scholarly journals Secondary Control for Storage Power Converters in Isolated Nanogrids to Allow Peer-to-Peer Power Sharing

Electronics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 140 ◽  
Author(s):  
Eva González-Romera ◽  
Enrique Romero-Cadaval ◽  
Carlos Roncero-Clemente ◽  
Mercedes Ruiz-Cortés ◽  
Fermín Barrero-González ◽  
...  
Keyword(s):  
Power Flow ◽  
Control Method ◽  
Low Voltage ◽  
Hierarchical Control ◽  
Power Converter ◽  
Power Sharing ◽  
Primary Control ◽  
Secondary Control ◽  
Control Loops ◽  
Energy Interchange

It is usual in literature that power sharing among grid-forming sources of an isolated microgrid obeys their energy rating, instead of economic agreements between stakeholders, and circulating energy among them is usually avoided. However, these energy interchanges make strong sense and classical power sharing methods must be reformulated in the context of prosumer-based microgrids. This paper proposes a secondary control method for a prosumer-based low-voltage nanogrid that allows for energy interchange between prosumers, where storage systems, together with PV generators, are the controllable grid-forming sources. A power flow technique adapted to islanded microgrids is used for secondary control algorithm and the whole hierarchical control strategy for the prosumer converter is simulated and validated. This hierarchical control consists of three stages: tertiary control plans the energy interchange among prosumers, secondary obtains different voltage and power setpoints for each of the grid-forming sources, and, finally, primary control guarantees stable voltage and frequency values within the nanogrid with droop rules. Inner control loops for the power converter are also defined to track setpoints and assure stable performance. Simulation tests are carried out, which prove the stability of the proposed methods and the accuracy of the setpoint tracking.

scholarly journals Decentralized Fast Delayed Signal Cancelation Secondary Control for Low Voltage Ride-Through Application in Grid Supporting Grid Feeding Microgrid

2021 ◽  
Vol 9 ◽  
Author(s):  
Elutunji Buraimoh ◽  
Innocent E. Davidson ◽  
Fernando Martinez-Rodrigo
Keyword(s):  
Low Voltage ◽  
Hierarchical Control ◽  
Voltage Regulation ◽  
Power Sharing ◽  
Primary Control ◽  
Distributed Energy ◽  
Secondary Control ◽  
Low Voltage Ride Through ◽  
Control Scheme ◽  
Real Time Digital Simulator

In this study, a distributed secondary control is proposed alongside the conventional primary control to form a hierarchical control scheme for the Low Voltage Ride-Through (LVRT) control and applications in the inverter-based microgrid. The secondary control utilizes a fast Delayed Signal Cancelation (DSC) algorithm for the secondary control loop to control the reactive and active power reference by controlling the sequences generated. The microgrid consists of four Distributed Energy Resources (DER) sources interfaced to the grid through interfacing inverters coordinated by droop for effective power-sharing according to capacities. The droop also allows for grid supporting application for microgrid’s participation in frequency and voltage regulation in the main grid. The proposed decentralized fast DSC performance is evaluated with centralized secondary and traditional primary control using OPAL-RT Lab computation and MATLAB/SIMULINK graphical user interface for offline simulations and real-time digital simulator verification. This study presents and discusses the results.

scholarly journals A Finite-Time Robust Distributed Cooperative Secondary Control Protocol for Droop-Based Islanded AC Microgrids

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2936
Author(s):  
Shafaat Ullah ◽  
Laiq Khan ◽  
Mohsin Jamil ◽  
Muhammad Jafar ◽  
Sidra Mumtaz ◽  
...  
Keyword(s):  
Distributed Control ◽  
Finite Time ◽  
Control Method ◽  
Hierarchical Control ◽  
Research Work ◽  
Primary Control ◽  
Secondary Control ◽  
Control Protocol ◽  
Multi Agent ◽  
Power Outputs

