Point Of Common Connection Research Articles

Parameters Tuning of Photovoltaic Power Generation System with Static Synchronous Compensator Based on Chaos Orthogonal Particle Swarm Optimization

China is a country rich in solar energy resources, with good natural conditions for the utilization of solar energy. At present, the main application mode of photovoltaic power generation system is grid-connected photovoltaic power generation. In order to maintain the voltage stability of the common connection point (PCC), STATCOM is mainly added to the PCC of photovoltaic power station. It can be regarded that the photovoltaic system and STATCOM constitute a whole and are integrated into the grid, and the unified coordination and optimization of the overall control system becomes particularly important. In this paper, the parameter tuning strategy of PI controller for photovoltaic grid-connected system with STATCOM is studied. Taking the optimal overall performance of DC capacitor voltage and PCC point voltage of photovoltaic inverters as the optimization objective, chaotic orthogonal particle swarm optimization algorithm is used to optimize the parameters of PI controller of the system, and simulation is carried out under the condition of voltage variation to verify the effectiveness of the optimization strategy.

Data mining and data driving of harmonic in AC arc furnaces based on functional analysis

This paper use big data technology, mine synchronous harmonic measuring data of AC arc-furnaces whole production process with functional analysis, verifies that harmonic current released from AC arc-furnaces is in independence and orthogonality approximately between each other. The discovered knowledge shows that multi-arc-furnaces harmonic current can be largely counteracted each other, If these AC arc-furnaces were connected to a PCC in which short-circuit capacity is enough for that the superposed harmonic current of AC arc-furnaces can be electromagnetic compatible, then power quality of the PCC can reach the qualified level discovered knowledge further reveals the model of AC arc-furnace, disorder data stream generated from harmonic measuring data is derived to calculation composition harmonic current at PCC(Point of Common Connection) in which AC arc-furnaces were connected.

A robust SMES controller strategy for mitigating power and voltage fluctuations of grid-connected hybrid PV–wind generation systems

Recently, hybrid generation systems (HGSs) are considered to be the optimal solution for supplying remote areas with the required electrical power. HGSs contain two or more renewable energy sources (RESs), such as wind power generators (WPGs), photovoltaic (PV) generation systems and the energy of the tides. Due to the intermittent nature of RESs, power and voltage fluctuations have appeared accordingly at the connection point with the utility power grid. Hence, energy storage technologies can play an effective role in mitigating power and voltage fluctuations caused by hybrid PV–wind generation systems. This paper proposes a robust control strategy for superconducting magnetic energy storage (SMES) combined with HGS. Fuzzy logic control (FLC) is used to control the chopper circuit of SMES in order to charge/discharge the active power from/to HGS. The proposed FLC strategy considers the fluctuations due to PV and wind power generation systems and the random load power variation. SMES with the proposed FLC method can effectively mitigate the fluctuation of active and reactive powers transfer between HGS and grid, and it can also regulate the voltage profile of the common connection point of SMES with HGS. Moreover, the system line power loss is clearly reduced by using the SMES system. The complete power system including loads is built in MATLAB/Simulink platform. The simulation results indicate that the proposed FLC–SMES can smooth both power and voltage fluctuations due to uncertain climate changes of PV and WPG systems.

Analiza i modelovanje pretvarača sa aktivnim ispravljačem i njegov uticaj na energetsku efikasnost elektromotornog pogona

The aim of this paper is to present, analyse and demonstrate the benefits of using an active bidirectional rectifier as a front end converter in the variable speed drive converter of an electric motor. The use of an active bidirectional rectifier allows for more advanced operation of the drive, in terms of current waveshape, energy recovery during braking or generating mode of the motor. Also the compensation of the reactive power of consumers connected to the same common point of connection to network can be performed with the active bidirectional rectifier of the proposed drive. In addition to the basic drive topology with an active rectifier and corresponding control mode, the experimental results and results of the simulation on the model are given in several operating points of case study plant.

