Showing papers presented at "International Power Electronics and Motion Control Conference in 2014"

A survey on comparison of electric motor types and drives used for electric vehicles

Abstract: In this study, Switched Reluctance Motor (SRM), Induction Motor (IM), Brushless DC Motor, and Permanent Magnet Motor (PM), and their drives have been compared with the efficiency, cost, weight, cooling, maximum speed, reliability, fault tolerance, power ratings, and vehicle acceleration time. Hence, a comprehensive literature research on motor types and their drives used in EV has been made. According to these researches, some conclusions have been obtained. It has been seen that PM BLDC motors and their drives are the most efficient and have high power density, brushless DC motors and their drives have low cost, IM is appropriate for controllability and cost, the weight of SRM is low, its reliability is high, it operates fault-tolerance and according to the acceleration time, its performance is better than IM and BLDC. Hence, SRM is the most appropriate motor for EV.

Implementation and analysis of a control scheme for damping of oscillations in VSC-based HVDC grids

Abstract: This paper proposes a simple method for damping of oscillations in dc grids based on Voltage Source Converters (VSCs). The damping effect is achieved by a control loop for counteracting measured dc voltage oscillations by acting on the active current reference of the ac-side VSC controller. The design of the damping method is supported by participation factor analysis and parametric sensitivities of a small-signal model representing an investigated test case. This investigated system is consisting of a single HVDC converter station connected to a dc cable equivalent and an ac grid. The validity of the developed small-signal model is verified by comparison to a simulation model including nonlinear effects of the investigated converter configuration. The small-signal model is then used to analyze the stability and dynamic characteristics of the system with and without the proposed active damping and to identify a suitable tuning of the damping controller.

Estimation of energy conversion processes in an electromechanical complex with the use of instantaneous power method

Abstract: The instantaneous power component analysis of energy conversion processes in all the elements of electromechanical complex power channel has been performed. It has been established that effective power is a quality measure for power processes in the system. An index of electromechanical complex power channel capacity has been offered. It has been proved that instantaneous power component, reflecting energy exchange processes in the system, causes decrease of the object power channel capacity.

A comparison of informative value of motor current and power spectra for the tasks of induction motor diagnostics

Abstract: In the article a theoretical basis of induction motor diagnostic methods based on motor current and motor power consumption spectra analysis is presented. Equations, describing current and power curves of motor working with most frequently caused damage types, were shown. A comparison of informative values of these signals has showed that power consumption signal contains greater number of diagnostic features, and their numeric values allows clearer recognition of damage feature in signal spectra.

Analysis of harmonic mitigations using hybrid passive filters

Abstract: With the recent development in the power electronic devices, the use of power electronics in controlled Variable Speed Drives (VSD) is increasing in industrial and domestic applications. These controlled VSDs provide many advantages and flexibility in those applications, but at same time cause harmonic distortion in the power system. In recent years, significant attention has been focused on line side harmonics because they overload power network infrastructure, affect quality of the grid, cause reliability problem in equipment and waste energy. Therefore mitigations of harmonics have been considered as important research issues in power system. A growing number of different harmonic mitigation techniques are available using active and passive components. In various industrial applications, passive harmonic mitigation techniques are used in low power drives due to the cost and size point of view. In this paper, a comparative analysis has been performed for various configurations of passive components and finally a hybrid passive filter has been optimized for the harmonic mitigation. In some applications such as micro-grid or standalone grid, there are strict requirements for Total Harmonic Distortion (THD) of voltage at the Point of Common Coupling (PCC). Therefore, a new harmonic factor (K) has been defined to calculate the THD based on current harmonics.

Modeling and control of a doubly fed induction generator for grid integrated wind turbine

Abstract: This paper presents the modeling, simulation and control of a grid connected doubly fed induction generator (DFIG) coupled with the wind turbine. Among all the renewable energy resources, wind energy is rapidly gaining interest of developed as well as underdeveloped countries. Due to the increase in demand of electrical energy and increase in environmental pollution the use of wind energy to meet the domestic and industrial power demands is essential and inevitable. The main benefit is the production of economically justified and ecofriendly energy in bulk quantity. Because of the irregularity of wind speed, the output of wind turbine varies and that is why, variable speed wind turbines are more practical these days. In order to integrate the variable output of the wind turbine with the power grid, doubly fed induction generators are used due to their inherent advantages like active and reactive power control, absence of large capacitive banks and improved power quality. A DFIG is modeled using the electric equivalent circuit and dq0 transformation along with the stator flux oriented vector control approach is used to decouple active and reactive power. Back to back power converters serve the purpose of controlling active and reactive powers at sub/super synchronous speeds. So the implementation of the proposed scheme ensures the constant output frequency and voltages with the control of active and reactive power and is highly suitable for grid integration in Distributed Generation (DG) Applications. The proposed scheme is implemented in SIMULINK / MATLAB environment and the simulation results validate the efficacy of the proposed scheme.

