| The regional power grids are connected through the DC transmission system, which is conducive to realize non-synchronous operation and isolation between the regional power grids and improve the dynamic quality and the stability of the regional power grids. When several AC systems are connected through the DC transmission lines, a number of DC transmission lines are required, which will greatly increase the investment and operating costs. Thus, Multi-terminal HVDC system appeared. This paper takes Quebec—New England±450 Three-terminal HVDC transmission project as an example to discuss control model, start-stop control, power reversal and tilt adjustment control of the Multi-terminal HVDC system.First, according to the Quebec power grid data, the Quebec±450 HVDC transmission system parameters are calculated. And system model, control system and AC system of a three-terminal 12-pulse bipolar±450 HVDC system are built in the simulation software PSCAD/EMTDC.Secondly, start-stop control module and power reversal control module are built in Quebec model. The paper analyzes the differences of start-stop control and power reversal between two-terminal and Multi-terminal system and proposes control method of all start, individual start, all stop, individual stop, all power reversal and individual power reversal. Then a feasible control method is given for the control mode changeover in the Multi-terminal HVDC system.Finally, the paper analyzes tilt adjustment control method, builds the control system and proposes feasible power adjustment control method.
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