두 개의 2차권선을 갖는 변압기형 한류기의 전류제한 특성

This paper analyzed the current limiting characteristics of a transformer type superconducting fault current limiter (SFCL) with two secondary windings. In case of having a common connection point in the secondary winding, the transient current limiting characteristics due to the double quench of the two models according to the installation location of the superconducting element were compared and analyzed. When the fault current magnitude is large, the fault current is limited by the occurrence of double quench in both models. In the previous SFCL with a common connection point, the quench time and the voltage generation interval time of the two superconducting elements were short, and the proposed SFCL confirmed that the instantaneous power and cumulative energy of the superconducting element were small.

Harmonic analysis of hybrid renewable microgrids comprising optimal design of passive filters and uncertainties

In this paper, the applications of passive filters in grid-connected and isolated hybrid renewable microgrid are addressed. The single-tuned filters are engaged to reduce the total harmonic distortion (THD) at the point of common connection with keeping total demand distortions below the maximum allowable limits. The total cost of proposed passive filters along with THD define the adapted bi-objectives to be minimized simultaneously provided that set of operating inequality constraints are satisfied. A multi-objective grasshopper optimization algorithm (MOGOA) is applied in this regard. The best answers are picked up carefully among the Pareto solutions by technique for order of preference by similarity to ideal solution (TOPSIS) procedures. Harmonic analysis is performed to examine the critical frequencies in many instants before and after installing passive filters. The effects of harmonics on the motor and wind generator torques are analysed and discussed. In addition, the system power factor is improved. Various scenarios regarding the operations of the grid under study are investigated comprising uncertainties of renewable power sources. The reductions in torque ripples of induction motor and wind turbine generator are indicated. It can be emphasized that the cropped results of filter’s cost along with THD generated by MOGOA are very competitive and convincing when they are compared to the results of the well-structure multi-objective genetic algorithm.

Voltage harmonic distortion compensation with non-linear load power sharing in low-voltage islanded microgrid

Microgrids are designed to operate at a fundamental frequency (50 or 60 Hz). However, certain types of loads generate voltage and/or current harmonics that increase power system heat losses. These harmonic losses reduce system efficiency, cause apparatus overheating and increase power costs. Besides that, the Distributed Generation (DG) is expected to play an important role in future power systems, since it is able to reduce losses, improve power quality to end users. In this paper we propose new harmonic droop controller to compensate the harmonic currents produced by each DG to feed the nonlinear loads. Furthermore, the proposed controller is able to damp the total harmonic distortion of the voltage at the common connection point (PCC). Modeling and simulations incorporate to define the best control parameters for a proper operation. Experimental results are given to show the efficiency of the proposed algorithm.

Comparative Study on Current Limiting Characteristics of Transformer-Type SFCL With Common Connection Point Between Two Secondary Windings

In this paper, the transformer-type superconducting fault current limiters (SFCLs) with common connection point between two secondary windings, which was similar structure to the previously suggested transformer-type SFCL with two triggering levels, was proposed and their current limiting characteristics were compared. The suggested transformer-type SFCLs consist of the primary winding and two secondary windings with common connection point. However, the current limiting operations through two triggering levels, which can be generally adjusted by the winding direction and the number of turns between two secondary windings, are affected by the application position of two high-T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> superconducting (HTSC) elements into the transformer type SFCL with common connection point. To analyze the dependence of the current limiting operation on the application position of two HTSC elements, the short-circuit tests for the transformer-type SFCL with two different positions of two HTSC elements were carried out and their current limiting characteristics were compared from the point of view of the power burden and the accumulated energy of two HTSC elements comprising each transformer-type SFCL.

Remote Power Control Injection of Grid-Connected Power Converters Based on Virtual Flux

Renewable Energy Source (RES)-based power plants need to control the active and reactive power at the Point of Common Connection (PCC) with the grid, in order to comply with the requirements of the Transmission System Operators (TSOs). This point is normally far away from the power converter station, and the cables and step-up transformers have a non-neglectable influence on the delivered power. In order to overcome this drawback, this paper presents a control algorithm that permits one to control remotely the power injected at the PCC, by adjusting the local controller of the Voltage Source Converters (VSCs). In this work, the synchronization with the grid is done based on the Virtual Flux (VF) concept. The results reveals that the VF estimation is able to produce a reliable estimation of the grid voltage in any point of the network, and makes it possible to calculate the necessary current reference for injecting a desired active and reactive power at a point that can be some kilometres away. In this paper the main principle for this remote power control is presented. Likewise, the simulation and experimental results will be shown in order to analyse the effectiveness of the proposed system.

