scholarly journals Rapidly Accelerated Synchronous Generators in CAES Systems for Frequency Support in Power Grids

2021 ◽  
Author(s):  
◽  
Efim Sturov
Keyword(s):  
Mathematical Model ◽  
Renewable Energy Sources ◽  
Synchronous Generator ◽  
Power Grids ◽  
Small Scale ◽  
Rotational Inertia ◽  
Control Parameters ◽  
Electrical Networks ◽  
Hydraulic Motor ◽  
Synchronous Generators

<p>Modern electrical networks are transformed through the use of intermittent sources of energy, such as small-scale photovoltaic installations and wind turbines. By reducing the carbon footprints associated with centralised power grids, they are made more vulnerable to contingent under-frequency events. The renewable energy sources can't provide the required rotational inertia to make the power grid's frequency stable and to be able to assist in restoring the frequency. In New Zealand, Transpower (system operator) is responsible for normalising the frequency in case of contingent events to avoid blackouts in the networks.    In case of contingent events in power grids, additional power must be delivered to the networks with the use of primary frequency support systems. Internationally these systems are represented by under loaded power plants, where power output can be adjusted by controlling the primary governor output. This approach incurs no-load running costs and to avoid these costs generation units should be maintained at rest. The most efficient and technically feasible solution is to use synchronous generators that are already present in the power grids or can be additionally delivered to the grids as stand-alone units. However, with the use of the traditional synchronisation method, the generators cannot be synchronised with power grids in a short timeframe (up to 10 s in some countries).   To overcome this disadvantage, a novel synchronisation approach should be designed to synchronise synchronous generators from rest of the electrical networks. This thesis proves that it can be achieved by a ballistic synchronisation approach (and then the improved 2-stage ballistic approach), which computes and follows an acceleration trajectory which simultaneously synchronises both phase and frequency. To achieve this fast acceleration a novel environmentally friendly small-scale compressed air energy storage (ss-CAES) system has been designed. This system utilises a hydraulic drivetrain which transmits very high torque directly to the shaft of a synchronous generator, thus enabling its rapid acceleration.  The hydraulic drivetrain is composed of a proportional throttle valve and a variable-displacement hydraulic motor. The central controller from National Instruments outputs a voltage that controls the opening of the proportional valve. It changes the flowrate in the main hydraulic circuit, meaning that it is possible to control the output torque and velocity of the hydraulic motor. Since it is coupled to a synchronous generator, the control system can control the dynamics of the drivetrain by changing its voltage output.   Computer simulations indicate that this approach enables very rapid synchronisation of a model system to the grid in < 1.5 s at a 100-kW scale. The modelling of the prototype helped to verify the control parameters of the system before the implementation of the algorithm built into the hardware. It should be noted that this model was simulated with the use of the corresponding manufacturer's data. To increase the accuracy of the mathematical model and verify the control parameters, the system components were experimentally characterised with the use of a ubiquitous high-speed data acquisition system.  It resulted in a realistic and accurate mathematical model of the complex electro-hydraulic system, despite the well-known challenges of modelling the hydraulic domain. This model was utilised for the tuning of the control parameters of the system before its experimental testing. Experimental runs confirmed the feasibility of the proposed acceleration and synchronisation approach for synchronisation from the rest of the generator in < 4 s.</p>

scholarly journals Rapidly Accelerated Synchronous Generators in CAES Systems for Frequency Support in Power Grids

2021 ◽  
Author(s):  
◽  
Efim Sturov
Keyword(s):  
Mathematical Model ◽  
Renewable Energy Sources ◽  
Synchronous Generator ◽  
Power Grids ◽  
Small Scale ◽  
Rotational Inertia ◽  
Control Parameters ◽  
Electrical Networks ◽  
Hydraulic Motor ◽  
Synchronous Generators

