Maximum Power Point Voltage Research Articles

A Hybrid Method for Three-Level T-Type Inverters to Eliminate Neutral Point Voltage Ripple and Control DC-Link Capacitors’ Voltage for Separate MPPT

Nowadays, photovoltaic (PV) systems based on centralized topology with a three-level T-type (3LT2) inverter are used to decrease investment costs and increase conversion efficiency. In this topology, the split capacitors of the DC-link can individually connected to PV arrays. Accordingly, DC-link capacitors’ voltage should separately controlled to track PV arrays’ maximum power point (MPP) voltage. However, the asymmetric control of capacitors’ voltage causes line voltage to unbalance and output current to distort. In this paper, a hybrid method based on dipolar variable injection and zero-sequence voltage injection concepts is proposed to simultaneously control the DC-link capacitors’ voltage of the 3LT2 inverter and eliminate their voltages ripple. In the presence of partial shading, the proposed method can control the capacitors’ voltage of the DC-link to realize the separate MPP tracking while ensuring the balance of line voltages. Furthermore, the proposed method eliminates the voltage ripple on DC-link capacitors, inherently caused by the 3LT2 inverter, to improve the DC-link lifetime and the PV system reliability. The simulation studies and practical experiments have been performed, and their results prove the validity of the proposed method, whether the PF is unity or non-unity.

An Adaptive Model-Based MPPT Technique with Drift-Avoidance for Grid-Connected PV Systems

In this article, a modified control structure for a single-stage three phase grid-connected photovoltaic (PV) system is presented. In the proposed system, the maximum power point tracking (MPPT) function is developed using a new adaptive model-based technique, in which the maximum power point (MPP) voltage can be precisely located based on the characteristics of the PV source. By doing so, the drift problem associated with the traditional perturb and observe (P&O) technique can be easily solved. Moreover, the inverter control is accomplished using a predictive dead-beat function, which directly estimates the required reference voltages from the commanded reference currents. Then, the reference voltages are applied to a space vector pulse width modulator (SVPWM) for switching state generation. Furthermore, the proposed inverter control avoids the conventional and known cascaded loop structure of the voltage oriented control (VOC) method by elimination of the outer PI controller, and hence the overall control strategy is simplified. The proposed system is compared with different MPPT techniques, including the conventional P&O method and other techniques intended for drift avoidance. The evaluation of the suggested control methodology depends on various radiation profiles created in MATLAB. The proposed technique succeeds at capturing the maximum available power from the PV source with no drift in comparison with other methods.

Real-Time Implementation of CLMS Algorithm in 3P4W Solar PV-BES-Based Microgrid System

A solar photovoltaic (PV)—battery energy storage (BES) involved the microgrid (MG) system is presented in this article. It contains a bidirectional dc–dc converter (BDDC), which is responsible for extracting the maximum power output from the PV array by regulating the dc-link voltage to the maximum power point (MPP) voltage of the PV array. Whenever the PV array is not delivering any power, then the control of the BDDC is automatically shifted to regulate the dc-link voltage to a constant dc voltage. Thus, the BDDC regulates the dc-link voltage to the desired voltage in the presence of BES in the MG. Whenever the BES is disconnected from the MG, then the voltage source converter (VSC) regulates the dc-link voltage to the desired value. Thus, it enhances the reliability of the system. The neutral current compensation is performed by the zig-zag transformer, which is connected at the load end. The VSC performs different functions such as mitigation of harmonics and reactive power, balancing of grid currents, and the regulation of the dc-link voltage in the absence of BES. The system behavior is analyzed under different operating conditions in the simulation platform and in the laboratory conditions on a prototype.

Voltage Regulation of DC-Microgrid With PV and Battery

This paper studies voltage regulation and maximum power point tracking (MPPT) control for a DC-microgrid that includes a photovoltaic (PV) panel, battery, constant resistance and constant power loads. A dynamic model of the DC-microgrid system described by a multi-input and multi-output nonlinear system with non-affine inputs is derived. Based on this nonlinear dynamic model, we use output regulation theory to design a local state feedback controller that regulates voltages to prescribe set points and maximizes PV power output. Global set point regulation is also studied using passive system theory for non-affine systems and Lyapunov stability theory. The effectiveness of the proposed control schemes is investigated using simulations when changes in both illumination and load occur.

