EPE Association: EPE 1993 - 11 - Lecture Session L4b: CONTROL: PWM TECHNIQUES, VECTOR CONTROL

EPE 1993 - 11 - Lecture Session L4b: CONTROL: PWM TECHNIQUES, VECTOR CONTROL
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 11 - Lecture Session L4b: CONTROL: PWM TECHNIQUES, VECTOR CONTROL

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   DESIGN AND IMPLEMENTATION OF A PULSE WIDTH MODULATOR FOR A THREE LEVEL INVERTER USING A MICROPROCESSOR AND EPLDS
By E. K. H. van der Pols; J. D. L. Haesakkers [View]
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Abstract: In the development of a megawatt drive for asynchronous machines using a three-level GTO-inverter, a new pulse width modulator (PWM) has been designed and implemented. The PWM consists of a pattern generator, a special test pattern generator, and an inverter interface. The pattern generator produces space vector modulated and pulse number modulated phase switching state patterns. User defined test patterns are produced by the test pattern generator to allow easy testing of inverter units. The inverter interface uses GTO state feedback signals to transform the phase state or test patterns into GTO command signals. The PWM is equipped with extensive diagnostic facilities, including a GTO timing analyzer. The implementation of the PWM is based on an 68000 microprocessor and various EPLDs for the protective and speed requiring functions. The use of EPLDs has a software-like flexibility in implementation. Tests on the prototype drive system have shown excellent behaviour.

   SPACE VECTOR PWM STRATEGY FOR 3-LEVEL INVERTERS WITH DIRECT SELF-CONTROL
By A. M. Walczyna; R. J. Hill [View]
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Abstract: A novel pulse width modulation (PWM) strategy for induction motor drives with direct self-control and a free-running 2-level torque controller is descrlbed. The technique is based on space vector modulation achieved with look-up tables and logic circuits. The method is very flexible allowing the generation of many PWM patterns, including switching preferences and avoiding 3-level inverter switching collisions. In the paper, detailed consideration is given to the PWM patterns consisting of full, intermediate and half voltage vectors. The techniques of generating a dodecagonal flux trajectory and of reducing stator current reactive distortion with 2-level torque control are demonstrated. Methods for neutral point voltage control are proposed and the problem of a drive transition from a 6-pulse to a 12-pulse mode is discussed. The properties of the method are illustrated by simulation of a high-power traction drive.

   REALIZATION OF A HIGH-DYNAMIC DISCRETE-TIME CONTROLLER FOR PWM INVERTER-FED INDUCTION MOTOR DRIVES
By J. Böcker; J. Janning; K. Anbuhl [View]
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Abstract: This paper describes a controller of a PWM inverter-fed induction motor drive based on the well known principle of rotor flux orientation. A new aspect is the homogeneous discrete-time design of the complete control structure including measurement data acquisition and pulse width modulation. A discrete-time flux observer ensures accurate flux orientation even at standstill and additionally supplies one-step-ahead predicted current estimates, which compensates for computational delay. By these discrete-time considerations computing power can be saved whereas optimal control performance can be reached. This control structure covers very different requirements of practical interest as smooth slow motion and operation at standstill as well as operations in the range of high flux weakening (up to ratios of 1:3 ... 5 or more). In constant-flux range torque response times of about 5 ms are reached. Even at a flux weakening ratio of up to 1:3.5 a torque response time of 15 ... 20 ms was measured. The controller bas been successfully proved in several drives up to a power of 960 kW. In all operation modes the control characteristics are comparable with those of DC drives.

   A FLUX CONTROLLER THAT IMPROVES DRIVE SYSTEM PERFORMANCE BY ACCOUNTING FOR MAGNETIC CIRCUIT SATURATION
By H. C. Lovatt [View]
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Abstract: This paper gives a theoretical and experimental comparison between three types of inner control loop strategy: a hysteresis current controller, a PID current controller, and a new design of flux linkage controller. The new controller uses a non-linear feedback element to linearize the inner loop. The paper concludes that the new controller bas significant advantages over the other two strategies when controlling magnetic circuits that are driven into saturation. However, it is the most complicated to implement, with extra circuitry required to estimate the flux linkage. The reluctance machine drive is used as one example of a system with a saturating magnetic circuit.

