Effects of Common-Mode Active Filtering in Induction Motor Drives for Electric Vehicles

Abstract—

This paper deals with the active common-mode (CM) voltage compensation in an induction motor drive where the inverter is supplied by a dc source, which is typical of vehicle applications. The CM voltage at motor terminals, creating a shaft voltage through the motor air gap with possible rise in bearing current, can endanger motor reliability and reduce its lifetime. Therefore, CM voltage filtering is desirable. On the other hand, the operation of an active filter has an impact on drive efficiency due to its specific losses and can affect the electromagnetic interference (EMI) emissions that are generated by the drive. Such effects are investigated in this paper. A detailed description of a CM active filter (CMAF) is presented. An analysis of the CM voltage and current on the motor ground connection before and after the introduction of the CMAF is performed. The power losses due to the CMAF operation are analyzed and experimentally evaluated. Furthermore, the EMI toward the vehicle dc power supply line is investigated. All phenomena are studied by simulation and experimentally. The simulated results “are obtained developing” a high-frequency circuit model of the drive system, including the CMAF, which is implemented using the PSpice software. To accurately perform the experimental tests, a new dedicated high voltage dual dc line impedance stabilization network (LISN) is designed and set up on purpose. The CMAF is found to be an effective solution for the increase in motor reliability and drive electromagnetic compatibility, and its operation does not significantly reduce drive efficiency. Moreover, the CMAF does not worsen the EMI toward the dc supply line. Therefore, its presence does not imply the need for additional filters with respect to the case where no CMAF is used. Simulated results are in good agreement with the experimental ones, confirming the validity of the proposed modeling of the drive system.

Proof-of-Concept of a Smart Fault Current Controller With a Superconducting Coil for the Smart Grid

Abstract—

The power grid, especially distribution grid, has been more complicated due to distributed generations (DGs) with renewable energy sources and the smart grid. The complexity changes two things in terms of a fault; higher prospective fault current and the temporal variation of sources and loads. To correspond to those remarkable changes, we propose a fault current controller (FCC) named “smart FCC.” The smart FCC consists of a superconducting coil with a freewheeling diode if necessary, four thyristors, and a control unit. Smart FCC can not only limit but also control the current when a fault occurs. The smart grid technology can provide so enough information that it is possible to estimate which level of limited current should be the best in the real-time situation of the grid. Based on a real-time calculation of optimal fault current using the smart grid monitoring technologies, this new device is always ready to adjust the fault current. In this paper, we introduce a concept of the smart FCC and prove the concept. Various topologies have been proposed and simulated. Finally, a case study on a distribution class of 22.9 kV smart FCC has been conducted based on a conceptional system design.

DESIGN PROCEDURE OF A PUSH PULL CURRENT-FED DC-DC CONVERTER

Abstract—

Some of the major drawbacks of Voltage-fed converter can be resolved by its Current-fed counterpart with its certain practical advantages. The recent increase in interest and use of current-fed converters calls for establishing a systematic design methodology. While some papers have provided useful insights to these converters, elaborate design steps are not available in literature. This paper presents complete design process of a push-pull current-fed converter. 

Buck Converter Design

PHOTOVOLTAIC-GRID INTEGRATED SYSTEM

This paper proposed solution for directly energizing of ac load throughout  Photovoltaic Solar Array during the daytime by applying so called variable voltage tracking system (VVT). The main function of VVT is to maintain the average output chopped voltage at fixed value irrespective of solar radiation rate, in turn the chopped voltage is converted into ac voltage suitable for grid-connected loads. This solution is realized by integrating both complementary buck-boost chopper and dc to ac converter. The ac-grid contributes to the load in two cases, first when there is a power shortage during the daytime due to weak irradiation rates, and second during the night time. The power estimator unit is used to determine the grid contribution intervals. 
This solution excludes the use of battery bank which is the main obstacle in massive use of solar energy due to their weight, short life time, maintenance and cost. Matlab/Simulink is used to simulate the proposed model, where the obtained simulation results confirm and justify the proposed approach for further study and looking for optimized solutions for cost reduction and energy savings. 

Generalized UPQC system with an improved Control Method under Distorted and Unbalanced Load Conditions.

Abstract-

Power quality has become an important factor in power systems, for consumer and household appliances with proliferation of various electric and electronic equipment and computer systems. The main causes of a poor power quality are harmonic currents, poor power factor, supply-voltage variations, etc. A technique of achieving both active current distortion compensation, power factor correction and also mitigating the supply-voltage variation at the load side, is compensated by unique device of UPQC presented in this paper and this paper presents a modified synchronous-reference frame (SRF)-based control method to Shunt active filter and instantaneous PQ (IPQ) theory based control technique for series active filter to compensate power-quality (PQ) problems through a three-phase four-wire unified PQ conditioner (UPQC) under unbalanced and distorted load conditions. The proposed UPQC system can improve the power quality at the point of common coupling on power distribution systems under unbalanced and distorted load conditions. The simulation results based on Matlab/Simulink are discussed in detail in this paper.

Optimal Placement of Custom Power Devices in Power System Network to Mitigate Voltage Sag under Faults

Abstract-

Voltage sag has been considered to be a serious power quality problem faced by many utilities. Placement of custom power devices may prove to be an effective remedy for solving power quality problems. In this paper, an Artificial Neural Network (ANN) based approach for optimal placement of Distribution Static Synchronous Compensator (DSTATCOM), Dynamic Voltage Restorer (DVR) and Unified Power Quality Conditioner (UPQC) in a power system network has been considered to mitigate voltage sag under faults. Voltage sag under different type of short circuits has been estimated using MATLAB/SIMULINK software. Optimal location of custom power devices has been obtained using a feed forward neural network trained by post-fault voltage magnitude of three phases at different buses. A comparative performance of DSTATCOM, DVR and UPQC in voltage sag mitigation has been studied to select most effective controller out of three controllers for the system. Case studies have been performed on IEEE 14-bus system. The effectiveness of proposed approach of placement of custom power devices has been established on the test system considered.