Stability in Isolated Grids: Implementation and Analysis of the Dead-Zone Virtual Oscillator Control in Simulink and Typhoon HIL

TL;DR

The paper addresses stability of isolated grids with high inverter-based resource penetration and reduced inertia. It analyzes and implements Dead-Zone Virtual Oscillator Control with a Voltage Recovery Loop (VRL) in three-phase battery inverters and PV-inverter systems; analysis includes stability of DZVOC and multiple inverters, and integration with PV via PV-grid-following mode. Key contributions include the DZVOC design with VRL, stability insights from RLC modeling and eigenvalue analysis (e.g., $\lambda = -7.3 \pm j\,100\pi$), and demonstration in MATLAB/Simulink and Typhoon HIL with 8 kW and 5 kW micro-grid cases, including fault ride-through scenarios. Findings indicate near-instantaneous response, inherent accurate power sharing among parallel VOCs, and seamless interaction with PV in grid-following operation; VRL improves voltage regulation though tuning/coordination is needed during anomalies. Practical impact includes enabling scalable, fast-responding grid-forming inverters for next-generation micro-grids and PV+battery deployments.

Abstract

This paper explores the analysis and implementation of the Virtual Oscillator Control (VOC) strategy for inverters aiming to enhance stability amidst the ever-increasing generation of renewable energy sources like solar PV. Key objectives include implementation and analysis of a Dead-Zone VOC (DZVOC) three-phase battery-inverter system with an additional voltage control loop, study of its stability and performance in an isolated micro-grid and exploration of their use alongside widely used grid following PV-inverter system. By modeling independent microgrids under various cases with scenarios: VOC inverters of varying capacities and VOC inverters in conjunction with PV inverters, this research addresses critical aspects of power-sharing, compatibility, response times, and fault ride-through potential, as well as improving the voltage droop profile of a general DZVOC control. The simulation is executed in MATLAB SIMULINK and validated with real-time simulation using the Typhoon-HIL 404.

Figures (13)

• Figure 1: Circuit Model of Dead Zone Oscillator
• Figure 2: Impulse response of the oscillator circuit considering different parts of the dead-zone piece-wise function ($f(V_{osc})$): (a): $V_{osc} > \psi$, (b): $|V_{osc}| \le \psi$, (c): $V_{osc} < -\psi$, (d): $f(V_{osc})$ wholly.
• Figure 3: Voltage Recovery Loop (VRL)
• Figure 4: Standalone three-phase grid with differently sized inverter-based sources.
• Figure 5: A battery-inverter system, with VOC, supplying a common load in parallel with a PV-inverter system, with hysteresis current control.