DC Network Overvoltage Protection Circuit Using Thyristor Quenching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Direct current networks in power plants, supplied via three-phase rectifiers, are inadequately protected against overvoltages from the alternating current network, which can damage DC loads such as sensors, controls, and actuators.
Innovation Solution
A circuit arrangement with means for detecting overvoltages at the input or output of the DC network, utilizing thyristors and controllable switching elements to divert current from current-carrying thyristors, and including a capacitor and inductor to limit current and force the thyristors to turn off, thereby protecting the DC loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a three-phase rectifier is used to supply DC networks in power plants, then the power supply capability is improved, but the vulnerability to overvoltages from the AC network increases
Solution Approach 1:
The patent introduces an intermediary protection circuit between the three-phase rectifier and DC loads. This circuit includes detection means for monitoring overvoltages, switching means (thyristors) for interrupting current flow, and energy storage means (capacitors) for maintaining power supply during switching transitions. The intermediary circuit blocks harmful overvoltages while allowing normal power transmission, resolving the contradiction between power supply capability and overvoltage vulnerability.
Solution Approach 2:
The protection circuit performs preliminary detection of overvoltage conditions before they can damage DC loads. The detection means continuously monitors the DC voltage level, and when an overvoltage threshold is exceeded, the switching means is activated in advance to interrupt the current flow from the rectifier, preventing damage before it occurs.
2Reliability
If overvoltage protection means are added to the DC network, then the reliability against overvoltages is improved, but the device complexity increases
Solution Approach 1:
The protection circuit is designed with multi-functional components that serve both protection and power supply functions. The energy storage means (capacitors) not only maintain voltage during switching but also smooth normal DC output. The switching means (thyristors) can operate in both rectifier and protection modes. This multi-functionality reduces overall system complexity while maintaining high reliability.
Solution Approach 2:
The protection circuit is designed to be self-regulating and automatic. The detection means automatically identifies overvoltage conditions without external intervention, and the switching means automatically interrupts current flow based on detection signals. The circuit requires no manual operation or complex control systems, reducing operational complexity while ensuring reliable protection.
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
Effectively prevents damage from overvoltages by interrupting the load current and limiting the current flow, ensuring the safe operation of critical DC loads in power plants.
Implementation Method 1
The means for taking over can have an energy store as a voltage source, which drives a current through the circuit closed by the first controllable switching element. The energy store can be a capacitor that is charged during operation.
Implementation Method 2
A choke is advantageously arranged in series with the first controlled switching element and the capacitor, which inductor causes a reversal after the capacitor has discharged and thereby causes the first controlled switching element to be automatically extinguished.
Data Source
Figure 1
AI summary
Circuit (S) for protecting at least one DC network with DC loads (1) that can be connected to the circuit (S), wherein the circuit (S) is suitable and configured to supply the DC network with electrical energy via a three-phase rectifier (G) and has the following features: - the circuit (S) comprises a means (2, 3, 4, TH1, LS, CS, DU, DV, DW) for detecting an overvoltage, which is suitable and configured to detect an overvoltage at the input of the DC network, - the circuit (S) comprises a means for receiving a current, which is suitable and configured to impose a current on one or more of the current-carrying thyristors (THU1, THV1, THW1) of the rectifier (G), which leads to the quenching of the thyristor(s) (THU1, THV1, THW1) as soon as the means for detecting the overvoltage has detected an overvoltage.