Individual Maximum Power Point Tracking Research Articles

A Distributed Multimode Control Strategy for the Cascaded DC–DC Converter Applied to MVAC Grid-Tied PV System

The cascaded dc–dc converter is a popular topology for large-scale medium-voltage photovoltaic (PV) system with the advantages of high voltage conversion ratio, high efficiency, great flexibility, and independent control capability. However, the absence of optimal string maximum power point tracking (MPPT) operation under power mismatch is a big issue in common centralized control. Furthermore, the cost and time delay are unacceptable resulting from the distance among PV strings in the large-scale PV station and the cascaded dc–dc converter needs to adopt the distributed control method without real-time communication. To this end, by introducing other necessary constraints including voltage constraints, power constraints, and gain constraints on the basis of the distributed MPPT control strategy, a distributed multimode control scheme is proposed in this article. Each submodule (SM) can be switched flexibly between multiple operation modes to maximize the extracted solar energy. Individual string MPPT and autonomous distribution of output voltage are achieved without communication under the proposed distributed control strategy. In this way, optimal operation range is wider, mode switching is simpler, and applicability and robustness are improved. A downscaled prototype and a 35-kV/6-MW simulation system are constructed to verify the effectiveness of the proposed control strategy.

Passivity-Based Control of Single-Phase Cascaded H-Bridge Grid-Connected Photovoltaic Inverter

This article presents a nonlinear passivity-based control for a grid-connected cascaded H-bridge (CHB) photovoltaic (PV) system. The proposed control system is based on a port-controlled Hamiltonian model extracted from the synchronous reference frame system. Grid current dynamics is included in this model. Compared to existing solutions, the proposed control method has a robust performance and enhances the stability of the CHB-based PV system in the case of disturbances such as unequal irradiance over distinct PV arrays or a sudden sag or swell in the grid voltage. This controller also provides the independent control of each dc-link voltage. Therefore, the individual maximum power point tracking algorithms can be realized in each PV array, and the harvested energy can be maximized. Finally, simulation results and experimental investigations are conducted to verify the effectiveness of the proposed strategy.

Development of a Thermal Energy Harvesting Converter with Multiple Inputs and an Isolated Output

In this paper, an isolated multi-input single-output (MISO) converter is developed and applied to a thermoelectric energy conversion system to harvest thermal energy. The thermoelectric generators have individual maximum power point tracking functions. Furthermore, such a converter has a high step-up voltage conversion ratio. In addition, the presented converter is imposed on the thermoelectric energy conversion system with the three-point weighting strategy adopted to realize the maximum power point tracking (MPPT). In this paper, the basic principles of this converter are first described and analyzed, and finally some simulated and experimental results are offered to verify the feasibility and effectiveness of such a thermal energy harvesting system.

Implementation of adjustable variable step based backstepping control for the PV power plant

The most recent research challenge in sustainable photovoltaic (PV) energy is to maintain a high efficiency of PV arrays. Our contribution in this issue is reducing the power loss caused by environmental condition change and parametric variations. A non linear recursive Backstepping maximum power point tracking (MPPT) controller based on an adjusted variable step Perturb and Observe (P&O) algorithm (VS-Backstepping) is proposed to gather the maximum power with fast converge time from the PV system. The trade off between the high accuracy and the fast tracking speed cannot be realized through single MPPT techniques. Thus this work combines two individual MPPT controllers. However, the accuracy for finding the maximum power is highly related to the part of MPP tracking control using the Backstepping approach as well as the rapidity to reach the MPP is managed with the adjusted variable step P&O algorithm. To further evaluate the effectiveness of the proposed method (VS-Backstepping), simulation and experimental results on a commercial PV panel are presented and compared to an individual fixed step P&O algorithm and a variable step P&O (VS-P&O) controller.

