Direct usage of photovoltaic solar panels to supply a freezer motor with variable DC input voltage

In this paper, a single-phase photovoltaic (PV) inverter fed by a boost converter to supply a freezer motor with variable DC input is investigated. The proposed circuit has two stages. Firstly, the DC output of the PV panel that varies between 150 and 300 V will be applied to the boost converter. The boost converter will boost the input voltage to a fixed 300 V DC. Next, this voltage is supplied to the single-phase full-bridge inverter to obtain 230 V AC. In the end, The output of the inverter will feed a freezer motor. The PV panels can be stand-alone or grid-connected. The grid-connected PV is divided into two categories, such as with a transformer and without a transformer, a transformer type has galvanic isolation resulting in increasing the security and also provides no further DC current toward the grid, but it is expensive, heavy and bulky. The transformerless type holds high efficiency and it is cheaper, but it suffers from leakage current between PV and the grid. This paper proposes a stand-alone direct use of PV to supply a freezer; therefore, no grid connection will result in no leakage current between the PV and Grid. The proposed circuit has some features such as no filtering circuit at the output of the inverter, no battery in the system, DC-link instead of AC link that reduces no-loads, having a higher efficiency, and holding enough energy in the DC-link capacitor to get the motor started. The circuit uses no transformers, thus, it is cheaper and has a smaller size. In addition, the system does not require a complex pulse width modulation (PWM) technique, because the motor can operate with a pulsed waveform. The control strategy uses the PWM signal with the desired timing. With this type of square wave, the harmonics (5th and 7th) of the voltage are reduced. The experimental and simulation results are presented to verify the feasibility of the proposed strategy

Multilevel Converters: An Enabling Technology for High-Power Applications

| Multilevel converters are considered today as the state-of-the-art power-conversion systems for high-power and power-quality demanding applications. This paper presents a tutorial on this technology, covering the operating principle and the different power circuit topologies, modulation methods, technical issues and industry applications. Special attention is given to established technology already found in industry with more in-depth and self-contained information, while recent advances and state-of-the-art contributions are addressed with useful references. This paper serves as an introduction to the subject for the not-familiarized reader, as well as an update or reference for academics and practicing engineers working in the field of industrial and power electronics.Ministerio de Ciencia y Tecnología DPI2001-3089Ministerio de Eduación y Ciencia d TEC2006-0386

Reliability analysis of single-phase photovoltaic inverters with reactive power support

Reactive power support is expected to be an emerging ancillary requirement for single-phase photovoltaic (PV) inverters. This work assesses related reliability issues and focuses on the second stage or inversion process in PV inverters. Three PV inverter topologies are analyzed and their reliability is determined on a component-by-component level. Limiting operating points are considered for each of these topologies. The capacitor in the dc link, the MOSFETs in the inverting bridge, and the output filter are the components affected. Studies show that varying power-factor operation with a constant real power output increases the energy storage requirement as well as the capacitance required in the dc link in order to produce the double-frequency power ripple. The overall current rating of the MOSFETs and output filter must also be sized to accommodate the current for the apparent power output. Modeling of the inverter verifies the conditions for each of the components under varying reactive power support commands. It is shown that the production of reactive power can significantly increase the capacitance requirement, but the limiting reliability issue comes from the increased output current rating of the MOSFETs

Low order harmonic cancellation in a grid connected multiple inverter system via current control parameter randomization

In grid connected multiple inverter systems, it is normal to synchronize the output current of each inverter to the common network voltage. Any current controller deficiencies, which result in low order harmonics, are also synchronized to the common network voltage. As a result the harmonics produced by individual converters show a high degree of correlation and tend to be additive. Each controller can be tuned to achieve a different harmonic profile so that harmonic cancellation can take place in the overall system, thus reducing the net current total harmonic distortion level. However, inter-inverter communication is required. This paper presents experimental results demonstrating an alternative approach, which is to arrange for the tuning within each inverter to be adjusted automatically with a random component. This results in a harmonic output spectrum that varies with time, but is uncorrelated with the harmonic spectrum of any other inverter in the system. The net harmonics from all the inverters undergo a degree of cancellation and the overall system yields a net improvement in power quality

