PWM Based Off Grid Solar Inverter

PWM, pulse width modulation, is a way to control the voltage output from the PV array. It is like a switch that turns on the PV output when the voltage to an input is too low and keeps the current on until the voltage across an input capacitor reaches a threshold. Then it turns off the current from the array until enough energy is used from the capacitor to allow the current to be switched back on to raise the voltage again. This will happen thousands of times a second. The problem with PWM is that it turns off the PV generation for the amount of time it takes for the load to drop the charge on the input capacitor. The time when the PV array available power is not being uses causes inefficiency. MPPT controllers use current to control the voltage. If the voltage is high enough, the current increases (drawing more power from the PV array and lowering the voltage). The MPPT process will draw the most energy possible from the PV array and can be 30% more efficient at energy production than PWM. When the battery is fully charged it restricts the PV output unless there is a grid connection that allows any energy not needed for charging the battery to be passed through an inverter to the grid. Both systems will protect a battery from over charging but MPPT will charge the battery faster, and produce maximum output to the grid.