Operation Of Power Converter Research Articles

Development of buck power converter circuit with ANN RL algorithm intended for power industry

PurposeThis paper aims to deal with application of artificial intelligence for solving real time control complication adhered with the controlled operation of a buck power converter. This type of converter finds application for power conversion at various levels for the direct current-direct current power industry to step down the input voltage.Design/methodology/approachUse of ANN-RL (Artificial Neural Networks- Reinforcement Learning)-based control algorithm to control buck power converter shows robustness against parameter and load variation. Because of non-linearity instigated by element used for switching, control of this converter becomes an arduous control predicament. All the classical control techniques are based on an approximate linear model of the step down converter and these techniques fail to handle actual non-linearity.FindingsIn this paper, a reinforcement learning-based algorithm has been used to handle and control buck power converter output voltage, without approximating the model of converter. The non-linearity instigated in converter is subjected to state of switch. Model of buck power converter is defined as a multi-step decision problem so that it can be solved using mathematical model of Markov decision process (MDP) and, in turn, reinforcement learning can be implemented. As MDP model is available for a discrete state system so model of converter has to be discretized and then value iteration is applied and output is analyzed. Load regulation and integral time absolute error analysis is done to show efficacy of this technique.Originality/valueTo mitigate the effect of discretization function approximation using neural network is applied. MATrix LABoratory has been used for implementation and result indicates an improvement in the overall response.

Turn-on Delay Based Real-Time Junction Temperature Measurement for SiC MOSFETs With Aging Compensation

Online junction temperature (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> ) measurement enables robust power converter operations by providing overtemperature protection and condition monitoring of the power devices. For SiC MOSFETs, the real-time T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> information is especially critical as limited field data are available regarding the reliability. In this article, utilizing the turn-ON delay time as temperature sensitive electrical parameter, an online T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> measurement is realized through an intelligent gate drive. Specifically, the turn-ON delay time is translated into the pulsewidth of a digital signal through the conditioning/logic circuits. During T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> measurements, the adjustable gate resistance circuit is activated to improve the measurement sensitivity beyond 600 ps/°C. Using the high-resolution capture module (300-ps resolution) in the system microcontroller, this pulsewidth is measured and then converted to junction temperature with a resolution of <; 0.5 °C. A prototype is built to validate the online T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> measurement method. The switching test results show that the circuit is able to precisely measure T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d,on</sub> and offers a good linearity/sensitivity for T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> estimation. In the continuous operation, the junction temperature of a decapsulated device using an infrared camera and T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> obtained from the circuit match well with <; 1 °C difference under various operating conditions. In addition, the gate-oxide degradation's impact on T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d,on</sub> is considered for SiC MOSFETs, and an aging compensation scheme is discussed to maintain the measurement accuracy throughout the device's lifetime. It is shown that the proposed circuit provides an accurate real-time T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> measurement for SiC MOSFETs, which can be deployed to improve the power converters' reliability.

Novel Adaptive Controller for Buck Converter with High Resource Efficiency and Low Computational Complexity

Power converters are used in a wide range of industrial processes. Computational complexity, tracking ability, and calculation accuracy are the main parameters that affect the switching performance of power converters. One of the major parts of switch-mode power converters is the controllers which are essential for proper operation. A new adaptive controller is proposed to reduce the computational complexity, the algorithm is presented based on Improved Variable Forgetting Factor (IVFF), Leading Dichotomous Coordinate Descent (DCD), and Exponentially-weighted Recursive Least Square (ERLS). The proposed method estimates the system coefficients with 98% accuracy. The settling time of the output voltage is 0.008[Formula: see text]ms which is faster than other algorithms. According to Leading DCD, this structure needs no multiplier and divider blocks. VFF leads to the improvement of the tracking ability and convergence rate in the system variations. This structure can be implemented on any application that needs an optimal controller. The Vedic mathematics as a multiplier operation is used in the structure of the improved VFF for reducing the calculation delay and area. The error of the proposed method converges to zero with lower than 60 iterations. In other words, the proposed algorithm calculates the optimal coefficients with lower than 50 iterations and is faster than another algorithm.

