Array Maximum Power Point Research Articles

Simplified control algorithm for stable and efficient standalone PV systems: An assessment based on real climatic conditions

This research addresses the critical challenge of optimizing efficiency and performance in solar photovoltaic (PV) systems. It focuses on duty cycle optimization of DC/DC converters for maximum power point tracking (MPPT). The study introduces an innovative hybrid MPPT solution that integrates a novel temperature-based single-sensor approach with an integral backstepping controller. This method precisely achieves the PV array's maximum power point (MPP) under varying weather conditions while optimizing the converter's duty cycle to best align with the MPP voltage. Comprehensive simulations in MATLAB/Simulink reveal that the hybrid method surpasses conventional MPPT systems in key metrics, achieving faster convergence time (below 0.66 ms), reduced power ripple (<0.3 W), and enhanced tracking efficiency (exceeding 97.67 %). Notably, experimental data validates the practical efficacy of the proposed system under real-world conditions in the context of El Jadida, Morocco. This integrated approach advances the theoretical understanding of MPPT optimization and demonstrates tangible improvements in PV system performance, offering significant potential for enhancing solar energy utilization in variable climate regions.

Voltage Detection-Based Selective Harmonic Current Compensation Strategies for Photovoltaic Inverters

Voltage and current detection-based harmonic current compensation (VDB-HCC and CDB-HCC, respectively) strategies allow the use of photovoltaic (PV) inverters to enhance the grid power quality. CDB-HCC strategies require converter hardware retrofit by inserting an extra current sensor to measure load or downstream grid currents. On the other hand, VDB-HCC strategies are straightforward solutions employing only embedded measurements used for protection, control, and synchronization purposes. This paper provides a comprehensive comparison of three VDB-HCC strategies: VDB-HCC based on a single current loop (SCL); VDB-HCC based on dual parallel current control loops (DCL); and VDB-HCC based on parallel voltage and current control loops (VCL). The comparison includes the requirement of harmonic detection algorithms, PV array maximum power point tracking (MPPT) performance, stability over grid impedance variations and inverter power rating, steady-state harmonic compensation, enabling transient response, and computational burden. Experimental results using a 1.5-kW commercial PV inverter are conducted. Based on distributed HCC applications by PV systems, VCL has shown the best performance in terms of voltage distortion reduction under weak grids.

Design and control of LCL-type grid-tied PV power conditioning system based on inverter and grid side currents double feedback

ABSTRACT Solar energy as a limitless, clean, and cost-effective energy source could be converted to electrical power by photovoltaic cells. In this paper, a photovoltaic power conditioner, which is connected to the low voltage grid via an LCL filter, is presented. This power conditioning system supplies high-quality current and has high stability against disturbances. Since the generated PV voltage is lower than the grid voltage, a DC-DC converter is utilized. Also, DC voltage is also converted to AC by an LCL-type inverter. To ensure the resonance elimination yielded from the LCL filter, inverter and grid side currents, a double feedback strategy is employed. By considering resonance damping, stability margin, and the grid-connected requirements, a systematic design procedure for the suggested strategy is investigated to ensure the system stability in the low-voltage network. In comparison with the conventional strategies, the suggested strategy gives suitable resonance damping capability, higher marginal stability, and better grid-connected properties. Simulation results of the PV power conditioning system illustrate the accurate performance of the control system, suitable tracking of the PV array maximum power point, and high-quality current injection into the grid.

Power quality improvement of grid-connected photovoltaic systems using PI-fuzzy controller

To ensure enhanced reliability and availability of electricity to consumers, grid-connected photovoltaic systems need to improve their power quality, this paper uses a three-phase five levels cascaded H-bridge inverter in grid-connected mode to improve the flexibility and efficiency of the photovoltaic system. Each photovoltaic (PV) array in the proposed system has a maximum power point tracker (MPPT) to extract the PV array maximum power point for a particular irradiance and temperature and reduce the mismatch that causes an imbalance in the power sent from the inverter to the main grid. The fuzzy logic controller is used to tune the proportional-integral (PI) controller to regulate the current and voltage of the grid-connected inverter by changing the gain of the PI controller (Kp, Ki) to obtain a fast response and improve the power quality of the system despite different load disturbances and inputs. The system was simulated in MATLAB/Simulink, and the results show the superiority of the proposed control unit, in which a pure and stable sine output voltage and current waveforms. Finally, the total harmonic distortion (THD) is improved to reach 3.81% based on the fuzzy PI controller, while 7.77% is based on the PI controller.

