Kalman Filter Based Detection Scheme for DC-Link Voltage Measurement Faults in MMC-HVDC Systems

The dc-link voltage control technology is of great importance to the stable operation of the modular multilevel converter high voltage direct current (MMC-HVdc) system. Currently, most control methods need to acquire the actual dc-link voltage, which is obtained from the complicated dc voltage measuring device. The faults of the measuring device have occurred many times in recent years, causing the dc-link voltage controller failure and affecting the safety and stability of the system. This article analyzes the MMC discrete mathematical model and fault characteristics of the measuring device. Then, a dc-link voltage measurement fault detection scheme based on Kalman filter is proposed. The operating status of the dc voltage measuring device can be monitored in real time using the proposed scheme. To maintain the stable operation of the system during measurement faults, a backup indirect dc-link voltage control method is also discussed. The whole proposed scheme is robust to the system transient operation and can be easily integrated into existing control systems. When the fault occurs, it can continue maintaining dc-link voltage stability, until measurement devices return to normal or help shut down the converter smoothly, improving the reliability of MMC-HVdc systems. The feasibility and effectiveness of the proposed scheme are confirmed by simulation in MATLAB/Simulink and experiments in a three-phase MMC prototype.