Reducing of energy consumption in public transport — Results of experimental exploitation of super capacitor energy bank in Gdynia trolleybus system

Abstract: Paper presents the result of test exploitation supercapacitor energy bank in Gdynia trolleybus system. In the first part of the article the basics of the regenerative breaking are presented and the construction and control strategy of the supercapacitor bank are described. The area of research and method of measurement are explained. In the second part of paper the results of tests and measurements are described. Emphasis was placed on the comparison of different methods of using regenerative braking energy. In the last part of the article conclusions are presented.

A novel harmonic elimination method for a three-phase diode rectifier with controlled DC link current

Abstract: Conventional diode rectifiers generate current harmonics which affects quality of power systems. According to the IEC61000 standards, different harmonic limits have been defined for broad range of products in which they have to fulfill the regulations. A cost effective solution to reduce current harmonic emission in low power motor drive systems (below 10 kW) is to use passive filters such as DC or AC chokes; but they are bulky and expensive filters and also input current Total Harmonic Distortion (THD) value depends on load profile. This paper presents an active harmonic mitigation technique with a novel current modulation method for three phase motor drive systems. Analysis and simulations have been carried out to verify the proposed method.

Lithium-ion battery installation in traction power supply system for regenerative energy utilization Initial report of effect evaluation after half a year operation

Abstract: Previously, some energy storage systems were installed to compensate for voltage drop and to avoid regenerative brake cancelation in d.c. 750V and 1.5kV traction power supply system in Japan. The fly wheel and Lithium-ion (Li-ion) battery, nickel metal hydride (Ni-MH) battery and electric double layer capacitor (EDLC) were used as a storage device. In East Japan Railway Company, Li-ion battery system was installed at HAIJIMA Substation (SS) on Ome Line and started operation on February 20 th , 2013. It is the first application of the energy storage system mainly not for voltage drop compensation but for regenerative energy utilization. In this paper, the effect of Li-ion battery system installed at HAIJIMA SS is evaluated based on the measured data during the practical operation and it is shown that it contributes to more than 5% reduction of total traction power supply at HAIJIMA Substation. The future plan of energy storage application is also mentioned.

A PSO optimized fractional-order PID controller for a PV system with DC-DC boost converter

Abstract: In this study, a fractional-order PID (FOPID) controller is designed to control a DC-DC boost converter in a PV-system. Because of the nonlinear V-I characteristic of a PV-panel, a power electronic interface is required to obtain a desired and fixed voltage level. In order to obtain the best system performance, parameters of the proposed controller are tuned by using Particle Swarm Optimization (PSO) algorithm. Both of the system responses with the FOPID and classical PID are tested under various power conditions by changing the load resistor and solar irradiation values. The simulation results are compared in terms of integral of time weighted squared error (ITSE) criterion, percentage overshoot (Mp) and rising time (Tr). The results show that the FOPID controller performs better performance than the classical PID controller.

Impedance spectroscopy for battery monitoring with switched mode amplifiers

Abstract: Impedance Spectroscopy is a well-known measurement technique for electrochemical systems, such as a battery half-cell. Once this method would be implemented in the battery management system and performed online during operation it could provide a monitoring system for the whole pack and increase its lifetime and safe operation. Current solutions are either inaccurate or too big, expensive and energy inefficient. The presented approach proposes a dual use of the battery charger which incorporates a switched mode amplifier to generate the stimuli current necessary to perform an Impedance Spectroscopy. The drawback of this method are the distortions associated with the modulation of the measurement frequency onto a carrier frequency. The influence of the DC-link voltage and the switching frequency on the on the total harmonic distortion are analysed. These theoretical results are compared with the ones from experiments. A custom designed switched amplifier was built up, specifically designed for performing Impedance Spectroscopy on a battery pack. This technology could allow impedance monitoring of every cell in the battery pack and make a better estimation of the state of the battery possible.

Cascade PI controller for single-phase STATCOM

Abstract: This paper presents state space model of singlephase STATCOM based on continues switching function. Continues switching functions for bipolar voltage source inverter (VSI) have been used to derive the transfer function for complete controller. Two proportional integral (PI) controllers which are a DC PI for DC link voltage control and an AC PI for alternating current control are implemented in cascade topology in reactive power compensation. Proposed control method has been analyzed in simulation by using MATLAB. Root locus technique is used to design AC PI controller parameters.

