A Grid-Forming Multi-Port Converter using Unified Virtual Oscillator Control

Awal, MA; Bipu, Rashed Hassan; Chen, Siyuan; Khan, Mehnaz Akhter; Yu, Wensong; Husain, Iqbal

doi:10.1109/ecce44975.2020.9236087

Cited by 10 publications

(7 citation statements)

References 10 publications

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“…Thus, it does not require any quasi steady-state or phasor approximation. In [81], uVOC is used in implementation of a multi-port converter (MPC) consisting of a grid forming port, a DC port, and a splitphase-AC port which can be used as building blocks in hybrid AC-DC systems such as community microgrids enabling intracommunity and inter-community energy sharing. [82] investigated a double synchronous uVOC for grid-forming voltage source converters to achieve synchronization to the fundamen-FIGURE 7 A three-phase inverter with the uVOC [16] tal frequency positive-and negative-sequence components of unbalanced or distorted grids.…”

Section: Unified Virtual Oscillatormentioning

confidence: 99%

Virtual oscillator‐based methods for grid‐forming inverter control: A review

Aghdam

Agamy

2022

IET Renewable Power Gen

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In inverter‐dominant power systems, grid‐forming (GFM) inverters regulate voltage and frequency. To construct GFM inverters, conventionally, various control methods based on synchronous machine emulation or droop characteristics have been employed. However, recently, inverters are regulated by Virtual Oscillator Control (VOC) to emulate the dynamics of a weakly nonlinear oscillators. In contrast to droop control, VOC is a time‐domain controller that enables interconnected inverters to stabilize arbitrary initial conditions to a synchronized sinusoidal limit cycle rapidly. The fast synchronization, accurate power sharing in grid‐connected and islanded modes, simple and robust implementation make it a promising candidate for inverter‐dominant power systems. Moreover, VOC removes the computational burden within machine emulation‐based methods and provides an approach to measure the frequency without employing phase‐locked loop (PLL). Hence, to leverage the advantages of this method and expand its application in power system control, this paper reviews different VOC implementations. Mainly, this paper focuses on the studies related to the fundamental theory of oscillators and design process. Additionally, there are discussions on the stability analysis of VOC‐based systems, harmonics and pre‐synchronization. Challenges on the compatibility with heterogeneous controllers, fault ride‐through and other limitations of VOC including non‐inertial response and coupled power control are investigated and solutions are outlined.

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Section: Unified Virtual Oscillatormentioning

confidence: 99%

Virtual oscillator‐based methods for grid‐forming inverter control: A review

Aghdam

Agamy

2022

IET Renewable Power Gen

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“…The system parameters are listed in Table I. Note that two interleaved sub-phases are used in each phase and hence an effective switching frequency of 75kHz is achieved which reduces the LCL filter requirements [25]. The control parameters are listed in Table II.…”

Section: Appendix a Simulation And Experimental Setupmentioning

confidence: 99%

Transient Stability Assessment for Current-Constrained and Current-Unconstrained Fault Ride Through in Virtual Oscillator-Controlled Converters

Awal

Husain

2021

IEEE J. Emerg. Sel. Topics Power Electron.

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Unified virtual oscillator controller (uVOC) inherits the rigorous analytical foundation offered by oscillator based grid-forming (GFM) controllers and enables fast over-current limiting and fault ride-through (FRT). Control design for effective FRT requires transient stability analysis. Existing transient stability analysis methods and studies are limited in either considering only current unconstrained scenarios or neglecting the simultaneous power angle and voltage dynamics. Under current-constrained faults, the voltage and power angle dynamics are strongly coupled and both play critical roles in determining transient stability. Therefore, decoupled analysis of the two, typically used in transient stability studies, does not offer comprehensive insight into the system dynamics. In this work, the overall FRT method for uVOC is presented and a comprehensive modeling and analysis method for transient stability is developed under both current-saturated and unsaturated symmetrical AC faults. We utilize phase-plane analysis of the overall system in a single graphical representation to obtain holistic insights into the coupled voltage and power angle dynamics. The FRT controller and the analysis method have been validated through simulations and hardware experiments. The results demonstrate that uVOC is not constrained by a critical clearing angle unlike droop and virtual synchronous machine (VSM) type second order controllers.

