Abstract— the concept of electric spring (ES) has been proposed recently as an effective means of distributed voltagecontrol. The idea is to regulate the voltage across the critical (C) loads while allowing the noncritical (NC) impedance-type loads (e.g., water heaters) to vary their power consumption and thus contribute to demand-side response. In this paper, a comparison is made between distributed voltagecontrol using ES against the traditional single point control with STATic COMpensator (STATCOM). For a given range of supply voltage variation, the total reactive capacity required for each option to produce the desired voltage regulation at the point of connection is compared. A simple case study with a single ES and STATCOM is presented first to show that the ES and STATCOM require comparable reactive power to achieve similar voltage regulation. Comparison between a STATCOM and ES is done. In both cases, it turns out that a group of ESs achieves better total voltage regulation than STATCOM with less overall reactive power capacity. Dependence of the ES capability on proportion of critical and NC load is also shown.
In this paper, a comparisonis made between electricsprings (ES) and static compensator (STATCOM). A comparison is made between distributed voltagecontrol using ES againstthe traditional single point control with STATic COMpensator(STATCOM) by using fuzzy logic controller. Here we are using fuzzy logic controller instead of using other controllers. For a given range of supply voltage variation, thetotal reactive capacity required for each option to produce thedesired voltage regulation at the point of common coupling (PCC) connection is compared.In this paper, it turns out that a group of ESsachieves better total voltage regulation than STATCOM with lessoverall reactive power capacity. Dependence of the ES capabilityon proportion of critical and NC load is also shown. Simulation was done by using MATLAB/Simulink software under various critical and NC loads.
To investigate the opposite effect of what was described in the previous subsection, the voltage across the loads is reduced by increasing the reactive power absorption of the renewable source. This is to test the ability of an ES and a STATCOM to support the voltage and regulate it at the nominal value. At t = 1.0 s, the reactive power absorption by the intermittent renewable source is increased from 467 to 1100 VAr. Without any voltagecontrol, the load voltage is seen to drop from the nominal value of 216 V to slightly below 190 V as shown by the green trace in Fig. 5(a) and (b).As before, both STATCOM and ES are able to restore the voltage across the C load back to the nominal value as shown by the overlapping blue and red traces in Fig. 5(b). The ES achieves this by injecting about 150 V in series with the NC load the voltage across which drops to about 150 V as shown by the blue traces in Fig. 5(a) and (c). In order to suppress the voltage, both ES and STATCOM inject reactive power (as indicated by negative sign of Q) into the system as shown in Fig. 5(d) with ES requiring to inject about 150 VAr less
stage point in series with the line to control dynamic and receptive power flows on the transmission line. Along these lines, this inverter will trade dynamic and responsive power with the line. The responsive power is electronically given by the series inverter, and the dynamic power is transmitted to the dc terminals. The shunt inverter is worked so as to request this dc terminal power (positive or negative) from the line keeping the voltage over the capacity capacitor Vdc steady. In this way, the net genuine power consumed from the line by the UPFC is equivalent just to the losses of the inverters and their transformers. The remaining limit of the shunt inverter can be utilized to trade responsive power with the line so to give a voltage direction at the association point. The two VSI's can work independently of each other by separating the dc side. So all things considered, the shunt inverter is operating as a STATCOM that generates or ingests responsive energy to manage the voltage extent at the association point. Instead, the series inverter is operating as SSSC that generates or ingests responsive energy to control the present flow, and hence the power low on the transmission line. The UPFC has numerous conceivable operating modes. Specifically, the shunt inverter is operating in such an approach to inject a controllable current, ish into the transmission line. The shunt inverter can be controlled in two unique modes:
motor drive can be reduced. Furthermore, CM voltage can be eliminated by using advanced modulation strategies such as that proposed in . ● Input current: Multilevel converters can draw input current with low distortion. ● Switching frequency: Multilevel converters can operate at both fundamental switching frequency and high switching frequency PWM. It should be noted that lower switching frequency usually means lower switching loss and higher efficiency. Unfortunately, multilevel converters do have some disadvantages. One particular disadvantage is the greater number of power semiconductor switches needed. Although lower voltage rated switches can be utilized in a multilevel converter, each switch requires a related gate drive circuit. This may cause the overall system to be more expensive and complex.
