EPE Association: EPE 2001 - Topic 03a: Uninterruptible Power Supplies (UPS)

EPE 2001 - Topic 03a: Uninterruptible Power Supplies (UPS)
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2001 - Conference > EPE 2001 - Topic 03: POWER SUPPLIES > EPE 2001 - Topic 03a: Uninterruptible Power Supplies (UPS)

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   Control strategy for reducing inrush current in three-phase UPS system
By S. Nishikata; S. Kuroda; T. Kataoka [View]
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Abstract: Control strategy for reducing inrush current when a load of capacitor-filtered rectifier is connected to a three-phase UPS system is proposed. Inrush current can be greatly reduced when digital control with inrush current suppression loop in addition to observer, voltage drop compensator and PID controller is applied to the system. Transient responses of UPS output voltage and load current when the load is connected are shown, and the usefulness of the proposed control is verified with simulations and experiments.

   Design and Analysis of Output Filter for UPS Inverter
By J. Kim; J. Choi; F. Blaabjerg [View]
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Abstract: This paper proposes a design method of the L-C output filter for UPS inverter. There are two kinds of harmonic sources that make the UPS output voltage waveform be distorted: One is caused by the PWM switching of inverter but most of it can be eliminated by inserting the L-C filter in the output side of inverter. The other is caused by the nonlinear characteristics of the load current. If the output impedance of the UPS inverter is almost zero, then the output voltage waveform may be independent on the nonlinear load current characteristics. But the configuration of the power circuit with L-C filter cannot meet the zero-output impedance at all. The feedback controller complements the harmonic distortion due to the nonlinear load current. But the design value of L-C filter and the system performance of the controller are coupled each other and it is difficult to design the L-C filter considering the system performance of the controller in the conventional method. In this paper, the harmonic components caused by two different sources are analyzed separately based on the transfer function described as the closed form. The filter value can be calculated with the given value of system time constant determined by the switching frequency, the speed of control processor, and the controller gain. A design procedure is described by a single flow chart and explained step by step. The validity of the proposed filter design algorithm is verified through the simulation and experiments.

   Development of a Novel Power Apparatus to Make up for Voltage Dips
By M. Ohshima; F. Nakamura; S. Tamai; Y. Yamamoto; H. Mori [View]
[Download]

Abstract: Along with wide and deep penetration of electronics application into our modern society voltage dips and momentary interruptions mainly due to lightning and snow damage on overhead transmission lines has become to disturb normal operation of loads. UPS, which is mostly employed to protect sensitive loads from them, has such limitations that it dissipates not less energy in running operation because currents flow through two converters in series, that it is poor to feed electric motors which occupy main loads in industrial plants and that it costs high to be applied in common. UPS can be regarded not as omnipotent against voltage dips and short interruptions. We have developed a novel power apparatus termed QBS (Quick Backup System) to supplement above drawbacks in UPS, employing one reversible ac/dc converter and one high-speed switch. Normally QBS supplies power directly from a commercial network to critical loads while the reversible converter interconnects with it to charge the battery. When the critical bus voltage deviates from the tolerance range QBS disconnects the high-speed switch and continues to feed the critical loads in UPS mode. The whole power transition is completed within 2ms. QBS has already been put to practical use in telecommunication center and electronics manufacturer of Japan. This paper presents constitutional technologies developed to realize QBS and obtained experimental data in the field demonstration test of a 100kVA QBS.

   Robust Deadbeat Control for UPS using State and Disturbance Observers
By P. Mattavelli [View]
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Abstract: This paper investigates the use of deadbeat control on both output voltage and inductor current for the inverter stage of Uninterruptible Power Supplies (UPS). Besides the linear state feedback which allocates system poles in the origin so as to achieve deadbeat response for all state variables, this paper proposes the use of a state observer and a disturbance observer for the compensation of the computational delay and for the estimation of the load current, respectively. In the proposed solution, undesired oscillations on the inductor current, which usually occur when the deadbeat control is performed only on the output voltage, are avoided. Moreover, with a proper design of observer parameters, it is possible to minimise the control sensitivity to model uncertainties, parameter mismatches and noise on sensed variables, which usually characterize existing deadbeat control techniques. Finally, an additional control provision is proposed for the implementation of the current limitation of the power converter. Simulation and experimental results on a single-phase UPS laboratory prototype (1 kVA) confirm the effectiveness of the proposed solution.

