Inverter Zero Torque Control for Vehicle Battery Charging Protection
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Solution Overview
Problem
Existing vehicle control systems face challenges in preventing battery charging during regenerative power generation while avoiding inverter overheating, particularly when the battery is prohibited from charging and the rotating electrical machine is driven by motive power from the driving wheel.
Innovation Solution
Implementing a control method that performs zero torque control on the inverter to prevent regenerative torque generation, and switching to three-phase ON control or gate shutoff based on power consumption and rotation speed conditions to manage regenerative power and prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three-phase ON control is performed to prevent battery charging by regenerative current, then the battery is protected from being charged when prohibited, but the inverter may become overheated due to Joule heat from circulating regenerative current
Solution Approach 1:
The control device changes the operating parameters of the rotating electrical machine by performing zero torque control, adjusting the torque command value to zero. This parameter change stops regenerative current generation at the source, preventing both battery charging and inverter overheating simultaneously
Solution Approach 2:
The control device extracts and eliminates the harmful regenerative current at its source by implementing zero torque control. Instead of allowing current to circulate through the inverter (causing overheating) or charge the battery (when prohibited), the control stops torque generation entirely, removing the problematic current flow
2Temperature
If zero torque control is performed to stop regenerative current flow, then inverter overheating is prevented, but regenerative power cannot be utilized when battery charging is allowed
Solution Approach 1:
The control device dynamically adjusts the torque command value based on real-time operating conditions. When battery charging is prohibited, zero torque control is applied; when charging is allowed, normal regenerative braking is enabled. This dynamic adaptation optimizes both thermal management and energy recovery
Solution Approach 2:
The control device uses feedback from the charging prohibition status to determine the appropriate control mode. By monitoring whether battery charging is allowed or prohibited, the system automatically selects between zero torque control and normal regenerative braking, ensuring optimal performance under different conditions
3Loss of energy
If regenerative braking is performed to recover energy, then energy efficiency is improved, but the battery may be damaged or overloaded when charging is prohibited
Solution Approach 1:
The control device performs preliminary anti-action by implementing zero torque control before regenerative current can flow to the battery when charging is prohibited. By preemptively stopping torque generation, the system prevents potential battery damage or overload before it can occur
Solution Approach 2:
The control device extracts and eliminates the harmful regenerative current at its source through zero torque control when battery charging is prohibited, preventing potential battery damage. When charging is allowed, the same control mechanism enables safe energy recovery, thus removing the harmful aspect while preserving the beneficial aspect
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
Effectively prevents battery charging by regenerative power and reduces the risk of inverter overheating by managing regenerative current flow, ensuring safe operation even when the battery is prohibited from charging.
Implementation Method 1
an inverter configured to convert DC power supplied from the power storage device to AC power and supply the AC power to the rotating electrical machine
Implementation Method 2
when the power storage device is prohibited from being charged while the rotating electrical machine is being driven to rotate by the motive power from the driving wheel
Implementation Method 3
it is concerned that the inverter may become overheated due to Joule heat
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The vehicle includes an AC motor generator (MG) connected to a driving wheel, a battery, an inverter configured to convert DC power supplied from the battery to AC power and supply the AC power to the MG, and a vehicle ECU configured to control the inverter. The vehicle ECU performs a zero torque control to drive the inverter so that the output torque from the MG is zero when the battery is prohibited from being charged while the MG is being driven to rotate by the motive power from the driving wheel.