Modelling & Simulation of PV Module Connected with Three-Port DC Converter

Of the world’s electricity is being generated through conventional sources of energy like coal and atomic energy. People have realized the dire effect of using these fuels, and the amount of CO2 being released into the environment. There has been a shift in emphasis towards cleaner ways of generating electricity in recent years. Solar energy is abundantly available and the cleanest renewable energy source available in the world and is ready to use for a variety of applications, such as the generation of electricity for residential, commercial, or industrial consumption and have become very competitive solutions. It can be seen that there is trend of solar photovoltaics (PV), which has seen rapid growth over the years. The increasing trend of adopting PV system allows consumers to be known as producers or “Prosumers”. This report evaluates how solar PV can be used in combination with a battery bank along with three port converter to fulfill the requirement. Power production from PV cannot be consistent due to factors like the weather although The main benefits of solar power are that it can be easily installed cost of generation is low as there is no requirement for fuel and require very little maintenance Distributed maximum power point tracking (MPPT) and autonomous are achieved with the proposed configuration. The input-port of each TPC is connected to an independent PV energy source to achieve individual MPPT, and the output-ports of these TPCs are connected with load. Fully modular design is achieved by using Simulink/matlab.

A Novel Combination Algorithm of Different Methods of Maximum Power Point Tracking for Grid-Connected Photovoltaic Systems

Abstract This paper proposes a novel algorithm to combine two or more techniques of maximum power point tracking (MPPT) to increase the output dc power and the efficiency of photovoltaic (PV) arrays. Different MPPT methods have dissimilar responses for the same environmental circumstances. The combination of multiple methods has the advantage of ever acquiring maximum power as the environmental conditions change. The proposed algorithm is used to enhance the selection of the most suitable duty cycle of the combined methods, based on the power-voltage characteristics, to get the best tracking response. Multiple classical and/or artificial intelligence (AI)-based MPPT methods can be combined based on this selection algorithm. To demonstrate its effectiveness, two examples are illustrated. The first one is the combination of two classical MPPT methods, which are the incremental conductance (INC) and the perturb-and-observe (P&O). The second example is to combine two AI-based MPPT, which are the artificial neural network (ANN) and the fuzzy logic control (FLC). The simulation results of the application of the proposed algorithm to a grid-connected PV system model justify its capability to acquire better static and dynamic responses than the responses of individual MPPT methods.

Design & Real-time Implementation of MIDO Converter Based PV Water Pumping System with BES

Background: Despite so many developments, most of the farmers in the rural areas are still dependent on rainwater, rivers or water wells, for irrigation, drinking water etc. The main reason behind such dependency is non-connectivity with the National grid and thus unavailability of electricity. To extract the maximum power from solar photovoltaic (SPV) based system, implementation of Maximum Power Point Tracking (MPPT) is mandatory. PV power is intermittent in nature. Variation in the irradiation level due to partial shading or mismatching phenomena leads to the development of modular DC-DC converters. Methods: A stand-alone Multi-Input Dual-Output (MIDO) DC-DC converter based SPV system, is installed at a farm; surrounded with plants for water pumping with stable flow (not pulsating) along with battery energy storage (BES) for lighting. The proposed work has two main objectives; first to maximize the available PV power under shadowing and mismatching condition in case of series/ parallel connected PV modules and second is to improve the utilization of available PV energy with dual loads connected to it. Implementation of proposed MIDO converter along with BES addresses these objectives. First, MIDO controller ensures the MPPT operation of the SPV system to extract maximum power even under partial shading condition and second, controls the power supplied to the motor-pump system and BES. The proposed system is simulated in MATLAB/ SIMULINK environment. Real-time experimental readings under natural sun irradiance through hardware set-up are also taken under dynamic field conditions to validate the performance. Results and Conclusion: The inherent advantage of individual MPPT of each PV source in MIDO configuration, under varying shadow patterns due to surrounding plants and trees is added to common DC bus and therefore provides a better impact on PV power extraction as compared to conventional PV based water pumping system. Multi-outputs at different supply voltages is another flag of MIDO system. Both these aspects are implemented and working successfully at 92.75% efficiency.

Performance analysis of solar PV based DC optimizer distributed system with simplified MPPT method

The proposed work focuses on the design and development of solar photovoltaic (PV) based DC optimizer distributed the system to enable individual maximum power point tracking (MPPT) in solar panels. This DC optimizer distributed system avoids mismatch losses and hot spots in solar PV panels during partial shadow conditions. A novel PI controller based fractional open circuit voltage MPPT method to extract the maximum power has been designed and discussed in this work. The entire system has been designed and modeled in MATLAB/Simulink and the same has been validated in hardware experimentation under varying environmental conditions. The results prove that the proposed system has fast voltage and current settling time with minimum oscillation and is cost-effective as it uses only a voltage sensor eliminating the use of the current sensor.

