Distributed Maximum Power Point Tracking Research Articles

Cascaded Multi-Input Single-Output Boost Inverter for Mismatch Mitigation at PV Submodule Level

Mismatched power generation is a serious issue in PV systems, resulting from unequal power generation between PV components. Solutions have been proposed to reduce or eliminate the mismatch concern. One practical strategy is individually harvesting the maximum power from each PV component; the more distributed MPPT is applied to a finer level, the more power can be obtained. This study proposes three-input single-output boost converters that are employed to effectively increase PV power generation and significantly reduce mismatch issues between the PV submodule (PV SM). Each boost converter will be controlled to harvest the maximum power from a group of PV cells inside a single PV module. The outputs of the three boost converters are connected in series to provide higher output voltage for grid integration. The cascaded power converters are linked with a forwarding diode to provide a protection feature for the system and prevent the reverse current from harming the PV module. On the grid side, a single-phase Voltage Source Inverter (VSI) is used to convert the DC power from the PV module to sinusoidal AC power. The performance of the suggested inverter has been confirmed through experimental tests.

An Improved Distributed Maximum Power Point Tracking Technique in Photovoltaic Systems Based on Reinforcement Learning Algorithm

An Improved Distributed Maximum Power Point Tracking Technique in Photovoltaic Systems Based on Reinforcement Learning Algorithm

A Fast Reconfiguration Technique for Boost-Based DMPPT PV Systems Based on Deterministic Clustering Analysis

Mismatching operating conditions affect the energetic performance of PhotoVoltaic (PV) systems because they decrease their efficiency and reliability. The two different approaches used to overcome this problem are Distributed Maximum Power Point Tracking (DMPPT) architecture and reconfigurable PV array architecture. These techniques can be considered not only as alternatives but can be combined to reach better performance. To this aim, the present paper presents a new algorithm, based on the joint action of the DMPPT and reconfiguration approaches, applied to a reconfigurable Series-Parallel-Series architecture, which is suitable for domestic PV application. The core of the algorithm is a deterministic cluster analysis based on the shape of the current vs. voltage characteristic of a single PV module combined with its DC/DC converter to perform the DMPPT function. Experimental results are provided to validate the effectiveness of the proposed algorithm and to demonstrate evidence of its major advantages: robustness, simplicity of implementation and time-saving.

A Sizing Procedure for the DC-Side Capacitor of a Three-Phase Modular Multilevel Converter

The integration of photovoltaic (PV) modules with a modular multilevel converter (MMC) is very interesting because it allows us to exploit the intrinsic advantages of that converter, such as modularity and high voltage quality, and to implement distributed maximum power point tracking algorithms. The latter can appropriately be performed through controlling the circulating currents. In the literature, some control strategies for both the AC and DC circulating currents were proposed to manage the power mismatch among the legs and between the arms of the MMC. In a previous work, the authors proposed a novel control strategy for the circulating current components and inserted a capacitor on the DC side of a three-phase MMC with integrated PV panels. In the present work, it is shown how the correct sizing of this capacitor is essential to optimize the AC circulating voltages and minimize converter losses. A sizing procedure is proposed, deeply analyzed, and validated through numerical simulations.

A Comprehensive Review of Distributed MPPT for Grid-Tied PV Systems at the Sub-Module Level

Energy crises and the growth of the energy demand have increased the interest in utilizing unconventional power sources. Thus, renewable energy sources have become a topic of interest to mitigate rising energy concerns and cope with increased electricity demand. With remarkable merits including cleanness and abundance, photovoltaic (PV) solar energy systems are a key to solving these issues. The employed inverters should effectively utilize the maximum available power from the PV solar system and transfer this power to the utility grid without posing any further limitations. However, the unequal power generation of different PV systems caused by partial shading (PS) and other PV panel degradation factors leads to a reduction in generation capacity. One of the relatively new solutions to mitigate the mismatch concerns between the PV modules and sub-modules is to extract the maximum power of each sub-module individually. The main objective of this paper is to present a comprehensive review of such PV grid-connected inverters topologies associated with sub-module connection and control. It will classify the PV grid-tied inverters in accordance with the level where the maximum power point tracking (MPPT) system is implemented. A special focus has been placed on sub-module microinverters (MI) in terms of circuit topologies, conversion efficiency, and controller design. This paper provides a comprehensive analysis of employing the distributed MPPT (DMPPT) approach to maximize the power generation of PV systems by mitigating the mismatch issues inside the PV module. The circuit topology, PV system configuration, and MPPT algorithms used for applying DMPPT solutions in PV SMs are discussed in detail in this study.

