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ABSTRACT: Two techniques are presented to balance the filter capacitor voltages of a multipulse rectifier with the active injection operating on a variable-frequency supply. The active injector consists of a low-rated bidirectional switch that modifies the behavior of a 12-pulse rectifier at either low or high frequency, resulting in 24-pulse or multilevel pulse width modulation operation, respectively. The operation of the rectifier and the injector, the practical issues that unbalance the capacitor voltages, and the methods to correct this imbalance are explained together with experimental results obtained with a 4-kW prototype.
IEEE Transactions on Industry Applications 03/2011; · 1.66 Impact Factor
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ABSTRACT: A second-harmonic direct current (DC) ripple compensation technique is presented for a multi-phase, fault-tolerant, permanent magnet machine. The analysis has been undertaken in a general manner for any pair of phases in operation with the remaining phases inactive. The compensation technique determines the required alternating currents in the machine to eliminate the second-harmonic DC-link current, while at the same time minimising the total rms current in the windings. An additional benefit of the compensation technique is a reduction in the magnitude of the electromagnetic torque ripple. Practical results are included from a 70 kW, five-phase generator system to validate the analysis and illustrate the performance of the compensation technique.
IET Electric Power Applications 02/2011; · 1.17 Impact Factor
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ABSTRACT: A direct-frequency control for Current Injection Series Resonant Converter (CISRC) is developed to regulate the output voltage. The PI controller is used and the design is based on the open-loop control-to-output frequency responses. Controller design also involves a trade-off between reducing the output voltage ripple and maintaining the high quality input line current. The closed-loop direct frequency control of the CISRC is finally validated with a combination of results from the prediction in MATLAB<sup>reg</sup> and the detailed simulation in Saber<sup>reg</sup>. As a result, for the first time, a complete closed-loop operation of the CISRC is presented.
Power and Energy Conference, 2008. PECon 2008. IEEE 2nd International; 01/2009
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ABSTRACT: This paper describes a new control strategy for an aircraft electrical systems evaluation platform. The 100 kVA, experimental facility includes multiple generators and power electronic loads interconnected by a high-voltage dc bus, centrally controlled by a real-time computer and data logging system. The Facility is to allow electrical power management techniques to be developed for future autonomous aircraft. The control of the facility presents important challenges as it has to be flexible, facilitating future expansion, robust, safe, and yet allow the development of advanced control strategies.
Industrial Electronics, 2008. IECON 2008. 34th Annual Conference of IEEE; 12/2008
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ABSTRACT: The active stabilisation of an HVDC distribution system with multiple constant power loads is presented. Each constant power load comprises a separate motor drive including the torque and speed control functions. By adding a simple admittance compensating controller to the current control loop of the constant power loads, the loads, and therefore the HVDC distribution system, are stabilised. Small-signal analysis techniques are used to form a basis for the design of the active stabilising controllers. Root locus plots are used to examine the system poles as the active and passive damping parameters are adjusted. First, a single motor drive and input filter is examined, then the source output filter is included and finally a second motor drive and input filter is added. The performance of the final design is verified through detailed Saber simulations of the HVDC distribution system.
Vehicle Power and Propulsion Conference, 2008. VPPC '08. IEEE; 10/2008
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ABSTRACT: An input filter state feed-forward stabilising controller is presented to stabilise a constant power load and is validated using a brushless DC motor drive system. The strategy is to feed-forward a stabilising signal which is a function of the DC-link filter variables, capacitor voltage and the inductor current, into the current control loop of the motor drive to modify the magnitude and phase of the system input admittance around the input filter natural frequency and thereby damp the input filter. The controller design and parameter selection are described. The impact of the stabilising controller is examined on the motor controller performance and finally the effectiveness of the controller is verified by simulation and experimentally.
IET Electric Power Applications 10/2008; · 1.17 Impact Factor
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ABSTRACT: The derivation of an optimal ripple injection technique for multi-pulse rectifiers operating on variable frequency aerospace supplies is presented. This is determined by analysing the multi-level PWM operating mode of a 12-pulse rectifier that uses a bidirectional switch to modify its behaviour. The resultant line currents are almost sinusoidal, the THD being 1.06%. The injector current is 2.5% of the load current. The principle of the multi-level PWM injection mode, idealised waveforms and the determination of the ideal ripple injection are explained and experimental results obtained with a 4 kW prototype are presented.
