Adaptive maximum power point tracker in photovoltaic grid-connected system

This paper proposed a non-active disturbance maximum power point tracking technology in photovoltaic grid connected inverter system. The maximum power point is reached by natural fluctuations of the photovoltaic array output power. The bus voltage value corresponding to the maximum power is got in voltage pulsation cycle, and that voltage will work as instruction voltage in the next cycle. Then the PV array voltage can automatically move to the maximum power point. When the operating voltage moves to the maximum power point, the extremun power will be located in the mid-point of the voltage pulse at that time. Therefore, the bus voltage will not be moved by the original control strategy. If the temperature or the intensity of sunlight changes, the shift of the maximum power point voltage will cause the bus voltage instruction automatically to move again. This method tracks the maximum power point quickly without setting any parameters. The validity of the proposed adaptive MPPT method is verified through a 10kW three-phase PV grid connected inverter applied in 8kW PV power plant in the field.