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In recent years, there has been a growing interest in using model-free deep reinforcement learning (DRL)-based controllers as an alternative approach to improve the dynamic behavior, efficiency, and other aspects of DC–DC power electronic converters, which are traditionally controlled based on small signal models. These conventional controllers often fail to self-adapt to various uncertainties and disturbances. This paper presents a design methodology using proximal policy optimization (PPO), a widely recognized and efficient DRL algorithm, to make near-optimal decisions for real buck converters operating in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) while handling resistive and inductive loads. Challenges associated with delays in real-time systems are identified. Key innovations include a chattering-reduction reward function, engineering of input features, and optimization of neural network architecture, which improve voltage regulation, ensure smoother operation, and optimize the computational cost of the neural network. The experimental and simulation results demonstrate the robustness and efficiency of the controller in real scenarios. The findings are believed to make significant contributions to the application of DRL controllers in real-time scenarios, providing guidelines and a starting point for designing controllers using the same method in this or other power electronic converter topologies. [ABSTRACT FROM AUTHOR]

This paper presents a novel single-phase non-isolated bidirectional buck converter topology. The proposed converter uses a basic switching cell structure with a coupled inductor and an interleaving switching scheme. This article addresses a crucial challenge in bidirectional DC-DC conversion by prioritizing reducing output current ripples and minimizing filter inductor size. The employed method includes using MOSFETs with fast recovery diodes to mitigate reverse recovery and body diode losses. Furthermore, the optimization of the switching frequency of the output inductor to be twice the actual switching frequency contributes to reducing the component size of the converter. The coupled inductor also helps to reduce stress on components by distributing currents among its legs. The experimental result demonstrates the proposed converter has a very low ripple current as compared to the conventional converter. The low current ripples and smaller filter inductor size enabled by high-frequency operation have improved the efficiency and size of the converter. A common ground between input and output terminals ensures robust performance without common mode current concerns. Overall, the proposed converter represents a significant improvement in DC-DC converters, promising enhanced efficiency, reliability, and compactness in bidirectional DC-DC conversion systems. In order to verify the performance of the proposed converter, a 460 W buck converter prototype was built and tested. [ABSTRACT FROM AUTHOR]

Microgrids are designed to connect different types of AC and DC loads, which require robust power controllers to achieve an efficient power transfer. However, the effects of both AC and DC disturbances in the same type of controller make achieving stability a design challenge, especially in coupled systems where disturbances affect both the upstream and downstream in the microgrid. This paper presents an analysis of a second-order sliding-mode control (SOSMC) applied to a microgrid with direct-current (DC) and alternating-current (AC) power converters. The aim is to simulate the second-order sliding-mode control with buck converters that feed constant DC–DC and DC–AC power loads. The controller was tested in consideration of a unique sliding surface facing external disturbances, such as variations in the frequency of AC converters, sudden changes in upstream voltages, and constant power loads (CPL). The influence of the gain values (K) on the controller was also analyzed. The results show that the controller is robust regarding its sensitivity to external disturbances and steady-state error. However, the importance of the constant "K" in the model states that there exist K-limit values where if "K" is too low, a slowdown is presented, and the response against disturbances can be critical, and if is too high, an overshoot is presented in the output voltage. [ABSTRACT FROM AUTHOR]

Hybrid DC microgrid clusters contain various types of converters such as BOOST, BUCK, and bidirectional DC/DC converters, making the control strategy complex and difficult to achieve plug-and-play. The common master–slave hierarchical control strategy makes it difficult to achieve accurate and stable system control. This paper proposes an accurate peer-to-peer hierarchical control method for the hybrid DC microgrid cluster, and the working principle of this hierarchical control method is analyzed in detail. The microgrid cluster consists of three sub-microgrids, where sub-microgrid A consists of three BUCK converters, sub-microgrid B consists of three BOOST converters, and sub-microgrid C consists of two bidirectional DC/DC converters. According to all possible operations of various sub-microgrids in the microgrid cluster, the top-, mid-, and bottom-level controls are designed to solve the coordination control problem among different types of sub-microgrids. In this paper, a hybrid microgrid cluster simulation model is built in the PLECS simulation environment, and an experimental hardware platform is designed. The simulation and experiment results verified the accuracy of the proposed control strategy and its fast plug-and-play regulation ability for the system. [ABSTRACT FROM AUTHOR]