Solar power-driven permanent magnet synchronous motor coupled with pump load: design, development and control

This paper presents design, development and control of solar photovoltaic (SPV) supply system for permanent magnet synchronous motor (PMSM) driven pump load. The proposed system is very effective in curtailing power demand on existing grid supply on highly dense population areas. An incremental conductance method followed by sliding mode control scheme is used to track SPV array maximum power point (MPP) and vary the speed of the PMSM accordingly under the change in atmospheric conditions. The direct torque control (DTC), voltage source inverter (VSI) is employed to control the PMSM speed and to achieve stable operating point. A prototype of single stage SPV supply-based PMSM coupled with DC machine is developed in laboratory for emulating the centrifugal pump characteristics. Performances under different environmental and operating conditions are obtained on the developed prototype to prove the efficacy of the proposed control.

Mismatch losses in a PV system due to shortened strings

Numerous events may require intentional removal of one or more photovoltaic modules from a string, shortening the length of the string relative to others within the array, resulting in a str ing length mismatch. The impact of such a mismatch is not well understood either in measurable operational effects (voltage, current, power) or in the potential effects on long-term module health. It is impractical to solely approach this problem experimentally due to the size and complexity of arrays that may experience string length shortening. This work presents simulations, validated through limited field experiments on a two string array, providing a basis from which more complex arrays and scenarios may be explored. Refinement of the simulation achieves an overall error in IMPP for the nominal (S1) and test strings (S2) between the simulation and experimental values, through all test conditions, of +0.35±1.46% and -0.36±1.58% respectively. Shortening one of two strings by one module results in a power loss greater than the power contribution of the module alone (1.29 module equivalents); the impact increases through the maximum test case of a six module mismatch with a power loss equivalent to more than 11 modules. The impact of using string-end blocking diodes is presented with an emphasis at the array maximum power point and at open circuit. Implications are discussed for arrays of higher complexity.

用于农业大棚的光伏阵列最大功率点跟踪算法研究

In order to enhance the utilization of solar energy in photovoltaic greenhouse, this paper takes the optimization strategy of photovoltaic array's maximum power point tracking algorithm as research object. According to the changing rule of the slope of photovoltaic array's output P-U curve, this paper proposes a new variable-step conductance increment method to track the maximum power point. When the working point is located on the left side of maximum power point, the logarithmic function value of curve’s slope is adopted as the voltage step to adjust the position of working point. When the working point is located on the right side of maximum power point, the exponential function value of curve’s slope is adopted as the voltage step to adjust the position of working point. Through the MPPT modelling and simulation in MATLAB/Simulink and the corresponding circuit test, the result shows that comparing with the traditional variable-step conductance increment method, the proposed algorithm can find the maximum power point faster, and it can effectively reduce the power loss caused by step oscillation in the searching process, which achieves the goal of enhancing conversion efficiency of photovoltaic power generation.

Effect of Partially Shaded Conditions on Photovoltaic Array's Maximum Power Point Tracking

Maximum power point tracking algorithm is widely implemented in photovoltaic system to maximize the PV array output power. In general, Perturb and Observe (P&O) is simple thus being selected to continuously track the array maximum power point (MPP). Under uniform solar irradiance, PV array characteristic is non-linear and consisting only one MPP along the functional operating voltage. However, when the PV array is partially shaded, the P-V characteristic becomes more complex with multiple MPPs. The occurrence of multiple MPP might cause the PV array to be trapped at the local MPP. At this operating condition of local MPP, PV array will generate lesser output power. In this study, the performance of PV array is explored especially when each PV module is at 30% and 70% shaded conditions. Simulation results show that PV array at absolute MPP can generate greater output power with the largest increased by 74.6% hence achieving higher power efficiency.

