Distributed Load Control for Microgrid Frequency Stability

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Solution Overview

Problem

Traditional control systems for electric power grids, particularly microgrids, face challenges in maintaining operational flexibility due to assumptions of static system conditions, leading to inefficiencies in voltage and frequency regulation, especially during dynamic changes and islanded operations without a strong substation voltage source.

Innovation Solution

Implementing a distributed control architecture that utilizes load controllers to monitor and adaptively adjust power supply based on real-time parameters like frequency and voltage, employing grid-forming inverters for primary frequency response and shedding loads quickly to maintain system stability, with setpoints determined using the incomplete beta function to optimize reserve power utilization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional control systems with static assumptions are used, then device complexity is reduced, but adaptability deteriorates due to inability to respond to dynamic changes and reverse power flow

Engineering Contradiction:

Improveadaptability to dynamic system changesVSAvoidcontrol system complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The control system is divided into multiple distributed load controllers, each independently managing local loads. This segmentation allows the system to adapt to dynamic changes through localized decisions without requiring complex centralized control, resolving the contradiction between adaptability and complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control system transitions from static assumptions to dynamic response by continuously monitoring system frequency and adapting load control strategies in real-time. This dynamic approach enables the system to respond to changing conditions while maintaining manageable complexity through standardized control algorithms.

Inventive Principle:

Principle #15Dynamics

2Reliability

If load shedding is used to maintain frequency stability, then frequency stability is improved, but productivity deteriorates due to loss of power supply

Engineering Contradiction:

Improvefrequency stabilityVSAvoidpower supply continuity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system implements partial load shedding by selectively controlling individual loads rather than complete system shutdown. This allows maintaining frequency stability while preserving power supply to critical loads, thus balancing reliability requirements with productivity maintenance.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

Different loads are assigned different control characteristics and setpoints based on their criticality and power consumption patterns. This local differentiation allows the system to maintain frequency stability through targeted load reduction while minimizing impact on overall productivity by preserving supply to essential loads.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If distributed control architecture is implemented, then adaptability is improved, but device complexity increases due to multiple controllers

Engineering Contradiction:

Improveoperational flexibilityVSAvoidnumber of controllers

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Each load controller is designed as a universal, multi-functional unit that can manage multiple loads with different characteristics using standardized algorithms. This universality reduces the effective complexity by eliminating the need for highly specialized controllers for each specific load type, while still providing the adaptability of distributed control.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Speed

If fast load shedding is implemented, then frequency response speed is improved, but loss of energy increases due to abrupt load disconnection

Engineering Contradiction:

Improvefrequency response speedVSAvoidenergy waste from abrupt disconnection

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The control system pre-configures load control strategies and setpoints based on system conditions and load characteristics. This preliminary preparation enables rapid response to frequency deviations without the need for abrupt, energy-wasting disconnections, as the system can smoothly transition loads based on pre-planned control sequences.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20230307909A1Electric Power Systems, Control Systems and Associated Operational Methods

Publication Date: 2023.09.28 BATTELLE MEMORIAL INST

AI summary

Electric power systems, control systems and associated operational methods are described. According to one aspect, an electric power system includes plural load controllers that are configured to control the supply of electrical energy from the system to plural loads, a control system that determines an amount of power in reserve and available to be provided to the electric power system, uses the determined amount of power in reserve to determine different values for a plurality of setpoints that correspond to a parameter of electrical energy that is supplied by the system to the loads, and the load controllers monitor the parameter of the electrical energy that is supplied by the system with respect to the setpoint values and to adjust an amount of the electrical energy that is supplied from the electric power system to the loads as a result of the monitoring of the parameter by the load controllers.