M.J. Newman

Chalmers University of Technology, Göteborg, Vaestra Goetaland, Sweden

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Publications (13)28.46 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Dynamic voltage restorers (DVRs) are now becoming more established in industry to reduce the impact of voltage sags to sensitive loads. However, DVRs spend most of their time in standby mode, since voltage sags occur very infrequently, and hence their utilization is low. In principle, it would be advantageous if the series-connected inverter of a DVR could also be used to compensate for any steady-state load voltage harmonics, since this would increase the power quality "value-added" benefits to the grid system. However, before this can be done, consideration must be given to the control of steady-state power through the DVR, the increased losses, and the low modulation depths at which the scheme must operate to achieve acceptable harmonic compensation performance. This paper presents a selective harmonic feedback control strategy that can be easily added to medium-voltage DVR systems to provide voltage harmonic compensation capabilities with minimal effect on the sag compensation performance of the basic DVR. The proposed controller has been experimentally verified on a medium-voltage (10 kV) three-phase DVR prototype under a range of conditions, including distorted supply voltages, nonlinear loads, and operation during distorted voltage sags.
    IEEE Transactions on Industry Applications 12/2005; · 1.67 Impact Factor
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    ABSTRACT: Current regulation techniques for pulsewidth-modulated (PWM) voltage source inverters (VSIs) can be classified as either linear or nonlinear. Linear techniques consist principally of either a proportional-integral (PI) or a predictive current control strategy, while nonlinear schemes are usually based on a hysteresis strategy. Of the two linear strategies, predictive current control offers the advantages of precise current tracking with minimal distortion and can also be fully implemented on a digital platform. However, the conventional implementation of the predictive current regulation (PCR) algorithm is sensitive to noise and errors in the load inductance estimate, particularly when the back EMF is also estimated. This paper presents an improved PCR algorithm that retains all the benefits associated with PCR while achieving significantly increased robustness to load parameter mismatch and reduced zero current clamped oscillation effects. It is also relatively insensitive to noise in the sampled current measurements. The algorithm is equally applicable to variable fundamental frequency applications such as variable speed drives and to fixed fundamental frequency applications such as PWM rectifier systems or active filters. Simulation and experimental results are presented to confirm the improved robustness of the new algorithm.
    IEEE Transactions on Industry Applications 12/2005; · 1.67 Impact Factor
  • H. Awad, H. Nelsen, F. Blaabjerg, M.J. Newman
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    ABSTRACT: The static series compensator (SSC) has shown a significant capability to mitigate voltage dips, which are the most severe problem to sensitive loads. Also, it has been declared that the function of the SSC can be extended to work as a series active filter. This work proposes a moving-average filter to detect the fundamental component of the measured voltages and currents (needed to control the SSC) while using a double vector control algorithm to improve the transient performance of the SSC. This is made in order to accurately control the fundamental voltage component at the load terminals in the case of distorted grid voltage. Furthermore, a selective harmonic compensation strategy is applied to filter out the grid harmonics. The operation of the SSC under distorted utility conditions and voltage dips is discussed. The validity of the proposed controller is verified by experiments, carried out on a 10-kV SSC laboratory setup. Experimental results have shown the ability of the SSC to mitigate voltage dips and harmonics. It is also shown that the proposed controller has improved the transient performance of the SSC even under distorted utility conditions.
    IEEE Transactions on Power Systems 03/2005; · 2.92 Impact Factor
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    ABSTRACT: The dynamic voltage restorer (DVR) has become popular as a cost effective solution for the protection of sensitive loads from voltage sags. Implementations of the DVR have been proposed at both a low voltage (LV) level, as well as a medium voltage (MV) level; and give an opportunity to protect high power sensitive loads from voltage sags. This paper reports practical test results obtained on a medium voltage (10 kV) level using a DVR at a distribution test facility in Kyndby, Denmark. The DVR was designed to protect a 400-kVA load from a 0.5-p.u. maximum voltage sag. The reported DVR verifies the use of a combined feed-forward and feed-back technique of the controller and it obtains both good transient and steady-state responses. The effect of the DVR on the system is experimentally investigated under both faulted and nonfaulted system states, for a variety of linear and nonlinear loads. Variable duration voltage sags were created using a controllable LV breaker fed by a 630 kVA distribution transformer placed upstream of the sensitive load. The fault currents in excess of 12 kA were designed and created to obtain the required voltage sags. It is concluded the DVR works well in all operating conditions.
