The voltage source inverter for D-Statcom are constructed based on multi-level topologies, with or without use of a transformer. These type of solutions will provide support for operation with a high level of terminal voltage. For operation of D-Statcom converter it is possible to represent its PWM-controlled VSI with an instantaneous voltage source. The generating principle of instantaneous active & reactive power by D-Statcom a shown in Figure 3.In this, the currents and voltages are represented with instantaneous space vectors obtained using a power –in variant Clarke transform three cases are presented in figure 3: general one, for reactive power equal to zero and the active power equal to zero.
to their customers. PS especially distribution systems, have numerous non linear loads, which significantly affect the quality of power. Apart from non linear loads, events like capacitor switching, motor starting and unusual faults could also inflict powerquality (PQ) problems. PQ problem is defined as any manifested problem in voltage /current or leading to frequency deviations that result in failure or mal operation of customer equipment. Voltage sags and swells are among the many PQ problems the industrial processes have to face. Voltage sags are more severe. During the past few decades, power industries have proved that the adverse impacts on the PQ can be mitigated or avoided by conventional means, and that techniques using fast controlled force commutated power electronics (PE) are even more effective. PQ compensators can be categorized into two main types. One is shunt connected compensation device that effectively eliminates harmonics. The other is the series connected device, which has an edge over the shunt type for correcting the distorted system side voltages and voltage sags caused by power transmission system faults.
They are becoming more heavily loaded and are being operated in ways not originally envisioned. Transmission systems must be flexible to react to more diverse generation and load patterns. In addition, the economical utilization of transmission system assets is of vital importance to enable utilities in industrialized countries to remain competitive and to survive in developing countries, the optimized use of transmission systems investments is also important to support industry, create employment and utilize efficiently scarce economic resources. Flexible AC Transmission Systems (FACTS) is a technology that responds to these needs. It significantly alters the way transmission systems are developed and controlled together with improvements in asset utilization, system flexibility and system performance.
One of the most common power frequency disturbances is voltage sag. By definition, voltage sag is an event that can last from half of a cycle to several seconds. Voltage sags typically are due to starting on large loads, such as an electric motor or an arc furnace. Induction motors draw starting currents ranging between 600 and 800% of their nominal full load currents. The current starts at the high value and tapers off to the normal running current in about 2 to 8 sec, based on the motor design and load inertia. Depending on the instant at which the voltage is applied to the motor, the current can be highly asymmetrical.
by day due to world industrialization. To conserve fossil fuels for future generations distribution energy generations (DG) are the best alternative. Wind and PV plays a key role on renewable power generation. The powerquality is the main constraint while feeding power to distribution loads. In this paper DG are used to feed power to Unified PowerQuality Conditioner (UPQC) through a multi-level converter. The multilevel converter is used as shunt and series converters of UPQC, by using this converter the harmonic component presented in the output of the converter is redused compared to the conventional 2level converter output. Also reduces %THD presented on the fundamental value. Due to this the filter component requirement is less compared to conventional case. The inclusion of multilevel converters in UPQC can reduce the filtering requirement, power loss and reactive power consumed by the converter.
This paper has presented the powerquality problem such as total harmonic distortion in the distributionsystem and simulation technique of a D-STATCOM. The simulation results with different PWMs show that, by adding LCL Passive filter to D-STATCOM, the THD reduced within the IEEE STD 519-1992. The power factors may also increase close to unity. Thus, it can be concluded that by adding D-STATCOM with LCL filter and SVPWM the powerquality is improved and THD is reduced.
Powerquality problems in transmission and distribution systems. Among these, the D- STATCOM is one of the most effective devices. A new PWM-based control scheme has been implemented to control the electronic valves in the DSTATCOM. The D-STATCOM has additional capability to sustain reactive current at low voltage, and can be developed as a voltage and frequency support by replacing capacitors with batteries as energy storage. [6, 7]
When the power requirement is high, three phase inverters are used. When three single-phase inverters are connected in parallel, we can get the three-phase inverter. The gating signals for the three phase inverters have a phase difference of 120 o . These inverters take their dc supply from a battery or from a rectifier and can be called as six-step bridge inverter. Figure.2.2 shows the three phase inverter using six MOSFET’s and with diodes. A large capacitor is connected at the input terminals tends to make the input dc voltage constant. This capacitor also suppresses the harmonics fed back to the source. Therefore the Voltage Source Inverter is only buck (step down) inverter operation for DC to AC power conversion or boost (step-up) operation for AC to DC power conversion.
