Flexible synchronous PWM control of cascaded inverters for photovoltaic generation

Development of the modulation strategy for synchronous control of cascaded inverters, supplied by two strings of photovoltaic panels and connected to a grid by a three-phase transformer with an open winding configuration on primary side, has been done in the paper. Algorithms of synchronized pulse width modulation (PWM) are based in this case on continuous control of switching frequencies of two inverters as function of magnitudes of the DC-links voltage. It allows providing both continuous voltage synchronization in each inverter and in the load, and also an improvement of effectiveness of operation of the systems under some operating conditions. Spectral assessment of quality of the phase voltage for the systems with basic versions of synchronized PWM has been performed.