Power converters are used to convert power from direct current (DC) power sources to alternating current (AC) power output for use on local loads or for delivery to a power grid. Such power converters are instrumental in applications such as for providing AC power from DC distributed power sources like photovoltaic (PV) cells. With an increased societal focus on anthropogenic environmental degradation, particularly in relation to green house gas (GHG) and certain other emissions, there has been an increased trend towards distributed renewable power generation. For example, in recent years, there has been a steep increase in the number of homes and businesses that have installed roof top solar cell arrays that generate power to power a home or business and also provide excess power to the power grid. Such distributed power generation sources may require power converters that are relatively efficient, inexpensive, reliable, and have a minimal form factor. Conventional power converters typically comprise DC filters, boost converters, AC filters, inverters, and coupling to the power grid.
In distributed generation or point of use generation of power where a local load can receive power either from the distributed generation source or the power grid, the local load can become disconnected from the electric grid and the distributed generation source can continue to power the local load. This condition is referred to as islanding, where the local load and the distributed generation source has been “islanded” or electrically separated from the rest of the power grid.
Islanding a load can lead to a drift in the local frequency and phase between the voltage and current delivered to the local load. Additionally, islanded conditions may pose a hazard to utility workers that may be working on power lines and may not be aware of the existence of islanded and powered live power lines. Therefore, when an islanding condition exists, anti-islanding procedures are implemented to prevent the supply of power from the distributed power source to the local load. Furthermore, Underwriters Laboratory certification (UL1741) requires power converters to provide a mechanism for detecting an islanding condition and implement anti-islanding procedures.
USPTO Backgrounds
USPTO Backgrounds