The Resistance Comparison Method Using Integral Controller for Photovoltaic Emulator

Photovoltaic (PV) emulator (PVE) allows the development and testing of the PV equipment and system effectively. The PVE is an alternative to controllable light source that requires a large space and highly inefficient. The PVE requires a power converter and the buck converter is preferred due to the control simplicity and high efficiency. Nonetheless, the conventional design of the buck converter cannot be used since the output voltage of the PVE highly dependent on the output resistance. A proper design of the buck converter specified for the PVE application is needed to maintain continuous current mode operation and the output voltage ripple factor below the desired specification. This paper proposed the design for the passive components for the PVE using buck converter, which includes the output resistor, inductor, and capacitor. The single diode model is used to produce the current-resistance characteristic curves of the PV. The control strategy of the PVE is not included in this paper. The results show that the passive components for the buck converter obtained from the derivation able to maintain continuous current mode and has the output voltage ripple factor lower than the desired specification when operates as the PVE. This proves the derivation of the passive components is accurate.

With increasing solar photovoltaic-based power generation, a photovoltaic emulator (PVE) is necessary to experimentally validate new control strategies without the influence of external factors such as irradiance and temperature. However, two significant challenges with PVEs are (i) solving the nonlinear equation of photovoltaic (PV) panel and (ii) oscillations in constant current (voltage) region with voltage (current) control. Thus, in this paper, a PVE with the ability to mimic both uniformly irradiated and partially shaded PV panels is proposed by employing artificial neural network (ANN) and piecewise-linearization technique. Based on the input operating conditions (irradiance, temperature, and partial shading), the ANN breaks the nonlinear I-V curve into piecewise-linear segments and outputs their boundary points. Then, with these boundary points, piecewise-linear equations of the segments relating PVE’s voltage and current are formed. Subsequently, using these piecewise-linear equations, the reference PVE voltage corresponding to PVE’s output current is calculated and given to the PI controller of a synchronous buck converter to mimic a PV panel. Thus, the proposed PVE overcomes the problem of solving nonlinear I-V equation by piecewise linearization which in turn aids an impedance-matching technique to mitigate the aforementioned oscillations. The generation of training data and development of ANN were carried out in MATLAB. Finally, the simulation studies performed in MATLAB/Simulink and hardware experiments validated the steady-state accuracy and the transient response which settled within 10 ms endorsing the real-time application of the proposed PVE.

Photovoltaic (PV) sources are inherently nonlinear power devices and maximum power derivation depends on Maximum Power Point Tracking (MPPT) algorithms. The algorithms require testing in real time situation using PV source which will be troublesome due to higher dependency on environmental factors and larger space requirements for higher power rating. The increased and faster testing lead to develop a PV emulator with desired performance and lower price compare to the commercially available PV emulators. In this paper, design of a digitally controlled PV emulator with varying resistive load is proposed to replicate the behaviour of real PV sources. The power stage of the PV emulator is realized using dc-dc buck converter topology and the controller stage uses an algorithm-in-loop Newton-Raphson (NR) method. Finally, the PV emulator is tested with MPPT controlled dc-dc boost converter for battery charging. The design of the power and control stages of the PV emulator has been compared with the real PV source and it is observed that the obtained V-I characteristic is in good agreement. Moreover, an analysis is presented for different switching frequencies of the boost converter connected as load to the fixed switching frequency buck converter, i.e., PV emulator. Further, a schematic hardware circuit diagram has been given to realize the proposed digitally controlled PV emulator.

The photovoltaic (PV) technology has been increasingly used in our energy generation. Therefore, it is essential to have a good PV testing facility during the development process. The PV emulator (PVE) is a voltage or current source that mimic the current-voltage characteristic as a PV module that requires proper control strategy to work. The resistance feedback method (RFM) control strategy has many good attributes, except the transient response, which is caused by the proportional-integral (PI) controller. This paper proposed a new fuzzy logic PI (FLPI) controller to improve the transient performance of the RFM PVE. It is based on the error adjustment method that founded on the transient state and load of the PVE. The performance of the proposed PVE is compared with the original PVE that used RFM with the PI controller. The finding of the research shows that the transient performance of the proposed PVE has improved 2.3 times compared to the original PVE without affecting its accuracy.