Model predictive control for distributed MPPT algorithm of cascaded H-bridge multilevel grid-connected PV inverters

Abstract This paper concentrates on an algorithm with model predictive control for current and distributed MPPT for cascaded H-bridge multilevel photovoltaic (PV) inverter applications. In conventional method, in each sampling period, a discrete-time model is employed to predict the current future values for all vectors of voltage. The voltage vector will be approved if it minimizes the cost function. Because multilevel inverter has so many available voltage vectors, there is a large quantity of calculations, hence it makes difficult in implementing the normal control method. A varied control strategy that extensively decreases the calculations volume and eliminating common-mode voltage is proposed. To raise the PV modules performance and enlarge the systems power, a distributed maximum power point tracking (MPPT) control scheme for each phase of multilevel inverter is offered, that allows its DC-link voltage to be regulated separately. The recommended approach is double-checked by using a model simulated in MATLAB-Simulink software.

Modeling and Energy Generation Evaluations of Large-Scale Photovoltaic Plants Equipped With Panel-Level DC Optimizers

The distributed maximum power point tracking (DMPPT) technology, based on a DC optimizer (DCO, a DC/DC micro-converter) for each single photovoltaic (PV) panel, is one of the most popular solutions to mitigating the waste of solar energy when suffering mismatch conditions. However, the trade-off between the additional costs of deploying the panel-level power electronic equipment and the improved generation benefits of a large-scale PV plant (LPP) remains to be further studied. This study presents a static modeling method for the DCO-based distributed LPPs to study the long-term energy generation characteristics based on historical hourly weather data and then evaluate the economic benefits. The operational characteristics of the PV strings equipped with series-connected DCOs for three different topologies (Boost, Buck, and Buck-boost) are investigated, and then the control strategies for the PV-DCO generation units are proposed to maximize the energy generation of LPPs under frequent mismatch conditions. Different mismatch scenarios caused by the panel aging, geographical location settings, and the partial shading in PV arrays are simulated in the model. Six typical centralized or distributed PV plant configurations are carried out for comparison in case studies, to explore the generation characteristics and the advantages of energy production for the DCO-based distributed LPPs. Besides, the Levelized cost of energy (LCOE) which considers both the energy generation benefits and investment costs is introduced to the economic evaluation of different structures of LPPs.

MMC-Based PV Three-Phase System with Distributed MPPT

The use of distributed maximum power point tracking (DMPPT) algorithms is spreading because of their higher efficiency in the case of partial shading. The possibility of integrating photovoltaic (PV) modules in a modular multilevel converter (MMC) connected to the grid has been proposed in recent literature with the advantage of integrating DMPPT algorithms. In the case of partial shading, circulating currents control is necessary to extract the maximum available power and inject symmetric currents in the grid. Novel control strategies for both the ac and dc circulating current components of a three-phase MMC-based PV were proposed and analyzed in this work. Thanks to the presence of a capacitor connected to the dc-side of the MMC, the ac circulating currents could freely be controlled to extract the maximum power from all the PV modules in any irradiance condition while maintaining low power losses. Moreover, in contrast to previous works, instead of measuring the active power of legs and compensating for their imbalance using open-loop control, the power leg mismatches are compensated exploiting the dc loop currents generated through closed loop controls. The effectiveness of the proposed control strategy was proved by simulations performed using MATLAB Simulink.