implementation of the first generation of ES (i.e. ES-1) with capacitive storage have been reported. By working under inductive and capacitive mode, ES-1 is capable of regulating the mains voltage to its nominal value in the presence of intermittent power injected into the power grid. With input voltagecontrol, ES can work with non-critical loads that have high tolerance of voltage fluctuation (e.g. with operating voltage range from 180 V to 265 V for a nominal mains voltage of 220 V). Examples of the non-critical loads are thermal loads such as ice-thermal storage systems, electric water heater systems, air-conditioning systems and some public lighting systems.The first version of ES provides only reactive power compensation for mains voltage regulation and simultaneously varies the non-critical load power so as to achieve automatic power balancing within the power capability of the ES and its associated non-critical load. This arrangement allows ES-2 to work in eight different operating modes and to provide both active and reactive power compensation. It also enables ES-2 to perform extra tasks such as power factor correction and load compensation. The first and second versions of ES are illustrated in (a) and (b), respectively. With many countries worldwide determined to decarbonize electric power generation within the next few decades, new concerns about power system stability have arisen from the increasing use of intermittent renewable energy sources. Due to the distributed and intermittent nature of renewable energy sources, such as wind and solar energy, power companies will find it impossible to instantaneously predict and control the total power generation in the entire power grid. Future smart grid requires a new control paradigm that the load demand should follow power generation, which is just opposite to existing control method of power generation following load demand.
A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. There are a large number of spring designs; in everyday usage the term often refers to coil springs. Small springs can be wound from pre- hardened stock, while larger ones are made from annealed steel and hardened after fabrication. Somenon-ferrous metals are also used including phosphor bronze and titanium for parts requiring corrosion resistance and beryllium copper for springs carrying electrical current (because of its low electrical resistance). The concept of electric spring (ES) has been proposed recently as an effective means of distributed voltagecontrol. The idea is to regulate the voltage across the critical (C) loads while allowing the noncritical (NC) impedance- type loads (e.g., water heaters) to vary their power consumption and thus contribute to demand-side respons.
The electric spring is a new demand side management technology  . It can provide electric active suspension functions for voltage and frequency stability in a distributed manner for future smart grid . The subtle change from output voltagecontrol to input voltagecontrol of a reactive power controller makes the electric spring suitable for future smart grid applications. For the compensation of neutral current, a new three-phase ES topology is proposed and its operating principle is explained. Its ability to enhance the power system stability and its use for reducing neutral current in a three-phase power system is demonstrated in a simulation study. The effectiveness of the proposed system under different load conditions are also verified in the simulation study.
Thus, beside voltagecontrol, the power consumed by the noncritical load is also modulated according to the input power resulting in frequency regulation.ES can also lower the energy storage requirements by up to 50% . Capacitor in the ES, replaced with batteries on the DC side improve the power quality in the distribution system . As the grid is very sensitive, connected equipment cannot tolerate the fluctuations beyond certain limits. Renewable energy, that is intermittent in nature, if directly connected to the grid may lead to the voltage collapse. So it is necessary to limit the voltage fluctuations in energy source. The reactive power and thereby voltage variations in the distribution lines can be controlled by ES thereby improving the stability of the system .The electric spring can be used as current controlled voltage source, that boost the voltage to a required level in case of voltage dip across critical loads and suppresses the excess voltage during over voltage.
As explained in the aforementioned Section, the unbalance phenomena of the rectifying current in the proposed converter are influenced by the gain difference of each converters’ resonant network. When the input voltage of the converter is fixed, the unbalance problem cannot be solved using the conventional PFM controller because of the limitations of individual control capability for each converter, which means the same switching frequency for all converters. If another controller is able to control the output voltages of bridgeless PFCs, the difference of the resonant gain can be compensated by adjusting input voltages of each converter. In addition, this method can control each output rectifier current passing through the output filter capacitors in the Y-connected rectifier.
