Series Switch Pre-Charging to Reduce Common-Mode Voltage
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Solution Overview
Problem
In photovoltaic power generation systems, the sudden change in voltage between the ends of switch components when they are turned on leads to common-mode voltage interference, causing strong interference with power and control signals and posing a risk to system operation.
Innovation Solution
A device is introduced that connects two ends of one switch component in parallel to a passive component, such as a resistor, allowing the high-voltage end to charge the low-voltage end, thereby reducing the voltage difference and minimizing common-mode voltage interference when the switch is turned on.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two switch components are connected in series for safety regulation, then system reliability is improved, but common-mode voltage interference increases when switches are turned on
Solution Approach 1:
A pre-charging resistor is introduced as an intermediary component connected in parallel with the second switch component. This resistor serves as a mediator that provides a controlled charging path for the capacitor at the low-voltage end of the second switch, preventing sudden voltage changes when the switch closes. The resistor is temporarily active during switch operation and then disconnected, allowing the system to maintain both reliability and low interference.
Solution Approach 2:
The pre-charging resistor performs preliminary action by charging the capacitor at the low-voltage end of the second switch component before the switch closes. This pre-charging process reduces the voltage difference that would otherwise exist across the switch contacts, thereby preventing the sudden voltage change and common-mode interference that would occur during switch closure.
2Reliability
If the second switch component is turned on after the first switch component, then safety requirements are met, but a large voltage difference exists across the second switch causing peak current
Solution Approach 1:
The pre-charging resistor acts as an intermediary that provides a controlled path for charge transfer to the capacitor at the low-voltage end of the second switch. This mediator component limits the rate of voltage change during charging, preventing the formation of large peak currents when the second switch closes, while still allowing the sequential switching operation required for safety.
Solution Approach 2:
The pre-charging resistor provides beforehand cushioning by absorbing and gradually transferring the voltage difference energy to the capacitor before the second switch closes. This cushioning effect prevents the sudden energy release that would create peak current, protecting the system from harmful current surges while maintaining the safety-critical sequential switching sequence.
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 reduces the common-mode voltage and the corresponding current, minimizing interference with the power supply system and protecting the switch components from damage.
Implementation Method 1
two ends of a first switch component in at least one phase of the output end of the inverter are connected in parallel to a passive component... allowing the high-voltage end to charge the low-voltage end
Data Source
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AI summary
This application discloses a device, a method, and a system for resolving common-mode voltage interference. The device is applied to a power supply system, the power supply system includes a power converter and a switch mechanism, each phase of an output end of the power converter is connected to a downstream circuit by using the switch mechanism, the power converter is configured to perform electric energy conversion, the switch mechanism includes a first switch component and a second switch component that are connected in series, the device includes a controller and a passive component, two ends of the first switch component in at least one phase of the output end of the power converter are connected in parallel to the passive component, and the controller is configured to: control the second switch component to be turned on, and when a voltage difference between the two ends of the first switch component is less than a preset voltage, control the first switch component to be turned on. When the second switch component connected in series to the first switch component is turned on first, a high-voltage end charges a low-voltage end by using the passive component, to reduce the voltage difference between the two ends of the first switch component. After the voltage difference between the two ends of the first switch component is less than the preset voltage, the first switch component is turned on. In this case, a case in which there is a very large sudden change between voltages at the two ends of the first switch component due to closing of the first switch component does not occur, so that a common-mode current can be reduced, a power supply risk can be prevented in the power supply system, and the switch component is protected, thereby prolonging a service life of the switch component.