Sensorless Control of Switched Reluctance Machines for Low Speeds and Standstill

Abstract

A method for determining rotor position of a switched reluctance (SR) machine having a rotor and a stator is provided. The method may include injecting a test pulse into one or more idle phases of the SR machine, determining a decoupled flux value based at least partially on a total flux value corresponding to the test pulse and a mutual flux value, and determining the rotor position based at least partially on the decoupled flux value.

What is claimed is: 
     
         1 . A method for determining rotor position of a switched reluctance (SR) machine having a rotor and a stator, comprising:
 injecting a test pulse into one or more idle phases of the SR machine;   determining a decoupled flux value based at least partially on a total flux value corresponding to the test pulse and a mutual flux value; and   determining the rotor position based at least partially on the decoupled flux value.   
     
     
         2 . The method of  claim 1 , wherein the test pulse is configured to have a substantially constant current height. 
     
     
         3 . The method of  claim 1 , wherein the test pulse is injected based at least partially on a measured phase current and rotor position feedback. 
     
     
         4 . The method of  claim 1 , wherein the total flux value is determined based at least partially on a voltage integration of the test pulse. 
     
     
         5 . The method of  claim 1 , wherein the mutual flux value is determined based on one or more predefined relationships between mutual flux values, measured phase current values, and rotor position feedback values. 
     
     
         6 . The method of  claim 1 , wherein the decoupled flux value is determined based at least partially on a difference between the total flux value and the mutual flux value. 
     
     
         7 . The method of  claim 1 , wherein the rotor position is determined based on one or more predefined relationships between decoupled flux values, measured phase current values, and rotor position values. 
     
     
         8 . The method of  claim 1 , wherein the rotor position is used to further derive a speed and a direction of the rotor relative to the stator. 
     
     
         9 . A control system for a switched reluctance (SR) machine having a rotor and a stator, comprising:
 a converter circuit in electrical communication between the stator and a common bus; and   a controller in electrical communication with at least the converter circuit, the controller being configured to inject a test pulse into one or more idle phases of the SR machine, determine a decoupled flux value based at least partially on a total flux value corresponding to the test pulse and a mutual flux value, and determine the rotor position based at least partially on the decoupled flux value.   
     
     
         10 . The control system of  claim 9 , wherein the controller is configured to inject the test pulse to have a substantially constant current height. 
     
     
         11 . The control system of  claim 9 , wherein the controller is configured to measure phase current and monitor rotor position feedback. 
     
     
         12 . The control system of  claim 9 , wherein the controller is configured to determine the total flux value by integrating a voltage of the injected test pulse. 
     
     
         13 . The control system of  claim 9 , wherein the controller is configured to determine the mutual flux value by referring to one or more preprogrammed maps defining relationships between mutual flux values, measured phase current values, and rotor position feedback values. 
     
     
         14 . The control system of  claim 9 , wherein the controller is configured to determine the decoupled flux value by computing a difference between the total flux value and the mutual flux value. 
     
     
         15 . The control system of  claim 9 , wherein the controller is configured to determine the rotor position by referring to one or more preprogrammed maps defining relationships between decoupled flux values, measured phase current values, and rotor position values. 
     
     
         16 . The control system of  claim 9 , wherein the controller is further configured derive a speed and a direction of the rotor relative to the stator based on the rotor position. 
     
     
         17 . An electric drive, comprising:
 a switched reluctance (SR) machine having a stator and a rotor rotatably disposed relative to the stator;   a converter circuit configured to electrically communicate with the stator and a common bus; and   a controller in electrical communication with at least the converter circuit, the controller being configured to inject a test pulse into one or more idle phases of the SR machine, determine a decoupled flux value based at least partially on a total flux value corresponding to the test pulse and a mutual flux value, and determine the rotor position based at least partially on the decoupled flux value.   
     
     
         18 . The electric drive of  claim 17 , wherein the controller is configured to generate the test pulse to have a substantially constant current height, and inject the test pulse based at least partially on a measured phase current and rotor position feedback. 
     
     
         19 . The electric drive of  claim 17 , wherein the controller is configured to determine the total flux value by integrating a voltage of the injected test pulse, determine the mutual flux value by referring to one or more preprogrammed maps defining relationships between mutual flux values, measured phase current values, and rotor position feedback values, and determine the decoupled flux value by computing a difference between the total flux value and the mutual flux value. 
     
     
         20 . The electric drive of  claim 17 , wherein the controller is configured to determine the rotor position by referring to one or more preprogrammed maps defining relationships between decoupled flux values, measured phase current values, and rotor position values.