Harmonics issues of three-phase diode rectifiers with a small DC link capacitor

Abstract: This paper presents effects of DC link capacitor sizes in a three phase diode rectifier on input current harmonics at a system level. A small DC link capacitor generates a resonant frequency with a line inductor which can affect and increase the input current harmonics. According to IEC 61000-3-2 and IEC 61000-3-12 standards, low order current harmonics of a power electronic system should be controlled below a certain limits but at a power system level, voltage harmonics are important and should be reduced. SABER simulations have been carried out for a three phase motor drive system with different DC link capacitors and at different power levels in order to analyze the input current harmonics and the power quality of the power network.

Microgrid test-bed design with renewable energy sources

Abstract: This paper is dedicated to microgrid design by using several renewable energy sources (RES) together. The generator side contains the most widely used three types of RESs that are wind energy, solar energy, and fuel cells. The wind turbine is designed according to parameters of a 6.5kW commercial permanent magnet synchronous generator (PMSG). The solar plant that has 15kW rated power is constituted with string connection of 96 solar panels that has 170Wp rated power for each. The last generator of system is modelled according to parameters of a fuel cell that generates 10.5kW peak power. All the generation units are coupled over dc bus-bar by adjusting the voltages to 48Vdc. The dc loads are directly connected to bus-bar while the ac loads are supplied by ac bus-bar that is built by a three-phase 48V/380V-50Hz inverter. An RLC load with 10kW/250VA/250VAR power is connected to the output of inverter. The proposed test-bed can be improved by adding several generator and load types, and additional controllers, breakers, and contactors. In its current state, the proposed test-bed is considered as a preliminary design.

FPGA based Hardware-in-the-Loop (HIL) simulation of induction machine model

Abstract: The developed Hardware-in-the-Loop (HIL) Simulation was used to evaluate the performance of the electrical machinery driver systems in some cases which are very difficult or impossible to be tested in laboratory environment. By using this simulation environment, Embedded Control Systems (ECS) can easily be tested in a practically, cheaply and unhazardous way. In this study, we have developed a novel FPGA-based model of an induction machine in a single-chip in order to use in real-time simulation applications. In development steps, we have chosen Altera tools and used floating-point number system in model equations. The cycle time of the developed HIL Simulation environment is less than the previous studies thanks to FPGA based system modeling. According to the clock source of the development FPGA board, its value is about 1 microsecond. KeywordsHIL Simulation, FPGA Implementation, Real Time Modelling, Induction Machine Model

Permanent Magnet Synchronous Generators for Offshore wind energy system linked to Grid -Modeling and Control Strategies

Abstract: This paper describes the modeling and control of Permanent Magnet Synchronous Generator (PMSG) of 5MW for wind farms applications. The generators are linked to the grid by means of a fully controlled frequency converter, which consists of two three phase rectifiers, an intermediate DC-bus, and an inverter. The full system is connected to AC grid with phase to phase RMS voltage of 20kV. Proposed control strategies include the Maximum Power Point Tracking (MPPT) for the PMSG speed control, the active/reactive power control, and the DC-bus voltage management. To show the performances of the control strategies, some simulation results are presented and analyzed using Matlab/Simulink software.

Multi-level converters for low voltage high current applications: Issues, challenges and limitations

Abstract: Low voltage and high current power electronic converters are receiving increasing interest of both industry and academia for their application in stand-alone electric power generating systems. Multi-level converter topologies are well adopted solutions in high voltage applications, however benefits related to the reduction of current and voltage ripple as well to the decrease of switching power losses can be achieved also in low voltage systems. The paper investigates the application of converters with multi-level configurations in automotive systems and two cases are studied. The first case is a DC-DC converter for dual-voltage automotive architecture, while the second case is a low voltage three-phase rectifier for 1kHz AC fundamental frequency electrical generator in auxiliary power supply units.

