A Grid-Supporting Photovoltaic System Implemented by a VSG with Energy Storage

Abstract

Conventional photovoltaic (PV) systems interfaced by grid-connected inverters fail to support the grid and participate in frequency regulation. Furthermore, reduced system inertia as a result of the integration of conventional PV systems may lead to an increased frequency deviation of the grid for contingencies. In this paper, a grid-supporting PV system, which can provide inertia and participate in frequency regulation through virtual synchronous generator (VSG) technology and an energy storage unit, is proposed. The function of supporting the grid is implemented in a practical PV system through using the presented control scheme and topology. Compared with the conventional PV system, the grid-supporting PV system, behaving as an inertial voltage source like synchronous generators, has the capability of participating in frequency regulation and providing inertia. Moreover, the proposed PV system can mitigate autonomously the power imbalance between generation and consumption, filter the PV power, and operate without the phase-locked loop after initial synchronization. Performance analysis is conducted and the stability constraint is theoretically formulated. The novel PV system is validated on a modified CIGRE benchmark under different cases, being compared with the conventional PV system. The verifications demonstrate the grid support functions of the proposed PV system.

Power Electronics in Renewable Energy Systems

“…The practical experiments show that the proposed technique works. Xu et al [16] introduce methods to provide grid-supporting functions in photovoltaic systems by utilizing battery energy storage to create a virtual synchronous generator. The power system is claimed to be able to operate without phase locked loop grid synchronizing.…”

Droop characteristics based damping and inertia emulation of DC link in a hybrid microgrid

“…The limited size and allowable voltage variation across DC link capacitor limits the inertia capacity of overall system. In [27], PV system is directly connected across the DC link and a battery energy storage system is used to operate the PV at maximum power point (MPP) and maintain voltage across the DC link using coordination control in grid connected applications. A battery and ultracapacitor based energy storage system is used in [28] to regulate the frequency using the SG characteristics.…”

“…A battery and ultracapacitor based energy storage system is used in [28] to regulate the frequency using the SG characteristics. However, control strategies used in [27,28], do not have the fixed DC link voltage. Also, inverter frequency varies with the changes in irradiance.…”

Coordinated reactive power strategy using static synchronous compensator for photovoltaic inverters

“…In addition, the progress of power electronics has revealed a great possibility and potential for integration of renewable energy systems with grid . For a PV system operating in a grid‐connected environment, there are three different modes of operation: grid‐forming, grid‐feeding, and grid‐supporting . In general, the off‐grid PV systems deal with the grid‐forming mode, whereas in the grid feeding mode, the PV inverter delivers power to the grid by acting as an ideal current source.…”