EPE Association: EPE 1991 - 14 - Session 2.3: PWM TECHNIQUES

EPE 1991 - 14 - Session 2.3: PWM TECHNIQUES
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - Conference > EPE 1991 - 14 - Session 2.3: PWM TECHNIQUES

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   A FAST SPACE-VECTOR CONTROL FOR A THREE-LEVEL VOLTAGE SOURCE INVERTER
By R. Joetten; Chr. Kehl [View]
[Download]

Abstract: The three-level-principle is attractive also for voltage source inverters with transistors, aiming at loss reduction in high speed induction machines. If high control performance is demanded, space vector control becomes desirable, and the task becomes time critical. A new method is implemented with a signal processor Tl TMS32010 and experimentally verified with a transistor inverter, with base frequency 400 Hz, 12-step operation up to 800 Hz and a smooth transition into the 12-step range. Further features are angle control in this range and the possibility to handle also variable direct voltage in the base speed range.

   A PWM CONTROL METHOD USING PULSE FREQUENCY MODULATION TECHNIQUE
By Yoshitaka Iwaji; Shoji Fukuda [View]
[Download]

Abstract: This paper describes a PWM pulse pattern optimization method utilizing the pulse frequency modulation (PFM). In conventional PWMs the pulse frequency is kept constant. In the proposed scheme, however, the pulse frequency is adjusted to improve the performance of PWM sinusoidal inverters. The PWM pulse patterns are basically controlled so that the time-integral function of the output voltage in the space vector representation may draw a circular locus. In addition to this, the pulse frequency as well as the pulse width are controlled so that the performance index (PI), which represents the degrees of achieved objectives, may be minimized. In this paper, two PIs, one for minimizing the distortion of the output currents and the other for minimizing the torque pulsation of driven motors, are employed. The method is finally implemented using a single-chip microprocessor, and the experimental results demonstrate its validity.

   DESIGN ASPECTS OF HIGH POWER PWM INVERTERS WITH IGBT
By Yehia Tadros; Günter Junge; Samir Salama [View]
[Download]

Abstract: The advantages of application of IGBT in PWM inverters for the medium power range with inverter power capacity up to 50 kW are now well known. The available high current IGBT modules with voltages up to 1200 V and currents up to 400 A allow inverter power up to about 100 kW. With the help of parallel circuits and/or using a three level inverter the power range can be extended to several hundred kW. In this contribution the problems associated with the resulting high currents and high rate of rise of currents and voltages will be discussed. Practical solutions for safe operation in the high power range will be presented. The advantages of a realized three level IGBT inverter compared with two level GTO inverter will be demonstrated.

   OPTIMUM CONTROL OF PWM RECTIFIERS FOR MAGNET SUPPLY
By D. Ciscato; L. Malesani; L. Storari; L. Rossetto; P. Tenti; G. L. Basile; F. Voelker [View]
[Download]

Abstract: The paper presente a very low current ripple PWM rectifier for supply of particle accelerator magnets. The modulation technique is based on the feed-forward optimum control theory [1,2], and is implemented by means of a high-performance micro-controller, which also generates the PWM control of the converter switches. The proposed solution consists in a single-stage step-down totally-controlled GTO converter, and uses the Intel 80C196KC micro-controller. The optimum control strategy ensures minimum low frequency output voltage ripple and maximum input power factor irrespective of the line voltage distortion. Design criteria and control implementation are described. Experimental results are given for a 15 kW prototype.

   ANALYSIS OF THE CONTROL BEHAVIOR OF A BIDIRECTIONAL THREE-PHASE PWM RECTIFIER SYSTEM
By Johann W. Kolar; Hans Ertl; Karl Edelmoser; Franz C. Zach [View]
[Download]

