DVR Booster Transformer Protection Using Primary-Winding Shorting
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Solution Overview
Problem
Existing short-circuit protection systems for DVR voltage variation compensators are inadequate in protecting the booster voltage converter from damage due to short circuits and long-term overloads, leading to potential interruptions in power supply to sensitive loads.
Innovation Solution
A system with sensors and discriminators measures currents in the secondary winding of the booster transformer and DC circuit, triggering a solid-state switch to immediately short-circuit the primary winding, disconnecting the booster transformer from the power grid and converter, using smaller contactors to ensure continuous power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If circuit breakers or fuses are used to protect the booster voltage converter, then short-circuit protection is provided, but the connection cannot be interrupted because the booster transformer behaves like a current transformer during short-circuit
Solution Approach 1:
Instead of protecting the secondary winding from short-circuit current (which cannot be interrupted), the invention inverts the protection approach by short-circuiting the primary winding. This redirects the harmful current through the primary side where it can be safely handled, while maintaining continuous operation on the secondary side.
Solution Approach 2:
The invention introduces a solid-state switch as an intermediary device between the primary winding and the short-circuit condition. This switch acts as a mediator that can rapidly short-circuit the primary winding to protect the converter without requiring interruption of the secondary circuit.
2Reliability
If bypass contactor and cutoff contactors are used for protection, then short-circuit protection is achieved, but the switching cycle duration causes peak voltage increase that exposes transistors to damage
Solution Approach 1:
The invention replaces the mechanical contactor system with a solid-state switch for the critical protection function. The solid-state switch operates much faster than mechanical contactors, eliminating the voltage spike problem caused by delayed switching. The mechanical contactors are retained only for the bypass function where slower operation is acceptable.
Solution Approach 2:
The solid-state switch performs preliminary action by immediately short-circuiting the primary winding as soon as a short-circuit condition is detected. This preliminary protection action occurs before the mechanical contactors can operate, preventing the dangerous voltage buildup that would otherwise occur during the contactor switching cycle.
3Reliability
If protection system uses three apparatuses for large currents in secondary winding, then short-circuit protection is provided, but construction cost increases
Solution Approach 1:
The invention segments the protection function into two distinct parts: primary winding protection handled by a solid-state switch, and secondary winding protection handled by a bypass contactor. This segmentation allows each component to be optimized for its specific function and rated for appropriate current levels, reducing the need for expensive high-current apparatuses on the secondary side.
Solution Approach 2:
The invention uses a solid-state switch for the critical primary winding protection function, which is more reliable and has longer life than mechanical contactors. The bypass contactor is used only for the secondary side where it can be simpler and less expensive. This strategic allocation reduces overall system cost while maintaining reliability.
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 protects the booster voltage converter from damage by limiting voltage peaks and ensuring continuous power supply to sensitive loads without interruptions, reducing costs and contactor switching times.
Implementation Method 1
The booster transformer, during short-circuit in a mains-supplied load, behaves like a current transformer. For this reason, the connection of the booster voltage converter to the primary winding of the booster transformer, which constitutes its load in the emergency state, cannot be interrupted.
Implementation Method 2
The flow of short-circuit current through the secondary winding of the booster transformer forces the appearance of a high voltage on the primary winding and a sharp increase in the voltage on the DC circuit capacitor of the booster voltage converter.
Data Source
Figure 1
AI summary
The invention solves the issue of a method and system for short-circuit protection of DVR voltage variation compensator with booster transformer. Such compensators are installed in LV power supply networks in order to reduce voltage fluctuations, characteristic of networks working with RES.