Grid power quality improvement,emergency preparedness plan for nurses,movies in post apocalyptic world - 2016 Feature

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This paper presents a grid interfacing inverter which compensates power quality problems and also interface Renewable Energy Sources with the help of electric grid.
Power Quality Improvement of Grid Interconnection of renewable Energy Based Distribution System S. THE green house gases (such as co2 ) absorbs the infrared radiation (IR) and confine the heat in the earth’s atmosphere.primarly, these gases emissions comes from the combustion of fossil fuels based on used energy. Extending use of power electronics based equipment and non-linear loads at PCC generate harmonic currents may weakening the PQ. The method of current harmonics reduction reduces passive LC filters which are simple and low cost. The duty ratio of inverter switches are varied in a power cycle such that the combination of load and Thus the output of dc-link voltage regulator results in an active current Im.
Power quality refers to electricity that consistently meets the agreed-upon specifications for optimal and efficient use in home electronics. Power factor, which measures how much of the electricity delivered is actually useable by customers.
Voltage and power factor, in particular, are very dependent on how many customers are on an electrical line, and how much they are using. Today’s modern and sensitive electronics demand a steady voltage and frequency, a considerable change from electronics in the 1960s. More information and the ability to manage voltages in real-time allow utilities with Smart Grid technology to operate their electrical grid within tighter tolerances. Sign up for our monthly e-newsletter and receive new information on the smart grid, technologies and benefits for you. Renewable Energy Sources are being increasingly connected in distribution system utilizing power electronic converters. Due to the wide spread use of non-linear loads significant amounts of harmonic currents are being injected into power systems.
However, these filters have drawbacks as well like large size, tuning and risk of resonance problems.
This inverter is known as ?Grid interfacing inverter? and this is incorporated with active power filter functionality to control the performance of malfunction device. SYSTEM INTERPRETATION Fig.1 shows the proposed system consists of RES connected to the dc-link of a grid-interfacing inverter. DC-Link Voltage and Power Control Operation The power generated due to the intermittent or irregular nature of RES is of variable nature. Control Scenario Fig.4 shows the control diagram of grid- interfacing inverter for a 3-phase 4-wire system. The multiplication of active current component (Im) with unity grid voltage vector templates (Ua, Ub and Uc) generates the reference grid currents (in*) is put to zero, being the instantaneous sum of balanced grid currents the grid synchronizing angle (?) is obtained from phase locked loop (PLL) is used to generate unit vector template. In North America, home appliances and electronics are designed to operate within a range of 106 volts to 127 volts of alternating current (AC). Higher than normal voltage causes electronic equipment to operate inefficiently, and may even cause damage to certain equipment.
Like other digital devices, they include a transformer to step down voltage for the digital electronics.
The impact of these fossil fuels encouraged to find alternative energy sources to the fossil fuels. These harmonic currents flows through the power systemimpedance which causes harmonic currents to be drawn by other loads connected at PCC. As harmonic pollution is severe in power networks, power system engineer developed dynamic and adjustable solutions to the power quality problems. As voltage source inverter interfaces the renewable energy source to the grid and delivers the generated power, it is considered as a key element of DG system. The dc- link plays an important role in transferring this power from renewable energy source to the grid.
Low voltage has similar impacts, and may cause equipment to work erratically or not at all, like when you turn on your vacuum and your lights dim momentarily.This is especially true of digital electronic equipment such as computers and TVs. Also like other digital devices, they are engineered to meet strict FCC requirements to keep from interfering with other electronic or communications equipment.Smart meters allow your utility to see what the actual voltage delivered to your home is. The sharing of active power between Thus, the power injected into the grid from the WFconverters is managed through the common DC link.
The power buffer concept may be implemented using speed condition, the power fluctuation frequency is f = 3.4a D-Statcom, but not using a DVR. The fuzzy logic can be used in many applications especially, when the process/models are complex to analyse by using classical methods. Devaraju2 Pursuing M.Tech in SreeVidyanikethan Engineering College, Tirupati, Andhra Pradesh, India. The persistence of current and voltage harmonics in power system increases losses in the lines, decrease the power factor and may cause timing errors in sensitive electronic equipment’s.


