### Abstract

This thesis deals with energy optimal control of small and medium-size variable speed induction motor drives for especially Heating, Ventilation and Air-Condition (HVAC) applications. Optimized efficiency is achieved by adapting the magnetization level in the motor to the load, and the basic purpose is demonstrate how this can be done for low-cost PWM-VSI drives without bringing the robustness of the drive below an acceptable level.

Four drives are investigated with respect to energy optimal control: 2.2 kW standard and high-efficiency motor drives, 22 kW and 90 kW standard motor drives. The method has been to make extensive efficiency measurements within the specified operating area with optimized efficiency and with constant air-gap flux, and to establish reliable converter and motor loss models based on those measurements. The loss models have been used to analyze energy optimal control strategies by different steady-state calculations. Several control strategies were implemented and tested on a 2.2 kW scalar drive, both with respect to steady-state efficiency, convergence time in case of changing load, response to a large sudden load disturbance, and energy consumption in a realistic pump system. The dynamic performances were also evaluated in a vector controlled drive for CT applications. Based on these tests, the displacement power factor control and the direct air-gap flux control appeared to be best for small HVAC applications.

Energy optimal control of medium-size drives was analyzed separately to investigate the influence of converter losses. A new model-based control principle is proposed which can include converter losses, which does not depend on an analytical solution and which does only requires little computational power. A relation is established which can predict the efficiency improvement by energy optimal control for any standard induction motor drive between 2.2 kW and 90 kW.

A simple method to evaluate the robustness against load disturbances was developed and used to compare the robustness of different motor types and sizes. Calculation of the oscillatory behavior of a motor demonstrated that energy optimal control will sometimes improve and sometimes deteriorate the stability.

Comparison of small and medium-size induction motor drives with permanent magnet motor drives indicated why, and in which applications, PM motors are especially good. Calculations of economical aspects demonstrated the small difference in savings between the different motor types in a variable speed drive, compared with the constant speed drive.

Original language | English |
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Place of Publication | Aalborg |
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Publisher | Institut for Energiteknik, Aalborg Universitet |

Number of pages | 216 |

ISBN (Print) | 87-89179-26-9 |

Publication status | Published - 2000 |

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### Cite this

*Energy Optimal Control of Induction Motor Drives*. Aalborg: Institut for Energiteknik, Aalborg Universitet.

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*Energy Optimal Control of Induction Motor Drives*. Institut for Energiteknik, Aalborg Universitet, Aalborg.

**Energy Optimal Control of Induction Motor Drives.** / Abrahamsen, Flemming.

Research output: Book/Report › Ph.D. thesis › Research

TY - BOOK

T1 - Energy Optimal Control of Induction Motor Drives

AU - Abrahamsen, Flemming

PY - 2000

Y1 - 2000

N2 - This thesis deals with energy optimal control of small and medium-size variable speed induction motor drives for especially Heating, Ventilation and Air-Condition (HVAC) applications. Optimized efficiency is achieved by adapting the magnetization level in the motor to the load, and the basic purpose is demonstrate how this can be done for low-cost PWM-VSI drives without bringing the robustness of the drive below an acceptable level.Four drives are investigated with respect to energy optimal control: 2.2 kW standard and high-efficiency motor drives, 22 kW and 90 kW standard motor drives. The method has been to make extensive efficiency measurements within the specified operating area with optimized efficiency and with constant air-gap flux, and to establish reliable converter and motor loss models based on those measurements. The loss models have been used to analyze energy optimal control strategies by different steady-state calculations. Several control strategies were implemented and tested on a 2.2 kW scalar drive, both with respect to steady-state efficiency, convergence time in case of changing load, response to a large sudden load disturbance, and energy consumption in a realistic pump system. The dynamic performances were also evaluated in a vector controlled drive for CT applications. Based on these tests, the displacement power factor control and the direct air-gap flux control appeared to be best for small HVAC applications.Energy optimal control of medium-size drives was analyzed separately to investigate the influence of converter losses. A new model-based control principle is proposed which can include converter losses, which does not depend on an analytical solution and which does only requires little computational power. A relation is established which can predict the efficiency improvement by energy optimal control for any standard induction motor drive between 2.2 kW and 90 kW.A simple method to evaluate the robustness against load disturbances was developed and used to compare the robustness of different motor types and sizes. Calculation of the oscillatory behavior of a motor demonstrated that energy optimal control will sometimes improve and sometimes deteriorate the stability.Comparison of small and medium-size induction motor drives with permanent magnet motor drives indicated why, and in which applications, PM motors are especially good. Calculations of economical aspects demonstrated the small difference in savings between the different motor types in a variable speed drive, compared with the constant speed drive.

AB - This thesis deals with energy optimal control of small and medium-size variable speed induction motor drives for especially Heating, Ventilation and Air-Condition (HVAC) applications. Optimized efficiency is achieved by adapting the magnetization level in the motor to the load, and the basic purpose is demonstrate how this can be done for low-cost PWM-VSI drives without bringing the robustness of the drive below an acceptable level.Four drives are investigated with respect to energy optimal control: 2.2 kW standard and high-efficiency motor drives, 22 kW and 90 kW standard motor drives. The method has been to make extensive efficiency measurements within the specified operating area with optimized efficiency and with constant air-gap flux, and to establish reliable converter and motor loss models based on those measurements. The loss models have been used to analyze energy optimal control strategies by different steady-state calculations. Several control strategies were implemented and tested on a 2.2 kW scalar drive, both with respect to steady-state efficiency, convergence time in case of changing load, response to a large sudden load disturbance, and energy consumption in a realistic pump system. The dynamic performances were also evaluated in a vector controlled drive for CT applications. Based on these tests, the displacement power factor control and the direct air-gap flux control appeared to be best for small HVAC applications.Energy optimal control of medium-size drives was analyzed separately to investigate the influence of converter losses. A new model-based control principle is proposed which can include converter losses, which does not depend on an analytical solution and which does only requires little computational power. A relation is established which can predict the efficiency improvement by energy optimal control for any standard induction motor drive between 2.2 kW and 90 kW.A simple method to evaluate the robustness against load disturbances was developed and used to compare the robustness of different motor types and sizes. Calculation of the oscillatory behavior of a motor demonstrated that energy optimal control will sometimes improve and sometimes deteriorate the stability.Comparison of small and medium-size induction motor drives with permanent magnet motor drives indicated why, and in which applications, PM motors are especially good. Calculations of economical aspects demonstrated the small difference in savings between the different motor types in a variable speed drive, compared with the constant speed drive.

M3 - Ph.D. thesis

SN - 87-89179-26-9

BT - Energy Optimal Control of Induction Motor Drives

PB - Institut for Energiteknik, Aalborg Universitet

CY - Aalborg

ER -