Maximum Power Point Voltage Research Articles

Integrated cooling systems and maximum power point tracking of fuzzy logic controller for improving photovoltaic performances

The nonlinearity of solar irradiation and temperature leads to unstable photovoltaic (PV) outputs and decrease in efficiency. A method based on experimental study is developed to maximize the output of the PV panels using the combination of PV cooling system and fuzzy logic, fuzzy logic (FL)-based constant voltage (CV) maximum power point tracking (MPPT) algorithm. The PV cooling system reduces the PV panel temperature to the optimum temperature, while the FL-based CV MPPT algorithm tracks the maximum power of the PV panel. Experimental results showed that the combination of the two methods in a PV system results in improving the photovoltaic performances. Thus, the PV panel outputs increase when the PV panel works at its optimum temperature. This integrated FL-based CV MPPT controller proves the effectiveness in improving PV performances for any weather condition.

Dynamic Reconfiguration of Thermoelectric Generators for Vehicle Radiators Energy Harvesting Under Location-Dependent Temperature Variations

Conventional internal combustion engine vehicles generally have less than a 30% of fuel efficiency, and the most wasted energy is dissipated in the form of heat energy. The excessive heat dissipation is a primary reason of poor fuel efficiency, but reclamation of the heat energy has not been a main focus of vehicle design. Thanks to thermoelectric generators (TEGs), wasted heat energy can be directly converted to electric energy. All the heat exchangers, including vehicle radiators, gradually cool down the coolant or gas from the inlet to outlet. TEG modules are commonly mounted throughout the heat exchanger to fulfill the required power density and voltage. Each TEG module has a different hot-side temperature by the mounting location (distance from the inlet) and thus different maximum power point (MPP) voltage and current. Nevertheless, TEG modules are commonly connected in series and parallel, where both the ends are connected to a single power converter. As a result, the whole TEG module array exhibits a significant efficiency degradation even if the power converter has the MPP tracking capability. Although material and device researchers have been putting a lot of effort in enhancing TEG efficiency, such system-level issue has not been deeply investigated. This paper proposes a cross-layer, system-level solution to enhance TEG array efficiency introducing online reconfiguration of TEG modules. The proposed method is useful for any sort of TEG arrays to reclaim wasted heat energy, because heat exchangers generally have different inlet and outlet temperature values. This paper also introduces a complete design and implementation showcase of a reconfigurable TEG module building block. Experimental results show up to a 34% enhancement using the proposed method compared with a fixed array structure, which is a common practice.

Online dynamic conductance estimation based maximum power point tracking of photovoltaic generators

In this paper, a novel method of maximum power point tracking of renewable energy generators is proposed, utilizing the sum of dynamic and static conductance as maximum power point tracking loop variable. This allows to formulate the maximum power point tracking problem as a typical closed-loop stabilization task of non-linear static plant with zero reference. Consequently, a simple integrative controller is shown to be sufficient to ensure zero steady-state maximum power point tracking error with easily determinable nominal dynamics. A recently revealed method of online photovoltaic generator dynamic conductance estimation allowing robust terminal voltage control is utilized. Moreover, it is revealed that the resulting maximum power point tracking loop plant is piecewise linear around the maximum power point, i.e. for given environmental conditions two different convergence rates are expected, depending on the relative value of operating voltage to maximum power point voltage. Presented analytical outcomes are verified by application of the proposed maximum power point tracking structure to a grid-connected photovoltaic generator system under robust voltage control.

Design, Modeling, and Control of a Novel Hybrid-Excited Flux-Bidirectional-Modulated Generator-Based Wind Power Generation System

This paper proposes a novel hybrid excited generator, which is suitable for a variable-speed wind power generation system. Two sets of excitation sources are employed, which are permanent magnets (PMs) on the rotor and the field windings on the stator. The rotor is design with PM-iron structure, namely the PMs and iron poles are alternatively located in rotor, which can provide PM excitation and flux modulating simultaneously. Meanwhile, the adjacent stator teeth are designed with different height, which enables the stator with flux modulating effect, and, therefore, bidirectional flux modulating can be achieved. Some specific harmonics excited by the rotor PMs can be effectively adjusted by the field current, and the back electromotive force and electromagnetic torque can be regulated accordingly. Therefore, the proposed generator can achieve constant voltage control and maximum power point tracking control by controlling the field current. The design considerations and field regulating principle are analytically investigated. An improved Tabu search algorithm is used to optimize the proposed generator, and finite-element method is used to realize preliminary study of the electromagnetic performances. A prototype is manufactured and experimental tests are conducted to verify the theoretical analysis and control strategies.