Optimized generated power of a solar PV system using an intelligent tracking technique

<span lang="EN-US">Partial shading condition (PSC) is common and complicated in all types of PV power plant. Therefore, the power production of solar system would be affected by the mismatch phenomena produced by PSC. Furthermore, when the array is partially shaded, the P–V characteristics become more complex which causes multiple peaks of the P-V curve. So, the simple maximum power point tracking (MPPT) methods such as perturb and observe (P&O) will fail. To address the above issue, this paper proposes a combination of two different approaches, implementing distributed MPPT (DMPPT) and optimized fuzzy/bee algorithm (OFBA). DMPPT can be utilized to maximize solar energy by allowing each module, or group of modules, be managed independently. Also, due to the output power oscillations around the operating point in the P&O method, an OFBA is employed which allowing for the decrease of output power oscillations without the usage of temperature and light sensors. The result shows that utilizing of DMPPT control approach in conjunction with the OFBA boosts the output generated power.</span>

Fault-tolerant strategy without redundant switches for PV systems based on differential power processing converters

Considering the failure risk and cost-effectiveness of photovoltaic (PV) systems with high granularity maximum power point tracking (MPPT), a fault-tolerant strategy without redundant switches is proposed for the PV system based on differential power processing (DPP) converters. This fault-tolerant strategy optimizes the output power of the PV system under different converter fault conditions by adjusting the coordinated operation of the DPP converter and the centralized converter. Compared to previous methods, in the case of hardware cost advantage, the proposed fault-tolerant strategy achieves the stable operation of the PV system after the converter failure and completes the targeted power optimization of all PV modules. The PV system with the proposed fault-tolerant strategy operates in three modes: distributed MPPT (DMPPT) mode, the coexistence of DMPPT and centralized MPPT (CMPPT) mode, and CMPPT mode. The PV system operates in the DMPPT mode when no switch failure occurs in the DPP converter. In the latter two post-fault operating modes, this paper proposes a simple fault-tolerant method to remove the faulty DPP converter and adjust the MPPT coverage of the centralized converter to recover the power loss caused by the fault. The experimental results validate the proposed fault-tolerant strategy.

Buck-based DMPPT emulator: a helpful experimental demonstration unit

<span lang="EN-GB">Distributed control strategyrepresents the most promising solution to enhance the lackluster energetic performance of mismatched PhotoVoltaic (PV) systems. Moreover, many factors that contribute to such poor performance are still to be explored. To fully understand the advantages offered by the Distributed Maximum Power Point Tracking (DMPPT) approach, the implementation of a DMPPT emulator is necessary. Based on the above needs, this paper describes the realization and use of a Buck based DMPPT emulator and shows its high flexibility and potential. The realized device is capable to emulate the output current vs. voltage (I-V) characteristics of many commercial PV modules with a dedicated Buck DC/DC converter not only in controlled atmospheric conditions but also with different currents rating of the switching devices. The system implementation is based on a commercial power supply controlled by a low-cost Arduino board. Data acquisition is performed through a low-cost current and voltage sensor by using a multichannel board by National Instruments. Experimental results confirm the validity and potential of the proposed DMPPT emulator.</span>

Sliding-mode controller for a photovoltaic system based on a Cuk converter

The wide range of step-up and step-down input-output voltage characteristic of the Cuk converter makes it a good candidate to interface photovoltaic arrays in both classical and distributed maximum power point tracking systems. Because its two inductor structure, Cuk converters have continuous input and output currents, which reduce the additional filtering elements usually required for interfacing dc/dc converter topologies. However, PV systems based on Cuk converters usually do not provide formal proofs of global stability under realistic conditions, which makes impossible to ensure a safe operation of the PV installation. Therefore, this paper proposes a high performance sliding-mode controller for PV systems based on Cuk converters, which regulates the PV voltage in agreement with the commands imposed by a MPPT algorithm, rejecting both load and environmental perturbations, and ensuring global stability for real operation conditions. Finally, the performance of the regulated PV system is tested using both simulations and experiments.

