This report will provide the performance of residential solar PV inverters during various voltage and frequency transient events typically found in the grid. The following steady-state, transient, and harmonics test data will be used to support SCE Field Engineering’s assessment of residential inverter behavior as well as influence the proper revision of standards, including UL1742 and IEEE 1547, in order to ensure that these are grid friendly devices. Additionally, the test results may be utilized to develop and validate solar PV models for distribution system impact studies.
Grid Advancement has tested fourteen residential inverters from various manufacturers listed in Table 1.0.1. These inverters were tested at the SCE Pomona EVTC lab. Below is a list of the inverters tested and their specifications. All residential inverters were fully tested on the AC side with the exceptions of Inverter 9 (micro-inverter) and Inverter 15 (rated at 120VAC) due to rating differences between the inverters and the test setup. Based on previous tests involving commercial rated inverters and the initial results from the residential inverters, the grid disconnection and short circuit tests were identified as having the most potential impact to the grid.
Key findings for load rejection:
- The inverters were islanded with NO Load to assess the worst condition when the inverters are disconnected from the grid.
- Inverters generate a high voltage (up to 300%) right after they are isolated from the grid
- Depending on the manufacturer, the voltage behavior varies among the different inverters after the initial over-voltage due to islanding.
- Inverters 4 & 5 (manufacturer #3) do NOT meet IEEE1547 islanding --- 2 seconds
- Inverters 4, 5, 8, 13, & 14 have their voltage above 100% for the longest times after grid disconnection