Hierarchical Microgrid Control for Seamless On-Off Grid Transitions
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Solution Overview
Problem
Existing microgrid control systems struggle to maintain stability and balance when integrated with multiple production sources of different types, especially when existing components have unknown or non-modifiable adjustment characteristics, limited operating modes, or lack communication with the microgrid controller, leading to instability and inability to adapt to changes in power generation and distribution.
Innovation Solution
A multi-level, integrated microgrid control system with adjustable operating modes and software algorithms for power conversion systems and a microgrid controller that predicts load and renewable energy production, calculates spinning reserves, and dynamically allocates balance nodes to ensure stability, allowing for seamless transitions between on-grid and off-grid operations without voltage dips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuel-operated generators are used to compensate for power variations, then power balance can be partially maintained, but response time is slow and operating range is limited
Solution Approach 1:
The patent combines multiple balance nodes (fuel-operated generators, accumulation systems, and inverters) to work together in a coordinated manner. This merging allows the system to leverage the power balance capability of fuel-operated generators while compensating for their slow response time through the addition of faster-responding accumulation systems and inverters, thereby achieving both reliable power balance and fast response.
Solution Approach 2:
The system dynamically adjusts the operating mode and control parameters of fuel-operated generators based on real-time grid conditions. The microgrid controller continuously monitors power balance status and modifies generator set points, enabling them to operate more responsively within their technical limits while maintaining reliability.
2Adaptability or versatility
If multiple balance nodes are used, then system flexibility and safety increase, but device complexity increases
Solution Approach 1:
The control system is segmented into hierarchical levels with a microgrid controller managing overall coordination and individual balance node controllers handling local control. This segmentation allows multiple balance nodes to operate independently with standardized interfaces, increasing system flexibility while managing complexity through modular architecture and clear division of control responsibilities.
Solution Approach 2:
The microgrid controller implements universal control algorithms that can manage multiple types of balance nodes (generators, accumulation systems, inverters) through standardized protocols. This multi-functionality allows the same control system to handle diverse components, increasing adaptability while reducing the need for component-specific control logic, thereby managing complexity.
3Adaptability or versatility
If existing components with unknown adjustment characteristics are integrated, then system compatibility improves, but control precision deteriorates
Solution Approach 1:
The microgrid controller continuously monitors the actual performance of integrated components and uses feedback to dynamically adjust control parameters and set points. This real-time feedback mechanism compensates for unknown adjustment characteristics of existing components, maintaining control precision by adapting to actual component behavior rather than relying on predetermined parameters.
Solution Approach 2:
The system dynamically changes control parameters (such as droop characteristics, power set points, and response coefficients) based on real-time measurements of component performance. This parameter adaptation allows the controller to optimize control precision for each component regardless of its unknown initial characteristics, while maintaining compatibility through flexible parameter adjustment.
Data Source
AI summary
It is described a control system for a microgrid for the production and distribution of electric power coming from multiple electric power sources of the intermittent and/or random and/or programmable and/or accumulation-system type,said microgrid control system being organized with a hierarchical control structure on two levels, comprising a first control level for power conversion systems (PCS) of electric power coming from said multiple electric power sources, a second control level for a microgrid controller (MC) adapted to cooperate with said first control level, said second control level being adapted to control electric power to be supplied to a distribution network (on-grid condition) and/or to be supplied as the primary generation to power up isolated loads (off-grid condition) and/or to control intelligent distributed electric power accumulation systems (ACC),said second control level for the microgrid controller (MC) comprising:a monitoring system (MON), adapted to interface with physical signals generated by said control system, and to perform operations on said power conversion systems (PCS) and on said microgrid;a control function (FC) system, adapted to receive, at the inputs, measurements and states of the control system and to provide, at the output, parameters and set points through which said monitoring system (MON) acts on said power conversion systems (PCS), so as to manage the power flows of the microgrid;a state machine (MAS), adapted to cooperate with said monitoring system (MON) and said control functions (FC), so as to control the operating conditions of the microgrid and decide, based on said conditions, which control functions (FC) are to be enabled;said first control level (CPCS) of power conversion systems (PCS) being adapted to control the values of voltage (V), frequency (f), active power (P) and reactive power (Q) generated by said microgrid, and comprising:a droop control system under said on-grid condition, adapted to act on the values of said active and reactive power (P0 and Q0), keeping them at set-point values (Pref and Qref), by increasing or decreasing frequency and voltage, respectively, based on first droop curves;a droop control system under said off-grid condition, adapted to act on the values of said voltage (V) and frequency (f), keeping them at set-point values (fref and Vref), based on second droop curves.