This paper addresses the need for cost-effective and integrated impedance spectroscopy (IS) techniques for supercapacitors (SCs), particularly in applications where conventional frequency response analyzers (FRAs) are impractical due to their high cost and lack of portability. A power converter-based methodology is proposed to perform IS using a power electronics interface, enabling in situ characterization of SCs. The approach is based on an analytical formulation that relates the amplitude of the duty-cycle perturbation introduced into the converter with the excitation frequency and the desired sinusoidal current amplitude, allowing the direct generation of frequency-dependent excitation signals using the power converter. The proposed methodology is first validated using circuital simulations, demonstrating accurate impedance estimation with a Range-Average Absolute Error (RAAE) of 0.30% in magnitude and 1.94% in phase compared with a reference simulation. Experimental validation is then conducted using a synchronous converter controlled by a digital signal processor, and those results are benchmarked against a commercial FRA, obtaining an experimental RAAE of 4.88% in magnitude and 2.41% in phase. These discrepancies are mainly attributed to limitations in the excitation and measurement stages. In addition to its accuracy, the proposed approach significantly reduces implementation cost. The converter-based setup relies on standard power electronics hardware and conventional laboratory instrumentation, with an estimated cost of approximately $2000 USD, which is much cheaper than commercial FRA-based systems (up to $60,000 USD). These results demonstrate that the proposed methodology provides a practical and scalable alternative for impedance spectroscopy of supercapacitors, enabling embedded and in situ diagnostics of energy storage systems.

Electrochemical Impedance Spectroscopy (EIS) is a widely adopted technique to diagnose degradations in devices such as batteries. Recently, its use has been proposed for photovoltaic (PV) panels through specialized devices such as the Frequency Response Analyzer (FRA); however, power converters can perform these functions, while regulating energy. Yet, the methodologies proposed in the state of the art do not detail the procedure, which makes difficult the reproduction of the results. This paper explains in detail how to perform EIS by using a power converter (PC). This approach provides a detailed analysis of the PC to obtain an equation for the amplitude of the converter duty cycle, to ensure a sinusoidal perturbation of the PV current with a fixed amplitude for any frequency. The proposed procedure is validated in PSIM software, which shows that the EIS obtained with the PC provides an RMSE of up to 0.0836 compared with the EIS obtained with the AC sweep tool of PSIM.

Impedance Spectroscopy (IS) is widely used to analyze the dynamic behavior and degradation of electrochemical systems such as batteries. IS has also been successfully applied to study the performance and degradation mechanisms of photovoltaic (PV) devices. Traditionally, IS is performed with Frequency Response Analyzers (FRA), which apply small-signal perturbations and measure the impedance response of the system. However, those instruments are costly and not suitable for in situ diagnostics. This work proposes a methodology to perform IS measurements on PV systems using a power converter, thereby eliminating the need for external specialized equipment. The proposed approach includes a theoretical analysis of the converter dynamics to derive an expression for the duty cycle amplitude, which is required to maintain a constant perturbation magnitude across a range of frequencies. The methodology is experimentally validated using a synchronous Boost converter connected to a PV panel and controlled by a Texas Instruments F28379D digital signal processor (DSP), which injects the perturbation signal in the converter’s duty cycle. Moreover, the voltage and current measurements are performed with an oscilloscope. The results demonstrate that the proposed converter-based IS method accurately reproduces the impedance spectra obtained with a commercial FRA, confirming its feasibility as a low-cost, flexible, and scalable solution for PV impedance characterization and diagnostics.

Current model-based methods for monitoring photovoltaic (PV) modules typically rely on the single-diode model (SDM) or its variants, assuming uniform operating conditions across the module. However, these ideal conditions are difficult to realize in real-world applications due to partial shading, soiling, degradation, and other phenomena. This paper proposes a 7-parameter self-adapting Double SDM model (D-SDM) to enhance the accuracy and reliability of parameter identification in PV modules under real operating conditions. A robust methodology based on evolutionary algorithms is proposed to estimate the parameters of the D-SDM, directly from the I-V characteristic of a PV module, applicable in both uniform and mismatched scenarios. The proposed methodology also includes a robust fitting error calculation that only considers the section of the I-V curve where all the cells operate with positive voltage. The methodology is validated using experimental and simulated I-V curves across various mismatching patterns, demonstrating the superior stability and reliability of the proposed method, which can be used for PV system monitoring and diagnosis in complex conditions.

