Decoupling Filter for High Voltage DC Current Limiting
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Solution Overview
Problem
High voltage DC power systems with low feeder inductance pose challenges for current limiting in solid state power controllers (SSPCs), as traditional pulse width modulation methods are ineffective, leading to issues with heat management, complexity, cost, and weight in power distribution systems.
Innovation Solution
Incorporating a decoupling filter with a second inductor and resistor in parallel with a solid state switch, which is controlled based on current limiting conditions to provide additional output impedance and minimize voltage distortion, combined with an output filter featuring a first inductor and resistor in series with a solid state switch, allowing for efficient current limiting and inrush current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PWM current limiting is used in high voltage DC systems with low feeder inductance, then the system can operate with simple control, but current limiting becomes ineffective and excessive heat is generated in the SSPC
Solution Approach 1:
The patent introduces a decoupling filter as an intermediary component between the generator and the SSPC. This filter, containing an inductor and resistor, acts as a mediator that provides the necessary current limiting function without requiring the SSPC to handle the full current stress, thereby preventing excessive heat generation while maintaining reliable current limiting capability.
Solution Approach 2:
The patent segments the current limiting function by separating it from the SSPC and placing it in the decoupling filter. This segmentation allows the SSPC to focus on power switching while the filter handles current limiting, dividing the protective function into distinct components that can operate independently and efficiently.
2Reliability
If a decoupling filter is added to provide current limiting in high voltage DC systems, then current limiting capability is improved, but system complexity increases
Solution Approach 1:
The decoupling filter is designed to serve multiple functions simultaneously: it provides current limiting during fault conditions, filters voltage distortion from the generator, and decouples the generator from the power distribution module. This multi-functionality reduces the need for separate components, thereby limiting the increase in system complexity while achieving reliable current limiting.
3Temperature
If complex thermal management techniques are implemented to handle heat from SSPC, then temperature control is improved, but system weight and size increase
Solution Approach 1:
By introducing the decoupling filter as an intermediary, the patent reduces the thermal burden on the SSPC. The filter absorbs excess energy and limits current stress, which directly reduces heat generation at the SSPC. This approach avoids the need for heavy thermal management systems while still achieving effective temperature control.
4Reliability
If feeder length is increased to provide sufficient inductance for PWM current limiting, then current limiting effectiveness is improved, but system length and weight increase
Solution Approach 1:
The patent extracts the inductance function from the feeder and concentrates it in the decoupling filter's inductor. This allows the feeder to remain short while still providing sufficient inductance for current limiting, as the filter's inductor compensates for the low inductance of short feeders in high voltage DC systems.
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 enhances current limiting capability, reduces voltage distortion, and improves power quality during short circuits, while minimizing filtering requirements and overall system weight, size, and cost, thereby enhancing safety and efficiency in high voltage DC power systems.
Implementation Method 1
the decoupling filter comprising a second inductor connected in parallel with a second resistor and a second solid state switch
Implementation Method 2
the decoupling filter comprising a second inductor connected in parallel with a second resistor and a second solid state switch
Data Source
AI summary
An electric power generating system (EPGS) (100, 200, 300) includes a generator (102, 202, 302) configured to power a direct current (DC) load (109A, 209A, 309A) via a power distribution module (107, 207, 307). The power distribution module (107, 207, 307) includes a solid state power converter (SSPC) (108A, 208A, 308A). A decoupling filter (106, 206, 306) connected between the generator (102, 202, 302) and the power distribution module (107, 207, 307), and includes an inductor connected in parallel with a resistor and a solid state switch, the resistor and solid state switch being connected in series. During current limiting conditions in the SSPC (108A, 208A, 308A), the solid state switch of the decoupling filter (106, 206, 306) is configured to be open, and during the absence of current limiting conditions in the SSPC (108A, 208A, 308A), the solid state switch of the decoupling filter (106, 206, 306) is configured to be closed.