Motor Drive Inverter Control for Capacitor Ripple Current Reduction
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Solution Overview
Problem
Conventional power converters accelerate the aging deterioration of smoothing capacitors due to large pulsating currents, leading to increased costs and device size, as methods to reduce ripple changes or use high-tolerance capacitors are costly and inefficient.
Innovation Solution
A power converter with a rectifier unit, a capacitor, and an inverter, where a control unit manages pulsation on the capacitor's charging and discharging currents by superimposing power state pulsation on the motor drive pattern, performing load and power pulsation compensation to reduce capacitor stress while maintaining motor control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacitance of the capacitor is increased to reduce ripple changes in capacitor voltage, then the capacitor can better smooth the pulsating current, but the device size increases and cost increases
Solution Approach 1:
The invention changes the operating parameters of the capacitor by controlling the inverter to reduce pulsating current components. The control unit adjusts the switching patterns of the inverter to minimize the ripple current flowing through the capacitor, thereby reducing the stress on the capacitor and allowing the use of smaller capacitance values while maintaining voltage stability.
2Reliability
If a capacitor with high tolerance to deterioration is used to reduce aging deterioration, then the capacitor can withstand larger pulsating currents, but the cost of the capacitor component increases
Solution Approach 1:
The invention modifies the current waveform parameters by controlling the inverter switching to reduce pulsating current. This parameter change reduces the effective stress on the capacitor, allowing the use of standard capacitors with normal tolerance ratings instead of expensive high-tolerance capacitors, thereby reducing component cost while maintaining durability.
3Reliability
If the capacitance of the capacitor is increased to reduce aging deterioration, then the capacitor can better handle pulsating current, but the device size increases
Solution Approach 1:
The invention changes the temporal characteristics of the current flowing through the capacitor by using inverter control to reduce pulsating components. This parameter modification reduces the cumulative stress on the capacitor, extending its lifespan without requiring increased capacitance or device size.
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
The solution effectively reduces capacitor deterioration without increasing device size, achieving efficient motor control and extending capacitor lifespan.
Implementation Method 1
a rectifier unit that rectifies first AC power supplied from a commercial power source
Implementation Method 2
a capacitor connected to an output end of the rectifier unit
Implementation Method 3
an inverter that is connected across the capacitor and generates second AC power for output to a motor
Data Source
AI summary
A power converter includes a capacitor connected to an output end of a rectifier unit that rectifies first AC power, an inverter that is connected across the capacitor and generates second AC power for output to a motor, and a control unit that controls the operation of the inverter such that pulsation according to the power state of the capacitor is superimposed on a drive pattern of the motor. The control unit performs load pulsation compensation control to reduce the vibration of the motor and power pulsation compensation control to reduce the charging and discharging current of the capacitor while preferentially performing constant current load control to control the rotational speed of the motor, and generates a torque current command for the load pulsation compensation control such that a torque current command allocatable to the power pulsation compensation control remains.