Photovoltaic Array Maximum Power Point Tracking Based on Improved Perturbation and Observation Method

The output characteristics of photovoltaic cells are strong non-linearity, and maximum power point tracking technology can improve the efficiency of photovoltaic systems. Based on improved perturbation and observation method, this paper takes the advantages of both long and small steps to realize the maximum power tracking of the photovoltaic system. Firstly, the absolute value of the real-time power rate of change is used as a reference for the automatic variable step size, and the maximum power is quickly tracked with a large step when the external conditions change. Then, after reaching the maximum power point, the system automatically becomes a small step to reduce the power oscillation loss. Finally, average calculation module is added to the power sampling to reduce the impact of clutter on the system and prevent the “sharp peak” of power. The results of the maximum power point tracking example show that the model has significantly improved the tracking speed of the maximum power point and the range of oscillation near the maximum power point.

Assessment of a proposed hybrid photovoltaic array maximum power point tracking method

Photovoltaic arrays have limited conversion efficiency and thus, a maximum power point tracking technique is essential. This makes the maximum power point tracking (MPPT) require prior prediction of the mentioned point in spite of the undeniable changes in the environment. In this manuscript an introduction and assessment of the different techniques of MPPT is presented. The categorization scheme of the MPPT techniques is according to either the predefinition of operating points without system data update (offline methods) or continuous sampling of system variables, to update the PV module measurements (online methods). Whereas hybrid method is a combination of both. A number of techniques from each class were simulated in MATLAB/Simulink environment in order to compare their performance. Moreover, the hybrid method was simulated in two successive steps without pre-assumption of the output of the offline method. The results demonstrated the relevance of the hybrid method when applied to a photovoltaic system due to its good performance, fast response and less fluctuations, when subjected to sudden climatic changes.

Photovoltaic Array Maximum Power Point Tracking Based on Improved Method

At present, a good deal of methods for the Maximum Power Point Tracking (MPPT) has been used in engineering applications. However, Matlab simulation proved that they were difficult to harmonize the stability and speed ability of system. In addition, in order to maximize the use of PV panels ‘power, the paper focused on aneonatalalgorithm for Maximum Power Point Tracking (MPPT). Based on the algorithm, this paper designed an improved and feasible variable step perturbation and observation method which well alleviated the conflict that the maximum power point tracking could not take into account the stability and speed of response efficiently.

Implementation of a modified incremental conductance MPPT algorithm with direct control based on a fuzzy duty cycle change estimator using dSPACE

Maximum power point tracking (MPPT) is a necessary function in all photovoltaic (PV) systems. The classic incremental conductance (IC) MPPT algorithm is widely used in the literature. However, when large changes occur in the irradiance, the performance of this algorithm is degraded. To eliminate all of the disadvantages of the classic IC algorithm, we developed a new IC controller based on a fuzzy duty cycle change estimator with direct control. A fuzzy logic estimator (FLE) is used to estimate the new duty cycle used to track the PV array maximum power point. Compared with the fixed step IC MPPT method with direct control, the proposed algorithm reaches the MPP more accurately and faster during dynamic and steady-state conditions. A controlled Cuk DC–DC converter was implemented and connected to a SunTech STP085B PV panel to verify the accuracy of the proposed method. Matlab/Simulink was used for the simulation studies. Additionally, the algorithms were digitally implemented on the dSPACE ACE1104 platform. The results obtained confirm the advantages of the proposed algorithm.

Passivity–Based Control of Photovoltaic Grid-Connected Inverter

Photovoltaic (PV) grid-connected system requires the inverter possesses excellent dynamic and static characteristics. In the view of the mathematical model of the inverter is nonlinear, we will adopt a kind of nonlinear control strategy called Passivity–Based Control (PBC). First we establish the standard Euler – Lagrange (EL) mode for inverter, then we also prove that this inverter is strictly passive. Based on passivity of inverter, we can redistribute the system energy, and adopt the approaches of injecting damping and decoupling to improve system performance. In this paper, we can control the active and reactive power of system to make system can fast track the PV array maximum power point, and possess the capacity of compensating the reactive power. Simulation results show that passivity-based control method can make the inverter possess better robustness and dynamic.

