Refinement of the optimal switching frequency of a voltage-source inverter with a filter

Abstract

The article states the need to increase the switching frequency of autonomous voltage-source inverters in order to minimize its total mass together with the low-frequency output filter. The reduction in the mass of passive components of the filter with increasing inverter switching frequency is accompanied by an increase in the power losses in its transistors. Two mutually opposite directions form the minimum of the objective function of the dependence of the mass of the autonomous voltage inverter - filter system on the switching frequency. Previous works on finding the mass of the inverter - filter system when using thyristors, silicon transistors, transistors based on silicon carbide and gallium nitride, filters with a core made of electrical steel, amorphous iron, permalloy and ferrite are considered. It is justified to generalize previous studies by dividing the frequency range into five regions according to the core materials used. To construct the objective function of the mass dependence of the elements of the autonomous voltage-source inverter-filter system, the method of weight coefficients was used, which are specific mass indicators, respectively, for transistor coolers, choke, and filter capacitor. A diagram of a single-phase autonomous voltage inverter with a low-frequency filter is presented. The objective function of the mass dependence of the elements of the voltage inverter-filter system on the switching frequency is described. Using weight coefficients for chokes with different core materials, it is possible to carry out global optimization. The previously obtained indicators of the optimal frequency for silicon transistors and a choke with a core made of electrical steel are confirmed. It is shown that replacing the core material does not allow to significantly reduce the mass of the inverter-filter system. Using transistors based on silicon carbide and a choke core made of amorphous iron, it is possible to improve the mass and dimensions of the inverter with a filter by three times. The use of high-frequency materials such as permalloy, powdered iron, and ferrites in the core of the choke does not provide a weight advantage, nor does the use of faster gallium nitride transistors. For most industrial inverters, the optimal frequency is 3.2 kHz.