Photovoltaic Power Converter Management in Unbalanced Low Voltage Networks with Ancillary Services Support

Abstract

The proliferation of residential photovoltaic (PV) prosumers leads to detrimental impacts on the low-voltage (LV) distribution network operation such as reverse power flow, voltage fluctuations and voltage imbalances. This is due to the fact that the strategies for the PV inverters are usually designed to obtain the maximum energy from the panels. The most recent approach to these issues involves new inverter-based solutions. This paper proposes a novel comprehensive control strategy for the power electronic converters associated with PV installations to improve the operational performance of a four-wire LV distribution network. The objectives are to try to balance the currents demanded by consumers and to compensate the reactive power demanded by them at the expense of the remaining converters’ capacity. The strategy is implemented in each consumer installation, constituting a decentralized or distributed control and allowing its practical implementation based on local measurements. The algorithms were tested, in a yearly simulation horizon, on a typical Portuguese LV network to verify the impact of the high integration of the renewable energy sources in the network and the effectiveness and applicability of the proposed approach.

Reactive Power Compensation with PV Inverters for System Loss Reduction

“…are predominately used in high voltage (HV) transmission systems. However, in recent years, there have been several contributions [2][3][4][5][6][7][8][9][10] where usage of grid-connected photovoltaic (PV) system inverters for reactive power generation (i.e., compensation) in distribution systems was proposed.…”

“…New control strategies for PV inverters installed in low voltage distribution systems are presented in Reference [9]. It was shown that proposed strategies can compensate load imbalance, reduce overvoltages and minimize reactive power flows.…”

“…These additional losses yield opportunity costs since active power generation must be reduced in order to generate reactive power. These additional opportunity costs for PV inverters operating at power factors less than unity is often neglected by researchers (e.g., in References [7][8][9]). This in turn could present a major obstacle for reactive power compensation by PV inverters for network losses reduction.…”

A Decision Support System Tool to Manage the Flexibility in Renewable Energy-Based Power Systems

“…This situation represents a non-optimal utilization of the renewables. Moreover, even though the Reverse Power Flow does not lead to a violation of the voltage and current limits, the protection scheme that is currently implemented in the distribution grid was not designed to handle the Reverse Power Flow, and for this reason the system is not able to guarantee adequate protection for the distribution system in such situations [46,47].…”

Ancillary Service with Grid Connected PV: A Real-Time Hardware-in-the-Loop Approach for Evaluation of Performances

“…Connection to the distribution grid is one of the most important aspects of the future of renewable energy sources. Undoubtedly, this represents a source of opportunities and technological problems to be addressed and solved, but very often, we do not dwell on the fact that these sources can also be used as a tool to provide innovative network services [1][2][3][4]. In the so-called micro-grids, that can work either in island mode or connected to the main electric network, there are several issues that needs to be addressed.…”