DC Power Converter Research Articles

Power Quality Improvement Meeting Important Grid Codes Using Three-Phase Five-Level CHB Inverter With Improved Quarter and Half-Wave Symmetry Based Optimized SHM-PAM

Selective harmonic minimization-pulse amplitude modulation (SHM-PAM) scheme suppresses more number of selected voltage harmonic components of a predefined voltage waveform pattern for a wider range. This article presents formulations of some improved five-level pulse patterns based on both quarter-wave symmetry (QWS) and half-wave symmetry (HWS) with a low number of switching instants using the optimized SHM-PAM scheme to meet the CIGRE WG36-05/EN 50160 and IEC 61000-3-6 grid codes. The switching angles and normalized value of dc voltage sources are calculated by the recently reported dragonfly algorithm based optimization technique. The performance of the proposed schemes has been verified through simulation and experimentation on a three-phase five-level cascaded H-bridge (CHB) inverter. A comparison between the proposed two types of formulations has been carried out based on various aspects, such as waveform quality, dc power conversion capability, and power loss in the power semiconductor devices of the CHB inverter and efficiency. It is observed that QWS formulations exhibit better waveform quality than the HWS formulations sacrificing the efficiency of CHB inverter due to higher switching losses. Moreover, the effectiveness of the proposed schemes has been compared with some prior conventional modulation schemes.

Comparison of Efficiency-Based Optimal Load Distribution for Modular SSTs with Biologically Inspired Optimization Algorithms

The battle of currents between AC and DC reignited as a result of the development in the field of power electronics. The efficiency of DC distribution systems is highly dependent on the efficiency of distribution converter, which calls for optimized schemes for the efficiency enhancement of distribution converters. Modular solid-state transformers (SSTs) play a vital role in DC distribution networks and renewable energy systems (RES). This paper deals with efficiency-based load distribution for solid-state transformers (SSTs) in DC distribution networks. The aim is to achieve a set of minimum inputs that are consistent with the output while considering the constraints and efficiency. As the main feature of modularity is associated with a three-stage structure of SSTs, this modular structure is optimized using ant lion optimizer (ALO) and validated by applying it to the EIA (Energy Information Agency) DC distribution network which contains SSTs. In the DC distribution grid, modular SSTs provide the promising conversion of DC power from medium voltage to lower DC range (400 V). The proposed algorithm is simulated in MATLAB and also compared with two other metaheuristic algorithms. The obtained results prove that the proposed method can significantly reduce the input requirements for producing the same output while satisfying the specified constraints.

Phase-Shifted Full-Bridge ZVS DC-DC Converter with Synchronous Double Rectifiers for Battery Charging Applications

This paper presents a phase-shifted PWM-controlled DC to DC power converter with a synchronous double rectifier. The power switches can be directed to achieve the zero-voltage switching condition using the technology of the full-bridge power converter and increase the efficiency of the converter on the secondary side of the transformer. A current doubling rectifier with low current ripple and synchronized rectifier circuits are also adopted. The secondary side of the high-frequency transformer uses the synchronous double rectifier. The synchronous double rectifier circuit converts AC voltage to DC voltage to enable high-current applications with two filtering inductors to reduce losses and dissipate heat, resulting in an efficient system. The proposed method can control the input DC voltage of the phase-shifted power converter at 400 V and achieves the required DC voltage of 24 V for battery charging applications under the zero-voltage switching condition. The results of simulations and experiments show 86.7% efficiency at 40% load condition and 91.8% efficiency at full load condition.

