基于并网逆变器的分布式电源从外特性上模拟或部分模拟出同步发电机的频率及电压控制特性，从而改善分布式系统的稳定性。The virtual synchronous generator is based on the distributed power generation system connected to the grid based on the power electronic inverter. With the help of the equipped energy storage link and the appropriate control algorithm of the grid-connected inverter, the distribution based on the grid-connected inverter The type power supply simulates or partially simulates the frequency and voltage control characteristics of the synchronous generator from the external characteristics, so as to improve the stability of the distributed system.
大部分控制都是在电网平衡条件下进行的，未考虑不平衡条件。电网实际运行时，电网不平衡现象经常发生，若在逆变器控制策略设计过程中，未对不平衡情况进行设计。若电网发生不平衡现象，会使逆变器性能下降，严重时会导致逆变器损坏。其中，电网三相不平衡是逆变器设计中主要考虑的方面Most of the control is carried out under the balanced condition of the grid, and the unbalanced condition is not considered. During the actual operation of the power grid, the unbalanced phenomenon of the power grid often occurs. If the unbalanced situation is not designed during the design process of the inverter control strategy. If the power grid is unbalanced, the performance of the inverter will decrease, and in severe cases, the inverter will be damaged. Among them, the three-phase unbalance of the power grid is the main consideration in the design of the inverter.
当电网出现不平衡时，不平衡的电网电压会使逆变器输出电压也同样出现不平衡情况，使输出电压含有负序分量，从而影响三相逆变器的正常运行。通过抑制负序电压分量来使电压达到平衡。When the grid is unbalanced, the unbalanced grid voltage will cause the inverter output voltage to also be unbalanced, causing the output voltage to contain negative sequence components, thereby affecting the normal operation of the three-phase inverter. The voltage is balanced by suppressing the negative sequence voltage component.
发明内容Contents of the invention
本发明是针对电网不平衡影响三相逆变器的正常运行的问题，提出了一种基于虚拟同步发电机的不平衡电压控制方法，在虚拟同步发电机的基础上，在离网条件下对L型滤波器提供一种平衡电压控制方法，该方法在原有虚拟同步发电机控制方法的基础上，提出一种负序电压控制策略。该方法可以使系统在不平衡的条件下迅速有效地达到平衡。The invention aims at the problem that the unbalanced power grid affects the normal operation of the three-phase inverter, and proposes an unbalanced voltage control method based on a virtual synchronous generator. The L-type filter provides a balanced voltage control method, which proposes a negative sequence voltage control strategy based on the original virtual synchronous generator control method. This method can make the system reach equilibrium quickly and effectively under the condition of imbalance.
本发明的技术方案为：一种基于虚拟同步发电机的不平衡电压控制方法，虚拟同步发电机三相并网逆变器包括直流电压源U、三相逆变器、L滤波器、检测L滤波器输出端电压的电压检测器、检测三相逆变器输出电流的电流检测器、虚拟励磁机、虚拟电动机、功率检测器、虚拟同步发电机算法模块、电压正负序分离模块及PWM驱动模块，直流电压源电压进入三相逆变器，经过转换产生交流电压，产生的电压送入L滤波器，滤波后输出并网端，系统控制方法具体如下：The technical solution of the present invention is: an unbalanced voltage control method based on a virtual synchronous generator. The three-phase grid-connected inverter of the virtual synchronous generator includes a DC voltage source U, a three-phase inverter, an L filter, and a detection L Voltage detector for filter output voltage, current detector for detecting output current of three-phase inverter, virtual exciter, virtual motor, power detector, virtual synchronous generator algorithm module, voltage positive and negative sequence separation module and PWM drive In the module, the DC voltage source voltage enters the three-phase inverter, which is converted to generate AC voltage, and the generated voltage is sent to the L filter, and then output to the grid-connected terminal after filtering. The system control method is as follows:
通过虚拟励磁机、虚拟电动机及功率检测器计算出实时有功功率和无功功率，送入虚拟同步发电机算法模块，通过计算转换实时有功功率得到虚拟同步发电机的机械转矩，机械转矩与转动惯量通过数学关系计算出电网的同步角速度和同步发电机的机械角速度；实时无功功率通过计算得到参考电压；The real-time active power and reactive power are calculated through the virtual exciter, virtual motor and power detector, and sent to the algorithm module of the virtual synchronous generator. The mechanical torque of the virtual synchronous generator is obtained by calculating and converting the real-time active power. The mechanical torque and The moment of inertia calculates the synchronous angular velocity of the power grid and the mechanical angular velocity of the synchronous generator through mathematical relationships; the real-time reactive power is calculated to obtain the reference voltage;
L滤波器后的电压检测信号ua,ub,uc送入电压正负序分离模块，通过正负序分离分离结构，将电压ua,ub,uc分成正序电压分量up和负序电压分量un，再分别对正负序电压分量进行处理；The voltage detection signals ua , ub , uc after the L filter are sent to the voltage positive and negative sequence separation module, and the voltage ua , ub ,uc is divided into positive sequence voltage components up through the positive and negative sequence separationstructure and the negative sequence voltage component un , and then process the positive and negative sequence voltage components respectively;
正序分量处理：将两相旋转坐标系下的电压正序分量与参考电压做差，所得的值经过PI处理之后作为参考电流与三相逆变器输出的实时电流的正序分量ip进行比较处理；Positive sequence component processing: The voltage positive sequence component under the two-phase rotating coordinate system is compared with the reference voltage, and the obtained value is processed by PI as the reference current and the positive sequence componentip of the real-time current output by the three-phase inverter. comparison processing;
负序分量处理：将两相旋转坐标系下的电压负序分量与参数零做差，所得的值经过PI处理之后得到参考电流与三相逆变器输出的实时电流的负序分量in进行比较处理；Negative sequence component processing: the negative sequence component of the voltage in the two-phase rotating coordinate system is different from the parameter zero, and the obtained value is processed by PI to obtain the negative sequence component in of the reference current and the real-time current output by the three-phase inverter to compare;
正负序电压分量处理得到的结果再由两相坐标系转换到三相坐标系，转换后输出信号再送入SPWM模块中，由SPWM模块输出开关驱动信号，该信号经过驱动电路后控制逆变器开关的接通与关断，从而控制并网逆变器系统。The result obtained by processing the positive and negative sequence voltage components is converted from the two-phase coordinate system to the three-phase coordinate system. After conversion, the output signal is sent to the SPWM module, and the SPWM module outputs the switch drive signal, which controls the inverter after passing through the drive circuit. The switch is turned on and off to control the grid-connected inverter system.
本发明的有益效果在于：本发明基于虚拟同步发电机的不平衡电压控制方法，与现有的离网不平衡电压控制方法相比，本发明采用电压正负序分离的方法解决电网不平衡状态下不平衡电压的控制，能够使不平衡电压得到有效的抑制，从而使电网恢复平衡；本发明提出控制方法，拥有控制精度高，响应速度快等优点，可推广到其它单相或者三相并网逆变器的控制方法当中。The beneficial effect of the present invention is that: the present invention is based on the unbalanced voltage control method of the virtual synchronous generator. Compared with the existing off-grid unbalanced voltage control method, the present invention adopts the method of separating positive and negative voltage sequences to solve the unbalanced state of the power grid The control of the unbalanced voltage can effectively suppress the unbalanced voltage, so that the power grid can be restored to balance; the control method proposed by the invention has the advantages of high control precision and fast response speed, and can be extended to other single-phase or three-phase parallel In the control method of the grid inverter.
附图说明Description of drawings
图1为本发明基于虚拟同步发电机三相并网逆变器不平衡电压控制方法的整体结构框图；Fig. 1 is the overall structural block diagram based on the unbalanced voltage control method of the virtual synchronous generator three-phase grid-connected inverter of the present invention;
图2为本发明负序电压控制策略框图；Fig. 2 is a block diagram of negative sequence voltage control strategy of the present invention;
图3为本发明平衡电压控制仿真图。Fig. 3 is a simulation diagram of balanced voltage control in the present invention.