LOAD SHARING REGULATION OF A GRID-CONNECTED SOLAR PHOTOVOLTAIC SYSTEM IN KARBALA CITY

Microgrid is an effective solution for increasing the reliability of power distribution system using renewable energy sources. In this research, a solar photovoltaic (PV) power system designed for extraction maximum power, i.e. 100kW (at standard conditions, 1000 W/m2 and 25oC) is simulated for grid utilities. For extraction maximum power, the duty ratio of a DC-DC converter is adjusting based on the specific value of maximum power point (MPP) voltage of the PV array. Thus, the DC voltage of the inverter side is kept constant to meet the grid specifications, e.g. 400V and 50Hz. The PV array is modelled by nonlinear equations which describe the effect of real irradiance levels (for Karbala city) on DC voltage. The PV power system is designed in an actual location in Karbala city for supplying a three-phase load, e.g. about 62 kW. Due to the fluctuations in solar irradiance, a load sharing between the PV power system and the grid is controlled. The load sharing is verified numerically by the Newton-Raphson method for a three-bus ring distribution system. Numerical and simulation results show the capability of the designed PV power system to share the load with grid over the year.

Maximum power extraction in solar renewable power system - a bypass diode scanning approach

The effectiveness of solar energy as a viable energy source is hampered by various factors including high cost of components and lowered operating efficiency due to partial shading. Partial shading reduces the output of not only the shaded part of the panel but also the other panels connected to the same photovoltaic (PV) array. This paper discusses the benefits of using a bypass diode based voltage drop measurement and maximum power point tracking (MPPT) system in the power generation of a PV array. An algorithm to find the global maximum power in short span of time is also presented. MATLAB is then used to perform the simulation of the proposed algorithm on a 3 × 3 photovoltaic array and the results are checked against actual outdoor tests to test the validity of the proposed method. The proposed method holds even when extended to any array combinations for practical applications.

Matlab based simulation model of standalone DC Microgrid for Remote Area Power Applications

DC microgrids are playing an important role in remote area power applications like power supply to off-grid tele communication towers, off-grid data centres, rural electrification etc. and moreover these are extensively used, as these appear as solutions for integrating two or more renewable energy resources. In this paper, photovoltaic (PV) and wind energy systems have been integrated along with batteries and a load to form an autonomous DC microgrid with high reliability and stability. The primary aspects which are to be taken into consideration in a standalone DC microgrid are voltage regulation, load sharing and battery management. In this paper, an energy management strategy is proposed which includes maximum power point tracking (MPPT) algorithms and voltage droop control method. This strategy ensures optimal power sharing among the sources and increases reliability and stability profile of the microgrid. The operation of the microgrid in different modes and the behaviour of the system at different operating conditions is studied by varying the solar irradiance and wind speed for specific time periods. The simulation is done in Matlab Simulink software and the results are obtained.

Comparison of Free Energy Loss Analysis and Synergistic Efficiency Gain Analysis for PERC Solar Cells

The optimization of a solar cell requires a detailed knowledge of the efficiency limiting power losses. The free energy loss analysis (FELA) and the synergistic efficiency gain analysis (SEGA) both allow for studying these power losses. We compare both approaches for industrial passivated emitter and rear solar cells. The resistive losses calculated with both approaches are in good agreement with each other. In contrast, we find deviations of more than 20% for losses because of charge carrier recombination. From an analytical description of both methods, we conclude that these deviations are caused by a shift of the maximum power point voltage in an improved cell which is not considered in the FELA. The deviation of the losses critically depends on the specific loss channel investigated. In contrast with implied front-side power gains which are usually underestimated, rear-side or absorber gains can be over or underestimated by the FELA depending on the magnitude of the power loss. These differences follow from the Fermi level splitting which is affected differently by recombination currents at different locations. For an accurate determination of the efficiency improvement potential of individual recombination loss channels, we therefore recommend to perform a SEGA.

