Evaluation of the Effective Active Power Reserve for Fast Frequency Response of PV with BESS Inverters Considering Reactive Power Control

Abstract

<jats:p>The increasing presence of distributed generation (DG) in the electrical grid determines new challenges in grid operations, especially in terms of voltage and frequency regulation. Recently, several grid codes have required photovoltaic (PV) inverters to control their reactive power output in order to provide voltage regulation services, and the allocation of a certain amount of active power reserve for fast frequency response (FFR) service during under-frequency contingencies is needed. This requirement involves a significant waste of energy for PV systems, due to the necessity to constantly operate in de-loaded mode, under normal operating conditions. In addition, the variability of the irradiance can affect the correct amount of active power reserve that the system can provide in the moments after an under-frequency occurrence. The increasing number of battery energy storage systems (BESSs), coupled to PV systems, can be used to provide a worthy contribution to this frequency regulation service. The aim of this paper is to analyze the efficiency of active power reserve provided by a BESS connected to the DC bus of a non-ideal grid-connected PV inverter, taking into account the impact of reactive power control. For this purpose, the contribution of BESSs to frequency regulation is discussed and, starting from an existing model of real inverter, an analytical formulation for active power reserve evaluation is presented. Results concerning the impact of reactive power control are also given. Finally, the possibility for a low voltage (LV) grid with aggregated PV systems and BESSs to contribute to grid active power reserve is considered. Different voltage control strategies are compared, defining a helpful new parameter.</jats:p>

Second Life Batteries Used in Energy Storage for Frequency Containment Reserve Service

“…The fast development of distributed generation brings new challenges, especially in the field of voltage and frequency regulation of the power grid [21]. Battery systems are becoming crucial providers of fast frequency control services, also known as fast frequency containment process (FCP) [22].…”

“…According to this study and others, the lifespan of BESS is most affected by the depth of discharge (DoD) and the average state of charge (SoC) [28][29][30]. Additionally, in [21], the operation of SLBs in BESS are simulated in three network support model cases-namely, peak shaving, voltage control in power systems, and ancillary services. During the study, the authors found a positive impact on the operation of the energy system at all voltage levels in the use of BESS (no economic evaluation included in this study).…”

Flexible Active Power Control for PV-ESS Systems: A Review

“…Literature [40] proposed a control solution for grid-connected microgrids, where an SC-based ESS was used to deal with the transient power exchange so that the robustness and reliability of the system was increased. Literature [41] used a Li-ion battery ESS to provide active power reserve, while the PV arrays operate at MPPT. Nevertheless, in this case, the reserved power is completely restored in the battery ESS, which is a costly solution due to the redundancy capacity of ESS.…”

Experimental tests and simulations about the efficiency of commercial hybrid inverters operating at variable power factor

“…Thus, for non-relevant generation plants to participate in voltage regulation, commercial hybrid inverter manufacturers have added new capabilities that allow them to inject/absorb reactive power into the grid by changing the power factor (PF) of the inverter. Anyhow, it is important to keep in mind that the conversion efficiency decreases with a non-unity PF since the additional inverter losses due to the supplied reactive power have to be considered (Garozzo & Tina, 2020).…”

“…It is common knowledge, in fact, that the conversion efficiency decreases with a non-unity PF, but the extent of the additional inverter losses due to the supplied reactive power is less well studied (Grab et al, 2022). In particular, to evaluate the power losses due to the production of reactive power, in literature some mathematical models have been proposed (Demirok et al, 2014;Garozzo & Tina, 2020;Grab et al, 2022;Rampinelli et al, 2014). In order to correctly analyse the power losses of the PV inverter, Chivelet's model has been used in (Garozzo & Tina, 2020;Rampinelli et al, 2014).…”