MMC型光伏并网逆变器无差拍控制策略

Deadbeat Control Strategy of MMC Type Photovoltaic Grid Connected Inverter

将模块化多电平换流器(Modular Multilevel Converter,MMC)应用到光伏直流汇集并网系统中,可以提高光伏并网系统输出的电能质量,但是随着子模块数量的增多,MMC控制系统的计算量会显著增大。为简化MMC控制系统的计算量,通过分析研究,提出了一种基于无差拍电流控制的MMC的控制策略,该控制策略仅需一次坐标变换和PI调节环节,且可直接产生子模块投切个数,不需经过调制波调制,相对传统控制方法,运算量明显减少。最后利用MATLAB/Simulink搭建了光伏并网系统的仿真模型,仿真结果表明该控制策略具有很好的动态响应,可以使输出电流快速、准确跟踪参考电流,并网电流畸变率小,十分适宜并网系统的数字控制。

The application of the modular multilevel converter （MMC） to the collection of photovoltaic （PV） DC grid - connected system can improve the quality of the output power remarkably. However, with the increase of the number of sub modules, calculation amount of MMC control system will significantly increase. In order to simplify the calcula- tion of MMC control system, this paper proposes a control strategy for MMC based on the deadbeat current control which needs coordinate transform and P] regulation only once, and can directly produce switching number of the sub module without the modulation of modulation wave. Compared with the traditional control method, the computation a- mount is significantly reduced. Finally, a simulation model of the photovoltaie system is built through MATLAB/Simu- link. The simulation results show that the control strategy has a good dynamic response, and the output current can quickly and accurately track the reference current, and the grid current distortion rate is small. The above conclusion shows that the method proposed in this paper is very suitable for digital control of erid connected svstem.