Owing to rapid increase in PV penetration without inherent inertia, there has been an unremitting deterioration of the effective inertia of the existing power systems. This may pose a serious threat to the stability of power systems during disturbances if not taken care of. Hence, the problem of how to emulate Synthetic Inertia (SI) in PV Systems (PVS) to retain their frequency stability demands attention. Super Capacitor (SC)-based storage become an attractive option over the other energy storage types because of its high-power density, burst power handling capability, faster response and longer life cycle. Considering this, the authors here propose a novel PV-SC Cascaded Topology (PSCT) as a cost-effective approach to emulate SI by integrating a low voltage SC to a high voltage grid-connected PVS. The proposed PSCT helps in operating the SC as a voltage source rather than a current source. Thus, it eliminates the high gain requirements of the SC interfacing converters. The aim is to target two main frequency response services, i.e., Primary Frequency Response (PFR) and Synthetic Inertial Response (SIR), using a novel common control scheme, but without affecting any other energy intensive services. The authors introduced a Droop-Inspired (DI) method with an adjustable inertia constant to emulate dynamic inertia so that a wider range of Rate of Change of Frequency (RoCoF) values can be serviced with a limited storage. A very streamlined analysis was also carried out for sizing of the SC stage based on a simple Three-Point Linearization (TPL) technique and DI technique with a limited knowledge of the disturbance parameters. The whole system was initially validated in a MATLAB Simulink environment and later confirmed with the OPAL-RT Real-Time Simulator. The investigated response was subject to variation in terms of control parameters, changes in solar irradiance, grid frequency variation, etc.

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Frequency response services have become more important than ever in an increasingly inertia-less power system. A promising way to provide such services in a photovoltaic (PV) system is by hybridizing with supercapacitors (SC) due to their high power density, long operating cycles and fast response. The challenge, however, with a PV/SC system is what topology can effectively integrate such devices with so low and variable voltage, as well as how to control them for optimal utilization of their very limited capacity. This paper builds upon a previously introduced PV/SC cascade topology and proposes a complete control scheme for frequency services. A power segregation mechanism infers how the power demand is shared between SC and PV array, accounting for the operational boundaries of the former and occasionally deciding short-term curtailments for the latter. The proposed scheme involves also a voltage recovery function to slowly get the SC voltage back to the steady-state value after a disturbance, the latter being calculated via a newly introduced methodology. MATLAB/Simulink simulations validate the control efficacy under a series of frequency disturbances.

Frequency Response Services (FRS) have taken a special space among the family of ancillary services required for the stability of the Power Systems (PS). Falling of system inertia, being the inherent capability of the classical rotating generatorbased PS, has become a serious concern with the increase in inertia-less renewable energy sources like solar PV Systems (PVS). Hence, it draws the attention of the research community on how to emulate equivalent response from the PVS, either the existing ones or the future installations. Additional Energy Storage (ES) plays a vital role in providing Synthetic Inertia (SI) to the PVS. Super-capacitor (SC) has taken unique stand among the existing ESs due to its faster response, burst power handling capability, and longer life cycle. In this paper, a novel single magnetics (Inductor) based compact, non-isolated Tri-Port Converter (TPC) has been proposed. This allows the designer to integrate a low voltage SC unit to the PVS without the need of a high gain converter. The aim is to emulate SI in the grid connected PVS to provide the major FRS to the PS such as Inertial Response (IR) and Primary Frequency Response (PFR). Finally, the proposed TPC and the implemented control is verified via simulations in MATLAB/SIMULINK.