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The transient performance during power reversal in a bidirectional dual active bridge (DAB) dc–dc converter usually suffers from the issues of current deviation, hard switching, and other induced problems. In this article, a novel phase-shift method for fast power reversal in a DAB converter is proposed, which can achieve transient zero voltage switching (ZVS) without dc current bias, and therefore, shows advanced transient performance. The detailed algorithms and the effective phase-shift ranges based on different voltage conversion ratios are elaborated. An error analysis of the performance of dc bias elimination is provided to evaluate probable errors within allowed tolerances. Extensive and comparative experimental results are provided to support the validity of the proposed phase-shift method. It is shown that smooth, fast, and reliable power reversal can be effectively achieved with the novel method, and there is no need to add snubbers into the circuit by virtue of transient ZVS.

Electromagnetic interference (EMI) filters are inevitable parts of power electronic systems. A novel EMI filter for single-phase grid-inverter is proposed in this study, to suppress the common-mode (CM) EMI noise. The noise source and propagation path impedances are analysed, and the interaction between AC and DC side is studied. By connecting the ground terminal of the CM capacitors to the midpoint of the DC-link, the noise coupling between AC and DC side is reduced. When compared with the state-of-the-art of EMI filter, the proposed topology has advantages: the AC and DC filters can be designed independently; the impedance of the CM loop is improved; there is a remarkable CM EMI noise suppression effect on both AC and DC sides. Simulation and experimental results verify the theoretical analysis and proposed EMI filter structure.

Renewable energy generations have been attracting sustained attentions in academic and industry. Current-fed-isolated-bidirectional dc/dc converters (CF-IBDCs) are widely adopted in low-voltage high-current applications such as solar photovoltaic fuel cell with energy storage. This paper gives an overview and a comprehensive comparative evaluation of CF-IBDCs. The active clamped, dual half-bridge, L-L type dual active bridge, resonant-type, naturally clamped, and other type topologies of CF-IBDCs are investigated, analyzed, and compared regarding their circuit topological structures, operation characteristics, modulation methods, and soft-switching technologies. In addition, component cost models and loss models of converters are deduced and presented. On this basis, quantitative and comprehensive performance comparison of seven typical CF-IBDC topologies selected from each type is conducted in terms of costs, losses, weight, volume, and power density for the given system specifications and design constraints. Finally, the application range of different CF-IBDCs and future trend are presented to encourage further development.

Harmonic and electromagnetic interference (EMI) filters are the two important parts in the grid-connected inverter for the harmonic and EMI noise suppression. This article investigates the combined magnetic integration of the harmonic and EMI filters with the volume and weight reduction, which is defined as the integrated LCL–EMI filter in this article. Both common-mode (CM) and differential-mode (DM) models of the integrated inductor with EE-type magnetic core are built and analyzed. By designing the air gap of the center leg and arranging the windings properly, the distribution of magnetic flux on the magnetic branch can be controlled. As a result, harmonic inductors and a CM inductor can be effectively designed in the center leg and side leg, respectively. A symmetrical LCL filter is designed instead of the traditional asymmetrical structure with an integrated magnetic core. The current harmonic distortion analysis and EMI measurement results based on simulation and experiment results verify the effectiveness of the proposed integration method in the silicon carbide (SiC) MOSFET-based grid-connected inverter. Moreover, weight and volume comparisons between the integrated inductor and the traditional discrete inductors also reflect the superiority of the magnetic integrated LCL–EMI filter.

A new three-level bidirectional dc–dc converter configuration for the battery and supercapacitor (SC) energy storage systems in dc microgrids is presented in this paper. The PI-based control method is implemented to operate the proposed converter with hybrid energy storage system. Furthermore, joint control is utilized to obtain rapid dc-link voltage restoration and effective power sharing between battery and SC based on their respective characteristics. The system operating principle, controller design, stability analysis, simulation studies, and experimental studies are presented in this paper. The proposed three-level bidirectional dc–dc converter configuration can effectively integrate the battery and SC with the bidirectional power flow. The proposed control method provides the effective participation of the SC system which reduces the stress on the battery system. The presented converter configuration is effective in reducing the stress on the power semiconductors and provides better performance with smaller passive components. The experimental platform is built to test and validate the three-level bidirectional dc–dc converter and the proposed control method for the HESS.

