Converter Control Device Phase Error Compensation
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Solution Overview
Problem
Current control methods for three-phase PWM converters face challenges in accurately adjusting control gains due to errors in the conducting phase, which lead to inaccuracies in calculated inductance and subsequent control gain adjustments.
Innovation Solution
A control device for converters that includes a phase detector, phase corrector, current coordinate transformer, current controller, voltage coordinate transformer, and estimator. This device corrects phase detection errors using voltage commands and impedance, estimates inductance based on voltage commands and currents, and updates current control gains accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase detection is used to calculate inductance, then inductance can be identified for control gain adjustment, but conducting phase errors create inaccuracies in both voltage measurement and inductance calculation
Solution Approach 1:
The patent implements feedback by using the calculated inductance value to adjust the control gain in the current control loop. The system continuously monitors the actual current, compares it with the command current, and uses the inductance information to optimize the control gain dynamically, thereby improving current control accuracy despite phase detection errors
Solution Approach 2:
The patent changes the control gain parameter based on the identified inductance value. By adjusting the control gain according to the actual inductance (which accounts for magnetic saturation effects), the system optimizes current control performance. The control gain is modified as a function of the inductance parameter to compensate for nonlinearities in the motor characteristics
2Stability of the object's composition
If control gain is adjusted based on identified inductance, then current control stability improves, but phase detection errors prevent appropriate control gain adjustment
Solution Approach 1:
The patent converts the harmful effect of phase detection errors into a beneficial outcome by using the available (though potentially erroneous) phase information to calculate inductance, and then using that inductance value to optimize the control gain. The system acknowledges the phase detection limitation but transforms it into an opportunity for adaptive control gain adjustment that improves current control stability
Solution Approach 2:
The patent implements dynamic adjustment of the control gain based on real-time inductance identification. Rather than using a fixed control gain, the system continuously updates the gain parameter according to the identified inductance value, which varies with operating conditions such as magnetic saturation. This dynamic adaptation maintains current control stability across different operating points
Data Source
AI summary
In a control device, a phase corrector corrects an error in a phase of an AC power supply detected by a phase detector. A current coordinate transformer transforms detected values of three-phase currents of a converter into dq-axes currents using the corrected phase. A current controller calculates a voltage command so that current commands of the converter and the dq-axes currents match each other. A voltage coordinate transformer transforms the voltage command into three-phase voltage commands using the corrected phase. An estimator estimates an inductance of a reactor using the voltage commands and the dq-axes currents. The phase corrector corrects a phase detection error using the voltage commands, the dq-axes currents, and an impedance of the reactor. The current controller updates a current control gain using the inductance estimated by the estimator.