Battery Charging Control for Virtual Inertia and Grid Frequency
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Solution Overview
Problem
The transition to a higher share of distributed energy resources (DERs) and renewable energy resources in power grids reduces system inertia, leading to frequency stability issues, including faster frequency changes and potential grid instability or collapse.
Innovation Solution
A method for controlling the charging of electrical storage devices, involving an aggregator that retrieves information from the power grid and storage devices, derives a weighted distribution of virtual inertia response and fast frequency response, and communicates this to a charging controller to set active power setpoints for each device, ensuring stable grid operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional power plants with high inertia are replaced by DERs and renewable energy resources, then the share of renewable energy in the power grid is increased, but system inertia is reduced leading to frequency stability issues
Solution Approach 1:
The patent implements virtual inertia control that copies the frequency response characteristics of conventional synchronous generators using power electronic converters. The control system calculates a virtual inertia response signal based on frequency deviation and its derivative, then injects this signal through the converter to emulate the inertial behavior of traditional power plants, thereby maintaining frequency stability while enabling high renewable energy penetration.
Solution Approach 2:
The patent changes the operational parameters of power electronic converters from purely power-following mode to a mode where they actively provide virtual inertia support. By modifying the control algorithm to include frequency deviation and its rate of change, the converter's output power is dynamically adjusted to provide inertia-like response, transforming the converter from a passive component to an active stability provider.
2Adaptability or versatility
If power electronic converters are used to connect renewable energy resources to the grid, then renewable energy penetration is enabled, but the converters do not provide inertia support worsening frequency stability
Solution Approach 1:
The patent makes power electronic converters multi-functional by enabling them to simultaneously perform their primary function of connecting renewable energy sources to the grid and providing virtual inertia support. The control system integrates frequency stabilization functionality into the existing converter control architecture, allowing a single device to fulfill both power transmission and system stability roles.
Solution Approach 2:
The converter is configured to copy the inertial response behavior of conventional synchronous generators. By calculating virtual inertia signals based on frequency deviation and injecting them through the converter, the patent enables the converter to replicate the stabilizing effect of traditional inertia-providing equipment, thereby compensating for the loss of physical inertia in renewable energy systems.
3Reliability
If virtual inertia control is implemented in power electronic converters, then frequency stability is improved, but control complexity increases
Solution Approach 1:
The patent segments the virtual inertia control into distinct computational steps: calculating frequency deviation, computing its derivative with respect to time, determining the virtual inertia response signal, and injecting it through the converter. This segmentation of the control algorithm into manageable stages reduces implementation complexity while maintaining the overall frequency stabilization function.
Data Source
AI summary
A method for controlling charging of at least one electrical storage device is disclosed. Information regarding a power grid and the at least one electrical storage device is used by an aggregator to derive a weighted distribution of virtual inertia response and fast frequency response to be provided to the power grid by the electrical storage devices. A total power available for charging the at least one electrical storage device is derived in accordance with the weighted distribution by a charging controller. An active power setpoint is derived for each of the at least one electrical storage device on the basis of at least (i) the total available power and (ii) the information regarding the at least one electrical storage device. Finally, a charging state of each of the at least one electrical storage device is controlled based on the derived active power setpoint.