Motor Inverter Square-Wave Modulation for Overmodulation Current Control
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Solution Overview
Problem
Existing power conversion devices face an issue where the current flowing through a motor increases when the voltage command exceeds the amplitude of the carrier wave, leading to a lower fundamental wave component of the output voltage.
Innovation Solution
A power conversion device that includes a modulated wave generator producing a square wave based on the voltage command norm and a control signal generator to control a switching circuit, allowing for effective voltage conversion and current management by comparing the modulated wave with a carrier wave.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the voltage command is increased to increase the fundamental wave component of the output voltage, then the output voltage performance is improved, but the motor current increases excessively
Solution Approach 1:
The patent changes the waveform parameter of the modulated wave from a conventional sinusoidal wave to a square wave. This parameter change allows the system to maintain the fundamental wave component of the output voltage while suppressing excessive motor current, as the square wave modulation enables more efficient voltage utilization without causing current overload
Solution Approach 2:
The patent dynamically adjusts the modulation strategy by using square wave generation based on voltage command norm. The system adaptively controls the switching circuit operation to maintain optimal voltage output while preventing current excessive increase, achieving dynamic balance between voltage output and current consumption
2Power
If the voltage command exceeds the carrier wave amplitude, then the voltage utilization rate is improved, but the fundamental wave component of the output voltage becomes lower than the voltage command
Solution Approach 1:
The patent changes the modulation waveform parameter to a square wave, which enables the system to achieve higher voltage utilization rate while maintaining output voltage accuracy. The square wave modulation allows the fundamental wave component to closely match the voltage command even when the voltage command exceeds the carrier wave amplitude, unlike conventional sinusoidal modulation
3Device complexity
If a simple control circuit is used to increase the fundamental wave component, then the device complexity is reduced, but the current control precision deteriorates
Solution Approach 1:
The patent uses a simple square wave generation approach instead of complex sinusoidal modulation circuits. This parameter change in waveform generation maintains device simplicity while achieving precise motor current control, as the square wave modulation inherently provides better voltage utilization and current suppression characteristics
Solution Approach 2:
The patent replaces complex analog control circuits with a simplified digital control approach using square wave generation. This substitution maintains or improves current control precision while significantly reducing device complexity, as the square wave can be generated and controlled more efficiently through digital logic
Data Source
AI summary
An object of the present invention is to provide a power conversion device capable of suppressing an increase in a current flowing through a motor even if a voltage command exceeds the amplitude of a carrier wave. In order to achieve the above object, the power conversion device controls the driving of a motor by converting a DC voltage into a voltage based on a voltage command by an operation of a switching circuit and includes: a modulated wave generator that generates a first modulated wave from the voltage command; and a control signal generator that generates a control signal for controlling the operation of the switching circuit from the first modulated wave and a carrier wave. The modulated wave generator generates a square wave based on a voltage command norm as the first modulated wave.