A New Topology of DC–DC Converter Based on Piezoelectric Resonator

The emergence of new piezoelectric materials makes it possible to offer high performances in terms of power density and integration. These new materials can be used in dc–dc power converters as a solution to replace the magnetic components and to meet the growing demand for miniaturization, high power density, and high-efficiency applications. This article deals with a new topology of a dc–dc converter based on a piezoelectric resonator. The conversion mechanism based on energy and charge balance is explained in detail through an analytical model and validated by experimental results. A prototype has been designed for an input–output voltage up to 250–125 V and a power range up to 175 W. It provides an efficiency higher than 93% for wide operating points in radial mode vibration. As an example, we have obtained an efficiency of 93.8% for 250–117 V input–output voltage at 50 W output power. In addition, the thickness mode operation is experimentally validated at 1 MHz and exhibited a peak output power of 175 W with an efficiency of 80% for 200–60 V input–output voltage. The experimental results show the promising performances of the proposed dc–dc power converter based on a piezoelectric resonator for high-to-low voltage, high efficiency, and low-to-medium power applications.

A Comprehensive Comparison of Two Fast-Dynamic Control Structures for the DAB DC–DC Converter

Benefitting from some significant advantages, the dual active bridge (DAB) dc–dc converter has become one of the most promising candidates for dc–dc power conversion. In recent years, some strategies have been proposed to boost the dynamic performance of DAB dc–dc converter under the disturbance of input voltage and load condition. According to the relationship between the compensation part and the model-based part, these existing schemes can be divided into two structures including the parallel structure and series structure. In the parallel control structure, the compensation part is added to the model-based part. In contrast, the compensation part is multiplied with the model-based part in the series control structure. By adopting proper feedback control, both control structures can provide excellent dynamic performance for DAB dc–dc converter easily. Hence, the modified parallel-structure fast-dynamic control scheme and the modified series-structure fast-dynamic control scheme are both proposed in this article. Then, using these two proposed schemes as examples, the merits and the demerits of both structures are analyzed, and the corresponding compensation methods are also presented. Moreover, a general PI design principle of the model-based control scheme for the DAB dc–dc converter is provided, which is different from the traditional concept for designing the PI parameters. In addition, the control delay of these two proposed schemes is analyzed, and a compensation method is also proposed. Finally, simulation results and experimental results are obtained to verify the analysis in this article and the excellent performance of the proposed methods.

Optimization of Grid-Connected Photovoltaic Power Generation Technology Based on Nonlinear Back-Stepping Controller

To address the issue of energy scarcity and to use solar photovoltaic energy as a renewable source, a three-phase grid-connected photovoltaic inverter system with uncertain system model parameters is investigated, which converts DC power into AC power, feeds it into the grid, and maintains the grid-connected part’s quality. An enhanced back-stepping approach is proposed to explore the control strategy of three-phase solar grid-connected inverter, which includes adaptive control, dissipative theory, sliding mode control, and rapid terminal sliding mode control, respectively. It is verified that the system is subjected to external interference F = 5 during 0.5 s–0.8 s. As per the simulation results, the improved adaptive terminal sliding mode control method can suppress the interference to a certain extent and has strong robustness to the external interference. When compared with the adaptive sliding mode control approach, the anti-interference ability is better, and the system stability is improved. Then, to improve the above approach, a high speed terminal sliding mode control method is proposed, which can swiftly converge in finite time and the estimated value of uncertain parameters is closer to the actual value, thereby boosting the system’s robustness.

Design, Analysis and Implementation of Bidirectional DC–DC Converters for HESS in DC Microgrid Applications

This research proposes an enhanced converter for a hybrid energy storage system (HESS) for a multi-input bidirectional DC–DC power converter (MIPC). When batteries are used for energy storage, their charge and discharge rates are low, putting the battery under current stress and shortening its life. Because of their increased power density, supercapacitors (SCs) can react quickly to abrupt fluctuations and solve this problem. SCs, on the other hand, cannot be utilized for storage since they cannot provide power for prolonged periods of time. Batteries and supercapacitors are employed together in HESSs because their opposing characteristics make them an ideal pair for energy storage. An MIPC is used to connect the HESS to the DC microgrid. The MIPC allows for decoupled battery and SC power regulation, as well as energy transfer across storage devices inside the system. A controller has been developed to regulate both HESS charging and discharging operations, making it a unified controller for DC microgrid applications. The proposed model predictive control (MPC) provided better DC grid voltage restoration to step change in PV generation and load demand over the traditional proportional integral (PI) control scheme. The MPC method minimizes current strains, extends battery life and enhances overall system performance in response to a step change in PV power and load demand as well as providing quicker DC grid voltage control. Simulation and experimental data for the proposed controller were created by varying PV generation and load demand, resulting in faster DC link voltage regulation.

