电网不对称故障下光伏逆变器预测控制方法

摘要

The control strategy for the photovoltaic inverter under unsymmetrical fault in power grid is focused on. A mathematical model of the grid-connection inverter when unsymmetrical fault occurs in the grid is built and an analysis of power characteristic is made.Then the photovoltaic inverter control strategy based on model prediction current is put forward. Simulation verifications and analysis of damping active power fluctuation and negative sequence component current are made on a PSCAD/EMTDC platform.The results show that the model prediction current control method is able to make the output current of the inverter quickly follow the reference current with good dynamic and static characteristics. Under the unsymmetrical fault in the grid,it effectively realizes the control of each sequence current without decomposing the grid current phase sequence,thus restraining active power fluctuation and negative sequence current caused by the unsymmetrical fault. Simple and easily processed digitally,this method is of great engineering value in photovoltaic inverter control. This work is supported by Fundamental Research Funds for the Central Universities(No.12MS33).%以光伏并网逆变器在电网不对称故障下的控制策略为研究对象，建立了并网逆变器在电网发生不对称故障时的数学模型，并对功率特性进行了分析，进而提出了电网不对称故障下基于模型预测电流控制的光伏并网逆变器控制策略，并在 PSCAD/EMTDC 平台上分别进行了以抑制有功功率波动为目标和抑制负序分量电流为目标的仿真实验。研究结果表明，模型预测电流控制方法能够使逆变器的输出电流迅速地跟随参考电流指令，具有良好的动稳态特性。在电网不对称故障下，不需要电网电流进行相序分解便可以实现对各序电流的有效控制，能够抑制三相电网电压不对称所引起的有功功率波动和负序电流，该方法控制算法简单，数字信号处理实现容易，在光伏逆变器的控制中具有工程价值。