Renewable Energy Sources are entitled as current sources connected to the dc-link of a grid-interfacing inverter. Digital equipment relies on low-voltage (usually around 5 volts) direct current to operate. Before smart meters, utilities would base their equipment settings on voltage readings at an electric substation and engineering estimates of what that would mean for actual voltage at each customer’s home. On the other and, voltage Hz, and the amplitude of the resulting voltage variation atregulation during relatively large disturbances, cannot be PCC, expressed as a percentage is 1.50%.
Balanced 3-phase non-linear loads such as motor drivers, silicon controlled rectifiers (SCR), large uninterruptible power supplies (UPS) produce harmonic currents and voltages which are positive- sequence harmonics like 7th, 13th, etc. Usually the variable speed wind turbines generate power at variable ac voltage but the fuel cell and photovoltaic energy sources generate power at variable low dc voltage. The given control approach compensates harmonics, unbalance, and neutral current when the load connected to PCC is non-linear or unbalanced or the combination of both.
This situation forced the revision of grid event that changes occur in its mechanical speed, ie due to connection code requirements, to guarantee the reliability wind disturbances, so will the WF active (reactive) power in systems with high wind power penetration.
This voltageeasily coped using reactive power only from D-Statcom; in fluctuation is seen in middle curve of Fig. Simulations are carried out using MATLAB/SIMULINK to verify the performance of the controller.
As the utility of high penetration of intermittent RES in distribution systems constitute a threat to network in terms of stability,voltage regulation and power quality issues , DG systems are required to act in accordance with technical and regulatory frame works to protect secure, reliable and cost-effective operation of overall network. Thus the power generated from these renewable sources need power conditioning before connecting to dc-link.
2 shows the structured representation of power transfer from the RES to the grid through dc-link.
These injected(demanded) into the power grid, leading to strategies were implemented using a Unified Power Quality variations of WF terminal voltage because of system Compensator (UPQC). The output shows the controller has fast dynamic response high accuracy of tracking DC voltage reference and robust to load parameters variations. Abstract This paper presents a grid interfacing inverter which compensates power quality problems and also interface Renewable Energy Sources with the help of electric grid. Hence DG systems can be actively controlled to enhance the system operation with improved power quality at PCC[2].
Single phase non-linear loads such as switch-mode power supplies in computer equipment produce produce harmonic currents and voltages which are third order zero- sequence harmonics, triplen harmonics like 3rd, 9th, 15th, 21st, etc. The dc- capacitor allows independent control of converters on either side of dc-link and decouples the RES from the grid [6]. As a result of these factors, utilities strive to keep the voltage that’s delivered to your house within the standard range. Unlike positive and negative- sequence harmonic currents, triplen harmonic currents do not cancel but add arithmetically at the neutral bus. These power disturbances propagate into the generators connected to a weak grid system, including a power system, and can produce a phenomenon known as detailed UPQC compensator was developed on simulation “flicker”, which consists of fluctuations in the illumination software. This result’sthe neutral current that touches magnitudes as high as 1.73 times the phase current. This means that even in normal operation, the WF impacts negatively on the System Power Quality. In addition to the risk of cables and transformers overheating, the third harmonic can recede energy efficiency [3]. Also, the normal connected to the grid, is necessary to employ the last operation of WF is impaired due to such disturbances. At t = 3.0??the active and reactive power pulsations are attenuated because the P and Q controllers come into action.
Barbosa, “Investigac? ?ao dos Modelos de Circuitos de Sincronismo Trif?asicos Baseadosna Teoria das Pot?encias Real e Imagin?aria Instantaneas (p–PLL e q–PLL)”, In: Proc. Custom power devices technology (CUPS) particular for the case of “weak grids”, the impact is even result very use full for this kind of application.
UPQC: controller generates both voltages commands ????_?????(??)? The UPQC is utilized for simultaneous ?compensation of the load current and the voltage disturbance and ????_?????(??) based on power fluctuations ??? and ??? , respectively. 6 Power Buffer Control As can be observed in the upper curve, the series converter requires negligible power to operate, while the III. In order to reduce the voltage fluctuations that may internal control scheme of the UPQC device was developed cause “flicker”, and improve WF terminal voltage to regulate the voltage in the WF terminals, and to mitigate regulation, several solutions have been posed. Normally the UPQC has two voltage mean power from the instantaneous power measured insource inverters of three-phase four-wire or three-phasethree-wire configuration. S IMULATION RESULTS AND DISCUSSION shunt converter demands a high instantaneous power level The model of the power system scheme illustrated from the capacitor when compensating active powerin Fig. The internal control common one is to upgrade the power grid, increasing the strategy is based on the management of active and reactive short circuit power level at the point of common coupling power in the series and shunt converters of the UPQC, and PCC, thus reducing the impact of power fluctuations and the exchange of power between converters through UPQC voltage regulation problems [5]. The mean values of active and reactive power are obtained by low–pass filtering, and the bandwidth of suchinverter is connected through transformers between the filters are chosen so that the power fluctuation componentssource and the common connection point.