HARMONIC ANALYSIS FOR SOLAR PV ARRAY FED VSI USING CURRENT CONTROLLER

A common method in the study of voltage source inverters is the hypothesis of a voltage-type input source even in the case of renewable energy (RE). The converter is supplied by an renewable energy sources, such as a Solar photovoltaic Array, the dc-link voltage is controlled by the converter with the closed loop to extract the maximum power from the solar PV. The main aim of the paper is to reduce the harmonics by the low pass filter and analyze the total harmonic distortion with current controller technique in three level voltage source inverter. The use of perturb and observe MPPT will help to produce high output efficiency from solar PV cell. The simulation result for the paper is analysed using MATLAB/SIMULINK software and the values for the total harmonic distortion is calculate

Optimal control of a multilevel DC-link converter photovoltaic system for maximum power generation

This paper describes a new algorithm for optimal control of a PV system under partial shading. A multilevel DC-link is the essential part of the proposed system and its control engages a voltage-hold perturbation and observation (VH-P&O) method combined with a PWM algorithm with permutation of PV sources. The algorithm enables achieving the maximum power generation for any number of PV and converter modules. The main features of the control are: (i) a continual operation of all PV sources, shaded and non-shaded, at their maximum power points, (ii) delivery of all extracted power from PV sources to the load and (iii) generation of multilevel output voltage waveform with a low total harmonic distortion

A Review on Control Strategies and Topologies of Multi Level Converter System

In recent decades, high-performance and medium voltage energy management for academia and industry have been attracted by multi-level converter topologies. In addition, the multi-level principle is used without decreasing the inverter power output to synthesise the harmonic distortion on the output waveform. For the reduction of harmonic distortion in the output waveform, the multi-level principle is used. The following topologies are presented: diode clamped inverters (neutral point clamped), condenser clamped (flying condenser), multi-level cascading (dc source, etc.) and the most effective modulation methods built for this converter category: multi-level, selective harmonic removal and space m vectors. A series of different topologies are given in this paper. Multi-level inverters have been gaining popularity in research teams and in the production of industrial applications for high and medium voltage applications for 20 years. Moreover, compared to a conventional converter, multi-level inverters can generate switched waveforms with reduced harmonic slopes. Recently, multi-level inverters have increased interest in their ability to generate high-quality wave forms at lower frequencies; the multi-level topology used in dynamic restaurant voltages reduces the harmonic distortion of the inverter output waveform without inverter output losses. By integrating control techniques for multi-level inverters, this paper discusses the most common topologies, making their implementations flexible in some power applications in many industrial areas

Simulation of High Power Factor Single Phase Inverter For PV Solar Array

Photovoltaic (PV) systems are solar energy supplySystems which either supply power directly to an electrical equipment or feed energy into the public electricity grid. It focuses on the latest development of modelling and control of grid connected photovoltaic energy conversion system. In the photovoltaic system, power electronic conversion is necessary to improve the efficiency of PV panels and system stability. In these systems, the backstage power circuit consists of a high step-up DC to DC converter and a full-bridge inverter to convert DC to AC, as the grid voltage is AC in nature. Modelling of photovoltaic systems include modelling of SPV array, power electronics inverter/converter based on MATLAB/SIMULINK. This present control algorithm of a three-phase and single phase grid-connected photovoltaic (PV) system including the PV array and the electronic power conditioning (PCS) system, based on the MATLAB/Simulink software. It also discusses advances in MPP tracking technologies, the synchronization of the inverter and the connection to the grid

Grid Connected With Micro Solar Generator

Nowadays, the need of renewable energy sources in on the rise because of the acute energy crisis in electricity generation due to increasing consumption demand and populations. Thus, energy from the sun is the best option for the generation of electricity as it is available everywhere, pollution-free as well as is free to harness. Therefore, objective of this dissertation is to generate simulation framework of the grid connected micro solar generator and analyse its efficiency and performance which can benefits to both educational institutions and industrial field. A framework system has been done to extract maximum obtainable solar power from the photovoltaic array and converted it into alternating current before deliver to the utility grid through controlling and synchronization mechanisms. The system includes photovoltaic array, maximum power point tracker (MPPT), DC-DC boost converter, three-phase inverter, modulation techniques, voltage source controller (VSC) controller and utility grid. Overall findings indicate the implementation of the developed framework can be useful for the further investigation and improvement of the grid connected photovoltaic (GCPV) system. In addition, result also indicate that framework system have a lower total harmonic distortion of 1.17%. The simulation studies are carried out in Simulink MATLAB environment