基于DSOGI-PLL的VSG双机并联系统功率分配控制策略

Power Distribution Control Strategy for VSG Dual-machine Parallel System Based on DSOGI-PLL

针对多虚拟同步发电机VSG(virtual synchronous generator)并联运行条件下受扰容易引发功率振荡和频率稳定性降低的问题,提出了一种双二阶广义积分器锁相环DSOGI-PLL(dual-second order generalized integrator phase-locked loop)技术的改进型VSG控制策略。分析了不同工况下VSG双机并联系统对公共耦合点负载增量的分配情况,分析了关键参数对各机组供电容量分配的影响。通过在功频控制器中引入积分环节来实现电力系统频率的二次调节,并采用DSOGI-PLL技术减少VSG输出电能在基频处的扰动,从而抑制多VSG并联运行时受扰的功率振荡程度。仿真结果表明,相比于传统控制策略,该方案能有效减少VSG输出电能在基频附近的扰动,减小了功率振荡,提高了并联运行条件下的输出电能质量,实现了各机组之间能量的合理分配,验证了所提控制策略在并离网模式下的适用性。

Aimed at the problem that power oscillations are easily caused by disturbances and the frequency stability is reduced under the parallel operation condition of multiple virtual synchronous generator(VSGs),a modified VSG control strategy combined with the dual-second order generalized integrator phase-locked loop(DSOGI-PLL)technology is proposed in this paper.The distribution of load increment at the point of common coupling in the VSG dual-machine parallel system under different operation conditions is analyzed,and the influences of key parameters on the power supply capacity distribution of each unit are analyzed.The secondary regulation of the power system frequency is realized by introducing an integral link into the power frequency controller,and the DSOGI-PLL technology is adopted to reduce the disturbance of output power from the VSG at the fundamental frequency,so that the level of power oscillation caused by disturbances during the parallel operation of multiple VSGs is suppressed.Simulation results show that compared with the traditional control strategy,the proposed scheme can effectively reduce the disturbance of output power from the VSG in the vicinity of the fundamental frequency,reduce power oscillations,improve the output power quality under the parallel operation condition,and realize a reasonable distribution of energy among units,which verifies the applicability of the proposed control strategy in both the and off-grid modes.