12 is seen [12] International Electrotechnical Commissionshunt and series converter active power behavior. The other inverter, selected for compensation, fall into the flicker band as statedcalled the shunt inverter is connected in parallel through the ?transformers. Numerical simulations wereperformed to determine and then compensate voltagefluctuation due to wind power variation, and voltageregulation problems due to a sudden load connection. This approach increases the compensation technological development of high power electronics capability of the UPQC with respect to other custom devices has led to implementation of electronic equipment strategies that use reactive power only. Simulations results suited for electric power systems, with fast response show the effectiveness of the proposed compensation compared to the line frequency.
These active compensators strategy for the enhancement of Power Quality and Wind allow great flexibility in: a) controlling the power flow in Farm stability. This control loop will not interact with the fluctuating powerThe UPQC has compensation capabilities for the harmoniccurrent, the reactive power compensation, the voltage compensation, because its components are lower indisturbances, and the power flow control. 7 Simulink diagram for UPQC Sub system The DC-bus has voltage level limitations in accordance with the VSI’s operational characteristics. As the fluctuating active power is handled by the capacitor, its value needs to be selected so that the “ripple” in the DC voltage is kept within a narrow range. Aredes “Instantaneousand is clearly seen the VDC control action power theory an applications to power conditioning”, John Wiley & Sons, 2007. INTRODUCTION compensation strategy using an UPQC, for the case of The location of generation facilities for wind SCIG–based WF, connected to a weak distribution powerenergy is determined by wind energy resource availability, grid. 11 Power of the capacitor in the DC–Bus At t = 0.5?? begins the cyclical power pulsationproduced by the tower shadow effect. This system is taken from a real case [7].often far from high voltage (HV) power transmission gridsand major consumption centers [1]. As was mentioned, thetower shadow produces variation in torque, and hence in theactive and reactive WF generated power. CONCLUSION In this paper, a new compensation strategyimplemented using an UPQC type compensator waspresented, to connect SCIG based wind farms to weakdistribution power grid. In case of facilities withmedium power ratings, the WF is connected throughmedium voltage (MV) distribution head-lines.
The proposed compensation schemeenhances the system power quality, exploiting fully DC–busenergy storage and active power sharing between UPQCconverters, features not present in DVR and D–Statcomcompensators. A situationcommonly found in such scheme is that the power generatedis comparable to the transport power capacity of the powergrid to which the WF is connected, also known as weak gridconnection. 5 Series Compensator Controllermaintain the WF terminal voltage at nominal value (see U1bus-bar in Fig.4), thus compensating the PCC voltage In summary, in the proposed strategy the UPQCvariations. The simulation results show a goodperformance in the rejection of power fluctuation due to“tower shadow effect” and the regulation of voltage due to asudden load connection. The main feature of this type of Connections are the increased voltage regulationsensitivity to changes in load [2]. In this way, the voltage disturbances coming can be seen as a “power buffer”, leveling the power injectedfrom the grid cannot spread to the WF facilities. So, the effectiveness of theproposed compensation approach is demonstrated in thestudy case.
So, the system’s ability toregulate voltage at the point of common coupling (PCC) tothe electrical system is a key factor for the successful Fig.
The Fig.6 illustrates aeffect, this control action may increase the low voltage ride– conceptual diagram of this mode of operation. Also, is well known that given therandom nature of wind resources, the WF generates The UPQC is controlled to regulate the WFfluctuating electric power. It must bethrough (LVRT) capability in the occurrence of voltage sags remarked that the absence of an external DC source in thein the WF terminals.
These fluctuations have a terminal voltage, and to mitigate voltage fluctuations at thenegative impact on stability and power quality in electric point of common coupling (PCC), caused by system loadpower systems. Fig.5 shows a block diagram of the UPQC bus, forces to maintain zero–average power in theseries converter controller. The using the UPQC series converter, by voltage injection “inoperation of SCIG phase” with PCC voltage. Rodriguez “Transient stability of a fixed speed wind farm” Renewable Energy 28, 2003 pp.1341–1355[3] P. Ledwich “Power Quality Enhancement Using Custom Power Devices” Kluwer Academic Publisher, 2002.



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Comments to “Grid power quality improvement”

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