A photovoltaic (PV) emulator replicates the exact I-V and P-V output characteristics of a PV module or array. This replication should have occurred in such a way the same output characteristics in different ambient conditions, including different temperature and irradiation levels, mismatching, or partial shading, have been obtained. In this paper, a PV emulator based on a DC-DC converter with a novel control method has been presented. The proposed controller is a fractional PI one optimized with Grasshopper Optimization Algorithm (GOA). It has one degree of freedom more than the conventional PI controller, which is the main advantage of this control approach. Also, a fractional-order lag compensator is used to decrease the output ripple of the converter. On the other hand, the Lambert W function models the PV characteristics which this modeling approach reduces computational burden and time. The simulation results in MATLAB/Simulink validate the performance of the proposed PV emulator.

Improved control strategy for photovoltaic emulator using resistance comparison method and binary search method

PV emulator (PVE) is a power supply that produces similar current‑voltage (I‑V) characteristic as the PV module. It simplifies the testing of the PV system during the development phase. Since the output voltage and current of the PVE change based on various factors (load, irradiance and temperature), the computation of the operating point for the PVE is crucial. The resistance feedback control strategy is a robust and fast approach to find the operating point for the PVE. Nonetheless, it uses an uncommon current‑resistance PV model, which cannot be computed using the conventional approach. This work introduces the reverse triangular number to compute the PV model and obtained the operating point of the PVE. The reverse triangular number is based on the variable step sizes that allow fast computation of the PV model. The operating point is then used by the PI controller and the buck converter to produce the output voltage and current similar to the PV module. The results show that the reverse triangular number is able to compute the PV model accurately. In addition, the proposed PVE not only works well with resistive load but adapts accurately under the integration with maximum power point tracking converter.

A photovoltaic (PV) module is an equipment that converts solar energy to electrical energy. A mathematical model should be presented to show the behavior of this device. The well-known single-diode and double-diode models are utilized to demonstrate the electrical behavior of the PV module. “Matlab/Simulink” is used to model and simulate the PV models because it is considered a major software for modeling, analyzing, and solving dynamic system real problems. In this work, a new modeling method based on the “Multiplexer and Functions blocks” in the "Matlab/Simulink Library" is presented. The mathematical analysis of single and double diodes is conducted on the basis of their equivalent circuits with simple modification. The corresponding equations are built in Matlab by using the proposed method. The unknown internal parameters of the PV panel circuit are extracted by using the PV array tool in Simulink, which is a simple method to obtain the PV parameters at certain weather conditions. Double-diode model results are compared with the single-diode model under various irradiances and temperatures to verify the performance and accuracy of the proposed method. The proposed method shows good agreement in terms of the I–V and P–V characteristics. A monocrystalline NST-120 W PV module is used to validate the proposed method. This module is connected to a variable load and tested for one summer day. The experimental voltage, current, and power are obtained under various irradiances and temperatures, and the I–V and P–V characteristics are obtained.

This paper presents the modeling, analysis and control of different DC-DC converter topologies to emulate the photovoltaic (PV) system. A PV emulator is basically a DC-DC converter having same electrical characteristics that of solar PV panel. The emulator helps to achieve real characteristics of PV system in a better way in an environment where using actual PV systems can produce inconsistent results due to variation in weather conditions. The paper describes different types of DC-DC converters like buck, Resonant and Quasi Resonant Converter. The complete system is modelled in MATLAB ® Simulink SimPowerSystem software package. The Simulation results obtained from the MATLAB ® Simulink SimPowerSystem software package for different topologies under steady and dynamic conditions are analyzed and presented. An evaluation table is also presented at the end of the paper, presenting the effectiveness of each topology.

Photovoltaic (PV) emulators are necessary tools for teaching research and development when actual PV panels cannot be used. Emulation can be used when design parameters such as size and quantity of PV resources required exceed the capacity of laboratories. Emulation schemes available today use expensive hardware and/or require software licenses. This paper presents a new PV emulator using the extremely low-cost real-time digital controller platform "Workbench". The proposed scheme uses low-cost hardware built around a single DSP and a DC bench power supply to emulate PV panels which can be used to test other equipment such as grid-tied inverters, and/or MPPT controllers. The proposed scheme is modular, in that multiple such emulators can be externally series/parallel connected. Each emulator can also be configured to emulate a combination of series/parallel connected PVs.