Power Electronics Congress, 2008. CIEP 2008. 11th IEEE International; 09/2008
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ABSTRACT: Based on the d-q model of a permanent-magnet synchronous motor drive, analytical expressions are derived for the small-signal input admittance of the system, which allow the examination of negative input admittance related instabilities. A compensating function is added to the control system to eliminate the instability effects and the analytical models are used to establish a design procedure. Saber simulations are used to validate the analysis and the operation of the stabilising controller.
Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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ABSTRACT: A three-phase, multilevel rectifier using active voltage injection with one MOSFET device is presented. The injector consists of a bidirectional switch that modifies the behavior of a 12-pulse rectifier resulting in either 24-pulse or multilevel pulsewidth-modulated (PWM) operation. The resultant input currents are almost sinusoidal, the line current THD being 2.36% for 24-pulse operation and 1.06% for PWM operation. The MOSFET current is 2.9% of the load current. The circuit operation, idealized waveforms and modulation strategy are explained and experimental results are presented.
IEEE Transactions on Power Electronics 06/2008; · 4.65 Impact Factor
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ABSTRACT: To carry out stability studies on more electric systems in which there is a preponderance of motor drive equipment, input admittance expressions are required for the individual pieces of equipment. In this paper the techniques of averaging and small-signal linearisation will be used to derive a simple input admittance model for a low voltage, trapezoidal back EMF, brushless, DC motor drive system.
Power Electronics, Machines and Drives, 2008. PEMD 2008. 4th IET Conference on; 05/2008
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ABSTRACT: The importance of power quality increases as more electric systems are introduced on aircraft. This paper compares the common mode and harmonic performance of four suitable multi-pulse diode rectifiers to give a better understanding of the performance tradeoffs of each system. This is achieved by simulating and assessing the effects of imbalance in the phase shifting transformers, voltage harmonics and negative sequence imbalance in the supply on CMV, line currents and Total Harmonic Current Distortion (THDI). This paper concludes that zero sequence harmonic distortion has the largest impact on the magnitude of CMV and a negligible effect on THDI. It is found that the DC link voltage is affected negligibly by harmonic distortion, negative sequence supply imbalance and inductive imbalance in the phase shifting transformers. Higher pulse number circuits tend to have a lower harmonic distortion and lower CMV providing the higher pulse number is not achieved by extending a lower pulse number converter using voltage injection techniques.
Power Electronics, Machines and Drives, 2008. PEMD 2008. 4th IET Conference on; 05/2008
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ABSTRACT: A negative input-resistance compensator is designed to stabilize a power electronic brushless dc motor drive with constant power-load characteristics. The strategy is to feed a portion of the changes in the dc-link voltage into the current control loop to modify the system input impedance in the midfrequency range and thereby to damp the input filter. The design process of the compensator and the selection of parameters are described. The impact of the compensator is examined on the motor-controller performance, and finally, the effectiveness of the controller is verified by simulation and experimental testing.
IEEE Transactions on Industrial Electronics 01/2008; · 5.16 Impact Factor
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ABSTRACT: This paper presents a 3-phase, voltage-sourced, 36-pulse converter that draws almost sinusoidal currents. The converter results from the combination of a series connected, 12-pulse, voltage-sourced rectifier with a passive voltage injection circuit and a bi-directional switch. The voltage injection circuit uses a single-phase rectifier bridge and a single-phase transformer. Both the voltage injection circuit and the bi-directional switch operate at six times the supply frequency and have a low rating. In this paper, the converter operation is explained and analysed. Subsequently, the converter is evaluated experimentally using a 4 kW, 400 Hz prototype, where the THD<sub>I</sub> of the line currents was measured to be below 1.2%.
Power Electronics and Drive Systems, 2007. PEDS '07. 7th International Conference on; 12/2007
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ABSTRACT: This paper presents a 3-phase, voltage-sourced, 48-pulse converter. The converter results from the combination of a series connected 12-pulse voltage- sourced rectifier with a passive voltage injection circuit, a passive current injection circuit and a bi-directional switch. The voltage and current injection circuits each use a single-phase rectifier bridge and a single-phase transformer circuit. Both the injection circuits and the bidirectional switch operate at six times the supply frequency and have a low rating. In this paper the converter operation is explained, analysed and simulated.
