Inverter Control Frequency Range Dynamics
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Solution Overview
Problem
Existing motor driving systems using pulse width modulation (PWM) with fixed frequencies suffer from controllability issues and electromagnetic noise due to harmonic components, and switching to random PWM methods can improve noise reduction but deteriorate current controllability and introduce abrupt frequency changes.
Innovation Solution
An apparatus and method for controlling an inverter that includes a frequency determining processor to set a gradually increasing or decreasing frequency change range for the PWM frequency, allowing smooth transitions between PWM methods and reducing noise while maintaining controllability, using a combination of current controllers, voltage modulators, and frequency determining processors to manage switching frequencies based on motor driving information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If random pulse width modulation method is applied to reduce switching noise, then electromagnetic noise is reduced, but current controllability deteriorates due to abrupt frequency changes
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable and variable rather than fixed. The frequency determining processor dynamically changes the switching frequency within a predetermined range based on operating conditions, allowing the system to adapt between fixed frequency (for controllability) and variable frequency (for noise reduction), thus resolving the contradiction between noise reduction and controllability
Solution Approach 2:
The patent changes the parameter of switching frequency from a fixed value to a variable parameter that can be adjusted within a predetermined range. By modifying the frequency parameter dynamically based on operational requirements, the system achieves both noise reduction benefits and maintained controllability, resolving the technical contradiction
2Ease of operation
If pulse width modulation frequency is fixed to simplify control, then controllability is improved, but electromagnetic noise and vibration increase due to strong harmonic components
Solution Approach 1:
The system uses a frequency determining processor that dynamically adjusts the switching frequency within a predetermined range based on operating conditions. This dynamic frequency adjustment allows the system to maintain simplified control structures while reducing electromagnetic noise by avoiding fixed frequency harmonics
Solution Approach 2:
The patent implements periodic variation of the switching frequency around a base frequency. This periodic action disperses the harmonic energy across multiple frequencies, reducing the intensity of individual harmonic components and thereby reducing electromagnetic noise while maintaining control effectiveness
3Object-affected harmful factors
If switching frequency is randomly changed to disperse frequency band, then noise is suppressed, but current controllability deteriorates due to rapid frequency changes
Solution Approach 1:
The frequency determining processor dynamically adjusts the switching frequency within a predetermined range based on operating conditions. This controlled dynamic adjustment allows noise suppression through frequency variation while maintaining current controllability by preventing abrupt or excessive frequency changes
Solution Approach 2:
The patent changes the switching frequency parameter within a controlled predetermined range rather than random changes. This controlled parameter variation achieves noise suppression through frequency dispersion while maintaining controllability by limiting the extent and rate of frequency changes
Data Source
AI summary
An apparatus for controlling an inverter for driving a motor includes a processor which includes: a current processor for generating a voltage command for causing a current detection value obtained by measuring a current supplied from the inverter to the motor to follow a current command for driving the motor; a voltage modulator for generating a pulse width modulation signal for controlling on and off states of switching elements in the inverter with a predetermined switching frequency based on the voltage command; and a frequency determining processor for setting a frequency change range within which the switching frequency will be randomly changed and randomly determining the switching frequency within the frequency change range when a random pulse width modulation method is applied to control of the inverter.