Dual-Domain Maximum Power Tracking for Multi-Input RF Energy Harvesting with a Reconfigurable Rectifier Array

This work proposes a dual-domain maximum power tracking (MPPT) technique for multiple-input RF energy harvesting systems. A differential rectifier array is used to implement 4-channel reconfigurable RF to DC power conversion, and an adjustable 4-bit capacitor array is designed to improve the impedance matching between the antennas and the rectifiers. Using the perturbation and observation (P&O) method, both arrays are adaptively configured in the background with the variations of the input energy and output loading. Experimental results show that the proposed circuit successfully tracks the maximum power points while harvesting RF energy, with the peak conversion efficiency of 49.06% when the input energy is −6 dBm. With the proposed dual-domain MPPT, the high efficiency range of the energy harvesting system is greatly extended to 21 dB (−21–0 dBm).

Fuel cell‐based topologies and multi‐input DC–DC power converters for hybrid electric vehicles: A comprehensive review

In the last few decades, the utilization of fuel cells (FCs) in the automotive industry has created much attention due to easy use, modular structure, and higher efficacy. In the future, technological evolutions reveal that FC driven electric vehicles (EVs) will grow at a rapid pace and will become an excellent alternative to conventional vehicles. This paper discusses a detailed topological classification of the FC-based hybrid electric vehicle (FCHEV). In these FCHEVs, one of the critical elements is the DC–DC power converter unit. The hybridization of FCs with the other power sources requires more converter units that make the system complex. A multi-input DC–DC power converter is used to connect more than one energy source to reduce the system's complexity and improve the overall system efficacy. In this survey, numerous articles have been considered and examined vividly. An assessment of present and future scenarios of FCs based power source topologies and multi-input DC–DC power converter topologies used in HEV is presented. This survey provides a deep insight into the topic for the researchers and engineers working in this field.

Design and Real-Time Implementation of a Control System for SiC Off-Board Chargers of Battery Electric Buses

Emerging wide bandgap (WBG) semiconductors, such as silicon carbide (SiC), will enable chargers to operate at higher switching frequencies, which grants the ability to deliver high power and enhances efficiency. This paper addresses the modeling of a double-sided cooling (DSC) SiC technology-based off-board charger for battery electric buses (BEBs) and the design of its control and real-time (RT) implementation. A three-phase active front-end (AFE) rectifier topology is considered in the modeling and control system design for the active part of the DC off-board charger. The control system consists of a dual-loop voltage–current controller and is used to ensure AC to DC power conversion for charging and to achieve the targeted grid current total harmonic distortion (THD) and unity power factor (PF). Linear and nonlinear simulation models are developed in MATLAB/Simulink for optimum control design and to validate the voltage and current control performances. Four types of controllers (i.e., proportional–integral (PI), lead–lag, proportional–resonant (PR), and modified proportional–resonant (MPR)) are designed as current controllers, and a comparative analysis is conducted on the simulation model. In addition, the final design of the dual-loop controller is implemented on the RT–FPGA platform of dSpace MicroLabBox. It is then tested with the charger to validate the control performance with experimental data. The simulation and experimental results demonstrate the correct operation of the converter control performance by tracking the reference commands.

Fast and Accurate Approach to RF-DC Conversion Efficiency Estimation for Multi-Tone Signals.