Desain dan Implementasi Algoritma Korelasi Daya dan Tegangan di Kapasitor untuk Maximum Power Point Trackking pada Photovoltaic Menggunakan Arduino Uno

Photovoltaic is a main device in solar power generation systems. The performance of this component needs to be improved to get the maximum power point. Many methods for maximizing power in photovoltaic have been developed and implemented in various algorithms. In fact, the algorithm has a lot of complexity and it requires a signal processing system that has a high speed and expensive one in the implementation. To overcome this problem, an algorithm based on power and voltage correlation inthe capacitors is developed to get maximum power. If the voltage across the capacitor is controlled according to the maximum power point voltage (VMPP), the maximum power (PMPP) value would be achieved. This concept is verified through computational simulations anda voltage control algorithm would be implemented using the Arduino Uno microcontroller for the final verification. The efficiency of the simulation is 99.88%–99.92% and an experimental is 92.84%–94.78%.

A novel fuzzy controller for photovoltaic pumping systems driven by general-purpose frequency converters

In this paper, a fuzzy logic based Mandani-type controller is applied to an industrial frequency converter to couple a photovoltaic generator to a conventional centrifugal pump for water pumping applications. The system operates in closed loop and the DC bus voltage regulation of the frequency converter is done indirectly by varying the speed of the pump according to the power provided by the photovoltaic generator. In order to decrease the number of series-connected modules, the working voltage of the photovoltaic generator (maximum power point voltage) must be as close as possible to the minimum voltage limit required by the frequency converter’s input. The proposed algorithm was embedded in a general-purpose microcontroller. Controller performance was evaluated through tests on an experimental bench that allows simulating different water heads. Experimental results shows that the speed of the proposed fuzzy controller allows the operation close to the lower DC voltage limit imposed by the frequency converter, making possible the use of photovoltaic generators with a reduced number of PV modules in series (in this work, 30% fewer modules). The fuzzy controller regulates the photovoltaic generator voltage throughout the day, avoiding frequency converter limitation due to undervoltage errors, even with sudden changes in irradiance.

DC-DC converter as a maximum power point voltage tracker.

In this paper, the maximum power point voltage tracker is designed and operated with the DC variable resistive load. The DC-DC converter technique is used for the design. The designed tracker operates as a DC-DC converter down. The designed tracker is a smart type; this is due to the use of programmed microcomputer to control the tracker circuits. The tracker contains three main circuits, sensing, drive and the power circuit. The designed tracker is constructed suitable to use with the photovoltaic power system (PVPS). The tracker is tested in the laboratory under different load levels at fixed insolation level.

Performance Enhancement by the Introduction of Additional Narrow Band Gap Bottom Layer of aSi0.64Ge0.36: H on Proposed p + aSi:H/i-aSi: H/n+ aSi0.73Ge0.27: H Thin Film Solar Cells

This work is the continuation of our previous work entitled "Investigations on optical, material and electrical properties of aSi:H and aSiGe:H in making proposed n+aSi:H/iaSi:H/p+aSiGe:H graded band gap solar cells." In this work, we present an additional bottom layer made of increased germanium content: aSi0.64Ge0.36:H to the previously recommended p+aSi:H/i-aSi:H/n+aSi0.73Ge0.27:H photovoltaic cell to strengthen the absorption spectrum and thereby boosting the attainment of the solar cell. Moreover, the overall active layer thickness is reduced from 430 nm of previous work to 395 nm of proposed work. This work includes the fabrication of samples of epitaxially grown aSiGe:H thin films of varying band gap made with Plasma Enhanced Chemical Vapour Deposition (PECVD) technique succeeded by their characterisation. The establishment of band gap tailoring by varying the germane (GeH4) gas flow rate is thoroughly investigated through optical characterisation. The growth chemistry of PECVD made aSi0.64Ge0.36:H layer has been analysed and the presence of respective radicals has been verified using Fourier Transform Infra Red (FTIR) spectroscopy. In accordance with the measured band gaps, p+ aSi:H/i-aSi:H/n+aSi0.73Ge0.27:H/naSi0.64Ge0.36:H solar cell has been proposed. A comprehensive inquiry on optimisation of the recommended structure has been made by varying the optical band gap and thickness of the bottom most aSi0.64Ge0.36:H layer of the structure. All the cell parameters including open circuit voltage (Voc), short circuit current density (Jsc), maximum power point voltage (Vm), maximum power point current density (Jm), Fill factor (FF) and conversion efficiency (η) has been calculated using SCAPS1D solar simulator. Furthermore, C–V characteristics and Mott-Schottky plot of the proposed structure has been evaluated. The introduction of narrow band gap amorphous silicon germanium (aSi0.64Ge0.36:H) at the bottom has remarkably enhanced Jsc and η to 15.54 mA/cm2 and 15.15% respectively, which is better compared to reported amorphous silicon photovoltaic cells having single junction.

