EPE Association: EPE 1993 - 56 - Dialogue Session DS4.5: CONTROL: TRANSDUCERS AND OBSERVERS

EPE 1993 - 56 - Dialogue Session DS4.5: CONTROL: TRANSDUCERS AND OBSERVERS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 56 - Dialogue Session DS4.5: CONTROL: TRANSDUCERS AND OBSERVERS

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   A METHOD TO MONITOR THE THERMAL STRESS OF POWER DEVICES FOR DIRECT STATOR FLUX CONTROLLED AC DRIVES
By G. Hörning [View]
[Download]

Abstract: Frequency inverter induction motor drives with direct stator flux and torque control as the Direct Self Control (DSR) of Depenbrock [1] or the method of Takahashi and Noguchi [2] have very short torque response times. A typical feature of these control methods is the irregular switching sequence of the inverter legs within a cycle of the stator frequency. Since the average switching frequency does not consider this, it is not a measure for the thermal stress of the power devices. To protect them against thermal destruction, a method of on-line monitoring is proposed based on a so called "temperature index" and a "window frequency." By observing the values of temperature index and window frequency for each switching element, an overloading is prevented, including possible cases of fault. When temperature index or window frequency are reaching their limits, the inverter can be turned off in time. This ensures a safe operation of the drive. In addition, digital simulation results show an improved operational performance, which can be achieved by this method.

   IMPLEMENTATION OF EXTENDED LUENBERGER OBSERVERS FOR JOINT STATE AND PARAMETER ESTIMATION OF PWM INDUCTION MOTOR DRIVE
By T. Du; M. A. Brdys [View]
[Download]

Abstract: The paper presents practical implementation results of three full-order extended Luenberger observers (FELOs) for joint state and parameter estimation of a PWM induction motor drive. Ob-I is for joint rotor time constant and rotor flux estimation, Ob-II for joint shaft speed and rotor flux estimation, and Ob-Ill for joint shaft speed, load torque as well as rotor flux estimation. The advantages of FELOs over extended Kalman filters are pointed out. The results show that the extended Luenberger observers are able to work satisfactorily in practical industry environment, generating the estimates with fast dynamics.

   REAL-TIME CURRENT ESTIMATION IN BRUSHLESS DC DRIVES USING A SINGLE DC-LINK CURRENT SENSOR
By C. D. French; P. P. Acarnley; A. G. Jack [View]
[Download]

Abstract: The classical method of current control in a three phase inverter is to compare current demand with actual winding current, where the winding current is obtained by direct measurments on the motor windings. This method of current measurement relies upon total uniformity of current sensors, to achieve a balanced output. The problem of current sensor imbalance can lead to unacceptable torque ripple at low speeds. By using a single sensor located on the dc-link, there is inherent balance. Due to the chopping action of the inverter, current cannot always be directly measured at the dc-link. This paper describes an observer based system that uses a motor / converter model to estimate this flywheeling current. When the winding current can be directly measured at the dc-link, the observer updates its system model in a closed loop manner. The observer is implemented in real-time using a DSP ( Digital Signal Processor ) based system. Full steadystate & transient results are described.

   A COMPACT WIDEBAND CURRENT SHUNT
By M. J. Case; J. J. Schoeman [View]
[Download]

Abstract: The need remains for wideband shunts in various measurement functions, despite the advent of current-measuring devices based on phenomena making use of more than Ohms' Law. This paper describes a shunt of circular form no more than 6 mm thick with a bandwidth comparable to standard co-axial structures. The internal construction is such that the signal-carrying conductors exist only in a field-free region, while the current-carrying structure is of simple construction. The form of the shunt makes it particularly suitable for mounting in series with a hockey-puck semiconductor, or in line with a substantial busbar.