In this paper, a novel adaptive second-order sliding mode (2-SM) control approach, based on online zero-crossing detection, was proposed to solve the problems of the chattering and fixed control gain for buck converters with multi-disturbances. In modeling, the possible parameter perturbations and external disturbances of the converter system were contained. Instead of the traditional first-order sliding mode (1-SM), the twisting algorithm with 2-SM was adopted for the controller design, which could overcome the chattering problem and realize control continuity. Meanwhile, a novel adaptive mechanism was introduced to replace the conventional fixed control gain by time-varying control gain, the idea of which is to calculate the number of the zero-crossing points of the sliding surface online. As a result, the control magnitude of the improved controller could be reduced to a minimal admissible level, and the steady error of the output voltage could converge to the expected value. Furthermore, the robust stability of the converter system with multi-disturbances wads investigated. Comparative simulations and experiments validated the advantages of this paper as offering better robustness and control performance. [ABSTRACT FROM AUTHOR]

This paper proposes an extreme learning machine (ELM)-based adaptive sliding mode control strategy for the receiver-side buck converter system in the wireless power transfer system subjecting to the lumped uncertainty. The proposed control strategy utilizes a singularity-free fixed-time sliding mode (FTSM) feedback control, which ensures a fixed-time convergence for both the sliding variable and voltage tracking error. An ELM-based uncertainty bound estimator is further designed to learn the uncertainty bound information in real-time, which opportunely loosens the constraint of bound information requirement for sliding mode control design. The global stability of the closed-loop system is rigidly analyzed, and the good performance of the proposed control strategy is validated by comparison experiments which exhibit ideal overshoot elimination, 45.70–51.72% reduction of settling time, and 13.65–36.96% reduction of the root mean square value for voltage tracking error with respect to different load types. [ABSTRACT FROM AUTHOR]

This paper proposes two non-isolated step-down DC–DC converters based on the type-A three-state switching cell (3SSC-A), resulting in an alternative to the buck and buck-boost classical converters, respectively. The proposed topologies are part of a group of unexplored converters that employ the 3SSC-A, which has the advantages of 3SSC-based converters, such as high power density, reduced current stress on the semiconductors and suitable thermal loss distribution. In this regard, a complete static analysis is performed, including a detailed study of all semiconductor voltage and current efforts and developing loss models for each one. Moreover, by using simulation models, AC sweep analyses validate the dynamic frequency response of each converter's small-signal models, and PI-based output–voltage closed-loop controllers are duly designed. Finally, the topologies are experimentally validated through the implementation of adequately designed prototypes, achieving efficiency values greater than 91% under several output power rates varying from 50% to 100%. [ABSTRACT FROM AUTHOR]

Boosted interest in highly efficient power supplies based on renewables requires involving simulators during both the designing stage and the testing one. It is especially relevant for the power supplies that operate in the harsh environmental conditions of northern territories and alike. Modern solar panels based on polycrystalline Si and GaAs possess relatively high efficiency and energy output. To save designing time and cost, system developers use simulators for the solar panels coupled with the power converters that stabilize the output parameters and ensure the proper output power quality to supply autonomous objects: namely, private houses, small-power (up to 10 kW) industrial buildings, submersible pumps, and other equipment. It is crucial for the simulator to provide a valid solar panel I-V curve in various modes and under different ambient conditions: namely, the consumed power rating, temperature, solar irradiation, etc. This paper considers a solar panel simulator topology representing one of the state-of-the-art solutions. This solution is based on principles of classical control theory involving a pulse buck converter as an object of control. A mathematical model of the converter was developed. Its realization in MATLAB/Simulink confirmed the adequacy and applicability of both discrete and continuous forms of the model during the design stage. Families of I-V curves for a commercially available solar panel within the temperature range from − 40 to +25 ∘ C were simulated on the model. A prototype of the designed simulator has shown its correspondence to the model in Simulink. The developed simulator allows providing a full-scale simulation of solar panels in various operating modes with the maximum value of the open circuit voltage 60 V and that of the short circuit current 60 A. Issues of statistical processing of experimental data and cognitive visualization of the obtained curves involving the cognitive graphic tool 2-simplex have also been considered within the framework of this research. The simulator designed may serve as a basis for developing a product line of energy-efficient power supplies for autonomous objects based on renewables, including those operating in northern territories. [ABSTRACT FROM AUTHOR]