A New Approach for Photovoltaic Arrays Modeling and Maximum Power Point Estimation in Real Operating Conditions

In this paper, a new approach for photovoltaic (PV) arrays modeling and maximum power point estimation (MPPE) in real operating conditions is presented. The PV array polynomial model is developed from its single-diode equivalent circuit, and the parameters of the proposed model are estimated by measuring the voltage and current of three points around the maximum power point (MPP). The maximum power point voltage (MPPV) is then calculated from the proposed model, and the PV array voltage is fixed at MPPV. Therefore, unlike the maximum power point tracking (MPPT) algorithms, there is no oscillation around the MPP. Using the PV array polynomial model with only three measurements around the operating point, results in less calculation burden, increases the estimation speed and decreases the I-V curve estimation process loss. In order to validate the proposed MPPE algorithm, we have compared it with the most commonly used perturb and observe (P&O) MPPT algorithm, a zero oscillation adaptive P&O technique, and a fast MPPT method by simulation and experimental results.

Fuel Cell Emulator with MPPT Technique and Boost Converter

<span lang="EN-GB">This paper presents the simulation between fuel cell model and interleaved DC-DC boost converter (IBC) using a constant voltage maximum power point tracking (MPPT) technique. The main advantage of this method is it had the simplest algorithm and can be computed for the high efficiency IBC. The MPPT technique forces the fuel cell to meet the maximum power that the fuel cell can generate. To test the IBC along with the MPPT algorithm, MATLAB/Simulink simulation is carried out. This MPPT method increases the efficiency of power delivered from the fuel cell. The IBC has also chosen for its advantages of reduction of passive component's size, as well as reduced the current ripple that could affect the fuel cell stack. It is envisaged that the MPPT method of constant voltage gives a handful of help in designing a low cost and high efficient fuel cell system along with the interleaved boost converter chosen</span>

A grid-connected single-phase photovoltaic micro inverter

In this paper, the topology of a single-phase grid-connected photovoltaic (PV) micro-inverter is proposed. The PV micro-inverter consists of DC-DC stage with high voltage gain boost and DC-AC conversion stage. In the first stage, we apply the active clamp circuit and two voltage multipliers to achieve soft switching technology and high voltage gain. In addition, the flower pollination algorithm (FPA) is employed for the maximum power point tracking (MPPT) in the PV module in this stage. The second stage cascades a H-bridge inverter and LCL filter. To feed high quality sinusoidal power into the grid, the software phase lock, outer voltage loop and inner current loop control method are adopted as the control strategy. The performance of the proposed topology is tested by Matlab/Simulink. A PV module with maximum power 300W and maximum power point voltage 40V is applied as the input source. The simulation results indicate that the proposed topology and the control strategy are feasible.

Review of Maximum Power Point Tracking Control of Photovoltaic Systems in Case of Uniform & Non-uniform Irradiance Conditions

It is crucial to improve the photovoltaic (PV) system efficiency and to develop the reliability of PV generation control systems. One of the approaches to increase the efficiency of PV power generation system is to operate the PV systems optimally at the maximum power point. However, the PV system can be optimally operated only at a specific output voltage; otherwise the output power fluctuates under intermittent weather conditions. In addition, it is very difficult to test the performance of PV systems controller under the same weather condition during the development process where the field testing is costly and time consuming. For these reasons, the presentation is about the state of the art techniques to track the maximum available output power of photovoltaic systems called maximum power point tracking (MPPT) control systems. This topic could be also one of the most challenges in photovoltaic systems application that has been receiving much more attention worldwide. The talks will cover the application of intelligent techniques by means the artificial neural network (ANN) and fuzzy logic controller scheme using polar information to develop a novel real-time simulation technique for MPPT control by using dSPACE real-time interface system. In this case, the three-layer feed-forward ANN is trained once for different scenarios to determine the global MPP voltage and power and the fuzzy logic with polar information controller takes the global maximum power point (MPP) voltage as a reference voltage to generate the required control signal for the power converter. This type of fuzzy logic rules is implemented for the first time in MPPT control application. The proposed method has been tested using different solar cell technologies such as monocrystalline silicon, thin-film cadmium telluride and triple junction amorphous silicon solar cells. The verification of availability and stability of the proposed system through the real-time simulator shows that the proposed system can respond accurately for different scenarios and different solar cell technologies. In other cases, one of the main causes of reducing energy yield of photovoltaic systems is the partially shaded condition. Although the conventional MPPT control algorithms operate well in a uniform solar irradiance, they do not operate well in non-uniform solar irradiance conditions. The non-uniform conditions cause multiple local maximum power points on the power-voltage curve. The conventional MPPT methods cannot distinguish between the global and local peaks. Since the global power point may change within a large voltage window and also its position depends on shading patterns, it is very difficult to recognize the global operating point under partially shaded conditions. From these reasons, the presentation will address the effectiveness of the proposed MPPT method to solve the partially shaded conditions under the experimental real-time simulation technique based dSPACE real-time interface system for different size of PV arrays, such as 3x3(0.5kW) and 20x3(3.3kW) and different interconnected PV arrays, for instance series-parallel (SP), bridge link (BL) and total cross tied (TCT) configurations.