Today, Transmission networks of modern system are becoming increasingly stressed because of growing demand and restrictions on building new lines. One of the consequences of such a stressed system is threat of losing stability following a disturbance. Flexible ac transmission system (FACTS) devices are found to be every effective in stressing a transmission network for better utilization of its existing facilities without sacrificing the desired stability margin. STATCOM, employ the newly technology of power electronic switching devices in electric power transmission systems to controlvoltage and power flow and play an important role as a stability aid for and transient disturbances in an interconnected power systems. During the last decade, a number of control devices under the terms FACTS technology have been proposed and used. Among all FACTS devices, static synchronous compensators (STATCOM) plays great role in reactive power compensation and voltage support because of its altercative steady state performance and operating characteristics.
controlled series capacitor (TCSC) is one of the practical devices that can improve the implementation of FACTs . Actual line voltage and current information is quite important TCSC control scheme. However, voltage and current unbalance produced by an electric railway load causes serious TCSC control errors. This problem can influence system stability. In particular, a voltage and current unbalances after fault will cause further problems. FACTS:
As the parallel operation of multiple generators is a promising solution for the MEA EPS, appropriate power sharing among the different power sources needs to be carefully considered. From the communication point of view, overall control of DC systems can be divided into three categories: distributed control, centralized control and decentralized control . In terms of centralized control, not only a centralized controller is required to send commands to individual modules but also communication links from each parallel module to the centralized controller are needed , . Under this circumstance, system failure can occur if communication fails. Distributed control does not need a central controller but communication links among the parallel units are essential , . It overcomes the disadvantage of centralized control: single point failure (central controller, communication links), but the performance is still degraded by the communication delays. Alternatively, appropriate power sharing can also be achieved by employing droop control, a decentralized control method which relies on local measurements and control , . If the outage of one module occurs, the remaining modules can still contribute to power sharing according to their local droop settings. Thus, the system reliability is increased. Since communication links among the sources and additional centralized controller are not needed, each parallel module can work independently relying on the local measurements and controllers. Therefore, higher system modularity and lower cost can be achieved as well under droop control. Due to the abovementioned advantages, a droop-based solution is an attractive choice for the DC EPS.
The reference current generator allow to generate three currents of trapezoidal shapes and phase shifted relative to each other by an angle equal to 120 ° electrical. This three phase currents are out in phase with electromotive forces to minimize consumption and is amplitude controlled the speed controller. Three control loops are used to generate current in the three reference voltages of the motor. The model reference current generator is implanted under the environment of Matlab / Simulink as shown in according to the following figure 8 :
Contextualizing Figure 1, in a future perspective of integrating smart homes as crucial part of smart grids, the operation of some of the electrical appliances are on/off controlled according to the energy management and the user comforts and conveniences (however, they can also be managed by the smart grid). In order to realize this controllability by the user, these electrical appliances require two fundamental things for a properly operation: power and an internal communication in the smart home. Since the EV is plugged-in at the smart home, in case of power outages, it can provide uninterrupted power for the electrical appliances according to the battery state-of-charge (determined by the internal management system of the EV, but the information is available for the user through the EV interface or even through APPs), the user preferences and the electrical appliances (cf. section I). In this context of EV-home interaction, some control strategies can be delineated as soon as a grid fault occurs, without prejudice to the operability of the home and with advantages for the EV. In order to prevent a fully battery discharging, some of electrical appliances can be turned-off at the same time of the power outage occurrence (e.g., heating systems or secondary lights), but others not (e.g., internal communication system, main lights, or the alarm system). The criteria to select the electrical appliances supplied by the V2H mode as UPS are established by the smart home energy management (which are previously established based on the user convenience). In a comprehensive and real overview of the V2H implementation in a smart home, this selection can be made automatically by the system and can be changed by the user, i.e., the priority inherent to each electrical appliance can be defined by the user according to their convenience (e.g., according to the seasons or weekdays and weekends). In addition, the priority of each electrical appliance differs from home to home. As these issues are related to the communication and energy optimization aspects of smart homes, this article discards addressing these issues, focusing only on the operation of
Abstract— Secondary distribution system is generally Three Phase Four Wire system which is directly connected to consumers. Due to the unbalanced configuration of these networks, a net current flowing through the neutral conductor. The presence of increasing number of non linear loads also causes significant neutral current in the system. The nonlinear loads draw harmonic and reactive components of current from ac mains. The excess neutral current and harmonics are the serious issues as they deteriorate the overall performance of distribution systems. The proposed strategy employs a new three phase Electric Spring circuit for reducing neutral current and a Hysteresis Current Controller for eliminating harmonics from the system. MATLAB/SIMULINK software platform is used for simulation. The application of the proposed method has been investigated for different load conditions and the results are presented.
