Minimisation of Instantaneous Total Harmonic Distortion of Curents for Three-Phase Switching Power Converters
Günay, Murat (2002) Minimisation of Instantaneous Total Harmonic Distortion of Curents for Three-Phase Switching Power Converters. [Thesis]
This work studies an application of the discontinuous control approach to the design of the current control loop in switching power converters and electrical drives. The role of the current control loop is to generate the switching patterns that will determine the sequence and the duration ON and OFF states of the switches. The reduction of the Instantaneous Total Harmonic Distortion of the currents for 3~Phase Switching Power Converters and 3~Phase Electrical machines is being selected as additional requirement determining the switching matrix operation. The approach is based on the Direct Sliding Mode principle and the unified approach for control of a PWM 3-phase switching matrix with six switches, common for 3-phase inverters, rectifiers as well as 3-phase machines. Conventional tracking control algorithms may provide the proper selection of switching vector but not the proper timing since switching timing occurs only when the control error is contacted pre-set hysteresis bounds. However this generates significant harmonic distortion especially low order harmonic distortion compared with carrier based algorithms. The quality of the switching control algorithm is determined by both the proper selection of switching vector and the proper switching timing. The presented algorithm evaluates harmonic distortion in real time with instantaneous THD definition and sequentially selects two switching vectors in one control period in order to minimize the tracking error and timing is determined according to the THD minimization theorem. The simulation of the approach is performed on both Boost Rectifier and Buck Inverter, and comparative simulation results with Relay Control approach are given.
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