Inverter Control Device Torque Reduction for Overcurrent Suppression
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Solution Overview
Problem
Existing inverter control devices face challenges in suppressing overcurrents during abnormalities in rotating electrical machines or inverters, leading to potential demagnetization and increased load on inverter elements.
Innovation Solution
The inverter control device employs an electronic control unit that controls switching elements in an orthogonal coordinate system, performing torque reduction control and active short-circuit control to manage armature and field currents, reducing drive current and regulating field current to approach a specific operating point, thereby suppressing overcurrents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active short-circuit control is performed at all times when an abnormality has occurred during rotation of the rotating electrical machine at a high speed, then the control is simple and immediate, but all current generated by the rotating electrical machine circulates through the inverter and coils, causing overcurrent
Solution Approach 1:
The control device performs torque reduction control before switching to active short-circuit control. By reducing the torque instruction value when an abnormality is detected, the drive current is reduced in advance, which prevents excessive current circulation when active short-circuit control is subsequently activated, thereby avoiding overcurrent damage to the inverter and coils
Solution Approach 2:
The control device dynamically adjusts the torque instruction value based on the operational state and abnormality conditions. Instead of maintaining a fixed torque value, the system modifies the torque instruction to reduce drive current during abnormal operations, enabling adaptive current management that prevents overcurrent while handling abnormalities
2Reliability
If the switching elements are controlled to on state during active short-circuit control, then the abnormality protection is achieved, but transient vibration occurs in currents flowing through the inverter and rotating electrical machine
Solution Approach 1:
The control device reduces torque and adjusts field current in advance before activating active short-circuit control. This preliminary adjustment of current parameters stabilizes the electrical state, reducing the magnitude of transient vibrations and current fluctuations that would otherwise occur during the switching transition to short-circuit mode
Solution Approach 2:
The control device changes the field current parameter during the transition to active short-circuit control. By adjusting the field current to an appropriate value before and during the switching process, the system modifies the electrical characteristics to minimize transient vibrations and maintain current stability while preserving the protective function
Data Source
AI summary
An inverter control device that controls an inverter as a control target, the inverter being connected to a direct-current power supply and connected to an alternating-current rotating electrical machine so as to convert power between direct current and alternating current of a plurality of phases, and the inverter having an arm for each alternating-current phase, the arm including a series circuit of an upper-stage switching element and a lower-stage switching element, the inverter control device including an electronic control unit.