Multivariable Control Design for Grid-Forming Inverters With Decoupled Active and Reactive Power Loops

Rathnayake, Dayan B.; Bahrani, Behrooz

doi:10.1109/tpel.2022.3213692

Cited by 22 publications

(13 citation statements)

References 34 publications

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“…The current control reference value and the measured values of the grid-side currents I meas d,cv , I meas q,cv are obtained from the current controller by means of the inverter trigger pulses P d,cv , P q,cv . Achieving the decoupling control of active and reactive power of inverters and synchronous grid connection can be performed by integrating phase-locked loop measurement methods [27][28][29][30]. The control approach for managing energy storage in photovoltaic systems aligns with the strategy used for controlling energy storage in wind power generation systems.…”

Section: Optical Storage System Model and Controlmentioning

confidence: 99%

A Stabilization Control Strategy for Wind Energy Storage Microgrid Based on Improved Virtual Synchronous Generator

Huang,

Lin,

Sun

et al. 2024

Energies

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In high-penetration renewable-energy grid systems, conventional virtual synchronous generator (VSG) control faces a number of challenges, especially the difficulty of maintaining synchronization during grid voltage drops. This difficulty may lead to current overloads and equipment disconnections, and it has an impact on the security and reliability of the system, as well as limiting the dynamic reactive power support capability of the system. To solve this problem, in this study, a wind–solar hybrid power generation system is designed with a battery energy storage device connected on the DC side, and proposes a low voltage ride-through (LVRT) control strategy for the grid-connected inverter based on an improved VSG. The control strategy employs an integrated current limiting technique combining virtual impedance and vector current limiting to ensure that the VSG exhibits good dynamic power support characteristics during symmetrical faults by adjusting the setpoint value of reactive power. At the same time, it maintains the synchronization and power angle stability of the VSG itself to achieve the goal of LVRT. Simulation results show that the proposed control strategy can effectively suppress the renewable power fluctuations (about 30% reduction in fluctuations compared to the conventional strategy) and ensure the safe and reliable operation of the renewable energy sources and VSGs during grid-side faults. In addition, it provides a given reactive power support and stable grid voltage control (voltage dips reduced by about 20%), which significantly enhances the LVRT capability of the hybrid wind–solar-storage generation system.

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Section: Optical Storage System Model and Controlmentioning

confidence: 99%

A Stabilization Control Strategy for Wind Energy Storage Microgrid Based on Improved Virtual Synchronous Generator

Huang,

Lin,

Sun

et al. 2024

Energies

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“…In [16], authors investigated the use of impedance-based analysis to define, assess, and enhance the performance of GFM inverter controllers in various ways. In [17], a multivariable controller was proposed with the aim of decoupling P and Q loops in GFM inverters using droop control and other methods. A decentralized control approach for multiparallel GFM-distributed generators on island MG was developed in [18].…”

Section: Related Workmentioning

confidence: 99%

Design, Modeling, and Validation of Grid-Forming Inverters for Frequency Synchronization and Restoration

Bennia,

Elbouchikhi,

Harrag

et al. 2023

Energies

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This paper focuses on the modeling, analysis, and design of grid-forming (GFM) inverter-based microgrids (MGs). It starts with the development of a mathematical model for three-phase voltage source inverters (VSI). The voltage and current controllers consist of two feedback loops: an outer feedback loop of the capacitance-voltage and an inner feedback loop of the output inductance current. The outer voltage loop is employed to enhance the controller’s response time. The inner current loop is used to provide active damping for the resonance created by the LCL filter. A two-layer control scheme is adopted for the GFM inverter control. The primary decentralized control uses droop control and virtual impedance loops to share active and reactive power. Simultaneously, the centralized secondary control addresses frequency and amplitude deviations induced by the droop control. Additionally, a synchronization loop is proposed for seamless reconnection of GFM inverters to the MG and to connect the GFM-controlled MG to the main grid. It has the advantage that the inverter operates in GFM mode even after the synchronization has occurred. The simulation results have shown that the voltage controller ensures a 0.005 s settling time and maintains the steady-state error at its minimum value of 0.1 V. Similarly, the current controller ensures a 0.006 s settling time with a 10−5 steady-state error. The system with the designed controller has a low total harmonic distortion (THD) of 1.46% and improved power quality of the output voltage. Furthermore, a quick restoration time is observed during load steps and tripping events, with a restoration time of 1 s with 10−10 steady-state error. Synchronization is achieved within 0.8 s for the incoming inverters and requires 3 s to synchronize the MG with the main grid, maintaining a steady-state error of 10−9.

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“…In addition to these conventional droop and VSG methods, several other approaches have been proposed for GFMIs, primarily designed using nonlinear control techniques. Virtual oscillator control (VOC) [22], [23], H ∞ -based methods [24], [25], and Virtual Synchronous control utilizing dclink capacitor dynamics [26] are examples of other popular control techniques. However, in this paper, focus is placed on the most widely used methods for GFMIs, which are the frequency-based droop method and VSG-based methods, as they exhibit promising features and can be considered wellestablished control techniques [27].…”

Section: Introductionmentioning

confidence: 99%

Grid-Forming Inverters: A Comparative Study of Different Control Strategies in Frequency and Time Domains

Mohammed,

Udawatte,

Zhou

et al. 2024

IEEE Open J. Ind. Electron. Soc.

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Grid-forming inverters (GFMIs) are anticipated to play a leading role in future power systems. In contrast to their counterpart grid-following inverters, which employ phase-locked loops for synchronization with the grid voltage and rely on stable grid connections, GFMIs primarily employ the power-based synchronization concept to form the voltage. Hence, they can not only stably operate in regions of the grid characterized by low strength but also provide critical ancillary services to power systems, including voltage, frequency and inertia support. Several control strategies have been employed for GFMIs, making it crucial to comprehend their stability characteristics for the analysis of small-signal stability and low-frequency oscillations. This article examines the performance of GFMIs when equipped with four different control strategies, namely: droopbased GFMI, virtual synchronous generator (VSG)-based GFMI, compensated generalized VSG (CGVSG)based GFMI, and adaptive VSG (AVSG)-based GFMI. The comparative analysis assesses the performance and robustness of these four control strategies across various operational scenarios in frequency and time domains. Initially, the impedance-based stability analysis method is employed to evaluate these control strategies across different case studies in terms of grid strengths, grid impedance ratios, the dynamics with/without virtual impedance and inner voltage and current loops, and variations in the inverter's operating points. Subsequently, time domain verification using the electromagnetic transient models are conducted for these case studies as well as to assess the power tracking capability of these control strategies in response to changes in power references. Finally, the robustness of these four controllers is explored against external grid disturbances, including grid frequency deviations, phase jumps, and voltage sags, considering varying levels of disturbance magnitudes in both weak and strong grid connections. In conclusion, the evaluation of these control techniques in various operational scenarios reveals their strengths and weaknesses, offering valuable guidance for the selection of the most appropriate control technique to suit desired practical applications.

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Multivariable Control Design for Grid-Forming Inverters With Decoupled Active and Reactive Power Loops

Cited by 22 publications

References 34 publications

A Stabilization Control Strategy for Wind Energy Storage Microgrid Based on Improved Virtual Synchronous Generator

A Stabilization Control Strategy for Wind Energy Storage Microgrid Based on Improved Virtual Synchronous Generator

Design, Modeling, and Validation of Grid-Forming Inverters for Frequency Synchronization and Restoration

Grid-Forming Inverters: A Comparative Study of Different Control Strategies in Frequency and Time Domains

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