EPE Association: EPE 1991 - 17 - Session 2.6: HIGH POWER DRIVES

EPE 1991 - 17 - Session 2.6: HIGH POWER DRIVES
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - Conference > EPE 1991 - 17 - Session 2.6: HIGH POWER DRIVES

   [return to parent folder]

   VARIABLE SPEED PUMPED STORAGE SYSTEM FED BY LARGE-SCALE CYCLOCONVERTER
By T. Taguchi; K. Aida; K. Mukai; T. Yanagisawa; T. Kanai [View]
[Download]

Abstract: The world's first variable speed pumped storage system fed by large-scale cycloconverter was brought into operation at the Yagisawa power station Unit 2 of the Tokyo Electric Power Co., Inc. in December, 1990. This remarkable system incorporates the latest large scale, large capacity power electronics technology, ultrahigh-speed digital control technology, and large scale, large capacity generator-motor technology. Actual machine tests carried out at the Yagisawa power station verified various functions of the variable speed pumped storage system, thus allowing the advantages.

   PHASE ANGLE CONTROL OF VOLTAGE SOURCE CONVERTER IN HIGH POWER APPLICATIONS
By Lennart Ängquist; Lars Lindberg [View]
[Download]

Abstract: Voltage Source Converters for high-power applications like HVDC and SVC will encourage the use of low commutation frequency which restricts the attainable control performance. In spite of the low switching frequency the control system must be fast-acting In order to handle start-up and different fault conditions. A control strategy is required that brings the converter into stationary state as fast as possible. The paper describes a control method for a voltage source converter. The proposed control method is based on measured converter flux (time integral of converter voltage) and dc voltage, here exemplified in a six pulse unit. The time to next commutation is calculated in real-time so that the converter flux is guided in minimum time from an arbitrary point in the flux plane towards the stationary orbit.

   NEW SYNCHRONIZATION METHOD FOR THYRISTOR POWER CONVERTERS CONNECTED TO WEAK AC-SYSTEMS
By R. Wiedenbrug; F. P. Dawson; R. Bonert [View]
[Download]

Abstract: This paper presents a new approach to synchronization for a phase controlled thyristor power converter. Detection of accurate zero crossings are possible even under the following conditions: large frequency change, sudden load changes and large commutation overlap angles. The synchronization is achieved by first reconstructing the reference voltage on the ac source side of the converter transformer. A microcontroller based algorithm is used for this purpose. The reconstructed voltage is subsequently used for synchronization purposes. The improvement provided by the new synchronization scheme is verified experimentally.

   INVESTIGATION OF A DOUBLY-FED INDUCTION GENERATOR USING A SIMPLE CYCLOCONVERTER
By H. Härer; U. Horn [View]
[Download]

Abstract: A simple cycloconverter using 6 thyristors for supplying the slipring rotor of an induction generator with variable frequency is described. Due to the supply frequency of the rotor circuit and to the firing sequence of the thyristors, undesirable harmonics may appear in the stator voltage causing light flickers in isolated mains installations such as on board ship or in wind energy generation. These harmonics can be reduced substantially by using suitable firing circuits for the thyristors and by implementing a closed-loop control concept for the rotor circuit. Experimental results as well as simulation results are given.

   AN EXPERIENCE WITH CYCLOCONVERTER - FED IM DRIVES FOR A MODERN TANDEM COLD MILL
By M. Hattori; T. Ishikawa; M. Taniguchi; T. Ohnishi; Y. Kurata [View]
[Download]

Abstract: This paper describes the relationship between motor drive performance and strip thickness gauge accuracy in a modern 5 - stand 6 - high tandem cold mill. The tandem cold mill system was recently put into operation at Yawata Works of the Nippon Steel Corp. Each mill stand is driven by a 72 - arm circulating current cycloconverter - fed IM and auxiliaries each are driven by transistor PWM - VSI - fed IMs. The strip thickness gauge accuracy is directly related to the ratio between the speed response and the speed accuracy of the main drive system. In this paper, this relationship is investigated and verified through simulation and experiment. This paper also proposes a new control method for tandem cold mill motor drives to increase the drive system reliability.