A Power Flow Solution Technique for Autonomous and Non Autonomous Mode of Operation of Microgrid System

A power flow solution technique has been proposed for microgrid operating in isolated as well as grid-connected mode. The formulation is based on simple impedance matrix approach where the elements of the impedance matrix are the impedance of the power flow paths from the terminal loads to the node representing the point of common connection (PCC). Distributed generators in microgrid are modeled to operate either in droop controlled, P-V or P-Q mode. When connected to the grid, Distributed Generation (DG's) may be operated in any of the operating modes, but during autonomous operation, the droop controlled mode is followed. The bus interfacing the main and the microgrid has been chosen as a voltage regulated bus so as to facilitate seamless transfer from the autonomous to the grid connected mode of operation and vice-versa. Comparisons with existing methods are presented to show the accuracy and ability of the proposed method. Maintaining the PCC bus voltage at 1.0 p.u. helps to have an improved voltage profile and seamless transfer of the system between grid connected and islanded modes.

Estudio de la calidad de la energía en el punto común de conexión entre una red de baja tensión y un sistema solar fotovoltaico de 7.8 kWp

Este trabajo presenta, el estudio de los problemas de tensión originados en el punto común de conexión de una redexperimental de 1,000 kWh/mes de energía solar en la ciudad de Ibagué, Colombia. La red de baja tensión fue caracterizadade acuerdo con la NTC 5001e incluye aspectos como desequilibrio de tensión, intermitencia, flicker de cortoy largo plazo, fluctuaciones y harmónicos. La energía máxima producida por la fue de 850 kWh/mes, equivalenteal 72,65% de la capacidad instalada, con relación a las perturbaciones de larga duración se tuvo un incremento del2% con respecto al valor mínimo de la tensión registrada; el desequilibrio de tensión disminuye entre el 3.5 y el70% y los harmónicos de tensión (THD) aumentaron el 7% en la línea U1, 0.8% en la línea U2 y 3% en la línea U3.Los harmónicos de corriente no presentaron incrementos significativos en las líneas U2 y U3, la línea U1 registró unincremento del 22%. Los valores de flicker de corta y larga duración, las muescas de tensión (Notches) y las interrupcionesde larga duración no registraron diferencias significativas, la potencia activa y reactiva total se incrementaronen 58 y 42%, respectivamente. El estudio termográfico permite establecer un incremento de temperatura de7.5% después de la implementación de la red experimental. Se espera que la experiencia en el proyecto pueda servirde referencia en la aplicación de la ley 1715 del gobierno de Colombia para el aprovechamiento de la energía solar

Behavior of photovoltaic systems connected to the distribution network. Case study, photovoltaic power plants in the distribution network of the SDEE Mureș operator

Today, the stability of the power distribution system is influenced by the significant number of photovoltaic power plants connected to the electric distribution network. This paper aims to present the results obtained after about three years of operation of a photovoltaic plant of (2.5-3,2) MW in terms of voltage variation in the common point of connection, power quality. Also, will present results of photovoltaic power plant certification, environmental factors that contributed to the production of electricity, responsiveness to change in the scheme of operation of the electricity distribution network. The case study refers to a single 2.8 MW photovoltaic plant, but it will review the operation of two more plants 2,8 MW located in different geographical areas, but with the same power, type of inverters and photovoltaic panels from one supplier. The data obtained will be teaching material when designing and simulating the operation of a new photovoltaic power plant.