<p>Modern electrical networks are transformed through the use of intermittent sources of energy, such as small-scale photovoltaic installations and wind turbines. By reducing the carbon footprints associated with centralised power grids, they are made more vulnerable to contingent under-frequency events. The renewable energy sources can't provide the required rotational inertia to make the power grid's frequency stable and to be able to assist in restoring the frequency. In New Zealand, Transpower (system operator) is responsible for normalising the frequency in case of contingent events to avoid blackouts in the networks.    In case of contingent events in power grids, additional power must be delivered to the networks with the use of primary frequency support systems. Internationally these systems are represented by under loaded power plants, where power output can be adjusted by controlling the primary governor output. This approach incurs no-load running costs and to avoid these costs generation units should be maintained at rest. The most efficient and technically feasible solution is to use synchronous generators that are already present in the power grids or can be additionally delivered to the grids as stand-alone units. However, with the use of the traditional synchronisation method, the generators cannot be synchronised with power grids in a short timeframe (up to 10 s in some countries).   To overcome this disadvantage, a novel synchronisation approach should be designed to synchronise synchronous generators from rest of the electrical networks. This thesis proves that it can be achieved by a ballistic synchronisation approach (and then the improved 2-stage ballistic approach), which computes and follows an acceleration trajectory which simultaneously synchronises both phase and frequency. To achieve this fast acceleration a novel environmentally friendly small-scale compressed air energy storage (ss-CAES) system has been designed. This system utilises a hydraulic drivetrain which transmits very high torque directly to the shaft of a synchronous generator, thus enabling its rapid acceleration.  The hydraulic drivetrain is composed of a proportional throttle valve and a variable-displacement hydraulic motor. The central controller from National Instruments outputs a voltage that controls the opening of the proportional valve. It changes the flowrate in the main hydraulic circuit, meaning that it is possible to control the output torque and velocity of the hydraulic motor. Since it is coupled to a synchronous generator, the control system can control the dynamics of the drivetrain by changing its voltage output.   Computer simulations indicate that this approach enables very rapid synchronisation of a model system to the grid in < 1.5 s at a 100-kW scale. The modelling of the prototype helped to verify the control parameters of the system before the implementation of the algorithm built into the hardware. It should be noted that this model was simulated with the use of the corresponding manufacturer's data. To increase the accuracy of the mathematical model and verify the control parameters, the system components were experimentally characterised with the use of a ubiquitous high-speed data acquisition system.  It resulted in a realistic and accurate mathematical model of the complex electro-hydraulic system, despite the well-known challenges of modelling the hydraulic domain. This model was utilised for the tuning of the control parameters of the system before its experimental testing. Experimental runs confirmed the feasibility of the proposed acceleration and synchronisation approach for synchronisation from the rest of the generator in < 4 s.</p>

scholarly journals The Impact of PLL Dynamics on the Low Inertia Power Grid: A Case Study of Bonaire Island Power System

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1259 ◽  
Author(s):  
Yin Sun ◽  
E. de Jong ◽  
Xiongfei Wang ◽  
Dongsheng Yang ◽  
Frede Blaabjerg ◽  
...  
Keyword(s):  
Short Circuit ◽  
Renewable Energy Sources ◽  
Rate Of Change ◽  
Power Grids ◽  
Voltage Source ◽  
Rotational Inertia ◽  
Synchronous Generators ◽  
Correct Operation ◽  
The Impact

To prepare for the future high penetration level of renewable energy sources, the power grid’s technical boundaries/constraints for the correct operation of powerelectronics interfaced devices need to be further examined and defined. This paper investigates the challenge of integrating Voltage Source Converters (VSC) into low inertia power grids, where the system frequency can vary rapidly due to the low kinetic energy buffer available, which used to be provided by the rotational inertia of synchronous generators. The impact of rate of change of frequency (ROCOF) on the PLL dynamics and its subsequent influence on the VSC power stage output is explained. The Bonaire island network is presented as case study. The performance of the VSC is analyzed under a fast ROCOF event, which is triggered by a short circuit fault. A down-scaled experiment is used to validate the Bonaire island network simulation results. It shows that the phase angle error measured by the synchronous-reference frame phase-locked loop (SRF-PLL) is proportional to the slope of the ROCOF and inversely proportional to its controller integral gain constant.

