Abstract: An arrangement is provided for detecting the occurrence of an islanding condition in the connection of a distributed power generation source to an electrical power system or utility. In accordance with the present invention, a voltage or current signal is injected into the system, and the resulting system impedance is determined. The resulting determination is used as an indicator of the islanding condition. The detection arrangement allows the detection of islanding conditions even when the load is well matched to the generated power.

Abstract: An arrangement is provided for detecting the occurrence of an islanding condition in the connection of a distributed power generation source to an electrical power system or utility. In accordance with the present invention, a voltage or current signal is injected into the system, and the resulting system impedance is determined. The resulting determination is used as an indicator of the islanding condition. The detection arrangement allows the detection of islanding conditions even when the load is well matched to the generated power.

Abstract: A high voltage inverter cascades a plurality of multiple voltage level inverter modules each fed by an isolated dc energy unit to reduce the number of stages of the inverter required to generate a desired ac voltage. Thus, where the dc energy unit includes the secondary winding of an ac transformer, the number of each winding needed is reduced. By using active rectifiers operated in a boost mode to convert the transformer secondary voltage to dc for powering the inverter modules, regenerative operation can be achieved.

Abstract: Series voltage compensation is provided in an ac power line by connecting the inverter unit of a dynamic voltage restorer (DVR) in series with the primary winding of a load transformer, which may already be present, thereby eliminating the need for injection transformers. For three-phase ac power lines the three primary phase windings can be either wye or delta connected. If they are wye connected, a three-phase inverter with a common dc source is preferred. For delta connected primary phase windings, separate single-phase inverters each with its own floating dc source can be directly connected in series with each primary phase winding. Preferably however, the poles of a two-phase inverter are direct connected in series between two of the primary phase windings and a common source phase, and share a common dc source referenced to the common source phase.