Distributed Generation Plants Research Articles

Complex use of smart grid technology in railway traction networks

The goal is to develop a methodology for modeling electric power supply systems for railways equipped with a complex of devices implemented using smart grid technologies. The results obtained showed that a reliable and high-quality electric power supply for traction of trains and non-traction consumers could be implemented on the basis of the integrated use of Smart Grid active elements, such as a phase converter, an active harmonic conditioner, a controlled reactive power source and a distributed generation plant. On the basis of computer simulation, it has been established that in the absence of reactive power sources, noticeable voltage fluctuations are observed on the 10 kV buses of a non-traction consumer. The asymmetry approaches the limit of normally permissible values; turning off the active filter leads to an increase in the total voltage harmonic distortion up to 16%; in the presence of the whole complex of active devices, high quality of electricity is achieved. The phase number converter is robust and has low sensitivity to parameter setting errors; voltage deviations caused by a limited range of changes in reactive power in its source are short-term and do not exceed values acceptable for practice. Thus, on the basis of Smart Grid technologies, it is possible to implement the connection of distributed generation plants directly to the traction network using a device for transducing the number of phases, formed according to the inverted Steinmetz’s circuit. Elimination of harmonic distortions created by rectifier electric locomotives is carried out by means of an active conditioner of higher harmonics. A controlled reactive power source can be used to maintain voltage levels.

Transient angular stability on medium voltage distribution systems with distributed generation

The dynamic behaviour of a 32 MW gas-turbine generating unit, connected to the 23 kV main busbar of a substation, is analysed in this article. The study is focused on the representative faults occurring in an electrical system and allows the determination of the maximum times in with a fault must be delivered to maintain the stability of generator. A three-phase power network is modelled with the Alternative Transients Program (ATP). Simulation results are reported and analysed for typical variables of interest such as machine rotor angle, frequency, and power. According to the study results, machine stability is greatly affected by three-phase faults, as compared to the dynamic behaviour under single-phase faults. The analysis carried out is useful to improve and maintain the security of operation of the electrical grid and in aligned to the current regulations and recent reforms of the Mexican electric sector. The fact that the performed study was usually not mandatory but has been pending since the commissioning of distributed generation plants in the Central Mexican Region is emphasized.

The Study of Transition to the Isolated Operation of Power Supply Systems with Distributed Generation Plants and High Power Energy Storage Units

The Study of Transition to the Isolated Operation of Power Supply Systems with Distributed Generation Plants and High Power Energy Storage Units

The study of the isolated power supply system operation with controlled distributed generation plants, energy storage units and drive load

Energy storage units (ESU) and distributed generation (DG) plants including those using renewable energy sources can be used to develop isolated power supply systems (IPSS) and enhance their reliability. Operation of DG plants in the IPSS requires to consider restrictions for consumers maximum load, as well as effects of abrupt load increase or load shedding on the generating plants. These problems can be resolved using ESU and intelligent technologies for DG plants control. The paper considers IPSS of an industrial facility with turbogenerator plants (TGP), wind power plant (WPP) and high-capacity ESU for which fuzzy control systems and prognostic controllers were used. The simulation was performed in the MATLAB system using the Simulink and SimPowerSystems software packages. Normal and emergency modes were studied in IPSS with TGP, WPP, and high-capacity ESU. The simulation results indicated that combined use of high-capacity ESU and prognostic controller of TGP generator rotor speed allows to ensure stability and survivability of IPSS enhancing its damping properties. The auto-prognostic controller of the TGP generator, which does not require special adjustment, provides high quality indicators of the IPSS control in all considered modes.

Применение асинхронизированных генераторов в электрических сетях с пониженным качеством электроэнергии

For decentralized power generation, small-capacity asynchronized generators (AGs) can be used, which are able to yield a number of positive effects in comparison with conventional synchronous machines: higher stability limits, wider reactive power adjustment ranges, simpler synchronization with the grid due to the ability to control the EMF phase, and the possibility to maintain synchronous operation in case of failure in one of the field windings. The article describes the model of a grid equipped with asynchronized generators with automatic excitation and rotor speed control systems, which is developed in the MATLAB software package environment. Normal and emergency operation modes of a 35 kV grid with distributed generation plants based on asynchronized machines under the conditions of degraded electric power quality due to the presence of electric traction loads are simulated. The influence of AGs on emergency and post-emergency modes are determined, and the harmonic distortion levels are estimated. For comparison, the grid operation modes are simulated for the case of using synchronous machines as generation sources. The influence of higher harmonic components on the performance of the proposed automatic control system is analyzed. The obtained study results have shown that with using asynchronized generators, better control processes and better quality of electric power are obtained in comparison with those in a grid equipped with synchronous machines; in addition, the stability limits are increased, and the synchronization processes are simplified.