具体实施方式Detailed ways
如图1为本发明提出的一种在离网状态下，基于虚拟同步发电机三相并网逆变器不平衡电压控制方法的整体结构框图，系统主要包括直流电压源U、三相逆变器、L滤波器、检测L滤波器输出端电压的电压检测器、检测三相逆变器输出电流的电流检测器、虚拟励磁机、虚拟电动机、功率检测器、虚拟同步发电机算法模块、电压正负序分离模块及PWM驱动模块。直流电压源提供700V的电压，进入三相逆变器，经过转换产生交流电压，产生的电压送入L滤波器，滤波后输出并网端。通过虚拟励磁机、虚拟电动机及功率检测器计算出实时有功功率和无功功率，送入虚拟同步发电机算法模块，通过计算转换实时有功功率得到虚拟同步发电机的机械转矩，机械转矩与转动惯量通过数学关系计算出电网的同步角速度和同步发电机的机械角速度(也就是电气角速度)；实时无功功率通过相关计算得到参考电压。然后，L滤波器后的电压检测信号ua,ub,uc送入电压正负序分离模块，通过正负序分离分离结构，将电压ua,ub,uc分成正序电压分量up和负序电压分量un，再分别对正负序电压分量进行处理；将两相旋转坐标系下的电压正序分量与参考电压做差，所得的值经过PI处理之后作为参考电流与三相逆变器输出的实时电流的正序分量ip比较处理；再对负序分量进行处理，与正序分量相似，但实验目的为控制电压的负序分量为零，因此，负序分量与参数零做差，所得的值经过PI处理之后得到参考电流与三相逆变器输出的实时电流的负序分量in进行比较处理；得到的结果再由两相坐标系到三相坐标系转换。最后转换后输出信号再送入SPWM模块中，由SPWM模块输出开关驱动信号，该信号经过驱动电路后控制逆变器开关的接通与关断，从而控制并网逆变器系统。Figure 1 is a block diagram of the overall structure of an unbalanced voltage control method based on a three-phase grid-connected inverter based on a virtual synchronous generator in an off-grid state proposed by the present invention. The system mainly includes a DC voltage source U, a three-phase inverter Detector, L filter, voltage detector for detecting output voltage of L filter, current detector for detecting output current of three-phase inverter, virtual exciter, virtual motor, power detector, virtual synchronous generator algorithm module, voltage Positive and negative sequence separation module and PWM drive module. The DC voltage source provides a voltage of 700V, enters the three-phase inverter, and generates AC voltage after conversion. The generated voltage is sent to the L filter, and then output to the grid-connected terminal after filtering. The real-time active power and reactive power are calculated through the virtual exciter, virtual motor and power detector, and sent to the algorithm module of the virtual synchronous generator. The mechanical torque of the virtual synchronous generator is obtained by calculating and converting the real-time active power. The mechanical torque and The moment of inertia calculates the synchronous angular velocity of the power grid and the mechanical angular velocity (that is, the electrical angular velocity) of the synchronous generator through mathematical relationships; the real-time reactive power obtains the reference voltage through related calculations. Then, the voltage detection signals ua , ub ,uc after the L filter are sent to the voltage positive and negative sequence separation module, and the voltage ua ,ub ,uc is divided into positive sequence voltage components through the positive and negative sequence separation structure up and the negative sequence voltage component un , and then process the positive and negative sequence voltage components respectively; the voltage positive sequence component in the two-phase rotating coordinate system is compared with the reference voltage, and the obtained value is used as the reference current and the reference voltage after PI processing The positive sequence component ip of the real-time current output by the three-phase inverter is compared and processed; then the negative sequence component is processed, which is similar to the positive sequence component, but the purpose of the experiment is to control the negative sequence component of the voltage to be zero, so the negative sequence component Make a difference with the parameter zero, and the obtained value is processed by PI to obtain the reference current and the negative sequence component in of the real-time current output by the three-phase inverter for comparison; the obtained result is then converted from the two-phase coordinate system to the three-phase coordinate system system conversion. Finally, the converted output signal is sent to the SPWM module, and the SPWM module outputs the switch drive signal, which controls the on and off of the inverter switch after passing through the drive circuit, thereby controlling the grid-connected inverter system.