Управление устройством РПН сетевого трансформатора с учетом режимов работы электросталеплавильного комплекса

The paper presents the main results of developing and researching a new principle for controlling the step-down transformer on-load tap changer (OLTC), which coordinates the OLTC operation with the electrical parameters of the electric-arc steelmaker, compensators installed in the high-power and ultrahigh-power EAF power supplies, and the mains. The proposed principle consists in pre-determining the operating voltage ranges on the mains-transformer primary side for all OLTC tap positions taking into account the existing of both the electric-arc steelmaking facility and the mains. The static VAR compensator (SVC) control system is improved by adding a block for finding the mains-transformer OLTC tap position number so as to use new position-switching algorithms. The problem of optimizing the OLTC tap-position switching in mains-transformers supplying power to electric-arc steelmaking facilities under significant mains-voltage deviations is analyzed on the basis of evidence from three Russian steelworks companies. We herein discuss the particularities selecting the mains-transformer OLTC positions in two SVC control modes, one consisting in keeping zero consumption of reactive power from the mains, and the other one consisting in maintaining a coordinate voltage in the common EAF and SVC connection point. The effect of the proposed solutions is found from the results obtained by means of mathematical modeling of electric-arc steelmaking facilities in MATLAB Simulink. We discuss the options for further improvement of principles for coordinating the operation of automatic transformer-voltage regulators (AVR) with the parameters of steelmakers, compensators, and mains.

Power control of a doubly fed induction generator connected to the power grid

ABSTRACTIn this paper, the regulation control problem of the active and reactive power at the common connection point between a doubly fed induction generator and the grid is approached. The proposed controller is developed exploiting the passivity properties of the considered model for the control system. It is considered the existence of a wind turbine that delivers a time-varying torque to the generation unit which exhibits a highly nonlinear structure due to the variations of the wind speed. From a theoretical perspective, the main feature of the contribution lies in the fact that it is formally proved that the equilibrium point of the closed-loop system that corresponds to the desired power exhibits practical global asymptotic stability properties. This characteristic is obtained applying well-known theory from the perturbed nonlinear dynamical systems theory. However, in the numerical evaluation of the proposed controller, it is illustrated how these properties are indeed stronger since asymptotic stability is achieved.

C, H, Cl, and In Element Cycle in Wastes: Vacuum Pyrolysis of PVC Plastic To Recover Indium in LCD Panels and Prepare Carbon Coating

Resource recycling of millions of solid wastes is a world’s problems. Because element is the basic unit of all wastes, the essence of wastes recycling is to realize cycle of elements in wastes. In this paper, a new concept of element cycle in wastes is proposed. Under guidance of element cycle, various wastes have common connection point. The concept is clarified by a case of C, H, Cl and In element cycle from waste PVC plastic and LCD panels. In this paper, a vacuum pyrolysis of waste PVC was proposed to recycle indium in LCD and synchronously prepare carbon coating. Cl in PVC combined with In in LCD was mainly regenerated in the form of InCl3. Meantime, C and H in PVC were reused to prepare carbon coating and energy products, such as pyrolysis oil and gas. The recycling system means to change two kinds of wastes into resources by their own element characteristics. Under optimized conditions, recovery rate of indium exceeded 98 %. Meantime, with increasing temperature, microstructure of carbon coating is...

Flyback Cascaded Multilevel Inverter Based SHE-PWM Control for STATCOM Applications

This paper presents the closed loop DC-DC flyback converter with multi-level cascaded H-bridge inverter (MCHI) for transformer-less static synchronous compensator (STATCOM) system. The STATCOM system is proposed to be controlled using decoupled dq vector control incorporating the new reactive current reference algorithm and multi-level selective harmonic elimination pulse width modulation (MSHEPWM) technique. This ensures transient performance enhancement as well as simpler control and modulation technique implementation for dynamic systems. As the proposed MSHEPWM solely depends on adjustable DC-link voltage levels, flyback converter is designed for that purpose to suit wider applications. In current work, a single phase five-levels CHI based STATCOM system incorporated with the aforementioned converters are presented to compensate the reactive power (VAR) at the point of common connection (PCC). The dynamic as well as the transient performances of the developed STATCOM control system and the proposed voltage closed loop control of each converter are investigated to meet different VAR demands at balanced loading conditions. Simulation studies are performed to verify the effectiveness and theoretical analysis of the approaches presented.

