Drive Unit Capacitor Discharge Control via Duty Ratio Optimization
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Solution Overview
Problem
Existing drive units face inefficiencies in discharging residual charges from capacitors, leading to prolonged time and increased energy loss due to suboptimal control of step-up and step-down operations in the step up-down converter.
Innovation Solution
The implementation of an electronic control unit that sets a target duty ratio to maximize total losses in the step up-down converter and DC-DC converter, thereby accelerating the discharge of capacitors by optimizing the converter's operation when the relay is turned off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the step up-down converter performs step-up and step-down operations to discharge capacitor charges, then the capacitors are discharged, but energy loss increases due to reactor losses and switching losses
Solution Approach 1:
The control device changes the operational parameters of the step up-down converter by setting a target duty ratio that maximizes total loss. This parameter adjustment optimizes the discharge process by controlling the switching element's on-time ratio, thereby increasing energy dissipation rate and reducing discharge time while managing the trade-off between energy loss and discharge speed
2Reliability
If the relay is turned off to discharge residual charge of capacitors, then safety is improved, but the discharge time becomes prolonged
Solution Approach 1:
The control device dynamically adjusts the duty ratio of the step up-down converter during the discharge process. By making the control parameter adaptive and time-varying, the system optimizes the discharge rate at different stages, achieving both safe operation (relay off) and reduced discharge time through dynamic parameter optimization
3Productivity
If the switching element operates at high frequency to reduce discharge time, then discharge speed improves, but switching loss increases
Solution Approach 1:
The control device uses feedback control to monitor the actual duty ratio and adjust it to match the target duty ratio that maximizes total loss. This closed-loop control ensures optimal switching frequency and duration, balancing discharge speed with switching loss by continuously adapting the switching element's operation based on system state
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 significantly shortens the time required to discharge the capacitors to a threshold value, reducing energy loss and improving operational efficiency.
Implementation Method 1
a step up-down converter having a switching element and a reactor, the step up-down converter being connected to a first electric power line and a second electric power line... configured to exchange electric power between the first electric power line and the second electric power line while converting the voltage of the electric power
Implementation Method 2
a first capacitor attached to the first electric power line, and a second capacitor attached to the second electric power line
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
In a drive unit including a motor (32), an inverter (34), a first electric storage device (36), a step up-down converter (40), a first capacitors (46) and a second capacitors (48), a DC-DC converter (54), and a relay (SMR), the DC-DC converter (54) is driven, while a target duty ratio of the step up-down converter (40) is set such that a total loss of the step up-down converter (40) and the DC-DC converter (54) becomes greater than a maximum loss value of the step up-down converter (40), and the step up-down converter (40) is controlled, when the relay (SMR) is turned off to discharge charge of the first capacitor (46) and the second capacitor (48).