As more PV systems are added to the electrical grid, the requirements for interconnection are changing. New PV inverters are being required to provide advanced functions to help support the robust operation of the electrical system. These functions include:
- Volt-VAr (voltage regulation)
- Commanded Power Factor (voltage regulation)
- Frequency-watt (frequency regulation)
- Commanded Maximum Power (frequency regulation)
- L/H Votlage Ride-Through
- L/H Frequency Ride-Through
Changes to the utility interconnection standard allows the full utilization of distributed power electronic device capabilities and are needed to remedy the negative impacts of replacing well-regulated conventional generation sources with a variable generation resource, such as PV. The voltage regulation functions can be accomplished utilizing non-unity power factor operation that produces reactive power on a schedule or the reactive power generation can be the result of line voltage variation from nominal if it is implemented using the volt-VAr functions. Frequency regulation can be accomplished utilizing a real power curtailment method or by implementing a frequency-watt function that will dynamically adjust the real power generation according to the frequency at the terminals of the device. The voltage and frequency ride through requirements allow distributed generation to remain on-line when the utility experiences anomalies and assist in the recovery from an event. Past interconnection requirements caused the distributed devices to respond quickly to minimal anomalies and cease energizing the utility, which in a high penetration scenario could cause further decline in stability of the utility.