Synchronous Motor Position Error Correction at Standstill
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Solution Overview
Problem
Synchronous motor angular position estimation in vector control is challenged by differential cross-coupling errors between d- and q-axes, making accurate position estimation difficult without position sensors and rotor rotation.
Innovation Solution
A method using high-frequency voltage injection and pulsating torque signals to estimate angular position error by processing d- and q-axis currents, compensating for cross-coupling effects through a lookup table of error values at various torque operating points, enabling accurate sensorless vector control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If voltage injection is used for angular position estimation in synchronous motors, then position estimation can be achieved without position sensors, but differential cross-coupling errors between d- and q-axes introduce significant estimation errors
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing angular position error values in a lookup table across multiple torque operating points before actual motor operation. During runtime, the system simply retrieves the appropriate error value based on current torque conditions and applies compensation, avoiding real-time complex calculations and achieving both sensorless operation and high precision position estimation
Solution Approach 2:
The patent changes the operating parameter by injecting high-frequency voltage signals at different torque operating points to excite the motor and measure the resulting angular position errors. By varying the torque parameter and measuring corresponding position errors, the system builds a comprehensive lookup table that enables accurate compensation across the entire operating range
2Speed
If high-frequency voltage injection is applied to estimate angular position, then position information can be obtained at standstill, but cross-coupling effects between d- and q-axes create measurement errors
Solution Approach 1:
The patent implements feedback by measuring the actual angular position error that occurs during high-frequency voltage injection at each torque operating point, storing this measured error in the lookup table, and then using this stored error feedback to compensate for cross-coupling effects during normal operation. This closed-loop approach ensures high precision position estimation even at standstill
Solution Approach 2:
The system performs preliminary measurements and error characterization at various torque operating points before actual motor control begins. This preliminary action of building the lookup table with pre-measured error values enables accurate position estimation at standstill without requiring the motor to rotate, while compensating for cross-coupling effects
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise angular position estimation and correction of errors in synchronous motor control, improving the accuracy of vector control without the need for position sensors or rotor rotation, effectively addressing the cross-coupling issues in existing methods.
Implementation Method 1
A method using high-frequency voltage injection and pulsating torque signals to estimate angular position error by processing d- and q-axis currents
Implementation Method 2
In synchronous electric motors, the rotation of the motor shaft (i.e., of the rotor) is synchronized with the frequency of the supply current at steady state
Data Source
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AI summary
According to an aspect, there is provided an apparatus for performing angular position error estimation. The apparatus operates (601) a synchronous motor (111) according to a pre-defined pulsating torque signal using a sensorless vector control method with high-frequency voltage injection. The pre-defined pulsating torque signal has a zero mean and corresponds to a torque operating point. The apparatus measures (602) a first value of an estimated angular position at a first time instance corresponding substantially to an end point of the pre-defined pulsating torque signal and second values of the estimated angular position and an estimated angular speed at a second time instance occurring after the first time instance. Based on the measured values, the apparatus estimates (603) an error in the estimated angular position and stores (604) the error to a lookup table. After performing said steps for one or more pre-defined pulsating torque signals, the apparatus operates (607) the synchronous motor (111) using the lookup table for angular position error correction.