Grid Side Converter Microgrid Synchronization Control

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Solution Overview

Problem

Conventional microgrid control systems fail to ensure smooth transition between microgrids and utility grids, leading to instability, and existing methods for voltage imbalance mitigation and synchronization are economically infeasible and inefficient.

Innovation Solution

A method and system for synchronizing utility grids and microgrids using a grid side converter, diesel generators, wind turbines, and photovoltaic arrays, which control voltage, frequency, and phase angle to match utility grid parameters, and employ a switched capacitor bank for resynchronization, enabling efficient power management and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional microgrid control systems are used for transition between grid-connected and island modes, then the system operates with existing control mechanisms, but the transition causes voltage and frequency fluctuations leading to instability and equipment damage

Engineering Contradiction:

Improvemicrogrid stabilityVSAvoidvoltage and frequency fluctuations

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control system performs preliminary synchronization of voltage, frequency, and phase angle before reconnecting the microgrid to the utility grid. The grid side converter adjusts microgrid parameters in advance to match utility grid parameters, ensuring smooth transition and avoiding harmful fluctuations during mode switching

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control system continuously monitors voltage, frequency, and phase angle differences between the microgrid and utility grid, using feedback signals to dynamically adjust the grid side converter operations. This closed-loop control ensures parameters remain synchronized during transition, preventing instability and equipment damage

Inventive Principle:

Principle #23Feedback

2Reliability

If dedicated components such as SVCs, STATCOMs, and automatic load tap changing transformers are used for voltage regulation, then voltage control capability is improved, but the system cost increases significantly making it economically infeasible

Engineering Contradiction:

Improvevoltage control capabilityVSAvoidsystem cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The grid side converter is designed to perform multiple functions including voltage control, frequency regulation, and reactive power compensation. This multi-functional approach replaces the need for dedicated voltage regulation components like SVCs and STATCOMs, achieving the same voltage control capability at lower system cost

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines voltage control, frequency control, and reactive power management functions into a single integrated control system operating through the grid side converter. This consolidation eliminates the need for separate dedicated components, reducing overall system complexity and cost while maintaining effective voltage regulation

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If two coordinated circuit breakers are employed for microgrid resynchronization to the utility grid, then synchronization control is achieved, but the equipment cost and system complexity increase

Engineering Contradiction:

Improvesynchronization controlVSAvoidequipment cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The grid side converter acts as an intermediary device between the microgrid and utility grid, providing continuous voltage and frequency control during the synchronization process. This eliminates the need for complex coordinated circuit breaker systems, as the converter maintains parameter matching that enables safe reconnection with simpler protection equipment

Inventive Principle:

Principle #24Intermediary (Mediator)

4Adaptability or versatility

If the microgrid operates in island mode with power imbalance, then the microgrid can function independently, but the system experiences disturbance and loses synchronism with the utility grid

Engineering Contradiction:

Improveindependent operation capabilityVSAvoidsynchronism maintenance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The control system dynamically adjusts the grid side converter operations based on the operating mode. During island mode, it maintains independent operation; during resynchronization, it dynamically modifies voltage, frequency, and phase angle to match the utility grid, ensuring continuous synchronism while preserving adaptability across different operational states

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11451065B1Voltage control and grid synchronization of microgrids in real time

Publication Date: 2022.09.20 KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS

AI summary

A system and method for synchronizing a utility grid and a microgrid including a diesel generator, a photovoltaic array and a wind turbine. In a grid connected mode, a microgrid voltage, a microgrid frequency and a microgrid phase angle are controlled by a grid side converter which generates a preset reference power at the utility grid frequency; and provides a real power and a reactive power to each of a plurality of loads. In an island mode, the diesel generator operates at a constant speed to generate power at the reference frequency and communicates the reference frequency to a wind turbine, and the microgrid supplies the real power and reactive power to each of the plurality of loads. In a resynchronization mode, a switched capacitor bank is charged to provide the voltage needed to reconnect the microgrid to the utility grid.