Design of a Single-Stage Power Converter Operating in Burst and Continuous Modes for Low-Power Energy Sources

A single-stage power converter, operating in either the burst or continuous mode for low-power energy sources, is presented in this brief. With the proposed converter, the energy from the ambient energy source is processed once (i.e., a single-step conversion process) before powering the load circuits, thereby allowing an increase in the overall efficiency once compared to two-step conversion processes. The proposed power converter is designed using off-the-shelf components consisting of a boost converter, a temporary storage element (i.e., supercapacitor) and an output switching circuit (OSC). The OSC is used to manage the duration period for the load that operates in either the burst or continuous mode. The proposed power converter can start the operation from an input voltage as low as 0.3 V and up-convert the output to about 3.7 V. This brief achieves a peak end-to-end efficiency of 70.06% through a single-step power conversion. The proposed power converter can support an output power range from 1 $\mu \text{W}$ to 202 mW. Once compared to prior work, the proposed power converter can achieve a wide dynamic load range, a higher end-to-end efficiency with a low input voltage as well as a single-step power conversion.

A Review of Switching Oscillations of Wide Bandgap Semiconductor Devices

Wide bandgap (WBG) devices offer the advantages of high frequency, high efficiency, and high power density to power converters due to their excellent performance. However, their low parasitic capacitance and fast switching speed also make them more susceptible to switching oscillations. The switching oscillations can cause voltage and current overshoots, shoot-through, electromagnetic interference, additional power loss, and even device damage, which can seriously affect the performance of power converters and systems. However, a comprehensive and in-depth overview is lacking on this topic. This article reviews the types, the causes and negative effects, the effects of parasitic parameters and suppression methods of these switching oscillations, which is helpful for practical engineering. First, the switching oscillations are divided into different types, and their causes and negative effects are reviewed. Then, the effects of different parasitic parameters on the switching oscillations are overviewed. It is found that due to the different physical structures of silicon carbide metal-oxide-semiconductor field-effect transistors, enhancement-mode gallium nitride high-electron mobility transistors (eGaN HEMTs), and cascode GaN HEMTs, the effects are also different. Finally, the main methods of suppressing the switching oscillations are summarized, and the advantages and disadvantages of these methods are presented. Furthermore, future research works on this topic and the conclusion of this paper are drawn, which will help readers deepen their understanding of the switching oscillations of WBG devices, and inspire readers to better use WBG devices for high-frequency and high-efficient power conversion.

Comparison of Phase-Shift and Modified Gating Schemes on Working of DC-DC LCL-T Resonant Power Converter

This brief discusses the operation and performance comparison of LCL-T DC-DC resonant power converter when controlled with fixed-frequency phase-shifted gating (PSG) and modified-gating signals (MGS) schemes. The converter is designed to operate in lagging power factor mode to accomplish zero-voltage switching (ZVS) of the inverter switches. The operating principle of the converter with the two proposed gating schemes is explained. A brief steady-state analysis of the converter using Fourier series approach is presented. The choice between PSG and MGS schemes is made by comparing the performance of the converter. It is found that both the gating schemes are effective in regulating the output voltage for variable input voltage and loading conditions. However, the efficiency of the converter is found to be higher with MGS due to the fact that only one switch loses ZVS as compared to two with the PSG when operated with maximum input voltage. Also, the variation in pulse-width angle (δ) required to regulate the output voltage is small in MGS as compared to that with PSG. A 300 W experimental prototype of the converter has been built and tested to verify the theoretical results. It is experimentally confirmed that the MGS control gives the better performance than the PSG control for different input voltage and loading conditions.

Boundary Control With Corrected Second-Order Switching Surface for Buck Converters Connected to Capacitive Loads

Boundary control (BC) with second-order switching surface is exploited for achieving faster response time and robust operation of switching power converters. However, the system performance of the boundary-controlled converters is significantly affected when it is connected to a second-stage converter with a large input capacitor. This article studies the shortcomings in second-order BC schemes of buck converter with capacitive loads and nonlinear switching loads. Second, this article proposes a BC scheme with corrected second-order switching surface to drive buck converters cascaded to boost converters. The switching criteria of the corrected control law account for the effect of unknown load capacitance as well as the variation in filter parameters. Therefore, an outer voltage ripple feedback loop is introduced to determine the corresponding switching criteria gain factor that adjusts the overall gain, while maintaining the output voltage ripple at a specified voltage band. The proposed method is verified by both simulation and hardware experiments. A 250-W buck converter prototype has been built to validate the control scheme under different load types, including a resistive-capacitive load, a boost converter, and a commercial dc electronic load. A comparison is drawn between conventional BC and the proposed method in both simulation and experimental environment, in order to highlight the advantages of the proposed method. With this approach, the converter operates at designed BC parameters independent of load capacitance and system parameter variations.

