Steady-state control and fault ride-through method of IPC-CSC for offshore wind integration

Abstract

The current source converters (CSCs) have the advantages of high power density and light weight, which are potential topologies for lightening offshore wind turbine converter platforms. The conventional phase-controlled CSC (CPC-CSC) effectively reduces the problems of PWM-CSC, which are high DC voltage fluctuation and high switching losses. However, it has only one degree of control freedom, which is not applicable to offshore wind power systems. On this basis, an improved phase-controlled CSC (IPC-CSC) is investigated to use in offshore wind power integration systems in this paper. After establishing the corresponding mathematical model, the principle of the modulation method is subsequently analyzed. Thereby, the factors affecting the voltage and frequency of the offshore AC systems are explored, and the steady-state control strategy is further proposed. A fault ride-through method utilizing the actively bypassed capability of the CSC is also proposed to suppress the overcurrent in the DC link, which is caused by a fault in the onshore grid. Moreover, the q-axis current injection method of wind turbine converter based on the offshore voltage amplitude deviation is proposed, which is advantageous to the stable operation of the offshore AC system during the fault period and the rapid recovery after the fault is cleared. Finally, typical operating conditions such as steady-state conditions, wind speed drops, and system faults are simulated in PSCAD, and the characteristics of offshore AC faults and DC faults are analyzed respectively to verify the feasibility of the raised schemes.