   EXPERT SYSTEM FOR DESIGNING CONVERTERS FOR LARGE SYNCHRONOUS MACHINES
By S. Ahrens; I. Kortaberria; J. Bigeon; D. Poupart [View]
[Download]

Abstract: This paper presents an expert system tool for fast prototyping and cost estimation of converters for large variable speed drives. It outlines the aims of such a tool for a manufacturer's engineering and sales department. After a brief analysis of the design process we describe the system's approach which is based on artificial intelligence methodology. An example illustrates the flexible way in which the system handles technica! design constraints to optimize the converter's cost price. Finally the knowledge representation scheme and the system's implementation are pointed out.

   A NEW APPROACH TO OPTIMIZED NUMERICAL CONTROL OF LARGE POWER CONVERTERS
By S. Diop; J. L. Poulioquen; J. M. Taillardat [View]
[Download]

Abstract: This paper presents a new approach to the numerical control of large power converters, based on a model of the system and open-loop computation of the variables to be controlled. Open-loop computation provides good dynamic performance since the control system does not introduce an additional time constant. Maximum use of the capabilities of digital systems enables the following features to be realized:
- control suited to all types of power converter,
- power rating optimization,
- ease of design and cornmissioning,
- ease of use.
The new approach is applied to the control of active and reactive power flow with a 50 MW Synchrothyr (1) with efficiency optimization at all operating points.

   MODELLING AND IDENTIFICATION OF A SET OF MULTl-MOTOR DRIVES
By F. Parant; C. Coeffier; C. Iung [View]
[Download]

Abstract: The dynamic behaviour of a moving strip in an n-roller system is investigated. The strip passes through several different consecutive sections and is supported, transported and controlled in tension by a multitude of driven rollers. The rollers are driven by induction motor supplied by PWM systems. All of them are coupled mechanically to each other by the material. Starting from an approach of the main system with a partition into m subsystems, an off-line identification of multivariable system parameters is realized. The results obtained by this approach are compared to the experimental results. The method used is efficient to obtain accurate models of a large set of electrical machines coupled by a strip, and can be used in various industrial areas.

   HIGH POWER CYCLOCONVERTER DRIVE FOR DOUBLE-FED INDUCTION MOTORS
By G. M. Brown; B. Szabados; R. Belmans [View]
[Download]

Abstract: Two cycloconverters independently supply stator and rotor windings of a wound rotor induction machine. The control strategy to stabilize this inherently unstable system is derived from the double-fed machine matrix and the resulting algorithm is implemented in hardware with a simple field calculator. A practical implementation of a 2 kW drive, illustrates the feasibility of the drive, and practical performances of full speed in both directions, as well as speed ramps up to 700 rpm/s are realized. The system benefits from the simplicity of line-commutated operation associated with a relatively high frequency of operation of each individual cycloconverter, thereby avoiding saturation effects appearing at low frequencies, combined with control of harmonic generation using the extra degree of freedom provided by the DFM.

   TIME SUBOPTIMAL ROTATION SPEED CONTROL OF A THYRISTOR-SUPPLIED DC MOTOR DRIVE
By Zeljko Ban; Petar Crnosija [View]
[Download]

Abstract: Various methods of time optimal rotation speed control of a thyristor-supplied direct-current motor drive have been analyzed. The design of a rotation speed control algorithm for a DC motor drive without inner armature current feedback providing suboptimal rotation speed step response has been discussed. An armature current limiting algorithm has also been developed. The control algorithms have been developed separately for the continuous and the discontinuous mode of operation of the thyristor converter. Simulation results have indicated that the algorithms described provide suboptimal rotation speed responses.

   EXPERIMENTAL APPLICATION OF LARGE VARIABLE SPEED DRIVES IN A TYPICAL AUXILIARY POWER SYSTEM
By F. Di Maso; C. Raffaelli; M. Rebolini; G. Bergonovo [View]
[Download]

Abstract: Nowadays, adjustable speed drives are used to improve reliability and energy savings in generating-station auxiliary networks. Electric motors are directly connected to the operating machines ( pumps, fans and blowers ) throttling valves, dampers and adjustable guide vanes, in which mechanical or fluid energy is dissipated or wasted, are no longer used. As a result of the successful developments in the field of Power Electronics, and especially frequency converters, ENEL has opted to conduct studies regarding the experimental installation of large variable-speed drives in its power plants. An analog model has been developed to analyze the behavior of the drives under steady state and transient conditions. Analog simulations were carried out with control units interconnected through optical and analog interfaces to a transient network analyzer ( TNA ). This paper presents the results of studies, developed by CESI and ENEL, aiming at investigating the effects of such applications on typical generating-station auxiliary networks.