In this paper, an interleaved high-power zero-current-switching (ZCS) onboard charger (OBC) based on the three-phase single-switch buck rectifier is proposed for application to plug-in electric vehicles (EVs). The multi-resonant structure is used to achieve high efficiency and high power density, which are necessary to reduce the volume and weight of the OBC. This study focuses on the border conditions of ZCS converting with a battery load, which means the variation ranges of the output voltage and current are very large. Furthermore, a novel hybrid control method combining pulse frequency modulation (PFM) and pulse width modulation (PWM) together is presented to ensure a driving frequency higher than 10 kHz, and this will reduce the unexpected inner resonant power flow and decrease the total harmonic distortion (THD) of the input current under a light load at the end of the charging process. Finally, a prototype is established, and experiments are carried out. According to the experimental results, the conversion efficiency is higher than 93.5%, the THD about 4.3% and power factor (PF) 0.98 under the maximum power output condition. Besides, a three-stage charging process is also carried out the experimental platform. [ABSTRACT FROM AUTHOR]

This paper introduces an advanced transformerless multilevel hybrid-conversion topology intended for the interconnection of renewable DC sources at small-scale. The most important contribution presented in this paper is the generation of two isolated DC sources from a single DC source without the use of any type of transformer. The DC sources feed a nine-level DC/AC hybrid cascade multilevel converter. This advanced topology is achieved by redesigning the conventional DC/DC Buck topology, attached to the multilevel converter, and embedding a suitable switching strategy along with a Field Programmable Gate Array (FPGA)-based control. The advantages of the proposed structure, when compared to other proposals in the literature, are higher efficiency, reduced number of power switches, and high power density derived of transformerless characteristic. As a way to highlight differences and advantages of this converter over other options recently available in the literature, this paper carries out a quantitative evaluation comparing the number of voltage levels and the number of elements involved in the structure of DC/AC multilevel converters. The mathematical model and control strategy of the converter are explained and analyzed by means of simulations. Finally experimental results, obtained from a laboratory-scale prototype, show the performance of the system and demonstrate its relative advantages. [ABSTRACT FROM AUTHOR]

In this paper, a triangular spread-spectrum mechanism is proposed to suppress the electromagnetic interference (EMI) of a DC-DC buck converter. The proposed triangular spread-spectrum mechanism, which is implemented in the chip, can avoid modifying the printed circuit board of switching regulators. In addition, a lower ripple of output voltage of switching regulators and a better system stability can be realized by the inductive DC resistance (DCR) current sensing circuit. The chip is fabricated by using TSMC 0.18-μm 1P6M CMOS technology. The chip area including PADs is 1.2 × 1.15 mm2. The input voltage range is 2.7~3.3 V and the output voltage is 1.8 V. The maximum load current is 700 mA. The off-chip inductor and capacitor are 3.3 μH and 10 μF, respectively. The experimental results demonstrate that the maximum spur of the proposed DC-DC buck converter with the triangular spread-spectrum mechanism improves to 14dBm. Moreover, the transient recovery time of step-up and step-down loads are both 5 μs. The measured maximum efficiency is 94% when the load current is 200 mA. [ABSTRACT FROM AUTHOR]

This paper presents the modeling and the implementation of the digital control of a multileg interleaved DC-DC buck converter for electrical vehicle (EV) charging. Firstly, we derive a discrete averaged model of an n-leg interleaved buck converter (IBC). Secondly, we present a direct tuning procedure for one primary discrete PIDF (PID + filter) and multiple secondary PI controller. The objective of the control system is to regulate the current flow in each leg of the converter. This task is accomplished by introducing a novel control paradigm that simultaneously addresses two aims: on the one hand, the control scheme must guarantee an acceptable level of robustness under load variations; while on the other, an even distribution of power on each leg must be ensured at any operational condition. The proposed strategy hinges on a technique that combines simplicity and precision in the fulfillment of design frequency specifications. We use simulations and a digital signal processor (DSP) based experimental implementation of the design technique to validate the proposed methodology. [ABSTRACT FROM AUTHOR]

