Abstract This paper introduces a novel loss model concept for performance evaluation and design optimization of power electronics converters based on MathCAD sheet. A dual active bridge (DAB) converter (12 V/360 V, 1 kW and 25 kHz) is... more
Abstract This paper introduces a novel loss model concept for performance evaluation and design optimization of power electronics converters based on MathCAD sheet. A dual active bridge (DAB) converter (12 V/360 V, 1 kW and 25 kHz) is used as the test platform. The ...
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Most of FACTS devices and grid connected converters need the information about the frequency and phase of the grid for synchronization and control. In some cases, the value to be measured that is used as synchronization signal is at... more
Most of FACTS devices and grid connected converters need the information about the frequency and phase of the grid for synchronization and control. In some cases, the value to be measured that is used as synchronization signal is at remote bus or at a different voltage potential, which would require expensive high voltage measurements or high bandwidth communication. A new synchronization method for single-phase floating convertert is presented, which neither requires high voltage measurements nor high bandwidth communication. The method is applied to a new FACTS device - Distributed Power Flow Controller (DPFC) which is derived from the UPFC. Within the DPFC, multiple single-phase converters are distributed along the transmission line instead of one big 3-phase converter. The principle of this method is to use the line current as the rotation reference frame which enables the series converter to read the phase and frequency information locally. In this case, only the signals in dc quantity are communicated, and the system stability during communication failure is greatly improved.
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The UPFC is the most powerful power flow controller recently, and because of the exchange of active power between the shunt and series parts, they have to be located at the same place. This paper presents a new concept to transmit power... more
The UPFC is the most powerful power flow controller recently, and because of the exchange of active power between the shunt and series parts, they have to be located at the same place. This paper presents a new concept to transmit power without the common DC link of the UPFC, which gives the possibility of the separated UPFC. The exchange
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Abstract This paper studies the capability of the DPFC to damp low frequency power oscillation. The POD controller parameters are calculated by using the residue method. It is shown that the DPFC has the capability of damping multiple... more
Abstract This paper studies the capability of the DPFC to damp low frequency power oscillation. The POD controller parameters are calculated by using the residue method. It is shown that the DPFC has the capability of damping multiple frequency oscillations at the ...
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The increasing number of components in a system makes the integration of complex system a challenging task. Having multiple requirements, limitations and schedules to bring a product to market and to achieve the best possible system... more
The increasing number of components in a system makes the integration of complex system a challenging task. Having multiple requirements, limitations and schedules to bring a product to market and to achieve the best possible system design and configuration from multiple design perspectives, increase the difficulty of its conception even further. Therefore, we propose a new methodology that systematically helps
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... These generators affect the operation and coordination of the distribution network protection. ... The network operator will normally have a protection relay at the medium-voltage side of the transformer with which the DG unit is... more
... These generators affect the operation and coordination of the distribution network protection. ... The network operator will normally have a protection relay at the medium-voltage side of the transformer with which the DG unit is connected to the network. ...
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Page 1. DISTRIBUTED GENERATION UNITS CONTRIBUTING TO VOLTAGE CONTROL IN DISTRIBUTION NETWORKS Sohan Morren, Sjoerd WH de Haan, JA Ferreira Electrical Power Processing, Delft University of Technology ABSTRACT ...
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Page 1. 1 AbstractThe number of distributed generation units connected to the grid is increasing. Their behavior during voltage dips becomes more important. Especially as most units are connected to the grid with power electronic... more
Page 1. 1 AbstractThe number of distributed generation units connected to the grid is increasing. Their behavior during voltage dips becomes more important. Especially as most units are connected to the grid with power electronic converters. ...
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ABSTRACT Distributed Power Flow Controller is a new device within the family of FACTS. The DPFC has the same control capability as the UPFC, but with much lower cost and higher reliability. This paper addresses one of the applications of... more
ABSTRACT Distributed Power Flow Controller is a new device within the family of FACTS. The DPFC has the same control capability as the UPFC, but with much lower cost and higher reliability. This paper addresses one of the applications of the DPFC namely compensation of unbalanced currents in transmission systems. Since the series converters of the DPFC are single-phase, the DPFC can compensate both active and reactive, zero and negative sequence unbalanced currents. To compensate the unbalance, two additional current controllers are supplemented to control the zero and negative sequence current respectively.
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ABSTRACT Switching losses occur in the single active bridge (SAB) with phase-shift control when it operates over a large voltage and load range at constant frequency. At high output current, the SAB operates in continuous conduction mode... more
ABSTRACT Switching losses occur in the single active bridge (SAB) with phase-shift control when it operates over a large voltage and load range at constant frequency. At high output current, the SAB operates in continuous conduction mode (CCM) where the anti-parallel diode of the switch conducts prior to the switch turning on, thus enabling ZVS. However at low output current, zero current switching (ZCS) turn-off occurs in discontinuous conduction mode (DCM) and ZVS turn-on is lost. With the dual current pulse control proposed in this paper where a non-zero turn-off current is maintained during DCM, switching losses can be mostly eliminated across large output current range with a simple auxiliary circuit, hence enabling large voltage and load variations at higher efficiency. Efficiency increase of up to 12 % at light-load can be achieved without sacrificing its full-load efficiency. The predicted results are validated with a 3 kW SAB hardware prototype.