Linear Operation of Photovoltaic Array With Directly Connected Lithium-Ion Batteries

This paper proposes linear operation of a photovoltaic array which is directly connected to lithium-ion batteries. The array voltage is fixed at the total battery voltage. When the amount of insolation is given, the array power decreases as the cell temperature rises. The maximum power point (MPP) voltage at the highest temperature of a year is selected as the array voltage. This voltage determines the optimal number of the batteries. The array power is guaranteed to be equal to the MPP power or greater through the year. Some simulation and experiment were executed to verify the effectiveness of the method. The utilization efficiency reaches 96.5%. The loss of power proved to be small compared with the maximum power point tracking, which can be economically recovered by using PV modules of larger capacity. A simple switch can substitute for a dc–dc converter.

Analysis and Design of a Thermoelectric Energy Harvesting System With Reconfigurable Array of Thermoelectric Generators for IoT Applications

In this paper, a novel thermoelectric energy harvesting system with a reconfigurable array of thermoelectric generators (TEGs), which requires neither an inductor nor a flying capacitor, is proposed. The proposed architecture can accomplish maximum power point tracking (MPPT) and voltage conversion simultaneously via the reconfiguration of the TEG array, and demonstrate significantly improved power conversion efficiency over the conventional switching converter and switched-capacitor architectures. Two systematical scaling approaches—powers-of-two scaling and maximum-factor scaling—are presented and analyzed to serve as the design guideline, catering for reconfigurable TEG arrays of different sizes. In order to optimize the chip area required, a custom-designed, multi-level hierarchy and systematically scalable switch array that requires a reasonable number of switches is also developed to enable the reconfiguration of the TEG array. The 16-node and 12-node versions of the proposed system have been implemented in a standard 0.35- $\mu \text{m}$ CMOS process. Measurement results verify the analysis, and confirm that the proposed system can maintain a higher than 88.8% efficiency over a wide range of temperature gradients.

Design of A Grid Integrated PV System with MPPT Control and Voltage Oriented Controller using MATLAB/PLECES

This paper presents model of a grid-integrated photovoltaic array with Maximum Power Point Tracker (MPPT) and voltage oriented controller. The MPPT of the PV array is usually an essential part of PV system as MPPT helps the operating point of the solar array to align its maximum power point. In this model, the MPPT along with a DC-DC converter lets a PV generator to produce continuous power, despite of the measurement conditions. The neutral-point-clamped converter (NPC) with a boost converter raises the voltage from the panels to the DC-link. An LCL-filter smoothens the current ripple caused by the PWM modulation of the grid-side inverter. In addition to the MPPT, the system has two more two controllers, such as voltage controller and a current controller. The voltage control has a PI controller to regulate the PV voltage to optimal level by controlling the amount of current injected into the boost stage. Here, the grid-side converter transfers the power from the DC-link into the grid and maintains the DC-link voltage. Three-phase PV inverters are used for off-grid or designed to create utility frequency AC. The PV system can be connected in series or parallel to get the desired output power. To justify the working of this model, the grid-integrated PV system has been designed in MATLAB/PLECS. The simulation shows the P-V curve of implemented PV Array consisting 4 X 20 modules, reactive, real power, grid voltage and current.

Seven indicators variations for multiple PV array configurations under partial shading and faulty PV conditions

The goal of this paper is to model, compare and analyze the performance of multiple photovoltaic (PV) array configurations under various partial shading and faulty PV conditions. For this purpose, a multiple PV array configurations including series (S), parallel (P), series-parallel (SP), total-cross-tied (TCT) and bridge-linked (BL) are carried out under several partial shading conditions such as, increase or decrease in the partial shading on a row of PV modules and increase or decrease in the partial shading on a column of PV modules. Additionally, in order to test the performance of each PV configuration under faulty PV conditions, from 1 to 6 Faulty PV modules have been disconnected in each PV array configuration. Several indicators such as short circuit current (Isc), current at maximum power point (Impp), open circuit voltage (Voc), voltage at maximum power point (Vmpp), series resistance (Rs), fill factor (FF) and thermal voltage (Vte) have been used to compare the obtained results from each partial shading and PV faulty condition applied to the PV system. MATLAB/Simulink software is used to perform the simulation and the analysis for each examined PV array configuration.