The Control and Model of Synchronous Generator on Ship

2012 ◽  
Vol 195-196 ◽  
pp. 1095-1101
Author(s):  
Le Luo ◽  
Lan Gao ◽  
Liang Chen ◽  
Liang Hu
Keyword(s):  
Mathematical Model ◽  
Control System ◽  
Simulation Model ◽  
Synchronous Generator ◽  
Excitation Control ◽  
Synchronous Generators ◽  
Simulation Test ◽  
Power Station ◽  
Model And Simulation ◽  
The Mathematical Model

This paper analyzes the characteristics of marine power station. The mathematical model and simulation model of synchronous generators AVR+PSS excitation control system was built. At last the simulation test of suddenly add load was did in MATLAB/simulink environment. The result shows that the excitation control system has well stability, rapidity and some robustness.

A New Photovoltaic Blocks Mutualization System For Micro-Grids Using An Arduino Board And Labview

2018 ◽  
Vol 9 (1) ◽  
pp. 98 ◽  
Author(s):  
Abdelkader Mezouari ◽  
Rachid Elgouri ◽  
Mohammed Alareqi ◽  
Khalid Mateur ◽  
Hamad Dahou ◽  
...  
Keyword(s):  
Power Supply ◽  
Renewable Energy Sources ◽  
Electrical Energy ◽  
Power Grids ◽  
Small Scale ◽  
Small Power ◽  
Photovoltaic Panels ◽  
Switching Matrix ◽  
Labview Program ◽  
Micro Grids

The photovoltaic systems are often employed into micro-grids; Micro-grids are small power grids designed to provide a reliable and better power supply to a small number of consumers using renewable energy sources. This paper deals with DC micro-grids and present a new system of monitoring and sharing electricity between homes equipped with photovoltaic panels (PV) in the goal to reduce the electrical energy waste. The system is based on dynamic sharing of photovoltaic blocks through homes in stand-alone areas, using an arduino board for controlling the switching matrix. The LABVIEW program is used to further process and display collected data from the system in the PC screen. A small-scale prototype has been developed in a laboratory to proof the concept. This prototype demonstrates the feasibility and functionality of the system.

scholarly journals Emulating Rotational Inertia of Synchronous Machines by a New Control Technique in Grid-Interactive Converters

2020 ◽  
Vol 12 (13) ◽  
pp. 5346 ◽  
Author(s):  
Meysam Saeedian ◽  
Bahram Pournazarian ◽  
S. Sajjad Seyedalipour ◽  
Bahman Eskandari ◽  
Edris Pouresmaeil
Keyword(s):  
Power Systems ◽  
Large Scale ◽  
Renewable Energy Sources ◽  
Rate Of Change ◽  
Power Grids ◽  
Stable Region ◽  
Control Technique ◽  
Voltage Source ◽  
Rotational Inertia ◽  
Virtual Inertia

Integration of renewable energy sources (RESs) into power systems is growing due to eco-friendly concerns and ever-increasing electricity demand. Voltage source converters (VSCs) are the main interface between RESs and power grids, which have neither rotational inertia nor damping characteristics. Lack of these metrics make the power grid sensitive to frequency disturbances and thereby under frequency, to load shedding activation or even large-scale collapse. In this regard, the contribution of this paper is to develop a new control technique for VSCs that can provide virtual inertia and damping properties with the DC-link capacitors inhered in the DC-side of grid-tied VSCs. The applied VSC is controlled in the current controlled model, with the capability of injecting extra active power with the aim of frequency support during perturbations. The dynamics assessment of the proposed platform is derived in detail. It is revealed that the control scheme performs in a stable region even under weak-grid conditions. Finally, simulations are conducted in MATLAB to depict the efficacy and feasibility of the proposed method. The results show that frequency deviation is mitigated under step up/down changes in the demand, and the rate of change of frequency is improved by 47.37% compared to the case in which the synthetic inertia loop is canceled out.

scholarly journals APPLICATION OF DESIGN APPROACH TO IMPLEMENTATION OF ENERGY EFFICIENT TECHNOLOGIES

2020 ◽  
pp. 290-295
Author(s):  
A. Yevdokymova ◽  
A. Dehtiarenko ◽  
N. Petrenko
Keyword(s):  
Power Systems ◽  
Energy Efficient ◽  
Energy Production ◽  
Alternative Energy ◽  
Power Plants ◽  
Renewable Energy Sources ◽  
Energy System ◽  
Power Grids ◽  
Electrical Networks ◽  
Energy Network

