基于有功和无功功率协调分配的统一电能质量调节器控制策略

摘要

统一电能质量调节器(UPQC)由串联型有源滤波器和并联型有源滤波器组合而成.在常规功率控制策略中,串、并联变流器与馈线之间存在的有功功率环流增大了串、并联单元的容量负担和损耗,且当电源电压跌落较大时,串、并联单元在补偿电能质量过程中有可能发生容量越限.提出了基于有功和无功功率协调分配的UPQC控制策略,通过合理分配串、并联变流器的功率输出,充分发挥串联变流器的作用,使得串联变流器承担部分负载无功功率以减轻并联变流器的负担,并消除有功功率环流;基于并联变流器补偿容量恒定的原则分配电源与储能单元提供的有功功率,以减小配电网馈线过电流的风险,并保证串、并联单元在补偿电能质量过程中不会发生容量越限.在电源电压完全跌落的极限情况下,负载有功完全由储能提供,实现了不间断电源的功能.在PSCAD/EMTDC中搭建了仿真算例,结果验证了所提策略的正确性和有效性,能够实现UPQC串、并联变流器以及储能单元的协调控制.%UPQC(Unified Power Quality Conditioner) is composed of series active power filter and shunt active power fiber.In the conventional power control strategy,the active power circular flow existing between feeders and series and shunt converters increases the capacitance burden and loss of series and shunt units,and a big voltage drop of power source may cause the overload of series and shunt units in the power quality compensating process.The control strategy of UPQC based on active and reactive power coordination distribution is proposed.The output power of series and shunt converters is reasonably allocated to make full use of series converter and make it take part of the reactive power of load to lighten the burden of shunt converter and eliminate the active power circulation.The active power of power source and energy storage unit is distributed based on the principle of constant compensation capacity of shunt converter to decrease the overcurrent risk of distribution network feeders and avoid capacity overload of series and shunt converters in the power quality compensating process.When the voltage of power source drops completely,the load active power is completely provided by the energy storage unit,realizing the function of uninterrupted power supply.Results of a simulation example built in PSCAD/EMTDC verify the validity and efficiency of the proposed control strategy and show that the proposed strategy can realize power coordination distribution among series and shunt converters of UPQC and energy storage unit.