The paper presents a computationally efficient and accurate numerical approach to evaluating RF–DC power conversion efficiency (PCE) for energy harvesting circuits in the case of multi-tone power-carrying signal with periodic envelopes. This type of signal has recently received considerable attention in the literature. It has been shown that their use may result in a higher PCE than the conventional sine wave signal for low to medium input power levels. This reason motivated the authors to develop a fast and accurate two-frequency harmonic balance method (2F-HB), as fast PCE calculation might appreciably expedite the converter circuit optimization process. In order to demonstrate the computational efficiency of the 2F-HB, a comparative study is performed. The results of this study show that the 2F-HB significantly outperforms such extensively used methods as the transient analysis (TA), the harmonic balance method (HB), and the multidimensional harmonic balance method (MHB). The method also outperforms the commercially available non-linear circuit simulator Keysight ADS employing both HB and MHB. Furthermore, the proposed method can be readily integrated into commonly used commercially available non-linear circuit simulation software, including the Keysight ADS, Ansys HFSS, just to name a few—minor modifications are required. In addition, to increase the correctness and reliability of the proposed method, the influence of PCB is considered by calculating Y parameters of its 3D model. The widely employed voltage doubler-based RF–DC converter for energy harvesting and wireless power transfer (WPT) in sub-GHz diapason is chosen to validate the proposed method experimentally. This RF–DC converter is chosen for its simplicity and capability to provide sufficiently high PCE. The measurements of the PCE for a voltage doubler prototype employing different multi-tone waveform signals were performed in laboratory conditions. Various combinations of the matching circuit element values were considered to find the optimal one in both—theoretical model and experimental prototype. The measured PCE is in very good agreement with the PCE calculated numerically, which attests to the validity of the proposed approach. The proposed PCE estimation method is not limited to one selected RF–DC conversion circuit and can also be applied to other circuits and frequency bands. The comparison of the PCE obtained by means of the proposed approach and the measured one shows very good agreement between them. The PCE estimation error reaches as low as 0.37%, and the maximal estimation error is 32.65%.

Large-Signal Stability Analysis and Design of Finite-Time Controller for the Electric Vehicle DC Power System

In the electric vehicle dc power system (EVDCPS), a motor or converter can be regarded as a constant power load (CPL) when tightly controlled. Different from the resistive load, CPL may make the EVDCPS unstable. Thus, in addition to less overshoot and shorter setting time, the controller of the converter applied in EVDCPS should maintain the system stable. In this article, the finite-time controller (FTC) is proposed based on exact feedback linearization (EFL) to stabilize the EVDCPS feeding CPL. First, to handle the nonlinearity caused by the CPL, the affine nonlinear model of EVDCPS is transformed into the Brunovsky canonical form by using EFL. Then, the finite-time control is adopted and a PI compensator is designed to eliminate the steady-state error. Under the proposed control algorithm, rigorous proofs indicate that not only the closed system can be large-signal stable, but also the EVDCPS bus voltage can converge the reference in finite time. Furthermore, to reduce the design difficulty of FTC, the backstepping method is adopted to design a backstepping finite-time controller(BFTC). Finally, simulations and experiments of FTC and BFTC are carried out. Results indicate that both FTC and BFTC have large-signal stability, and although the robustness of BFTC is inferior to FTC, the setting time and overshoot are greatly improved compared with the traditional linear feedback controller.

A Novel Buck-Boost Converter with an Enhanced Negative Output Voltage

This paper proposes the theoretical design of a novel buck-boost converter with an enhanced negative output voltage than conventional converters. It is beneficial for applications that require a wide range of conversion ratio. The steady-state as well as power-loss analyses of the proposed converter operating in continuous conduction mode are examined. Comparison with typical negative output converters like the buck-boost converter, self-lift Luo converter and hybrid buck-boost converter is also presented to emphasize the proposal. The design is simulated and tested by using MATLAB/SIMULINK software and found that the results consistently showed sensible conformity with the analysis. Keywords: conversion ratio, DC–DC power converters, negative output, steady state

