Medium Voltage Inverter Auxiliary Rectifier Bypass
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Solution Overview
Problem
Existing medium voltage inverter systems face instability and failure when a serially connected H-bridge type inverter experiences a fault, such as a fuse opening or SCR burn-out, leading to disruption in power supply and inability to short-circuit the output terminal.
Innovation Solution
The system incorporates an auxiliary rectifying unit with blocking diodes and an inrush current limiting resistor, along with a smoothing unit and a controller, to ensure continuous operation by bypassing the failed unit power cell, even if there is a failure at the input terminal, by supplying power to the controller and maintaining voltage to the smoothing unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a serially connected H-bridge type inverter is used to achieve medium voltage output, then the inverter can provide flexible operation and effective power system control, but the system becomes unstable and fails when a fault occurs such as fuse opening or SCR burn-out
Solution Approach 1:
The inverter system is divided into multiple independent unit power cells, each with its own rectifying unit, smoothing unit, and controller. This segmentation allows individual cells to be isolated and bypassed when faulty, preventing system-wide failure while maintaining overall system operation.
Solution Approach 2:
The controller is pre-configured with bypass contactors that can immediately short-circuit the output terminal upon detecting a fault condition. This preliminary preparation of bypass paths enables rapid fault isolation without requiring complex real-time decision-making during failure events.
2Reliability
If the controller is equipped to short-circuit the output terminal upon failure, then the system can maintain stability during faults, but the controller requires continuous power supply even during abnormal operations
Solution Approach 1:
The auxiliary rectifying unit serves multiple functions: it provides power to the controller during normal operation, maintains power supply during abnormal operations when the main rectifying unit fails, and enables the bypass function to operate independently of the main power path. This multi-functionality ensures controller operation without requiring continuous high power consumption.
Solution Approach 2:
The auxiliary rectifying unit acts as an intermediary power source that bridges the gap between the main rectifying unit and the controller. When the main rectifying unit fails, the auxiliary unit mediates by providing alternative power path through the supply unit, ensuring the controller remains operational for fault management.
3Reliability
If an auxiliary rectifying unit is added to provide power during abnormal operations, then the controller can maintain bypass functionality, but the system complexity and component count increase
Solution Approach 1:
The auxiliary rectifying unit is merged with the existing power supply architecture by integrating it with the supply unit and controller power management system. This merging approach allows the auxiliary unit to complement rather than duplicate existing components, reducing overall system complexity while maintaining continuous operation capability.
4Object-affected harmful factors
If blocking diodes and inrush current limiting resistor are incorporated in the auxiliary rectifying unit, then the system prevents damage from excessive currents, but the circuit complexity increases
Solution Approach 1:
The inrush current limiting resistor and blocking diodes are pre-installed in the auxiliary rectifying unit to cushion against excessive currents before they can damage the controller or other sensitive components. This beforehand protection prevents harmful effects without requiring complex active current limiting circuits.
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 configuration enables stable operation and bypass functionality in medium voltage inverter systems, ensuring continuous power supply and preventing damage from excessive inrush currents, thereby enhancing operational stability and reliability.
Implementation Method 1
a first rectifying unit configured to rectify an AC voltage provided through an input terminal to a DC voltage
Implementation Method 2
the smoothing unit including a capacitor
Implementation Method 3
an inrush current limiting resistor arranged between the second rectifying unit and the supply unit and configured to limit an inrush current to the supply unit
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A medium voltage inverter system is provided. The inverter system includes a controller configured to short-circuit the output terminal of the inverter unit when failure occurs, a supply unit configured to supply an electric power to the controller, and an auxiliary rectifying unit configured to rectify the AC voltage provided through the input terminal and to supply the rectified AC voltage to the supply unit.