CONTROL OF Z-SOURCE INVERTER USING ADVANCED FUZZY LOGIC CONTROL FOR PV SYSTEM APPLICATIONS

The Z-source inverter (ZSI) has some advantages and suitable for all the Photo Voltaic (PV) system. This paper deals with a new topology for all ZSI with battery for PV power generation and distribution system. Thus the battery is connected parallel to one of the capacitors in Z-Source (ZS) network, instead of involving an additional DC/DC converter. This system builds all the advantages of ZSI. The operating principle of the new topology is designed and the design scheme of the ZS network is explained and also closed-loop control strategy for the proposed system is analyzed to manage the three power flow of PV panel, grid, and battery in the system. Maximum Power Point Tracking (MPPT) has been implemented in the ZSI with battery based PV system by using the proposed control strategy. Different modes of operation are simulated. Simulation for this proposed system using fuzzy logic control technique is completely analyzed through the MATLAB/SIMULINK software

Parameter Extraction of PV Module using NLS Algorithm with Experimental Validation

Photovoltaic (PV) module parameters act an important task in PV system design and simulation. Most popularly used single diode Rsh model has five unknown electrical parameters such as series resistance (Rse), shunt resistance (Rsh), diode quality factor (a), photo-generated current (Ipg) and dark saturation current (Is) in the mathematical model of PV module. The PV module output voltage and current relationship is represented by a transcendental equation and is not possible to solve analytically. This paper proposes nonlinear least square (NLS) technique to extract five unknown parameters. The proposed technique is compared with other two popular techniques available in the literature such as Villalva’s comprehensive technique and modified Newton-Raphson (N-R) technique. Only two parameters Rse and Rsh are estimated by Villalva’s technique, but all single diode unknown electrical parameters can be estimated by the NLS technique. The accuracy of different estimation techniques is compared in terms of absolute percentage errors at MPP and is found the minimum for the proposed technique. The elapsed time for parameter estimation for NLS technique is minimum and much less compared to other two techniques. Extracted parameters of polycrystalline ELDORA-40 PV panel by the proposed technique have been validated through simulation and experimental current-voltage (I-V) and power-voltage (P-V) characteristics

Gravitational search algorithm-based photovoltaic array reconfiguration for partial shading losses reduction

The operation of a photovoltaic (PV) array under partial shading (PS) conditions represents a great challenge in the PV systems. The PS of a PV array causes a reduction of the generated power of such array and increases the thermal losses inside the shaded modules. This paper presents the gravitational search algorithm (GSA) to optimally fully reconfigure the PV array with the purpose of reducing the PS losses. The single diode PV model is used to model the PV module. The GSA code is built using MATLAB environment. The target of the optimized problem is to minimize the irradiance level mismatch index. The reconfigurable PV array is modelled using MATLAB/SIMULINK environment. The validity of the GSA-based reconfigurable PV array is verified by the simulation results. The effectiveness of proposed PV array is evaluated by comparing its results with that of other PV array configurations under different PS and PV modules conditions

Thermography-based virtual MPPT scheme for improving PV energy efficiency under partial shading conditions

This paper proposes a new thermography-based maximum power point tracking (MPPT) scheme to address photovoltaic (PV) partial shading faults. Solar power generation utilizes a large number of PV cells connected in series and in parallel in an array, and that are physically distributed across a large field. When a PV module is faulted or partial shading occurs, the PV system sees a nonuniform distribution of generated electrical power and thermal profile, and the generation of multiple maximum power points (MPPs). If left untreated, this reduces the overall power generation and severe faults may propagate, resulting in damage to the system. In this paper, a thermal camera is employed for fault detection and a new MPPT scheme is developed to alter the operating point to match an optimized MPP. Extensive data mining is conducted on the images from the thermal camera in order to locate global MPPs. Based on this, a virtual MPPT is set out to find the global MPP. This can reduce MPPT time and be used to calculate the MPP reference voltage. Finally, the proposed methodology is experimentally implemented and validated by tests on a 600-W PV array

Variations of PV module parameters with irradiance and temperature

© 2017 The Authors. Published by Elsevier Ltd. This paper presents a comparison of common and well-documented methods for varying the single-diode model parameters extracted at standard test conditions (STC) of a PV module to suit varying operating conditions of irradiance and temperature. To perform such a comparison, accurate values of the single-diode parameters at STC are required. These were obtained using well-established numerical and iterative methods. The Newton-Raphson method was found to be most accurate for obtaining these parameters at STC. Consequently, these parameters were used to compare the methods of varying the single-diode model parameters with temperature and irradiance. MATLAB software has been developed to evaluate the performance of each method using the Shell SQ150 PV module. Results are compared with measured data and discussion of the accuracy of various methods is presented. .Published versio