Converter‐level reliability prediction and analysis in switched reluctance motor drive

Reliability has been a dominant factor in the performance of power converters. In this study, an enhanced k -out-of- n :G model is presented to predict and analyse the reliability of typical asymmetric half-bridge power converter in switched reluctance motor drive. First, the reliability estimation procedure is introduced including electrothermal model, failure rate model, and reliability model, during which the electrothermal model is critical to accelerate the process of reliability prediction. Next, the enhanced k -out-of- n :G model can be built, and corresponding solving process is derived. Meanwhile, the reliability comparison is quantitatively illustrated between conventional k -out-of- n :G models, generally accepted Markov model, and enhanced k -out-of- n :G model, indicating the result with the proposed model is consistent with Markov model. Moreover, the modelling and solving processes are simpler. Then, the reliability is optimised in respect to turn-on angle, turn-off angle, and fault-tolerance strategies with the enhanced k -out-of- n :G model, providing a guideline to select the most effective control parameters and strategies for reliability improvement. Finally, the fault experiments and thermal stress measurement are carried out to indirectly validate the reliability analysis.

Wide-Bandgap Semiconductor HF-Oscillation Attenuation Method With Tuned Gate $RLC$ Filter

Wide-bandgap (WBG) transistors provide better switching performance and higher operating temperatures compared to state-of-the-art Si devices and are suited for high-frequency applications due to very short switching times. The main obstacle for implementation of WBG transistors at full potential is the high-frequency oscillation in voltage and current during switching transients. Oscillations arise from resonance due to parasitic and device inductances and capacitances. Introduction of WBG transistors depends on the elimination of these oscillations and their negative effect on the performance of power converters. Good layout practice is mandatory, but there is a limit to the reduction of these parasitics, and often, slowing of the semiconductor switching time must be applied. This article presents a simple methodology for the attenuation of the negative effects of WBG transistor high-frequency oscillations without increasing rise and fall times. The proposed methodology is based on determination of the source of feedback resonant frequency between gate and power loops using network analyzer measurement on printed circuit board and utilization of a tuned $RLC$ filter. Experimental application of the methodology shows a direct relationship between loop resonant frequency and voltage and current oscillations. The proposed method reduces power losses, high-frequency oscillations, and electromagnetic interference.

Ensuring a Reliable Operation of Two-Level IGBT-Based Power Converters: A Review of Monitoring and Fault-Tolerant Approaches

Despite the emerging multi-phase and multi-level converters, two-level insulated gate bipolar transistor-based power converters are still widely used in industrial applications in nowadays. Thus, its reliability is of significant importance for ensuring industrial safety. In this paper, a review of the possibilities to ensure the reliable operation of these power converters is presented. The possible approaches are categorized into two groups: condition monitoring and fault-tolerant control. The former approach performs the monitoring methods of power converters, which enables the identification of device degradation to be realized. Accordingly, the mechanisms, indicators, and measuring methods of degradation are demonstrated in this paper to assist the design of condition-based maintenance. In contrast, the latter approach is a post-fault one, where power converters remain the operation by activating the fault-tolerant units after faults are identified. For this approach, fault detection, fault isolation, and tolerant strategies are essential. Finally, the performance and cost-effectiveness of the two categories are discussed in this paper.

ДОСЛІДЖЕННЯ ДЕРЖАВНОГО ПЕРВИННОГО ЕТАЛОНУ ОДИНИЦІ СИЛИ ЗМІННОГО СТРУМУ

The article is devoted to the results of the research in order to solve the problem of metrological support of production and operation of thermoelectric power converters, precision meters and AC power sources in the branches of the national economy. The optimal solution to the problem of metrological support is to create a national standard unit of alternating current. The article conducts theoretical research, comparison with foreign analogues and analysis of methods for measuring and reproducing the strength of alternating current. The analysis of the precision means intended for measurement, reproduction and comparison of force and voltage of alternating current is carried out. Theoretical bases of creation of a high-precision standard of unit of alternating current are outlined. To build a national standard, the method of comparing the AC current with the equivalent DC current using a precision thermoelectric converter and shunts was chosen. The composition and requirements to the operating conditions of the national standard are determined. Since the storage and reproduction of a unit of alternating current must be realized by comparison with the equivalent direct current, the main source of uncertainty of measurements of this unit is a combination of uncertainties of measurements of thermoelectric comparator Fluke 792A, precision shunts A40, which are part of the standard, output voltage meters measure the electrical resistance to direct current and the output signal of the thermocomparator. According to the results of research work, for the first time in Ukraine the national standard of an alternating current unit was put into operation.