Analysis, Design, and Implementation of a Differential Power Processing DMPPT With Multiple Buck–Boost Choppers for Photovoltaic Module

Submodule mismatch has become the major cause of losses in the photovoltaic (PV) power generation system, which has been an important factor restricting the development of PV technology. Differential power processing (DPP) architecture is increasingly employed in PV distributed MPPT (DMPPT) due to its low processed power. In order to improve the PV utilization efficiency, minimize the power loss and reduce the system cost, a novel scheme based on DPP is introduced in this article. The proposed DPP converter is composed of multiple buck-boost choppers, and a multidimensional perturb and observe (MPO) algorithm is proposed to achieve true DMPPT through correcting the voltage of each submodule to its voltage at the maximum power point by using a single current sensor. A prototype with multiple buck-boost choppers for 36 V/200 W PV module is designed and built to verify the operating principle and evaluate the performance of the proposed DPP converter and DMPPT strategy, and the experimental results show that the prototype is low-cost and effectively improves system efficiency.

An Effective Power Tracking Algorithm for Partially Shaded Solar PV Array Employing Micro Converters Feeding to DC Microgrid

This paper proposes the analysis of power enhancement in partially shaded PV system supplying DC microgrid employing micro converters with a modified Perturb and Observe (P & O) based on Maximum Power Point Tracking (MPPT) technique by sensing the load parameters alone. The proposed technique is effective in power tracking under both normal and partially shaded conditions with the reduced number of sensing devices as compared to those used in the conventional DMPPT (Distributed Maximum Power Point Tracking) techniques. In this work, two series configured micro converters are considered for supplying 120 V DC microgrid from partially shaded PV panels. The complete steady-state analysis is developed and predicted the performance of the proposed MPPT operation and compared with the simulation and experimental results. The PV panels are emulated in the experiments. The effectiveness of the proposed technique is demonstrated and substantiated by theoretical, simulation and experimental results under various operating conditions.

Multi‐input transformer‐less four‐wire microinverter with distributed MPPT for PV systems

SummaryThis paper proposes three‐phase microinverter able to process the power of three PV modules simultaneously and independently; thus, efficient utilization of PV modules through distributed maximum power point tracking (DMPPT) is realized. The proposed microinverter employs switched capacitors (SCs) networks combined with three‐phase voltage source inverter; it is named switched capacitor buck‐boost voltage source inverter and abbreviated as SC‐BBVSI. The connections of SCs networks are determined to fulfill the high boosting gain along with minimized leakage currents. In addition, low capacitances values can be employed for power decoupling purpose. Thus, in addition to DMPPT feature, three features of high boosting gain, high‐reliable product, and minimized leakage current are realized without using the bulky and costly isolation transformer. In this paper, the operation modes of SC‐BBVSI for single and multi‐input scenarios are explained. The modulation strategy to realize these modes along with the control system design is presented as well. The relations required to design the passive elements and identify the device's stresses are derived. The features of the proposed microinverter are confirmed through detailed comparison with other recently reported topologies. Both simulation and experimental results are provided to verify the features of the proposed topology.

DMPPT Control of Photovoltaic Microgrid Based on Improved Sparrow Search Algorithm

There are some problems in the photovoltaic microgrid system due to the solar irradiance-change environment, such as power fluctuation, which leads to larger power imbalance and affects the stable operation of the microgrid. Aiming at the problems of power mismatch loss under partial shading in photovoltaic microgrid systems, this paper proposed a distributed maximum power point tracking (DMPPT) approach based on an improved sparrow search algorithm (ISSA). First, used the center of gravity reverse learning mechanism to initialize the population, so that the population has a better spatial solution distribution; Secondly, the learning coefficient was introduced in the location update part of the discoverer to improve the global search ability of the algorithm; Simultaneously used the mutation operator to improve the position update of the joiner and avoid the algorithm falling into the local extreme value. The results of the model in Matlab showed that the ISSA can track the maximum power point(MPP) more accurately and quickly than the perturbation observation method (P&O) and the particle swarm optimization (PSO) algorithm, and had good steady-state performance.

