Motor Emulator Circuit for High-Frequency Current Emulation
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Solution Overview
Problem
Existing motor emulators face limitations in emulating high-frequency current due to low switching frequency and inductance issues, leading to current pulsation and voltage shortages, which restrict their ability to accurately mimic medium-speed and high-speed motor operations.
Innovation Solution
A motor emulator design featuring a voltage following inverter and an output current control unit that uses SiC MOSFETs and independent DC voltage sources to control switching frequencies up to 100 kHz, reducing current pulsation and enabling precise emulation across a wider voltage modulation area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the inductance of the motor emulator is increased to match the target motor (0.9 pu to 1.1 pu), then the high-frequency current emulation performance is improved, but the DC terminal voltage must be further increased through the boosting circuit, which is limited by the voltage rating of the devices
Solution Approach 1:
The patent changes the inductance parameter of the motor emulator to match the target motor's inductance (0.9 pu to 1.1 pu), which improves high-frequency current emulation performance. This parameter adjustment is achieved through the use of SiC MOSFETs that enable high-speed switching, allowing the system to maintain stable operation with the matched inductance without requiring excessive DC terminal voltage boosting.
2Strength
If the inductance of the motor emulator is decreased (0.1 pu to 0.3 pu) to solve the voltage shortage problem, then the DC terminal voltage requirement is reduced, but the current pulsation caused by digital control delay increases significantly
Solution Approach 1:
The patent replaces traditional mechanical or conventional electronic switching systems with SiC MOSFET-based switching technology. This substitution enables high-speed switching operation that significantly reduces the control delay, thereby minimizing current pulsation even when the inductance is decreased to 0.1 pu to 0.3 pu. The SiC MOSFET's fast switching capability compensates for the reduced inductance effect.
Solution Approach 2:
The patent introduces dynamic high-speed switching control using SiC MOSFETs that can adapt to the reduced inductance conditions. The switching frequency is increased to 100 kHz or above, which dynamically adjusts the system response to compensate for the lower inductance value, thereby maintaining stable current output without excessive pulsation.
3Productivity
If the switching frequency is increased to 100 kHz or above using SiC devices, then the current emulation band is extended to cover switching frequency band (5 to 10 kHz), but the heat dissipation conditions become more challenging
Solution Approach 1:
The patent employs SiC (Silicon Carbide) semiconductor devices, which are composite materials with superior thermal and electrical properties compared to conventional silicon devices. SiC MOSFETs have higher thermal conductivity and higher breakdown voltage, enabling them to operate at switching frequencies of 100 kHz or above while managing heat dissipation more effectively. This material choice extends the current emulation bandwidth to cover the switching frequency band (5 to 10 kHz).
Data Source
AI summary
Embodiments relate to a motor simulator for an inverter under test (IUT), the motor simulator comprising: a voltage follower inverter for at least partially cancelling an output voltage of the IUT; and an output current control unit for controlling an output current of the IUT on the basis of an estimated current of a simulation target motor.