   STATIC KRAEMER DRIVE WITH SPECIALLY DESIGNED VOLTAGE INVERTER
By L. S. Ribickis; U. V. Ivbuls; J. P. Greivulis; S. S. Petrov [View]
[Download]

Abstract: The paper presents study results of a special inverter in asynchronous electric drive designed as sub-synchronous static converter cascade circuit (Kraemer drive). The process of the inverter output voltage formation is mathematically described by taking the sum of two saw-tooth mirror-image voltages (Serraphile functions) having a half-cycle phase shift. Harmonic analysis and the synthesis of the voltage shape have been performed. The design and operational concepts of the proposed inverter have been also included.

   A NEW METHOD OF ANALYSIS OF CHOPPER FED DC SERIES MOTOR USING WALSH FUNCTION
By Anish Deb; G. Sarkar; S. K. Sen; A. K. Datta [View]
[Download]

Abstract: A new method of analysis of chopper fed DC series motor is presented using Walsh function. A Walsh Operational Transfer Function (WOTF) is utilized instead of conventional transfer function in a equivalent manner. Output response of average speed and average current is obtained having no restriction on the variations width, frequency and amplitude of the input wave. The results are in close agreement with the experimental values.

   SIMULATION OF THE INPUT-OUTPUT CHARACTERISTICS OF A CYCLOCONVERTER
By Virgil Maier [View]
[Download]

Abstract: The study of cycloconverter - a.c. electric machine drive systems requires adequate mathematical modals for all their elements. Bearings of a complete modelling refer to the solving of certain problems of energetics and optimization of the drive systems as well as to the implementation of command by microprocessor. This paper presents the algorithm for generating the output voltages of the cycloconverters materialized later in a computer program. Instructions for computing the components of the space phasor of the voltages in the (d,q,O) system were provided, too. Thus, the program could be used for the study of the dqO orthogonal components generated by the cycloconverter or could be integrated as a subroutine in a more general program. All the significant computed variables are printed and any of them may be plotted with respect to the time axis.

EPE 1991 - 17 - Session 2.6: HIGH POWER DRIVES
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - Conference > EPE 1991 - 17 - Session 2.6: HIGH POWER DRIVES
	[return to parent folder]

	VARIABLE SPEED PUMPED STORAGE SYSTEM FED BY LARGE-SCALE CYCLOCONVERTER By T. Taguchi; K. Aida; K. Mukai; T. Yanagisawa; T. Kanai	[View] [Download]
Abstract: The world's first variable speed pumped storage system fed by large-scale cycloconverter was brought into operation at the Yagisawa power station Unit 2 of the Tokyo Electric Power Co., Inc. in December, 1990. This remarkable system incorporates the latest large scale, large capacity power electronics technology, ultrahigh-speed digital control technology, and large scale, large capacity generator-motor technology. Actual machine tests carried out at the Yagisawa power station verified various functions of the variable speed pumped storage system, thus allowing the advantages.

	PHASE ANGLE CONTROL OF VOLTAGE SOURCE CONVERTER IN HIGH POWER APPLICATIONS By Lennart Ängquist; Lars Lindberg	[View] [Download]
Abstract: Voltage Source Converters for high-power applications like HVDC and SVC will encourage the use of low commutation frequency which restricts the attainable control performance. In spite of the low switching frequency the control system must be fast-acting In order to handle start-up and different fault conditions. A control strategy is required that brings the converter into stationary state as fast as possible. The paper describes a control method for a voltage source converter. The proposed control method is based on measured converter flux (time integral of converter voltage) and dc voltage, here exemplified in a six pulse unit. The time to next commutation is calculated in real-time so that the converter flux is guided in minimum time from an arbitrary point in the flux plane towards the stationary orbit.

	NEW SYNCHRONIZATION METHOD FOR THYRISTOR POWER CONVERTERS CONNECTED TO WEAK AC-SYSTEMS By R. Wiedenbrug; F. P. Dawson; R. Bonert	[View] [Download]
Abstract: This paper presents a new approach to synchronization for a phase controlled thyristor power converter. Detection of accurate zero crossings are possible even under the following conditions: large frequency change, sudden load changes and large commutation overlap angles. The synchronization is achieved by first reconstructing the reference voltage on the ac source side of the converter transformer. A microcontroller based algorithm is used for this purpose. The reconstructed voltage is subsequently used for synchronization purposes. The improvement provided by the new synchronization scheme is verified experimentally.

