EPE Association: EPE 1989 - 21 - Lecture Session 3.4: POWER ELECTRONICS IN GENERATION AND DISTRIBUTION

EPE 1989 - 21 - Lecture Session 3.4: POWER ELECTRONICS IN GENERATION AND DISTRIBUTION
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1989 - Conference > EPE 1989 - 21 - Lecture Session 3.4: POWER ELECTRONICS IN GENERATION AND DISTRIBUTION

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   APPLICATION-OPTIMIZED CONTROL STRATEGY FOR REACTIVE POWER COMPENSATION OF CONVERTER FED ROLLING MILL DRIVES
By Jürgen Zäh [View]
[Download]

Abstract: Due to the strict requirements of the power supply companies regarding the permissible harmonic and voltage disturbances, the use of converter-fed drives in rolling mills demands the installation of static compensators to an increasing extent. A control concept is presented, which in combination with the components used, satisfies stringent demands on high dynamical compensation of reactive load as well as guaranteeing high accuracy of phase balancing. All control functions such as evaluation of measured values, computation of power (active and reactive components), filter- and control algorithms are implemented on a powerful Programmable High Speed Control System (PHSC). The theoretically derived aspects concerning the required control performance are verified by experimental result gained from a laboratory setup as well as from the operation of the compensator in a rolling steel milI.

   A NOVEL TECHNIQUE FOR REACTIVE POWER COMPENSATION
By P. Mehta; M. Darwish; T. Thomson [View]
[Download]

Abstract: A novel technique for building reactive power compensators using the switched capacitor technique (Darwish, 1987) is presented. Normally, when switched-capacitors are used for reactive power compensation they are operated at the supply frequency. However, in the proposed technique the capacitors are switched at higher frequencies (typically 800Hz). The main advantages of this approach is that it provides a stepless variation in reactive power without the generation of harmonics as is the case with the conventional approach. This paper includes the details of theoretical and experimental investigation carried out at Brunel to assess the new technique.

   A PULSEMODULATED LOW-VOLUME REACTIVE-POWER COMPENSATOR
By Sjoerd W. H. de Haan; Gerjan J. J. de Leijer [View]
[Download]

Abstract: A 3-phase pulsewidth-modulated reactive-power compensator is presented. It is a topology that resembles a Current Source Inverter (CSI) that is shorted on the DC-side. The converter is operated at a high switching frequency which renders the potential to generate nearly undistorted current waveforms. In comparison with traditional compensators the energy storage elements can be relatively small, depending on the switching frequency. By application of an appropriate switching scheme, the reactive power is almost instantaneously transferred from one port to another port of the 3-phase system without substantial energy storage. Test results are shown of a compensator-model which is equipped with IGBT's and which switches at 20kHz.

   ADAPTIVE, CLOSED-LOOP CONTROL OF DYNAMIC POWER FILTERS AS FICTITIOUS POWER COMPENSATORS
By J. H. R. Enslin; M. Naudé; J. D. Van Wyk [View]
[Download]

Abstract: A new control philosophy, utilizing both Thyristor Controlled Reactive sources (TCR), and Dynamic Power Filters (DPF), has been proposed by Enslin (1988a), in the application of fictitious power compensation. This paper shows the closed-loop control of a dynamic power filter (DPF), using an adaptive signal processing algorithm based on the cross-correlation between the voltage and current waveforms. The control strategy is based on the derivation of equivalent network parameters, calculated from digital time domain, cross-correlation signal processing techniques, implemented with the aid of a microcomputer. Practical results under quasi-dynamic operating conditions, obtained from a 15 kVA three phase dynamic power filter, are included in this paper.

   EFFECT OF LOW DISTORTION LIMITS ON FILTER CIRCUIT DESIGN
By K. H. Krüger; W. Schultz [View]
[Download]

Abstract: More and more specifications are setting permissible limits for voltage distortion due to harmonics in order to safeguard the smooth operation of harmonic-sensitive loads in a network. This trend is heading, in some cases, towards the establishment of distortion limits of as low as 1% or less. The object of this paper is to explain the relationship between voltage distortion and such parameters as the switching state of the network, the compensation capacity available for filter circuits and the operating mode of the static converters. lt also demonstrates current tendencies in the design and configuration of filter circuits. Harmonic filter solutions are presented which are based on existing plant and operate in different types of networks and at different voltages.

   A NOVEL PWM SCHEME OF VOLTAGE SOURCE INVERTERS BASED ON SPACE VECTOR THEORY
By Sotoshi Ogasawara; Hirofumi Akagi; Akira Nabae [View]
[Download]

Abstract: A novel PWM scheme which can considerably reduce harmonic currents is proposed. It is explained analytically that the harmonic currents depend on the location of the reference voltage vector, the inverter output voltage vectors used at a switching period, and the sequence of these output voltage vectors. In the novel PWM scheme, the switching sequence is selected so that the harmonic current is minimum. An experimental system which generates the PWM patterns by software at real time is constructed. Compared with the conventional sinusoidal PWM scheme, it is confirmed that the current ripple is decreased and the spectrum is shifted and dispersed to higher frequency region.