Combining Frequency Containment Reserves and Renewable Power Leveling in Energy Storage Systems

The objective of this paper was to show that a combination of renewable energy sources with energy storage systems, which provide frequency containment reserves FCR (also called primary frequency control), improves the performance of both systems. This double benefit comes out in a reduction of intraday trading for the storage system and a leveled power injection of the renewables.Considering the regulations that apply for battery storage systems to provide FCR in Germany, interaction with other units is essential to guarantee availability of the system. This interaction is usually performed market based by intraday trading or by flexible power generation or consumption combined with the storage system. This paper, however, showed the benefits of interaction with fluctuating renewable energy sources.Energy storages and renewables were clustered to a common grid connection point to utilize the fluctuations of the renewable power generation directly for battery management. Simulation results based on sample photovoltaic and wind profiles showed the double benefit of the configuration. Intraday trading was reduced by 33% up to 57%. At the same time, fluctuations decreased, so the renewable power injection better matched a predefined power schedule.

Research on the Novel Non-Contact Power Supply System Tuning Methodology based on Fuzzy Neural Network Theory under the Random Load Condition

In this paper, we combine the literature review and technique reports to conduct research on the novel non-contact power supply system tuning methodology based on fuzzy neural network theory under the random load condition. Power supply by noncontact way could increase the flexibility of electrical equipment, eliminates the traditional power supply methods of safe hidden trouble and makes up for the traditional power supply methods because of the existence of electrical connections of the lack of divination. The background harmonic separation of qualitative method is detecting system side and user side common connection point for the size of the harmonic distortion effect. The genetic algorithm with adaptive system, cellular automata, chaos theory and artificial intelligence is considered for the next decade computing technology has a significant impact on the key technology which is adopted by our research to optimize the proposed system. Mathematical analysis and dynamic load change can lead to circuit reactance, so system will deviate from the resonance state. The experimental simulation proves the feasibility and robustness of our proposed methodology. In the near future, more related research will be conducted to optimize and modify the current method.

Border Collision of Three-Phase Voltage-Source Inverter System with Interacting Loads

As a commercial interface, three-phase voltage-source inverters (VSI) are commonly equipped for energy conversion to export DC power from most distributed generation (DG) to the AC utility. Not only do voltage-source converters take charge of converting the power to the loads but support the grid voltage at the point of common connection (PCC) as well, which is dependent on the condition of the grid-connected loads. This paper explores the border collision and its interacting mechanism among the VSI, resistive interacting loads and grids, which manifests as the alternating emergence of the inverting and rectifying operations, where the normal operation is terminated and a new one is assumed. Their mutual effect on the power quality under investigation will cause the circuital stability issue and further deteriorate the voltage regulation capability of VSI by dramatically raising the grid voltage harmonics. It is found in a design-oriented view that the border collision operation will be induced within the unsuitable parameter space with respect to transmission lines of AC grid, resistive loads and internal resistance of VSI. The physical phenomenon is also identified by the theoretical analysis. With numerical simulations for various circuit conditions, the corresponding bifurcation boundaries are collected, where the stability of the system is lost via border collision.

Real-time plug-in electric vehicle charging strategies for current and voltage unbalance minimization

Plug-in electric vehicles (PEVs) have been proposed as one of the solutions to reduce transportation dependency on oil. Nevertheless, if PEVs are introduced as a new load on the grid without any charging strategy, the grid's power quality will be deteriorated. Among the power quality parameters, current and voltage unbalances would be affected. This paper proposes a real-time strategy in order to minimize the current unbalance factor (CUF) caused by PEVs and housing on a common connection point (CCP) in a residential network. As a consequence of the CUF minimization, the voltage unbalance factor (VUF) is significantly reduced. The CUF at a CCP is formulated as a function of the loads in-phase and quadrature currents (PEVs and householders included). This objective function is minimized under maximum rating and charging priority constraints using algorithm Active-set. The minimization process is a part of the strategy which consists in adapting the optimization problem in real-time to changing conditions such as PEV's arrival and departure times, PEV's battery capacity variety, a random initial state-of-charge (SOC) and the householder's consumption. The strategy was tested on a low voltage network simulated on Matlab /Simulink. Results show that the current balance index is increased more than 400%, the voltage unbalance index is reduced 17% and some of the CCPs in the electric network simulated, are re-balanced (based on the EN50160 standard's definition) thanks to the CUF minimization.