Single-phase Photovoltaic Research Articles

Low-Voltage Ride-Through Capability of a Single-Stage Single-Phase Photovoltaic System Connected to the Low-Voltage Grid

The progressive growing of single-phase photovoltaic (PV) systems makes the Distribution System Operators (DSOs) update or revise the existing grid codes in order to guarantee the availability, quality, and reliability of the electrical system. It is expected that the future PV systems connected to the low-voltage grid will be more active with functionalities of low-voltage ride-through (LVRT) and the grid support capability, which is not the case today. In this paper, the operation principle is demonstrated for a single-phase grid-connected PV system in a low-voltage ride-through operation in order to map future challenges. The system is verified by simulations and experiments. Test results show that the proposed power control method is effective and the single-phase PV inverters connected to low-voltage networks are ready to provide grid support and ride-through voltage fault capability with a satisfactory performance based on the grid requirements for three-phase renewable energy systems.

Grid-Connected Photovoltaic Power System Using Boost-HalfBridge Converter

This paper focuses on the power electronics used in the renewable energy systems especially in the photovoltaic applications. In recent years, interest in natural energy has grown in response to increased concern for the environment. Due to the limitations in the energy available from conventional sources, worldwide attention is being focused on renewable sources of energy. Especially, the energy obtained from solar arrays, becomes more and more important. In grid connected applications, a modular micro-inverter integrated with each photovoltaic (PV) panel can reduce the overall system cost and increase the system reliability and MPPT efficiency. In order to make the PV generation system more flexible and expandable, the backstage power circuit is composed of a high step-up converter and a pulse width-modulation (PWM) inverter. The traditional voltage-fed-full-bridge DC-DC converter suffers high cost, low transformer efficiency and discontinuous input current problems. A current-fed-half-bridge converter topology is utilized herewith continuous input current current, low cost and high efficiency features. A 210 W single-phase PV microinverter system with galvanic isolation is presented. By integrating microinverter to each PV panel, localized MPPT of each individual PV panel can be achieved, thus loading to fast tracking speed and higher system efficiency. Keywords - PV array, boost-half-bridge, grid-connected photovoltaic (PV) system, maximum power point tracking, repetitive current control.

Research on the MPPT Stability of the Single-Stage and Single-Phase Photovoltaic Grid-Connected System

At present the multi-stage transformation topology are more used in photovoltaic (PV) grid-connected system, although the control of this structure is relatively simple but the conversion efficiency is difficult to improve due to increase in transformation series. The single stage topology has a simple topology with high reliability and efficiency because of low power consumption, but control algorithm is more complex because of its power convert main circuit without DC-DC. This paper describes a method for maximum power point tracking (MPPT) in the single-stage and single-phase PV grid-connected system. In the paper, the nonlinear output characteristics of the PV including I-V & P-V are obtained in changed solar insulations or temperature based on MATLAB, and the MPPT algorithm which is based on the particle swarm optimization (PSO) method is also described. The simulation model of the single-stage and single-phase PV grid-connected system is built , and simulation results show the MPPT algorithm has excellent dynamic and static performances ,which verifies the PSO method is effective for MPPT in the single-stage and single-phase PV grid-connected system.

Three Level Single Phase Photovoltaic and Wind Power Hybrid Inverter

This paper presents a new topology of three-level single phase photovoltaic (PV) and wind power hybrid inverter. It consists of three main circuits; they are a hybrid controller circuit, a charger circuit, a pulse driver and full bridge circuit. The inverter is installed in front of Electrical Energy and Industrial Electronic Systems (EEIES) Cluster, Universiti Malaysia Perlis, Northern Malaysia. Its main energy source is a PV array and wind power generation. In this research, AC three-level waveform and square wave single phase PV and wind power hybrid inverter are developed and created by a microcontroller PIC16F627A-I/P and analyzed their performance comparisons. The result shows that the AC waveform which is formed by the PV and wind power hybrid inverter will effect on AC load rms voltage, AC current and current total harmonic distortion (CTHD), for a load of 20W 220V 50Hz AC water pump, its AC load rms voltage and current are higher when the single phase PV and wind power hybrid inverter is formed as AC square wave than as AC three-level waveform, but the CTHD is lower when the single phase PV and wind power hybrid inverter is formed as AC three-level waveform than as AC square wave.

Synchronization of a Single-phase Photovoltaic Generator With the Low-Voltage Utility Grid

The increased generation of electrical energy from renewable sources and its integration into the low voltage grid have necessitated regulations governing the connection of renewable energy generators to the grid. This was deemed necessary to preserve the integrity and the correct operation of the grid. This paper presents a new architecture of a hybrid phase lock loop circuit topology for synchronizing a single-phase inverter fed from a renewable energy source such as a photovoltaic (PV) generator to the low voltage grid. The system uses a digital phase lock loop (DPLL) architecture, which is based on the arctan phase detector, driving a phase lock loop (PLL) to synchronize a PV inverter with the grid. The proposed system has been tested by simulation using simulink/matlab. The test results demonstrate the ability of the system to synchronize a PV inverter with the grid and to re-establish synchronization following a sudden perturbation in the grid voltage such as a single or a multistep change in phase. The system is digital and can be readily implemented using an FPGA (field programmable gate array) and hence can be easily embedded in a home or small scale single-phase PV inverter.

A Single-Phase Voltage-Controlled Grid-Connected Photovoltaic System With Power Quality Conditioner Functionality

Future ancillary services provided by photovoltaic (PV) systems could facilitate their penetration in power systems. In addition, low-power PV systems can be designed to improve the power quality. This paper presents a single-phase PV system that provides grid voltage support and compensation of harmonic distortion at the point of common coupling thanks to a repetitive controller. The power provided by the PV panels is controlled by a Maximum Power Point Tracking algorithm based on the incremental conductance method specifically modified to control the phase of the PV inverter voltage. Simulation and experimental results validate the presented solution.

Control of Single-Stage Single-Phase PV Inverter

In this paper the issue of control strategies for single-stage photovoltaic (PV) inverter is addressed. Two different current controllers (the classical proportional-integral (PI) and the novel proportional-resonant (PR) controllers) have been implemented and an experimental comparison between them has been made. A complete control structure for the singlephase PV system is also presented. The superiority of the PR controller is demonstrated with respect to the PI controller in terms of harmonic current rejection and the capability to remove the steady-state error without using the voltage feedforward (VFF). The control strategy was successfully tested on a real 1.5 kW PV inverter.