This article presents a deadbeat-based method for the hybrid energy storage system (HESS) in solar-assisted electric vehicles (EVs), using a new bidirectional three-level cascaded (BTLC) converter. Moreover, photovoltaic (PV) panels are also considered in the system, because the proposed method is designed for solar-assisted EV applications to achieve a longer driving range. The proposed BTLC converter can integrate the battery and the supercapacitor as an HESS to effectively mitigate the power mismatch between the PV power generation and the load power consumption for the solar-assisted EVs. The BTLC converter is superior to the conventional parallel-connected bidirectional battery/supercapacitor converters from the perspectives of related component size reduction and control flexibility. To regulate the BTLC converter, a deadbeat-based method is proposed, which can provide the proper power management for the battery and the supercapacitor, and maintain the bus voltage. The design and implementation of the proposed deadbeat-based method are analyzed in detail. A scaled-down prototype of the proposed BTLC converter is built for the experimental verification. The simulation and experimental results are presented and compared to verify the effectiveness of the deadbeat-based method for the HESS with the proposed BTLC converter.

Load frequency control (LFC) is playing an indispensable role to achieve the secure and economic operation of power grids. However, the existing LFC schemes either may rely on a nonlinear grid model under perfect operating condition with nominal parameters, or they may adopt a complicated control structure of high order. These LFC schemes may have poor control performance or even loss of stability in real-time implementation due to the grid uncertainties and the change of system operation scenarios. Consequently, a hybrid control method with two control loops considering various practical scenarios is originally proposed in this paper. In the inner loop, variable universe fuzzy logic control is applied to mitigate the impact of load disturbances on control performance. In the outer loop, an incremental genetic algorithm is employed to online optimize the control parameters. The performance of the proposed control method is comprehensively tested on a MATLAB/Simulink-based LFC model and a real-time digital simulator-based real-life 49-bus power system. The extensive results show that the proposed hybrid method exhibits comparatively better control performance than an adaptive fuzzy logic controller and an improved proportion integration controller.

This paper presents an electromagnetic interference (EMI) filter design procedure for a single-phase SiC MOSFET inverter. To ensure the EMI filter performance is both accurate and effective, the equivalent noise source impedances of common mode (CM) and differential mode (DM) noise models are extracted. Then the CM and DM EMI filters can be designed based on the known CM and DM noise source impedances, respectively. The EMI filter design based on the proposed method is validated both through simulation and experiments. The simulation and experiment results have verified the effectiveness of the proposed method.

Photovoltaic (PV)/battery hybrid power units have attracted vast research interests in recent years. For the conventional distributed power generation systems with PV/battery hybrid power units, two independent power converters, including a unidirectional dc-dc converter and a bidirectional converter, are normally required. This paper proposes an energy management and control strategy for the PV/battery hybrid distributed power generation systems with only one integrated three-port power converter. As the integrated bidirectional converter shares power switches with the full-bridge dc-dc converter, the power density and the reliability of the system is enhanced. The corresponding energy management and control strategy are proposed to realize the power balance among three ports in different operating scenarios, which comprehensively takes both the maximum power point tracking (MPPT) benefit and the battery charging/discharging management into consideration. The simulations are conducted using the Matlab/Simulink software to verify the operation performance of the proposed PV/battery hybrid distributed power generation system with the corresponding control algorithms, where the MPPT control loop, the battery charging/discharging management loop are enabled accordingly in different operating scenarios.

As the renewable energy sources (RESs) are being connected to grid through power electronics-based converters without any inertia, the decreasing inertia issue of the distributed power system becomes more and more critical. The quasi-Z source inverter (qZSI) presents many advantages when applied to photovoltaic (PV) power system, such as voltage boost ability and turning the upper and lower switches of one bridge leg without damaging the devices. Thus, this paper proposes a method to emulate the power system inertia based qZSI PV power system. By regulating the voltage of two capacitors in the qZSI and dc-link capacitors according to the grid frequency proportionally, the capacitors can serve as an energy buffer for frequency support. The advantages of the proposed method are its simple implementation process and that the system inertia can be enhanced without adding hardware resources. Simulation and experimental results verify the feasibility of the proposed virtual inertia method and the proposed control scheme.

For reducing mounting space and improving the power density of drive system, it is of great significance to investigate the estimation of the rotation and position of the permanent magnet synchronous motor (PMSM). In this paper, a sensorless control strategy based on the model reference adaptive system (MRAS) has been proposed. Meanwhile, with SiC-MOSFET applied instead of the Si-IGBT device for a higher switching-frequency, that the load-side current can be improved with lower harmonics, and the satisfied performance of the control system based on MRAS can be furtherly promoted. Finally, the proposed strategy will be verified by the simulation and experiment results.