In this research work, a resilient finite-time consensus-based distributed secondary control protocol is presented for droop-based distributed generating (DG) units of an islanded AC microgrid (MG). Through a multi-agent control structure, the DG units of the microgrid adjust their active power outputs so that they reach an agreed-upon value in a finite time. Concurrently, all the DG units are forced to operate with their frequencies regulated to the reference MG frequency in a finite time, despite time-varying load perturbations. Each DG unit is provided with a hierarchical control architecture, where the primary control is achieved using the droop control method, while the secondary control is established through the proposed distributed control protocol. The communication between DG units takes place over a sparse communication network. The proposed control protocol is robust to both small and sufficiently large communication latencies and it supports the plug-and-play feature of DG units. Different time-domain-based numerical simulations are carried out on a small as well as large microgrid testbenches in Matlab/Simulink and demonstrate the correctness and effectiveness of the proposed distributed control protocol. A comparative study is also presented with the existing distributed control protocol, and it is found that the proposed strategy is superior in its performance.

Voltage and Frequency Droop Control in an Autonomous Microgrid

2012 ◽  
Vol 236-237 ◽  
pp. 568-575
Author(s):  
Xiao Ying ◽  
Heng Wei Lin ◽  
Zhao Yang Yan ◽  
Jian Xia Li ◽  
Ming Su
Keyword(s):  
Control Method ◽  
Low Voltage ◽  
Impedance Control ◽  
Power Sharing ◽  
Voltage Source ◽  
Droop Control ◽  
Parallel Operation ◽  
Communication Signals ◽  
Control Loops ◽  
Control Scheme

In this paper, a method for the parallel operation of inverters in an autonomous microgrid system is adopted. This paper presents the resistive output impedance control scheme that allows multiple voltage source converters (VSCs) to operate in parallel in a VSC fed microgrid. The control loops are taking into account the special nature of a low-voltage microgrid, in which the line impedance is mainly resistive. In contrast with the conventional droop-control method, the proposed controller uses a virtual resistance without communication signals to achieve good power sharing, which is insensitive to line-impedance unbalances.

scholarly journals From Hierarchical Control to Flexible Interactive Electricity Services: A Path to Decarbonization

2021 ◽  
Vol 15 ◽  
pp. 1558-1570
Author(s):  
Marija D. Ilic ◽  
Pedro M. S. Carvalho
Keyword(s):  
Power Flow ◽  
Distribution Systems ◽  
Reactive Power ◽  
Hierarchical Control ◽  
Electric Energy ◽  
Specific Model ◽  
Net Energy ◽  
Primary Control ◽  
Interaction Variables ◽  
And Control

We propose to conceptualise electric energy systems as complex dynamical systems using physically intuitive multilayered energy modelling as the basis for systematic diverse technology integration, and control in on-line operations. It is shown that such modelling exhibits unique structure which comes from the conservation of instantaneous power (P) and of instantaneous reactive power ( _Q), (interaction variables (intVar)) at the interfaces of subsystems. The intVars are used as a means to model and control the interactive zoomed-out inter-modular (inter-area, inter-component) system dynamics. Control co-design can then be pursued using these models so that the primary control shapes intVars of its own module by using its own lowlevel detailed technology-specific model and intVar info exchange with the neighbours. As a result, we describe how the proposed approach can be used to support orderly evolution from today’s hierarchical control to a platform enabling flexible interactive protocols for electricity services. The potential for practical use of the proposed concepts is far-reaching and transparent. All that needs to be conceived is that intVar characterising any intelligent Balancing Authority (iBA) is a generalisation of today’s Area Control Error (ACE) characterising net energy balance of a Balancing Authority (BA). An iBA can be any subsystem with its own sub-objectives, such as distributed energy resources (DERs) comprising customers and grid forming microgrids; distribution systems; transmission systems; Independent System Operators (ISOs); and, ultimately, electric energy markets within large interconnection. Several industry problems are described as particular sub-problems of general interactive electricity services. These formulations help one compare models and assumptions used as part of current solutions, and propose enhanced solutions. Most generally, feasibility and stability conditions can be introduced for ensuring feasible power flow solutions, regulated frequency and voltage and orderly power exchange across the iBAs.