	INVESTIGATION OF A DOUBLY-FED INDUCTION GENERATOR USING A SIMPLE CYCLOCONVERTER By H. Härer; U. Horn	[View] [Download]
Abstract: A simple cycloconverter using 6 thyristors for supplying the slipring rotor of an induction generator with variable frequency is described. Due to the supply frequency of the rotor circuit and to the firing sequence of the thyristors, undesirable harmonics may appear in the stator voltage causing light flickers in isolated mains installations such as on board ship or in wind energy generation. These harmonics can be reduced substantially by using suitable firing circuits for the thyristors and by implementing a closed-loop control concept for the rotor circuit. Experimental results as well as simulation results are given.

	AN EXPERIENCE WITH CYCLOCONVERTER - FED IM DRIVES FOR A MODERN TANDEM COLD MILL By M. Hattori; T. Ishikawa; M. Taniguchi; T. Ohnishi; Y. Kurata	[View] [Download]
Abstract: This paper describes the relationship between motor drive performance and strip thickness gauge accuracy in a modern 5 - stand 6 - high tandem cold mill. The tandem cold mill system was recently put into operation at Yawata Works of the Nippon Steel Corp. Each mill stand is driven by a 72 - arm circulating current cycloconverter - fed IM and auxiliaries each are driven by transistor PWM - VSI - fed IMs. The strip thickness gauge accuracy is directly related to the ratio between the speed response and the speed accuracy of the main drive system. In this paper, this relationship is investigated and verified through simulation and experiment. This paper also proposes a new control method for tandem cold mill motor drives to increase the drive system reliability.

	EXPERT SYSTEM FOR DESIGNING CONVERTERS FOR LARGE SYNCHRONOUS MACHINES By S. Ahrens; I. Kortaberria; J. Bigeon; D. Poupart	[View] [Download]
Abstract: This paper presents an expert system tool for fast prototyping and cost estimation of converters for large variable speed drives. It outlines the aims of such a tool for a manufacturer's engineering and sales department. After a brief analysis of the design process we describe the system's approach which is based on artificial intelligence methodology. An example illustrates the flexible way in which the system handles technica! design constraints to optimize the converter's cost price. Finally the knowledge representation scheme and the system's implementation are pointed out.

	A NEW APPROACH TO OPTIMIZED NUMERICAL CONTROL OF LARGE POWER CONVERTERS By S. Diop; J. L. Poulioquen; J. M. Taillardat	[View] [Download]
Abstract: This paper presents a new approach to the numerical control of large power converters, based on a model of the system and open-loop computation of the variables to be controlled. Open-loop computation provides good dynamic performance since the control system does not introduce an additional time constant. Maximum use of the capabilities of digital systems enables the following features to be realized: - control suited to all types of power converter, - power rating optimization, - ease of design and cornmissioning, - ease of use. The new approach is applied to the control of active and reactive power flow with a 50 MW Synchrothyr (1) with efficiency optimization at all operating points.

	MODELLING AND IDENTIFICATION OF A SET OF MULTl-MOTOR DRIVES By F. Parant; C. Coeffier; C. Iung	[View] [Download]
Abstract: The dynamic behaviour of a moving strip in an n-roller system is investigated. The strip passes through several different consecutive sections and is supported, transported and controlled in tension by a multitude of driven rollers. The rollers are driven by induction motor supplied by PWM systems. All of them are coupled mechanically to each other by the material. Starting from an approach of the main system with a partition into m subsystems, an off-line identification of multivariable system parameters is realized. The results obtained by this approach are compared to the experimental results. The method used is efficient to obtain accurate models of a large set of electrical machines coupled by a strip, and can be used in various industrial areas.

