Provision of ancillary services in a grid-connected photovoltaic distributed energy resource

The constant growth of distributed energy resource (DER) in the electric power system (EPS) is a reality on account of some aspects, for example, technical, financial, environmental. The insertion of DERs can be positive, providing ancillary services, for example, harmonic mitigation, or negative, causing overvoltage, depending on the proper control and the characteristics of the grid. This paper proposes a pq-based control strategy for distributed generation, wherein the studied system is composed by a photovoltaic DER and a three-phase converter for processing the generated power and providing ancillary services (ASs) to a three-wire EPS. The power control is based on the power balance between the grid and the converter. Besides supplying active and reactive power, the proposed strategy can provide ASs by controlling the grid currents from a pq transformation. Some advantages over other solution can be mentioned, such as reduced sensor number and instantaneous control response. In addition, neither additional harmonic-extraction method nor a phase-locked loop is required. To validate this study and theoretical considerations, simulation results are presented and evaluated. From tests in a downscaled laboratory setup, experimental results are also presented to verify the effectiveness of the proposed control strategy.