Self-Feeding Converter Circuit for Resistor Overload Sensing
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Solution Overview
Problem
In modular multilevel conversion devices, the self-feeding circuit's current limiting resistor can malfunction, leading to an overloaded state and potential overheating due to excessive current, necessitating a method to sense and prevent resistor overload.
Innovation Solution
The self-feeding circuit includes an overload sensing circuit that monitors the control signal for the switching element connected in series with the resistor, allowing for the detection of an overloaded state and preventing overcharge by controlling the switching element's on-off operation, thereby preventing resistor overheating without requiring temperature sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the current limiting resistor value is reduced to limit inrush current, then the capacitor charging speed increases, but the resistor may enter an overloaded state and overheat due to excessive current
Solution Approach 1:
The patent applies dynamics by making the resistor value changeable over time. The switching element transitions the resistor from a low resistance state during charging to a high resistance state during normal operation, allowing the system to adapt to different operational phases and avoid resistor overheating while maintaining fast charging speed
Solution Approach 2:
The patent uses periodic action through the switching element that periodically changes the resistor's resistance value. During capacitor charging, the resistor is in a low resistance state to enable fast charging, and during normal operation, it switches to a high resistance state to prevent overload, creating a cyclic pattern that resolves the contradiction between charging speed and temperature control
2Reliability
If a temperature sensor is added to detect resistor overload, then resistor overheating can be prevented, but the device complexity and cost increase
Solution Approach 1:
The patent applies self-service by enabling the system to monitor and protect itself without external temperature sensors. The control unit uses existing circuit parameters and switching elements to detect resistor overload conditions and automatically adjust the resistor state, allowing the system to self-diagnose and self-protect against overheating
Solution Approach 2:
The patent implements feedback by having the control unit continuously monitor circuit parameters and use this information to control the switching element. The control unit receives feedback about the capacitor charging state and resistor condition, then adjusts the resistor resistance accordingly, creating a closed-loop control system that prevents overload without requiring additional temperature sensing hardware
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 solution effectively senses and prevents resistor overload, ensuring reliable operation of the power conversion apparatus by managing the switching element's state based on the control signal, thus avoiding resistor damage and maintaining efficient power supply.
Implementation Method 1
a capacitor connected electrically in series between the terminals of the DC capacitor of the main circuit
Implementation Method 2
a current limiting resistor connected between the terminals of the DC capacitor of the main circuit
Implementation Method 3
a switching element connected in series with the resistor between the terminals of the capacitor
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A self-feeding circuit (7) includes a second electricity storage element (C2) electrically connected between the terminals of a first electricity storage element (C1) of a main circuit (6), a power supply circuit (10) configured to convert the voltage of the second electricity storage element (C2) into a power supply voltage for a driving circuit (8), and a voltage detector (32) configured to detect the voltage of the second electricity storage element (C2). A unit converter (5) includes a first resistor (R1) connected to the second electricity storage element (C2) electrically in series between the terminals of first electricity storage element (C1), and a second resistor (R2) and a first switch (T1) connected electrically in series between the terminals of the second electricity storage element (C2). The power supply circuit (10) is configured to prevent an overcharge of the second electricity storage element (C2) by generating a control signal (S1) for controlling the first switch (T1) on and off based on the detection value from the voltage detector (32). The power supply circuit (10) is further configured to sense an overloaded state of the second resistor (R2) based on the control signal (S1).