Wave power assessment for electricity generation with powerbouy system by wave motion emulation modelling

Among different technologies, the Wave Energy Conversion (WEC) represents an efficient, clean and sustainable source for generating electricity, however creating distributed generation plants with Wave Energy Potential (WEP) necessitates extremely careful estimation. Therefore, a new model using five components of Fourier series has been presented for WEP estimation. The model helps reduce the imprecision in the wave estimation due to the time resolution of wave data, permits to emulate the buoy movement when a wave reaches it (hydrodynamics studies), facilitates in the emulation of the linear electric generator magnets movement located inside a powerbouy system (electromagnetic simulations) and helps obtain the correct generated voltage curve shapes and power quality with the aim of designing and selecting the electrical components to connect the microgrid by wave power to the power system. The model is a function of significant height and periodicity of the waves and offers an evidence for a better WEP estimation. Irregular wave profile is very important to predict the voltage and power quality supplied by the powerbouy. When the irregular wave profile is ignored, WEP estimations could exceed 90% and produce false expectations of electric power generation and incorrect sizing of electric components for the microgrid by wave power. Thus, true WEP estimation can prove to be a good investment decision tool to develop wave energy plants. For proposed model validation, the results of an assessment of wave energy in 25 different geographic coordinates of the Mexican coast, based on wave motion profile, suggest that the Mexican Pacific side is suitable for wave power plant development, 100–500 kW for each installed powerbouy in such points. Consequently, this work contributes to obtaining new techniques in WEP estimation based on wave parameters in order to get electrical parameters for true electrical power. Thus, search for technological development for the electrical equipment is required to install for its harvest in wave microgrid system.

Математические модели для определения предельных режимов в электрических сетях с установками распределенной генерации

Decentralization of electricity generation based on distributed generation plants is an important segment of the new technology platform for the power industry. On the basis of this approach, significant positive effects can be obtained, which consist in reducing financial costs of energy supply, increasing the uninterrupted power supply, improving the quality of electricity and stimulating the use of renewable energy sources. Effective use of distributed generation in electric power systems requires the development of methods and tools that provide coordinated management of normal, emergency and post-emergency modes. Of particular relevance is the problem of determining the limit operating modes of networks, at the nodal points of which relatively low power generators are connected. In some situations, for example, when using small hydraulic stations, groups of such generators can be located at significant distances for 6-10-20 kV distribution networks from consumption centers. In this case there will be a noticeable limitation of the regions of static aperiodic stability. The article presents the results of developments aimed at implementing methods for determining the limit operating modes by static aperiodic stability in networks with distributed generation plants. The proposed approach is based on the limit modes equations which provide the formation of effective algorithms for the operational finding of points belonging to the boundaries of stability regions. The results of the construction of the indicated areas for a 6 kV electric network with distributed generation plants based on low-power hydraulic stations are presented. Additionally, the transient processes in the studied electric power system were simulated in the Matlab system for various space points of the controlled mode parameters.

Wave Energy Estimation based on the Statistical Analysis of the Significant Height and Periodicity

The study of wave potential at coastal points requires involving many parameters and degrees of freedom of ocean wave motion. In this work, we focus to the two most relevant ones: the wave’s significant height and its periodicity. By means of a descriptive statistical analysis of oceanographic databases from two coastal nodes in Mexico, we present realistic estimations of wave potentials. This work allows advancing the knowledge for the estimation of ocean wave energy potential and can be useful for future design of distributed generation plants based on this renewable alternative.

Digital Twin of the Distributed Generation Plant

This article describes the concept of building a digital twin of the distributed generation (DG) plant operating on based on a synchronous generator with a fuzzy auto-tuning unit for automatic voltage regulator and automatic speed regulator. The structure of the digital twin is represented as a hierarchal fuzzy model built using experimental data. Programmatically implemented algorithms for optimization of term aggregations membership functions and numerals from knowledge base rules. The results of experiments on obtaining an optimized neuro-fuzzy model for regulating the generator rotor frequency are presented. The proposed algorithms can be used in further research on the construction of a digital twin of the DG plant, as well as for solving the problem of automatic regulators tuning.

