Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

A Novel Inverter Control Strategy with Power Decoupling for Microgrid Operations in Grid-Connected and Islanded Modes

Yan Tong, Qin Wang, Aihong Tang

TL;DR

The paper tackles frequency and voltage stability in microgrids with high renewable penetration, where reduced inertia challenges grid-forming control across both grid-connected and islanded modes. It introduces the Unified Dynamic Power Coupling (UDC) model that blends droop control and Virtual Synchronous Generator (VSG) dynamics, supported by a Relative Gain Array–based coupling analysis, enabling virtual inertia in islanded operation and fast active-power tracking in grid-connected operation. Key contributions include (i) a generalized power model unifying droop and VSG behavior, (ii) a frequency-domain coupling compensation framework to harmonize multiple Distributed Generations, and (iii) design guidelines validated by simulation. The results demonstrate improved overshoot, settling time, and ROCOF performance, with decentralized control leveraging bus frequency and voltage signals, suggesting practical potential for resilient, grid-forming microgrid operation.

Abstract

Grid-forming, particularly those utilizing droop control and virtual synchronous generators (VSG), can actively regulate the frequency and voltage of microgrid systems, exhibiting dynamic characteristics akin to those of synchronous generators. Although droop control and VSG control each have distinct benefits, neither can fully meet the diverse, dynamic needs of both grid-connected (GC) and islanded (IS) modes. Additionally, the coupling between active and reactive power can negatively impact microgrids' dynamic performance and stability. To solve these problems, this paper introduces a unified dynamic power coupling (UDC) model. This model's active power control loop can be tailored to meet diverse requirements. By implementing a well-designed control loop, the system can harness the advantages of both droop control and VSG control. In islanded mode, the proposed model can provide virtual inertia and damping properties, while in grid-connected mode, the inverter's active power output can follow the changed references without significant overshoot or oscillation. Furthermore, the model incorporates coupling compensation and virtual impedance based on a relative gain array in the frequency domain to facilitate quantitative analysis of power coupling characteristics. This paper outlines a distinct design process for the unified model. Finally, the proposed control method has been validated through simulation.

A Novel Inverter Control Strategy with Power Decoupling for Microgrid Operations in Grid-Connected and Islanded Modes

TL;DR

The paper tackles frequency and voltage stability in microgrids with high renewable penetration, where reduced inertia challenges grid-forming control across both grid-connected and islanded modes. It introduces the Unified Dynamic Power Coupling (UDC) model that blends droop control and Virtual Synchronous Generator (VSG) dynamics, supported by a Relative Gain Array–based coupling analysis, enabling virtual inertia in islanded operation and fast active-power tracking in grid-connected operation. Key contributions include (i) a generalized power model unifying droop and VSG behavior, (ii) a frequency-domain coupling compensation framework to harmonize multiple Distributed Generations, and (iii) design guidelines validated by simulation. The results demonstrate improved overshoot, settling time, and ROCOF performance, with decentralized control leveraging bus frequency and voltage signals, suggesting practical potential for resilient, grid-forming microgrid operation.

Abstract

Grid-forming, particularly those utilizing droop control and virtual synchronous generators (VSG), can actively regulate the frequency and voltage of microgrid systems, exhibiting dynamic characteristics akin to those of synchronous generators. Although droop control and VSG control each have distinct benefits, neither can fully meet the diverse, dynamic needs of both grid-connected (GC) and islanded (IS) modes. Additionally, the coupling between active and reactive power can negatively impact microgrids' dynamic performance and stability. To solve these problems, this paper introduces a unified dynamic power coupling (UDC) model. This model's active power control loop can be tailored to meet diverse requirements. By implementing a well-designed control loop, the system can harness the advantages of both droop control and VSG control. In islanded mode, the proposed model can provide virtual inertia and damping properties, while in grid-connected mode, the inverter's active power output can follow the changed references without significant overshoot or oscillation. Furthermore, the model incorporates coupling compensation and virtual impedance based on a relative gain array in the frequency domain to facilitate quantitative analysis of power coupling characteristics. This paper outlines a distinct design process for the unified model. Finally, the proposed control method has been validated through simulation.
Paper Structure (8 sections, 21 equations, 6 figures, 2 tables)

This paper contains 8 sections, 21 equations, 6 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Concept of dynamic GFM control
  3. Grid Integration Modelling
  4. Droop Control
  5. Virtual Synchronous Generator
  6. Unified Droop-VSG Control Strategy
  7. Experimental Simulation and Parameter Design
  8. Conclusion

Figures (6)

  • Figure 1: Main circuit structure of a grid-forming converter.
  • Figure 2: Traditional Inverter Control Loop (a) Droop control,(b) Active power control loop of VSG.
  • Figure 3: Active power control loop of droop control with Governor
  • Figure 4: Simplified small-signal model of UDC
  • Figure 5: Simulation Results of Step Responses for VSG, UDC, and Droop Control under Step Change in Reference Power
  • ...and 1 more figures