Implementation of photovoltaic array MPPT through fixed step predictive control technique

This paper proposes the implementation of Photovoltaic (PV) array Maximum Power Point Tracker (MPPT) through Fixed Step-Model Predictive Controller (FS MPC). The proposed controller scheme is based on the modified INcremental Conductance (INC) algorithm combined with the two-step horizon FS MPC. The current based INC algorithm is subject to major modifications in order to be capable of real time interaction between the MPPT and the controller obtaining sufficient information in one sampling time. The developed technique has been incorporated into a model for the overall simulation of the performance of a PV array for solar energy exploitation and is compared to the conventional approach under solar radiation variation improving PV system utilization efficiency and enabling to optimize system performance. This study also illustrates the effectiveness of the proposed controller scheme under various sky conditions with a simulation model employing real solar radiation data.

Novel Maximum-Power-Point Tracking Algorithm For Grid-Connected Photovoltaic System

This paper presents a novel maximum-power-point (MPP) tracking algorithm for photovoltaic (PV) energy conversion systems. The algorithm is based on utilizing the relation between the PV array MPP current and the solar insolation level at different atmospheric conditions. Also, a single-stage grid-connected PV system is proposed to track the MPP of the PV array, using the new algorithm, and to produce a sinusoidal output current in phase with the utility voltage (i.e., to obtain a unity power factor). The power stage of the proposed system includes, mainly, a direct current–alternate current inverter, whereas the control stage is based on utilizing both the Proportional Integral (PI) and the P resonant controllers. The obtained results satisfy the desired performance for the proposed system.

An intelligent maximum power point tracking method based on extension theory for PV systems

The purpose of this paper is to propose a novel maximum power point tracking (MPPT) technique to fully utilize photovoltaic (PV) array output power that depends on solar insolation and ambient temperature. The proposed intelligent MPPT algorithm based on extension theory can automatically adjust the step size to track the PV array maximum power point (MPP). Compared with the conventional fixed step size perturbation and observation (P&O) and incremental conductance (INC) methods, the presented approach is able to effectively improve the dynamic response and steady-state performance of the PV systems simultaneously. Theoretical analysis and the design principle of the proposed method are described in detail. Some simulations are performed to demonstrate the effectiveness of the proposed extension MPPT method.

A Variable Step Size INC MPPT Method for PV Systems

Maximum power point tracking (MPPT) techniques are employed in photovoltaic (PV) systems to make full utilization of PV array output power which depends on solar irradiation and ambient temperature. Among all the MPPT strategies, the incremental conductance (INC) algorithm is widely used due to the high tracking accuracy at steady state and good adaptability to the rapidly changing atmospheric conditions. In this paper, a modified variable step size INC MPPT algorithm is proposed, which automatically adjusts the step size to track the PV array maximum power point. Compared with the conventional fixed step size method, the proposed approach can effectively improve the MPPT speed and accuracy simultaneously. Furthermore, it is simple and can be easily implemented in digital signal processors. A theoretical analysis and the design principle of the proposed method are provided and its feasibility is also verified by simulation and experimental results.

Large-signal stability analysis of spacecraft power processing systems

The authors present a comprehensive large-signal stability analysis of a solar-array power system. The stability of the equilibrium points of a system with a typical nonlinear load characteristic is analyzed. Employing state-plane analysis techniques, the dynamic behavior of the system from an arbitrary initial condition is characterized, and the region of the desired stable operation is identified. The stability and transient response of the system operation near the solar array's maximum power point are evaluated. The dynamic response of the spacecraft power system operating in the shunt mode and battery-discharge mode is analyzed. >

Step-up maximum power point tracker for photovoltaic arrays

This paper discusses a new maximum power point tracker (MPPT), which has been devised and tested at the laboratory. This MPPT is a high-frequency set-up dc-to-dc power conditioning unit. Simple and inexpensive analog circuitry is used to continually maximize the true PV array output power rather than maximizing the current or voltage at either the PV array or load. The control circuit is designed such that the actual current and voltage are sensed directly from the PV array. These two signals are then multiplied by a single-chip multiplier. The multiplier output charges or discharges two separate RC circuits of different time constants. These two RC signals are then mixed to set the duty cycle of a pulse width modulated signal to continually track the array maximum power point. This MPPT is simple and inexpensive; and it continuously tracks the true PV array maximum power point regardless of the load type.