Effective power transfer scheme for a grid connected hybrid wind/photovoltaic system

A new topology and effective power transfer scheme with minimum number of converters is proposed for a grid connected wind/photovoltaic (PV) system. Distributed generation sources considered are permanent magnet synchronous generator (PMSG)-based wind energy conversion system and PV array system. Two voltage source converters with a common DC-link serve as wind side converter (WSC) and grid side converter (GSC), respectively. The PV array is directly tied to the DC link without any power converter providing variable DC-link voltage. The Perturb and Observe technique extracts the maximum power from PV and the DC-link voltage is set to the maximum power point (MPP) voltage of the PV array. The output DC voltage of WSC is regulated to an MPP PV voltage using an outer proportional–integral voltage control loop. The maximum power from the PMSG and stator voltages is utilised to generate the reference currents for WSC to make stator currents to follow stator voltages. With unity power factor control, the overall VA of the WSC would contribute to the active power transfer and thereby reduce the kVA rating of the WSC in the proposed configuration. GSC tracks the maximum power from wind and PV array, and serves as a shunt active power filter to compensate for the current unbalance due to the connection of non-linear loads at the grid. All these functions are accomplished simultaneously. Various power transfer modes of operation are simulated through MATLAB/Simulink software and its results are validated through dSPACE Digital Signal Processor.

Fireworks Enriched P&O Algorithm for GMPPT and Detection of Partial Shading in PV Systems

Global maximum power point tracking (GMPPT) strategies for photovoltaic systems are effective under nonuniform irradiation conditions but cause unnecessary power loss due to wide search under uniform irradiance. This paper proposes a scheme for detecting the type of irradiation, viz., uniform or nonuniform, using the trend observed in the string maximum power point (MPP) voltage and current. This partial shading detection scheme is implemented in a GMPPT control strategy combining the conventional perturb and observe (P&O) algorithm and the Fireworks Algorithm (FWA). Under uniform irradiation conditions, the P&O algorithm is used owing to the lower magnitude of power oscillations during tracking as compared to the FWA. On the other hand, under partial shading conditions, the FWA is employed due to its global search and fast tracking capability. The proposed GMPPT method is tested experimentally to verify its effectiveness under different shading patterns.

A Novel Grid-Connected PV System Based on MMC to Get the Maximum Power Under Partial Shading Conditions

In the case of partial shading, the output power of the unshaded PV modules will be decreased by the influence of the shaded PV modules in one branch. In order to solve this problem, this paper proposes a novel topology for a PV power generation system by connecting a PV module to the capacitor in each submodule of a modular multilevel converter parallel. As partial shading occurs, the maximum power can be extracted by regulating the capacitor voltage to the maximum power point voltage. With this proposed topology, the maximum power tracking controller, the redundancy module controller, the voltage stability controller, and the grid-connected controller are studied. Simulation and experiment results show that comparing to the traditional topology, the proposed topology can greatly improve the output power of the PV system under the conditions of partial shading and features with low-voltage stress and high efficiency.

Monolithic CIGS–Perovskite Tandem Cell for Optimal Light Harvesting without Current Matching

We present a novel monolithic architecture for optimal light harvesting in multijunction thin film solar cells. In the configuration we consider, formed by a perovskite (PVK) cell overlying a CIGS cell, the current extracted from the two different junctions is decoupled by the insertion of a dielectric nonperiodic photonic multilayer structure. This photonic multilayer is designed by an inverse integration approach to confine the incident sunlight above the PVK band gap in the PVK absorber layer, while increasing the transparency for sunlight below the PVK band gap for an efficient coupling into the CIGS bottom cell. To match the maximum power point voltages in a parallel connection of the PVK and CIGS cells, the latter is divided into two subcells by means of a standard three-laser scribing connection. Using realistic parameters for all the layers in the multijunction architecture we predict power conversion efficiencies of 28%. This represents an improvement of 24% and 26% over the best CIGS and PVK sin...