Showing papers presented at "International Conference on Power Electronics Systems and Applications in 2015"

High power capacitive power transfer for electric vehicle charging applications

Abstract: This paper focuses on high power capacitive power transfer (CPT) for electric vehicle charging applications. The CPT system can achieve several kW power transfer through an air-gap distance of 150 mm with the dc-dc efficiency higher than 90%. Four pieces of metal plates are used as the capacitive coupler to build up electric fields and transfer power. A double-sided LCLC compensation circuit topology is proposed for the coupler to boost the voltage on the plates. The plates can be arranged vertically, instead of horizontally, to maintain the system power at rotatory misalignment conditions. The CPT system can also be combined with the inductive power transfer (IPT) system, in which the capacitors between the plates resonate with the inductors of the coils. Three prototypes have been constructed to validate the high power CPT system, which demonstrate that the CPT technology is suitable for electric vehicle charging applications.

Recent progress in developments of on-line electric vehicles

Abstract: Wireless electric vehicles (WEVs), classified into roadway powered electric vehicles (RPEVs) and stationary charging electric vehicles (SCEVs), are in the spotlight as future mainstream transportations. RPEVs are free from serious battery problems such as large, heavy, and expensive battery packs and long charging time because they get power directly from the road while moving. The power transfer capacity, efficiency, lateral tolerance, EMF, air-gap, size, weight, and cost of the WPTSs have been improved by virtues of innovative semiconductor switches, better coil designs, roadway construction techniques, and higher operating frequency. In this paper, fundamentals of WPTSs for RPEVs as well as recent progress in developments of on-line electric vehicles (OLEVs) that have been commercialized firstly in 2013 and made by KAIST, Korea are summarized. The fifth- (5G) and sixth-generation (6G) OLEVs, which can reduce construction cost and time for its commercialization, and the interoperability issue between RPEVs and SCEVs are addressed in detail.

Genetic Algorithm based Back-Propagation Neural Network approach for fault diagnosis in lithium-ion battery system

Abstract: Safety is important in a lithium-ion battery power system. It is necessary to adopt an effective fault diagnosis method to keep the battery power system in the good working status. In this paper, Genetic Algorithm (GA) is integrated to build a single hidden layer Back-Propagation Neural Network (BPNN) for fault diagnosis. In the process of training the neural network, GA is used to initialize and optimize the connection weights and thresholds of the neural network. Several faults are detected by the proposed GA optimized fault diagnosis scheme. Simulation results show that the proposed fault diagnosis scheme provides satisfactory results.

A bidirectional flyback cell equalizer for series-connected lithium iron phosphate batteries

Abstract: Cell equalization is a critical technology to enlarge battery pack capacity and prolong battery cycle life. A cell equalizer based on an isolated bidirectional flyback converter is introduced in this paper. Energy can be transferred from one cell to the pack or from the pack to some cell through a double winding transformer. An n-MOSFET and a milliohm resistor for current sampling are connected to each winding in series. According to the sampling current, the n-MOSFETs in both sides are switched on alternately. One is for inverting, and the other is for rectifying. Therefore, the converter achieves synchronous rectification, which contributes to higher energy efficiency. Meanwhile, the average balancing current can be set based on the sampling resistors. By the application of a controller IC for multi-cell battery stacks balancing, the implementation of the cell equalizer is simplified, and the reliability of the circuit is improved. A prototype is designed for a twelve-cell series connected lithium iron phosphate battery pack. Every cell can be charged or discharged individually at the same time, which accelerates the balancing process. Experiments have been conducted to validate the balancing circuit.

A control scheme for a High Speed Railway traction system based on high power PMSM

Abstract: The high power permanent magnet (PM) traction drive has recently been highlighted due to its promising qualities such as high efficiency and power density. For better performance, a robust, efficient and reliable control and driving scheme needs to be designed. In this Paper a control scheme is designed which based on Most Torque Per Ampere (MTPA) strategy to obtain high power density and is specially designed to achieve smooth transition between constant torque mode and constant power (field weakening) mode. In addition, a novel low-frequency pulse width modulation (PWM) scheme is designed to achieve smooth transitions between various fundamental-carrier wave frequency ratios while maintaining the synchronization between stator and rotor flux throughout the entire operation range. The validity of the scheme has been proved by simulation results and experiment is underway.