Abstract: This paper treats the analysis of the control-oriented system structure and the dynamic quality of a three-phase PWM rectifier system. Based on the application of the space vector calculus one can give a clear and simple mathematical description of the power electronic system. The transformation into a (rotating) d,q-coordinate system oriented with respect to the mains voltage space vector leads to a split of the mains current into two parts. One part determines the contribution which gives the required power flow into the DC bus, the other part defines the instantaneous reactive power condition in the mains. Furthermore the system equations show directly the possibility of the control of both current components in a decoupled manner. This makes a realization of the system control in form of a cascade structure reasonable. Thereby also the possibility of a simple realization of current limitation and a feedforward control of the load behavior is possible. As more detailed research shows one has to pay special attention to the voltage control loop which is superimposed on the current control loop. The small-signal transfer function of the system to be controlled by the voltage controller shows (for energy flow from the mains into the DC voltage bus) a zero located in the right s-half-plane. This is equivalent to allpass behavior. This behavior can be interpreted in a physical sense via the then given system function as step-up (boost) converter: Fora power flow from the DC link into the mains the system acts as a buck-converter. Accordingly, the system zero then lies in the left s-half-plane. Besides the dependency of the location of the poles and zeros on the system load condition the following aspects of the system are investigated: (1) the influence of the dimensioning of the mains-side inductances and of the capacitor buffering the DC voltage on the dynamic behavior, (2) possibilities of feedforward control based on the load and mains voltage conditions and (3) the design of a DC link current controller for prediction of the system response to a change in the controller output signal by a SMITH-predictor.

   A SPACE VECTOR-BASED RECTIFIER REGULATOR FOR AC/DC/AC CONVERTERS
By Thomas G. Habetler [View]
[Download]

Abstract: A voltage sourced rectifier control scheme for use with ac / dc / ac variable speed drives is presented in this paper. A control scheme is derived which directly calculates the duration of time spent on the zero state and on each switching state adjacent to the reference vector, over a constant switching interval, in order to drive the line current vector to the reference vector. In addition, under transient conditions, when dead-beat control is not possible, a control scheme is presented which ensures the line current vector is driven in the direction of the reference current vector. The current reference for the rectifier controller is derived from the bus voltage error and a feedforward term based on the estimated converter output power. The proposed space vector-based rectifier regulator is shown to exhibit improved harmonic and transient performance over existing per-phase duty cycle prediction methods, especially at modulation indices near unity. The dead-beat control of the rectifier input current is accomplished every half-cycle with constant switching frequency, while still symmetrically distributing the zero state within the halfcycle period. In this way, satisfactory performance under various operating conditions is achieved with relatively low switching frequencies and high bus yoltage ripple.

EPE 1991 - 14 - Session 2.3: PWM TECHNIQUES
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - Conference > EPE 1991 - 14 - Session 2.3: PWM TECHNIQUES
	[return to parent folder]

	A FAST SPACE-VECTOR CONTROL FOR A THREE-LEVEL VOLTAGE SOURCE INVERTER By R. Joetten; Chr. Kehl	[View] [Download]
Abstract: The three-level-principle is attractive also for voltage source inverters with transistors, aiming at loss reduction in high speed induction machines. If high control performance is demanded, space vector control becomes desirable, and the task becomes time critical. A new method is implemented with a signal processor Tl TMS32010 and experimentally verified with a transistor inverter, with base frequency 400 Hz, 12-step operation up to 800 Hz and a smooth transition into the 12-step range. Further features are angle control in this range and the possibility to handle also variable direct voltage in the base speed range.

	A PWM CONTROL METHOD USING PULSE FREQUENCY MODULATION TECHNIQUE By Yoshitaka Iwaji; Shoji Fukuda	[View] [Download]
Abstract: This paper describes a PWM pulse pattern optimization method utilizing the pulse frequency modulation (PFM). In conventional PWMs the pulse frequency is kept constant. In the proposed scheme, however, the pulse frequency is adjusted to improve the performance of PWM sinusoidal inverters. The PWM pulse patterns are basically controlled so that the time-integral function of the output voltage in the space vector representation may draw a circular locus. In addition to this, the pulse frequency as well as the pulse width are controlled so that the performance index (PI), which represents the degrees of achieved objectives, may be minimized. In this paper, two PIs, one for minimizing the distortion of the output currents and the other for minimizing the torque pulsation of driven motors, are employed. The method is finally implemented using a single-chip microprocessor, and the experimental results demonstrate its validity.

