The stand-alone solar photovoltaic power system is composed of solar moudle arry, controller ,battery and the inverter.working principle in detail:solar moudle under irradiation of sun light of sunlight at day time can generate DC,one part of which can be distributed to DC load through the controller or transrormed into alternating current bye the inverter;The other part can be utilized to charge for batter;Whenthe sunlight is deficient ,the battery can be employed to supply power toDC load through DCcontrol system or to alternating current load through the inverter.