Power Electronics and Drive Systems, 2007. PEDS '07. 7th International Conference on; 12/2007
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ABSTRACT: A control strategy is described to drive an active injector for multi-pulse rectifiers operating on variable frequency aerospace supplies. The injection technique utilises a single low-rated active device that carries approximately 2.9% of the load current, and this may be driven with either low-frequency pulses or high-frequency, pulse-width modulation to produce 24-pulse operation or multi-level PWM operation respectively. The resultant input currents are almost sinusoidal, the line current THD being 2.36% for the 24-pulse operation and 1.06% for the PWM operation. The control principle, design and performance are presented in this paper. Experimental results of the controller with a 4 kW prototype are shown.
Power Electronics and Drive Systems, 2007. PEDS '07. 7th International Conference on; 12/2007
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ABSTRACT: The design and performance are described of a complete fuel cell-based power train for a small delivery vehicle. For low cost and simplicity, the power train comprises a single unidirectional DC-DC converter to interface the fuel cell, with a supercapacitor power buffer that is connected directly across the DC-link of the traction drive. The paper describes the overall design of the power train, in particular focusing on the development and performance of the control algorithm that is required to manage the energy flow between the fuel cell, super capacitors and traction system, a key objective being to minimize the transient loading of the fuel cell. A computer based model is used to design the controller and the results are validated by comparison with data from a dynamometer-based test rig of the complete power train for typical driving cycles.
Vehicle Power and Propulsion Conference, 2007. VPPC 2007. IEEE; 10/2007
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ABSTRACT: A combination of two, simple, passive injection circuits is used to eliminate virtually all the low-order harmonics from the line currents of a standard 12-pulse rectifier, transforming its performance into that of a 36-pulse system. A line current total harmonic distortion of 1.51% is achieved in a 15-kW, 400-Hz prototype. The basic 12-pulse rectifier comprises two 6-pulse bridges that are series connected on both the ac and dc sides along with a 50%-rated, delta-star, phase-shifting transformer, while each injection circuit principally consists of a small transformer that operates at six times the supply frequency and carries around 1% of the total power throughput. The injection techniques are also valid for a fully isolated transformer arrangement. Full details of the circuit operation and design are reported
IEEE Transactions on Power Electronics 06/2007; · 4.65 Impact Factor
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ABSTRACT: This paper attempts to identify the best multi-level topology (cost and performance) for grid-connected converters supplied from residential renewable sources. This is done through a series of SABER time-domain simulations and the use of data about the devices currently found in the market. The cascaded multi-level topology and the triangular carrier based phase-shifted unipolar PWM switching scheme are used because of their straightforward approach to control. In addition to a PI current feedback loop, a voltage feedforward loop is introduced to further improve the output performance. For low switching frequencies (i.e. negligible switching losses), comparably efficient converters can be cheaper by implementing a multi-cell design. However, if the efficiency of such designs is to exceed that of the single-cell designs, the converter cost can become disadvantageous. If the switching frequency is high (i.e. considerable switching losses), the conversion efficiency of a single-cell converter is always higher than that of a multi-level converter.
Power System Technology, 2006. PowerCon 2006. International Conference on; 11/2006
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ABSTRACT: Practical results are used to parameterise a physically based, compact IGBT model for three generations of IGBT (PT, NPT and IGBT3), at temperatures extending down to 50 K. Full details are presented of the model parameter variations with temperature over the range 50-300 K. The models are then used to examine the performance of a sinusoidal pulse-width-modulated inverter leg at cryogenic temperatures
IEE Proceedings - Circuits Devices and Systems 11/2006; · 0.36 Impact Factor
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ABSTRACT: A step-up converter is described to interface the low, poorly regulated fuel cell output voltage (70-120 V) with the higher voltage supercapacitor bank and traction drive system on a small fuel cell powered electric vehicle. The paper focuses on the design of an interleaved boost converter, in particular comparing a two inductor circuit with an alternative topology comprising a single inductor plus interphase transformer (IPT). Whilst the two circuits have identical inductive stored energies, the lower AC excitation of the inductor in the IPT topology offers performance benefits
Power Electronics and Motion Control Conference, 2006. IPEMC 2006. CES/IEEE 5th International; 09/2006