The objective of this project is to moniter and control the cosine angle between the voltage and current in order to save the electric energy.This project is very useful in the industries where heavy inductive loads are used.If the powerfactor is less than unity the line current is greater and increases the KVA demand.This attracts penalty imposed by Electricity Board.
According to Table 8, about 37% of energy consumption in line 5 of Tehran Metro is of reactive power type, which is stored or leaked in heat transfer or leakage flux in the induction reactance of overhead network and traction load. The presence of reactive power in the network is necessary for initial loading, and also by the nature of the electric charge, but its high consumption rate is unacceptable and it consumes a significant part of the capacity of the power systems which may, in the long run, reduce the life of the equipment and increase the cost of depreciation and maintenance activities of the equipment. It should be noted that the high reactive power supply through the overhead system increases the network flow and decreases the voltage range, which also increases the losses in the traction systems. On the other hand, optimization of automation of line 5 power distribution systems (SCADA) for remote control, the amount of consumption, and consumption readings, prepares the ground for management of the network residual value, and the possibility of optimizing switching processes in the overhead power supply network. Ensuring operations in Line 5 power distribution systems relies on data communication systems of telecommunication and data channels, which should enhance the performance of telecommunication systems in this segment and improve automation of energy control operations. There are several ways to improve network efficiency and reduce losses caused by electrical energy distribution systems. Moreover, excessive consumption of reactive power causes voltage drop and voltage fluctuations in the overhead network. Since high drop in overvoltage triggers the traction circuits of the trains, performing any compensating action
The global energy shortage has directly obstructed the economic, social, developing nations and environments by Green House Gases and by receiving carbon credits. The growing demand for power across the globe is being forecasted and projected to be exponential. Lack of quality with out-of-date network infrastructure, climate change, increasing fuel costs, has resulted in ineffective and progressively unstable electric system. With the growing challenge of electrical power, Quality of service and continuity of supply has been the maximum importance for all major power utility sectors across the world. Smart Grid is predominantly proposed as the major growth in connecting communication and information technologies to enhance grid reliability, and to enable incorporation of various smart grid resources such as renewable energy, electric storage (Battery storage, Vehicle-to-Grid (V2G) storage,… etc.) and electric transportation. Power system may be consisting of single generator or it may have interconnected areas consisting of many generators. The latter is the normal power system. Interconnected System is a big electrical network which is divided into groups known as control areas and each control area corresponds to the portion of the grid owned by a single utility. Lines joining different control areas are known as tie-lines. With the expansion of non-conventional energy coming from resources as wind and sun, there is huge increase in the number of distributed generations. These non-conventional energy sources are of random nature, specifically wind energy, the energy storage systems of decent number needed greatly to make such resources dependable. The power network assembly turns out to be more complex with the connection of energy storage system and distributed generation to the grid.
Main advantage of MCVS with shaping the output voltage waveform in electric machine is overlapping electric machines with different number of pole pairs on one magnetic core, which allow providing no sliding contacts and increasing reliability of the system. Introduction of additional components that operate in feedback circuit carry out excitation of generator, stabilization of magnitude and frequency of the output voltage via two channels: control of excitation and of the converter circuit. Ability to control the amplitude modulation percentage in wide range allows achieving good power factors of MCVS with high quality of the output voltage waveform.