A Microgrid Energy Management System Based on Non-Intrusive Load Monitoring via Multitask Learning

Non-intrusive load monitoring (NILM) enables to understand the appliance-level behavior of the consumers by using only smart meter data, and it mitigates the requirements such as high-cost sensors, maintenance/update and provides a cost-effective solution. This article presents an efficient NILM-based energy management system (EMS) for residential microgrids. Firstly, smart meter data are analyzed with a multi-task deep neural network-based approach and the appliance-level information of the consumers is extracted. Both consumption and operating status of the appliances are obtained. Afterward, the energy consumption behaviors of the end-users are analyzed using these data. Accordingly, average power consumption, operation cycles, preferred usage periods, and daily usage frequency of the appliances were obtained with an average accuracy of more than 90%. The obtained results were integrated into an EMS to create an efficient and user-centered microgrid operation. The developed model not only provided the optimum dispatch of distributed generation plants in the microgrid but also scheduled the controllable loads taking into account customers' satisfaction. It was demonstrated with the help of simulation that the proposed NILM-based EMS model improves the operation cost/customer satisfaction ratio between 45% and 65% compared to a traditional EMS.

Stochastic reconfiguration of distribution system considering stability, correlated loads and renewable energy based DGs with varying penetration

This paper presents a probabilistic stability constrained optimal configuration model to simultaneously consider uncertainties with correlation and small signal stability for distribution system in the presence of photovoltaic based distributed generation (PV-DG) and small hydro power plant based DG (SHPP-DG). The objective is to minimize real power loss, number of switching operations and maximize the voltage stability margin while maintaining the constraints of bus voltage, branch current carrying capacity, and radiality of distribution system (DS) and preserving the small signal stability of the DS. Further, the impact of PV penetration on the small signal stability constrained distribution system reconfiguration (DSR) is assessed. It is also shown that the stochastic variation of PV-DG can cause system instability. With increasing level of PV-DG penetration, the probability of the system becoming unstable increases. For solving this constrained, multi-objective optimization problem, a knee point driven evolutionary algorithm along with three point estimation (KnEA-PE) method is applied. The feasibility and effectiveness of this method has been tested on IEEE 33 bus, IEEE 69 bus and IEEE 119 bus radial distribution systems.

ИСПОЛЬЗОВАНИЕ ПРОГНОСТИЧЕСКИХ АЛГОРИТМОВ И НЕЧЕТКИХ СИСТЕМ УПРАВЛЕНИЯ ДЛЯ УСТАНОВОК РАСПРЕДЕЛЕННОЙ ГЕНЕРАЦИИ

The concept of intelligent electric networks provides for the widespread use of distributed generation plants with renewable sources, in particular, implemented on the basis of windgenerating plants. The report addresses the issues of sharing prognostic algorithms and fuzzy regulators for controlling wind-generating installations

Управление режимами систем электроснабжения с установками распределенной генерации, сформированными на основе асинхронизированных машин

Управление режимами систем электроснабжения с установками распределенной генерации, сформированными на основе асинхронизированных машин

Smart Transformer-Enabled Meshed Hybrid Distribution Grid

Renewable energy sources (RES) induce problems such as voltage and current limit violations, absence of inertia and consequent stability problems, and poor power quality. Smart transformer (ST) is a promising solution for avoiding such a changing grid scenario leading to strong grid reinforcements. This article proposes an ST-enabled meshed hybrid distribution grid to achieve voltage and power flow control simultaneously with a centralized controller. In this configuration, a low-voltage dc (LVdc) line is proposed which connects the ST LVdc link with the dc bus of distributed generation (DG) converters. This introduces various active power flow paths to support the loads. The DG converters supply active power near the load points which ensures that line losses are reduced significantly while achieving improved voltage regulation as compared to conventional microgrid. Moreover, the DG converters can draw active power from ST LVdc link during absence of RES to support the load, resulting in improved utilization of these converters. The control complexity of the DG converters is reduced as the ST controls both the LVac and LVdc line voltages. Further, the newly developed power flow path allows reverse power flow from DG plants more efficiently. Performance of the proposed system is verified with simulation and experimental results.