In this paper, we present a nonlinear PID controller based on saturation functions with variable parameters in order to regulate the output voltage of a buck converter in the presence of changes in the input voltage. The main feature of the proposed controller is to bound the control input with a variable parameter to avoid the windup effect generated by the combination of the integral control action and some operation conditions. The main advantages of the proposed nonlinear PID controller are its low computing cost and the simple tuning task to implement the control strategy in an embedded system. The acceptable behavior of the closed-loop system is presented through the simulation and experimental results. [ABSTRACT FROM AUTHOR]

A ripple-based constant on-time (RBCOT) buck converter with a virtual inductor current ripple (VICR) control can relax the stability constraint of large equivalent series resistance (ESR) at an output capacitor, but output regulation accuracy deteriorates due to the issue with output DC offset. Thus, this paper proposes a wave tracking reference (WTR) control to improve converter stability with low ESR and concurrently eliminate output DC offset on the regulated output voltage. Moreover, an adaptive on-time (AOT) circuit is presented to suppress the switching frequency variation with load current changes in continuous conduction mode. A prototype chip was fabricated in 0.35 µm CMOS technology for validation. The measurement results demonstrate that the maximum output DC offset is 4.1 mV and the output voltage ripple is as small as 3 mV. Furthermore, the switching frequency variation with the AOT circuit is 11 kHz when load current changes from 50 mA to 500 mA, and the measured maximum efficiency is 90.9% for the maximum output power of 900 mW. [ABSTRACT FROM AUTHOR]

The development and optimization of a hybrid system composed of photovoltaic panels, wind turbines, converters, and batteries connected to the grid, is first presented. To generate the maximum power, two maximum power point tracker controllers based on fuzzy logic are required and a battery controller is used for the regulation of the DC voltage. When the power source varies, a high-voltage supply is incorporated (high gain DC-DC converter controlled by fuzzy logic) to boost the 24 V provided by the DC bus to the inverter voltage of about 400 V and to reduce energy losses to maximize the system performance. The inverter and the LCL filter allow for the integration of this hybrid system with AC loads and the grid. Moreover, a hardware solution for the field programmable gate arrays-based implementation of the controllers is proposed. The combination of these controllers was synthesized using the Integrated Synthesis Environment Design Suite software (Version: 14.7, City: Tunis, Country: Tunisia) and was successfully implemented on Field Programmable Gate Arrays Spartan 3E. The innovative design provides a suitable architecture based on power converters and control strategies that are dedicated to the proposed hybrid system to ensure system reliability. This implementation can provide a high level of flexibility that can facilitate the upgrade of a control system by simply updating or modifying the proposed algorithm running on the field programmable gate arrays board. The simulation results, using Matlab/Simulink (Version: 2016b, City: Tunis, Country: Tunisia, verify the efficiency of the proposed solution when the environmental conditions change. This study focused on the development and optimization of an electrical system control strategy to manage the produced energy and to coordinate the performance of the hybrid energy system. The paper proposes a combined photovoltaic and wind energy system, supported by a battery acting as an energy storage system. In addition, a bi-directional converter charges/discharges the battery, while a high-voltage gain converter connects them to the DC bus. The use of a battery is useful to compensate for the mismatch between the power demanded by the load and the power generated by the hybrid energy systems. The proposed field programmable gate arrays (FPGA)-based controllers ensure a fast time response by making control executable in real time. [ABSTRACT FROM AUTHOR]

