并联型统一电能质量控制装置无缝切换控制技术

摘要

There are generally excessive harmonics,reactive power and negative sequence currents in the distribution power system,which can cause hazards including poor efficiency of power grid operation,unusual heating and damage of load.Meanwhile,a large number of sensitive loads,including communications,medical and high-end manufacturing,will run out of order as long as the duration of voltage interruption or voltage sags lasts more than a few milliseconds,which may cause serious economic losses.Therefore these power quality issues need to be integrated.The shunt-unified power quality controller (S-UPQC) can solve the above two types of power quality problems respectively and the key is to realize the fast and smooth seamless switching between the two operating states.In view of the problems in the existing switching control,this paper proposes a complete seamless switching control technique for S-UPQC,including the seamless cut-in algorithm based on current rate control and the flexible cut-off algorithm based on instantaneous linear modulation,with the advantages of simpleness,quickness and reliability.Its cut-in time is less than 1 ms and there is no mutation of voltage amplitude and phase in its cut-off process.The effectiveness of the proposed method is verified by PSCAD/EMTDC electromagnetic transient simulation and physical prototype experiment based on 380V/100kV·A S-UPQC.%配电网中普遍存在谐波、无功和负序潮流超标等电能质量问题,这会引起电网运行效率降低、负荷异常发热乃至损坏等;同时通讯、医疗及高端制造等大量敏感负荷一旦供电中断或电压暂降时间超过几ms,即可能运行失常并造成严重的经济损失,因此需要对这2类电能质量问题综合治理.并联型统一电能质量控制器(shunt-unified power quality controller,S-UPQC)能够分别解决上述2类电能质量问题,这在于S-UPQC可以在其2种运行状态之间实现快速平稳地无缝切换.针对现有切换控制中存在的不足,文章提出一种完整的无缝切换控制算法,包括基于电流变化率控制的无缝切入算法和基于瞬时值线性调制的柔性退出算法2部分.该算法具有实现简单,切换过程迅速可靠、平稳光滑的优点,其切入响应时间小于1 ms,退出过程电压无幅值和相位突变.基于380 V/100kV·A规格S-UPQC的PSCAD/EMTDC电磁暂态仿真和物理动模样机试验均验证了该方法的有效性.