Hierarchical Control of Multi-Domain Power Flow in Mobile Systems: Part II — Aircraft Application

2015 ◽  
Author(s):  
Matthew A. Williams ◽  
Justin P. Koeln ◽  
Andrew G. Alleyne
Keyword(s):  
Power Systems ◽  
Power Flow ◽  
Large Scale ◽  
Control Method ◽  
Hierarchical Control ◽  
Mobile Systems ◽  
Centralized Control ◽  
Modeling Framework ◽  
Control Framework ◽  
Aircraft Application

This two-part paper presents the development of a hierarchical control framework for the control of power flow throughout large-scale systems. Part II presents the application of the graph-based modeling framework and three-level hierarchical control framework to the power systems of an aircraft. The simplified aircraft system includes an engine, electrical, and thermal systems. A graph based approach is used to model the system dynamics, where vertices represent capacitive elements such as fuel tanks, heat exchangers, and batteries with states corresponding to the temperature and state of charge. Edges represent power flows in the form of electricity and heat, which can be actuated using control inputs. The aircraft graph is then partitioned spatially into systems and subsystems, and temporally into fast, medium, and slow dynamics. These partitioned graphs are used to develop models for each of the three levels of the hierarchy. Simulation results show the benefits of hierarchical control compared to a centralized control method.

scholarly journals Photovoltaic Power Converter Management in Unbalanced Low Voltage Networks with Ancillary Services Support

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 972 ◽  
Author(s):  
Fermín Barrero-González ◽  
Victor Pires ◽  
José Sousa ◽  
João Martins ◽  
María Milanés-Montero ◽  
...  
Keyword(s):  
Power Flow ◽  
Reactive Power ◽  
Low Voltage ◽  
Renewable Energy Sources ◽  
Distribution Network ◽  
Power Converter ◽  
Maximum Energy ◽  
Practical Implementation ◽  
Network Operation ◽  
The Impact

The proliferation of residential photovoltaic (PV) prosumers leads to detrimental impacts on the low-voltage (LV) distribution network operation such as reverse power flow, voltage fluctuations and voltage imbalances. This is due to the fact that the strategies for the PV inverters are usually designed to obtain the maximum energy from the panels. The most recent approach to these issues involves new inverter-based solutions. This paper proposes a novel comprehensive control strategy for the power electronic converters associated with PV installations to improve the operational performance of a four-wire LV distribution network. The objectives are to try to balance the currents demanded by consumers and to compensate the reactive power demanded by them at the expense of the remaining converters’ capacity. The strategy is implemented in each consumer installation, constituting a decentralized or distributed control and allowing its practical implementation based on local measurements. The algorithms were tested, in a yearly simulation horizon, on a typical Portuguese LV network to verify the impact of the high integration of the renewable energy sources in the network and the effectiveness and applicability of the proposed approach.

scholarly journals Energy Storage Power and Energy Sizing and Specification Using HSSPFC

Electronics ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 638
Author(s):  
Mehrzad M. Bijaieh ◽  
Wayne W. Weaver ◽  
Rush D. Robinett
Keyword(s):  
Energy Storage ◽  
Power Flow ◽  
Storage Systems ◽  
Hierarchical Control ◽  
Power Sharing ◽  
Power Flow Control ◽  
Three Phase ◽  
Surface Shaping ◽  
Power And Energy ◽  
Simulated Hybrid

The intermittent nature of renewable sources requires the integration of Energy Storage Systems (ESSs) with appropriate power and energy densities. One of the applications of Hamiltonian Surface Shaping and Power Flow Control (HSSPFC) is to size ESSs for power and energy densities by employing them as sole actuators of Microgrid (MG) systems. This Article provides a comprehensive yet simplified example of utilization of HSSPFC to size ESSs of inverter-based three-phase MG systems under hierarchical control. Here, the distributed Hamiltonian controller is expanded for control of parallel ESSs and power sharing metrics are defined to distribute power between hybrid storage systems according to their power and energy density capabilities. Simulated hybrid ESSs comprising battery and flywheel systems are used as examples to demonstrate the behaviour of the expanded control, verify the power sharing criteria and illustrate ESS design and specification by utilizing HSSPFC.

scholarly journals Optimized Hierarchical Control for an AC Microgrid Under Attack