   ESTIMATION OF MECHANICAL SIGNALS IN INDUCTION MOTORS USING THE RECURSIVE PREDICTION ERROR METHOD
By H. Borsting; M. Knudsen; H. Rasmussen; P. Vadstrup [View]
[Download]

Abstract: Sensor feedback of mechanical quantities for control applications in induction motors is troublesome and relative expensive. In this paper a recursive prediction error (RPE) method has successfully been used to estimate the angular rotor speed w and the driving torque Td in an induction motor. The signals are estimated from measurements of stator voltages and currents only, without any knowledge of the load. The performance of the estimator is evaluated by comparing the estimated signals by the measured ones. The RPE method is guaranteed convergence in contradiction to the Extended Kalman filter which is frequently used for joint parameter and state estimation in induction motors. A modified structure of the motor model has shown to improve the performance of the estimator.

   WAVEFORM SUPERVISION POWER PHASE CONVERTER OF TIME CONTROLLED RECTIFIERS: A REAL OPERATION SURVEILLANCE
By E. P. Wiechmann; A. R. Garcia; J. R. Rodriguez; E. O. Amthauer; R. W. Sanchez [View]
[Download]

Abstract: The concept of waveform supervision for power converters is analyzed. Overall system reliability is improved reducing the number of feedback signals required by conventional fault diagnosis units. Waveform supervision allows diagnosis of abnormal operation and fault. Detection is based on a real time error signal produced by comparison between real time simulated and acquired data. The error is compared with characteristic anomalous signal patterns to produce a diagnosis. The system offers accurate converter operation diagnosis. Experimental results obtained with a laboratory prototype are presented.

   A FAULT DETECTION PROCEDURE FOR SINGLE PHASE BRIDGE CONVERTERS
By E. Craig; B. C. Mecrow; D. J. Atkinson; A. G. Jack [View]
[Download]

Abstract: The use of multiple single phase bridges has fault tolerant benefits in high reliability permanent magnet drives for use in safety critical applications. This paper describes a technique which continuously monitors the condition of a single phase bridge, using a single additional current sensor positioned to pick up only the fly wheeling currents around the bridge. Correlation of the device firing signals, phase Current direction and fly wheeling currents enable a fault to be detected. The system identifies the faulted device and its mode of failure, within the short circuit withstand time of the power devices. Accurate knowledge of the nature of the failure allows the bridge controller to take appropriate action to avoid propagation of the fault, which may lead to catastrophic failure of the bridge, affecting the power rails and associated systems. Results of an experimental bridge, incorporating the fault detection system, demonstrate the effectiveness of the technique when the bridge devices have severe open or short circuit faults.

   A DIGITAL TRACKING R/D CONVERTER WITH HARDWARE ERROR CALCULATION USING A TMS320C14
By B. A. Murray; W. D. Li [View]
[Download]

Abstract: The resolver is a very robust and cost-effective angular position transducer. The outputs can be transmitted through very long distances, without severe corruption by noise, before being processed. A resolver to digital converter is designed, using the TMS320C14 digital signal processing microcomputer, to provide absolute angular position and velocity information for digital servo control systems. The converter is substantially implemenled in software as a replacement for the resolver to digital converter IC's normally used. The demodulation and error calculation functions are performed in hardware to optimise the low speed performance of the system. The paper describes the development of the converter algorithm and the error calculation hardware. Results of both simulation and the experimental converter system are presented.

   CURRENT MEASUREMENT IN STATIC CONVERTERS AND REALIZATION OF A HIGH FREQUENCY PASSIVE CURRENT PROBE (50A-300MHz)
By E. Labouré; F. Costa; F. Forest [View]
[Download]

Abstract: The measurement of currents in static converters and specially the analysis of switching phenomena in semiconductor devices make necessary the use of current probe with large frequency bandwidth, high currents capability and low electromagnetic susceptibility (Typical stress values in medium power converters: I: 50A RMS; dl/dt: 1000A/μs; dV/dt: 10kV/μs). The first part of this paper concerns the description of current measurement techniques. We show why current transformer is a good way to measure current. An elementary structure based on a ferrite core, a winding and a resistor load is first tested. A high frequcncy electrical model is presented. It is used in numerical simulation of the frequency response and allows to pick the more significant parameters. We analyze the way of improving electrical performances and the electromagnetic susceptibility. Then we show some experimental results obtained with such current probe.

