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An analytical approach to the quality optimization of three-phase and two-phase pulse width modulation (PWM) in a three-phase bridge circuit is considered. To assess the quality of modulation, the mean square error of current modulation for the modulation period (local variance) and for the period of the modulating function (integral variance) is used. The free variables that can be used to optimize the three-phase PWM are the pulse offset parameters relative to the center of the modulation interval and the zero-sequence signal. The free variables that can be optimized for the two-PHASE PWM are the pulse offset parameters relative to the center of the modulation interval and the shift parameter of the passive phase switching function. The analysis of current dispersion for three-phase pulse width modulation and two-phase pulse width modulation is carried out. The switching functions of optimal three-phase and two-phase pulse-width modulation are synthesized according to the criterion of current dispersion in the load. With two-phase modulation, dynamic energy losses in the valves are reduced. It is shown that the use of two-phase modulation allows to raise the modulation frequency to the level at which the energy losses in the electronic keys are the same in the two-phase and three-phase modulation. In the case of equal energy losses in electronic keys, comparison of the optimal three-phase and two-phase modulation by the criterion of current dispersion in the load shows that at high modulation frequency and the amplitude modulation coefficient of more than 0,69, the use of twophase modulation is preferred. The analysis of the current dispersion generated by three-phase and two-phase PWM is performed. Switching functions of optimal three-phase and two-phase PWM are synthesized by the criterion of current dispersion in the load. It is shown that the optimization of the pulse displacement parameters relative to the center of the modulation interval is effective only at low modulation frequency. The efficiency of optimization of two-PHASE PWM by the parameter of shift of the passive phase switching function is small and does not exceed 7%. Two-phase modulation reduces dynamic energy losses in electronic keys. It is shown that the use of two-phase modulation allows to raise the modulation frequency to the level at which the energy losses in the keys are the same in the two-phase and three-phase PWM. Comparison of the optimal three-phase and two-phase PWM by the criterion of current dispersion in the load shows that at high modulation frequency and the amplitude modulation coefficient of more than 0.69, the use of two-phase modulation is preferred. The algorithm of combined optimal control of the frequency Converter using three-phase and two-phase modulation, the use of which leads to a significant reduction in the dispersion of currents at low modulation frequencies, is synthesized. A consequence of the reduced dispersion of current is the reduction of energy losses due to modulation and vibrating characteristics in rowing electric drives of large power.

vestnik gosudarstvennogo universiteta morskogo i rečnogo flota imeni admirala s. o. makarova/vestnik gosudarstvennogo universiteta morskogo i rečnogo flota imeni admirala s.o. makarova

COMBINED OPTIMAL PULSE WIDTH MODULATION ACCORDING TO THE CRITERION OF VARIANCE OF CURRENT IN PROPULSION ELECTRICAL INSTALLATIONS OF SHIPS