Precharge Control Using Time-Based Completion Detection
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Solution Overview
Problem
Existing precharge control systems face challenges in reliably determining the completion of capacitor precharge due to variations in voltage sensor accuracy and capacitor characteristics, leading to potential overdischarge and increased costs from selecting high-accuracy sensors and high-withstand voltage contactors.
Innovation Solution
A precharge control apparatus that sets a set voltage based on the maximum error of voltage sensor detection errors and a set time based on the time constant of resistor and capacitor values, ensuring the capacitor voltage difference reaches a withstand voltage threshold, allowing for reliable precharge completion determination without requiring high-accuracy sensors or contactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-accuracy voltage sensors and high-withstand voltage contactors are selected to ensure reliable precharge completion determination, then system reliability is improved, but device cost increases
Solution Approach 1:
The patent changes the determination criterion from a fixed voltage threshold to a dynamic time-based criterion. The control device determines precharge completion based on whether a predetermined time period has elapsed since the voltage difference fell below a threshold, rather than relying solely on the voltage threshold itself. This parameter change allows the system to compensate for sensor accuracy variations and capacitor characteristic variations without requiring high-accuracy components.
Solution Approach 2:
The patent introduces a time margin as a cushioning mechanism against uncertainty. By requiring that a predetermined time period elapse after the voltage difference falls below the threshold before determining precharge completion, the system creates a safety buffer that accounts for potential measurement errors and component variations. This beforehand cushioning ensures reliable determination even with lower-accuracy sensors and components.
2Device complexity
If a fixed voltage threshold is used to determine precharge completion, then control simplicity is improved, but measurement precision requirements increase
Solution Approach 1:
The patent transitions from a static voltage threshold determination to a dynamic time-based determination. The control logic now considers both the voltage threshold and the elapsed time since the threshold was met. This dynamic approach reduces the stringency of measurement precision requirements because the time element provides additional information that compensates for voltage measurement uncertainties.
Solution Approach 2:
The patent introduces time-based feedback to the precharge completion determination process. The control device continuously monitors both the voltage difference and the elapsed time, using the time information as feedback to confirm that precharge has truly completed. This feedback mechanism allows the use of less precise voltage sensors while maintaining reliable determination through the additional temporal dimension.
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
Enables reliable precharge completion determination even with low-accuracy sensors and varying capacitor characteristics, reducing the need for costly high-accuracy components and preventing overdischarge, while maintaining system safety and efficiency.
Implementation Method 1
a voltage difference between a battery voltage and a capacitor voltage detected by a voltage sensor becomes equal to or less than a set voltage
Implementation Method 2
a time from when the voltage difference becomes twice the maximum error to when the voltage difference becomes equal to or less than a withstand voltage of a main contactor, under states where the precharge causes the capacitor voltage to increase with a time constant when a resistance value of a resistor and a capacitance of a capacitor each are largest within an allowable error
Implementation Method 3
a smoothing capacitor connected in parallel to a load before closing a main contactor that conducts a power supply path from a battery to a load
Data Source
AI summary
A precharge control apparatus starts precharge of a capacitor. The precharge is determined to be completed when a set time has elapsed since a voltage difference between a battery voltage and a capacitor voltage detected by a voltage sensor becomes equal to or less than a set voltage. The set voltage is based on a maximum error obtained by adding maximum values of detection errors of the battery voltage and capacitor voltage by the voltage sensor. The set time is based on a time from when the voltage difference becomes twice the maximum error to when the voltage difference becomes equal to or less than a withstand voltage of a main contactor, under states where the precharge causes the capacitor voltage to increase with a time constant when a resistance value of a resistor and a capacitance of the capacitor each are largest within an allowable error.