State-of-charge estimation of lithium iron phosphate battery using extreme learning machine

Abstract: Tracking the state-of-charge (SOC) is important for battery applications. A novel SOC estimation algorithm based on extreme learning machine (ELM) is proposed. Compared with the traditional neural network method, the ELM simplifies the computation procedure and shortens the learning time. A typical model of ELM is built for an 180Ah/3.2V lithium iron phosphate battery, and data acquired from cell discharge experiments under a series of current are contributed to model training and predicting. To evaluate the effect of ELM on SOC estimation, the back propagation (BP) neural network and the support vector machine (SVM) are taken into comparison. The results show that the ELM method provides a more accurate SOC. What is more important is that the speed of network training is improved greatly.

An adaptive modulation scheme for fundamental frequency switched multilevel inverter with unbalanced and varying voltage sources

Abstract: Stepped modulation operates at fundamental frequency allows the use of low speed switching devices and mitigates the switching loss and EMI concerns suffered by many other hard-switched inverters adopting carrier-based pulse-width modulation (PWM) such as space vector PWM and sinusoidal PWM. Half-height (HH) method is one of the simplest ways to compute switching angles of stepped sinusoidal output. Similar approaches have been utilized in digital-analog signal conversion and synthesis. However, there is limited research on HH-based modulation for power inverters. In this paper, a computational modulation scheme based on HH method was studied. The proposed modulation scheme is capable for real-time computation with most present microprocessors. This paper will demonstrate the implementation of the proposed modulation scheme at balanced voltage and the techniques of adaption to varying and unbalanced sources. Capability of having minimum total harmonic distortion (THD) under equal voltage sources of HH method was verified. The performance of the proposed modulation scheme was examined using numeric calculation and simulation with a 7-level cascade H-bridge inverter and the results are presented.

Development of the Equivalent Magnetic Circuit Model for a Surface-interior Permanent Magnet Synchronous Motor

Abstract: This paper presents an analytical method for analyzing the magnetic field of a Surface-interior Permanent Magnet Synchronous Motor (SIPMSM). The Equivalent Magnetic Circuit Model (EMCM) of the SIPMSM is established first according to the distribution characteristics of the main magnetic flux and leakage magnetic fluxes of the motor. On this basis, the methods for calculating various leakage magnetic permeances are determined according to the motor structure and thus the leakage magnetic reluctances of the magnetic circuit are obtained. A comparative analysis of the calculation results of the analytical method and the Three-dimensional Finite Element Method (3D FEM) reveals that those results are in good agreement, it shows that the EMCM has certain reasonability and feasibility. Compared with the finite element method, the analytical method has the advantage of easy and fast calculation, it can save a lot of time when analyzing many motor designs with different dimensions, and it can therefore be used as a powerful analytical tool during the design processes of SIPMSMs.

Large signal stability analysis of aircraft electric power system based on averaged-value model

Abstract: More electric aircraft (MEA) is using more electrical power on board and the stability analysis of the aircraft electric power system (AEPS) becomes more important. This paper presents a modeling study and stability analysis of the EPS for MEA. Averaging technique is used to model the aircraft EPS, which includes a generator, an autotransformer rectifier and an inverter-motor load. The proposed model is accurate and simple for the large signal stability analysis of MEA power system. Brayton-Moser mixed potential and Lyapunov stability theorems are employed to estimate the large-signal stability region of the system. Simulation results are used to verify the effectiveness and feasibility of the proposed analytical method.

The design and application of an unmanned surface vehicle powered by solar and wind energy

Abstract: The development of unmanned surface vehicles (USVs) for reconnaissance or other littoral missions is attracting increasing attention. In order to increase the sustainability of USVs, a new hybrid driving system powered by solar energy and wind energy is designed for the proposed USV. The developed USV is based on a catamarans prototype boat, and is equipped with a wing sail. In addition, the superficial of the USV is covered with PV panels for providing sustainable energy generation. The batteries based storage system is used for storing extra electricity as well as providing electricity for the control system and electrical system. To achieve tasks independently and intelligently, the USV is integrated with an automatic control system. The USV is discussed in detail, and some testing results are presented to validate its feasibility.

A hierarchical group control method of electrical loads in smart home

Abstract: With the development of smart home, the amount of household electricity loads is greatly increasing. How to effectively control these loads has been one of the most important issues in the research of smart home system. Keeping the total electricity loads under limitation would ensure the safety of users' electricity consumption. However, limiting the amount of electricity load or simply cutting the electricity off when it exceeds the limit will bring inconvenience to users. This paper proposes a hierarchical group control method of household facility, which classifies household electricity loads according to their importance and formulates a rule of cutting off when the total load exceeds the limitation. Based on the MATLAB software, calculating and simulating the appliances' working state by original Particle Swarm Optimization (PSO) has verified the correctness and effectiveness of the proposed group method. This method can be applied to current smart home control unit to improve the security and convenience of the system.