Current-Source Single-Phase Module Integrated Inverters for PV Grid-Connected Applications

This paper presents a modular grid-connected single-phase system based on series-connected current-source module integrated converters (MICs). The modular configuration improves the reliability, redundancy and scalability of photovoltaic (PV) distributed generators. In this system, each PV panel is connected to a dc/ac inverter to permit individual Maximum Power Point Tracking (MPPT) operation for each panel. Thus, the harvested power from the PV system will increase significantly. There are four different inverter topologies suitable to be used as MICs with different performances in terms of filtering elements size, power losses, efficiency, output voltage range, and high frequency transformers’ size. For the MPPT control, the oscillating even order harmonic components should be eliminated from the inverter’s input side otherwise the maximum power cannot be extracted. The proposed modulation scheme in this paper will ease the control of inverter’s input and output sides. Therefore, the 2nd order harmonic in the input current can be eliminated without adding new active semiconductor switches. A repetitive controller coupled with proportional-resonant controllers are employed to achieve accurate tracking for grid side as well as input side currents. Comparisons and performance evaluations for the proposed MICs are presented and validated with 1 kVA prototype controlled by TMS320F29335 DSP.

Fuzzy Logic Controller for Voltage and Frequency Stabilization in DC decoupled Micro grid system

An efficient Fuzzy Logic Controller (FLC) is proposed for maintaining constant voltage and frequency in a Decoupled DC micro grid system. The micro grid is modeled with solar, wind turbine, Fuel cell, battery and loads. Individual fuzzy MPPT (Maximum Power Point Tracking) controllers have proposed for solar, wind and fuel cell to extract maximum power from the sources and also to maintain constant voltage at DC bus. For the bidirectional power flow among the buses in the micro grid with power management strategy, an efficient Fuzzy logic controller is proposed for the bidirectional converter connected between DC and AC buses. The performance indices such as ITAE, ITSE, and settling time, rise time of DC link voltage has determined and it is being compared with the conventional Proportional Integral (PI) controller to endorse the performance of the proposed FLC. The results prove that the FLC has better performance in all aspects and it is more suitable for the power management in micro grid.

Elimination of Photovoltaic Mismatching With Improved Submodule Differential Power Processing

Differential power processing (DPP) is a promising architecture to solve the issue caused by mismatches among photovoltaic (PV) submodules. To eliminate the mismatch power losses, this paper presents an optimized PV-to-bus DPP system with submodule-level individual maximum power point tracking (MPPT) and module-level minimum-power tracking (MPT) simultaneous implementation according to the built mathematical model of the power processed by DPP converters with respect to the string current. Furthermore, a flexible time-sharing algorithm is adopted to reduce the number of MPPT units. Compared with other solutions, such as PV optimizer, the proposed scheme can reduce the effects of mismatches to the minimum regardless of mismatch conditions. The system cost is reduced since only one adaptive MPPT controller is required. Besides, the system efficiency is improved due to the true MPPT implementation and MPT control. Both simulation and experimental tests are provided to validate the effectiveness of the proposed scheme.

A Three-Port Converter Based Distributed DC Grid Connected PV System With Autonomous Output Voltage Sharing Control

A distributed dc grid connected photovoltaic (PV) generation configuration based on hybrid-connected three-port converters (TPCs) and its control strategy are proposed in this paper. Distributed maximum power point tracking (MPPT) and autonomous voltage sharing control are achieved with the proposed configuration and control strategy. The proposed system consists of multiple modular pulsewidth modulation plus phase-shift (PPS) controlled TPCs, which feature soft switching and low voltage stress. The input port of each TPC is connected to an independent PV energy source to achieve individual MPPT, and the output ports of these TPCs are connected in series to interface with a high-voltage (HV) dc bus, while the bidirectional ports are in parallel to build a low-voltage (LV) dc bus. The mismatch power of input sources can be transferred through the LV dc bus among these TPCs, and the power and voltage balancing at the HV output side can be realized. By regulating the voltage reference of a bidirectional port in a linear relationship with the output voltage, output voltage sharing is realized with only the module's own voltage and current being sensed. Fully modular design is achieved. System stability with the proposed control strategy is revealed by using the Routh–Hurwitz criterion. Simulation and experimental results are provided to verify the effectiveness and advantages of the proposed configuration and control strategy.

