DC Converter Protection Circuit for Short-Circuit Current Damping
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Solution Overview
Problem
Flexible direct-current power transmission systems face challenges in effectively suppressing short circuit current and damping current oscillation, leading to prolonged equipment exposure to high-current surges and increased destabilization risk, due to the limitations of existing protection methods and the use of IGBTs in voltage source converters.
Innovation Solution
A converter with a protection device comprising a resistor unit and a bidirectional circulation current switch, connected in parallel, is integrated into the system to rapidly suppress short circuit current and damp oscillations, utilizing IGBTs, IGCTs, or MOSFETs as switching transistors, and sharing cooling and energy access with the converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the alternating-current incoming breaker is directly switched off to shut down the entire direct-current power transmission system, then the system is protected from short circuit current, but the system recovery time is prolonged and economic loss increases
Solution Approach 1:
The invention segments the protection function from the main power transmission function by introducing a dedicated protection device with bidirectional circulation current switches that can independently suppress short circuit current without shutting down the entire system. This allows the protection function to operate separately while the main system remains operational.
Solution Approach 2:
The protection device acts as an intermediary between the short circuit fault and the main power transmission system. It introduces bidirectional circulation current switches that can rapidly suppress short circuit current through controlled current circulation, mediating the fault condition without requiring complete system shutdown.
2Ease of manufacture
If diode devices are connected in parallel in the flexible direct-current power transmission converter, then the converter structure is simplified, but the attenuation of short circuit current becomes difficult due to the diodes providing a current loop
Solution Approach 1:
The invention replaces static diode devices with dynamic bidirectional circulation current switches that can actively control current flow. These switches can dynamically open or close based on system conditions, enabling active suppression of short circuit current while maintaining the parallel connection structure for simplicity.
Solution Approach 2:
The invention changes the operational parameters of the switching devices from passive diode conduction to active controlled switching. The bidirectional circulation current switches can control the timing and magnitude of current flow, transforming the system from passive current circulation to active current management that can suppress short circuit currents.
3Device complexity
If conventional protection methods are used in flexible direct-current power transmission, then the system structure remains simple, but equipment is exposed to high-current surges for longer time causing economic loss
Solution Approach 1:
The protection device is pre-configured with bidirectional circulation current switches that are ready to activate immediately upon detecting a short circuit fault. This preliminary preparation enables rapid response without requiring complex real-time decision-making or system reconfiguration during the fault condition.
Solution Approach 2:
The invention replaces the mechanical approach of complete system shutdown with an electronic control approach using bidirectional circulation current switches. This substitution enables faster, more precise control of short circuit current attenuation while maintaining overall system operational status.
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
The solution effectively shortens fault current attenuation time, reduces economic loss, and enhances equipment safety by rapidly suppressing short circuit currents and damping oscillations, while being structurally simple and cost-effective.
Implementation Method 1
A converter with a protection device comprising a resistor unit and a bidirectional circulation current switch, connected in parallel
Implementation Method 2
A converter with a protection device comprising a resistor unit and a bidirectional circulation current switch, connected in parallel
Data Source
Figure 1(a)~2
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AI summary
The present invention discloses a direct-current power transmission protection device, including a resistor unit and a bidirectional circulation current switch unit, and the resistor unit and the bidirectional circulation current switch unit being connected in parallel to form the protection device, where at least one resistor is cascaded to form the resistor unit, and at least one bidirectional circulation current switch is cascaded to form the bidirectional circulation current switch unit. In addition, the present invention also provides a converter including the protection device, and at least one protection device is connected in series in each phase unit. The present invention provides the protection device, the converter and a protection method for flexible direct-current power transmission, which can rapidly and effectively suppress direct-current short circuit current and damp current oscillation, and not only can better protect equipment safety, but also can greatly shorten fault current attenuation time, thus shortening direct-current shutdown time and further decreasing economic loss and system destabilization risk caused by shutdown to the max. Moreover, the protection device is structurally simple and low in cost, and has good implementability and economic efficiency.