Thermal monitoring of LiFePO4 batteries using switching harmonics

Thermal monitoring is of high relevance for safe operation and degradation management of batteries. Direct measurement of battery temperature has drawbacks due to both cost and reliability issues. To overcome these limitations, the development of temperature estimation methods has received significant research attention. Most of the existing estimation methods are based on the injection of an additional signal, which can produce additional losses. This article proposes a temperature estimation method for LiFePO4 batteries using the switching harmonics of the converter feeding the battery. Temperature changes are estimated from the variation of the battery impedance at the switching frequency. The method operates online and without interfering with the normal operation of battery and power converter, and does not therefore introduce additional losses or any other adverse effect in the batteries.

Design and Experimental Assessment of a Robust Voltage Control for DC-DC Converters Considering Components Parametric Uncertainties

This study presents the design and evaluation of a robust controller, based on frequency-domain, in order to enhance the performance of dc-dc power converters under parametric uncertainties. This robust control approach takes into account all possible uncertainties in the system such as load and input voltage variations. Thereby, the robust controller design is based on the constraints of the gain and/or phase margins delimited by these uncertainties in order to ensure robust performance and stability of the system. Assessments on the performance of the proposed robust control are conducted. Comparisons with other control methods are also provided. Experimental validations on a dc-dc buck converter system test board are carried out to verify the theoretical claims.

Enabling Multistep Model Predictive Control for Transient Operation of Power Converters

Recently, an efficient multistep direct model predictive control (MPC) scheme for power converters has been proposed. It relies on the Sphere Decoding Algorithm (SDA) to solve the associated long-horizon optimal control problem. Since the SDA evaluates only a small number of candidate solutions to find the optimal one, a significant reduction in the average computational burden can be achieved compared to the basic exhaustive search approach. However, this is only true during steady-state operation. In fact, the SDA still requires a large execution time during transients. This paper shows that if not properly addressed, the dynamic performance of the system may be degraded, which clearly limits its practical application. To mitigate this issue, which particularly arises during transients, an efficient preconditioning approach for the SDA is proposed. This approach ensures that only a small number of candidate solutions are evaluated during both steady-state, and transients. This allows the multistep direct MPC to become a viable control alternative for power converters operating at low semiconductor switching frequencies, e.g., below 450 Hz. The proposal is validated using a grid-connected three-level converter as a case study. Both processor-in-the-loop simulations, and experimental results on a scaled-down 2.24 kVA laboratory setup are presented.

Common-Mode EMI Unterminated Behavioral Model of Wide-Bandgap-Based Power Converters Operating at High Switching Frequency

With wide-bandgap semiconductors increasing their commercial availability, high switching frequency operation has become an accepted practice to increase power density in power converters. High switching frequency operation, nonetheless, increases the electromagnetic interference (EMI) emissions of converters, for which accurate models are needed in order to predict their EMI noise and aid in the design of necessary filters. To this end, this paper assays first the impact that high switching frequency has on converter EMI emissions, and second, uses an unterminated behavioral model (UBM) to predict the common-mode (CM) emissions in the conducted EMI range (150 kHz–30 MHz). To achieve this, a new extraction procedure is developed for a UBM to effectively capture the rich high-frequency content of the CM emissions, providing a solution to the inherent limitations of previous behavioral models developed for insulated-gate bipolar transistor-based converters. The experimental results obtained with two setups: a 3-kW, 300-V dc, silicon-carbide-based three-phase inverter switching at 70 kHz and a 1-kW, 400-V dc, gallium nitride -based three-phase inverter switching at 500 kHz are presented to validate the approach and the model capabilities.