Impedance spectroscopy has recently emerged as a promising diagnostic tool for monitoring and assessing the health status of photovoltaic modules, particularly in the context of performance optimization and degradation analysis. Directly derived from the Electrochemical Impedance Spectroscopy widely used for characterization of electrochemical systems, its application to PV modules under real operating conditions remains challenging due to the technique's sensitivity to the intrinsic variability of irradiance and temperature during outdoor testing. This paper investigates the use of impedance spectroscopy on bifacial photovoltaic modules operating outdoor. The study presents the impedance spectra of bifacial photovoltaic modules operating at different configurations, irradiance values and biasing points. In particular, this work investigates the relationship between the impedance spectrum and the irradiance on both the front and rear sides of the bifacial photovoltaic module, and simultaneously provides reference data for real-time monitoring techniques and advanced diagnostic strategies for bifacial photovoltaic modules.

This paper presents a single-phase Full-Bridge (FB) inverter with a hybrid commutation technique designed to reduce the harmonic distortion caused by the loss of the controller capability around the zero-crossing point in the unipolar commutation region. The hybrid modulation changes from unipolar to bipolar commutation under the loss of the reference control, improving the robustness and efficiency of the method. The commutation technique improves the switching performance and reduces the switching losses. Simulation models are developed in MATLAB/Simulink R2023b to evaluate their performance under different operating conditions. The results show that the proposed commutation technique can achieve high efficiency, low total harmonic distortion (THD), and fast dynamic response. The experimental implementation of sliding mode control (SMC) implemented in an STM32 microcontroller confirms that the hybrid commutation technique can reduce the THD by 0.96 percentage points for local (off-grid) loads and up to 2.45 in an industrial grid-tie network, compared with unipolar commutation. These findings highlight the potential of the proposed modulation technique for applications like solar panels and offer crucial insights for ongoing research and development in this field.

Los sistemas fotovoltaicos (FV) son ampliamente usados en entornos urbanos para producir electricidad. Esas instalaciones FV se diseñan para aprovechar espacios no usados como techos, donde se tienen otros dispositivos instalados (antenas, chimeneas, etc.), por lo que el espacio disponible no es regular. Por lo tanto, se debe diseñar un modelo matemático que tenga en cuenta esas irregularidades en la instalación FV. Este artículo introduce un nuevo modelo para ese tipo de instalaciones PV irregulares, el cual usa una formulación implícita de la característica corriente-voltaje de los módulos, permitiendo de esta forma evitar el uso de cálculos complejos como la función Lambert-W, lo que reduce el tiempo de cálculo. El modelo se basa en un sistema de ecuaciones formulado a partir de las relaciones circuitales de la estructura cruzada, la cual es una candidata ideal para instalaciones FV irregulares. Finalmente, el modelo se valida usando una instalación FV realista, la cual está basada en módulos FV comerciales.

Dynamic reconfiguration, the monitoring of power production, and the fault diagnosis of photovoltaic arrays, among other applications, require fast and accurate models of photovoltaic arrays. In the literature, some models use the Lambert-W function to represent each module of the array, which increases the calculation time. Other models that use implicit equations to avoid the Lambert-W function do not use the inflection voltages to simplify the system of nonlinear equations that represent the array, increasing the computational burden. Therefore, this paper proposes mathematical models for series-parallel (SP) and total-cross-tied (TCT) photovoltaic arrays based on the implicit equations of the single-diode model and the inflection points of the current–voltage curves. These models decrease the calculation time by reducing the complexity of the nonlinear equation systems that represent each string of SP arrays and the whole TCT. Consequently, the calculation process that solves the model speeds up in comparison with processes that solve traditional explicit models based on the Lambert-W function. The results of several simulation scenarios using the proposed SP model with different array sizes show a reduction in the computation time by 82.97% in contrast with the traditional solution. Additionally, when the proposed TCT model for arrays larger than 2×2 is used, the reduction in the computation time is between 47.71% and 92.28%. In dynamic reconfiguration, the results demonstrate that the proposed SP model provides the same optimal configuration but 7 times faster than traditional solutions, and the TCT model is solved at least 4 times faster than classical solutions.