Simulation of thermal properties of the liquid metal batteries

Abstract: With the development of intermittent renewable energy technologies (such as wind and solar) large-scale access into the electric grid, a low cost high efficiency energy storage medium is indeed to greatly improve the ability of the power grid adopting the renewable energy., among all kinds of energy storage technologies, batteries have long been considered a very promising choice owing to their seldom pollution, high efficiency, low maintenance, and flexibility in power and energy characteristics, besides its long service life. Here we describe the liquid metal battery which is a newly developed and can be self-heated. This cheap and efficient energy storage medium will meets the specifications for power grid applications. This paper focuses to analysis the self-heated mechanism in this new battery, which is the vital factor to ensure the startup and reliability of the battery. The analysis is based on the finite element numerical methods with a three-dimensional thermal simulation model of liquid metal battery, and compares the temperature distribution under various current densities, different battery electrolyte sizes respectively. Simulation results show that both the current densities and the thickness of the electrolyte have a critical value above which the liquid metal battery can achieve a self-heating state. We also verify the simulation results theoretically from the view of mathematical formula, and reveal the ways to get self-heated for this battery.

Development of a 4-DOF SCARA robot with 3R1P for pick-and-place tasks

Abstract: The planar robot is very suitable for moving workpieces which are in high demand in industrial automation. This paper develops a 4 degree of freedom (4-DOF) selective compliance assembly robot arm (SCARA) robot with three rotary joints and one prismatic joint (3R1P) to realize pick-and-place tasks of the circular and rectangular workpieces. The structure of the robot is firstly presented. The kinematic model is then built, and the kinematic analysis is performed based on MATLAB. The trajectory planning is further implemented. A control interface is also designed via Visual C++ to control the robot for achieving pick-and-place tasks. The validity of the developed robot is finally verified through experimental results.

Design and construction of a DAB Converter for integration of energy storage systems in Power Electronic applications

Abstract: The paper studies the design and construction of a Dual-Active-Bridge isolated DC/DC converter for tying energy storage systems to the DC link of a Power Electronic Converter. Among the keystone applications of such configuration, grid support for power quality systems, on/off board battery charger systems for plugged-in hybrid electric vehicles or Charging Station systems outstand as the most interesting from the technical and economic points of view. All these applications allow for the development of the Microgrid concept and boost the advancement towards electrical transportation. The converter is analytically characterized, a control structure is developed to ensure a constant battery voltage with a fast stable ride-through during transient events, and an experimental test platform is designed to assess the studied modulation and control strategies under 2kW power level.

Static model of a 2×25kV AC traction system

Abstract: Transport system, and especially railways as a part of it, has a highly significant place in the modern world. Railway system has a lot of advantages, comparing to the other type of transport, such as: comfort, economy, better control on the travel time and schedule and less risk factors. Development of high performance computers, growing complexity of traction drives and power supplies made possible and, moreover, necessary to model railway systems in order to provide its efficient planning, design and maintenance. This paper introduces a basis of the traction system modelling for high speed railway systems. First, a brief review of existing traction systems is given. Second, a 2×25kV AC bivoltage network is explained in details. Finally, a mathematical model of the static AC system has been proposed.

Application of Cuk converter together with battery technologies on the low voltage DC supply for electric vehicles

Abstract: Electric vehicles (EVs) have becoming more and more popular, and although there is no doubt that motor is the key part of a functional EV, it is generally accepted that the battery is the critical component and a main obstacle of the development of EVs. In this paper, some advanced research and technology of batteries is presented and compared one by one, especially those adopted by flagship EV automakers. Some emerging batteries which have great potential for future EVs are also discussed. Based on this, the paper studies the application in EV of Cuk converter, which can be regarded as a combination of boost converter and buck converter, on the low voltage side DC supply electric vehicles together with the batteries, and even super-capacitors which have unique characteristics. Further research and design is given regarding to multi-switching of the DC-DC topology.

High frequency AC auxiliary power source for future vehicles

Abstract: High frequency AC power distribution system have been discussed for a few decades now. It finds applications in computer power supplies, aerospace power, lighting systems, micro grid and telecommunication equipment. This paper applies the high frequency AC power distribution system into a commercial vehicle. Prototype of a high frequency AC power source, rated at 500 VA with distribution frequency of 50 kHz, to be employed in a future vehicle for auxiliary power supply is designed and presented in the paper. DC voltage to the HF inverter is fed from a front-end hard switched boost converter. The converter-inverter system's performance is evaluated from the obtained simulation and preliminary experimental results.

