(3) PWM converter
PWM converter controls the current to be supplied from the utility bidirectionally, and its magnitude should be adjusted according to the amount from the solar cell output power for fixed load At every operating instant the solar cell must be always operated at maximum power point by the step-up chopper
The PWM converter has the function of bidirectional power control, of which direction can be decided by the phase angle between the voltage and current at the utility side The utility supplies power to the load when the phase angle is zero, and the power flow reverses for the angle of 180
For given load power and utility voltage with constant magnitude, the instantaneous current to be controlled by PWM converter can be expressed as follows:
where