Inverter Control for Rotary Machine Overvoltage Suppression
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Solution Overview
Problem
Existing rotary electric machine control devices face challenges in quickly reducing regenerated power when the connection between the DC power source and the inverter is blocked, particularly with reduced capacitance of the smoothing condenser, leading to rapid voltage rises and increased safety concerns.
Innovation Solution
The implementation of an inverter control system that executes zero-torque control and high-loss control by varying the field current to increase the armature current, allowing for a higher torque variation rate and shut-down control when the voltage exceeds a threshold, effectively reducing regenerated power and maintaining safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the capacitance of the smoothing condenser is reduced to achieve space saving and cost reduction, then the device size and cost are reduced, but the voltage rises quickly when the contactor is opened
Solution Approach 1:
The control device predicts the occurrence of overvoltage before it actually happens by monitoring the contactor state and rotational speed. When prediction indicates potential overvoltage, the control proactively reduces regenerated power by adjusting the torque command, preventing the voltage rise before it becomes problematic. This preliminary action allows the system to use smaller smoothing condensers without experiencing rapid voltage rises.
Solution Approach 2:
The control device continuously monitors the actual rotational speed and compares it with the predicted rotational speed to detect deviations. When the actual speed deviates from the predicted speed (indicating regenerative braking conditions), the feedback mechanism triggers power reduction control. This closed-loop feedback enables the system to dynamically adjust regenerated power based on real-time conditions, effectively controlling voltage rise even with reduced condenser capacitance.
2Ease of manufacture
If the capacitance of the smoothing condenser is reduced, then cost is reduced, but the voltage rises quickly when the contactor is opened
Solution Approach 1:
The control device predicts the occurrence of overvoltage before it actually happens by monitoring the contactor state and rotational speed. When prediction indicates potential overvoltage, the control proactively reduces regenerated power by adjusting the torque command, preventing the voltage rise before it becomes problematic. This preliminary action allows the system to use smaller smoothing condensers without experiencing rapid voltage rises.
Solution Approach 2:
The control device continuously monitors the actual rotational speed and compares it with the predicted rotational speed to detect deviations. When the actual speed deviates from the predicted speed (indicating regenerative braking conditions), the feedback mechanism triggers power reduction control. This closed-loop feedback enables the system to dynamically adjust regenerated power based on real-time conditions, effectively controlling voltage rise even with reduced condenser capacitance.
3Speed
If regenerated power is reduced by controlling torque to zero when connection is released, then voltage rise is suppressed, but the reduction is not immediate enough with reduced capacitance
Solution Approach 1:
The control device predicts the occurrence of overvoltage before it actually happens by monitoring the contactor state and rotational speed. When prediction indicates potential overvoltage, the control proactively reduces regenerated power by adjusting the torque command, preventing the voltage rise before it becomes problematic. This preliminary action allows the system to use smaller smoothing condensers without experiencing rapid voltage rises.
Solution Approach 2:
The control device continuously monitors the actual rotational speed and compares it with the predicted rotational speed to detect deviations. When the actual speed deviates from the predicted speed (indicating regenerative braking conditions), the feedback mechanism triggers power reduction control. This closed-loop feedback enables the system to dynamically adjust regenerated power based on real-time conditions, effectively controlling voltage rise even with reduced condenser capacitance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for immediate reduction of regenerated power and voltage suppression, ensuring safety and efficiency even with reduced capacitance, outperforming previous techniques in space-saving and cost-reduction efforts.
Implementation Method 1
an inverter interposed between a DC power source section including a power storage device and an AC rotary electric machine to perform power conversion between DC power from the DC power source section and AC power for the rotary electric machine
Implementation Method 2
the rotary electric machine not only functions as an electric motor that serves as a drive source for the vehicle, but also functions as an electric generator that generates electric power using kinetic energy of the vehicle
Implementation Method 3
executes high-loss control in which the field current is varied so as to increase the armature current while maintaining a torque command provided in the zero-torque control
Data Source
AI summary
An inverter control section controls the inverter by controlling an armature current in a two-axis orthogonal coordinate system that rotates in synchronization with the rotary electric machine, the armature current being a vector obtained by synthesizing a field current and a drive current extending along respective axes of the orthogonal coordinate system. If it is determined that connection between the DC power source section and the inverter is in a blocked state, the inverter control section executes zero-torque control in which the inverter is controlled such that torque regenerated by the rotary electric machine becomes zero, and executes high-loss control in which the field current is varied so as to increase the armature current while maintaining a torque command provided in the zero-torque control.