EPE 1989 - 21 - Lecture Session 3.4: POWER ELECTRONICS IN GENERATION AND DISTRIBUTION
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1989 - Conference > EPE 1989 - 21 - Lecture Session 3.4: POWER ELECTRONICS IN GENERATION AND DISTRIBUTION
	[return to parent folder]

	APPLICATION-OPTIMIZED CONTROL STRATEGY FOR REACTIVE POWER COMPENSATION OF CONVERTER FED ROLLING MILL DRIVES By Jürgen Zäh	[View] [Download]
Abstract: Due to the strict requirements of the power supply companies regarding the permissible harmonic and voltage disturbances, the use of converter-fed drives in rolling mills demands the installation of static compensators to an increasing extent. A control concept is presented, which in combination with the components used, satisfies stringent demands on high dynamical compensation of reactive load as well as guaranteeing high accuracy of phase balancing. All control functions such as evaluation of measured values, computation of power (active and reactive components), filter- and control algorithms are implemented on a powerful Programmable High Speed Control System (PHSC). The theoretically derived aspects concerning the required control performance are verified by experimental result gained from a laboratory setup as well as from the operation of the compensator in a rolling steel milI.

	A NOVEL TECHNIQUE FOR REACTIVE POWER COMPENSATION By P. Mehta; M. Darwish; T. Thomson	[View] [Download]
Abstract: A novel technique for building reactive power compensators using the switched capacitor technique (Darwish, 1987) is presented. Normally, when switched-capacitors are used for reactive power compensation they are operated at the supply frequency. However, in the proposed technique the capacitors are switched at higher frequencies (typically 800Hz). The main advantages of this approach is that it provides a stepless variation in reactive power without the generation of harmonics as is the case with the conventional approach. This paper includes the details of theoretical and experimental investigation carried out at Brunel to assess the new technique.

	A PULSEMODULATED LOW-VOLUME REACTIVE-POWER COMPENSATOR By Sjoerd W. H. de Haan; Gerjan J. J. de Leijer	[View] [Download]
Abstract: A 3-phase pulsewidth-modulated reactive-power compensator is presented. It is a topology that resembles a Current Source Inverter (CSI) that is shorted on the DC-side. The converter is operated at a high switching frequency which renders the potential to generate nearly undistorted current waveforms. In comparison with traditional compensators the energy storage elements can be relatively small, depending on the switching frequency. By application of an appropriate switching scheme, the reactive power is almost instantaneously transferred from one port to another port of the 3-phase system without substantial energy storage. Test results are shown of a compensator-model which is equipped with IGBT's and which switches at 20kHz.

	ADAPTIVE, CLOSED-LOOP CONTROL OF DYNAMIC POWER FILTERS AS FICTITIOUS POWER COMPENSATORS By J. H. R. Enslin; M. Naudé; J. D. Van Wyk	[View] [Download]
Abstract: A new control philosophy, utilizing both Thyristor Controlled Reactive sources (TCR), and Dynamic Power Filters (DPF), has been proposed by Enslin (1988a), in the application of fictitious power compensation. This paper shows the closed-loop control of a dynamic power filter (DPF), using an adaptive signal processing algorithm based on the cross-correlation between the voltage and current waveforms. The control strategy is based on the derivation of equivalent network parameters, calculated from digital time domain, cross-correlation signal processing techniques, implemented with the aid of a microcomputer. Practical results under quasi-dynamic operating conditions, obtained from a 15 kVA three phase dynamic power filter, are included in this paper.

	EFFECT OF LOW DISTORTION LIMITS ON FILTER CIRCUIT DESIGN By K. H. Krüger; W. Schultz	[View] [Download]
Abstract: More and more specifications are setting permissible limits for voltage distortion due to harmonics in order to safeguard the smooth operation of harmonic-sensitive loads in a network. This trend is heading, in some cases, towards the establishment of distortion limits of as low as 1% or less. The object of this paper is to explain the relationship between voltage distortion and such parameters as the switching state of the network, the compensation capacity available for filter circuits and the operating mode of the static converters. lt also demonstrates current tendencies in the design and configuration of filter circuits. Harmonic filter solutions are presented which are based on existing plant and operate in different types of networks and at different voltages.

	A NOVEL PWM SCHEME OF VOLTAGE SOURCE INVERTERS BASED ON SPACE VECTOR THEORY By Sotoshi Ogasawara; Hirofumi Akagi; Akira Nabae	[View] [Download]
Abstract: A novel PWM scheme which can considerably reduce harmonic currents is proposed. It is explained analytically that the harmonic currents depend on the location of the reference voltage vector, the inverter output voltage vectors used at a switching period, and the sequence of these output voltage vectors. In the novel PWM scheme, the switching sequence is selected so that the harmonic current is minimum. An experimental system which generates the PWM patterns by software at real time is constructed. Compared with the conventional sinusoidal PWM scheme, it is confirmed that the current ripple is decreased and the spectrum is shifted and dispersed to higher frequency region.