Power Converter Reverse Flow Suppression via Diode Contactor
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Solution Overview
Problem
Existing power conversion devices face challenges in suppressing reverse power flow into direct current power supplies during reactive power compensation, leading to inefficiencies and potential damage, particularly when using large and expensive configurations like air circuit breakers or simple electromagnetic contactors, which may cause part damage or reliability issues.
Innovation Solution
A power conversion device comprising a power converter, direct current capacitor, voltage sensor, rectifying element, and electromagnetic contactor, where the control circuit engages or opens the contactor based on detected voltage levels to prevent reverse power flow, using a diode and electromagnetic contactor in parallel to manage power flow effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-pressure air circuit breaker or electromagnetic contactor with arc chute is used to suppress reverse power flow, then reverse power flow is effectively suppressed, but the device becomes large and expensive
Solution Approach 1:
The patent combines the rectifying element (diode) and electromagnetic contactor into a single integrated configuration. The diode is placed in parallel with the contactor, creating a unified power flow control system that leverages the blocking capability of the diode and the switching capability of the contactor, thereby achieving effective reverse power flow suppression without requiring separate complex protection devices.
Solution Approach 2:
The rectifying element (diode) acts as an intermediary component that naturally blocks reverse current flow through its inherent electrical properties. By positioning the diode in parallel with the contactor, the system uses this passive component to handle the reverse power flow suppression function, allowing the contactor to focus on normal power switching and reducing the overall system complexity.
2Device complexity
If a simple electromagnetic contactor is used to suppress reverse power flow, then device size and cost are reduced, but part damage may occur when opening in the state of direct current flow
Solution Approach 1:
The rectifying element (diode) is positioned to preemptively block reverse current flow before it can reach the electromagnetic contactor. This preliminary protective action prevents direct current from flowing in reverse through the contactor, eliminating the risk of part damage when the contactor opens and avoiding reliability issues associated with DC arcing.
3Reliability
If a diode is inserted in the direct current input to suppress reverse power flow, then reverse power flow is suppressed, but wasteful power consumption increases due to forward voltage drop
Solution Approach 1:
The system dynamically switches between two operational modes using the control circuit: (1) During normal power generation, the electromagnetic contactor is engaged to provide a low-impedance path for forward current, minimizing power losses. (2) During reactive power compensation when reverse flow might occur, the contactor opens and the diode takes over, blocking reverse current. This dynamic switching optimizes energy efficiency in each operational state.
Solution Approach 2:
The rectifying element (diode) is not continuously engaged but only activated when needed for reverse power flow suppression. By using the diode selectively during reactive power compensation mode rather than continuously, the system minimizes the impact of forward voltage drop losses while still providing effective reverse flow protection when required.
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 effectively suppresses reverse power flow into the direct current power supply while maintaining efficiency and reliability, avoiding the drawbacks of previous methods by using a simple and reliable setup that minimizes wasteful power consumption and reduces the need for cooling mechanisms.
Implementation Method 1
The rectifying element is provided between the direct current capacitor and the direct current power supply and suppresses a reverse flow of electrical power from the power converter and the direct current capacitor into the direct current power supply
Implementation Method 2
The electromagnetic contactor is connected in parallel with the rectifying element. The control circuit controls operations of the power converter and the electromagnetic contactor
Data Source
AI summary
According to an embodiment of the invention, a power conversion device that includes a power converter, a direct current capacitor, a voltage sensor, a rectifying element, an electromagnetic contactor, and a control circuit is provided. The power converter includes a pair of direct current terminals connected to a direct current power supply, includes multiple alternating current terminals connected to an electric power system of alternating current, converts direct current power input from the direct current power supply into alternating current power, and supplies the alternating current power to the electric power system. The direct current capacitor is connected between the pair of direct current terminals. The voltage sensor detects a voltage value of the direct current capacitor. The rectifying element is provided between the direct current capacitor and the direct current power supply and suppresses a reverse flow of electrical power from the power converter and the direct current capacitor into the direct current power supply. The electromagnetic contactor is connected in parallel with the rectifying element. The control circuit controls operations of the power converter and the electromagnetic contactor. In the case where the voltage value of the direct current capacitor detected by the voltage sensor is a prescribed value or more, the control circuit engages the electromagnetic contactor and supplies active power from the power converter to the electric power system; and in the case where the voltage value of the direct current capacitor detected by the voltage sensor is less than the prescribed value, the control circuit opens the electromagnetic contactor and supplies a reactive power from the power converter to the electric power system.