Showing papers presented at "International Power Electronics and Motion Control Conference in 2010"

Fault-Tolerant Operation of a Battery-Energy-Storage System Based on a Multilevel Cascade PWM Converter With Star Configuration

Abstract: This paper focuses on fault-tolerant control for a battery-energy-storage system based on a multilevel cascade pulsewidth-modulation (PWM) converter with star configuration. During the occurrence of a single-converter-cell or single-battery-unit fault, the fault-tolerant control enables continuous operation and maintains state-of-charge balancing of the remaining healthy battery units. This enhances both system reliability and availability. A 200-V, 10-kW, 3.6-kW·h laboratory system combining a three-phase cascade PWM converter with nine nickel-metal-hydride battery units is designed, constructed, and tested to verify the validity and effectiveness of the proposed fault-tolerant control.

The Qi wireless power standard

Abstract: To enable a wide use of wireless power applications, the wireless power consortium has developed an industry standard to achieve interoperability between products that will carry the Qi logo. This paper introduces the Qi wireless power standard, explains the basic decisions that has been made in the process and provides a preview and short explanation of the system.

Trends in power electronics and control of renewable energy systems

Abstract: The electrical energy consumption continues to grow and more applications will be based on electricity in the next decades. We can expect that more 60 % of all energy consumption will be converted and used as electricity. It is a demand that production, distribution and use of electrical energy are done as efficient as possible. Further, emerging climate changes argues to find future solutions which also are sustainable. Two major technologies will play important roles to solve parts of those future problems. One is the change the electrical power production from conventional, fossil (and short term) based energy sources to renewable energy sources. Another is to use high efficient power electronics in power generation, power transmission/distribution and end-user application. This paper discuss trends of the most emerging renewable energy sources, wind energy and photovoltaics, which by means of power electronics are changing the future electrical infrastructure but also contributes steadily more to non-carbon based electricity production. Most focus is on the power electronics technologies used. In the case of photovoltaics transformer-less systems are discussed as they have the potential to obtain the highest efficiencies. It is concluded the both wind power and photovoltaic technologies are steadily more cost effective as well as contribute rapidly to the total installed electrical power.

Low voltage ride through capability of a 5 kW grid-tied solar inverter

Abstract: Distributed power generation systems (DPGS) such as wind and solar become more and more widely spread. As a consequence grid operating companies demand system services. As part of the general fault ride through (FRT) requirements this paper deals with low voltage ride through (LVRT) capability of a three-phase-four-wire grid-tied solar inverter. The standard system will be described and necessary changes to the control such as positive (PS), negative (NS) and zero sequence (ZS) separation, a stable phase-locked-loop (PLL) as well as voltage support by means of reactive current as well as stress factors to the hardware will be identified.

Influence of EV on grid power quality and optimizing the charging schedule to mitigate voltage imbalance and reduce power loss

Abstract: The penetration of Electric Vehicle (EV) on the Indian grid and its positive impact can be seen if the EV's are co-ordinated. The co-ordinate charging and discharging of EV's can improve the voltage profile and reduce the power transmission loss. Primary distribution of Guwahati City is simulated using actual data. Voltage profile and transmission loss have been analyzed considering various levels of EV penetration and charging patterns. It is shown that coordinated charging and discharging of EV's on the grid will flatten the voltage profile of a bus as well as reduce the power loss.

Modulation of Modular Multilevel Converter for HVDC application

Abstract: This paper deals with the scalable and transformerless Modular Multilevel Converter (MMC). A new modulation algorithm for this converter is presented, together with a Matlab-Simulink simulation based validation, of eight sub-module single phase MMC. In addition, the capacity of the proposed modulation to operate at high power applications with high number of sub-modules is demonstrated, by means of a simulation of a HVDC application with characteristics: 200 MW, 200 kV, 100 submodules/phase.

Kinetic energy recovery on railway systems with feedback to the grid

Abstract: Several proposals for using of power derived from regenerative braking in railway systems are available. We present an energy recovery system with feedback to the distribution grid based on a new converter topology; the dimensioning methodology of the system is based on real data intake and validated simulations. The new converter topology presented is based on the connection in cascade of a DC/DC elevator to a 3-phase inverter. This way, the system is freed from the limitations imposed by voltage fluctuations in the grid, allowing maximum recovery at minimum catenary's voltages. For more information please visit

Development and control of an integrated and distributed inverter for a fault tolerant five-phase switched reluctance traction drive

