Grid-Forming Energy Storage Control for Weak-Grid PCC Stability
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Solution Overview
Problem
Conventional grid-following control modes in power systems with weak inertia and low physical strength face challenges in maintaining stability due to the lack of effective coordination of active and reactive power among multiple energy storage apparatuses, especially in systems with renewable energy and power electronic devices.
Innovation Solution
A grid-forming energy storage system with a control method that monitors frequency and voltage at the point of common coupling (PCC), determines active and reactive power additional values for each energy storage apparatus, and employs cooperative control strategies to distribute power outputs based on active and reactive power surge ratios, using droop control to stabilize frequency and voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grid-following control mode is used, then synchronization with power grid is achieved, but stability in weak power grid deteriorates
Solution Approach 1:
The patent inverts the conventional control approach by switching from grid-following mode (which tracks grid parameters) to grid-forming mode (which establishes grid parameters). The virtual synchronous generator technology enables energy storage apparatus to generate voltage and frequency references, effectively inverting the traditional master-slave relationship between grid and converter, thereby improving stability in weak grids.
Solution Approach 2:
The patent changes key operating parameters by implementing virtual synchronous generator control with adjustable inertia constants and damping coefficients. This allows the energy storage system to dynamically adjust its response characteristics to match grid conditions, transforming the fixed grid-following behavior into adaptive grid-forming behavior that enhances stability.
2Power
If virtual synchronous generator strategy is used, then inertia support and rapid power adjustment are provided, but coordination of multiple energy storage apparatuses deteriorates
Solution Approach 1:
The patent implements a centralized coordination system that collects real-time operating data from multiple energy storage apparatuses equipped with virtual synchronous generator functions. The coordination system processes this feedback information and generates optimized power dispatch commands, ensuring that individual apparatus actions are harmonized to maintain overall system stability and prevent conflicting operations.
Solution Approach 2:
The patent introduces a centralized coordination system as an intermediary between multiple energy storage apparatuses. This mediator receives power adjustment requests, evaluates system conditions, and distributes coordinated commands to individual apparatuses, thereby simplifying the complex interactions between multiple virtual synchronous generators and ensuring unified system behavior.
3Speed
If multiple energy storage apparatuses operate independently, then rapid local response is achieved, but frequency and voltage stability at PCC deteriorates
Solution Approach 1:
The patent merges the independent control functions of multiple energy storage apparatuses into a unified coordinated control system. While each apparatus maintains its virtual synchronous generator capability for rapid local response, the centralized coordination system combines their outputs through power distribution scheduling, ensuring that their collective action maintains frequency and voltage stability at the point of common coupling rather than causing instability through uncoordinated responses.
Data Source
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AI summary
The present application provides a grid-forming energy storage system and a control method therefor. The control method comprises: monitoring the frequency and voltage at a point of common coupling (PCC), and when the frequency and/or the voltage at the PCC exceeds a limit, determining, according to changes in active and reactive power of a system, additional values of active and reactive power of each grid-forming energy storage device connected to a grid by means of the PCC; then, correspondingly layering the additional values of the active and reactive power of each grid-forming energy storage device and response values of the active and reactive power thereof, respectively, to serve as power instruction values for active and reactive power control of each grid-forming energy storage device; further, on the basis that each grid-forming energy storage device is capable of responding to a frequency and voltage disturbance in a local range of the grid-forming energy storage device, from the perspective of the system, by sending the additional values of the active and reactive power, layering a response required for the frequency and/or voltage disturbance at the PCC onto each grid-forming energy storage device, thus further ensuring the stability of the frequency and the voltage at the PCC.