孤岛型微电网中逆变器并联运行控制策略

Control strategy for paralleled inverters in islanded micro-grid

为了解决基于传统下垂控制的逆变器并联系统无功分配不合理以及输出电压和频率存在偏差的问题,提出一种孤岛型微电网中基于虚拟阻抗的电压、频率和无功功率微调的逆变器并联控制策略。在传统下垂控制中加入虚拟阻抗使逆变器输出阻抗呈感性,消弱线路阻性成分引起功率耦合;对电压/频率进行二次调节,使电压和频率在负荷变化大时仍能维持在额定值,改善电能质量;二次无功调节直接控制无功功率的分配,使无功分配不再受逆变器端电压的影响,实现无功的高精度分配。建立微电网小信号动态模型用以分析系统稳定性及合理选择控制参数。仿真结果验证了所提控制策略的有效性。

In order to solve the problem that unreasonable reactive power sharing and deviations of output voltage and frequency based on the conventional droop control of paralleled inverters,a parallel inverter control strategy,based on virtual impedance,frequency / voltage and reactive power regulation,is proposed. Virtual impedance is added in conventional droop control to make the output impedances of inverters present inductive and weaken the power coupled caused by resistive component. Voltage / frequency secondary regulation improves the quality of voltage and frequency,and inverters can still maintain voltage and frequency rating even if large load power changes. Secondary reactive power regulation directly controls the distribution of reactive power and the reactive power sharing can be obtained independently from inverter output voltage,and achieve high precision of reactive power sharing. Small-signal dynamic model of microgrid is built to analyze stability and choose the control parameters reasonably. Simulation results verify the effectiveness of the proposed control strategy.