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EPE Journal Volume 20-3 - Papers
- A Two-Frequency Quasi Six-Phase Voltage Source Inverter Based on Space Vector PWM
- Fast Simulated Frequency Response Measurement for Switched-Mode Power Circuits
- Test Signal based Speed Estimation for Induction Motor Drives
- Experimental Comparaison of Lamination Material (M330-50 & NO20) Case Switching Flux Synchronous Machine with Hybrid Excitation
- Charge-Equalization Circuit for Series-Connected Batteries with Quasi-resonant Flyback Converters
- Issues on Solar-Generator Interfacing with Voltage-Fed MPP-Tracking Converters
- Low Voltage Ride Through For DFIG Wind Turbines Using Passive Impedance Networks
EPE Journal Volume 20-3 - Editorial
By B. Sneyers
The editorial of EPE Journal 20-3, "Welcome to the first EPE Joint Wind Energy and T&D Chapters Seminar, NTNU, Trondheim, Norway, 9, 10 and 11 May 2011", written by Brigitte Sneyers.
EPE Journal Volume 20-3 - Papers
By N. R. Abjadi; J. Soltani; G. R. Arab Markadeh
With development of series multi-phase motor drives and harmonic injection technique to enhance torque for multi-phase motor drives, there is an immense need for multifrequency PWM voltage source inverters (VSI). The PWM techniques used in the previous works are either of ramp-comparison or of hysteresis type. The first suffer from implementation difficulties and the second has the high variable switching frequency drawback (difficulties of LC input EMI filter design). SVM possesses many advantages over the mentioned PWM techniques and it can be used in multiphase drive applications. One of the most popular multi-phase machines is quasi six-phase (QS) machine. The phasor diagram of a QS system and a two level six-phase VSI are depicted in Fig. 1. Despite the three-phase case the numbers of switching vectors are very high (refer to Fig. 2) and the removal of low-order harmonics in SVM six-phase systems is so complicated. In this paper, a two frequency QS SVM VSI is designed and implemented. The approach improves the performance of the system in terms of total harmonic distortion (THD) and DC-bus utilization. The resulted SVM VSI is used to generate two reference vectors for two series QS machines. Some analysis and discussions are given through the development of the SVM technique, computer simulation and practical results.
By Matti Vilkko; Tomi Roinila; Teuvo Suntio
Modelling and simulation of electric circuits of switched-mode power converters provide the means for computer-based testing before an engineering prototype is manufactured. The topologies of the electric power conversion systems are typically highly complex and the analytical models may become difficult to derive. For such cases, non-parametric frequencyresponse modelling provides an efficient analyzing tool. The prevailing techniques provide methods to simulate time-domain behaviour of non-linear models of circuits and means to generate frequency responses of linearized smallsignal models. Some tools provide also methods to calculate frequency responses of non-linear models. However, they are all based on sine-sweep method which requires a long simulation time. The measurement time can be drastically reduced by applying a broadband excitation signal. This paper presents a frequency-response measurement scheme for switched-mode converters where the sine sweep is replaced by the maximum length binary sequence (MLBS) excitation. The technique allows the design engineer to benefit from accurate frequency responses based on nonlinear modelling while shorter simulation time gives the opportunity to iteratively simulate the effect of parameter variations.
By Heiko Zatocil; Bernhard Piepenbreier
In the first part of the paper an estimation method for sensorless control employing a test signal based reference model is presented. The method estimates the slip frequency by a comparison of the measured test signal impedance curves while the machine is in operation with curves from a test signal based reference model. The reference model which describes the test signal behaviour of the machine is measured during DC magnetisation of a cold machine at steady state and constant rotor flux linkage. During normal machine operation the machine temperature and the stator frequency differ from these conditions and, thus, have a negative influence on quality of the estimation. In the second part of the paper the impact of these disturbances is investigated and two compensation strategies are presented. Measurements on two different standard induction machines which are not especially designed for sensorless control show that the estimation method allows safe operation at standstill and even at zero frequency.
By Emmanuel Hoang; Sami Hlioui; Michel Lecrivain; Mohamed Gabsi
The aim of this paper is to compare the experimental performances of a new hybrid flux switching synchronous machine built with two types of lamination materials (3% silicon iron steel M330-50 and NO-20). This machine uses the flux switching principle where all the active parts are located on the stator (armature windings and permanent magnets). However DC excitation coils where added in the stator and gives a supplementary degree of freedom used to control the total excitation flux. The rotor is only a salient passive rotor and can be robust and made with a low cost technology. This new machine can be fed by means of a traditional three-phase voltage converter or can be associated with a diode rectifier.
By Yao-Ching Hsieh; Wei-Guang Chen; Chen-Yao Liu
A charge equalization circuit for balance discharging in a series-connected battery bank is proposed in this paper. The circuit comprises several parallel-connected flyback converters which connect each unit battery in the bank to supply the electric load. The transformer leakage inductance and capacitances of MOSFETs are applied to fulfill the quasiresonant zero voltage switching (ZVS), which consequently eliminates the voltage spikes and enhance the conversion efficiency. Design equations are derived and numerical analysis results are applied to evaluate the required values of the inductance and capacitance to realize ZVS performance. A battery bank with four series-connected lead-acid batteries is used to verify the proposed charge equalization circuit. The experimental results advocate the applicability of the proposal.
By Teuvo Suntio; Juha Huusari; Jari Leppäaho
The large-scale harvesting of solar energy is an important action to decelerate the observed climate changes and ensuring the availability of energy also in the future. Reliably operating solar-energy systems composing of solar arrays and their interfacing converters are of prime importance to maximize solar-energy harvesting. The main obstacle for the improvements in the reliability is turned out to be the lack of full understanding of the solar-generator interfacing. The paper investigates the interfacing in terms of voltage-fed maximum-power-point (MPP) tracking converters. The investigations confirm that there are two reasons for the observed problems of which the one is the violation of Kirchhoff ’s current law governing the operation of a solar generator and the other is the phenomenon known as negative resistance oscillation (NRO) causing instability. In practice, this means that the voltage-fed converter can reliably operate only at the voltages higher than the maximum-power-point (MPP) voltage. Practical evidence is provided based on a coupledinductor superbuck converter supplied by a real solar panel and loaded with a storage battery.
By Xiangwu Yan; Giri Venkataramanan; P. S. Flannery; Yang Wang; Qing Dong
This paper presents an approach to utilize a passive impedance network in series at the stator side of a typical DFIG wind turbine for the purpose of voltage sag ride through. A control strategy that enables the passive impedance network to engage and stabilize the stator flux during grid voltage sag events has been studied. Simulation results demonstrates that electromagnetic torque and rotor current meet the requirements of new regulator codes, even at 0% of the nominal voltage remaining with uninterrupted current feeding into the grid. Due to its topology and control strategy, the proposed system is easy to control, capable of off-line operation for high efficiency and low cost in manufacturing and maintenance.