The paper analyzes the peculiarities of the development of the energy sector in Ukraine, as well as in European countries. Existing approaches to energy production are shown. The situation in Ukraine has changed in recent years. Energy production has shifted from centralized to distributed. The emergence of new types of power plants has made it possible to connect to the grid in places where it was previously impossible, a large number of consumers already have their own power units. Therefore, managing the energy network is becoming increasingly complex and therefore requires new approaches. The normative and legislative beginning of the active development of alternative energy in Ukraine already exists, and European and world experience should help Ukraine achieve energy independence and high environmental standards. Existing problems in the development of power grids arise due to the intensive growth of production and consumption of electricity, while the management of power systems is complicated by the growing share of distributed and renewable energy sources with changing production schedule. Improved controllability of electrical networks allows to prevent emergencies by load control programs, division of the network into autonomous zones, etc. Investment is a crucial factor in creating a flexible and efficient power grid based on innovative technical solutions. Implementation of energy efficiency projects is a guideline for improving the intelligent level of the energy system, which will allow energy companies to manage the energy network as a single system, increase profitability, reliability and uninterrupted, reduce technical and commercial losses, improve network management and efficiency. An important role is played by the interaction of all stakeholders in projects - the state, production, energy and energy sales companies, consumers and equipment manufacturers. Thus, the international experience in the transmission and distribution of electricity creates opportunities for successfully implementing projects for the introduction of energy-efficient technologies in our Ukraine.

scholarly journals Тhe study of electronic generation effect on statical aperiodic stability of electrical power system

2020 ◽  
Vol 22 (2) ◽  
pp. 51-64
Author(s):  
A. G. Fishov ◽  
I. S. Murashkina ◽  
A. I. Marchenko ◽  
E. Erdenebat ◽  
Y. S. Ivkin
Keyword(s):  
Power Systems ◽  
Power System ◽  
Renewable Energy Sources ◽  
Electrical Power ◽  
Power Grids ◽  
Small Scale ◽  
Electrical Power System ◽  
Electrical Grid ◽  
Electrical Grids ◽  
Key Aspects

One of the key aspects in the development of power engineering all over the world is the use of distributed small-scale generation. This is both based on fuel carbon resources with a synchronized connection between sources when they are connected to the electric power grids and renewable energy sources operated in the electrical grid via frequency converters (electronic generation). The latter brings an inevitable broad use of inverters in available AC power systems. The objectives of this paper are numerous. First is the desire to study the effect of electronic generation on modes and stability of current electrical grids and electrical power systems. Another objective is to establish requirements for electronic generation control that lets us minimize actions on relay protection coordination and automation upon the integration of electronic generation in power grids. A final objective is to increase the reliability of general electrical modes. This article shows the outcomes of the study on the statical aperiodic stability of the electrical power system upon the integration of electronic generation, requirements for its statical characteristics, and the control when operated within the electrical power system.

scholarly journals On the Electrostatic Inertia in Microgrids with Inverter-Based Generation Only—An Analysis on Dynamic Stability

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3274 ◽  
Author(s):  
Mihai Sanduleac ◽  
Lucian Toma ◽  
Mircea Eremia ◽  
Irina Ciornei ◽  
Constantin Bulac ◽  
...  
Keyword(s):  
Power Systems ◽  
Dynamic Stability ◽  
Low Voltage ◽  
Stability Limit ◽  
Power Grids ◽  
Electrostatic Energy ◽  
Rotational Inertia ◽  
Synchronous Generators ◽  
Voltage Variation ◽  
Point Of Common Coupling

