电网不平衡下虚拟同步发电机功率-电流协调控制策略

虚拟同步发电机(Virtual Synchronous Generator, VSG)技术通过模拟同步发电机运行机理,在理想电网条件下能够使分布式电源友好接入电网。然而,在不平衡电网电压下,则会出现输出功率振荡、电流不平衡等问题。为克服这些问题,提出了一种基于静止坐标系下虚拟同步发电机功率-电流协调控制策略。该控制策略根据瞬时功率理论计算负序电流参考值,建立了恒定有功、无功及电流平衡3个控制目标的统一解析表达式,实现功率-电流的协调控制,提高了系统运行性能。最后仿真结果验证了所提控制策略的有效性。

Coordinate control of power and current for virtual synchronous generator under unbalanced grid voltage

The technology of virtual synchronous generator can simulate the operation mechanism of the synchronous generator, which can make distributed generation friendly connect to power grid under balanced condition. However, when the grid voltage becomes unbalanced, it will lead to rippled power and unbalanced three-phase current. To overcome this difficulty, a coordinate control of power and current for virtual synchronous generator based on the stationary frame is proposed. The instantaneous power theory is employed to compute the reference negative-sequence current command, which suppresses the active-power oscillation, reactive-power oscillation and balanced current respectively. The unified analytic formula of the control target is established to achieve the coordinate control of power and current, which enhances the operation performance of the system. Finally, the simulation results verify the effectiveness of the proposed control strategy. This work is supported by National Natural Science Foundation of China (No. 61703144 and No. U1804143) and Key Science and Technology Project of Colleges and Universities of Henan Education Department (No. 17A470010 and No. 18A470003)