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基于模块化多电平高压直流输电系统(high voltage direct current transmission based on modular multilevelconverter,MMC-HVDC)通常采用双闭环矢量控制策略,由于该策略在不平衡故障情况下,需要采用正负序2套旋转坐标系对正负序电流分别进行控制,从而存在需要调整控制参数多、动态响应慢的问题。该文在两相静止坐标系下,分析了MMC-HVDC数学模型的特点,并对其功率分量进行了相应推导。为了实现交流信号无静差控制,在坐标系下引入比例谐振控制器实现正负序电流的统一控制,该策略无需繁琐的旋转坐标变换,从而不存在受电路参数影响的耦合项和前馈补偿项,进而方便了控制器的设计;同时利用PR控制器对传统电容电压均衡控制内环进行了改进,最后,在PSCAD/EMTDC中搭建的仿真模型基础上,验证了-PR平衡和不平衡控制策略的有效性。
Double closed-loop vector control strategy is usually adopted in the MMC-HVDC based high-voltage direct current transmission based on modular multilevel converter (MMC-HVDC). Because of the unbalanced fault condition, this strategy needs two sets of positive and negative sequence The rotating coordinate system separately controls the positive and negative sequence currents, so there is a problem that many control parameters need to be adjusted and the dynamic response is slow. In the two-phase stationary coordinate system, the characteristics of the MMC-HVDC mathematical model are analyzed and its power components are deduced accordingly. In order to realize no static difference control of AC signals, a proportional resonance controller is introduced into the coordinate system to achieve unified control of positive and negative sequence currents. This strategy does not require cumbersome rotation coordinate transformation, so there is no coupling term and feed forward compensation affected by the circuit parameters , And then the design of the controller is facilitated. At the same time, the PR capacitor is used to improve the traditional capacitor voltage balance control inner loop. Finally, based on the simulation model built in PSCAD / EMTDC, the control of -PR balance and unbalance control The effectiveness of the strategy.