In this work, a two-probe approach is proposed to extract noise source impedance under operating conditions. The proposed two-probe method is introduced and then validated by several passive components. Compared with the previous impedance extraction methods, the proposed approach has no direct electrical contact to equipment under test (EUT). Moreover, the calibration to eliminate the influence of probes and cables is conducted without any contact to the EUT. Finally, experimental results showed EMI filter designed based on the proposed approach can effectively attenuate conducted emissions in single-phase inverter.

For power converters with inductive loads, a freewheeling path is needed for the current due to reactive power. The MOSFET synchronous rectification (SR) is widely used to reduce the conduction loss during the freewheeling period. Due to the wide band gap of silicon carbide (SiC), the intrinsic body diode of SiC MOSFET exhibits a high voltage drop. Hence, an antiparallel SiC Schottky diode is normally implemented to eliminate its conduction. However, the external SiC Schottky diode is not fully utilized as it only works during the dead time. In this paper, the hard-switching SR is investigated in an SiC three-phase inverter and compared with a conventional inverter using freewheeling diode (FWD). An improved power loss model for the two inverters has been developed. It is found that the inverter using SR has higher efficiency due to the smaller switching loss. A 7-kW prototype of SiC three-phase inverter is built, which achieves a peak efficiency of 98.8% (±0.15%) and 98.5% (±0.15%) at 40 kHz using SR and FWD, respectively. This paper confirms that the SiC MOSFET is an ideal candidate for the SR. NRF (Natl Research Foundation, S’pore)

This paper presents a design methodology for a high power density converter, which emphasizes weight minimization. The design methodology considers various inverter topologies and semiconductor devices with application of cold plate cooling and LCL filter. Design for a high-power inverter is evaluated with demonstration of a 50 kVA 2-level 3-phase SiC inverter operating at 60 kHz switching frequency. The prototype achieves high gravimetric power density of 6.49 kW/kg.

Due to the economic and environmental benefits, wind power is becoming one of the more promising supplements for electric power generation. However, the uncertainty exhibited in wind power data is generally unacceptably large. Thus, the data should be accurately evaluated by operators to effectively mitigate the risks of wind power on power system operations. Recognizing this challenge, a novel deep learning based ensemble approach is proposed for probabilistic wind power forecasting. In this approach, an advanced point forecasting method is originally proposed based on wavelet transform and convolutional neural network. Wavelet transform is used to decompose the raw wind power data into different frequencies. The nonlinear features in each frequency that are used to improve the forecast accuracy are later effectively learned by the convolutional neural network. The uncertainties in wind power data, i.e., the model misspecification and data noise, are separately identified thereafter. Consequently, the probabilistic distribution of wind power data can be statistically formulated. The proposed ensemble approach has been extensively assessed using real wind farm data from China, and the results demonstrate that the uncertainties in wind power data can be better learned using the proposed approach and that a competitive performance is obtained.

In order to better realize the plug and play function of various distributed energy sources (photovoltaic, storage batteries, etc.) in the DC micro-grid, improve energy conversion efficiency and improve DC side bus voltage performance. The layered control strategy introduced contains two layers: the new energy in the inner layer of the micro-grid is maximized by the maximum power tracking control, and the energy storage unit uses the voltage leveling control to ensure the stability of the DC side bus voltage; The bidirectional vector decoupling control includes voltage and current double closed loop control, and uses d-q coordinate axis transformation to control DC voltage and power factor to solve the problem of bidirectional flow of power during grid connection. This paper gives a detailed theoretical analysis and design method for each layer control. Simulation results demonstrate the feasibility and effectiveness of the proposed method.

A patented bidirectional power converter was studied as an interface to connect the DC-bus of driving inverter, battery energy storage (BES), and ultracapacitor (UC) to solve the problem that the driving motor damages the battery life during acceleration and deceleration in electric vehicles (EVs). The proposed concept was to adopt a multiport switch to control the power flow and achieve the different operating mode transitions for the better utilization of energy. In addition, in order to improve the conversion efficiency, the proposed converter used a coupled inductor and interleaved-pulse-width-modulation (IPWM) control to achieve a high voltage conversion ratio (i.e., bidirectional high step-up/down conversion characteristics). This study discussed the steady-state operation and characteristic analysis of the proposed converter. Finally, a 500 W power converter prototype with specifications of 72 V DC-bus, 24 V BES, and 48 V UC was built, and the feasibility was verified by simulation and experiment results. The highest efficiency points of the realized prototype were 97.4%, 95.5%, 97.2%, 97.1%, and 95.3% for the UC charge, battery charge, UC discharge, the dual-energy in series discharge, and battery discharge modes, respectively.