	DESIGN ASPECTS OF HIGH POWER PWM INVERTERS WITH IGBT By Yehia Tadros; Günter Junge; Samir Salama	[View] [Download]
Abstract: The advantages of application of IGBT in PWM inverters for the medium power range with inverter power capacity up to 50 kW are now well known. The available high current IGBT modules with voltages up to 1200 V and currents up to 400 A allow inverter power up to about 100 kW. With the help of parallel circuits and/or using a three level inverter the power range can be extended to several hundred kW. In this contribution the problems associated with the resulting high currents and high rate of rise of currents and voltages will be discussed. Practical solutions for safe operation in the high power range will be presented. The advantages of a realized three level IGBT inverter compared with two level GTO inverter will be demonstrated.

	OPTIMUM CONTROL OF PWM RECTIFIERS FOR MAGNET SUPPLY By D. Ciscato; L. Malesani; L. Storari; L. Rossetto; P. Tenti; G. L. Basile; F. Voelker	[View] [Download]
Abstract: The paper presente a very low current ripple PWM rectifier for supply of particle accelerator magnets. The modulation technique is based on the feed-forward optimum control theory [1,2], and is implemented by means of a high-performance micro-controller, which also generates the PWM control of the converter switches. The proposed solution consists in a single-stage step-down totally-controlled GTO converter, and uses the Intel 80C196KC micro-controller. The optimum control strategy ensures minimum low frequency output voltage ripple and maximum input power factor irrespective of the line voltage distortion. Design criteria and control implementation are described. Experimental results are given for a 15 kW prototype.

	ANALYSIS OF THE CONTROL BEHAVIOR OF A BIDIRECTIONAL THREE-PHASE PWM RECTIFIER SYSTEM By Johann W. Kolar; Hans Ertl; Karl Edelmoser; Franz C. Zach	[View] [Download]
Abstract: This paper treats the analysis of the control-oriented system structure and the dynamic quality of a three-phase PWM rectifier system. Based on the application of the space vector calculus one can give a clear and simple mathematical description of the power electronic system. The transformation into a (rotating) d,q-coordinate system oriented with respect to the mains voltage space vector leads to a split of the mains current into two parts. One part determines the contribution which gives the required power flow into the DC bus, the other part defines the instantaneous reactive power condition in the mains. Furthermore the system equations show directly the possibility of the control of both current components in a decoupled manner. This makes a realization of the system control in form of a cascade structure reasonable. Thereby also the possibility of a simple realization of current limitation and a feedforward control of the load behavior is possible. As more detailed research shows one has to pay special attention to the voltage control loop which is superimposed on the current control loop. The small-signal transfer function of the system to be controlled by the voltage controller shows (for energy flow from the mains into the DC voltage bus) a zero located in the right s-half-plane. This is equivalent to allpass behavior. This behavior can be interpreted in a physical sense via the then given system function as step-up (boost) converter: Fora power flow from the DC link into the mains the system acts as a buck-converter. Accordingly, the system zero then lies in the left s-half-plane. Besides the dependency of the location of the poles and zeros on the system load condition the following aspects of the system are investigated: (1) the influence of the dimensioning of the mains-side inductances and of the capacitor buffering the DC voltage on the dynamic behavior, (2) possibilities of feedforward control based on the load and mains voltage conditions and (3) the design of a DC link current controller for prediction of the system response to a change in the controller output signal by a SMITH-predictor.

	A SPACE VECTOR-BASED RECTIFIER REGULATOR FOR AC/DC/AC CONVERTERS By Thomas G. Habetler	[View] [Download]
Abstract: A voltage sourced rectifier control scheme for use with ac / dc / ac variable speed drives is presented in this paper. A control scheme is derived which directly calculates the duration of time spent on the zero state and on each switching state adjacent to the reference vector, over a constant switching interval, in order to drive the line current vector to the reference vector. In addition, under transient conditions, when dead-beat control is not possible, a control scheme is presented which ensures the line current vector is driven in the direction of the reference current vector. The current reference for the rectifier controller is derived from the bus voltage error and a feedforward term based on the estimated converter output power. The proposed space vector-based rectifier regulator is shown to exhibit improved harmonic and transient performance over existing per-phase duty cycle prediction methods, especially at modulation indices near unity. The dead-beat control of the rectifier input current is accomplished every half-cycle with constant switching frequency, while still symmetrically distributing the zero state within the halfcycle period. In this way, satisfactory performance under various operating conditions is achieved with relatively low switching frequencies and high bus yoltage ripple.