This paper presents the design and implementation of a digital control strategy for a Buck converter, used as a solar charger of valve-regulated lead acid (VRLA) batteries. The control system consists of two fuzzy logic controllers (FLCs), which adjust the appropriate increment of the converter duty cycle based on battery state of charge according to a three-stage charging scheme. One FLC works as a maximum power point tracker (FLC-MPPT), while the other regulates the battery voltage (FLC-VR). This approach of using two different set of membership functions overcomes the limitations of the battery chargers with a single control function, where the voltage supplied to the battery is either not constant due to the operation of the MPPT algorithm (possibly damaging the battery) or is constant due to the operation of the voltage control (hence, MPP cannot be achieved). In this way, the proposed control approach has the advantage of extracting the maximum energy of the PV panel, preventing battery damage caused by variable MPPT voltage, thereby extending the battery's lifetime. Moreover, it allows overcoming of the drawbacks of the conventional solar chargers, which become slow or inaccurate during abrupt changes in weather conditions. The strategy is developed to be implemented in a low-cost AT91SAM3X8E Arduino Due microcontroller. Simulations by MATLAB/Simulink and experimental results from hardware implementation are provided and discussed, which validate the reliability and robustness of the control strategy. [ABSTRACT FROM AUTHOR]

This paper presents the development of a discrete model of a photovoltaic (PV) system consisting of a PV panel, Maximum Power Point Tracking (MPPT), a dual-axis solar tracker, and a buck converter. The discrete model is implemented on a 32-bit embedded system. The goal of the developed discrete PV model is to provide an efficient way for evaluating several algorithms and models used by the PV system in real-time fashion. The proposed discrete model perfectly matches the continuous and discrete model simulated with MATLAB-SIMULINK. The real-time performance is tested by running the model to simulate the PV system, where the fastest time sampling of 1 ms is achieved by the buck converter model, while the longest time sampling of 100 ms is achieved by the solar tracker model. Moreover, a novel method is proposed to optimize the net energy, which is calculated by subtracting the energy consumed by the tracker from the PV energy generated. The proposed net energy optimization method varies the operation time interval of the solar tracker under high and low solar irradiation conditions. Based on the real-time simulation of the discrete model, our approach increases the net energy by 29.05% compared to the system without the solar tracking and achieves an increase of 1.08% compared to the existing method. [ABSTRACT FROM AUTHOR]

This paper presents the analysis and design of a PWM nonlinear digital control of a buck converter based on input-output linearization. The control employs a discrete-time bilinear model of the power converter for continuous conduction mode operation (CCM) to create an internal current control loop wherein the inductor current error with respect to its reference decreases to zero in geometric progression. This internal loop is as a constant frequency discrete-time sliding mode control loop with a parameter that allows adjusting how fast the error is driven to zero. Subsequently, an outer voltage loop designed by linear techniques provides the reference of the inner current loop to regulate the converter output voltage. The two-loop control offers a fast transient response and a high regulation degree of the output voltage in front of reference changes and disturbances in the input voltage and output load. The experimental results are in good agreement with both theoretical predictions and PSIM simulations. [ABSTRACT FROM AUTHOR]

This paper proposes a high-efficiency DC–DC converter with charge-recycling gate-voltage swing control with a light load. By achieving a variable gate-voltage swing in a very efficient manner by charge recycling, the power efficiency has been substantially improved due to the lower power consumption and the achieved balance between the switching and conduction losses. A test chip was fabricated using 65-nm CMOS technology. The proposed design reduces the gate-driving loss by up to 87.7% and 47.2% compared to the conventional full-swing and low-swing designs, respectively. The maximum power conversion efficiency was 90.3% when the input and output voltages are 3.3 V and 1.8 V, respectively. [ABSTRACT FROM AUTHOR]

This paper presents the dynamic analysis of a permanent magnet DC motor using a buck converter controlled by zero average dynamics (ZADs) and fixed-point inducting control (FPIC). Initially, the steady-state behavior of the closed-loop system was observed and then transient behavior analyzed while maintaining a fixed ZAD control parameter and changing the FPIC parameter. Other behaviors were studied when the value of the ZAD control parameter changed and the FPIC parameter was maintained at the initial value. Besides, bifurcation diagrams were built with one and two delay periods by changing the control parameter of the FPIC and maintaining fixed ZAD parameters while some disturbances were carried out in the electric source. The results show that the ZAD-FPIC controller allowed good regulation of the speed for different reference values. The ZAD-FPIC control technique is effective for controlling the buck converter with the motor, even with two delay periods. The robustness of the system was checked by changing the voltage of the source. It was shown that the system used a fixed switching frequency because the duty cycle was not saturated for certain ranges of the control parameters shown in the research. This technique can be used for higher order systems with experimental phenomena such as quantization effects, time delays, and variations in the input signal. [ABSTRACT FROM AUTHOR]

