High-Voltage Inverter Submodule for Fast Short-Circuit Current Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multipoint converters face challenges in safely limiting short-circuit currents and avoiding system damage, particularly in high-voltage applications where cheap mechanical switches for high DC voltages are not available, leading to high transmission losses and inefficient overvoltage limiting.
Innovation Solution
The submodule design connects two subunits via connecting means with emitter and collector branches, potential isolation diodes, and a switching branch, ensuring that short-circuit currents are controlled internally, reducing the need for external switches and allowing quick absorption of energy to prevent high voltages, and allowing the converter to resume operation without recharging energy storage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If power semiconductor switches are used in the DC intermediate circuit of high-voltage DC transmission systems, then switching speed and control precision are improved, but transmission losses increase due to high voltage requiring a large number of power semiconductors connected in series
Solution Approach 1:
The converter is divided into multiple submodules connected in series, each submodule containing power semiconductor switches. This segmentation allows the high voltage to be distributed across multiple lower-voltage components, reducing the voltage stress on each individual switch and thereby reducing transmission losses while maintaining fast switching capability
Solution Approach 2:
The patent introduces a hierarchical structure with submodules as intermediate units between the power semiconductor switches and the high-voltage DC line. This dimensional organization (switches → submodules → DC line) allows the system to achieve both fast switching response and reduced losses by managing voltage distribution across multiple levels
2Reliability
If overvoltage limiters are provided in parallel with power semiconductors to protect against high voltage, then reliability is improved, but device complexity and transmission losses increase
Solution Approach 1:
The submodules serve multiple functions simultaneously: they provide voltage distribution, overvoltage limiting, and switching capability. Each submodule acts as both a voltage-dividing element and a protective element, eliminating the need for separate overvoltage limiter devices and reducing overall system complexity
Solution Approach 2:
The protective function against overvoltage is merged into the submodule structure itself. The submodules are designed to inherently limit overvoltage through their series connection configuration and internal impedance, combining protection functionality with the basic voltage distribution function rather than adding separate protection devices
3Strength
If a large number of power semiconductors are connected in series to handle high voltages, then voltage handling capability is improved, but transmission losses and device complexity increase
Solution Approach 1:
The high-voltage handling capability is achieved by segmenting the system into multiple submodules, each handling a portion of the total voltage. This segmentation reduces the voltage stress on each individual power semiconductor switch, allowing the use of lower-voltage-rated switches with lower conduction losses while collectively handling the full high voltage
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 short-circuit currents in both directions, avoids system damage, and reduces transmission losses by allowing the converter to manage short circuits without external switches, ensuring quick fault isolation and minimizing operational disruptions.
Implementation Method 1
a potential isolation diode is arranged in the emitter connection branch and in the collector connection branch
Implementation Method 2
a first energy storage, a first series connection of two power semiconductor switching units connected in parallel with the first energy storage
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a submodule (7) for developing an inverter (1) for high-voltage use, having a first sub-unit (5) comprising a first energy store (18), a first series circuit (11) of two power semiconductor switching units (12, 13) connected in parallel with the first energy store (18), each comprising a power semiconductor (14, 15) that can be switched on and off, having the same pass-through direction, and each being conductive opposite the nominal pass-through direction, and comprising a first connection terminal (x2), connected to the potential point between the power semiconductor switching units (12, 13) of the first series circuit (11), and a second sub-unit comprising a second energy store (26), a second series circuit (19) of two power semiconductor switching units (20, 21) connected in parallel with the second energy store (26), each comprising a power semiconductor (22, 23) that can be switched on and off, having the same pass-through direction, and each being conductive opposite the nominal pass-through direction, and comprising a second connection terminal (x1) connected to the potential point between the power semiconductor switching units (20, 21) of the second series circuit (19), limiting short circuit currents quickly, reliably, and effectively in case of a fault, wherein the first sub-unit and the second sub-unit (10) are connected to each other by connection means (27) designed such that a current flow between the first connection terminal (x2) and the second connection terminal (x1) in both directions takes place only via the first energy store (18) and/or the second energy store (26) in a selected switching state of all power semiconductor switching units (12, 13, 20, 21).