ABSTRACT Symmetry Cockcroft Walton multiplier is a typical cascade voltage multiplier. It is an attractive alternative to the high voltage (HV) transformer with high turn ratio and bridge rectifier in the HV generator in medical X-ray... more
ABSTRACT Symmetry Cockcroft Walton multiplier is a typical cascade voltage multiplier. It is an attractive alternative to the high voltage (HV) transformer with high turn ratio and bridge rectifier in the HV generator in medical X-ray machine. It can reduce the stray capacitance of the HV transformer. However, previous work reports that the parasitic capacitances in the multiplier itself can be added to the stray capacitance of the transformer, which becomes a burden to the resonant capacitance of the generator. Thus, it is crucial to minimize the parasitic capacitances in the multiplier. In this paper, the complete model of the parasitic capacitances in the multiplier is exhibited. The model gives full description of parasitic capacitances in any spatial configuration of the multiplier module. Then, the equivalent capacitance of the model is obtained and analyzed to exhibit the role of parasitic capacitances in the system circuit. The dependence of the equivalent capacitance on different parameters, such as different groups of parasitic capacitances and the number of diodes per chain, is addressed. Besides, the impact of breakdown of the diodes on the equivalent capacitance is also exhibited. The complete capacitance model and the analysis of the equivalent parasitic capacitance are validated by the experimental measurements. In the end, guidelines are concluded for how to minimize the equivalent parasitic.
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ABSTRACT The Partial Resonant Single Active Bridge (PR-SAB) introduced in this paper is able to reduce conduction losses in the Single Active Bridge (SAB) with the addition of partial resonant phases. In the SAB, current flows through the... more
ABSTRACT The Partial Resonant Single Active Bridge (PR-SAB) introduced in this paper is able to reduce conduction losses in the Single Active Bridge (SAB) with the addition of partial resonant phases. In the SAB, current flows through the switch snubber capacitors only during the short quasi-ZVS turnoff phases. However in the PR-SAB, current flows in the snubber capacitors instead of the switches and diodes during the partial resonant phases which occupy up to 50% of each switching period. As capacitors have negligible losses as compared to switches and diodes especially at higher voltages, conduction losses are reduced when significant portion of current is diverted to the capacitors. By reducing conduction losses, higher overall efficiency is achieved in the PR-SAB. The conduction losses reductions of the components in the PR-SAB are analysed and compared with those in the SAB. IGBT switching losses reductions during quasi-ZVS turn-off in the PR-SAB are also discussed. With the analysed conduction and switching losses, the improved efficiencies of the PR-SAB over the SAB are analytically determined. As compared to the SAB, the PR-SAB also exhibits up to 20% lower peak currents resulting in lower component stresses. These analysis are verified with experimental results obtained with a 3.4 kW hardware prototype.
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ABSTRACT This is a follow-up paper to the publication [1]. The previous paper presents the complete model of parasitic capacitances of a high voltage (HV) multiplier, which is employed as a capacitive rectifier in HV generator in medical... more
ABSTRACT This is a follow-up paper to the publication [1]. The previous paper presents the complete model of parasitic capacitances of a high voltage (HV) multiplier, which is employed as a capacitive rectifier in HV generator in medical x-ray machine. The equivalent parasitic capacitance of the multiplier Cem based on the model is exhibited to interpret the role of the parasitic capacitances in circuit operation of the HV generator. Without detailed explanation about derivation of analytical expression of Cem, its dependence on the component parameters are directly shown, which leads to guidelines for minimization of Cem. However, the complete model shows a capacitance network with complicated structure and containing voltage-dependent capacitances and constant voltage sources, which gives complexity to derivation of Cem as well as difficulties to clear understanding of the voltage dependence of Cem. Thus, this paper presents the detailed derivation and analytical expression of Cem. Exactly speaking, the key part of Cem, namely the total chain capacitance CDcht that determines the voltage dependence of Cem, is conducted. A simple way is presented for the derivation of CDcht. The derivation can give readers a clear understanding of the voltage dependence of CDcht. Besides the derivation, a design procedure for minimization of Cem is created based on the proposed guidelines in [1], accompanied by a case study. It gives designers step-by-step rules to make an optimal HV multiplier with a minimum Cem.
ABSTRACT Modular DC-DC converters have been used in high power applications to increase both the maximum power and voltage ratings of DC-DC converters. In parallel-connected modular DC-DC converters, light-load efficiency has been... more
ABSTRACT Modular DC-DC converters have been used in high power applications to increase both the maximum power and voltage ratings of DC-DC converters. In parallel-connected modular DC-DC converters, light-load efficiency has been reported to improve by shutting down unnecessary modules. In this paper, low voltage efficiency of series-connected converter is improved by shutting down modules to shift the input voltage of the remaining modules to higher values for higher efficiency. Moreover, minimum input voltage of the converter is also reduced and input voltage range is therefore increased. The collapse of input voltage is required during this process and energy stored in the input bus capacitors has to be discharged. The focus of this paper is to use available switches in the modules as bypass switches. A method to control these switches for operation within their safe operating area (SOA) during this process is discussed. Finally, a modular DC-DC convert prototype with input series and output parallel (ISOP) connections is built to verify this concept.