Abstract: A concept of an integrated and distributed inverter for switched reluctance machines is introduced. The application at hand is an outer-rotor direct drive designed for railway traction applications. A five-phase switched reluctance machine (SRM) was developed and is used to demonstrate the function of the integrated and distributed inverter. The distribution is achieved by supplying each phase coil with its own modular inverter. Each inverter module is placed evenly around the end of the stator stack next to its dedicated coil. This increases the redundancy of the drive significantly. The likelihood of phase-to-phase faults is reduced, because no overlapping end-turns are necessary. Also, the integration of machine and inverter is simplified, because the semiconductors can be evenly distributed around the machine. The concept reduces the amount of terminals between drive and vehicle to communication, power supply and cooling, independent of the number of machine phases. With the integrated and distributed inverter new control strategies can be developed to influence machine vibration and radiated noise. In this paper the design of the prototype, the direct torque control of the five-phase machine and the behavior in case of a fault inside a module is analyzed.

Comparison of linear voice coil and reluctance actuators for high-precision applications

Abstract: This paper concerns the comparison of three linear reluctance actuators and four voice coil actuators for high-precision applications. The short-stroke actuators with reasonably low variation of the force are optimized on actuator mass and power dissipation. For actuators with a significantly high force variation, the configuration is modified with the objective to improve the actuator properties for high-precision applications. Finally, the comparison is made on performance regarding, force, mass, losses and stiffness.

Observer for the rotor temperature of IPMSM

Abstract: In this paper an observer for the rotor temperature of an IPMSM, as commonly used in automotive applications, is presented. The observer is based on a flux observer utilizing the fact that the permanent magnet flux is temperature-dependent. Simulation and experimental results show good performance.

Transformer based voltage sag generator to perform LVRT and HVRT tests in the laboratory

Abstract: A transformer based voltage sag generator to test renewable energy systems is presented. Design considerations concerning overvoltages and overcurrents during switching action are adressed. Measurement results of a 30 kW laboratory prototype testing a line side PWM converter and a DFIG are presented. Both measurement results for investigations on the transformer based sag generator at the line side converter and the DFIG show the superb functionality of the sag generator. Voltage dips of variable magnitude, duration time and fault type can be generated to perform certification of LVRT capability. The device is also able to perform HVRT tests.

Why is sliding mode control methodology needed for power converters

Abstract: A review of the state of the art in the sliding-mode control of DC-to-DC switching converters is presented. The method of the equivalent control is illustrated in the design of a two-loop control for the voltage regulation of a buck-boost converter. The theoretical predictions are validated by means of PSIM simulations. Prospective applications of the method reported are also discussed.

Design of fractional order PID controller for boost converter based on Multi-Objective optimization

Abstract: This paper proposes the theory and application of a new designing method of the Fractional Order PID (FOPID) controller for boost converters. FOPID is a PID where the derivation and integration orders are of fractional order rather than integer. A FOPID is an extension to classic integer order PID controllers, that potentially promises better results. The method is based on the use of a Multi-Objective optimization evolutionary algorithm called Strength Pareto Evolutionary Algorithm (SPEA). Other controller methods cannot guarantee a good start-up response but the proposed method can provide an excellent start-up response besides desired dynamic response. The optimum fractional order PID coefficients for the desired control objectives are included and designers can implement each of them based on objective functions priority. A comparison between the optimum integer order PID controller and optimum fractional order PID controller is presented in the paper. The simulation and some experimental results prove the superiority of the fractional controllers over the integer controllers.

Modelling, simulation and control of Modular Multilevel Converter

Abstract: This paper describes first the mathematical model of the Modular Multilevel Converter with n submodules based on differential equations. Secondly, by using this model the simulation block diagram in Simulink is presented. After that, the special output AC voltage control of this converter is analysed, considering the capacitors' voltage control loop that usually is included in this topology. The modulation that also performs the capacitors' voltage balancing is not deeply studied in this paper. Finally, simulation results show that the proposed model can be useful to simulate the MMC topology with a large number of submodules, while on the other hand, the proposed AC voltage control is valid to regulate the total voltage of the converter capacitors as well as to exchange sinusoidal currents at any operation mode.

Multiphase machines in propulsion drives of electric vehicles

Abstract: Multiphase electric drives have been recently proposed for applications where the highest overall system reliability and power distribution per phase are required. The propulsion drive of an Electric Vehicle (EV) is one of these applications. This paper deals with the use of a five-phase induction machine in the propulsion module of EVs, where the viability of a Predictive Torque Control method (PTC) is analyzed. Simulation results are provided to illustrate the potential of the method, showing fast speed response and low torque ripple.