EPE 1993 - 56 - Dialogue Session DS4.5: CONTROL: TRANSDUCERS AND OBSERVERS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 56 - Dialogue Session DS4.5: CONTROL: TRANSDUCERS AND OBSERVERS
	[return to parent folder]

	A METHOD TO MONITOR THE THERMAL STRESS OF POWER DEVICES FOR DIRECT STATOR FLUX CONTROLLED AC DRIVES By G. Hörning	[View] [Download]
Abstract: Frequency inverter induction motor drives with direct stator flux and torque control as the Direct Self Control (DSR) of Depenbrock [1] or the method of Takahashi and Noguchi [2] have very short torque response times. A typical feature of these control methods is the irregular switching sequence of the inverter legs within a cycle of the stator frequency. Since the average switching frequency does not consider this, it is not a measure for the thermal stress of the power devices. To protect them against thermal destruction, a method of on-line monitoring is proposed based on a so called "temperature index" and a "window frequency." By observing the values of temperature index and window frequency for each switching element, an overloading is prevented, including possible cases of fault. When temperature index or window frequency are reaching their limits, the inverter can be turned off in time. This ensures a safe operation of the drive. In addition, digital simulation results show an improved operational performance, which can be achieved by this method.

	IMPLEMENTATION OF EXTENDED LUENBERGER OBSERVERS FOR JOINT STATE AND PARAMETER ESTIMATION OF PWM INDUCTION MOTOR DRIVE By T. Du; M. A. Brdys	[View] [Download]
Abstract: The paper presents practical implementation results of three full-order extended Luenberger observers (FELOs) for joint state and parameter estimation of a PWM induction motor drive. Ob-I is for joint rotor time constant and rotor flux estimation, Ob-II for joint shaft speed and rotor flux estimation, and Ob-Ill for joint shaft speed, load torque as well as rotor flux estimation. The advantages of FELOs over extended Kalman filters are pointed out. The results show that the extended Luenberger observers are able to work satisfactorily in practical industry environment, generating the estimates with fast dynamics.

	REAL-TIME CURRENT ESTIMATION IN BRUSHLESS DC DRIVES USING A SINGLE DC-LINK CURRENT SENSOR By C. D. French; P. P. Acarnley; A. G. Jack	[View] [Download]
Abstract: The classical method of current control in a three phase inverter is to compare current demand with actual winding current, where the winding current is obtained by direct measurments on the motor windings. This method of current measurement relies upon total uniformity of current sensors, to achieve a balanced output. The problem of current sensor imbalance can lead to unacceptable torque ripple at low speeds. By using a single sensor located on the dc-link, there is inherent balance. Due to the chopping action of the inverter, current cannot always be directly measured at the dc-link. This paper describes an observer based system that uses a motor / converter model to estimate this flywheeling current. When the winding current can be directly measured at the dc-link, the observer updates its system model in a closed loop manner. The observer is implemented in real-time using a DSP ( Digital Signal Processor ) based system. Full steadystate & transient results are described.

	A COMPACT WIDEBAND CURRENT SHUNT By M. J. Case; J. J. Schoeman	[View] [Download]
Abstract: The need remains for wideband shunts in various measurement functions, despite the advent of current-measuring devices based on phenomena making use of more than Ohms' Law. This paper describes a shunt of circular form no more than 6 mm thick with a bandwidth comparable to standard co-axial structures. The internal construction is such that the signal-carrying conductors exist only in a field-free region, while the current-carrying structure is of simple construction. The form of the shunt makes it particularly suitable for mounting in series with a hockey-puck semiconductor, or in line with a substantial busbar.