Development of the three-dimensional scanning system based on monocular vision

Abstract: The emerging three-dimensional (3D) scanning technology based on computer vision is attracting more and more attention in industrial applications such as the 3D modeling of motors and automobiles. This paper develops a 3D scanning system using monocular vision to rapidly and automatically obtain the 3D dimension of the scanned object. The principle of the 3D scanning system is firstly introduced. The structure is then presented. The system consists of a camera, a line laser generator, and a rotation platform with a direct-current motor. The software of the system is developed based on C # and EmguCV library functions to realize image processing. Additionally, experiments are carried out through a fabricated prototype. Experimental results demonstrate that the developed system achieves the rapid acquisition for the 3D dimension of the scanned object and features simple structure, low cost, easy to extend, and rapid 3D reconstruction.

A new two-degree of freedom switched reluctance motor for electric vessel

Abstract: This paper introduces a new 2-degree of freedom (2-DOF) switched reluctance motor for an electric vessel. The configuration, operation principle and algorithm of the new motor are described in detail. Moreover, the electromagnetic characteristics have been illustrated by using finite element method (FEM), and the simulation of the electric vessel also has been realized. A modified control method has been suggested as the control scheme to ensure innovation and stability of the electric vessel's operation. Finally, the experimental results have suggested that the innovation and conveniences of the new electric vessel are better than that of conventional electric vessel, then the results of theoretical analysis and experiments has been proved the improvements of the electric vessel.

Study on black start strategy of multi-microgrids with PV and energy storage systems considering general situations

Abstract: In recent years, with the rapid development of the microgrid, the multi-microgrids (MMG) has become a new type of power grids, which is comprised of multiple microgrids (MG). It's necessary to study a safe and effective black-start strategy for the MMG, because MMG is more complicated than MG not only in the architecture but also in the control mode. This paper puts forward a control strategy with 3-level structure, based on the hierarchical control theory. In addition, the paper designs a black start strategy based on the serial restoration strategy, for the MMG with the PV and energy storage systems. The results of the simulation on PSCAD/ EMTDC, verify the effectiveness and feasibility of the MMG black start strategy.

Yaw angle control of a boxfish-like robot based on cascade PID control algorithm

Abstract: Because of the complexity of water environment, it is difficult to precisely model the fish robot system. Therefore, model-based attitude control algorithm is difficult to apply to the robotic fish. Cascade PID control uses the measurements of controlled variable and its derivative to constitute a double feedback loop. It can adjust the interference that influence the intermediate variable in advance and improve the dynamic quality and working frequency of the whole system. It is better than the traditional PID controller in anti-interference performance, rapidity, adaptation and stability. This article adopts the cascade PID algorithm to control the yaw angle of a robotic fish for the first time. This article innovatively uses a Kalman filter to eliminate the system angle error caused by periodic oscillation of robotic fish. A yaw angle control framework was proposed for biomimetic robotic fish. Based on the proposed framework, systematically yaw angle control experiments with the robotic fish were carried out in situations where the reference inputs were step signal, square wave and sine wave. Experiments showed that the robotic fish can accurately track the reference of the yaw angle in real time, verifying the effectiveness of the proposed algorithm.

High power high voltage gain interleaved DC-DC boost converter application

Abstract: DC-DC converter is usually an important part in many industrial applications. Especially, high power and high voltage gain DC-DC converter is now required in Fuel Cell Vehicle applications. This paper presents a high power high voltage gain interleaved DC-DC converter. It is a kind of non-isolated boost converter, which will raise a DC voltage of 120 V to a voltage of 700 V. The rating power of the converter may be at 60 kW. There are four modules of DC boost converter in this converter topology. All four modules are connected in parallel and controlled by 90 phase shifting degree to each other. The converter topology will be simulated by MATLAB/SIMULINK. The classical PI controller is selected for each current loop. Experiments on this converter are conducted based on a novel test bench, which uses a boost converter and a buck converter to form an energy cycle. Then experimental results will be studied in the lab for this converter.

Step-less voltage regulation on radial feeder with OLTC transformer-DVR hybrid

Abstract: On Load Tap Changing (OLTC) transformer acts to regulate the load voltage on load by increasing or decreasing the input power flow whereas, the capacity supported DVR regulates the voltage with reactive power transfer. As the OLTC operates in discrete steps, it brings in quantum jump in both the phase and magnitude of voltage at PCC, whereas sensitive load requires step-less operation. For step-less voltage regulation over extended range a hybrid combination of DVR with OLTC control of transformer is envisaged. The paper presents a simple and fast control strategy for hybrid control of both OLTC and DVR to desire stepless voltage regulation of the radial feeder under load perturbation and source side disturbances. A simple control algorithm is proposed which control the DVR and OLTC transformer to regulate the voltage in the radial feeder. Simulated results under MATLAB environment are presented to validate the effectiveness of control scheme.