Additional losses in permanent magnet brushless machines

Abstract: The aim of the paper is to analyze the additional Joules losses in permanent magnets. The stator slot openings gives rise to changes in the magnetic flux density in permanent magnets (PM) of the rotor brush-less direct-current (BLDC) machine while the machine is rotating. The final consequence of these changes are induced eddy currents in PM and further additional power losses. The 3D time-stepping finite-element analysis is used to analyze this phenomenon. The induced eddy-current distribution in PM and the resulting power losses are calculated at different number of permanent magnet axial segmentation.

New Masterless Modular Current-Sharing technique for DC/DC Parallel converters

Abstract: This article presents a new Masterless Modular Current-Sharing (MMCS) technique. Current-sharing modules are identical and placed in a daisy chain configuration. Unlike classical current sharing which consists in comparing each phase current to a global computed average value, the presented masterless approach computes local current average values. Phase currents' balancing is achieved by comparing each phase current with the average value of its adjacent phase currents. This technique is validated by a mathematical demonstration and compared with the classical current sharing technique. MMCS approach is adapted to DC/DC Parallel converters with coupled inductors. Such topologies require extremely precise current-sensing technique. An accurate differential current-sensing technique with fluxgate sensor is proposed and applied to MMCS technique. Filters design and its architecture for current sharing loop are explained. Finally, experimentation on a six-phase DC/DC converter with coupled inductors is achieved and validates both MMCS and differential current sensing techniques.

New bi-directional DC/DC converter for supercapacitor interfacing in high-power applications

Abstract: This paper presents a new bi-directional DC/DC converter for supercapacitor interfacing in high-power applications. The converter acts as a VSI-based step-down DC/DC converter during the supercapacitor charging mode and as a qZSI-based step-up DC/DC converter during the energy recovery mode. To provide voltage matching and galvanic isolation the medium frequency transformer was implemented. To ensure higher voltage boost of the SC voltage during the discharge the qZSI with a two-stage quasi-Z-source (qZS) network was introduced. The paper analyzes and discusses the operation of the new converter mostly concentrating on the energy recovery (boost) mode. The operation of the two-stage qZS-network is analyzed in detail. Guidelines are presented for the new converter design. Finally, theoretical background was verified by the simulations.

Parameter extraction of battery models using multiobjective optimization genetic algorithms

Abstract: To simulate electric vehicles, appropriate battery models are required. In this work a model of the battery and a methodology for determining the parameters of a battery model using the catalog data of the batteries and Multiobjective Optimization is proposed. The technique is applied to different battery types and the results are presented.

More-electric aircraft electrical power system accelerated functional modeling

Abstract: The development of future more-electric aircraft (MEA) is a major trend in modern aircraft electric power system (EPS) engineering that results in a significantly increased number of onboard loads driven by power-electronics Development of appropriate EPS architectures, ensuring the power system integrity, stability and assessment of overall system quality and performance under possible normal and abnormal scenarios requires extensive simulation activity The increased use of power electronics can make the simulation of the large-scale EPS impractical due to enormous computation time or even numerical non-convergence due to the model complexity Hence, there is a strong demand for accurate but time-efficient modeling techniques for MEA EPS simulations The paper reports the development of a functional models library capable of significant improvement in simulation time whilst maintaining good accuracy up to a specified frequency range The application of the library is demonstrated on the example study of the performance of a twin-generator example EPS under both normal and faulty regimes

Bluetooth wireless communication and 1-wire digital temperature sensors in synchronous machine rotor temperature measurement

Abstract: This paper addresses the usage of digital temperature sensors in rotor temperature measurement. A rotor temperature measurement system had to be developed because of the complete synchronous machine thermal analysis. Rotor temperatures are measured using multiple DS18B20 digital thermometers and sent via a wireless link to the host. The measurement system has been mounted on a 400 kVA synchronous generator and the temperature measurements in rotation are presented.

Half-controlled-converter-fed open-winding permanent magnet synchronous generator for wind applications

Abstract: The configuration and control of two cascaded half-controlled-converters (HCC) designed for use with an open-winding permanent magnet synchronous generator (PMSG) wind turbine are investigated in this paper. The system is modeled and simulated in Simulink with the assistance of PLECS. The simulations results demonstrate that by using speed-control-based hysteresis current regulator, pure sinusoidal phase current waveforms can be achieved in the machine windings at various power factors. Compared to an open-winding PMSG fed by two cascaded voltage source converters, the proposed system requires fewer switches but provides identical excellent performance and good fault tolerance. The proposed system is also free of shoot-through issues. Although HCC allows only unidirectional power flow, this is typically not an issue in the wind power applications.

