Broyden quasi-Newton-based parameter measurement method for thyristor-level components in converter valves without wire disconnection

Abstract

To address the heavy workload of wire disconnection and reconnection, the measurement errors caused by external-circuit shunting, and the difficulty of obtaining specific component parameters using the comprehensive impedance method in field testing of damping and voltage-balancing components in HVDC converter valve thyristor levels, this paper proposes a parameter measurement method for thyristor-level components in converter valves without wire disconnection based on the Broyden quasi-Newton method. In the proposed method, two adjacent thyristor levels are selected as the measurement object, and the equivalent parameters of the external circuit are incorporated into the solving model. Parameter equations for the DC voltage-balancing resistors, damping resistors, and damping capacitors are established using DC and AC measurement data. The resulting nonlinear equations are then solved iteratively using the Broyden quasi-Newton method. MATLAB/Simulink simulation results show that the proposed method can accurately identify key thyristor-level component parameters while maintaining the intact wiring state of the converter valve. When compared with the direct measurement method that ignores the external circuit, the proposed method effectively reduces the influence of external-circuit shunting and provides higher measurement accuracy and better engineering applicability.