Synchronous Motor Voltage Phase Control for Response Delay Compensation
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Solution Overview
Problem
In synchronous motor control systems, the existing methods for detecting rotor position in a sensorless manner fail to account for response delays during transient states, leading to oscillations and loss of synchronism due to the lack of consideration of motor characteristics in setting the phase instruction values for applied voltages.
Innovation Solution
The proposed solution involves updating the applied voltage electrical angle instruction values by correcting for the response time constant of the synchronous motor and accounting for magnetic flux variations, ensuring stable operation by maintaining suitable response speed and filtering out response delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the voltage phase of the applied voltage is changed in the synchronous motor, then the current phase changes according to motor characteristic formula, but a response delay occurs according to UR time constant (L: inductance, R: coil resistance)
Solution Approach 1:
The patent applies preliminary action by calculating and applying a phase lead amount in advance to compensate for the anticipated response delay. The control device predicts the delay that will occur due to the UR time constant and proactively adjusts the voltage phase instruction value before the actual response delay manifests, ensuring the current phase reaches the target phase accurately without oscillation or loss of synchronism.
Solution Approach 2:
The patent changes the parameter of voltage phase instruction value dynamically based on the UR time constant. By calculating the phase lead amount as a function of the UR time constant and adjusting the voltage phase instruction accordingly, the system optimizes the balance between response speed and stability, preventing oscillation while maintaining accurate rotor position detection during transient states.
2Device complexity
If the position detecting operation is continued while ignoring the response delay, then the control system remains simple, but the actual rotation of the rotor cannot catch up with the phase instruction value of the applied voltage, leading to oscillation and loss of synchronism
Solution Approach 1:
The patent modifies the voltage phase instruction value parameter by adding a calculated phase lead amount that accounts for the UR time constant. This parameter adjustment is performed through mathematical calculation based on motor characteristics, maintaining relative system simplicity while significantly improving reliability during transient operations.
3Ease of operation
If a predetermined phase difference is added to the calculated current phase to set the voltage phase, then the phase instruction value can be determined, but the response delay due to motor characteristics is not compensated, reducing stability during transient states
Solution Approach 1:
The patent enhances the voltage phase setting by dynamically adjusting the phase difference parameter based on the UR time constant. Instead of using a fixed predetermined phase difference, the system calculates an optimized phase lead amount that compensates for response delay, maintaining ease of operation through automated calculation while improving stability during transient states.
Solution Approach 2:
The system performs preliminary calculation of the phase lead amount based on the UR time constant and motor characteristics before applying the voltage phase instruction. This advance preparation ensures that the phase instruction value is optimally set to compensate for anticipated response delays, improving transient stability without complicating the operational process.
Data Source
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Figure 2(A)~2(C)
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AI summary
Proposed is a control technique for a synchronous motor that can set an instruction value of an applied voltage in consideration of a response delay of a current. An applied-voltage electrical angle setting method according to the proposal includes detecting an applied voltage and a current of the synchronous motor M, calculating a current peak value Ip based on the detected values while calculating a present applied voltage phase α, calculating a target current phase βtarg based on the current peak value Ip followed by calculating a target applied voltage phase αtarg corresponding to the target current phase in a target value setting unit 20, and calculating a new applied voltage electrical angle instruction value θvtarg, based on a change angle Δθv obtained by correcting a difference between the present applied voltage phase α and the target applied voltage phase αtarg by a response time constant L/R of the synchronous motor, a rotational speed ω calculated based on the applied voltage and the current, and the previous applied voltage electrical angle instruction value θvtarg, in a voltage electrical angle instruction value setting unit 10.