A Coordinated Control Strategy for VSC-MTDC System Based on DC Voltage-Active Power Characteristic

A coordinated control strategy of voltage source converter based on multi-terminal direct current(VSC-MTDC)transmission system for integrating large-scale offshore wind power is proposed.With the typical five-terminal DC transmission system as an example,a coordinated control strategy based on local controller among converter stations is put forward,as is an improved descent control strategy for assistant converter station as well as an improved control strategy for active power control(APC)converter station,respectively based on DC voltage-active power characteristic,and the working modes of the two converter stations are analyzed.The parameter selection method of assistant and APC converter station is presented via DC power flow distribution and max/min operation mode.Simulations via PSCAD/EMTDC are conducted to validate the coordinated DC voltage control method under normal,master converter station fault and assistant converter station fault conditions,respectively.Results show that this method is able to guarantee the active power allocation of VSC-MTDC transmission system with good control effects.