The mathematical model of three-phase LCL inverter has coupling term in dq coordinate system. At the same time, the traditional proportional integrate (PI) controller can only realize the no steady-state error control of the sinusoidal AC current in dq coordinate system. This requires highly accurate phase angles and complex coordinate transformations. This paper proposes a control strategy which uses the Quasi-proportional resonant (QPR) controller in the αβ coordinate system. Using the capacitor current as the inner loop realizes active damping and inhibits the resonance peak of LCL filter. The grid-connected current external loop control sine AC current non-static tracking. Design capacitance current feedback coefficient, the proportional coefficient of QPR controller and resonance gain coefficient with frequency domain analysis and zero-pole assignment. The parameter design method and the effectiveness of the control strategy are proved in the simulation and experiment.

This paper presents an effective design method of the electromagnetic interference (EMI) based on single-phase SiC MOSFET inverter. To ensure the design is targeted and effective, the equivalent noise source impedance of common mode (CM) EMI and differential mode (DM) EMI has been measured and calculated at some specific frequencies according to proper model. Then the parameters of CM part and DM part can be respectively design based on the source impedance. The EMI attenuation ability of the filter designed by this method has been compared to a traditional one in simulation and experiments. The simulation and experiment results have verified the effectiveness of the proposed method.

In single phase DC-AC systems, double-line-frequency power ripple appears at the DC side inherently. Normally a large electrolytic capacitor can be used to reduce the power ripple at the DC side. But there are several problems with this method as it decreases the power density and reliability of the converter. In addition, a double-line-frequency current ripple appears in case a voltage source serves at the DC side, which is undesired in specific applications. This paper proposes a single phase DC-AC DAB (dual active bridge) converter with an integrated buck/boost stage for power decoupling purpose under low power condition. The proposed active power decoupling method is able to completely eliminate the double-line-frequency power ripple at the DC side. Therefore, a constant DC current can be obtained for requirements in specific DC-AC applications.

Power inverter is an important part of a grid-connected system, LCL filter is widely used in the grid-connected inverter due to its harmonic attenuation performance and system stability. Compared with the traditional power device IGBT, SiC MOSFET has shown obvious advantages in higher switching frequency as a result of high power density. This paper first analyzes the effect of passive damping method on the resonance peak; then a double closed-loop control strategy with the inner loop of capacitor current and the outer loop of grid current is introduced; finally, the experimental platforms of SiC MOSFET inverter are built. The experimental results show that the double closed-loop control based on the LCL filter three-phase grid-connected inverter significantly reduces the system harmonics, and confirms the feasibility of the control strategy parameters design scheme.

The grid-injected current total harmonics distortion (THD) and electromagnetic interference (EMI) noise must be considered in a transformer-less grid-connected inverter for a more electric aircraft (MEA) system. This paper develops a procedure for the design of the magnetic components of the LCL filter used in harmonic control and EMI reduction of the silicon carbide (SiC) grid-connected inverter in the MEA. The LCL filter is designed with effective harmonic attenuation and a compact size. To meet the space constraint requirement, specific design attention is focused on a customized amorphous cored inductor, with a comprehensive study of the relationships of inductor winding with respect to EMI noise. Reduced THD and EMI are verified through experiments performed on a 30 kW, 230 V/400 Hz three-phase grid-connected inverter prototype with the LCL filter.

Power inverter is an important part of a grid-connected system. Compared with the traditional L or LC filter, LCL filter is widely used in the grid-connected inverter due to its harmonic attenuation performance and system stability. The resonance frequency of LCL filter is determined by the parameters ofits components. However, the inductance of inductor may change in accordance with the current flowing through it that would have an impact on the harmonic attenuation. This paper presents a nonlinear inductor model to determine the components of LCL filter on a three-phase grid-connected inverter system. The control method of the proposed system is a double current closed-loop control method. The current harmonic distortion and total harmonic distortion are analyzed and compared with the traditional linear inductor model. The experimental results show that the LCL filter can be designed more efficiently when the nonlinear characteristics of the inductor is considered.

