Abstract
This paper proposes an Indirect Matrix Converter (IMC)-based grid-tied Photovoltaic (PV) system for Smart Grids (SGs). The PV array injects current in the ‘dc link’ of the IMC through an inductive link, and is connected to the SG with shunt and series connections, allowing for the compensation of current- and voltage-related Power Quality (PQ) issues, respectively, for the sensitive loads and the SG connection. A direct sliding mode-based controller is proposed to guarantee nearly sinusoidal currents in the connection to the SG, and sinusoidal voltages guaranteeing compliance with international standards, when supplying the sensitive loads. Additionally, a novel control approach for the ‘dc link’ voltage is synthesised to allow for the control of both the PV array current and the power flow to the SG. To guarantee the semiconductors safe commutation an asynchronous commutation strategy is derived. Simulation and experimental results show that the proposed system significantly improves PQ in the SG, minimizing the total harmonic distortion of the currents injected in the SG, and guaranteeing the quality of the voltage supplied to the sensitive loads, even in the occurrence of voltage sags or overvoltages.
Highlights
The increasing penetration of Distributed Energy Resources (DERs), in particular Photovoltaic (PV)systems in the Low-Voltage (LV) and Medium-Voltage (MV) grid and the growing use of power-electronics based equipment are leading to new challenges for distribution system operators (DSOs) and critical consumers
‘dc link’ voltage that can be used for controlling the PV array operating point, considering that the array is directly connected to the converter terminals
The PV array is directly connected to the Indirect Matrix Converter (IMC) ‘dc link’, the switching vector applied to the converter has an impact on the PV array operating point
Summary
The increasing penetration of Distributed Energy Resources (DERs), in particular Photovoltaic (PV). Systems in the Low-Voltage (LV) and Medium-Voltage (MV) grid and the growing use of power-electronics based equipment are leading to new challenges for distribution system operators (DSOs) and critical consumers These include Power Quality (PQ) issues such as low-order current harmonics, due to the use of non-linear loads, resulting in additional losses and voltage distortion in the point of connection to the grid (Point of Common Coupling—PCC) [1]. The shunt part of the IMC acts as a voltage-step-up converter with a minimum transfer ratio of 1.155, with no need for an additional dc/dc converter and full operating point range as long as the PV system is sized so that the open circuit voltage does not exceed the limit set by the converter modulation [15,31] This limitation in PV array voltage may increase the system losses and reduces the safety issues and allows for lower power operation. Simulation and experimental results confirm that the PV system operates according to the SG integration requirements
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