The Research On Coordinated Control Strategy Of Wind Farm Connected Grid Via VSC-HVDC

With the increasingly exhausted non-renewable energy, wind energy is arenewable energy that get more and more the attention of people, but the largecapacity of wind power connected to the Internet still brings great impact to thesystem and power flow of fluctuations. The VSC-HVDC is anticipated as an attractivesolution to the large scale wind power transmission bottleneck. The strongcontrollability of VSC-HVDC can help the wind farm has a better networkperformance. This article mainly studied the wind through the VSC-HVDC networkfault crossing ability and multiterminal systems in the case of different operatingconditions on the coordination between the control technology of the VSC, Thefollowing is the specific research content.1. Based on the mathematic model of VSC-HVDC in abc three phases staticcoordinate system, the per-unit mathematical model and the equivalent circuitdiagram of VSC-HVDC in dq synchronous rotation coordinate system are established.The double-loops and direct-current control strategies of VSC-HVDC is studied， thecurrent inner loop controller based on the current state feed-forward and decouplingtheory is designed, and then the outer loop control strategy (e.g. constant DC voltagecontrol, active and reactive power control and frequency control).2. The fault ride through control strategy when the AC gide fault is disussied. ACgrid failure cause voltage drops, due to the power transmission ability reduction ofVSC-HVDC, the DC side of the power surplus produce DC overvoltage. The keypoint of fault ride through control strategy is to maintain the power balance of thesystem during the fault in the AC system. The fault ride through control strategybased on wind turbine inertia is proposed, improved the network performance of windfarms.3. Study the control strategy of VSC-MTDC system in the power balance, analysisof DC voltage master-slave control、DC voltage deviation control and DC voltagedroop control strategy principle, and analyses the advantages and disadvantages ofseveral control strategies, on the basis of this，, the article put forward a newcoordinated control strategy for the wind farm to the VSC-MTDC systeminterconnection problems, the Dc voltage deviation prolapse coordinated controlstrategy.Under the environment of Matlab/Simulink to set up a five end VSC-MTDCsystem applied in the simulation model of wind，verify the validity of the coordinated control strategy.