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ABSTRACT This paper describes a DC-DC Full-Bridge Hybrid Series Resonant Converter (FB-HSRC) that enables constant switching frequency across a wide load range. Compared to most resonant converters, this converter has the advantage of... more
ABSTRACT This paper describes a DC-DC Full-Bridge Hybrid Series Resonant Converter (FB-HSRC) that enables constant switching frequency across a wide load range. Compared to most resonant converters, this converter has the advantage of constant frequency operation while maintaining ZVS on and off. Power is controlled with pulse width instead of frequency modulation. This enables filters to be optimised at the constant switching frequency instead of at the worst-case frequency hence reducing the sizes of the passive components in the converter. The FB-HSRC is topologically similar to the Partial Series Resonant Converter (PSRC) [6] but with two additional switches connected in parallel to each of its resonant capacitors in its switchless phase arm. At minimum load, the converter behaves like the PSRC with its resonant capacitors and series inductor contributing to power transfer. As load increases, these resonant capacitors also concurrently serve as ZVS turn off commutation capacitors for the switches during the resonant phase. Voltage and current waveforms are simulated with steady-state models of the operation modes. The converter efficiencies at various loads are calculated with the loss model obtained. Finally, a converter prototype is built for an output load range of 13 W to 100 W operating at a frequency of 100 kHz. Experimental results are obtained and are then compared against the simulations results and efficiency calculations.
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ABSTRACT Modular DC-DC converters are commonly used to increase the power capacity of a DC-DC converter for high power applications. To obtain the required power, multiple modules are connected in the input-parallel and output-parallel... more
ABSTRACT Modular DC-DC converters are commonly used to increase the power capacity of a DC-DC converter for high power applications. To obtain the required power, multiple modules are connected in the input-parallel and output-parallel (IPOP) configuration. In addition, phase-shedding are used to increase efficiency of such modular DC-DC converters at light-loads. With Single Active Bridge (SAB) modules, efficiency of the system can be further improved by increasing the snubber capacitance which results in Partial Resonant Single Active Bridge (PR-SAB) modules. As the load range of the PR-SAB load range is reduced, certain loads within the entire load range are therefore not attainable when they are connected in the IPOP configuration. This paper describes how snubber capacitance in each module is optimised such that the entire existing load range is maintained while improving system efficiency. In addition, by utilising unequal module power distribution, the overall IPOP converter efficiency is increased over a wide load range to above 94 %. Peak efficiency is also increased to about 96 %. Finally, experimental results for the IPOP converter are obtained with the optimised snubber capacitances in the SAB modules.
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ABSTRACT
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... generation on power system operation and control," KULeuven, ESAT-ELECTA, Promotor: R.Belmans &D.Van Dommelen, Assessor: Driessen J., ISBN 90 ... Paul Forsyth, Rick Kuffel, "Utility applications of a RTDS®... more
... generation on power system operation and control," KULeuven, ESAT-ELECTA, Promotor: R.Belmans &D.Van Dommelen, Assessor: Driessen J., ISBN 90 ... Paul Forsyth, Rick Kuffel, "Utility applications of a RTDS® Simulator", 8; R. Kuffel, J. Giebrecht, T. Maguire, RP Wierckx, P ...
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... suitable electrode materials. Góngora-Nieto, Sepúlveda, Pedrow, Barbosa-Cánovas and Swanson (2002) also mention the problem and describe a new electrode material with a much higher resistance against corrosion. The aim ...
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This paper presents a new component within the flexible ac-transmission system (FACTS) family, called distributed power-flow controller (DPFC). The DPFC is derived from the unified power-flow controller (UPFC). The DPFC can be considered... more
This paper presents a new component within the flexible ac-transmission system (FACTS) family, called distributed power-flow controller (DPFC). The DPFC is derived from the unified power-flow controller (UPFC). The DPFC can be considered as a UPFC with an eliminated common dc link. The active power exchange between the shunt and series converters, which is through the common dc link in
Research Interests: Power Electronics, Energy Conversion, Power Semiconductor Devices, High Voltage, Power Transmission, and 14 moreSystem Reliability, Power Control, Power system control, Impedance, Voltage, FACTS Devices, Transmission Line, Load Flow, Power flow, Electrical And Electronic Engineering, Voltaje, Prototype, Flexible AC Transmission System, and Unified Power Flow Controller (upfc)
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The short-circuit current contribution of wind turbines has not received much attention so far. This paper considers the short-circuit behavior, especially the short-circuit current of wind turbines with a doubly fed induction generator.... more
The short-circuit current contribution of wind turbines has not received much attention so far. This paper considers the short-circuit behavior, especially the short-circuit current of wind turbines with a doubly fed induction generator. Mostly, these wind turbines have a crowbar to protect the power electronic converter that is connected to the rotor windings of the induction generator. First, the maximum