Decentralized Inverter V-F Control for Islanded Microgrid Overload
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Solution Overview
Problem
Existing technologies face challenges in islanded microgrids due to insufficient Distributed Energy Resource (DER) supply capacity, leading to improper load sharing, direct current side instability, and large voltage and frequency deviations, which can result in unnecessary load shedding.
Innovation Solution
A decentralized and coordinated V-f control framework is provided, incorporating a power regulator and a voltage-frequency regulator to generate supplementary signals for controlling grid-forming inverters, adjusting their output frequency and voltage to mitigate overload conditions and droop conditions while maintaining power within static limits, and leveraging load sensitivity for demand control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DER supply capacity is increased to meet load demand, then voltage and frequency stability is improved, but system complexity and cost increase
Solution Approach 1:
The control framework enables inverters to autonomously regulate their own output based on real-time capacity constraints and system conditions. Each inverter independently detects overload and droop conditions, generates appropriate control signals, and adjusts its operation without requiring external control or communication infrastructure, thereby maintaining stability while avoiding added system complexity
Solution Approach 2:
The system dynamically adjusts inverter output parameters (active power, reactive power, frequency, voltage) based on real-time operating conditions. By changing these parameters in response to detected conditions, the framework maintains voltage and frequency stability within acceptable ranges while adapting to varying DER capacity and load demands
2Productivity
If inverter output is increased to meet load demand, then productivity is improved, but overload conditions cause instability and load shedding
Solution Approach 1:
The control framework implements continuous monitoring of inverter output power, frequency, and voltage. When overload conditions are detected (output power exceeding capacity or frequency/voltage deviating from acceptable ranges), the system generates feedback control signals that automatically reduce inverter output to restore stable operation, preventing load shedding
Solution Approach 2:
The system dynamically adjusts inverter operating parameters based on real-time conditions. The control framework continuously modifies output power, frequency, and voltage in response to changing load demands and DER capacity, enabling the system to operate at maximum productivity while maintaining stability through adaptive control
3Reliability
If inverter output is reduced to prevent overload, then system stability is maintained, but load shedding occurs
Solution Approach 1:
The control framework applies partial control actions by adjusting only the necessary inverter parameters to resolve detected conditions. Rather than reducing output to zero or triggering immediate load shedding, the system applies just enough control signal to restore frequency and voltage within acceptable ranges, maintaining both stability and continued power delivery
4Ease of operation
If communication between inverters is implemented for coordinated control, then load sharing is improved, but device complexity and cost increase
Solution Approach 1:
Each inverter independently detects system conditions (frequency, voltage, overload) and autonomously generates appropriate control signals based on its own operating parameters and the detected conditions. This self-service approach achieves coordinated load sharing without requiring communication infrastructure between inverters
Solution Approach 2:
The control framework achieves load sharing by having each inverter adjust its output parameters (active power, reactive power, frequency, voltage) based on real-time system conditions detected locally. This parameter-based coordination eliminates the need for communication while maintaining proper load distribution
Data Source
AI summary
In examples, provided are decentralized control methods and apparatus for controlling an output of an inverter. Also provided are decentralized control methods and apparatus for controlling demand in islanded microgrids operating with an insufficient distributed energy resource system (DER) power supply. The provided control methods and apparatus can include a power regulator and a voltage-frequency regulator configured to generate supplementary inputs to control the inverter. The power regulator can control an output of the inverter according to a real-time capacity constraint of the DER. The voltage-frequency regulator can control the output of the inverter in a manner that mitigates a voltage-frequency deviation, such as by leveraging load sensitivity.