	HIGH POWER CYCLOCONVERTER DRIVE FOR DOUBLE-FED INDUCTION MOTORS By G. M. Brown; B. Szabados; R. Belmans	[View] [Download]
Abstract: Two cycloconverters independently supply stator and rotor windings of a wound rotor induction machine. The control strategy to stabilize this inherently unstable system is derived from the double-fed machine matrix and the resulting algorithm is implemented in hardware with a simple field calculator. A practical implementation of a 2 kW drive, illustrates the feasibility of the drive, and practical performances of full speed in both directions, as well as speed ramps up to 700 rpm/s are realized. The system benefits from the simplicity of line-commutated operation associated with a relatively high frequency of operation of each individual cycloconverter, thereby avoiding saturation effects appearing at low frequencies, combined with control of harmonic generation using the extra degree of freedom provided by the DFM.

	TIME SUBOPTIMAL ROTATION SPEED CONTROL OF A THYRISTOR-SUPPLIED DC MOTOR DRIVE By Zeljko Ban; Petar Crnosija	[View] [Download]
Abstract: Various methods of time optimal rotation speed control of a thyristor-supplied direct-current motor drive have been analyzed. The design of a rotation speed control algorithm for a DC motor drive without inner armature current feedback providing suboptimal rotation speed step response has been discussed. An armature current limiting algorithm has also been developed. The control algorithms have been developed separately for the continuous and the discontinuous mode of operation of the thyristor converter. Simulation results have indicated that the algorithms described provide suboptimal rotation speed responses.

	EXPERIMENTAL APPLICATION OF LARGE VARIABLE SPEED DRIVES IN A TYPICAL AUXILIARY POWER SYSTEM By F. Di Maso; C. Raffaelli; M. Rebolini; G. Bergonovo	[View] [Download]
Abstract: Nowadays, adjustable speed drives are used to improve reliability and energy savings in generating-station auxiliary networks. Electric motors are directly connected to the operating machines ( pumps, fans and blowers ) throttling valves, dampers and adjustable guide vanes, in which mechanical or fluid energy is dissipated or wasted, are no longer used. As a result of the successful developments in the field of Power Electronics, and especially frequency converters, ENEL has opted to conduct studies regarding the experimental installation of large variable-speed drives in its power plants. An analog model has been developed to analyze the behavior of the drives under steady state and transient conditions. Analog simulations were carried out with control units interconnected through optical and analog interfaces to a transient network analyzer ( TNA ). This paper presents the results of studies, developed by CESI and ENEL, aiming at investigating the effects of such applications on typical generating-station auxiliary networks.

	STATIC KRAEMER DRIVE WITH SPECIALLY DESIGNED VOLTAGE INVERTER By L. S. Ribickis; U. V. Ivbuls; J. P. Greivulis; S. S. Petrov	[View] [Download]
Abstract: The paper presents study results of a special inverter in asynchronous electric drive designed as sub-synchronous static converter cascade circuit (Kraemer drive). The process of the inverter output voltage formation is mathematically described by taking the sum of two saw-tooth mirror-image voltages (Serraphile functions) having a half-cycle phase shift. Harmonic analysis and the synthesis of the voltage shape have been performed. The design and operational concepts of the proposed inverter have been also included.

	A NEW METHOD OF ANALYSIS OF CHOPPER FED DC SERIES MOTOR USING WALSH FUNCTION By Anish Deb; G. Sarkar; S. K. Sen; A. K. Datta	[View] [Download]
Abstract: A new method of analysis of chopper fed DC series motor is presented using Walsh function. A Walsh Operational Transfer Function (WOTF) is utilized instead of conventional transfer function in a equivalent manner. Output response of average speed and average current is obtained having no restriction on the variations width, frequency and amplitude of the input wave. The results are in close agreement with the experimental values.

	SIMULATION OF THE INPUT-OUTPUT CHARACTERISTICS OF A CYCLOCONVERTER By Virgil Maier	[View] [Download]
Abstract: The study of cycloconverter - a.c. electric machine drive systems requires adequate mathematical modals for all their elements. Bearings of a complete modelling refer to the solving of certain problems of energetics and optimization of the drive systems as well as to the implementation of command by microprocessor. This paper presents the algorithm for generating the output voltages of the cycloconverters materialized later in a computer program. Instructions for computing the components of the space phasor of the voltages in the (d,q,O) system were provided, too. Thus, the program could be used for the study of the dqO orthogonal components generated by the cycloconverter or could be integrated as a subroutine in a more general program. All the significant computed variables are printed and any of them may be plotted with respect to the time axis.