EPE 1993 - 11 - Lecture Session L4b: CONTROL: PWM TECHNIQUES, VECTOR CONTROL
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 11 - Lecture Session L4b: CONTROL: PWM TECHNIQUES, VECTOR CONTROL
	[return to parent folder]

	DESIGN AND IMPLEMENTATION OF A PULSE WIDTH MODULATOR FOR A THREE LEVEL INVERTER USING A MICROPROCESSOR AND EPLDS By E. K. H. van der Pols; J. D. L. Haesakkers	[View] [Download]
Abstract: In the development of a megawatt drive for asynchronous machines using a three-level GTO-inverter, a new pulse width modulator (PWM) has been designed and implemented. The PWM consists of a pattern generator, a special test pattern generator, and an inverter interface. The pattern generator produces space vector modulated and pulse number modulated phase switching state patterns. User defined test patterns are produced by the test pattern generator to allow easy testing of inverter units. The inverter interface uses GTO state feedback signals to transform the phase state or test patterns into GTO command signals. The PWM is equipped with extensive diagnostic facilities, including a GTO timing analyzer. The implementation of the PWM is based on an 68000 microprocessor and various EPLDs for the protective and speed requiring functions. The use of EPLDs has a software-like flexibility in implementation. Tests on the prototype drive system have shown excellent behaviour.

	SPACE VECTOR PWM STRATEGY FOR 3-LEVEL INVERTERS WITH DIRECT SELF-CONTROL By A. M. Walczyna; R. J. Hill	[View] [Download]
Abstract: A novel pulse width modulation (PWM) strategy for induction motor drives with direct self-control and a free-running 2-level torque controller is descrlbed. The technique is based on space vector modulation achieved with look-up tables and logic circuits. The method is very flexible allowing the generation of many PWM patterns, including switching preferences and avoiding 3-level inverter switching collisions. In the paper, detailed consideration is given to the PWM patterns consisting of full, intermediate and half voltage vectors. The techniques of generating a dodecagonal flux trajectory and of reducing stator current reactive distortion with 2-level torque control are demonstrated. Methods for neutral point voltage control are proposed and the problem of a drive transition from a 6-pulse to a 12-pulse mode is discussed. The properties of the method are illustrated by simulation of a high-power traction drive.

	REALIZATION OF A HIGH-DYNAMIC DISCRETE-TIME CONTROLLER FOR PWM INVERTER-FED INDUCTION MOTOR DRIVES By J. Böcker; J. Janning; K. Anbuhl	[View] [Download]
Abstract: This paper describes a controller of a PWM inverter-fed induction motor drive based on the well known principle of rotor flux orientation. A new aspect is the homogeneous discrete-time design of the complete control structure including measurement data acquisition and pulse width modulation. A discrete-time flux observer ensures accurate flux orientation even at standstill and additionally supplies one-step-ahead predicted current estimates, which compensates for computational delay. By these discrete-time considerations computing power can be saved whereas optimal control performance can be reached. This control structure covers very different requirements of practical interest as smooth slow motion and operation at standstill as well as operations in the range of high flux weakening (up to ratios of 1:3 ... 5 or more). In constant-flux range torque response times of about 5 ms are reached. Even at a flux weakening ratio of up to 1:3.5 a torque response time of 15 ... 20 ms was measured. The controller bas been successfully proved in several drives up to a power of 960 kW. In all operation modes the control characteristics are comparable with those of DC drives.

	A FLUX CONTROLLER THAT IMPROVES DRIVE SYSTEM PERFORMANCE BY ACCOUNTING FOR MAGNETIC CIRCUIT SATURATION By H. C. Lovatt	[View] [Download]
Abstract: This paper gives a theoretical and experimental comparison between three types of inner control loop strategy: a hysteresis current controller, a PID current controller, and a new design of flux linkage controller. The new controller uses a non-linear feedback element to linearize the inner loop. The paper concludes that the new controller bas significant advantages over the other two strategies when controlling magnetic circuits that are driven into saturation. However, it is the most complicated to implement, with extra circuitry required to estimate the flux linkage. The reluctance machine drive is used as one example of a system with a saturating magnetic circuit.