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“…MPCs have been taking much attention since last decade due to their capability in integrating multiple sources/loads in a cost‐efficient way 7 . Depending on the type of integrated sources/loads, MPCs can be divided into three categories: (a) DC MPCs, 8–10 (b) AC MPCs, 11–13 and (c) hybrid MPCs 14–17 . As shown in Figure 2A, the DC‐based RESs suffering from the intermittency are the main application for DC MPCs, where these sources are integrated with energy storage systems to create a smooth and programmable power generation at output.…”

Section: Introductionmentioning

confidence: 99%

“…In hybrid MPCs, both DC and AC sources/loads are integrated via a unified structure, as depicted in Figure 2C. This kind of MPCs is mainly exploited to connect multiple DC sources to the grid without any individual grid‐side converter 14–16 . As an accepted alternative way, the use of unified AC MPCs such as nine‐switch and multileg converters can reduce the number of switching devices, 18,19 hence the system's cost in ASDs and grid integration of RESs.…”

Section: Introductionmentioning

confidence: 99%

“…7 Depending on the type of integrated sources/loads, MPCs can be divided into three categories: (a) DC MPCs, [8][9][10] (b) AC MPCs, [11][12][13] and (c) hybrid MPCs. [14][15][16][17] As shown in Figure 2A, the DC-based RESs suffering from the intermittency are the main application for DC MPCs, where these sources are integrated with energy storage systems to create a smooth and programmable power generation at output. In DC MPCs, the DC-based RESs are directly connected to DC ports, although AC-based sources have to be connected using an individual rectifier.…”

Section: Introductionmentioning

confidence: 99%

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A novel multiport converter switching scheme to integrate multiple renewable energy sources

Bizhani

Techato

Noroozian

et al. 2022

Circuit Theory & Apps

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Summary In this paper, an innovative switching scheme named simultaneous space vector modulation (SSVM) is proposed for integrating various AC sources in the energy industry using a unified multiport converter. The proposed SSVM technique is applied to the multileg topology of a multiport converter, which is an encouraging option for the grid integration of renewable energy sources and multimachine drives. Considering the shared leg in the multileg converter, the proposed SSVM can utilize the utmost simultaneous switching states between different ports, resulting in lower switching loss and better DC‐link voltage utilization compared with the conventional sequential space vector modulation approach. A novel decision matrix concept is introduced to identify the simultaneous switching states. For this aim, according to the number of ports of the multileg converter, decision matrices containing valid simultaneous switching states are first calculated. Then, they are defined as look‐up tables in the proposed SSVM to be retrieved and exploited in every sampling period. The effectiveness of the proposed SSVM for a seven‐leg version of the multileg converter is assessed using the simulation analysis and real‐time validation. The capability of the proposed SSVM‐based multiport converter in grid integration of AC renewable energy sources is also verified considering two permanent magnet synchronous generator (PMSG)‐based wind turbines with real wind speed patterns. The simulation results confirm that the proposed SSVM is properly able to manage the power flow between different ports and improve the DC voltage utilization and switching loss compared with the sequential SVM.

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A Grid-Forming Multi-Port Converter using Unified Virtual Oscillator Control

Cited by 10 publications

References 10 publications

Virtual oscillator‐based methods for grid‐forming inverter control: A review

Virtual oscillator‐based methods for grid‐forming inverter control: A review

Transient Stability Assessment for Current-Constrained and Current-Unconstrained Fault Ride Through in Virtual Oscillator-Controlled Converters

A novel multiport converter switching scheme to integrate multiple renewable energy sources

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