Overvoltage Protection Circuit for Variable-Speed Generators
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Solution Overview
Problem
Existing variable speed constant frequency (VSCF) electrical energy generation systems in aircraft face challenges with overvoltage protection, as current solutions either disrupt the voltage regulation system or require series connection, impacting generator performance and service continuity.
Innovation Solution
An overvoltage protection device is introduced, comprising a circuit with switches and resistors connected between the inverter input terminals, independent of the voltage regulation system, using voltage sensors to detect and manage overvoltages without affecting generator control, and compatible with multiple energy sources and distribution networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crowbar circuit is used to short circuit power lines during overvoltage, then overvoltage protection is achieved, but service interruption occurs and the electrical system must be restarted
Solution Approach 1:
The invention extracts the overvoltage protection function from the main voltage regulation system by implementing a separate, independent protection circuit. This allows the protection function to operate autonomously without disrupting the normal voltage regulation and service continuity, resolving the contradiction between reliable protection and continuous operation.
Solution Approach 2:
The invention introduces an intermediary protection circuit that acts as a mediator between the generator and the power distribution center. This intermediary circuit can quickly respond to overvoltage conditions and limit voltage spikes before they propagate to the loads, while allowing normal operation to continue uninterrupted.
2Reliability
If a protective device is put in series in the machine excitation line to demagnetise the generator, then overvoltage protection is achieved independently of the generator control system, but voltage drops are added to the excitation wiring impacting regulation performances
Solution Approach 1:
The invention segments the protection function from the excitation control system by implementing a separate protection circuit connected to the power lines. This segmentation allows the protection function to operate independently without affecting the precision of the excitation voltage regulation, as the protective device does not intervene in the excitation control path.
3Reliability
If a clipping system is used to eliminate overvoltages on the DC network, then overvoltage protection is achieved, but the clipping system interacts with the voltage regulation system by excitation of the generator reducing independence
Solution Approach 1:
The invention extracts the overvoltage protection function from the voltage regulation system by implementing a separate, dedicated protection circuit. This extraction ensures that the protection function operates independently without interacting with or complicating the voltage regulation system, maintaining both simplicity and independence.
4Reliability
If a clipping system is used to eliminate overvoltages, then overvoltage protection is achieved, but the solution is limited to a configuration with a single generator
Solution Approach 1:
The invention implements a universal protection circuit design that can be applied to various system configurations including single generator, multiple generators, different power distribution architectures, and various load types. The protection circuit's independent architecture and standardized connection method enable it to adapt to diverse system configurations without requiring modification.
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 limits overvoltages at the output of the VSCF system, enhancing service continuity and reducing fault transmission, while allowing for additional delay in voltage regulation to manage overvoltages, thus minimizing constraints on the generator and its regulation.
Implementation Method 1
a capacitive mid-point connected to the aircraft neutral being connected to the input terminals of the inverter via two corresponding capacitors
Data Source
AI summary
Overvoltage protection device for a variable-speed and constant-frequency electrical energy generation system includes at least one DC current generator connected, via a DC current bus to the input terminals of at least one inverter and to at least one regulation module for regulating the output voltage of the at least one inverter. The device includes a circuit including at least one switch in series with a resistor, the circuit being connected between the input terminals of the at least one inverter, at least one measurement sensor for measuring the DC voltage across the input terminals of the at least one inverter, a control circuit connected to the at least one measurement sensor and able to receive a voltage measured by the at least one measurement sensor, compare the measured voltage against a threshold and command the closure of the at least one switch if the measured voltage is greater than the threshold, and command opening thereof if not.