	ESTIMATION OF MECHANICAL SIGNALS IN INDUCTION MOTORS USING THE RECURSIVE PREDICTION ERROR METHOD By H. Borsting; M. Knudsen; H. Rasmussen; P. Vadstrup	[View] [Download]
Abstract: Sensor feedback of mechanical quantities for control applications in induction motors is troublesome and relative expensive. In this paper a recursive prediction error (RPE) method has successfully been used to estimate the angular rotor speed w and the driving torque Td in an induction motor. The signals are estimated from measurements of stator voltages and currents only, without any knowledge of the load. The performance of the estimator is evaluated by comparing the estimated signals by the measured ones. The RPE method is guaranteed convergence in contradiction to the Extended Kalman filter which is frequently used for joint parameter and state estimation in induction motors. A modified structure of the motor model has shown to improve the performance of the estimator.

	WAVEFORM SUPERVISION POWER PHASE CONVERTER OF TIME CONTROLLED RECTIFIERS: A REAL OPERATION SURVEILLANCE By E. P. Wiechmann; A. R. Garcia; J. R. Rodriguez; E. O. Amthauer; R. W. Sanchez	[View] [Download]
Abstract: The concept of waveform supervision for power converters is analyzed. Overall system reliability is improved reducing the number of feedback signals required by conventional fault diagnosis units. Waveform supervision allows diagnosis of abnormal operation and fault. Detection is based on a real time error signal produced by comparison between real time simulated and acquired data. The error is compared with characteristic anomalous signal patterns to produce a diagnosis. The system offers accurate converter operation diagnosis. Experimental results obtained with a laboratory prototype are presented.

	A FAULT DETECTION PROCEDURE FOR SINGLE PHASE BRIDGE CONVERTERS By E. Craig; B. C. Mecrow; D. J. Atkinson; A. G. Jack	[View] [Download]
Abstract: The use of multiple single phase bridges has fault tolerant benefits in high reliability permanent magnet drives for use in safety critical applications. This paper describes a technique which continuously monitors the condition of a single phase bridge, using a single additional current sensor positioned to pick up only the fly wheeling currents around the bridge. Correlation of the device firing signals, phase Current direction and fly wheeling currents enable a fault to be detected. The system identifies the faulted device and its mode of failure, within the short circuit withstand time of the power devices. Accurate knowledge of the nature of the failure allows the bridge controller to take appropriate action to avoid propagation of the fault, which may lead to catastrophic failure of the bridge, affecting the power rails and associated systems. Results of an experimental bridge, incorporating the fault detection system, demonstrate the effectiveness of the technique when the bridge devices have severe open or short circuit faults.

	A DIGITAL TRACKING R/D CONVERTER WITH HARDWARE ERROR CALCULATION USING A TMS320C14 By B. A. Murray; W. D. Li	[View] [Download]
Abstract: The resolver is a very robust and cost-effective angular position transducer. The outputs can be transmitted through very long distances, without severe corruption by noise, before being processed. A resolver to digital converter is designed, using the TMS320C14 digital signal processing microcomputer, to provide absolute angular position and velocity information for digital servo control systems. The converter is substantially implemenled in software as a replacement for the resolver to digital converter IC's normally used. The demodulation and error calculation functions are performed in hardware to optimise the low speed performance of the system. The paper describes the development of the converter algorithm and the error calculation hardware. Results of both simulation and the experimental converter system are presented.

	CURRENT MEASUREMENT IN STATIC CONVERTERS AND REALIZATION OF A HIGH FREQUENCY PASSIVE CURRENT PROBE (50A-300MHz) By E. Labouré; F. Costa; F. Forest	[View] [Download]
Abstract: The measurement of currents in static converters and specially the analysis of switching phenomena in semiconductor devices make necessary the use of current probe with large frequency bandwidth, high currents capability and low electromagnetic susceptibility (Typical stress values in medium power converters: I: 50A RMS; dl/dt: 1000A/μs; dV/dt: 10kV/μs). The first part of this paper concerns the description of current measurement techniques. We show why current transformer is a good way to measure current. An elementary structure based on a ferrite core, a winding and a resistor load is first tested. A high frequcncy electrical model is presented. It is used in numerical simulation of the frequency response and allows to pick the more significant parameters. We analyze the way of improving electrical performances and the electromagnetic susceptibility. Then we show some experimental results obtained with such current probe.