电力工程技术 (May 2024)
Integrated optimization of loss distribution and capacitor voltage ripple for MMC devices
Abstract
Under inverter operating conditions, significant loss is incurred by the insulated gate bipolar transistor (IGBT) (referred to as T2 tube) in the lower part of the half-bridge submodule. The reduction of loss is beneficial for the improvement of equipment operation reliability. At the same time, the suppression of capacitor ripple voltage has the advantage for reducing capacitor demand and enhancing power density. However, attention is not given by existing optimization control strategies to the contradiction between loss distribution optimization and capacitor ripple voltage, making it difficult to balance equipment operation reliability and power density. Therefore, a comprehensive optimization method that combines the reduction of T2 transistor losses and the suppression of capacitor voltage ripple is proposed in this article. Firstly, the inherent contradiction between reducing the on-state loss of the T2 transistor and suppressing capacitor voltage ripple is explained by analyzing the impact path of charge on device loss and capacitor ripple voltage. Then, by introducing a penalty function, a comprehensive objective function is established that takes into account T2 transistor losses and capacitor voltage ripple. Subsequently, using the active bypass strategy as an example, a comprehensive optimization method based on the injection of second harmonic current and third harmonic voltage is proposed by analyzing the impact of the second harmonic current and third harmonic voltage injection on T2 transistor loss and capacitor voltage ripple. Finally, a simulation model is built in MATLAB/Simulink and PLECS for verification. The simulation results suggest that the reliability and power density of the device increase by the comprehensive optimization method, considering both T2 transistor losses and capacitor voltage ripple.
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