A Novel Strategy of Maximum Power Point Tracking for Photovoltaic Panels Based on Fuzzy Logic Algorithm

From the perspective of renewable energy industry investment, absorbing maximum power from renewable sources is a vital factor. Hence, an algorithm is required to change the operating point of renewable energy sources in different environment conditions accordingly. This paper proposes a novel algorithm for tracking the Maximum Power Point (MPP) of a Photovoltaic (PV) panel. In this paper, an auxiliary parameter based on the voltage and power of the PV panel is suggested. By adopting this parameter, independence of irradiation and temperature, the interval between the operating point and the MPP can be estimated. Furthermore, the range of the MPP voltage variations is calculated with respect to various irradiations and temperatures. Then, a novel fuzzy logic Maximum Power Point Tracking (MPPT) algorithm is proposed based on the introduced parameter and voltage variations interval of the MPP. The proposed algorithm has appropriate respond to environment condition changes with proper speed and accuracy. In addition, unlike Hill Climbing (HC) and Perturb and Observe (P&O), the proposed method has no chattering in steady state. The abovementioned claims are successfully validated via the software MATLAB/Simulink.

An Improved Boost-Based dc/dc Converter With High-Voltage Step-Up Ratio for DC Microgrids

In this article, an improved ripple-free input current boost-based high step-up (HSU) dc/dc converter compared to the coupled inductor (CI) ones is proposed, where the large CI is replaced by an inductor and a built-in transformer. By doing so, the energy is transferred to the output by two smaller magnetic components. Hence, a more compact and more efficient coupled magnetic component with greater flexibility in increasing its turns ratio is succeeded, allowing us to achieve higher dc voltage gains (higher than 20). Additionally, an active clamp is employed to recycle the leakage energy of the transformer, eliminating at the same time the switching losses. Therefore, by increasing the switching frequency it is feasible to build a highly efficient, reduced-size HSU converter that can be integrated along with a low maximum power point voltage photovoltaic module for dc microgrid applications. Finally, a 250-W-rated prototype has been implemented to verify the functionality of the presented converter in continuous conduction mode operation with an input voltage range of 16-20 V and an output voltage of 400 V.

Solar PV-BES Based Microgrid System With Multifunctional VSC

A solar photovoltaic (PV)-battery energy storage-based microgrid with a multifunctional voltage source converter (VSC) is presented in this article. The maximum power extraction from a PV array, reactive power compensation, harmonics mitigation, balancing of grid currents and seamless transition from grid connected (GC) mode to standalone (SA) mode and vice versa, are performed in this system. Whenever the grid fails, this system operates in SA mode automatically, thereby without causing any interruption in supplying the load. Similarly, it automatically shifts to the GC mode, when the grid is restored. The VSC functions in current control for GC mode, and it operates in voltage control for SA mode of operation. This system is capable of extracting the maximum power from the solar PV array irrespective it is operating in the GC mode or SA mode. The charging and discharging of the battery are controlled by using a bidirectional dc–dc converter. It regulates the dc-link voltage to the maximum power point voltage of the PV array. If the absence of the battery is detected, then the control is automatically shifted to VSC for performing the extraction of the maximum power of the PV array.

Maximum Power Point Tracking and Voltage Regulation of Two-Stage Grid-Tied PV System Based on Model Predictive Control

This paper proposes a maximum power point tracking (MPPT) and voltage regulation method based on model predictive control (MPC) for the two-stage grid-tied photovoltaic (PV) system, which can achieve MPPT and output voltage regulation of a PV system simultaneously. The MPPT algorithm based on MPC is implemented in a DC-DC boost converter. The reference voltage at maximum power point is obtained by dual step Incremental Conductance (I&C) algorithm under the rapidly varying illumination intensity, and the MPPT controller only needs to minimize one cost function of PV current, without pulse width modulation (PWM) module. To inject the generated PV power into the grid with high quality, this paper designs voltage regulation controller based on MPC to maintain the output voltage of the PV system at the desired value. The MPC controller outputs the optimal duty signal with the input and state constraints in the inner loop, and the PI controller in the outer loop is designed to improve the dynamic performance. The proposed method based on MPC was demonstrated using the SimPower systems tool in MATLAB/Simulink. Analysis and simulation results for the PV system show possible improvements on the closed-loop performance such as fast response and low overshoot.

