新型并联逆变器功率均分与环流抑制策略

Power Sharing and Current⁃circulation Suppression Strategy of New Shunt Inverter

微网中各并联逆变器与公共交流母线之间的线路阻抗存在差异,使得逆变器的输出功率不能精确均分,从而导致系统环流的产生。为此,提出了一种在分频域中引入虚拟阻抗的方法。在基波频域中,使用二阶广义积分算法构造的感性虚拟阻抗使得等效线路阻抗在基波频域为感性特性;在谐波频域中,使用一种根据谐波电流有效值来实时调节的阻性虚拟阻抗使得等效线路阻抗在谐波频域呈现阻性特性,以达到降低系统谐波电流和系统环流的目的;在总频域中,使用虚拟负阻抗来抵消线路中阻性阻抗的影响,减少由线路阻抗引起的电压降落。仿真结果验证了分频域虚拟阻抗的引入减小了线路阻抗之间的差异,提高了功率均分的精度,降低了系统环流,实现了逆变器稳定运行。

The difference of line impedance between each parallel inverter and the public AC bus in the micro grid makes the output power ofinverter not be evenly shared,which leads to the generation of current-circulation in the system.For this reason,a method of introducing virtual impedance in the frequency division domain is proposed.In the fundamental frequency domain,the use of inductive virtual impedance,which is constructed by the second order generalized integral algorithm,makes the equivalent line impedance show inductive characteristic in the fundamental frequency domain.In the harmonic frequency domain,a kind of resistive virtual impedance,which is adjusted in real time in accordance with harmonic current RMS,is used to make the equivalent line impedance show resistive characteristic in the harmonic frequency domain so to reach the purpose of reducing harmonic current and circulation of system.In the total frequency domain,the virtual negative impedance is used to offset the effect of resistive impedance in the line and reduce voltage drop caused by the line impedance.The simulation results show that the introduction of virtual impedance in the frequency division domain reduces the difference between the line impedance,improves the precision of power sharing,reduces the system circulation and realizes stable operation of the inverter.