Feedforward Proportional Carrier-Based PWM for Cascaded H-Bridge PV Inverter

In this paper, a feedforward proportional carrier-based pulsewidth modulation (PWM) is proposed for the dc link control of the single-phase cascaded H-bridge multilevel photovoltaic inverter. The conventional carrier-based PWM techniques, such as the phase-shifted PWM and the level-shifted PWM, require multiple individual dc voltage controllers for the individual maximum power point tracking (MPPT). Thus, the control structure and the controllers’ designs are quite complex. Several noncarrier-based PWM techniques, such as the feedforward space vector modulation, the sorting-algorithm-based modulation, and the lookup table-based modulation, have the capability of individual dc voltage regulation. Although these noncarrier-based PWM techniques require only one total dc voltage controller in the outer voltage loop, the implementations of them are much more complicated than those of the carrier-based PWM techniques. In this paper, with the proposed feedforward proportional carrier-based PWM, each individual modulation signal is directly generated by multiplying the current loop controller’s output and the modulation signal’s feedforward proportional factor. With the feedforward PWM and the total dc voltage control, the individual dc voltage regulation is achieved. This carrier-based PWM combines the strengths of both the traditional carrier-based PWM and the noncarrier-based PWM. It is not only easy for implementation, but also requires only one total dc voltage controller in the outer voltage loop. The detailed description, derivation, and analysis of this modulation are included in this paper. In addition, the simulations and experiments demonstrate the performance of the dc link control and the individual MPPT using the proposed PWM and the control strategy.

Design and Analysis of RBFN-Based Single MPPT Controller for Hybrid Solar and Wind Energy System

In this paper, a radial basis function network-based single maximum power point tracking (MPPT) control algorithm for a hybrid solar and wind energy system is designed and analyzed for standalone and grid connected applications. The extraction of maximum power from the intermittent and erratic nature renewable energy sources is the main target in the hybrid renewable energy system. In the literature, many researchers developed an individual MPPT control algorithm for solar and wind energy system, which in turn increases the number of control algorithms in a hybrid system. In this paper, a single MPPT controller is proposed to extract maximum power from both the sources simultaneously. The performance of the proposed MPPT control algorithm is analyzed in both standalone and grid connected modes, under different weather conditions. The hybrid renewable energy system is designed by considering 560-W photovoltaic system and 500-W wind system with the conventional boost converter, and it is simulated in MATLAB/Simulink environment to analyze the performance of the proposed MPPT controller.

An algorithm for elimination of partial shading effect based on a Theory of Reference PV String

An innovative approach to the analysis of partial shading effect (PSE), in the case of PV string systems, is presented in the paper. In order to eliminate PSE and successfully achieve maximum PV string power under partial shading condition (PSC), a new theoretical concept, named ‘Theory of Reference PV String’, has been developed and applied to conventional approach, based on the usage of module integrated converters (MICs). The new maximum power point tracking (MPPT) control strategy proved to be efficient and less influenced by mutual interaction (MI) of individual MPPT algorithms, at PV module level. Simplicity of the conventional MPPT control strategy, based on string current control has been preserved and even improved. By using MATLAB/Simulink software package, the model of PV string with MICs has been created. Real-time PSE elimination system with algorithm based on the proposed MPPT control strategy has been introduced and tested. The most important testing results, based on several study cases, have been presented and considered. The proposed algorithm proved to be very efficient in achieving MPP under real-time variable irradiation condition. All advantages of the new algorithm have been verified through simulations.

Efficiency Improvement of Three-Phase Cascaded H-Bridge Multilevel Inverters for Photovoltaic Systems

Medium-scale photovoltaic (PV) systems using cascaded H-bridge multilevel inverters have a capability to perform individual maximum power point tracking (MPPT) for each PV panel or each small group of panels, resulting in minimization of both power losses from panel mismatch and effect of partial shading. They also provide high power quality, modularity, and possibility of eliminating dc-dc boost stage and line-frequency transformer. However, each PV panel in the system is subjected to a double-line-frequency voltage ripple at the dc-link which reduces the MPPT efficiency. This paper proposes a dc-link voltage ripple reduction by third-harmonic zero-sequence voltage injection for improving the MPPT efficiency. Moreover, a control method to achieve individual MPPT control of each inverter cell is also presented. The validity and effectiveness of the proposed methods were verified by computer simulation.