为说明本发明的正确性和可行性，对一台L型三相并网逆变器系统进行仿真验证。仿真参数为：直流电压源电压700V，电网电压有效值220V，SPWM的开关频率为15KHz，L型滤波器参数为L1＝10mH。In order to illustrate the correctness and feasibility of the present invention, an L-type three-phase grid-connected inverter system is simulated and verified. The simulation parameters are: DC voltage source voltage 700V, grid voltage effective value 220V, SPWM switching frequency 15KHz, L-type filter parameter L1=10mH.
虚拟同步发电机将有功、无功功率转化为虚拟同步发电机的电势电压向量为The virtual synchronous generator converts active and reactive power into the potential voltage vector of the virtual synchronous generator as
其中θ＝∫ωdt(ω为同步发电机的机械角速度)为虚拟同步发电机的相位。可实现在三相电网电压平衡时向电网注入恒定的功率，并可为电网提供惯性和阻尼支持。Where θ=∫ωdt (ω is the mechanical angular velocity of the synchronous generator) is the phase of the virtual synchronous generator. It can inject constant power into the grid when the voltage of the three-phase grid is balanced, and can provide inertia and damping support for the grid.
电动势U可分解为正序分量、负序分量和零序分量，且采用无中线连接的三相桥式逆变器，因此不考虑零序电动势的影响The electromotive force U can be decomposed into positive-sequence components, negative-sequence components and zero-sequence components, and a three-phase bridge inverter without neutral line connection is used, so the influence of zero-sequence electromotive force is not considered
其中UP、UN分别为正负序分量的峰值，αuP、αuN分别为正负序电动势的初相角。Where UP ,UN are the peak values of the positive and negative sequence components, and αuP , αuN are the initial phase angles of the positive and negative sequence electromotive forces, respectively.
两相旋转坐标系下三相不平衡时逆变器输出瞬时功率为：The instantaneous output power of the inverter when the three phases are unbalanced in the two-phase rotating coordinate system is:
式中p0、p1、p2分别表示有功功率的平均值、余弦谐波峰值和正弦谐波峰值，q0、q1、q2分别表示无功功率的平均值、余弦谐波峰值和正弦谐波峰值；d相旋转坐标系下有功电压和电流为q相旋转坐标系下有功电压和电流为d相旋转坐标系下无功电压和电流为q相旋转坐标系下无功电压和电流为因此，只要处理掉负序电压分量，功率平衡也能解决。In the formula, p0 , p1 , p2 represent the average value of active power, cosine harmonic peak value and sine harmonic peak value respectively, q0 , q1 , q2 represent the average value of reactive power, cosine harmonic peak value and Sine harmonic peak value; the active voltage and current in the d-phase rotating coordinate system are The active voltage and current in the q-phase rotating coordinate system are The reactive voltage and current in the d-phase rotating coordinate system are The reactive voltage and current in the q-phase rotating coordinate system are Therefore, as long as the negative sequence voltage component is dealt with, the power balance can also be solved.
因此，在不平衡电网电压下，平衡电压的控制方案如图2。Therefore, under unbalanced grid voltage, the control scheme of balanced voltage is shown in Figure 2.
图3为采用抑制电压负序分量策略后得到的平衡电压控制波形。从图中可以看出，在电网电压三相不平衡时，逆变器输出的电压仍保持三相对称。其负序分量得到抑制。从而可以得出，加入负序电压控制之后，VSG可以输出平衡的三相电压。Figure 3 shows the balanced voltage control waveform obtained after the strategy of suppressing the negative sequence component of the voltage is adopted. It can be seen from the figure that when the three-phase grid voltage is unbalanced, the output voltage of the inverter still maintains three-phase symmetry. Its negative sequence components are suppressed. It can be concluded that, after adding negative sequence voltage control, VSG can output balanced three-phase voltage.
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| CN201710447554.XACN107171346B (en) | 2017-06-14 | 2017-06-14 | Unbalance voltage control method based on virtual synchronous generator |
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| CN201710447554.XACN107171346B (en) | 2017-06-14 | 2017-06-14 | Unbalance voltage control method based on virtual synchronous generator |
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