Without the Fluorinert solution and proper pad design, the high–voltage (HV) transistor used during the DC breakdown voltage (Vbk) measurement might be damaged by the partial discharge (PD) in the air if its Vbk is close to one thousand volts or more. From the waveform measurement, the PD in the air occurred at 650 V HV GaN HEMTs during the Vbk measurement, it is ignited by the unipolar arc, and it is not ignited by the avalanche breakdown. This is based on the fact that the current falls below zero ampere to become a negative current, and the voltage rises so that it is higher than the setting voltage of the DC meter at the onset of the PD, thus corresponding with the electrons, leaving the plasma to cathode, and enabling a build–in potential to exist in the plasma. Then, the PD ignites because the current starts to rise in order to allow for a positive spike current; the voltage level subsequently falls and a lower voltage reading is obtained. [ABSTRACT FROM AUTHOR]

Aiming at the unreliability resulting from ignoring the temperature effect and randomness of switching frequency in the traditional design method of an intrinsically safe Buck converter, a reliable design method based on the minimum frequency and considering the temperature characteristic is proposed. The theoretical design range of capacitance is deduced according to the maximum output ripple voltage and output intrinsic safety performance requirements. Considering the temperature characteristics of the capacitor, the actual maximum and minimum capacitances are obtained corresponding to the theoretical design capacitance within a given temperature range. It is pointed out that the actual minimum capacitance increases with the decrease of switching frequency, while the actual maximum capacitance is independent of frequency. Therefore, it can be deduced that there exists a minimum frequency which can meet the requirements of both output ripple voltage and intrinsically safe performance. When the actual maximum capacitance equals the actual minimum capacitance, the analytic expression of the minimum frequency is obtained. Assuming a capacitance adjustment, the actual working frequency of the converter corresponding to the minimum frequency is deduced. The design flow of an intrinsically safe Buck converter based on the minimum switching frequency considering the temperature characteristic is presented. The correctness of the theoretical analysis and the feasibility of the proposed design method are verified by experimental results. This design method can also be applied to other types of intrinsically safe converters. [ABSTRACT FROM AUTHOR]

A control technique combining pulse width modulation (PWM) and pulse amplitude modulation (PAM) is presented herein to reduce the output voltage ripple of the converter as little as possible. Such a converter requires a two-stage cascaded structure. The first stage is the buck-boost converter, which is used to adjust the output voltage of the second power stage, whereas the second stage is the two-phase interleaved buck converter, which is used to reduce the output voltage ripple. In theory, the two phases of the second stage operate under the condition of individual duty cycles of 50% with a phase difference of 180 ° between the two, and hence, the currents in the two phases are cancelled for any period of time, thereby making the output voltage of the converter almost voltage-free. Moreover, in order to improve the overall efficiency further, the proposed soft-switching technique based on an active clamp is presented and applied to these two stages to render the main and auxiliary switches turned on with zero-voltage switching (ZVS). Finally, the operating principles and control strategies of the proposed converter are described, and then, their effectiveness is verified by experimental results. [ABSTRACT FROM AUTHOR]

The article describes the principles based on which it is possible to obtain energy from renewable sources more efficiently. The principles use the conventional DC-DC interleaved buck converter based on the common electronic component types and the control strategy. A novelty of such a proposed solution lies in the methods which are not new, but with the right combination, better results can be achieved. The resulting method can be implemented into various topologies where the highest efficiency for wide input power is required. In case of the renewable energy sources where the power can vary hugely during the day, the proposed method can be implemented. Therefore, the article provides several steps, from calculation through simulation to experimental results that brings reader close to understanding of a such proposed solution. [ABSTRACT FROM AUTHOR]