Non-Uniform Aged Modules Reconfiguration for Large-Scale PV Array

© 2001-2011 IEEE. In the past decades, a large number of photovoltaic (PV) plants have been built. Due to the minor physical differences between PV cells and the influence of environmental factors such as rains, temperature, and humidity, the aging of a PV array is often distributed unevenly within each PV module. This non-uniform aging causes further decreased output power, which is often easily observed for large size PV arrays. Although the global maximum power point tracking (GMPPT) strategy can improve the output power, the GMPPT cannot exploit the maximal power generation potential from non-uniform aging PV arrays. In order to exploit further the power generation potential and extend the service time of non-uniform aging PV arrays, a novel PV array reconfiguration method is developed in this paper. The concept of cell unit is applied to investigate the aging phenomenon of PV modules, and each PV module is assumed to be composed of three submodules, while these three submodules within any single PV module might have different aging conditions and, thus, different power-output capacities. The challenge is how to rearrange the PV array under the cases where: 1) each PV module has non-uniformly aged cell units; 2) there are a large number of PV modules; and 3) the voltage working range is restricted. To solve these problems, a nonlinear integer programming problem is formulated to maximize the power output under the constraints of non-uniformly aging and voltage restrictions. A small size 7×10 PV array is simulated to illustrate the proposed method. Furthermore, medium size 20×10 and large size 125×20 PV arrays are employed to verify the feasibility of the proposed method. A 1.5 kW 2×4 real PV array under non-uniform aging conditions is presented and experimentally tested to confirm the proposed rearrangement method

Online two-section PV array fault diagnosis with optimized voltage sensor locations

Photovoltaic (PV) stations have been widely built in the world to utilize solar energy directly. In order to reduce the capital and operational costs, early fault diagnosis is playing an increasingly important role by enabling the long effective operation of PV arrays. This paper analyzes the terminal characteristics of faulty PV strings and arrays, and it develops a PV array fault diagnosis technique. The terminal current-voltage curve of a faulty PV array is divided into two sections, i.e., high-voltage and low-voltage fault diagnosis sections. The corresponding working points of healthy string modules and of healthy and faulty modules in an unhealthy string are then analyzed for each section. By probing into different working points, a faulty PV module can be located. The fault information is of critical importance for the maximum power point tracking and the array dynamical reconfiguration. Furthermore, the string current sensors can be eliminated, and the number of voltage sensors can be reduced by optimizing voltage sensor locations. Typical fault scenarios including monostring, multistring, and a partial shadow for a 1.6-kW 3 $times$ 3 PV array are presented and experimentally tested to confirm the effectiveness of the proposed fault diagnosis method

Power Hardware-in-the Loop Simulation ???????????? ????????? ??? ????????? ?????? ?????? ?????????

Department of Electrical EngineeringIn the prototype development process, the product functional testing could be expensive and time-consuming. In various industries such as aviation, automobiles, and electric power, Hardware-In-the-Loop Simulation (HILS) is used in the product development process. By using HILS, the system which is linked with the developed product is configured by simulation to provide a virtual operating environment. So, a variety of functions can be tested in an environment similar to the actual before the final product development stage. HILS performs simulation in real time to simulate the system same as actual operation. Various technical problems arise in this process, and a lot of research has been going on to solve the problem. In this paper, computation methods are proposed to improve the real-time simulation performance of a photovoltaic (PV) cell model for power hardware-in-the-loop simulation (PHILS) applications. In PHILS, high computation performance is required because the simulator should complete the target model calculations in a real-time manner without overrun errors. One solution is to reduce the computation time of the target model. To solve nonlinear PV cell model equations, numerical methods used for solving the nonlinear equations can be used. However, these methods can be computationally intensive. In order to optimize performance for PHILS, performance of Newton-Raphson and Halley???s numerical methods are compared and methods for choosing an initial value are proposed, which affect the computation time of the numerical iterations. Using the proposed initial value decision methods, the computation time can be drastically reduced. The target PV cell model, in which the computation time improvement method is applied, is verified in static and dynamic conditions to verify the accuracy of the model in the PHILS system. In addition, two PHILS tests were conducted to show examples of HILS for development of PV system power converter. First test is Maximum Power Point Tracking (MPPT) function test and second is to output the voltage of Differential Power Processing (DPP) converter model. Also, the real-time simulation for large-scale PV system is described to show the computation speed in extended model.ope

Efficiency improvement of non-uniformly-aged PV arrays

The utilization of solar energy by photovoltaic (PV) systems have received much research and development (R&D) attention across the globe. In the past decades, a large number of PV array have been installed. Since the installed PV arrays often operate in harsh environments, non-uniform aging can occur and impact adversely on the performance of PV systems, especially in the middle and late periods of their service life. Due to the high cost of replacing aged PV modules by new modules, it is appealing to improve energy efficiency of aged PV systems. For this purpose, this paper presents a PV module reconfiguration strategy to achieve the maximum power generation from non-uniformly aged PV arrays without significant investment. The proposed reconfiguration strategy is based on the cell-unit structure of PV modules, the operating voltage limit of gird-connected converter, and the resulted bucket-effect of the maximum short circuit current. The objectives are to analyze all the potential reorganization options of the PV modules, find the maximum power point and express it in a proposition. This proposition is further developed into a novel implementable algorithm to calculate the maximum power generation and the corresponding reconfiguration of the PV modules. The immediate benefits from this reconfiguration are the increased total power output and maximum power point voltage information for global maximum power point tracking (MPPT). A PV array simulation model is used to illustrate the proposed method under three different cases. Furthermore, an experimental rig is built to verify the effectiveness of the proposed method. The proposed method will open an effective approach for condition-based maintenance of emerging aging PV arrays