Prompt determination of the static stability margins in electrical energy systems equipped with distributed generation plants

The wide use of distributed generation (DG) technologies in electrical energy systems (EES) requires development of new control algorithms in normal, emergency and postemergency modes. The issues of determining the static aperiodic stability (SAS) margin in EES equipped with DG plants are of particular relevance. These plants can be removed from the consumption centers, which can lead to SAS reserves depletion. The article presents the results of studies aimed at the developing SAS reserves express calculation methods in EES equipped with DG plants. An effective technique to determine stability margins was proposed based on one of the modifications of limiting modes equations. The results of determining SAS for an electrical network with distributed generation plants are presented. Additionally, the simulation of transient processes in the studied EES for various points in the space of the mode’s controlled parameters has been carried out in the Matlab system.

Flicker control in mains with distributed generation plants

The use of distributed generation (DG) plants in power supply systems is a rapid development line. However, the impact of DG on power quality is multivalued. On the one hand, the presence of DG allows to reduce voltage losses. On the other hand, a phenomenon called flicker and associated with rapid voltage fluctuations is possible. This effect is usually manifested at an abrupt voltage drop in the DG generator connection unit. The processes taking place in the network when flicker occurs in networks with DG have not been sufficiently studied. The article presents results of the flicker modeling in a network equipped with DG plants, implemented on the basis of synchronous generators. The results obtained indicated that with sharp disturbances caused by switching on and off an additional load, flicker is observed in networks with unregulated generators, accompanied by voltage and frequency fluctuations. Based on the wavelet transformation and spectral analysis methods, it was found that the power spectral density of the generated flicker-noise is inversely proportional to the frequency. The use of look-ahead control algorithms to control the excitation and rotors rotational speed of the DG plants generators, as well as concordant adjustment of their controllers, increases stability and removes flicker completely.

Effects of asynchronized generators on emergency modes of power mains with inferior power quality

Application of asynchronized generators (ASG) in distributed generation plants allows to obtain the following positive results: increase stability margins; expand reactive power adjustment ranges; simplify processes of synchronization to line due to possibility of frequency and EMF phase control; ensure the unit’s operation in synchronous mode when one of excitation windings is damaged. The work provides description of the developed ASG computer model and the system of excitation automatic control. The studies are conducted in the MATLAB system using the Simulink and SimPowerSystems software packages. Emergency modes were simulated for the mains with ASG-based distributed generation plants in conditions of inferior power quality. ASG influence on emergency modes and levels of harmonic distortions in the mains were determined.

Development of technical requirements for generating units of distributed energy resources in the conditions of electric power systems transformation

The paper describes the prospects for commissioning distributed energy resources (DER) in Russia and considers the historical features, as well as the consequences of structural, qualitative, and quantitative changes in Russia’s UES. The main short and long-term transformational changes, as well as current and future challenges, are described. The main changes in the circuit and operating conditions when integrating DERs into distribution grids in the mass scale are shown. The authors justify the need for making changes in the existing technical requirements for power equipment, relay protection, and automation instruments. Technical requirements for the distributed generation plants and new types of equipment (energy storage systems, devices with power converters, etc.) should be developed. The paper proposes a new approach to the development of the DER-based power distribution schemes considering the specifics of modern generating units and loads. It is noted that solving these issues will ensure reliable DER functioning as part of power systems.

Distributed Generation of Electricity and Sustainable Regional Growth

The rather high distributed generation (DG) ramp-up observed in the world is largely associated with the progress in low-power generation technologies and the measure of state support for renewable energy sources. Distributed generation delivers sustainable development of low electricity demand areas where centralized power supply is too expensive. In Russia, the installed electrical capacity of DG has reached 37 GW and its contribution to the country’s electric power industry turns out to be very significant: approximately 13.7%. Moreover, more than half of the available facilities are used as stand-by, peak-load, and seasonal sources of electricity. The technological basis of the DG in the country is thermal power plants. The article considers in detail the possible options for operating DG plants. It is shown that the priority areas for the DG application are areas with low density of electrical loads, including rural and low population areas. The presence of infrastructural restrictions for connecting new consumers to the electrical network favors the use of DG in the centralized power supply zone as well. Prospects for the further DG application in the world are associated with the development of renewable energy and the improvement of electrochemical technologies, primarily electricity storage devices. In Russia, apparently, DG technologies based on fossil fuels will prevail for a long time. The country’s great demand for thermal energy will contribute to the widespread use of cogeneration plants. A significant reserve for DG development is the reconstruction of the country’s numerous gas boilers in small CHP plants with a potential of 41 GW of electrical capacity.

Метод пассивной идентификации математической модели установки распределенной генерации

Метод пассивной идентификации математической модели установки распределенной генерации