Islanding Transition Voltage Control for Microgrid Stability

Solution Overview

Problem

Voltage disturbances from a larger utility grid can propagate to microgrid systems before disconnection, causing undesirable voltage fluctuations, especially when the microgrid includes sensitive electrical loads.

Innovation Solution

An electrical system with a sensing arrangement, power conversion module, and control module that measures electrical characteristics, identifies islanding conditions, and operates the power conversion module to provide a target output voltage, mitigating disturbances during disconnection by adjusting voltage at the grid interface and eventually disconnecting from the external grid.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the microgrid is disconnected from the utility grid, then the microgrid operates autonomously, but voltage disturbances propagate to the microgrid causing voltage fluctuations

Engineering Contradiction:

Improveautonomous operation capabilityVSAvoidvoltage disturbances

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary detection of voltage disturbances and pre-charges the energy storage system before disconnection occurs. The control module monitors grid voltage in advance and prepares the power conversion module to compensate for upcoming disturbances, preventing voltage fluctuations before they affect the microgrid

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The energy storage system with power conversion module acts as an intermediary buffer between the utility grid and the microgrid. During transition, this intermediary actively compensates for voltage disturbances by injecting or absorbing power, isolating the microgrid from harmful voltage fluctuations while maintaining autonomous operation capability

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the microgrid disconnects from the utility grid, then autonomous operation is achieved, but sensitive electrical loads experience voltage fluctuations

Engineering Contradiction:

Improveislanding capabilityVSAvoidvoltage stability for sensitive loads

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The control module continuously monitors voltage at the grid interface and uses feedback control to adjust the power conversion module's output. When voltage disturbances are detected, the feedback loop rapidly adjusts the energy storage system's power output to counteract disturbances, maintaining stable voltage for sensitive loads during the islanding transition

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary detection of voltage disturbances and pre-charges the energy storage system before disconnection occurs. The control module monitors grid voltage in advance and prepares the power conversion module to compensate for upcoming disturbances, preventing voltage fluctuations before they affect the microgrid

Inventive Principle:

Principle #10Preliminary action

Solution Approach 3:

The energy storage system with power conversion module acts as an intermediary buffer between the utility grid and the microgrid. During transition, this intermediary actively compensates for voltage disturbances by injecting or absorbing power, isolating the microgrid from harmful voltage fluctuations while maintaining autonomous operation capability

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10312822B2Electrical systems and methods for islanding transitions

Publication Date: 2019.06.04 S&C ELECTRIC CO

AI summary

An electrical system includes a sensing arrangement coupled to an electrical grid interface to measure an electrical characteristic of the electrical grid interface, a power conversion module having an output coupled to the electrical grid interface, and a control module coupled to the sensing arrangement and the power conversion module. The control module determines a reference value for the electrical characteristic, identifies an islanding condition based on a difference between a value for the electrical characteristic and the reference value, determines a target output value for the power conversion module based on the difference, and in response to the islanding condition, operates the power conversion module to provide the target output value for the electrical characteristic at the output. The target output value reduces the difference while a connection arrangement is being opened to achieve islanding.