Impact of green power inverter-based distributed generation on distribution systems

A significant amount of green power is being installed at the distribution level through the installation of green power generation facilities in many parts of the United States and Canada. Green sources such as solar and wind are some of the green generation being interconnected at the distribution level. These non-conventional generators use inverter-based technologies and operate in parallel with utility distribution feeders. The fault behavior of an inverter-interfaced solar or wind distributed generator (DG) is determined by its control, which is significantly different from conventional synchronous and induction generators. In addition, utilities have expressed a concern that distributed generators interfaced to the grid via inverters could cause a transient overvoltage during a single phase to ground fault, after the substation breaker opens. The concern is that this overvoltage will damage utility equipment such as lightning arresters or saturate line-to-neutral rated utility feeder transformers resulting in transformer failure. This paper examines both the fault current and overvoltage issue and compares inverter based distributed generations (DGs) with conventional synchronous and induction DGs.