Rotating Electric Machine Control Device for Stable Power Supply Current
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Solution Overview
Problem
Conventional rotating electric machine control devices face issues with unstable power supply current limitation, leading to insufficient motor output or excessive current flow due to variations in motor characteristics and environmental temperature.
Innovation Solution
A rotating electric machine control device that includes a power supply voltage detection section, motor current detection section, and a control portion with specific modules for voltage command calculation, inverter power estimation, power supply current estimation, target power supply current determination, limit gain determination, and current limitation, which determines the limit gain based on detected and estimated values to stabilize power supply current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor voltage limit command value is calculated using a torque constant and motor resistance, then the power supply current can be limited to prevent heat generation and switching element breakdown, but the limitation becomes unstable due to individual differences and temperature variations
Solution Approach 1:
The control device calculates the actual power supply current based on detected motor current and voltage, compares it with the target power supply current, and adjusts the limit gain accordingly. This closed-loop feedback mechanism ensures stable power supply current limitation despite variations in motor characteristics and temperature, resolving the contradiction between reliability and measurement precision.
2Reliability
If the power supply current is excessively limited to ensure safety, then heat generation and switching element breakdown are prevented, but the motor output becomes insufficient
Solution Approach 1:
The limit gain is dynamically adjusted based on the ratio of target power supply current to actual power supply current. When the actual current is lower than the target, the limit gain increases to allow higher motor output. When the actual current approaches the target, the limit gain decreases to prevent excessive current. This dynamic adjustment resolves the contradiction between protection and power output.
3Power
If the power supply current limitation is relaxed to maintain motor output, then sufficient motor power is achieved, but excess current may flow causing heat generation and potential damage
Solution Approach 1:
The continuous monitoring and comparison of actual versus target power supply current enables real-time feedback control. The limit gain is adjusted to maintain the actual current at or near the target value, ensuring sufficient motor output while preventing harmful excess current flow and heat generation.
Data Source
AI summary
In a rotating electric machine control device, a voltage command value calculation section calculates a voltage command value based on a current command value and a motor current. An inverter power estimation section estimates an inverter power based on the motor current. A power supply current estimation section estimates a power supply current based on the inverter power and a power supply voltage. A limit gain determination section determines a limit gain based on the power supply current and a target power supply current. A limited voltage command value calculation section calculates a limited voltage command value based on the voltage command value and the limit gain. A current limitation section is capable of limiting the power supply current by outputting a command value corresponding to the limited voltage command value to an inverter portion.