Power Conversion Apparatus Voltage Distortion Correction
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Solution Overview
Problem
Existing power conversion systems fail to effectively reduce power-supply harmonics caused by distortion in motor voltage, which varies with operational states like rotational speed or load torque, leading to current distortion and torque ripple.
Innovation Solution
A power conversion apparatus equipped with switching devices, a controller, a capacitor for ripple smoothing, a current controller, and a voltage distortion corrector that detects harmonic components in the input power and superimposes compensation values to reduce harmonic distortion, using Fourier transforms and hill climbing methods to adjust compensation voltages based on operational states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If compensation voltage from a fixed table is added to voltage reference, then torque ripple is reduced, but power-supply harmonics are not reduced because the compensation voltage contains errors depending on operational state
Solution Approach 1:
The patent transitions from a static compensation voltage table to a dynamic compensation method where the compensation voltage is calculated in real-time based on the operational state (rotational speed, load torque). The voltage distortion corrector dynamically adjusts the compensation voltage values according to the actual operating conditions, ensuring accuracy across all operational states rather than relying on pre-stored values that may not match the current state.
Solution Approach 2:
The patent implements a feedback mechanism where the voltage distortion corrector continuously monitors the operational state and adjusts the compensation voltage accordingly. By using the actual rotational speed and load torque information, the system creates a closed-loop control that adapts the compensation voltage to match the current operational conditions, eliminating the errors present in fixed-table approaches.
2Reliability
If harmonic component of motor current is controlled extra to reduce current distortion, then power-supply harmonic regulations are satisfied, but device complexity increases
Solution Approach 1:
The voltage distortion corrector performs multiple functions simultaneously: it detects voltage distortion, calculates compensation voltages, and outputs corrected voltage references. By integrating these functions into a single control block within the existing controller, the patent avoids the need for separate harmonic control circuits or additional control systems, thereby satisfying power-supply harmonic regulations without significantly increasing device complexity.
Solution Approach 2:
The patent combines the voltage distortion correction function with the existing current control system. The compensation voltage calculation is integrated into the voltage reference generation process, merging the harmonic mitigation function with the existing control architecture rather than adding a separate, independent control system.
3Reliability
If compensation voltage is adjusted dynamically based on operational state, then power-supply harmonics are reduced, but control complexity increases
Solution Approach 1:
The voltage distortion corrector uses the operational state information (rotational speed, load torque) that is already available from the motor control system to automatically calculate and adjust the compensation voltage. The system serves itself by utilizing existing sensor data and control variables, eliminating the need for additional sensors or external adjustment mechanisms, thereby reducing power-supply harmonics without proportionally increasing control complexity.
Data Source
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AI summary
A power conversion apparatus is equipped with switching devices (Su, Sv, Sw, Sx, Sy, and Sz) to perform power conversion of input AC power supplied from an AC power supply (6) to output AC power having a predetermined voltage and a predetermined frequency, and to supply the power to a motor (7) connected thereto. The apparatus includes a controller (5) controlling switching of the switching devices (Su, Sv, Sw, Sx, Sy, and Sz), a capacitor (3a) smoothing a ripple generated by the switching of the switching devices (Su, Sv, Sw, Sx, Sy, and Sz), a current controller (53) controlling a current flowing to the motor (7), and a voltage distortion corrector (54) detecting a harmonic component caused by distortion in motor input power, and superimposing compensation values (vd_h and vq_h) on an output of the current controller (53) in accordance with a value of the harmonic component.