Analysis and Design of Grid-Connected Photovoltaic Systems With Multiple-Integrated Converters and a Pseudo-DC-Link Inverter

An architecture of multiple-integrated converter modules sharing an unfolding full-bridge inverter with a pseudo dc link (MIPs) is proposed for grid-connected photovoltaic systems in this paper. The proposed configuration can improve the power conversion, the control circuit complexity, and the cost competitiveness. The proposed MIP is composed of distributed flyback dc-dc converters (DFCs) and an unfolding full-bridge inverter with an ac filter. The DFCs can eliminate the shading effect by using the individual maximum power point tracking. In conventional flyback-type single-phase utility-interactive inverters, discontinuous conduction mode and boundary conduction mode are popular because of the inherent constant current-source characteristics more desirable for grid connection and of the simple procedures for the controller design. However, the operating mode suffers from a large current stress of the circuit components, which leads to the low power efficiency. To avoid this, the DFCs operate under continuous conduction mode that allows reduced current stresses and increased power efficiency, as well as low material cost. The current control loop of the converters employs primary-side regulation contributing to improvement of dynamics as well as the cost reduction significantly due to the elimination of the high-linearity photocoupler device. Development of a new dc-current loop that maintains the level of dc-current injection into the grid within the levels stipulated by IEEE 1547 will be dealt as well. The performance validation of the proposed design is confirmed by experimental results of a 200-W hardware prototype.

Individual Module Maximum Power Point Tracking for Thermoelectric Generator Systems

In a thermoelectric generator (TEG) system the DC/DC converter is under the control of a maximum power point tracker which ensures that the TEG system outputs the maximum possible power to the load. However, if the conditions, e.g., temperature, health, etc., of the TEG modules are different, each TEG module will not produce its maximum power. If each TEG module is controlled individually, each TEG module can be operated at its maximum power point and the TEG system output power will therefore be higher. In this work a power converter based on noninverting buck–boost converters capable of handling four TEG modules is presented. It is shown that, when each module in the TEG system is operated under individual maximum power point tracking, the system output power for this specific application can be increased by up to 8.4% relative to the situation when the modules are connected in series and 16.7% relative to the situation when the modules are connected in parallel.

Analytical study and evaluation results of power optimizers for distributed power conditioning in photovoltaic arrays

ABSTRACTThe use of modular or ‘micro’ maximum power point tracking (MPPT) converters at module level in series association, commercially known as “power optimizers”, allows the individual adaptation of each panel to the load, solving part of the problems related to partial shadows and different tilt and/or orientation angles of the photovoltaic (PV) modules. This is particularly relevant in building integrated PV systems. This paper presents useful behavioural analytical studies of cascade MPPT converters and evaluation test results of a prototype developed under a Spanish national research project. On the one hand, this work focuses on the development of new useful expressions which can be used to identify the behaviour of individual MPPT converters applied to each module and connected in series, in a typical grid‐connected PV system. On the other hand, a novel characterization method of MPPT converters is developed, and experimental results of the prototype are obtained: when individual partial shading is applied, and they are connected in a typical grid connected PV array. Copyright © 2011 John Wiley & Sons, Ltd.

Cascaded DC–DC Converter Photovoltaic Systems: Power Optimization Issues

This paper investigates the issues of ensuring global power optimization for cascaded dc-dc converter architectures of photovoltaic (PV) generators irrespective of the irradiance conditions. The global optimum of such connections of PV modules is generally equivalent with performing the maximum power point tracking (MPPT) on all the modules. The most important disturbance occurs when the irradiance levels of modules happen to be sensibly different from a module to another - in this case, voltage-limitation requirements may be broken. The proposed supervisory algorithm then attempts to establish the best suboptimal power regime. Validation has been achieved by MATLAB/Simulink numerical simulation in the case of a single-phase grid-connected PV system, where individual MPPTs have been implemented by an extremum-seeking control, a robust and less-knowledge-demanding perturb-and-observe method.