NOVELTY - The system (1) has a photovoltaic power generator (10) for outputting an electrical power generated by using solar light. An inverter (30) converts the generated electrical power into an alternating current (AC) power and supplies the AC power to a commercial power source (50) or to a load (60). A capacitor (40) stores the generated electrical power. A monitor (20) directs the generated electrical power to the inverter or the capacitor based on an operation mode selected by a user. The operation mode is selected from one of a load driving mode, a power sale mode and a charging mode.    USE - Photovoltaic power generation system e.g. stand-alone photovoltaic power generation system and grid-connection photovoltaic power generation system.    ADVANTAGE - The system has the inverter converting the generated electrical power into the alternating current (AC) power in response to a driving control signal output from a controller and supplying the AC power to the load, thus reducing cost of electricity since the load can be driven using the generated electrical power instead of the commercial power source. The user can use the generated electrical power for driving the load and sell the generated electrical power by using the system, thus providing economical benefits to the user and reducing loss of the electrical power generated in real-time, and hence improving efficiency of the generated electrical power. The monitor has an operation mode selection receiver attached to a display so as to allow the user to drive the system in a user's desired operation mode such that the generated electrical power meet user's requirement, thus improving user convenience and user satisfaction.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for controlling a photovoltaic power generation system.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of a photovoltaic power generation system.    Photovoltaic power generation system (1)    Photovoltaic power generator (10)    Monitor (20)    Inverter (30)    Capacitor (40)    Commercial power source (50)    Load (60)