Low-voltage photovoltaic systems are being widely used around the world, including their introduction into the power grid. The development of these systems requires the adaptation of several power converters, their static and dynamic modeling, the design of passive elements, and the design of the controller parameters, among other actions. Today, power converters are key elements in the development of photovoltaic systems, and classical power converters such as buck converters produce discontinuous input and output currents, requiring a high input capacitance and impacting the output power quality of these systems. This paper presents a proposal for a low-voltage photovoltaic system that uses a continuous input/output current buck converter, which enhances the operation of the classical buck converter in photovoltaic systems. The methodology describes the proposed photovoltaic system, including the power converter, its detailed operation, and the analysis of its waveforms. Moreover, the methodology includes a mathematical model of the photovoltaic system’s dynamic behavior and the design of a sliding-mode controller for maximum power extraction and perturbation rejection. The photovoltaic system is validated in two ways: first, a comparison with the classical buck converter highlighting the advantages of continuous input/output currents is presented; then, an application example using commercial devices is described in detail. The application example uses a flowchart to design the power converter and the sliding-mode controller, and a circuit simulation confirms the advantages of the continuous input/output current buck converter with its controller. In the circuit simulation, the control strategy is formed by a perturb and observe algorithm that generates the voltage reference for the sliding-mode controller, which guarantees the system stability, tracks the maximum power point, and rejects the double-frequency oscillations generated by an intended microinverter.

This paper presents an overview and critical discussion about the utilization of power converters in several microgrid configurations that incorporate non-conventional renewable energy sources and energy storage. The methodology is developed over 69 works published in this research topic. The papers are selected from databases in electrical engineering, e.g., IEEExplore, ScienceDirect, Springer, MDPI, etc. Then, the papers are classified depending on its focus, i.e., power converters in microgrids or power converters in distribution systems. At least, three classifications are proposed and one of them is made over more than 40 papers about power converters used in microgrids and electric distribution systems. Given the wide variety of microgrids and their configurations, the selection of appropriate power converters for every scenario is not trivial; therefore, this work also classifies the converters in their most common application, their advantages and disadvantages, and also point out the study domain, i.e., simulation or physical implementation. One of the main conclusions made from the overview is a gap identified in the study of direct current/ direct current microgrids despite being the simplest configuration among the three analyzed configurations. This is because hybrid and alternate current microgrids are more widely used since they allow taking advantage of the infrastructure of the current electrical systems.

DC microgrids are composed of loads, renewable sources, and storage devices that require control and protection to operate safely. The flyback converter is an alternative to connect paralleled batteries with nominal voltage DC buses; however, until now, complex controllers have been proposed, making difficult their implementation. On the other hand, when the voltage of a DC microgrid is not properly controlled, the loads may be damaged due to the voltage outside of the safe range. Therefore, proposed in this paper are two adaptive PI-structures to control a battery charger based on a flyback converter to be used in DC microgrids. The first adaptive current controller regulates the magnetizing current for stabilizing the system, and the second adaptive voltage controller regulates the voltage of the DC bus to protect the elements of the microgrid. The methodology to design the adaptive parameters of the PI-structures is developed as follows: first, the power stage of the flyback converter is introduced to derive a control-oriented model. The battery and the DC bus of the microgrid, which are interfaced by the flyback converter, are represented with widely accepted approaches. The second step is focused on modeling the system. The flyback converter, which includes a capacitance to model the DC microgrid, is represented by a dynamic model. The differential equations are averaged, and several transfer functions of the main variables are obtained. In the third step, the transfer functions are used to design the PI adaptive current controller and the PI adaptive voltage controller. In the last step, several recommendations are made to implement the power and control stages in low-cost hardware. An application example with realistic parameters is carried out in PSIM to validate the controller loops design. A battery of 12 V is connected to a DC microgrid of 48 V through a flyback converter with a switching frequency of 50 kHz. The settling time and deviation of the DC microgrid voltage, after a perturbation, are 0.845 ms and 2.04 V respectively, while the maximum values are adjusted to be 1 ms and 2.4 V. The simulation results validate the proposed procedure and the effectiveness of the PI-structures in regulating the magnetizing current and the DC bus voltage.