Comparative study of investment and efficiency to reduce energy consumption in traction power supply: A present situation of regenerative energy utilization by energy storage system

Abstract: Railway is widely recognized as eco-friendly transportation method. For example, in Japan, CO2 emission per person per 1km by railway is about 18g while it is 164g for car and 108g for air plane. On the other hand, the total amount of energy consumption for railway operation is not small and it is important to improve efficiency of energy utilization in traction power supply system more. As one of the most possible solutions to improve energy efficiency in traction power supply system, a regenerative utilization is expected and some energy storage systems have realized in d.c. traction power supply system in Japan. In this paper, some methods to make use of regenerative energy are compared not only in the effect but also in the cost. Other existing choices for eco-friendly energy utilization such as energy saving at station and renewable energy utilization are also compared. In conclusion, regenerative energy utilization by energy storage system has a large potential and will be a practical choice even from the viewpoint of return on investment in the near future.

Speed sensor fault tolerant direct torque control of induction motor drive

Abstract: The paper deals with the fault tolerant Direct Torque Control of an induction motor drive Influence of the speed sensor faults to the properties of the DTC-SVM drive system is presented Control structure with and without outer speed control loop is analyzed Simple algorithmic mechanism of the speed sensor fault detection is described During the faulted conditions vector controlled drive is switched to the sensorless control structure with MRASCC speed and flux estimator Dynamical performance of the fault-tolerant vector control system (FTDTC-SVM) with the current-type MRAS estimator are tested in simulation and in the laboratory set-up with 50kW machine Control structure is checked under faulted and post-fault conditions, in low speed and in field weakening regions

Method of estimating precise piston stroke of linear compressor driven by PWM inverter

Abstract: Linear compressors have been used in cooling apparatuses such as house refrigerators and portable coolers due to their high efficiency. The stroke of a free piston in a linear compressor driven by PWM inverter can be estimated by integrating the back electromotive force (EMF) of a linear permanent-magnet synchronous motor (LPMSM), which is used to drive a piston. However, it may be saturated due to dc offsets in measured motor voltage and current. The method for estimating precisely the piston stroke by using both the high-pass filter (HPF) and adaptive all-pass filter (APF) is suggested. The HPF is used for removing dc offset in the back EMF, and the resonance frequency of an adaptive APF is controlled in order to adjust the phase of back EMF to -90° under inverter frequency variations. Through simulation and the experimental results, it can be verified that the piston stroke has nearly sinusoidal waveform without any dc offset.

Automated over speeding detection and reporting system

Abstract: The aim of project is to design an automated speed detection system which can detect the speed of vehicles and if over-speeding occurs, extract the license number of vehicle and send it via email to Toll Plaza to charge fine. The system is designed for Punjab license plates which are currently implemented in Pakistan. Doppler effect phenomenon is used for the speed measurement. If over-speeding is detected, a camera automatically captures the picture of the vehicle and Digital Image Processing (DIP) techniques are applied to extract the license number. MATLAB is used for image processing. Afterwards, the extracted license plate number is sent via email to Toll Plaza. The results show that the proposed system successfully detects over speeding, extracts the license plate, has high performance and can be deployed on roads to check for over speeding.

A three-phase three-level NPC inverter based grid-connected photovoltaic system with active power filtering

Abstract: This paper presents a three-phase three-level neutral point clamped (NPC) inverter based single-stage gridconnected photovoltaic (PV) system with shunt active power filter (APF) functionality. The proposed system can perform both the maximum real power injection with the perturb and observe (PO active power filter; grid connected; multilevel inverter; maximum power point tracking.

Modeling of Photovoltaic Solar Array under Different levels of partial shadow Conditions

Abstract: Different methods of configuration have been formulated regarding photovoltaic solar power by employing several techniques. This has been done because of the varying conditions so that the loss of power can be minimized. The main factor which decreases energy output of the photovoltaic PV solar systems is partial shadowing. The way the energy output of partially shadowed arrays varies with the system configuration used, has been studied extensively. A huge degree of disorder still exists, particularly with respect to the best modularity grade for these systems. There are two distinct sub-divisions in the systems implemented in the reconfiguration mechanism: reconfigurable solar arrays, and a switching matrix to do a reconfiguration. Using different methods, the proportions of shadowing obstructions were noted to allow for calculation of the likely shadowing losses. The outcomes of this paper on modeling and monitoring are used to evaluate the photovoltaic system with respect to shadowing losses with different levels and their reliance on the system configuration are selected. It has been found that power loss because of varying conditions is majorly due to the decrease in radiance occurring on the photovoltaic array and can be avoided through selecting the suitable configuration and connection. The simulation results show that the output characteristics of the simulator presented better results with that proposed model.

