Synthesis of Large-Capacity Three-Phase Voltage Inverters with Pulse-Amplitude Modulation of the Output Voltage
The problem of designing large-capacity voltage inverters (up to a few MVA) involves the need to settle matters concerned with electromagnetic compatibility, including the interference radiation problem. Such electronic devices are required, e.g., for small-scale power-generating installations that use wind, water, and solar energy. One promising line of solving such problems implies synthesizing electronic devices based on using the multichannel conversion (MCC) principle. The structure of a combined three-phase voltage inverter (TVI) with MCC (TVI-C-MxL) is considered, which has the following distinctive features. (1) It offers the possibility of inverting an increased power level while using the available semiconductor devices with limited power and frequency ratings. (2) The considered structure makes it possible to use the minimum possible conversion frequency (equal to as low as twice the TVI-C-MxL output voltage frequency) owing to the use of an energy-saving voltage control algorithm in the channels. (3) The considered structure implies a low output voltage quantization level, which is achieved by shaping the voltage using by means of pulse-amplitude modulation (PAM) instead of PWM. The use of PAM helps improve the efficiency and electromagnetic compatibility, in particular, due to a reduced interference radiation level. A method for selectively suppressing the higher harmonic components with frequencies closest to that of the fundamental harmonic component is proposed, which makes it possible to improve the output filter’s overall mass and dimension indicators. The article presents a model description of the voltage with PAM with selectively suppressed higher harmonic components, which can be used for designing the output filter. The advisable application field of a TVI-C-MxL is for stationary electric power generating systems for small-scale power installations (wind and hydro power installations, and solar power plants).