    IEEE Transactions on Power Electronics 06/2004; · 5.73 Impact Factor
  • G.H. Bode, P.C. Loh, M.J. Newman, D.G. Holmes
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    ABSTRACT: Current regulation techniques for pulse width modulated voltage source inverters can be classified as either linear or nonlinear. Linear techniques consist principally of either a proportional-integral or predictive current control strategy, while nonlinear schemes are usually based on a hysteresis strategy. Of the two linear strategies, predictive current control offers the advantages of precise current tracking with minimal distortion and can also be fully implemented on a digital platform. However, the conventional implementation of the predictive current regulation algorithm is sensitive to noise and errors in the load inductance estimate, particularly when the backemf is also estimated. This paper presents an improved predictive current regulation algorithm that retains all the benefits associated with predictive current regulation while achieving significantly increased robustness to load parameter mismatch and reduced zero current clamping oscillation effects. It is also relatively insensitive to noise in the sampled current measurements. The algorithm is equally applicable to variable fundamental frequency applications, such as variable speed drives, and to fixed fundamental frequency applications, such as PWM rectifier systems or active filters. Simulation and experimental results are presented to confirm the improved robustness of the new algorithm.
    Power Electronics and Drive Systems, 2003. PEDS 2003. The Fifth International Conference on; 12/2003
  • [Show abstract] [Hide abstract]
    ABSTRACT: Voltage regulation of long weak distribution lines is a challenging problem, particularly when it may not be economic to simply upgrade the network. D-STATCOMs offer an attractive alternative, with their potential to provide both steady state and transient voltage compensation for a limited capital investment. However, operation of these systems with weak networks needs careful attention to achieve a stable and fast response under all supply conditions. This paper proposes a new cascade loop control strategy to regulate and balance the voltage at a distribution bus using a D-STATCOM which, compared to other reported strategies, is more robust and works well under all system conditions. Simulation and experimental results are presented to verify the stability of this control strategy across a range of operating conditions.
    Power Electronics and Drive Systems, 2003. PEDS 2003. The Fifth International Conference on; 12/2003
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    ABSTRACT: Most of the many reported control algorithms for uninterruptible power supplies (UPSs) use either filter inductor or filter capacitor currents as feedback variables to regulate the output voltage. This paper explores the fundamental performance issues associated with the use of these quantities as feedback variables, with a view to determining their contribution to the transient system response and output harmonic compensation in any particular situation. A proportional plus resonant (P+resonant) compensator is then added into the outer voltage regulation loop to achieve zero steady error, to develop a high performance UPS control algorithm, which is applicable to both single-phase and three-phase systems. Theory, simulation, and experimental results are presented in the paper.
    IEEE Transactions on Power Electronics 10/2003; · 5.73 Impact Factor
  • M.J. Newman, D.G. Holmes
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    ABSTRACT: Most infinite impulse response (IIR) digital filter implementations in power electronic inverter applications are based on the time shift operator q and its associated z-transform. But for higher sampling frequencies where the sample period approaches zero for z-transform discrete systems, their dynamic response does not converge smoothly to the continuous counterpart, causing substantial implementation problems. In contrast, the response of filters based on the delta operator does converge to the continuous counterpart for smaller sample periods, and hence they are much better suited for digital control applications where sampling frequencies are much higher than the system poles. This paper describes the basis of the delta operator, its use for IIR digital filter systems, and shows how the technique can be used in power electronic inverter applications to achieve substantial performance benefits compared to equivalent shift-based implementations. A brief review of shift based IIR filtering is presented and the required conversions to the delta form given. The specific examples of an active filter and a P + Resonant current regulator are used to illustrate the improvements that can be expected. The superior performance of the delta operator for digital control of inverter applications has been verified in both simulation and experiment.
    IEEE Transactions on Power Electronics 02/2003; · 5.73 Impact Factor
  • M.J. Newman, D.G. Holmes