Distributed SM MPPT Controller for Solar PV System Under Non-Uniform Atmospheric Conditions

This paper presents a diverse distributed maximum power point tracking (MPPT) method based on Cuk converter for solar photovoltaic system. The proposed MPPT method offers fast dynamic performance with absolute robustness by the concept of sliding mode control law to control the Cuk converter. The proposed configuration improves the dynamic response and reduces the ripple to considerable amount, resulting in their operation closer to maximum power point. Simulation is carried out to analyze the system behavior in response to varying atmospheric condition and the analytical results are also validated with simulation results.

Low cost ANN based MPPT for the mismatched PV modules

Due to manufacturing dispersal, the photovoltaic (PV) panels of similar rating and manufacturer have distinctive characteristics in practical. As the maximum power point tracking (MPPT) becomes essential to optimally utilize the solar PV panel, distributed maximum power point tracking (DMPPT) is considered in this paper to follow the MPP of each panel. As the common MPP value is used in the existing DMPPT method to control all the panels, it fails to consider the uniqueness of each panel. By considering the uniqueness of each panel, the ANN based MPPT is implemented in this paper. As the ANN is trained using the actual characteristics of each panel based on the operating current, voltage and temperature, it is able to track the actual MPP. Due to the solar irradiance free MPPT, the costly pyranometer is not required in the actual PV system for MPPT. It reduces the cost of the system and also provides the interruption free tracking due to its independent nature on Voc and Isc values. Also, because of the looping free behaviour of the proposed algorithm, it is capable of following the MPP at rapidly varying condition. The proposed technique and the verified outcomes are discussed here in detail.

An efficient multilevel interconnect control algorithm in AC/DC micro-grids using hybrid energy storage system

This paper presents a multilevel control method in two layers of micro-grids. Downstream grid (Battery-Converter Structure utilizing the distributed maximum power point tracking (DMPPT) for photovoltaic (PV) systems) and upstream grid (distributed generation (DG) sources with hybrid energy storage system (HESS)). In the downstream grid, each PV includes a DC/DC battery-converter with DMPPT. DMPPT converters can be used for voltage amplification and maintaining a constant PV voltage in the event of partial shading. To control the power and voltage in the upstream grid, hybrid energy storage systems (HESSs) distributed among AC/DC micro-grids are introduced. Each storage unit has two basic tasks. First, it controls the voltage of the node which as storage unit is connected (local node). Second, it controls the node identified as the global reference node on the grid. The output power of the HESS is controlled in such a way that the node voltage fluctuates in a predefined permissible range. This is due to fluctuations like load changes, reduced power of DGs or power constraints in DGs. To determine the power reference for each HESS, the state of charge (SoC) is considered matched to the dead-band droop control. Simulations were performed by MATLAB/Simulink.

Performance Improvement of PV-Fed Hybrid Modular Multilevel Converter Under Partial Shading Condition

This article presents a hybrid modular multilevel converter (HMMC) for large-scale photo voltaic (PV) integration to grid. PV panels are directly connected to each submodule of the converter without using any dc–dc converter. A distributed maximum power point tracking (D-MPPT) method is used to extract maximum power from each PV-string under normal, as well as, shading (uniform/nonuniform) condition. Power unbalance among the phases during partial shading is a major issue of such type of converter, which needs to be properly handled for satisfactory operation. To address this issue in a cascaded H-bridge converter, zero sequence voltage (ZSV) injection based methods have been utilized. In this work, ZSV injection is integrated with D-MPPT and the combined method is applied on HMMC to address both interphase and intraphase partial shading satisfying MPPT operation in each submodule. The feasibility of the proposed control method is first verified through PSCAD/EMTDC simulation. Thereafter, a dSPACE Micro-Lab-Box-based experimental prototype is developed to check the performance at 10 kW power level under the presence of real PV panels. A comparative assessment of the proposed system with available topologies has been performed to highlight the notable features. The capability of ZSV controlled HMMC is evaluated under various shading conditions to explore its usefulness to deal with power unbalance conditions. It may be predicted that an HMMC-based PV system with the aforesaid control methods has sufficient merits to become a potential candidate for high power PV integration.