Inverter Protection Control for DC Disconnection Overvoltage
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Solution Overview
Problem
Existing electric-rotating-machine control systems face a trade-off between rapid detection of inverter circuit disconnection from the DC power source to prevent excessive voltages and erroneous detection, leading to potential component damage or unnecessary shutdowns, which complicates downsizing and cost reduction.
Innovation Solution
An electric-rotating-machine control apparatus with a voltage sensor, temperature sensor, and control unit that dynamically adjusts the determination voltage based on temperature to perform protective control, including 6-switch opening or phase short-circuiting, to prevent excessive voltages without upsizing components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the determination voltage is set low to enable rapid detection of disconnection, then the response speed improves, but erroneous detection increases due to voltage ripple during normal operation
Solution Approach 1:
The determination voltage is made dynamic by adjusting it according to the regenerative braking torque. During normal regenerative braking operation, the determination voltage is set higher to avoid erroneous detection from voltage ripple. When disconnection is detected or regenerative torque exceeds a threshold, the determination voltage is lowered to enable rapid detection. This dynamic adjustment resolves the contradiction between rapid detection and erroneous detection prevention.
Solution Approach 2:
The patent changes the determination voltage parameter based on operating conditions. By monitoring regenerative braking torque and comparing it against a threshold, the system adjusts the determination voltage level accordingly. This parameter change allows the system to maintain high detection sensitivity only when necessary, while avoiding false positives during normal operation.
2Reliability
If the determination voltage is set high to prevent erroneous shutdown, then the reliability improves, but the detection speed decreases causing delay in protective operation
Solution Approach 1:
The system dynamically adjusts the determination voltage based on regenerative braking torque levels. When regenerative torque exceeds a predetermined threshold or disconnection is detected, the determination voltage is lowered to enable rapid detection within a predetermined time. This dynamic behavior prevents detection delay during critical conditions while maintaining high voltage thresholds during normal operation to prevent erroneous shutdowns.
Solution Approach 2:
The system performs preliminary assessment of regenerative braking torque before applying the determination voltage for disconnection detection. By pre-evaluating the operating condition and setting appropriate voltage thresholds in advance, the system prepares for rapid detection when needed without causing delay during actual disconnection events.
3Strength
If component size is increased to withstand higher voltages, then the withstanding voltage capability improves, but the device complexity and cost increase
Solution Approach 1:
The system performs preliminary detection of disconnection conditions by monitoring voltage and regenerative braking torque before excessive voltages can damage components. By detecting disconnection early and initiating protective control actions, the system prevents voltage levels from reaching dangerous thresholds that would require oversized components for protection.
Solution Approach 2:
The system rushes through the detection and protective control process within a predetermined time frame to prevent excessive voltage buildup. By quickly detecting disconnection and immediately executing protective control (such as switching control to prevent capacitor charging), the system avoids the need for components designed to withstand higher voltages, thereby reducing device complexity and cost.
Data Source
AI summary
The electric-power conversion apparatus includes an electric-power conversion circuit having two or more legs in each of which there are provided a positive-polarity switching device, a negative-polarity switching device, and an external connection point at which the positive-polarity switching device and the negative-polarity switching device are connected in series with each other and that is connected with an electric rotating machine, a capacitor connected with a positive electrode and a negative electrode, a voltage sensor for detecting a voltage between the positive electrode and the negative electrode, a temperature sensor for detecting a temperature of the electric-power conversion circuit, and a control unit that on/off-controls the switching devices in the electric-power conversion circuit and that performs protective control in the case where a voltage detected by the voltage sensor is larger than a determination voltage calculated based on a temperature detected by the temperature sensor.