不平衡电压下利用降阶谐振控制器的新型VSG控制策略

针对虚拟同步发电机(VSG)在电网电压不平衡条件下逆变器输出电流存在严重畸变和有功、无功功率存在振荡等问题,利用比例积分降阶谐振(PI-ROR)控制器对传统不平衡电压下VSG控制策略进行改进。PI-ROR控制器不需进行电流、电压正负序分离计算就可实现对负序分量的无差控制,因而可将正序、负序电流放到同一dq轴上进行统一控制,与传统的正负序分别控制相比,不仅降低了电流环控制结构的复杂程度还避免了大量正负分离计算带来的控制延时。通过仿真证明PI-ROR控制器与恒有功、恒无功及电流平衡3种控制目标结合,可改善VSG在不平衡电压条件下的稳态、暂态性能。

VSG Control Strategy Under Unbalanced Voltage Improved by Reduced Order Resonant Controller

In view of the serious distortion of the output current of the inverter and the oscillation of the active and reactive power of the virtual synchronous generator (VSG) under the unbalanced power grid voltage, the proportion integral plus reduced order resonant (PI ROR) controller is used to improve the traditional VSG control strategy under the unbalanced voltage. PI ROR controller can realize the no difference control of negative sequence component without the separation calculation of positive and negative sequences of current and voltage, so it can put the positive sequence and negative sequence currents on the same dq axis for unified control. Compared with the traditional positive and negative sequences controller, it not only reduces the complexity of current loop control structure, but also avoids the control delay caused by a large number of positive and negative separation calculation. Finally, the simulation results show that the PI ROR controller can improve the steady and transient state performance of VSG under unbalanced voltage condition when cosidering the three control objectives of constant active power, constant reactive power and current balance.