Power Module Relay Closing for Zero-Voltage Bus Pre-Charging
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Solution Overview
Problem
Conventional charging piles with three-phase AC contactors are bulky due to the need for arc quenching devices to manage impulse currents during pre-charging, occupying large internal space and increasing costs.
Innovation Solution
A method and power module that control the closing of relays to pre-charge a bus capacitor when the line voltage is near zero, eliminating the need for arc quenching devices by accurately timing the relay closure to minimize impulse currents, thereby reducing the internal space and cost of the charging pile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a three-phase AC contactor with arc quenching device is used to pre-charge the bus capacitor, then the contactor can handle impulse currents, but the volume of the contactor increases and occupies large space in the charging pile
Solution Approach 1:
The patent applies preliminary action by detecting the voltage across the contactor in advance before closing the contactor. The control unit monitors the voltage and only closes the contactor when the voltage is below a predetermined threshold, preventing impulse current surges before they occur. This eliminates the need for arc quenching devices and reduces contactor volume.
Solution Approach 2:
The patent changes the operational parameter of contactor closing timing based on voltage conditions. Instead of closing the contactor at fixed intervals or upon demand, the system dynamically adjusts the closing moment based on real-time voltage measurements, ensuring closure occurs only when voltage conditions are safe (below threshold), thereby preventing harmful impulse currents.
2Reliability
If arc quenching devices are added to the three-phase AC contactor to avoid contact adhesion, then contact reliability improves, but the device complexity and cost increase
Solution Approach 1:
The control unit performs preliminary voltage detection and evaluation before contactor closure. By assessing whether the voltage is below the predetermined threshold in advance, the system prevents impulse currents that would cause contact adhesion, eliminating the need for complex arc quenching devices and reducing overall system complexity.
Solution Approach 2:
The patent replaces the mechanical arc quenching device with an electronic control system that uses voltage sensing and conditional logic to prevent contactor issues. This substitution of mechanical protection with electronic control simplifies the physical contactor structure while maintaining reliability through intelligent timing.
3Ease of operation
If the relay is closed at any time to pre-charge the bus capacitor, then the pre-charging operation is simple, but impulse current occurs which requires arc quenching devices
Solution Approach 1:
The patent implements feedback by continuously monitoring the voltage across the contactor and using this information to control the closing timing. The control unit adjusts the closing decision based on real-time voltage feedback, ensuring closure occurs only when voltage is below the threshold, thereby preventing impulse current while maintaining operational simplicity.
Solution Approach 2:
The patent replaces the need for mechanical arc quenching devices with an electronic voltage detection and control system. This electronic approach maintains the simplicity of the pre-charging operation while eliminating harmful impulse currents through intelligent timing based on voltage conditions.
Data Source
AI summary
A charging pile, a power module, and a method for controlling the same. In response to receiving a signal of operation, samples of an input voltage of three relays corresponding to three phases, respectively, at an input of a power module are acquired to determine whether a line voltage between inputs of two of the three relays is within a predetermined voltage range. The two relays are closed to pre-charge a bus capacitor in a converting circuitry of the power module, in response to determining that the line voltage is within the predetermined voltage range. The predetermined voltage range comprises zero voltage, such that each relay can be closed when a voltage at its input is close to zero. An impulse current is decreased without help of an arc quenching device, thereby saving an internal space of the charging pile.