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    ABSTRACT: This paper presents an integrated series/shunt active filter combination (termed a universal custom power conditioner or UCPC) which uses a range of control strategies to achieve improved voltage harmonic compensation capabilities and to fully exploit the potential functionality of the topology without requiring tuned passive harmonic filters. The series active filter uses a DVR type controller for voltage regulation and dip compensation, together with an array of resonant harmonic controllers to provide selective mitigation of supply voltage harmonics as seen by the load. The shunt active filter regulates the DC link voltage and compensates for load unbalance and load current harmonics. Experimental results show that the proposed system can regulate the load voltage, compensating for both source voltage dips and voltage harmonics, while simultaneously eliminating load current harmonics as seen by the source. For radial distribution applications, the proposed scheme achieves minimal load voltage error even under wide variations of supply voltages and load currents. The control principle can be used for both singleand three-phase systems, and is implemented with a delta-operator-based infinite impulse response (IIR) filter to achieve high performance using only 16 bit fixed-point DSP based controllers.
    IECON 02 [Industrial Electronics Society, IEEE 2002 28th Annual Conference of the]; 12/2002
  • M.J. Newman, D.N. Zmood, D.G. Holmes
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    ABSTRACT: Harmonic reference generators for active filter systems are commonly implemented in the synchronous reference frame, so that simple low- or high-pass filter functions can be used depending on the requirements of a particular application. High-pass filters in particular are used when the reference generator is required to produce an "everything but the fundamental" target waveform. This paper presents a stationary frame notch filter equivalent to a high-pass synchronous frame harmonic reference generator for such systems. The use of the stationary frame allows for quicker calculation of the reference generation in a discrete digital implementation, and also allows classical control techniques to be used to analyze the active filter system without requiring synchronous frame transformations of the outside system model. Both simulation (continuous and discrete) and experimental results showing the equivalency of the stationary and synchronous frame reference generation process are presented using both shift and delta-operator-based infinite-impulse response digital filters.
    IEEE Transactions on Industry Applications 12/2002; 38(6):1591- 1599. · 1.67 Impact Factor
  • M.J. Newman, D.G. Holmes
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    ABSTRACT: This paper presents an integrated scheme for protecting and controlling series injection voltage-source inverters used with electrical grid systems. The scheme uses a number of strategies to provide a continuous current path for current from the secondary winding of the injection transformer for both transient and longer term fault conditions. These strategies can also be used to provide a current path during normal operation of the external AC system, facilitating startup and shutdown of the series injection system, as well as recovery from a fault. Both simulation and experimental confirmation of the integrated protection scheme are presented
    IEEE Transactions on Industry Applications 06/2002; · 1.67 Impact Factor
  • M.J. Newman, D.N. Zmood, D.G. Holmes
    [Show abstract] [Hide abstract]
    ABSTRACT: Harmonic reference generators for active power filter systems are commonly implemented in the synchronous reference frame, so that simple low or high pass filter functions can be used depending on the requirements of a particular application. High pass filters in particular are used when the reference generator is required to produce an "everything but the fundamental" target waveform. This paper presents a stationary frame notch filter equivalent to a high pass synchronous frame harmonic reference generator for such systems. The use of the stationary frame allows for quicker calculation of the reference generation in a discrete digital implementation, and also allows classical control techniques to be used to analyze the active filter system without requiring synchronous frame transformations of the outside system model. Both simulation (continuous and discrete) and experimental results showing the equivalency of the stationary and synchronous frame reference generation process are presented using both shift and delta operator based IIR digital filters
    Applied Power Electronics Conference and Exposition, 2002. APEC 2002. Seventeenth Annual IEEE; 02/2002
  • [Show abstract] [Hide abstract]
    ABSTRACT: Most of the many reported control algorithms for uninterruptible power supplies use either filter inductor or filter capacitor currents as feedback variables to regulate the output voltage. This paper explores the fundamental performance issues associated with the use of these quantities as feedback variables, with a view to determining their contribution to the transient system response in any particular situation. Then a proportional plus resonant (P+resonant) compensator is added into the outer voltage regulation loop to achieve zero steady error, to develop a high performance UPS control algorithm which is applicable to both single and three phase systems. Theory, simulation and experimental results are presented in the paper
    Power Electronics Specialists Conference, 2001. PESC. 2001 IEEE 32nd Annual; 02/2001

Publication Stats

588 Citations
28.46 Total Impact Points

Institutions

  • 2005
    • Chalmers University of Technology
      • Division of Electric Power Engineering
      Göteborg, Vaestra Goetaland, Sweden
  • 2001–2005
    • Monash University (Australia)
      • Department of Electrical and Computer Systems Engineering, Clayton
      Melbourne, Victoria, Australia
  • 2003
    • Nanyang Technological University
      Tumasik, Singapore