Research on Parameter Extraction Method of Photovoltaic Module Based on Improved Hybrid Algorithm

Correct extraction of the equivalent circuit model parameters of photovoltaic modules is of great significance for power prediction, fault diagnosis, and system optimization of photovoltaic power generation systems. Although there are many methods developed to extract the equivalent circuit model parameters of the photovoltaic module, it is still challenging to ensure the stability and operational efficiency of the extract method. In order to effectively extract the parameters of photovoltaic modules, this paper proposes a hybrid algorithm combining analytical methods and differential evolution algorithms for the extraction parameters of PV module. Firstly, the analytical method is applied to simplify the equivalent circuit model and improve the efficiency of the algorithm. Then, the adaptive algorithm is used to adjust the parameters of the differential evolution algorithm. Through the algorithm proposed in this paper, the parameters of the equivalent circuit model of the photovoltaic module can be extracted by the open-circuit voltage, short-circuit current, and maximum power point current and voltage provided by the manufacturer. The proposed method is applied to the extraction of the parameters of the dual-diode equivalent circuit model of different types of photovoltaic modules. The reliability and computational efficiency of the proposed algorithm are verified by comparison and analysis.

Multi‐input high step‐up inverter with soft‐switching capability, applicable in photovoltaic systems

In this study, a new multi-input high step-up inverter, based on isolated soft-switching DC-DC converter blocks is proposed. Each of these blocks can provide zero-voltage and zero-current switching for its semiconductors, which improve power efficiency. The interesting feature of this DC-DC converter is using bidirectional switches to generate both positive and negative output voltage levels in each DC-DC block with an appropriate control scheme. Each DC-DC converter operates by simple pulse width modulation control through fixed frequency and has two degrees of freedom, which provide the capability of output voltage regulation or maximum power point tracking. The proposed inverter consists of the cascaded connection of these DC-DC converters at their output terminal. This inverter can operate with high voltage gain, where the output voltage of each DC-DC converter is regulated. Furthermore, it can generate more output voltage levels with less number of DC-DC blocks. All these advantages make the proposed inverter suitable for photovoltaic power conditioning systems. In this study, the theoretical analysis with steady-state waveforms, design constraints, resonant tank analysis and comparison study are given. Then, experimental results of both the proposed inverter and its DC-DC blocks are presented.

A novel control strategy for mode seamless switching of PV converter in DC microgrid based on double integral sliding mode control

With the photovoltaic (PV) penetration increases in dc microgrid, the traditional PV converters with maximum power point tracking (MPPT) control, which are equivalent to current sources, can hardly meet the needs of coordinated operation. The PV converter should operate in both MPPT and constant voltage control (CVC) modes. When the operation mode changes, the PV converter needs to switch between current and voltage sources. Inevitably, the bus voltage instability would be caused. This paper presents a novel switching strategy for the smooth and seamless operation of the PV converter between MPPT and CVC modes. The PV converter under these two modes is always controlled as a voltage source, and its control variables are both the output voltage of PV arrays. When its operation mode changes from MPPT to CVC, a small offset signal based on DC bus voltage would be introduced to the reference voltage of inner loop of the PV converter, so as to shift the maximum power point (MPP) voltage. Meanwhile in the voltage inner loop, a double integral sliding mode controller (DISMC) is used to improve the performance and anti-interference ability of the PV converter. This method unifies MPPT and bus voltage adjustment strategy without any communication and changing any hardware structure and control parameters. When mode switching occurs, only the reference value of voltage inner loop would be slightly adjusted near the maximum photovoltaic power point, so the seamless transition for PV converter between the two modes can be ensured. Finally, the effectiveness of the mode seamless switching control strategy is demonstrated by the simulation and experimental tests.

A Bipolar-Input Thermoelectric Energy-Harvesting Interface With Boost/Flyback Hybrid Converter and On-Chip Cold Starter

This paper presents a bipolar-input thermoelectric energy-harvesting interface based on boost/flyback hybrid converter (BFHC). Two-type ring oscillators are combined to form as a complementary group with bipolar-input voltage operating range for self-start. With the technique of combining the boost converter and flyback converter together, the system is able to convert the energy with bipolar-input voltages. The open-circuit voltage maximum power point tracking (MPPT) method is adopted in this harvester to extract as much energy as possible from the thermoelectric generator. By dynamically adjusting the switching frequency according to the input power, the system achieves a high conversion efficiency with a wide input range. Implemented in 180-nm CMOS process, the harvester achieves a peak conversion efficiency of 84% at $V_{{\text {TEG}}}=260$ mV and 79% at $V_{{\text {TEG}}}=-300$ mV. In addition, the harvester can self-startup with minimum voltages of 129 mV with a positive input voltage and −140 mV with a negative input voltage.

Enhanced Lifetime and Photostability with Low-Temperature Mesoporous ZnTiO3 /Compact SnO2 Electrodes in Perovskite Solar Cells.

