Communication-Free Coordination Control Strategy for LFAC Offshore Wind Power System Based on CSC

Low-frequency alternating current (LFAC) power transmission combines some advantages of both high-voltage alternating current (HVAC) transmission and high-voltage direct current (HVDC) transmission. It is a new type of transmission method in the context of offshore wind power delivery for medium and long distances. The actively commutated current source converter (CSC) is a new type of converter with promising engineering application prospects. It offers advantages such as compact size, high power density, no risk of commutation failure, and strong fault ride-through capability. Currently, the main modulation method for CSC is pulse width modulation (PWM), which increases the switching losses and device stress of the converter. To address this issue, this paper proposes a flexible lowfrequency offshore wind power transmission scheme using fundamental modulation for CSC. However, this approach cannot simultaneously control both the voltage amplitude and frequency. To achieve stable control of both voltage amplitude and frequency, existing DC transmission schemes rely heavily on extensive communication, which is costly and difficult to ensure reliability, significantly reducing the practicality of the solution. To address these problems, this paper proposes a coordination control strategy between the wind turbine and CSC without communication. It effectively controls the offshore AC voltage and frequency without relying on long-distance communication, significantly reducing engineering costs and improving operational reliability. Finally, a simulation model was built in PSCAD/EMTDC to analyze the system's response characteristics under typical operating conditions. The results verified the correctness and effectiveness of the proposed scheme and control strategy.