Cascaded switching power converter for coupling a photovoltaic energy source to power mains

摘要

A cascaded switching power converter for coupling a photovoltaic (PV) energy source to power mains provides a high-efficiency and a potentially simple control mechanism for AC solar energy conversion systems. The PV energy source charges a capacitive storage element through a DC-DC converter, and an inverter couples energy from the capacitive storage element to the mains supply. The DC-DC converter is controlled so that ripple present on the capacitive storage element due to current drawn by the inverter is not reflected at the input of the DC-DC converter, which is accomplished by varying the conversion ratio of the DC-DC converter with the ripple voltage present across the capacitor. The average voltage of the capacitor can also be increased with increases in the available power output from the PV energy source, so that a corresponding increase in power is transferred to the mains supply.

主权项

1. A power converter for providing an AC power output from a photovoltaic power source, the power converter comprising:
a capacitive storage element; an inverter circuit having an input coupled to the capacitive storage element and an output providing the AC power output at a line frequency, wherein the inverter circuit draws charge from the capacitive storage element cyclically at half-periods of the line frequency and thereby causes a ripple variation in a voltage across the capacitive storage element; and a DC-DC converter having an input coupled to an output of the photovoltaic power source, and an output coupled across the capacitive storage element, wherein a conversion ratio of the DC-DC converter is varied by controlling a switching circuit of the DC-DC converter such that the output of the photovoltaic power source is maintained at a substantially constant voltage, and wherein the conversion ratio of the DC-DC converter varies at the half-periods of the line frequency as the output of the DC-DC converter follows the ripple variation in the voltage across the capacitive storage element.