Analysis and design of V-spoke ferrite interior permanent magnet machine for traction applications

Abstract: Due to the low residual flux density of ferrite magnets, flux-focusing and multi-layer configurations have been deployed to harness both the permanent magnet torque and reluctance torque. Here, a new configuration featuring a V-spoke rotor structure embracing a combined configuration of the conventional V- and spoke-shaped interior permanent magnet (IPM) machines is proposed for its superior torque density over equivalent counterparts. The magnetic open-circuit characteristic of the V-spoke machine is first analysed and compared with that of the equivalent V- and spoke-shaped machines. Then finite element analysis (FEA) simulations are performed for on-load conditions to confirm the superior performance of the proposed design. The frozen permeability method is carried out to provide further insights into the torque production mechanism. Operating efficiency, torque profiles and power-speed performance are also be investigated and evaluated to confirm the utility of the proposed ferrite machine design.

A research of the strategy of electric vehicle ordered charging based on the demand side response

Abstract: The rapid development of electric vehicle as well as photovoltaic generation leads measures to combine their advantages in urgent need. The appliance of the TOU price also brings about new challenge to the schedule of electric vehicle. This paper studies the method to minimize the electric cost of the users by the response to the photovoltaic generation and TOU price. Firstly, the model of the photovoltaic generation is proposed. Secondly, the model of optimization of electric vehicle is suggested. Lastly, optimization algorithm is utilized in this model. Simulation verifies the valid of the model.

Comparison of detection methods for power quality in micro-grid

Abstract: The micro-grid brings benefits for the economic development, but the transient power quality disturbances and harmonics generated by distributed power and grid-connected are inhibited to the development of micro-grid system. Detection and identification of these transient power quality disturbances are important. To circumvent this problem, the paper discusses the methods of power quality detection in frequency domain, mainly the Fourier transform, wavelet transform, HHT, S-transform and atomic decomposition as the main methods. It compares the advantages and disadvantages of these methods and analysis the power quality disturbance problems in micro-grid. By theoretical analysis and MATLAB simulation, it can be concluded that S-transform has high accuracy and well noise immunity in power quality detection, which provides an important reference to solve the problem of the micro-grid power quality disturbances.

Zero emission electric vessel development

Abstract: Emission from the vessel has not been taken serious in the past. Recently the concern has been intensified due to the fluctuation of oil price, mature in technology and commercial successful in other similar electric transportation such as train and road vehicle. Based on the modern power electronics, the technology is now ready to be used in vessel. Various type of vessel including boat, ship, tank and submarine are now ready for this revolution. The paper provide a design and technology discussion of the electric vessel development.

Modeling and control of DAB converter for solar micro-grid application

Abstract: In this paper, the modeling and control of the DC sub-grid, fed from Solar panels and integrated into the grid using dual active bridge (DAB) converters, is studied. The dynamic performance of the DAB converter depends on accurate modeling of the system. A small signal (SS) modeling of DAB converter is developed for the closed loop control and its dynamics are studied for different operating conditions. The simulation results of the proposed system are compared and it is found that the proposed system gives better dynamical response as compared to classical control system. An AC-DC hybrid micro-grid structure is modeled and its performance is studied. The performance of the dynamic system is simulated and the complete control algorithm is implemented in the laboratory.

Graph theory approach for a 2×25kV AC bivoltage traction system

Abstract: Electrical power system is one of the largest and essential nowadays engineering systems that is used in every single field of the modern life. Over the years, the power system advanced significantly, developing from local isolated networks with small-scale load and generation to large networks, such as power plants, railways etc. With increasing the size of the systems, power flow management has become an important task that requires an application of proper methods and techniques to solve power flow problem. In this paper, the authors have applied a graph theory approach as an effective method for solving the load flow in a 2×25kV AC bivoltage traction systems. Obtaining a static system, proposed method is able to overcome numerous problems in the system topology and dimensions.

Propulsion system design of electric vehicle

Abstract: This paper presents the systematic design methodology for the design of electric vehicle propulsion system. Power rating of three phase induction motor is calculated to achieve the pre-specified vehicle dynamic characteristics. The effect on electric motor power rating with variation of vehicle maximum speed is analyzed. Simulation results for vehicle dynamics are shown and validated. Furthermore, the obtained result is utilized to design a three wheeler electric vehicle for maximum speed of 50 km/hr.