Grid-Connected Power Storage Control for Frequency Deviation Restraint
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Solution Overview
Problem
Existing power compensation devices may destabilize the grid frequency by outputting active power in a direction that moves the grid frequency away from the reference value, particularly when the grid frequency abruptly changes.
Innovation Solution
A power storage system interconnected to a power grid, comprising a power storage device, a power converter, and a control device. The control device includes a frequency detector, a frequency variation amount calculator, a control calculator, and a restriction unit to generate a command value for active power output or input based on frequency variation, and restricts active power operations to prevent deviation of the grid frequency from the reference value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power compensation device outputs active power to suppress frequency variation, then the frequency variation component is compensated, but the grid frequency may move away from the reference value causing destabilization
Solution Approach 1:
The control device continuously monitors the grid frequency and compares it with the reference value, using the frequency difference as feedback to adjust active power output. This closed-loop control ensures that frequency correction actions do not overshoot and maintain stability around the reference value.
Solution Approach 2:
The control device dynamically adjusts the active power output based on real-time frequency conditions. When frequency deviates from the reference value, the device modifies its output to bring frequency back to reference, and when frequency approaches reference, it reduces output to prevent overshooting, creating a dynamic response that maintains stability.
2Productivity
If the active power command value is calculated by multiplication of frequency difference by gain, then the frequency variation component is compensated, but the control output may vary frequency in wrong direction
Solution Approach 1:
The control device applies partial action by adjusting active power output only to the extent needed to correct frequency deviation, not fully compensating every variation. This prevents excessive correction that would cause frequency to overshoot and move in the wrong direction, maintaining control accuracy.
Solution Approach 2:
The control device anticipates potential frequency overshooting by applying preliminary restraint to the active power output. When frequency approaches the reference value, the device reduces power output in advance to prevent crossing the reference value, thereby maintaining frequency control accuracy.
Data Source
AI summary
A power converter interchanges electric power between a power storage device and a power grid as the power storage device is charged and discharged. A control device controls active power inputted and outputted between the power grid and the power converter. The control device generates a command value indicating an amount of output of active power for increase in grid frequency or an amount of input of active power for lowering in grid frequency, in accordance with an amount of frequency variation calculated from a frequency detection value of the power grid. Furthermore, the control device restricts output of active power in accordance with the command value when the frequency detection value is larger than a frequency reference value of the power grid and restricts input of active power in accordance with the command value when the frequency detection value is smaller than the frequency reference value.