This paper develops an intelligent energy management system for optimal operation of grid connected solar powered electric vehicle (EV) charging station at workplace. The optimal operation is achieved by controlling the power flow between the photovoltaic (PV) system, energy storage unit, EV charging station (EVCS) and the grid. The proposed controller is developed considering the PV availability, grid loading and the EV charging load data. This information is modelled using Markov decision process (MDP) to develop a control strategy that eliminates the conventional problem of immediate recharging of energy storage unit after each EV charging by setting a target state of charge (SOC) level. This maximizes the use of PV power for EV charging and minimizes the impact on the grid. To test the operation of the proposed controller, a charging station powered by a 5kW PV system with 35kW energy storage unit connected to grid is developed through numerical simulations and experiment. The experiments were carried out for three different conditions under varying irradiance profile and load profile for multiple days. The results estimated the EV load and PV power and optimized the energy storage unit SOC between 0.3-1. Further, the energy management strategy minimized the impact of energy exchange between the grid and charging station by a factor of 2.

Partial shading (PS) conditions severely degrade the solar photo-voltaic water pumping system (SPWPS) efficiency. Due to partial shading, the output power of the photovoltaic (PV) array reduces, which minimizes the pumping output. Therefore, this paper designs a smart SPWPS for total cross tied (TCT) PV array. The design of smart SPWPS consists of irradiance, voltage, and current sensors. The irradiance sensor measures the real-time irradiation data of each module in the TCT connection. Based on real-time irradiation data, this paper proposes a dynamic reconfiguration algorithm with the help of switches that increases the PV array output power compared to normal TCT connection under partial shading conditions. The enhanced output power increases the water discharge of SPWPS. The voltage and current sensors are utilized for maximum power point tracking (MPPT) operation. Voltage by frequency (V/f) control with sinusoidal pulse width modulation helps to operate the induction motor smoothly. Further, simulation and experimental studies have been performed to validate the effectiveness of the proposed system under various PS conditions. The results obtained are encouraging as the reconfiguration algorithm improves the efficiency of the SPWPS.

Concerning about integration and high efficiency of the number of switches and the complexity of the drive circuits. So the number of switches should be as few as possible. By increasing switching frequency, the size of power inductor and filter capacitor can be significantly reduced. Switching losses and the effective operation range of duty cycle are two factors that restrict the increase of switching frequency. Literature [6] integrates same switch-units composed of diodes and MOSFETs of different converters, whereas literatures [7]-[9] insert specific switch-units into traditional dc-dc converters. Both the number of switches and passive components are decreased, but the switches work on hard switching condition. And the power transmission between three ports is in time division manner, hence duty cycle of switches is restricted. The topology proposed in [10] is derived from two cascade boost converters, and only two MOSFETs and two inductors are needed. The soft switching is achieved but the effective duty cycle of each switch is low. For satellite electrical power systems, a MPC is proposed in [11], which consists of unidirectional step-down converter and bidirectional PWM converter. There are two inductors and three MOSFETs but the switches suffer hard switching problem. In [12], auxiliary circuits contained coupled inductors and switches are required to achieve soft switching. However, the cost of components is increased and the power density is decreased. Moreover, the actual working conditions of the solar array should be evaluated in order to increase the response speed and the tracking accuracy of the MPPT algorithms and to cope with the problem of multipeak output power. At present, the most commonly used method is measuring short-circuit current and open-circuit voltage of the solar array from [13] and [14]. However, many of the PWM-based multiport converters like [4], [5], [10]-[12] need additional measuring circuit, which reduces the power density of the system. Bridge converters can be integrated with buck/boost converter by sharing bridge arm switches [15]-[18]. Bridge based MPCs, featuring soft switching and wide operation range, usually are partially isolated converters. To ensure the central symmetry of the voltage at the midpoint of the bridge arm, most bridge-based MPCs are of the full-bridge type. But for non-isolated converters, half-bridge is better. A bidirectional buck/boost converter and a half-bridge phase shift converter are

Interphase-microgrids formed by three islanded single-phase feeders in distribution systems are proposed in this paper. Loss of utility caused by natural and human-made disasters may isolate each residential subdivision from the utility. In this case, the household loads are supplied by distributed generation (DG) units which may not be enough to meet the load demand. This can lead to deviations in voltage and frequency, and the deviations may vary for each phase. The proposed solution is to form an interphase-microgrid by seamlessly interconnecting the islanded single-phase feeders. This interphase-microgrid can effectively balance the load demands and DG generation in distribution systems after losing the utility supply. This paper presents different case studies to demonstrate the viability of forming interphase-microgrids for residential distribution systems.

Stray inductance has great impacts on characteristics of power module and how to extract the inductance accurately is a significant challenge to guide the layout design and application of power module. The inductance during rapid gradient of current poses threaten to power module so the suitable stages for inductance extraction are recommended on account of dynamic characteristics. The existing method extracts inductance by two measure points and accuracy is low, which is influenced by measurement error significantly, so this paper proposes an adaptive stray inductance extraction algorithm, the essence of which is the least square method. The proposed algorithm applies least square method to extract stray inductance by fitting numerous sample points by double pulse test and eliminates the influence of measurement error because the residual obeys normal distribution same with measurement error. As a result, the proposed algorithm is with high noise immunity and accuracy. Finally, a multi-chips IGBT power module is tested under various conditions to verify the effectiveness of proposed method. Consequently, the error of extracted inductance is less than 5% and consistency is great.