Feedback Noise Propagation in Multisampled DC–DC Power Electronic Converters

This article analyzes the propagation of feedback noise in multisampled dc–dc power converters. The analytical calculations for noise attenuation, strictly valid for linear time-invariant systems, are found to offer good predictions for power converters, after suppressing the decimation effects of the digital pulsewidth modulator (DPWM). For control systems that employ a proportional-integral controller, without any digital low-pass filters, the nonlinearity caused by the DPWM decimation is found to saturate the noise attenuation properties, as the multisampling factor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N$</tex-math></inline-formula> is increased. Strong noise attenuation is enabled using antialiasing digital filters, with a small impact on the dynamic response. For control systems that employ a proportional-integral-derivative controller, increase of the multisampling factor, without any digital filters, causes the amplification of the noise power. Therefore, a greater attenuation of high-frequency components is required to provide a significant noise reduction in the control bandwidth. Even with these antialiasing digital filters, the dynamic response of multisampled control systems is improved compared to double-update. This is proven by the analytical and experimental comparison of various multisampled control strategies in terms of dynamic response and noise attenuation capabilities. The experimental results, from a buck-type converter, match well with simulations and analytical calculations.

Common-Mode Voltage Reduction Scheme for MMC With Low Switching Frequency in AC–DC Power Conversion System

In ac–dc power conversion system, modular multilevel converter (MMC) has been a promising technology, especially for high-voltage application. In such kind of application, the common-mode voltage (CMV) generated by power electronic switching can cause damage to electrical components and increase the electromagnetic interference (EMI) to the system. Hence, this article proposes a modulation scheme to reduce the CMV of MMC applied in high-voltage system, such as high-voltage dc. Usually, MMC consisting of numerous submodules (SMs) adopts the nearest level modulation (NLM) with the low switching frequency, so the CMV of the NLM scheme is analyzed, which indicates that the peak value of CMV is one-third of SM voltage. If one more or one less SM is turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> compared with NLM, the CMV caused by modulation can be eliminated theoretically. Subsequently, a modulation scheme based on the nearest zero CMV vector (NZCMVV) to reduce CMV is proposed for MMC. The NZCMVV scheme utilizes the two adjacent levels as candidate levels, and the theoretical ZCMVVs are picked out. Finally, the ZCMVV closest to the reference vector is selected to approximately replace the reference. The proposed method is simple and easy to implement. Simulated and experimental results validate that the proposed scheme can reduce CMV and CM current compared with the traditional NLM method.

7 level symmetrical inverter for photovoltaic system

This research presents the design, implementation, and evaluation of a seven-level symmetrical inverter for photovoltaic systems. The inverter is based on a cascaded H-bridges topology with distinct DC assets and is capable of efficiently converting DC power from a photovoltaic system to AC power with low Total Harmonic Distortion (THD). The system consists of a solar panel, charge controller, battery bank, and a multilevel inverter circuit. The inverter employs Pulse Width Modulation (PWM) techniques to control the output voltage and frequency, ensuring that it is suitable for the AC load. The performance of the inverter is analyzed using Fast Fourier Transform (FFT) to determine the THD, and the results are compared with those of other multilevel inverter topologies such as diode clamped (neutral clamped) and flying capacitors. The efficiency of the seven-level symmetrical inverter is evaluated under different load conditions and compared with other multilevel inverters to determine potential energy savings and performance improvements. The analysis provides insights into the advantages and limitations of the seven-level symmetrical inverter for photovoltaic systems, highlighting the importance of distinct DC assets in achieving high efficiency and low THD. The results of this research can be useful for designing and implementing high-performance and cost-effective photovoltaic systems.

철도차량 보조전원장치의 전압 제어 안정성 증대를 위한 Anti-windup 기법의 적용 및 비교 분석

In this paper, Application and Comparative Analysis of Anti-windup Method for Improving the Stability of Voltage Control of Auxiliary Power Supplies in Railway System. Because it is easy to design, and the structure is simple, there is a problem in the widely used PI controller to occur. Various problems occur, such as response time delay and overshoot due to integrator windup caused by the accumulation of errors in the integral controller. To improve this, various anti-windup methods have been studied. Among the representative Anti-windup methods, it was checked whether various problems caused by integrator windup could be solved through the conditional integral Anti-windup method and the tracking Anti-windup method and the error control Anti-windup. After confirming through PSIM simulation before hardware experiment, DC power conversion system was designed and improvements were confirmed.