Output voltage regulation based on P plus resonant control in islanded mode of microgrids

Abstract: This paper investigates the inverter output voltage regulation method for islanded mode of microgrids. When DG (distributed generation) based inverters operate in islanded mode, the inverter can supply the full local load demand. Hence, the microgrid can be defined as a voltage source and regulate the output voltage. If an inverter supplies the power to the nonlinear and unbalanced loads, it generates the high order harmonics to the output voltage. Therefore, in this paper, P+multi resonant control which has large gain on the narrow band of specific frequency has been considered additionally for the performance improvement of output voltage regulation instead of the simple fundamental component control. Furthermore, the controller design method which satisfies the stability and performance of the system depending on the control gain parameters has been suggested after considering the effect on system. Improved THD performance of P+multi resonant control is verified through the PSiM simulation. It is also compared and analyzed with the fundamental component PI method and the PI method with harmonics compensation.

Analysis of LLC Resonant Converter with Current- Doubler Rectification Circuit

Abstract: In this paper, LLC series resonant converter with current-doubler as a rectification circuit for secondary side is proposed. The current-doubler circuit is generally used for the high voltage input and low voltage output application to get high efficiency characteristics with reduced transformer turn ratio. However, an inductive circuit is not used in a secondary side for the LLC series resonant converter generally. When there is inductive circuit like current-double on the secondary side, the resonant characteristics are changed. In this paper, LLC converter with the current-doubler using coupled inductor is proposed. We verify that the secondary side current-doubler using coupled inductor is not affect to the resonant characteristic of primary LLC by the mathematical analysis. Finally, the analysis results are proved by the simulation and experiments.

Dynamic Emulation of Mechanical Loads with Backlash Based on Rapid Control Prototyping

Abstract: The paper discusses advanced control of a dynamometer performing dynamic emulation of mechanical loads. Assumed is certain class of nonlinear load with backlash. Paper presents and describes the basic control structure, which can be used for validation of speed algorithms and its practical implementation with rapid control prototyping. Validation of experimental results against the simulations has been performed with experimental test bench containing permanent magnet DC machines and DC-DC converters with high sampling times in current control loops.

Performance improvement of induction motor drive using simplified FLC method

Abstract: This paper presents the improvement method for simplified Fuzzy Logic Controller (FLC) for Induction Motor Drive. This method is aimed to enhance performance for variable speed drive performance in a rated forward and reverse operation. The implementation of simplified rules based is able to reduce the computational burden and memory space limitation. However, the speed performance shows some degradation with regards to simplification process. Thus, the propose improvement method is made to increase the error gain parameter. The membership function (MF) domain for error is increased from nominal 1 to 2. It increases the torque current and improves the speed response. The speed control is applied to the indirect Field Oriented Control method fed with Space Vector Pulse Width Modulation (SVPWM). The real time implementation is done using dSPACE DS1103 controller. The performance results are compared between simplified rules method, simplified rules improvement method and Anti-Windup Proportional Controller (AWPI). The results show improvement in terms of rise time, overshoot and settling time compared to its counterparts.

Finite-set model predictive control and DC-link capacitor voltages balancing for three-level NPC inverters

Abstract: This paper presents a finite control set model predictive strategy for a three-phase, three-level Neutral-Point-Clamped (NPC) inverters with resistive-inductive load (RL-Load). This strategy allows for fast load current control while keeping the balance of the DC-link capacitor voltages. The system performance with a prediction horizon of one sample time and the dynamic response of the system with step change in the amplitude of the reference are investigated. The output currents and DC-link capacitor voltages are sampled and predicted for the next sampling time for each valid switching state of the inverter. The error between the predicted and reference current values and also the error between the capacitor voltages with respect to the reference value are obtained to minimize the cost function by choosing the appropriate state's switching signals and then applied to the converter. The simulation is carried out using MATLAB/Simulink with PSIM software. The co-simulation results show that the proposed control achieves high performance and high degree of robustness while balancing the DC-link capacitor voltages.

Active power filter with common DC link for compensation of harmonic distortion in power grids

Abstract: The growing number of consumers representing non-linear loads has led to an increase in the level of harmonics and poor power quality. It is not news to apply active power filtering (APF), but the drawback is the lower efficiency and complexity. The described here active power filter control system is simpler and more efficient. It is based on a relay current regulator and its converter uses the existing DC bus of the rectifier. The theoretical basis of the APF is described. A model of the proposed APF (with its suggested control system and the common DC link) is simulated in Matlab. The result of this simulation demonstrates that the level of the Total Harmonic Distortion (THD) of the input current is less than 3 %. The input current matches the phase of the input (mains) voltage: i.e. the consumption of reactive power from the grid is minimized. The simulation is confirmed by experimental study of the APF with Common DC Link. The corresponding results are provided.