In this paper, the design and simulation of a photovoltaic (PV) emulator are presented. The output characteristic and I-V curve are produced based on mathematical engineering PV module, so that they are similar to the practical curves. The proposed system consists of a single-phase full-bridge PWM rectifier and a DC/DC buck converter, which can reduce the voltage ripple and improve the power factor near the grid. The rectifier uses double-loop control strategy and the buck circuit uses the formula of the PV module to control output voltage and load current. Using Matlab simulation, the result proves feasibility and good performance of this scheme, and simulation waves can reflect the change of temperature and light intensity.

This paper presents experimental analysis of Genetic Algorithms (GAs) based Maximum Power Point Tracking (MPPT) for photovoltaic (PV) systems. This method, presented by another paper [1], uses GAs to track the maximum power point (MPP) of PV panels. Comparison with the famous Perturb and Observe (P&O) and Incremental Conductance (Inc-Cond) are given, we tested stability (power oscillation) with real panels (Conergy PowerPlus 214P), to compare response time (rapidity) we used a PV emulator [2] so we can inject the same irradiance profile and see output PV power evolution. The response time, of P&O and Inc-Cond, and the PV power oscillation varies with the duty cycle increment step; with a small step, we get less power oscillation but this needs an important time response, we can improve system rapidity with a bigger duty increment step but important power oscillation will result. With GAs based MPPT we can get more stability with rapid response time. The results obtained show better stability and less oscillation around the MPP with the new method.

This paper presents the design, simulation, and experimental implementation of a photovoltaic (PV) emulator based on a buck converter controlled using the dynamic evolution control (DEC) technique. The proposed system accurately reproduces the nonlinear current-voltage (I-V) and power-voltage (P-V) characteristics of a commercial GREEN CELL SM100-18P (100 Wp) PV module under standard test conditions (1000 W/m2, 25 °C). The electrical characteristics of the reference module are embedded in the controller through a lookup table (LUT), which is integrated with the DEC algorithm to enable adaptive real-time regulation of output voltage and current. System modeling and validation are first conducted in MATLAB/Simulink to analyze steady-state and transient performance. A hardware prototype based on an XL4016 buck converter and Arduino Nano microcontroller is then implemented, with real-time monitoring provided via an ILI9341 TFT display. Experimental results show that the emulator achieves a maximum power deviation of 0.8%, a normalized root mean square error (RMSE) of 0.015, a settling time of approximately 12 ms, overshoot below 1.5%, voltage ripple under 2%, and peak conversion efficiency of 94% near the MPP region. These results confirm that the proposed PV emulator provides accurate static and dynamic reproduction of PV characteristics, offering a low-cost, stable, and repeatable platform for laboratory-scale evaluation of PV-related power electronic converters.

This article describes the design, control, and implementation of a photovoltaic (PV) emulator using two-switch forward-converter topology. The system is designed to emulate the nonlinear electrical behavior of an actual PV panel under different environmental conditions including radiation level and temperature. The emulator provides galvanic isolation and also accurate current modulation to provide a safe yet reliable means of testing PV-related devices and algorithms within a laboratory setting. A dual-loop PI control is proposed to adjust the output current according to voltage feedback (VF), thus making accurate I–V and P–V curves achievable. Besides software simulation, a tailored printed circuit board (PCB) was fabricated. The simulation result demonstrated that the system can achieve a fast response and stable operation, with a maximum error percentage of about 2.1%, indicating high emulation fidelity, thereby providing an attractive platform for various evaluation purposes such as MPPT algorithms, inverters, and EMS.

In this paper the modelling of the photovoltaic module has been applied through the experimental flash test data of industrial photovoltaic module. The theoretical background of the single diode model and the double diode model of the photovoltaic module have been described and similar procedures for the extraction and estimation of the unknown parameters have been proposed. The Levenberg-Marquardt optimization algorithm has been used to minimize objective function as a set of five nonlinear equations that were written for five equilibrium points on the current-voltage curve of the photovoltaic module. The single diode model and double diode model have then been simulated with the estimated unknown parameters and a very good matching between flash test data and a simulation data.