Grid-connected inverter is an important part of the grid-connected system. Compared with the traditional L or LC filter, LCL filter has a better high-frequency harmonic attenuation performance. However, LCL filter has resonant peak, which has a great influence on the stability of the system. This paper first analyzes the effect of passive damping method on the resonance peak; then a double closed-loop control strategy with the inner loop of capacitor current and the outer loop of grid current is introduced; finally, the LCL three-phase grid-connected inverter with double-loop current control significantly reduces the Total Harmonic Distortion (THD), which verifies the feasibility of parameters design scheme of control strategy.

Power switch devices which base on wide band-gap (WBG) semiconductor, such as silicon carbide metal-oxide-semiconductor-field-effect-transistor (SiC MOSFET) and gallium nitride high-electron-mobility transistor (GaN-HEMT) perform superior performance as compared with silicon (Si) MOSFET in high switching frequency, high blocking voltage, and high temperature operation. In this paper, a series of characteristic test and comparative evaluation of power loss and efficiency which based on Si MOSFET (IPW65R080CFDA), SiC MOSFET (C2M0080120D), and GaN HEMT (TPH3212PS) with similar current rating are conducted in the single-ended flyback converter. It shows that the WBG switch devices can reduce more power loss, improve efficiency, and enhance more power density instead of Si MOSFET.

Incorporating cognitive radio technology into wire-less sensor networks enables the sensor nodes to use the idle channels to meet their communication demands, but the spectrum sensing process inevitably brings extra energy consumption. Since cognitive sensor nodes are generally low-powered with limited batteries, we consider a novel spectrum sensing scheme with combined clustering and censoring for saving energy. We minimize the energy consumed in spectrum sensing by designing the optimal sensing period and the energy detection thresholds. The simulation results show that, under the premise of ensuring the target sensing performance, the proposed scheme reduces the energy consumption effectively compared with the clustering only and the censoring only schemes.

Magnetic components are very important part in the power electronics system. Given weight and constrain space in the power converter, high power density converter is increasely required. In the whole system, half of the weight are the magnetic components. For the grid-connected system, the LCL filter is a necessary part to suppress the noise due to the high switching frequency transistor appeared. This paper introduce the procedure to choose the approximate magnetic components for the LCL filter of grid-connected system. Finally, the design procedure is carried out and verified in a grid connected power converter.

This paper presents the extraction of common mode (CM) and differential mode (DM) inductances of a common mode choke (CMC) using 3D finite element method (FEM). For optimal performance of the CMC, the effects of CM and DM currents on the magnetic core saturation are investigated. As the parasitic capacitance of a CMC is a critical parameter that affects its high frequency performance, the parasitic capacitances of the turn-to-turn and the turn-to-core capacitances of different winding layouts are also extracted for comparison. Finally, different core structures are modeled and simulated for performance evaluation.

A power factor correction (PFC) converter with interleaved multi-channel topology is gaining increasing attention due to its ability in reducing input and output current ripples, but an Electromagnetic Interference (EMI) noise filter is still required for suppressing the large high-frequency switching noise that could potentially degrade the input power quality of the supplying grid and cause malfunctions to other grid-connected systems. In this paper, a magnetic modeling of an interleaved PFC converter with an input differential mode (DM) EMI filter has been successfully implemented, which considers the nonlinear behavior of the inductive component in the EMI filter. The Jiles-Atherton (J-A) model is applied to describe the filtering inductor whose core displays saturation and hysteresis. The simulation results are verified with the experimental test.

The magnetic integration method of single-stage and multi-stage electromagnetic interference (EMI) filter was proposed with EE and EIE-type cores for single-phase grid-connected voltage-source inverter (VSI). Common mode (CM) and differential mode (DM) chokes were all integrated into a single magnetic core unit. The effectiveness of integrated single-stage EMI filter (ISSEF) and multi-stage EMI filter (IMSEF) has been verified by simulation and experiments. Taking a 500 W single-phase inverter as an experiment platform, the conducted EMI noise and core temperature distribution were presented. The EMI filter with integrated structure can significantly reduce system volume with satisfied EMI suppression ability.

The energy stored quasi-Z source cascaded H-bridge (ES-QZS-CHB) inverter is widely used in photovoltaic (PV) power generation system because of its unique advantages. However, the existing researches on ES-QZS-CHB inverter PV power system mainly focus on the transmission of active power, but pay little attention to reactive power, causing the ES-QZS-CHB inverter PV power system cannot compensate reactive power or improve system performance. This paper proposes a PV power generation and static synchronous compensator based ES-QZS-CHB inverter system, to implement the PV generation and reactive power compensation at the same time. Simulation and experimental results verify the system's excellent performance.