不平衡电网电压条件下光储微电网并网控制

混合储能型光伏并网系统不仅有效解决了传统光伏发电的随机性和波动性,同时克服了单一储能系统功率密度与能量密度相矛盾的不足。但电网电压的不平衡则会使光储微网系统的输出电能质量下降,并且逆变器侧会出现过流现象,进而影响了整个系统的运行稳定性。为抑制储能变换器中电流及系统入网功率的二倍频脉动,提高并网电能质量,在两相静止坐标系下,分析了并网电流参考值的谐波与过流问题,提出带有功率补偿的限流模型预测直接功率控制;在混合储能系统控制结构中引入二倍频陷波器,并结合模型预测电流控制,实现了系统的快速动态响应以及高电能质量入网。在MATLAB/Simulink中搭建了系统仿真模型,并针对不同工况进行了仿真验证。仿真结果表明:在不平衡电网电压下,所提控制策略可平抑储能变换器中电流与逆变器中输出功率的二次脉动,同时在实现对有功、无功功率及负序电流协调控制时,可实现对故障过电流的抑制。

Grid-connected Control of Microgrid with Photovoltaic and Energy Storage Systems Under Unbalanced Grid Voltage Conditions

The photovoltaic(PV)grid-connected system with hybrid energy storage(HESS)not only effectively solves the randomness and fluctuation of traditional PV power generation,but also overcomes the contradiction between the power density and the energy density of a single energy storage system.However,the output power quality will be worse,and the overcurrent will appear on the inverter side under unbalanced grid voltage condition.This will affect the operation stability of the entire system.In order to restrain the doubling frequency pulsation of the current in the energy storage converter,and secondary pulsation in grid-connected power in order to improve the power quality;the harmonics and overcurrent problems of the grid current reference value are analyzed in the two-phase stationary coordinate system.The current-limited model predictive direct power control(MPDPC)with power compensation is proposed.The double frequency notch filter is introduced in HESS,combining with the model predictive current control,the fast-dynamic response of the system and the high-power quality are realized.The system simulation model has been built in MATLAB/Simulink and tested for different working conditions.Simulation results show that the proposed control strategy can stabilize the secondary ripple of the current in the energy storage converter,and the output power of the inverter.At the same time this can achieve the suppression of the fault overcurrent during the coordinated control of the active/reactive power,and the negative sequence current under imbalanced grid voltage.