基于准PR控制的虚拟同步逆变器故障冲击电流快速抑制方法研究

Research of Inrush Current Restraining Strategy Based on Quasi-PR Control for Synchronverter During Grid Fault

传统的虚拟同步逆变器大多采用脱网运行来应对电网故障瞬时产生的大电流冲击,没有考虑到对逆变器本身及公共电网的危害。因此,研究一种适用于虚拟同步逆变器瞬时冲击电流的抑制方法极为重要。该文首先分析虚拟同步逆变器的基本特性,结果表明,由于逆变器输出基波电势不能突变,当电网故障瞬间势必在逆变器输出端口产生一个很大的冲击电流,严重威胁电力电子器件的安全可靠运行及公共电网的稳定性。基于此,提出一种抑制虚拟同步逆变器冲击电流的新方法,即在故障瞬间切换为准比例谐振控制,故障结束后平滑反切回虚拟同步控制。该方法在维持逆变器不脱网的前提下,既可以快速抑制瞬时冲击电流,又可以支持并网点电压。仿真与实验验证所提方法的正确性与有效性。

Most of the traditional synchronverters adopt off-grid operation to deal with instantaneous inrush current impact during grid failure, taking no. consideration of the potential hazards to inverter itself or to the public power grid. Therefore, it is very important to study a method of instantaneous inrush current suppression for synchronverter. Firstly, the basic characteristics of synchronverters were analyzed. The results show that there will be large inrush current at the synchronverter＇s output port when the grid faults happen due to the non-mutable fundamental voltage outputted by the inverter. This will take a great threat to the safe and reliable operation of power electronic devices and the stability of the public grid. Based on this, a new restraining strategy was proposed in this paper, in which the synchronverter switches to quasi-proportional resonant （Quasi-PR） control mode during grid fault and smoothly switches back to the virtual synchronous mode after the fault cleared. It can quickly suppress the instantaneous inrush current and support the restoration of grid voltage while maintaining the inverter operating on grid-connected mode. Simulation and experiment results verified the correctness and validity of the proposed method.