An autonomous hybrid DC microgrid with ANN-fuzzy and adaptive terminal sliding mode multi-level control structure

Conventional fuels for power systems are now plaguing the environment more than ever before. Efforts to curb the environmental impacts of fossil fuels are now driving modern microgrids (MGs) to utilize green energy sources. In this regard, DC microgrids are well known for their versatility. Considering the rising significance of DC-MGs in future, this paper presents an aggregated DC microgrid model comprising of wind resource, photovoltaics, fuel cell, battery, and a supercapacitor. The model also includes DC–DC power converters and a two-level control structure. Firstly, the high-level of the proposed control structure constitutes an artificial neural network for maximum power point tracking and an intelligent energy management powered by a fuzzy logic controller. At this control level, the unified operation of the fuel cell and storage components under various dynamic conditions is ensured. Furthermore, the low-level control structure is based on an adaptive terminal sliding mode non-linear controller that derives the control signal for the converters. Finally, results showed that the energy management system along with the adaptive terminal sliding mode control successfully regulated the DC bus voltage by keeping the sources within their operational constraints. Moreover, the proposed non-linear controller demonstrated model’s robustness, successfully converged the sliding surface to zero in finite time, ensured global asymptotic stability and effectively dealt with the model uncertainties. All the simulation leading to these results were performed in MATLAB/Simulink and further evaluation was carried out by hardware in loop experiments using C2000 Delfino microcontroller F28397D launchpad.

A Modified Multi-Winding DC–DC Flyback Converter for Photovoltaic Applications

DC–DC power converters have generated much interest, as they can be used in a wide range of applications. In micro-inverter applications, flyback topologies are a relevant research topic due to their efficiency and simplicity. On the other hand, solar photovoltaic (PV) systems are one of the fastest growing and most promising renewable energy sources in the world. A power electronic converter (either DC/DC or DC/AC) is needed to interface the PV array with the load/grid. In this paper, a modified interleaved-type step-up DC–DC flyback converter is presented for a PV application. The topology is based on a multi-winding flyback converter with N parallel connected inputs and a single output. Each input is supplied by an independent PV module, and a maximum power point tracking algorithm is implemented in each module to maximize solar energy harvesting. A single flyback transformer is used, and it manages only 1/N of the converter rated power, reducing the size of the magnetic core compared to other similar topologies. The design of the magnetic core is also presented in this work. Moreover, the proposed converter includes active snubber networks to increase the efficiency, consisting of a capacitor connected in series with a power switch, to protect the main switches from damaging dv/dt when returning part of the commutation energy back to the source. In this work, the operating principle of the topology is fully described on a mathematical basis, and an efficiency analysis is also included. The converter is simulated and experimentally validated with a 1 kW prototype considering three PV panels. The experimental results are in agreement with the simulations, verifying the feasibility of the proposal.

Optimization for a Photovoltaic Pumping System Using Indirect Field Oriented Control of Induction Motor

Due to the increase in electricity and diesel costs, solar photovoltaic pumping systems have become a good solution, especially in rural areas. This work presents a standalone photovoltaic (PV) water pumping system (PVWPS) driven by an induction motor without energy storage to improve the pumping system’s performance. First, a comparison is made between two types: perturb and observe (P&amp;O) method and incremental conductance (INC) MPPT method with a variable step size that is automatically adjusted. Studying these two techniques helps to understand which one can result in a system with less oscillation and greater efficiency when tracking the maximum power point from the PV panel under sudden irradiation conditions. This MPPT works on the operating duty cycle of the boost converter. Then, that converter combines with a voltage source inverter (VSI) to convert DC power to AC power. Second, we use indirect field-oriented control (IRFOC), which drives the three-phase of an induction motor in turn to run the centrifugal pump. The simulation results of this work were obtained using the MATLAB Simulink platform.