EPE 2001 - Topic 03a: Uninterruptible Power Supplies (UPS)
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2001 - Conference > EPE 2001 - Topic 03: POWER SUPPLIES > EPE 2001 - Topic 03a: Uninterruptible Power Supplies (UPS)
	[return to parent folder]

	Control strategy for reducing inrush current in three-phase UPS system By S. Nishikata; S. Kuroda; T. Kataoka	[View] [Download]
Abstract: Control strategy for reducing inrush current when a load of capacitor-filtered rectifier is connected to a three-phase UPS system is proposed. Inrush current can be greatly reduced when digital control with inrush current suppression loop in addition to observer, voltage drop compensator and PID controller is applied to the system. Transient responses of UPS output voltage and load current when the load is connected are shown, and the usefulness of the proposed control is verified with simulations and experiments.

	Design and Analysis of Output Filter for UPS Inverter By J. Kim; J. Choi; F. Blaabjerg	[View] [Download]
Abstract: This paper proposes a design method of the L-C output filter for UPS inverter. There are two kinds of harmonic sources that make the UPS output voltage waveform be distorted: One is caused by the PWM switching of inverter but most of it can be eliminated by inserting the L-C filter in the output side of inverter. The other is caused by the nonlinear characteristics of the load current. If the output impedance of the UPS inverter is almost zero, then the output voltage waveform may be independent on the nonlinear load current characteristics. But the configuration of the power circuit with L-C filter cannot meet the zero-output impedance at all. The feedback controller complements the harmonic distortion due to the nonlinear load current. But the design value of L-C filter and the system performance of the controller are coupled each other and it is difficult to design the L-C filter considering the system performance of the controller in the conventional method. In this paper, the harmonic components caused by two different sources are analyzed separately based on the transfer function described as the closed form. The filter value can be calculated with the given value of system time constant determined by the switching frequency, the speed of control processor, and the controller gain. A design procedure is described by a single flow chart and explained step by step. The validity of the proposed filter design algorithm is verified through the simulation and experiments.

	Development of a Novel Power Apparatus to Make up for Voltage Dips By M. Ohshima; F. Nakamura; S. Tamai; Y. Yamamoto; H. Mori	[View] [Download]
Abstract: Along with wide and deep penetration of electronics application into our modern society voltage dips and momentary interruptions mainly due to lightning and snow damage on overhead transmission lines has become to disturb normal operation of loads. UPS, which is mostly employed to protect sensitive loads from them, has such limitations that it dissipates not less energy in running operation because currents flow through two converters in series, that it is poor to feed electric motors which occupy main loads in industrial plants and that it costs high to be applied in common. UPS can be regarded not as omnipotent against voltage dips and short interruptions. We have developed a novel power apparatus termed QBS (Quick Backup System) to supplement above drawbacks in UPS, employing one reversible ac/dc converter and one high-speed switch. Normally QBS supplies power directly from a commercial network to critical loads while the reversible converter interconnects with it to charge the battery. When the critical bus voltage deviates from the tolerance range QBS disconnects the high-speed switch and continues to feed the critical loads in UPS mode. The whole power transition is completed within 2ms. QBS has already been put to practical use in telecommunication center and electronics manufacturer of Japan. This paper presents constitutional technologies developed to realize QBS and obtained experimental data in the field demonstration test of a 100kVA QBS.

	Robust Deadbeat Control for UPS using State and Disturbance Observers By P. Mattavelli	[View] [Download]
Abstract: This paper investigates the use of deadbeat control on both output voltage and inductor current for the inverter stage of Uninterruptible Power Supplies (UPS). Besides the linear state feedback which allocates system poles in the origin so as to achieve deadbeat response for all state variables, this paper proposes the use of a state observer and a disturbance observer for the compensation of the computational delay and for the estimation of the load current, respectively. In the proposed solution, undesired oscillations on the inductor current, which usually occur when the deadbeat control is performed only on the output voltage, are avoided. Moreover, with a proper design of observer parameters, it is possible to minimise the control sensitivity to model uncertainties, parameter mismatches and noise on sensed variables, which usually characterize existing deadbeat control techniques. Finally, an additional control provision is proposed for the implementation of the current limitation of the power converter. Simulation and experimental results on a single-phase UPS laboratory prototype (1 kVA) confirm the effectiveness of the proposed solution.