Performance of InGaAs metamorphic laser power converters at different conditions

The topic of the work is the metamorphic InGaAs heterostructures for laser power converters (LPC) and their performance at different measurement conditions. Three different illumination conditions were studied: monochromatic Xe-lamp uniform illumination, laser with quasi-uniform illumination (with laser beam unfocusing) and non-uniform focused laser illumination. For simulating the experimental IV-curves as well as FF-Jg, Voc-Jg and η-Jg dependences, a tube model developed earlier and describing the charge carrier transport along current lines was used for all three illumination regimes. In the absence of losses (Xe-lamp and unfocused laser), the perfect model simulation model exhibiting an experimental efficiency greater than 50% (for λ=1064nm) has been demonstrated. As a result of simulation of LPC characteristics obtained under focused laser illumination, the losses associated with uniform light distribution as well as with an additional resistance, which decrease the LPC efficiency, have been found.

Review of GaN HEMT Applications in Power Converters over 500 W

Because of the global trends of energy demand increase and decarbonization, developing green energy sources and increasing energy conversion efficiency are recently two of the most urgent topics in energy fields. The requirements for power level and performance of converter systems are continuously growing for the fast development of modern technologies such as the Internet of things (IoT) and Industry 4.0. In this regard, power switching devices based on wide-bandgap (WBG) materials such as silicon carbide (SiC) and gallium nitride (GaN) are fast maturing and expected to greatly benefit power converters with complex switching schemes. In low- and medium-voltage applications, GaN-based high-electron-mobility transistors (HEMTs) are superior to conventional silicon (Si)-based devices in terms of switching frequency, power rating, thermal capability, and efficiency, which are crucial factors to enhance the performance of advanced power converters. Previously published review papers on GaN HEMT technology mainly focused on fabrication, device characteristics, and general applications. To realize the future development trend and potential of applying GaN technology in various converter designs, this paper reviews a total of 162 research papers focusing on GaN HEMT applications in mid- to high-power (over 500 W) converters. Different types of converters including direct current (DC)–DC, alternating current (AC)–DC, and DC–AC conversions with various configurations, switching frequencies, power densities, and system efficiencies are reviewed.

Passivity-Based Control Design Methodology for UPS Systems

This paper presents a passivity-based control (PBC) design methodology for three-phase voltage source inverters (VSI) for uninterruptable power supply (UPS) systems where reduced harmonic distortions for the nonlinear load, reduced output voltage overshoot, and a restricted settling time are required. The output filter design and modification for efficient control and existing challenges with the assignment of scaling coefficients of the output voltage, load, and inductor currents are addressed and analyzed. Notably, special attention is given to the modulator saturation issue through implementing an accurate converter model. Applications of the two versions of PBC in three-phase voltage source inverters using stationary αβ and rotating dq frames for a constant frequency of the output voltage are presented. Furthermore, the influence of the PBC parameters on the power converter performance is investigated. A comparative simulation and the experimental results validate the effectiveness of the presented passivity-based control design methodology.

Automated tool for 3D planar magnetic temperature modelling: application to EE and E/PLT core‐based components

Thermal performance of power converters is a key issue for the power integration. Temperatures inside the active and passive devices can be determined using thermal models. Modelling the temperature distribution of high-frequency magnetic components is quite complex due to the diversity of their geometries and used materials. This study presents a thermal modelling method based on lumped elements thermal network model, applied to planar magnetic components made of double planar E shaped cores (EE) and planar E core combined with plate one (E/PLT). The 3D model is automatically generated from the component's geometry. The computation enables to obtain 3D temperature distribution inside windings and core of planar transformers or inductors, in steady state or in transient case. This study details the proposed modelling method as well as the automated tool including the problem definition and the solving process. The obtained temperature distributions are compared with finite-element simulation results and measurements on different planar transformers.

Condition Monitoring the Health Status of Forced Air Cooling System Using the Natural Frequency of Thermal Network

The forced air cooling system plays an important role in the safe operation of power converters. Condition monitoring its health status can improve the reliability of power converter and reduce the cost of unscheduled maintenance due to over-heating. This letter proposed to use the natural frequency of thermal network as an indicator to monitor the aging process of cooling system. We show that the degradation of the cooling system can be monitored by detecting the variation of thermal network natural frequency. Experimental tests on a three-phase dc/ac converter with forced air cooling system are performed to verify the effectiveness of proposed method. This method is simple to implement and does not need to measure the power loss. Moreover, it enables the concurrent monitoring of multiple components in the cooling system.