Ingeniería ◽  
2019 ◽  
Vol 24 (1) ◽  
pp. 64-82
Author(s):  
Vladimir Toro ◽  
Eder David Baron ◽  
Eduardo Mojica-Nava
Keyword(s):  
Power Flow ◽  
Hierarchical Control ◽  
Active Power ◽  
Cyber Attacks ◽  
Cyber Attack ◽  
Secondary Control ◽  
Confidence Factor ◽  
Communication Links ◽  
Local Controller ◽  
The Stability

Context: An inverter-based microgrid working in islanded mode can suffer cyber- attacks, these can be done against either the local controller or the communication links among the inverters. Secondary control is able to reject those attacks, however, a tertiary control action is necessary in order to stabilize the power flow among the microgrid. Method: Confidence factor technique allows to reject attacks in a microgrid acting directly over the secondary control, however, this technique omits other factor related to the power available. In this case, secondary control was complemented with a tertiary control that includes optimization criteria. Results: An inverter-based microgrid is simulated in Matlab for different scenarios and under cyberattack, this allows checking the correct response of the controller under attacks and the effective powersharing among inverters. Conclusions: The tertiary control allows stabilizing the active power of the system after the rejection of a cyber-attack by the secondary control. Each inverter supplies active power according to its máximum power rating without affecting the stability of the whole system.

scholarly journals Low-Voltage Ride-Through Operation of Grid-Connected Microgrid Using Consensus-Based Distributed Control

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2867 ◽  
Author(s):  
Woon-Gyu Lee ◽  
Thai-Thanh Nguyen ◽  
Hyeong-Jun Yoo ◽  
Hak-Man Kim
Keyword(s):  
Distributed Control ◽  
Reactive Power ◽  
Control Method ◽  
Low Voltage ◽  
Power Sharing ◽  
Consensus Algorithm ◽  
Stable Operation ◽  
Low Voltage Ride Through ◽  
Primary Layer ◽  
Secondary Layer

Since the penetration of distributed energy resources (DERs) and energy storage systems (ESSs) into the microgrid (MG) system has increased significantly, the sudden disconnection of DERs and ESSs might affect the stability and reliability of the whole MG system. The low-voltage ride-through (LVRT) capability to maintain stable operation of the MG system should be considered. The main contribution of this study is to propose a distributed control, based on a dynamic consensus algorithm for LVRT operation of the MG system. The proposed control method is based on a hierarchical control that consists of primary and secondary layers. The primary layer is in charge of power regulation, while the secondary layer is responsible for the LVRT operation of the MG system. The droop controller is used in the primary layer to maintain power sharing among parallel-distributed generators in the MG system. The dynamic consensus algorithm is used in the secondary layer to control the accurate reactive power sharing and voltage restoration for LVRT operation. A comparison study on the proposed control method and centralized control method is presented in this study to show the effectiveness of the proposed controller. Different scenarios of communication failures are carried out to show the reliability of the proposed control method. The tested MG system and proposed controller are modeled in a MATLAB/Simulink environment to show the feasibility of the proposed control method.

scholarly journals Unified Power Flow Controller Based on Autotransformer Structure

Electronics ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1542
Author(s):  
Hyun-Jun Lee ◽  
Dae-Shik Lee ◽  
Young-Doo Yoon
Keyword(s):  
Power Flow ◽  
Single Phase ◽  
Low Voltage ◽  
Power Converter ◽  
Unified Power Flow Controller ◽  
Phase System ◽  
Three Phase ◽  
Flow Controller ◽  
And Control ◽  
Power Flow Controller

This paper proposes a new unified power flow controller (UPFC) topology. A single phase of them system with the proposed topology consists of an N:2 transformer with a center tap at the low-voltage side and a power converter module comprising full- and half-bridge converters. A three-phase system can be implemented with three devices. While the conventional UPFC topology uses two three-phase transformers, which are called series and parallel transformers, the proposed topology utilizes three single-phase transformers to implement a three-phase UPFC system. By using an autotransformer structure, the power rating of the transformers and the voltage rating of switches in the power converter module can be significantly decreased. As a result, it is possible to reduce the installation spaces and costs compared with the conventional UPFC topology. In addition, by adopting a full- and half-bridge converter structure, the proposed topology can be easily implemented with conventional power devices and control techniques. The techniques used to control the proposed topology are described in this paper. The results obtained from simulations and experiments verify the effectiveness of the proposed UPFC topology.

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