Flatness-based control strategy of modular multilevel matrix converter

Abstract

The M3C(Modular Multilevel Matrix Converter) can realize three-phase AC-AC transformation, and has the outstanding advantages of easy modularization, high reliability, low harmonic content, etc., which can be used in high-voltage and large-capacity variable-frequency speed control systems. Aiming at the shortcomings of traditional PI control, such as slow steady speed, easy overshoot and poor dynamic performance, etc., a nonlinear flatness-based control strategy suitable for M3C is derived based on the differential flatness theory, and the stability of the flatness-based control system is proved by Lyapunov method. The flatness-based control has the advantages of fast response, no overshoot, no static error tracking and high dynamic performance, etc., which can greatly improve the control effect of M3C input-side and output-side currents. Under conditions of the input-side frequency changes and output-side load changes, the flatness-based control strategy can maintain the extremely low system impact, and has good overall control effect. At last, the correctness and superiority of the proposed flatness-based control method are verified by MATLAB/Simulink simulation under different working conditions.Air conditioning load modeling and cluster control strategy considering electrical characteristicLIU　Zhiwei1, MIAO　Shihong1, YANG　Weichen1, ZHANG　Shixu1, LIANG　Zhifeng2, WANG　Peng3(1. Hubei Electric Power Security and High Efficiency Key Laboratory, State Key Laboratory of AdvancedElectromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China;2. State Grid Corporation of China, Beijing 100031, China;3. Electric Power Research Institute of State Grid Hubei Electric Power Co., Ltd., Wuhan 430077, China)In order to make full use of the regulating potential of the thermostatically controlled load, the air conditioning load is taken as an example to study the air conditioning load modeling and cluster control strategy. Firstly, a complete air conditioning load model is established from both the thermodynamic model and the electrical model. Secondly, considering the actual factors such as the number of start-stops and the service life of the air conditioner, a control strategy in the air conditioning cluster based on the improved temperature priority sequence is proposed. Finally, the influence of load voltage changes on the cluster res-ponse power is analyzed, and an air conditioning cluster control strategy considering power response deviation, voltage constraint and cluster equivalent state of charge is proposed based on frequency droop control. The simulative results based on MATLAB/Simulink show that the proposed air conditioning cluster control strategy can realize the suppression of power fluctuation of microgrid, at the same time it can effectively reduce the number of start-stops of the air conditioner and reduce the impact on the service life of the air conditioner.