DFIG风电机组网侧变换器的复开关表直接功率控制

传统直接功率控制(DPC)所用开关表的输出控制矢量离散且固定,导致脉宽调制变换器的交流输入电流富含谐波,在交流输入电压波动和不对称的情况下更为明显,无法满足基于双馈异步发电机(DFIG)的变速恒频风电机组在故障下的不间断运行要求.在分析网侧变换器数学模型和DPC原理的基础上,提出了一种基于复开关表的DPC新策略.该策略可根据变换器的交流输入电压、瞬时功率等工作状态,提供细化的开关表以供选择,从而在保留传统DPC结构简单特点的同时,获得了高精度的控制效果.仿真和实验结果表明,该控制策略在电网发生对称性过电压、电压跌落和不对称性故障时,均能保持三相输入电流的平衡、稳定,用于DFIG风电机组交流励磁变频电源的控制中能提高电网故障下风电系统的穿越运行能力,并减少脉宽调制变换器产生的电力谐波污染.

Multi-switching Table Based Direct Power Control for the Grid-side Converter of Doubly Fed Induction Generator Wind Turbines

The output voltage vectors generated by conventional DPC switching table are usually discrete and fixed and contain significant amounts of harmonic components in the three-phase input currents of the grid-connected pulse width modulation(PWM) converter.It is even more serious if the input AC voltage is fluctuating and/or asymmetry.As a result,it is difficult for the Doubly Fed Induction Generator(DFIG) wind turbines uninterrupted operation under the main system fault situations..Based on the grid-side converter model and the principle of DPC,this paper proposes a novel DPC strategy using multi-switching table method.The strategy is capable of providing detailed switching tables according to the converter working conditions such as line voltage,instantaneous power and etc.,while still retaining the simple structure of DPC.Therefore a high precision control is achievable.Simulation results demonstrate that the strategy can effectively maintain the symmetry and stability of the three-phase input currents under the grid voltage sagging,swelling and unbalanced fault conditions.Therefore,the MST-DPC scheme is an effective control strategy for the grid-side converter of DFIG under unbalanced grid voltage condition,with enhanced fault-ride-through capability and reduced harmonic pollutions to the grid.