Power Conversion Device Frequency Droop Control
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Solution Overview
Problem
Conventional power conversion devices experience significant variations in output voltage frequency when adjusting power output based on storage battery state of charge, leading to potential malfunctions and device shutdowns.
Innovation Solution
A power conversion device with a control unit that adjusts the frequency of output voltage by correcting a reference gain based on state-of-charge information, using a correction value that decreases with increasing charge level, to stabilize the frequency drooping characteristic and prevent excessive power loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If output power of power conversion devices is adjusted in accordance with SOC of storage battery, then power allocation is optimized and over-discharge is prevented, but frequency of output voltage varies greatly causing malfunction and device shutdown
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the droop characteristic parameter (frequency-power relationship) based on the SOC of the storage battery. When SOC is low, the droop characteristic is modified to prevent over-discharge, and when SOC is high, normal droop control is maintained. This ensures stable frequency output while optimizing power allocation according to battery state.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the SOC of the storage battery and using this information to adjust the droop characteristic of the power conversion device. The control device receives SOC information, determines the appropriate droop characteristic based on SOC levels, and adjusts the frequency-power relationship accordingly. This closed-loop feedback ensures that power output is optimized while maintaining stable frequency and preventing device malfunction.
2Power
If multiple storage batteries are connected in parallel to supply large power, then power supply capacity is increased, but power conversion efficiency decreases and loss increases
Solution Approach 1:
The patent optimizes power distribution by dynamically changing the droop characteristic parameter based on individual battery SOC levels. This allows the system to allocate power efficiently among multiple batteries, ensuring that batteries with higher SOC contribute more power while maintaining optimal conversion efficiency. The parameter adjustment prevents unnecessary energy loss by matching power output to actual battery state.
Data Source
AI summary
A control circuit corrects a reference gain by multiplying the reference gain by a correction value set in association with state-of-charge information of a storage battery, and uses the corrected reference gain as a first gain for controlling a DC/AC inverter, to adjust the slope of frequency drooping characteristic. The correction value is a value that gradually decreases with increase in state-of-charge information of the storage battery, the minimum value of the correction value is N1 which is a real number greater than 0 and corresponding to a first state of charge for stopping charging of the storage battery, and the maximum value of the correction value is N2 which is a real number greater than N1 and corresponding to a second state of charge for stopping discharging of the storage battery.