Link Capacitor Precharge Control via Dynamic Capacitance Measurement
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Solution Overview
Problem
Power supplies for devices like electric vehicles and hybrid vehicles face challenges in managing power flow and capacitance, particularly in preventing overcurrent and inrush currents during battery discharge, which can lead to inefficiencies and potential safety issues.
Innovation Solution
A control method for a power supply that includes a link capacitor connected between an external load and a power relay assembly with a precharge resistor, where the capacitance of the link capacitor is calculated using measured voltages at different times to control precharge and prevent overcurrent, and a control unit manages relay operations to ensure efficient power flow and capacitor charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If precharge is initiated without capacitance measurement, then power flow control is simplified, but overcurrent and inrush currents cannot be effectively prevented
Solution Approach 1:
The patent applies preliminary action by measuring the capacitance of the link capacitor before initiating the precharge process. The control unit calculates the capacitance value based on voltage measurements taken during the precharge process, and uses this pre-calculated capacitance information to determine the optimal precharge timing. This preliminary capacitance assessment enables more reliable overcurrent prevention while maintaining a manageable control methodology.
2Reliability
If capacitance measurement is performed continuously, then capacitor degradation can be monitored, but energy consumption and system complexity increase
Solution Approach 1:
The patent implements periodic action by performing capacitance measurements at specific intervals rather than continuously. The control unit measures the capacitance value during the precharge process and compares it with a predetermined threshold. This periodic measurement approach, triggered at appropriate moments in the charging cycle, effectively monitors capacitor degradation and determines replacement timing while minimizing unnecessary energy consumption associated with continuous monitoring.
3Ease of operation
If precharge resistor is used without capacitance consideration, then power flow control is simpler, but inrush currents cannot be effectively controlled
Solution Approach 1:
The patent applies feedback by using the measured capacitance value of the link capacitor to dynamically control the precharge process. The control unit calculates the capacitance based on voltage measurements during charging, and uses this feedback information to determine the optimal timing for transitioning from precharge to full power flow. This feedback mechanism ensures that the precharge resistor is used effectively to control inrush currents while maintaining operational simplicity.
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 method effectively prevents overcurrent and inrush currents during battery discharge, ensuring efficient power supply and extending the lifespan of the link capacitor by determining its replacement time based on calculated capacitance degradation.
Implementation Method 1
calculating the capacitance of a link capacitor functioning as a buffer while being charged and discharged between a battery of a power supply and an external load
Implementation Method 2
a power relay assembly (PRA) including a precharge resistor to control a power flow between a battery and the external load
Data Source
Figure 1
Figure 2~3
Figure 4A
AI summary
Provided is a control method for a power supply. The control method is for the power supply in which a link capacitor is connected between an external load and a power relay assembly (PRA) including a precharge resistor to control a power flow between a battery and the external load, the control method including: initiating precharge; after the initiating of the precharge, measuring the voltage of the link capacitor by measuring first, second, and third voltages V1, V2, and V3 of the link capacitor at different first, second, and third times T1, T2, and T3; calculating the capacitance C of the link capacitor using the first, second, and third voltages V1, V2, and V3; and terminating the precharge. Therefore, it is possible to calculate the capacitance of the link capacitor functioning as a buffer between the battery of the power supply and the external load while being charged and discharged.