Power Control Device Self-Sustaining Operation Safety
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Solution Overview
Problem
Existing power control devices face challenges in reliably disconnecting from a power system during self-sustaining operations, potentially causing safety issues due to reverse power flow and voltage abnormalities, and fail to supply electric power to connected loads during power failures.
Innovation Solution
A power control device with an inverter, a control unit, and a disconnection relay that ensures safe self-sustaining operation by detecting voltage and current absence, breaker open state, and power system disconnection before initiating self-sustaining power supply to loads, and reconnects only when safe conditions are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power conversion device performs self-sustaining operation when abnormality occurs in the power system, then the power supply to power loads can be maintained during power failure, but the device may fail to disconnect reliably from the power system due to complex configuration and abnormality detection limitations
Solution Approach 1:
The control unit performs preliminary detection of voltage and current before initiating self-sustaining operation. The voltage detection unit detects voltage from the power system, and the current detection unit detects current flowing between the power conversion device and the power system. Only when both voltage and current are detected as absent does the control unit permit transition to self-sustaining operation, ensuring safe disconnection before operation begins.
Solution Approach 2:
The control unit continuously monitors voltage and current during self-sustaining operation through the voltage detection unit and current detection unit. When voltage or current is detected during operation, the control unit immediately stops the self-sustaining operation and reconnects to the power system, providing real-time feedback control to maintain safety.
2Extent of automation
If the power conversion device switches operation mode based on detected frequency and voltage range, then operation can be automated, but reliable disconnection during self-sustaining operation cannot be ensured due to insufficient detection conditions
Solution Approach 1:
The control unit performs preliminary detection of voltage and current before initiating self-sustaining operation. The voltage detection unit detects voltage from the power system, and the current detection unit detects current flowing between the power conversion device and the power system. Only when both voltage and current are detected as absent does the control unit permit transition to self-sustaining operation, ensuring safe disconnection before operation begins.
Solution Approach 2:
The control unit continuously monitors voltage and current during self-sustaining operation through the voltage detection unit and current detection unit. When voltage or current is detected during operation, the control unit immediately stops the self-sustaining operation and reconnects to the power system, providing real-time feedback control to maintain safety.
3Reliability
If the breaker is opened to disconnect the power load from the power system, then physical disconnection is achieved, but the power conversion device may remain connected to the power system causing safety issues
Solution Approach 1:
The control unit takes in a contact signal indicating the open/close state of the breaker. During self-sustaining operation, the control unit verifies that the breaker is in the open state through this contact signal. The control unit continuously monitors the breaker state and will stop self-sustaining operation if the breaker closes, ensuring coordinated disconnection of both the power load and the power conversion device from the power system.
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
Ensures safe and reliable self-sustaining operation by preventing reverse power flow and voltage abnormalities, ensuring power is only supplied when conditions are met, and disconnecting from the power system during unsafe states.
Implementation Method 1
a voltage detector that detects voltage at the power system side of a circuit to be disconnected by the disconnection relay
Implementation Method 2
a current detector that detects current flowing between the power system and the power conversion device
Implementation Method 3
an inverter that converts DC (Direct-Current) power supplied from outside into AC (Alternating-Current) power
Data Source
AI summary
A power control device is provided which can execute self-sustaining operation only when conditions for allowing the self-sustaining operation are satisfied reliably, so as to supply AC power to a power load connected with a power system before the self-sustaining operation.In a case where an instruction to change the power control device into the self-sustaining operation state is accepted, the inverter is connected with the loads by the disconnection relay and the self-sustaining operation is started when voltage to be applied to a wiring portion between the disconnection relay and the earth leakage breaker is not detected, when current flowing between the main breaker and the power system is not detected and when a contact signal indicative of the open/close state of the main breaker indicates an open state. Moreover, the inverter is disconnected from the power system by the disconnection relay and the self-sustaining operation is stopped when the power control device is in the self-sustaining operation state in addition to that current flowing to or from the power system is detected or to that a contact signal indicative of the open/close state of the main breaker indicates a close state.