大型可变速抽水蓄能机组SFC起动性能分析

SFC Starting Performance Analysis of Large Variable Speed Pumped Storage Unit

大型可变速抽水蓄能机组在抽水工况下作为电动机运行,在起动过程中需要克服发电电动机和水泵水轮机的阻力矩,并且需要在一定的时间内将机组拖动到并网转速,所以采用有效的起动方式至关重要。大型可变速抽蓄机组电动工况起动方式包括静止变频器(SFC)起动、背靠背起动和自起动三种,其中SFC起动为抽蓄电站普遍采用的起动方式之一。变速机组也可采用定速机组配置的SFC进行起动,但变速发电电动机为绕线式异步电机,采用三相交流励磁技术,与定速机组在机型和励磁技术等方面完全不同,且目前国内外针对变速发电电动机SFC起动的相关研究成果较少,故亟需开展变速发电电动机、SFC装置和交流励磁配合的研究分析。自起动方式受到电机参数和变流器输出等限制,输出力矩的能力较小,而背靠背起动方式常作为备用起动方式,两者均不适用于400MW级及以上大型可变速抽蓄机组的起动。本文从分析可变速发电电动机SFC起动的原理入手,搭建了可变速发电电动机SFC起动的数值仿真模型,利用该仿真模型对一台440MW的抽蓄机组起动全过程进行了仿真分析,获得了主要物理量的变化规律,验证了数值模型的可靠性。

Large variable-speed pumped storage units operate as electric motors under pumping conditions.During the start-up process,it is necessary to overcome the moments of resistance of the power generating motors and pump turbines,and it is necessary to drag the units to the grid-connected speed within a certain period of time.Therefore,it is crucial to adopt an effective starting method.Large variable-speed pumped storage unit electric starting methods include static frequency converter(SFC)starting,back-to-back starting and self-starting,of which SFC starting is one of the commonly adopted starting methods in pumped storage power stations,and variable-speed units can also be started with SFC configured for fixed-speed units.However,the variable-speed generating motor is a wound asynchronous motor with three-phase AC excitation technology,which is completely different from the fixed-speed unit in terms of model and excitation technology.At present,there are fewer research results related to the SFC starting for variable-speed generating motors at home and abroad,so there is an urgent need to carry out the research and analysis on the cooperation of variable-speed generating motors,SFC devices and AC excitation.The self-starting method is limited by the motor parameters and converter output,and the output torque capacity is small.The back-to-back starting method is often used as a backup starting method.So both of them are not applicable to the starting of large variable-speed pumped storage units of 400MW class and above.In this paper,starting from the analysis the principle of SFC starting of variable-speed generating motor,a numerical simulation model of SFC starting of variable-speed generating motor is constructed.The whole starting process of a 440MW pumped storage unit is carried out by using this simulation model,and the rule of change of the main physical quantities is obtained,which verifies the reliability of the numerical model.