Microgrids are about to change the architecture and the operation principles of the future power systems towards smartness and resiliency. Power electronics technologies are key enablers for novel solutions. In this paper we analyze the benefits of a “microgrid by design” architecture (MDA), using a solid-state transformer (SST) as a low-voltage grid-former and inverter-based generation only. In this context, the microgrid stability is maintained with the help of “electrostatic energy inertia” that can be provided by the capacitor connected to the DC busbar behind the SST inverter topology. This happens in a natural way, alike the mechanical inertia in power systems with synchronous machines, however without depending on frequency and without the need of a rotational inertia. This type of microgrid always operates (both fully connected to the main grid or in islanding mode) with all the necessary mechanisms needed to maintain the microgrid stable—no matter of the perturbations in the upstream of the point of common coupling (PCC). In the case of microgrids with inverter-based generation only (including the energy storage systems), there is no mechanical inertia and different stability mechanisms need to be applied compared to the stability principle of the classical power systems. Our proposed mechanism differentiates from the recently proposed stability assessments of microgrids based on virtual synchronous generators from the control theory perspective. This paper is a continuation of our previous work where the MDA was first introduced. The use-cases and scenarios are based on realistic and yet reasonable complexities, by coupling the disturbance magnitude with the voltage stability limit in power grids. The paper finds meaningful disturbances to test the electrostatic energy inertia at the boundaries of grid stability, as guidance to understand the range of voltage variation for extreme conditions. The results show that in microgrids with inverter-based generation only and passive loads (RLC type) the operation is no longer frequency dependent. The energy of the DC busbar capacitor as electrostatic energy inertia of the MDA has a role similar to that of the rotational machines in classical grids in terms of maintaining dynamic stability, however impacting two different types of stability.

scholarly journals Grid-Following Mode Operation of Small-Scale Distributed Battery Energy Storages for Fast Frequency Regulation in a Mixed-Source Microgrid

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7710
Author(s):  
Amir Hussain ◽  
Wajiha Shireen
Keyword(s):  
Real Time ◽  
Renewable Energy Sources ◽  
Synchronous Generator ◽  
Frequency Instability ◽  
Power Converter ◽  
Rate Of Change ◽  
Frequency Regulation ◽  
Small Scale ◽  
Power Imbalance ◽  
Battery Energy

As the share of power converter-based renewable energy sources (RESs) is high, a microgrid, in islanded mode, is more vulnerable to frequency instability due to (1) sudden power imbalance and (2) low inertia. One of the most common approaches to address this issue is to provide virtual inertia to the system by appropriately controlling the grid-side converter of the RESs. However, the primary frequency controller (PFC) presented in this paper focuses on the fast compensation of power imbalance without adding inertia to the system. The proposed method is based on estimating the real-time power imbalance caused by a disturbance and compensating it using multiple small-scale distributed battery energy storage systems (BESSs). The power imbalance is estimated by observing the initial rate of change of frequency (RoCoF) following a disturbance. Based on the estimated power imbalance and the rating of the BESSs, the reference power for the BESSs is determined. The BESSs are controlled in grid-following mode to compensate for the power imbalance. The performance of the proposed PFC is verified using a Typhoon real-time simulator for various scenarios and is compared with the conventional virtual synchronous generator (VSG) controller.

Distributed ℋ∞ Frequency Control for Inverter Connected Microgrids

2017 ◽  
Author(s):  
Matthew K. Chu Cheong ◽  
Haiya Qian ◽  
Julia Conger ◽  
Dongmei Chen ◽  
Pengwei Du
Keyword(s):  
Optimal Control ◽  
Frequency Control ◽  
Transient Behavior ◽  
Small Scale ◽  
Rotational Inertia ◽  
Synchronous Generators ◽  
Local Data ◽  
Power Sources ◽  
Significant Control ◽  
Power Disturbances

Microgrids are small-scale power networks where distributed generation and inverter interfaced power sources are common. These networks are faced with more significant control challenges; a smaller system can less effectively dampen and distribute power disturbances or fluctuations, and the system frequency is less robust without synchronous generators to provide rotational inertia. In this paper we will develop optimal control algorithms to control the voltage and frequency in an islanded inverter-based microgrid. The voltages and frequency of this system are controlled using decentralized ℋ∞ control. The decentralized controllers operate using only local data, making the control methodolgy scalable. In addition, the studied controllers can be tuned to achieve the desired transient behavior. For voltage and frequency control of microgrids, transient performance is still an area of weakness. The proposed control scheme extends optimal control to the field of microgrid control and can improve the state of microgrid technology.

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