Perovskite solar cells (PSCs) with power conversion efficiencies (PCEs) of 25 % mainly have SnO2 or TiO2 as electron-transporting layers (ETLs). Now, zinc titanate (ZnTiO3 , ZTO) is proposed as mesoporous ETLs owing to its weak photo-effect, excellent carrier extraction, and transfer properties. Uniform mesoporous films were obtained by spinning coating the ZTO ink and annealed below 150 °C. Photovoltaic devices based on Cs0.05 FA0.81 MA0.14 PbI2.55 Br0.45 perovskite sandwiched between SnO2 -mesorporous ZTO electrode and Spiro-OMeTAD layer achieved the PCE of 20.5 %. The PSCs retained more than 95 % of their original efficiency after 100 days lifetime test without being encapsulated. Additionally, the PSCs retained over 95 % of the initial performance when subjected at the maximum power point voltage for 120 h under AM 1.5 G illumination (100 mW cm-2 ), demonstrating superior working stability. The application of ZTO provides a better choice for ETLs of PSCs.

Enhanced Lifetime and Photostability with Low‐Temperature Mesoporous ZnTiO3/Compact SnO2Electrodes in Perovskite Solar Cells

AbstractPerovskite solar cells (PSCs) with power conversion efficiencies (PCEs) of 25 % mainly have SnO2or TiO2as electron‐transporting layers (ETLs). Now, zinc titanate (ZnTiO3, ZTO) is proposed as mesoporous ETLs owing to its weak photo‐effect, excellent carrier extraction, and transfer properties. Uniform mesoporous films were obtained by spinning coating the ZTO ink and annealed below 150 °C. Photovoltaic devices based on Cs0.05FA0.81MA0.14PbI2.55Br0.45perovskite sandwiched between SnO2‐mesorporous ZTO electrode and Spiro‐OMeTAD layer achieved the PCE of 20.5 %. The PSCs retained more than 95 % of their original efficiency after 100 days lifetime test without being encapsulated. Additionally, the PSCs retained over 95 % of the initial performance when subjected at the maximum power point voltage for 120 h under AM 1.5 G illumination (100 mW cm−2), demonstrating superior working stability. The application of ZTO provides a better choice for ETLs of PSCs.

PWM Switched Capacitor-Based Cell-Level Power Balancing Converter Utilizing Diffusion Capacitance of Photovoltaic Cells

This paper proposes a novel pulsewidth modulation cell-level diffusion charge redistribution (DCR) converter based on a switched capacitor converter (SCC) utilizing diffusion capacitance of photovoltaic (PV) cells for PV modules under partial shading. Although a discrete inductor and capacitor are additionally necessary, Joule losses associated with switching operations can be reduced compared to the conventional capacitorless DCR converter. First, ac impedance measurement for a PV cell with 125 × 125 mm was performed, and the diffusion capacitance values were measured to be approximately 6.0 mF at its maximum power point voltage of 0.574 V. Second, the theoretical loss model was derived based on the detailed analysis, and it revealed that an optimal duty cycle achieving the lowest Joule loss was dependent on shading conditions. Third, a dual maximum power point tracking (MPPT) algorithm that controls duty cycles of not only the DCR converter, but a front-end boost converter is also proposed. With the dual MPPT control, the DPP converter operates at its optimal duty cycle to minimize the Joule loss while the boost converter seeks the MPP. The experimental results demonstrated that the maximum power significantly increased, thanks to the DCR converter, and that both the DCR and boost converters operated with respective optimal duty cycles.

Fluctuation of PV array global maximum power point voltage during irradiance transitions caused by clouds

In well-designed photovoltaic (PV) power plants, such as in typical utility-scale PV plants, operational conditions are quite stable and homogeneous apart from the fast irradiance transitions caused by cloud shadings. These partial shading events cause fast power fluctuations leading even to stability and quality problems in power networks. Fast non-homogeneous irradiance transitions cause also mismatch losses in PV generators and the occurrence of multiple maximum power points (MPPs), which appear in a wide voltage range of the PV generator. In consequence, the global MPP can fluctuate in a wide voltage region causing possible MPP tracking problems and power losses. This article presents a study of the behaviour of the global MPP voltage of various PV arrays during irradiance transitions caused by clouds. The global MPP voltage, its rate of change and the differences in voltage and available energy between the global MPP and the MPP with the highest voltage of the PV generators have been analysed comprehensively, for the first time, by using the characteristics of around 8000 measured irradiance transitions. The global MPP voltage was found to vary between 28 and 112% of the nominal MPP voltage of the array.