基于自适应模式切换的虚拟同步发电机功率控制策略

The Active and Reactive Power Control of Virtual Synchronous Generator Based on Adaptive Mode Switching

传统无互联线储能变流器"功率-电压-电流"三环虚拟同步发电机(VSG)控制策略在微网中受到广泛关注,但往往会引起其输出功率限额的问题,分析两种现有解决方案:(1)利用改进下垂动态改变下垂系数的方法,其调节能力有限,功率限制效果不佳;(2)利用下垂额定点调节环平移下垂特性曲线的方法能限制功率输出,但调节环的切换可能引起VSG输出功率出现较大波动,易导致系统不稳定。为此,提出一种基于自适应模式切换的VSG功率控制策略,即PQ控制的电流源模式和VSG控制的电压源模式的相位和电流指令都实时跟踪,为PQ-VSG控制模式间的自适应切换奠定基础。最后,建立微网系统的仿真模型和实验平台,仿真和实验结果验证了所提控制策略的有效性。

The control strategy of conventional energy storage converter wireless virtual synchronous generator （VSG） control based on “power-voltage-current” closed loop is widely used. But the micorgrid voltage would significantly affect the active and reactive output power limits in this strategy. This paper analyzes the effectiveness of two existing solutions. One is the improved droop control method by dynamically adjusting the droop coefficients, which has limited regulating range. The other is the translational droop curve control method. Although this method has an excellent performance, it may cause the output power of VSG to fluctuate and further lead the system to be unstable. The paper proposes an improved VSG control strategy based on adaptive mode switching. Herein, both the additional phase and current instructions are real-time tracked, to realize smooth transition between PQ control current-source mode and VSG control voltage-source mode. Finally, the simulation and experimental platforms are established. The results verify the effectiveness of the proposed strategy.