基于功率匹配和自适应惯性的VSG预同步控制方法

Pre-synchronization Control Method for Virtual Synchronous Generator Based on Power Matching and Self-adaptive Inertia

虚拟同步发电机(VSG)从离网向并网模式切换时需要进行预同步控制。针对VSG预同步并网后的稳定性问题,提出一种基于功率匹配和自适应惯性的VSG预同步控制方法。所提方法将电网电压的幅值和频率作为VSG输出电压的参考值,然后根据本地负载功率调整其输出功率参考值,使VSG输出电压的频率和幅值与电网电压同步,最后采用相位偏差的反馈控制实现相位同步。所提方法使得VSG并网后稳态工作点对应的输出功率与并网前一致,避免了VSG并网后出现的功率跃变现象。考虑到VSG在非理想情况下并网后出现的功率振荡,引入自适应惯性实现同步过程的振荡抑制。基于MATLAB/Simulink构建了VSG预同步并网仿真模型,结果表明:所提方法可保持VSG并网前后稳态输出功率一致且非理想情况下并网后的振荡时间可减少约60%,验证了所提方法的有效性。

It was necessary for the virtual synchronous generator(VSG)to be synchronized with the grid when it switched from off grid mode to grid connected mode.In this study,a modified pre-synchronization control method based on power matching and self-adaptive inertia for the VSG was proposed to improve its stability after grid connection.The proposed method took the amplitude and frequency of grid voltage as the reference value for the VSG output voltage,and then adjusted its output power reference value according to the local load power,thus the voltage frequency and amplitude of the VSG could be regulated to be synchronized with the grid.Besides,feedback control of phase deviation with PI controller was applied in the frequency control loop to achieve phase synchronization.With this method,the output power corresponding to the steady-state operation point of the VSG in grid connected mode was consistent with that before grid connection,and the output power step after the VSG connected to the grid could be avoided.While,when the VSG connected to grid in non-ideal situation,power and frequency oscillations would occur in the synchronization process,so time-varying inertia was introduced in this study to accelerate the VSG to stable state.A simulation model was constructed based on MATLAB/Simulink and simulation results indicate that the proposed method can maintain the same steady-state output power before and after the VSG connected to grid,besides,oscillation time after the VSG connected to grid in non-ideal situation could be reduced by about 60%,which proved the proposed method effective.