Photovoltaic (PV) systems require bypass diodes to protect PV modules from operating at negative voltages, thus avoiding the degradation of a PV array under partial-shading conditions. However, the presence of bypass diodes produces changes in the power production of the PV array; thus, an accurate bypass diode model is essential to estimate the power production of the PV array, which is required to analyze the viability of a PV installation. Therefore, this paper proposes a modified model for the bypass diodes present in commercial PV arrays; such a proposed model is based on the Schottky equation, including a series resistance. This paper also proposes a non-invasive and non-destructive method for estimating the model parameters, which avoids the requirement of opening the module junction box; thus, it applies to commercial PV arrays. Simulation and experimental results confirm the improved accuracy of the proposed solution over the classical bypass diode model usually adopted for estimating the power production of PV arrays.

This paper presents a methodology used to estimate the energy generated during one year by a photovoltaic module (PVM) operating under partial shading conditions. The methodology starts by calculating the solar paths and contours of nearby objects that produce shadows. Then, a method was proposed to estimate the shading factors of each submodule. Afterwards, the solar resource data and the calculated shading factors were used to feed a detailed PVM model to calculate the power–voltage curves for each hour, which were used to obtain a power profile and estimate the energy generated by the PVM in one year. The procedure was validated through simulation and experimental results. The simulation results consider a case study available in the literature, which was simulated to evaluate the effect on the PVM energy estimation considering and disregarding the partial shading conditions. The experimental results illustrate the capacity of the proposed methodology to predict the shaded and unshaded submodules and the module power–voltage curve. The results show that the proposed method avoids the energy overestimation introduced by classical estimation methods, which affects the sizing of a photovoltaic generator.

A method to design a sliding-mode control of a photovoltaic system based on a flyback converter is proposed. First, the photovoltaic system is modeled to design the sliding-mode controller and to select the parameters of a maximum power point tracking algorithm. Then, the detailed design of the sliding-mode controller is presented, which includes the establishment of the sliding surface. The transversality, reachability, and equivalent control tests are also developed. Because the power extraction of the PV system is carried out through a P&O MPPT algorithm, the selection of the perturbation magnitude, the perturbation period, and the maximum switching frequency is integrated into the control design. Additionally, since the derivative of the MPPT output could prevent the achievement of the reachability test, a filter to limit that derivative is also integrated into the design process. The whole method is illustrated in an application example where the data of a BP585 PV module and a real flyback converter are used. Once the parameters were obtained, circuital simulations performed in PSIM validated the intended operation of a PV system composed of a PV module and a flyback converter, which is connected to a source that produces the perturbations of an AC grid.

Rectifiers with power factor correction are key devices to supply DC loads from AC sources, guaranteeing a power factor close to one and low total harmonic distortion. Boost-based power factor correction rectifiers are the most widely used topology and they are formed by a power stage (diode bridge and Boost converter) and a control system. However, there is a relevant control problem, because controllers are designed with linearized models of the converters for a specific operating point; consequently, the required dynamic performance and stability of the whole system for different operating points are not guaranteed. Another weak and common practice is to design the power and control stages independently. This paper proposes a co-design procedure for both the power stage and the control system of a Boost-based PFC rectifier, which is focused on guaranteeing the system's stability in any operating conditions. Moreover, the design procedure assures a maximum switching frequency and the fulfillment of different design requirements for the output voltage: maximum overshoot and settling time before load disturbances, maximum ripple, and the desired damping ratio. The proposed control has a cascade structure, where the inner loop is a sliding-mode controller (SMC) to track the inductor current reference, and the outer loop is an adaptive PI regulator of the output voltage, which manipulates the amplitude of the inductor current reference. The paper includes the stability analysis of the SMC, the design procedure of the inductor to guarantee the system stability, and the design of the adaptive PI controller parameters and the capacitor to achieve the desired dynamic performance of the output voltage. The proposed rectifier is simulated in PSIM and the results validate the co-design procedures and show that the proposed system is stable for any operating conditions and satisfies the design requirements.

The energy consumption estimation of a locomotive for a particular route is important for the selection of a locomotive technology, the improvement of the energy management system, the evaluation of the locomotive’s potential energy generation, among others. The methodologies reported in the literature usually assume that the information of the railway track is available; however, in some cases, the track information is incomplete, not available, or the route is still in a planning stage. Therefore, this paper proposes a methodology to estimate the energy consumption and the potential energy generation of a locomotive when the railway track information is not available or incomplete. The methodology begins by extracting the main technical information of the locomotive to be analyzed. Then, the route is traced on Google Earth with steps of 100 m and the obtained information is processed to generate the longitude, latitude, elevation, and distance of the points along the route. From such information, it is possible to generate the slope and curvature profiles, while the speed profile can be obtained from the track operator or the regulations of a specific country. With that information, it is possible to estimate the equivalent power of the locomotive at each point of the route to finally calculate the consumed energy. The proposed methodology is validated with two case studies. The first one compares the results with a methodology available in the literature for the same route and locomotive, while the second case shows the applicability of the proposed methodology for a route without information.

