Power Conversion System Voltage Maintenance During Interruptions
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Solution Overview
Problem
Conventional power conversion systems for system interconnection fail to maintain user load voltage during momentary power interruptions, leading to potential data loss and system state disruptions, and struggle to restore the power state between the power system and user load after interruptions.
Innovation Solution
A power conversion system with a voltage maintenance load and load disconnection switch, along with a power information detection unit, current/voltage command generation unit, converter control unit, and switch changeover control unit, which maintains user load voltage and reconnects the power system after interruptions, minimizing disruptions and burden on the interconnection switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the interconnection switch is turned off during momentary power interruption, then disconnection from the power system is achieved, but the power state changes before and after recovery which influences the power system
Solution Approach 1:
The patent introduces a delay period mechanism that waits for a predetermined time after momentary power interruption detection before turning off the interconnection switch. This preliminary waiting action allows the power system to potentially recover naturally, and only disconnects if the interruption persists, thereby reducing unnecessary disconnections and minimizing power state changes that could influence the power system
Solution Approach 2:
The patent employs feedback control by monitoring the power system state continuously and using delay period logic to determine whether to disconnect. The system feedbacks on the duration of power interruption and adjusts the interconnection switch state accordingly, ensuring disconnection only occurs when necessary and facilitating smoother power state recovery that minimizes influence on the power system
2Loss of energy
If the interconnection switch is turned off during momentary power interruption, then the switch burden is reduced, but voltage of the user load reduces during transition period
Solution Approach 1:
The patent segments the single switch into two independent switches with separate control logic. The load disconnection switch controls the parallel circuit independently, allowing it to remain closed and maintain voltage while the interconnection switch opens to reduce burden, thus resolving the contradiction between energy loss reduction and voltage stability
Solution Approach 2:
The voltage maintenance load in the parallel circuit acts as an intermediary that compensates for voltage drops during the transition period when the interconnection switch is turning off. By providing an alternative current path through the load disconnection switch, it maintains user load voltage stability while the interconnection switch burden is reduced
Data Source
AI summary
A power system and a power conversion device are interconnected via an interconnection switch. A user load is provided between the power conversion device and the interconnection switch. In parallel with the interconnection switch, a series circuit composed of a load disconnection switch and a voltage maintenance load for maintaining voltage of the user load at the time of system momentary power interruption is connected. Control is performed such that, when momentary power interruption occurs, the interconnection switch is turned off and the power system and the power conversion device are connected via the voltage maintenance load, and at the time of recovery from the momentary power interruption, the interconnection switch is turned on, further the power system and the power conversion device are connected.