基于虚拟同步发电机的离网型三相逆变器控制研究

Control Research on the Three-Phase Inverter Based on Virtual Synchronous Generator in Islanded Mode

针对传统三相逆变器控制,在借助虚拟同步发电机二阶暂态数学模型的基础上,利用电容电压和电容电流反馈,与虚拟同步发电机构成功率-电压-电流三环控制。其中,电容电压环采用比例积分控制,保证稳态无误差;并使控制系统具有下垂特性,以及同步发电机转子惯性的特性,提高频率的稳定性。在分析虚拟同步发电机原理的基础上,详细分析了电压电流双环控制参数的整定和等效输出阻抗的计算。利用小信号分析法,详细分析了转动惯量、有功系数和无功系数对系统稳定性的影响。最后由仿真结果表明所提策略的正确性和有效性。

According to the traditional control of three-phase inverter,basing on the transient mathematical model of second order of virtual synchronous generator, the three loops control of power-voltage-current with virtual synchronous generator（ VSG） by using the feedback of capacitance＇s voltage and current was built. And the proportional and integral control was applied in the loop of voltage to ensure zero steady-state error. In the meantime,the control system has droop characteristic and virtual inertia as synchronous generator rotors. So the stability of frequency could be improved. The theory of VSG was analyzed firstly,and then the analysis of parameters tuning of voltage-current control and calculation of equivalent output impedance were given. Then,the effects of moment of inertia,active power coefficient and reactive power coefficient on system stability were analyzed in detail by using small signal analysis method. In the end,the simulation results showed that the control strategy was feasible and effective.