Potential-induced degradation (PID) in photovoltaic (PV) solar panels occurs due to the operation in strings that are part of large installations, and under determinate voltage and environmental operating conditions, especially humidity and temperature. The PID can cause decreasing of up to 40 % in the generated power capacity of the PV panel and, in the most severe cases, the end of its lifetime. When this phenomenon is detected in time, the causes can be corrected and, the effect on the PV panels could be susceptible to a reversibility process. This article presents a comparative analysis of the performance of four electrical indicators to detect PID reported in recent literature. This study is carried out by simulation, using the single-diode model to represent the PV panel, and under different irradiance and temperature conditions. The results show the advantages of an indicator based on normalized parallel resistance, in terms of its practicality and low sensitivity to changes in irradiance and temperature conditions.

Energy storage systems are essential for multiple applications like renewable energy systems, electric vehicles, microgrids, among others. Those systems are responsible of regulating the dc bus voltage using charging-discharging systems which are mainly formed by a power converter and a control system. This work focuses on the control system of a flyback converter. A detailed design procedure of an adaptive sliding-mode controller (SMC) and its parameters is presented. The proposed procedure was validated through simulations which allow to confirm its good performance in terms of global stability providing the desired dynamic of the dc bus voltage regulation.

Micro-inverters have attracted the attention in photovoltaic (PV) systems because they mitigate the effects of partial shading. A micro-inverter can be implemented with two-stages: DC-DC step-up conversion and DC-AC conversion (inverter). Resonant converters present high potential for the first stage due to their high voltage gain, efficiency, and switching frequency. These characteristics allows a small footprint and low switching losses due to possibility of zero-voltage-switching (ZVS) operation. The DC-DC converter typically performs the maximum power point tracking (MPPT) while the DC-AC injects the power to the grid. This paper proposes a MPPT technique for a resonant CLLC DC-DC converter to guarantee Zero Voltage Switching (ZVS). First, the resonant converter is analyzed to determine the resistance observed by the PV panel and to determinate the frequency range which the converter operates with ZVS. Then, a modified Perturb and Observe algorithm is proposed, by performing perturbations in the DC-DC switching frequency. The proposed MPPT also verifies the derivative of the converter input resistance regarding the frequency to ensure that the converter operates in ZVS when the MPP is tracked. Finally, Matlab/Simulink simulations validate the proposed MPPT technique with a resistive load and a nonlinear load (DC-AC connected to the grid). The results show satisfactory performance, high steady-state efficiency, and good dynamic response.

As defined, a solar photovoltaic array is internally a power-limited nonlinear current source. They are commonly used to convert electromagnetic radiation from the sun, into electric power. Accurate models of arrays in series-parallel configuration, represent each sub-module with the double-diode model. Nevertheless, most of those models imply a high computational cost because they require the Lambert W-function to obtain approximated explicit equations for the sub-module's voltage and current. This paper proposes a model of series-parallel photovoltaic arrays, operating under homogeneous and non-homogeneous irradiance conditions, where each sub-module is represented by the implicit expression derived from the double-diode model. The array is divided into strings and a system of implicit nonlinear equations is obtained for each string with the sub-modules' voltages and string's current as unknowns. The corresponding systems of implicit equations are solved by using the Trust-Region Dogleg method to obtain all the electrical variables of the array. The results from the proposed model are compared with those obtained with the equivalent electrical circuit of the array, used as a reference. Simulation data for small, medium, and large arrays show that the proposed method yields data akin to those of the reference method obtaining RMSE values below 0.104 A for current-voltage curves in homogeneous and non-homogeneous conditions. Likewise, the model is validated against several experimental conditions, showing a remarkable agreement with RMSE values below 0.161 A for current-voltage curves in each condition. Therefore, the proposed model can be used to represent accurately series-parallel arrays operating in homogeneous and non-homogeneous conditions.