Electric Vehicle Controller Duty Ratio Control
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Solution Overview
Problem
Existing electric vehicle controllers face issues with unnecessary breaker operation in the substation due to the lack of commonality between the overvoltage suppression circuit and the brake chopper circuit, leading to increased device size, cost, and maintainability challenges, as well as unintended tripping caused by sudden voltage changes.
Innovation Solution
An electric vehicle controller is designed with a power consumption circuit connected in parallel to the inverter, featuring a switching device and a power consumption resistor, along with a control unit that manages duty ratios to prevent unnecessary breaker operation by using the brake chopper circuit for both power consumption and overvoltage suppression, ensuring the brake chopper circuit operates before the line breaker is opened.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the brake chopper circuit is operated before the line breaker is opened during overvoltage suppression, then the switching device and brake chopper circuit are protected against overvoltage, but current flows from the power supply source to the brake chopper circuit through the line breaker causing unnecessary operation of the ΔI detector and potential tripping of the breaker in the substation
Solution Approach 1:
The patent merges the overvoltage suppression circuit and brake chopper circuit into a single integrated circuit. The brake chopper circuit performs dual functions: consuming regenerative power during normal operation and suppressing overvoltage when needed. This eliminates the need for a separate overvoltage suppression circuit while achieving the desired protection function.
Solution Approach 2:
The control unit is configured to operate the brake chopper circuit before opening the line breaker during overvoltage conditions. By activating the brake chopper circuit in advance, the system prepares to consume the overvoltage energy through the power consumption resistor, thereby protecting the switching device and brake chopper circuit from damage while managing the current flow to prevent unnecessary substation breaker operation.
2Reliability
If separate overvoltage suppression circuit and brake chopper circuit are used, then each circuit can be optimized for its specific function, but device size increases and cost and maintainability deteriorate
Solution Approach 1:
The brake chopper circuit is designed to perform multiple functions: it serves as both the regenerative power consumption circuit during normal operation and the overvoltage suppression circuit when voltage exceeds safe levels. The power consumption resistor and switching device are shared between these two functions, reducing the overall number of components needed in the system.
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 configuration prevents unintended breaker operations in the substation while achieving commonality between the overvoltage suppression and brake chopper circuits, reducing device size and cost, and ensuring efficient power consumption during regenerative braking.
Implementation Method 1
a power consumption resistor (7) connected in series with the switching device (6)... the power consumption resistor to consume regenerative power supplied from the motor
Implementation Method 2
an overvoltage suppression resistor connected in series with the overvoltage suppression thyristor... the electrical charge in the filter capacitor is consumed in the overvoltage suppression resistor, thus the voltage of the filter capacitor drops
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An electric vehicle controller 50 includes an inverter 11 that drives a motor 12 by receiving power supplied from an overhead line 1, a brake chopper circuit 8 that includes a switching device 6 and a braking resistor 7 and is connected in parallel with the inverter 11, a voltage detector 9 that detects a bus voltage applied to DC buses 4a and 4b, and a control unit 13 that performs power consumption control of causing the braking resistor 7 to consume regenerative power supplied from the motor 12 and overvoltage suppression control of suppressing the bus voltage from being excessive. The control unit 13 controls the switching device 7 such that a second duty ratio used at the time of performing the overvoltage suppression control is lower than a first duty ratio used at the time of performing the power consumption control.