Dynamic terminal characteristics of a photovoltaic generator

Abstract: Photovoltaic (PV) cells have non-linear electrical characteristics with only one operating point at which the maximum available power can be extracted. This is called the maximum power point (MPP). In order to maximally utilize the energy of solar radiation by using PV generators, they must be forced to operate at their MPP. This is done by using interfacing devices, which are capable of changing the operating point of PV generators and feeding the maximum electrical power to the loads. Although the static electrical characteristics are important when designing a PV generator, the operation of the interfacing devices is also highly affected by the dynamic characteristics of the PV generator. This paper investigates the dynamic properties of PV generators especially from the point of view of the interfacing devices used between the PV generators and the loads. These loads can be e.g. an electrical grid in case of grid-connected generators or batteries in stand-alone applications.

Implementing current-fed converters by adding an input capacitor at the input of voltage-fed converter for interfacing solar generator

Abstract: The concern on observed climate change has increased the utilization of renewable energy sources. The harvesting of solar energy is recognized as one of the key issues in reducing green house gas emission. Reliable solar-energy systems composing of solar arrays and their interfacing converters are of prime importance in uninterrupted solar energy production. The interfacing maximum-power-point converters are implemented usually by modifying the conventional voltage-fed converters. Actually, the modifications change the converter into a current-fed converter with corresponding steady-state and dynamic properties. The paper investigates the true properties of these transformed converters based on theory and practical measurements. As an example a direct-duty-ratio-controlled voltage-fed buck converter is shown to be transformed into a current-fed boost-type converter.

Hardware-in-the-loop testing of PV control systems using RT-Lab simulator

Abstract: This paper presents a testing system for power converters control units. A hardware-in-the-loop test bench is designed for assessing control unit performances. A photovoltaic generator, coupled with a boost circuit, is software-simulated within a real-time environment, RT-Lab and coupled in closed loop with the physical control unit to be tested.

Comparative study on power conversion methods for wireless battery charging platform

Abstract: In this paper, four different power conversion methods (voltage control, duty-cycle control, frequency control and phase-shift control) are compared for wireless power transfer applications by considering the energy transfer efficiency, electromagnetic interference, stability, and implementation complexity. The phase-shift control is found to be the optimal scheme with good efficiency and low electromagnetic interference. Its constant frequency feature is also within the framework of the new international wireless charging standard called ‘Qi’. A high system efficiency of 72% for 5W wireless charging applications has been achieved practically.

Analysis of vehicle to Grid concept in Indian scenario

Abstract: There seems to be a huge potential of electric vehicles in India by 2020, thus Vehicle to Grid concepts can be easily implemented in Indian scenario. In this paper, various possibilities and their impacts on power scenario for implementing Vehicle to Grid (V2G) have been explored in Indian context by considering the actual data. It has been established that electric vehicles can meet the peak demand by taking the power at off peak time and supplying the power back to the grid in peak hours.

Power sizing factor design of central inverter PV grid-connected systems: A simulation approach

Abstract: This paper presents a simulation approach which can help in the preliminary power sizing design of a grid-connected PV system based on a single inverter configuration. Given a nominal peak power of the PV array, this simulation procedure leads to the PV inverter maximum rated power which maximizes the yearly injected energy to the grid.

Inductance characteristics of PMSMs and their impact on saliency-based sensorless control

Abstract: Advantages of operating a Permanent Magnet Synchronous Machine (PMSM) without a position sensor are many and are well known. This paper presents a study of the effects of space harmonics in the incremental inductances and their impact on the machine saliency. The effects of space harmonics exclusively due to the machine (i.e., the saturation saliency distribution) are given particular consideration. The results are illustrated through inductance analysis and measurement of inductance profiles of two similar PMSM machines. The space harmonics in the inductance profiles are correlated with the position estimate distortions through a Matlab/Simulink embedding finite element (FE) machine simulation. Significant differences in sensorless operation of the two machines are found which correlate to the inductance profiles. This illustrates that inductance profiling can inform upon machine design in order to improve sensorless capabilities.

Predictive current control of three-phase two-level four-leg inverter

Abstract: Distributed power systems are getting more attention now-a-days due to their high flexibility and reliability. In this paper, predictive current control strategy is proposed for the grid-connected four-leg inverters. This kind of converter is developed to deliver power to the unbalanced/nonlinear three-phase loads and as well to the grid. The discrete-time model of the converter and load is used to predict the future behavior of the load currents for each valid switching state. The control method chooses a switching state that minimizes the error between the output currents and their references. The feasibility of the proposed method is verified by computer simulations, showing a good performance and capacity to compensate the disturbances.