Detecting Welded Switch Contacts in Line Converter Systems
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Solution Overview
Problem
Existing line converter systems for connecting alternative power sources to utility grids lack an effective method to test the operation of electromechanical switches, particularly to detect stuck contacts which can lead to safety and operational issues.
Innovation Solution
A line converter system with an inverter, line switches connected in series, a voltage detector, and a controller that uses a method to detect stuck contacts by opening inverter switches, transmitting open commands, and determining voltage presence between switch points to identify stuck contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromechanical switches are used in line converter systems, then safety disconnection and operational control are improved, but the risk of stuck contacts and undetected failures increases
Solution Approach 1:
The system performs a self-test before connecting to the utility grid by commanding line switches to open and detecting whether they actually open. This preliminary action identifies stuck contacts before they can cause safety hazards during normal operation.
Solution Approach 2:
The voltage detector provides feedback about the actual state of line switches to the controller. By monitoring voltage at switch locations and comparing it to expected values, the system receives continuous feedback on switch operation status to detect anomalies.
2Reliability
If self-test capability is added to detect switch status, then operational safety is improved, but system complexity increases
Solution Approach 1:
The voltage detector serves multiple functions: it monitors line voltage during normal operation and detects switch status during self-test. This multi-functionality allows self-test capability to be added without requiring completely separate test equipment, thereby limiting the increase in system complexity.
Solution Approach 2:
The line converter system performs its own self-test using its existing components (controller, voltage detector, and line switches). The system tests itself without requiring external test equipment or manual intervention, adding safety capability while minimizing additional complexity.
3Measurement precision
If voltage detection is performed between line switches, then detection accuracy is improved, but the number of detection points and system complexity increases
Solution Approach 1:
The system divides the detection task into segments by testing each line switch independently. By commanding switches to open in sequence and detecting voltage at specific points, the system achieves precise identification of which specific switch has stuck contacts rather than just detecting a general fault.
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 system effectively identifies and prevents the connection of stuck contacts to the utility grid, ensuring safe and reliable operation by using a processor and computer-readable medium to execute a method that determines the status of line switches, thereby preventing potential failures.
Implementation Method 1
a voltage detector... determining whether the voltage detector has detected a voltage
Data Source
AI summary
A system for the detection of welded contacts in a circuit of a line converter system has a plurality of inverter switches, a plurality of utility switches in which a pair of utility switches is connected in series through a line to a utility, a voltage detector, an electronic controller, and a DC input source. The line converter system converts incoming DC power into AC output power that is delivered to the utility grid. The voltage detector measures the voltage across a first node and a second node of the circuit and provides an output that is interpreted by an electronic controller for each step performed during a method of detection of welded contacts. The detection method has a sequence of test steps in which at least one switch is opened and/or closed, a DC bus of the inverter or the utility grid is used as a stimulus voltage, and the voltage is measured. If a voltage is not detected across the first and second nodes, the test sequence is continued until a welded contact is detected or the electronic controller determines that none of the contacts are welded. If the controller determines that none of the contacts are welded, the line converter system is permitted to connect and supply AC power to the utility.