This paper describes the design process of a high-power-density 100kW (34kW/L) traction inverter for electric vehicles, operating at an ambient temperature of 105°C. A detailed thermal analysis is performed based on the thermal behavior of the switching devices, and the results are used to estimate the semiconductor device junction temperature and to determine the requirements of the cooling system to achieve the target power level. A high-temperature gate drive board aiming for reliable system operation in electric vehicles is developed. An overcurrent protection scheme based on parasitic inductance between the power source and the Kelvin source of the power module has been implemented. A dc-link decoupling snubber circuit is designed numerically based on a detailed fourth-order high-frequency equivalent circuit of a double pulse test circuit. The approach to optimize the snubber circuit, not only for the voltage spike suppression but also for good thermal performance, is proposed. Finally, a hardware prototype with SiC power modules has been built and tested at 60kW continuous power and 100kW for 20 seconds at 105°C ambient temperature and 65°C inlet coolant temperature.

Modular multilevel converter (MMC) has been widely applied in HVDC systems. When MMC is applied in variable-frequency drives, the sub-module (SM) capacitor voltage fluctuation becomes serious at low output frequency. To suppress the fluctuation, a useful method is high-frequency injection. However, the high-value common-mode voltage would cause the insulation problem to the load. To address this issue, a hybrid MMC with a series of full-bridge SMs (FMs) inserted at the dc side is given. The high-value common-mode voltage can be eliminated by the additional arms. Meanwhile, the SM capacitor voltage fluctuation of the upper and lower arms of MMC system can be suppressed by an optimal high-frequency injection method. Simulation and experiment results confirm the validity of the given topology.

A power control scheme with maximum power point tracking based on solely voltage feedback control loops is proposed in this paper for a dc/ac isolated high frequency PV micro-inverter. The presented power circuit topology consists of an integrated continuous conduction mode (CCM) boost converter with an asymmetrical pulse-width modulation (APWM) controlled CLL step-up resonant converter and a half-bridge grid-side inverter. The presented topology is capable of achieving CCM input current and a wide range of zero voltage switching (ZVS) operation for the front-end stage. The proposed power control scheme, as well as the developed maximum power point tracking (MPPT) control technique utilize the resonant circuit's resonant capacitor voltage and the APWM input voltage of the resonant circuit only to achieve MPPT and to control the active power of the overall system. By doing so, a large electrolytic input filtering capacitor is not needed. This allows small size film capacitors to be used and improves the system lifetime expectancy. The theoretical analysis and the detailed descriptions of the proposed power control scheme for the presented PV micro-inverter are provided. Simulation and hardware results on a 220W with 120V, 60Hz output hardware prototype are presented to demonstrate the performance of the proposed PV inverter system.

The serious negative sequence (NS) issues and energy shortage problems are aroused by the single-phase 25-kV traction power supply system (TPSS) of high-speed railways. To achieve NS compensation and alleviation of energy demand, a TPSS with an integrated PV generation system is proposed. According to the structural characteristics of the TPSS and the PV system, a special topology and an NS compensation method are presented. Moreover, taking the NS control as the primary goal, three operation modes are classified by considering the load conditions of the TPSS and the output state of the PV system. After that, a coordinated control system with a central controller and multiple local controllers is proposed. The central controller can realize the flexible selection of operation modes and calculate the reference power. Meanwhile, the local controllers achieve the accurate tracking of the reference current and the stability of the DC link voltage by switching the control modes. Finally, the feasibility and effectiveness of the proposed system and the NS compensation method are verified by simulations.

Semiconductor power devices are the major constituents of any power conversion system. These systems are faced by many circumscriptions due to the operating constraints of silicon (Si) based semiconductors under certain conditions. The emergence and persistence evolution of wide bandgap technology pledge to transcend the restrictions imposed by Si based semiconductors. This paper presents a thorough experimental study and assessment of the performance of three power devices: 1200 V SiC cascode, 1200 V SiC MOSFET, and 1200 V Si IGBT under the same hardware setup. The study aims to capture the major attributes for each power device toward determining their realistic potential applications. The switching performance of each power device is studied and reported. As the gate resistance is a crucial factor in a power device characterization, an extensive analysis of hard-switching losses under different separated turn-on and turn-off gate resistances is also performed and discussed. To appraise the fast switching capability, the switching dv/dts and di/dts are measured and analyzed for each power device. Furthermore, insights are provided about the dependency of switching energy losses on the power device current and blocking voltage. This paper also focuses on evaluating the operations and the performances of these power devices in a hard-switched dc-dc converter topology. While using of 1200 V SiC Schottky diode in the converter design with each power device, the high switching frequency operations and efficiency of the converter are reported and thoroughly explored. The SiC cascode exhibited superior performance when compared to the other two power devices. The results and analyses represent guidelines and prospects for designing advanced power conversion systems.