AC Filter Switching for Reactive Power Suppression Without Breaker Wear
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Solution Overview
Problem
Conventional power systems face premature AC circuit breaker failure due to frequent switching required to suppress reactive power, leading to early replacement needs.
Innovation Solution
A power system design incorporating an AC filter circuit with an inductor and capacitor, along with a first switch between the capacitor and AC circuit breaker, allows for reactive power suppression without operating the AC circuit breaker, using a Molded Case Circuit Breaker (MCCB) as the first switch to reduce switching frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the AC circuit breaker is operated frequently to suppress reactive power, then reactive power suppression is achieved, but the AC circuit breaker reaches machine life at an early stage
Solution Approach 1:
The invention divides the circuit breaker function into two separate components: the AC circuit breaker handles only large current shutdowns, while a dedicated first switch (MCCB) handles reactive power suppression switching. This segmentation allows each component to perform its specific function without excessive switching, extending the AC circuit breaker's life while maintaining reactive power suppression capability.
Solution Approach 2:
The first switch acts as an intermediary component between the AC filter circuit and the AC circuit breaker. It mediates the reactive power suppression function, preventing the AC circuit breaker from being subjected to frequent switching operations. The first switch absorbs the switching stress, protecting the AC circuit breaker from premature failure.
2Reliability
If the AC circuit breaker is used for reactive power suppression, then reactive power flow is controlled, but switching frequency increases greatly
Solution Approach 1:
The invention segments the switching functions by introducing a first switch dedicated to reactive power suppression. This separates the high-frequency reactive power switching from the low-frequency AC circuit breaker operations, allowing reactive power control to be achieved with appropriate switching frequency while preserving the AC circuit breaker for its primary protection function.
Solution Approach 2:
The first switch serves as an intermediary that handles all reactive power suppression switching operations. This intermediary component absorbs the high switching frequency requirements, preventing these operations from affecting the AC circuit breaker's machine life and maintaining efficient reactive power control.
3Reliability
If a DC circuit breaker is provided between the secondary battery and power conversion device to suppress reactive power, then reactive power suppression is possible, but the device complexity increases
Solution Approach 1:
The invention replaces the expensive and complex DC circuit breaker with a more economical first switch (MCCB) that is better suited for the reactive power suppression function. This substitution reduces device complexity and cost while achieving the same functional outcome of reactive power suppression in the AC filter circuit.
Solution Approach 2:
The invention changes the type of switching device from a DC circuit breaker to an AC-rated MCCB (first switch) that is appropriate for the AC filter circuit application. This parameter change in switch selection optimizes the system for its actual operating conditions, reducing complexity while maintaining reactive power suppression capability.
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 approach effectively suppresses reactive power flow into and out of the AC filter circuit, extending the life of the AC circuit breaker and reducing replacement frequency while maintaining grid stability.
Implementation Method 1
an AC filter circuit including an inductor having one end connected in series to an output end of the AC power supply and a capacitor having one end receiving a voltage of another end of the inductor
Implementation Method 2
an AC filter circuit including an inductor having one end connected in series to an output end of the AC power supply
Data Source
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AI summary
A power system includes an AC power supply, an AC filter circuit, an AC circuit breaker, and a first switch. The AC filter circuit includes an inductor having one end connected in series to an output end of the AC power supply, and a capacitor having one end receiving a voltage at another end of the inductor. The AC circuit breaker exists between the other end of the inductor and an electric power grid. The first switch switches a state between the one end of the capacitor and a wire connecting the other end of the inductor to the AC circuit breaker, between a connected state and a disconnected state. The AC power supply may be a generator and include a generator control unit controlling the generator. The generator control unit may turn off the first switch when the AC power supply operates in a predetermined standby mode.