ABSTRACT: With the increase in use of electronic equipments there has been rise in problems related to powerquality. Powerquality deals with utilization of electric energy from the distributionsystem successfully without interference or interruption. The various powerquality disturbances are transients, interruptions, voltage sag, voltage swell, voltage collapse, harmonics etc. These powerquality related problems can be solved with the help of various custom power devices. Dynamic voltage restorer (DVR) is a custom power device used for the compensation of voltage sag and swell. It can provide the most commercial solution to mitigation voltage sag by injecting voltage as well as power into the system. In this paper an overview of DVR, its components, functions, compensating techniques and control methods are reviewed in detail and the compensating techniques are compared.
PowerQuality (PQ) has become an important issue to electricity consumers at all levels of usage. The PQ issue is defined as “Any power problem manifested in voltage, current, or frequency deviations that results in failure or misoperation of customer equipment.” The development of power electronic based equipment has a significant impact on quality of electric power supply. The switch mode power supplies (SMPS), dimmers, current regulator, frequency converters, low power consumption lamps, arc welding machines, etc, are some out of the many vast applications of power electronics based devices. The operation of these loads/equipments generates harmonics and thus, pollutes the modern distributionsystem. The growing interest in the utilization of renewable energy resources for electric power generation is making the electric powerdistribution network more susceptible to powerquality problems. In such conditions both electric utilities and end users of electric power are increasingly concerned about the quality of electric power.
In present day distribution systems (DS), major powerconsumption has been in reactive loads. The typicalloads may be computer loads, lighting ballasts, smallrating adjustable speeds drives (ASD) in airconditioners, fans, refrigerators, pumps and otherdomestic and commercial appliances are generallybehaved as nonlinear loads [9-10]. These loads draw laggingpower-factor currents and therefore give rise toreactive power burden in the DS. Moreover, situationworsens in the presence of unbalanced and non-linearloads, affect the quality of source currents to a largeextent. It affects the voltage at point of commoncoupling (PCC) where the facility is connected. Thishas adverse effects on the sensitive equipmentsconnected to PCC and may damage the equipmentappliances .
STATCOM and δ is the power angle. The reactive power output of the D-STATCOM inductive or capacitive depending can be either on the operation mode of the DSTATCOM. The construction controller of the D-STATCOM is used to operate the inverter in such a way that the phase angle between the inverter voltage and the line voltage is dynamically adjusted so that the D-STATCOM generates or absorbs the desired VAR at the point of connection. The phase of the output voltage of the thyristor-based inverter, V i , is controlled in the same way as the distributionsystem voltage, Vs.
Distributed Generation: A Nontechnical Guide. Tulsa, OK, USA: PennWell, 2001. The insights about Combined system for consonant concealment and receptive power pay can be clarified from  A. Luo, Z. Shuai, W. Zhu, and Z. J. Shen, "Consolidated system for symphonies concealment and responsive power remuneration," IEEE Trans. Ind .Electron., vol. 56, no. 2, pp. 418–428, Feb. 2009.the insights about Improvement of force quality utilizing versatile shunt dynamic channel can be clarified from  L. H. Tey, P. L. Thus, and Y. C. Chu, "Change of force quality utilizing versatile shunt dynamic channel," IEEE Trans. Control Del., vol. 20, no. 2, pp. 1558–1568, Apr. 2005.the insights around An on-line UPS system can be clarified from  A. Nasiri, Z. Nie, S. B. Bekiarov, and A. Emadi, "An on-line UPS system with control figure rectification and electric disconnection utilizing BIFRED converter," IEEE Trans. Ind. Electron., vol. 55, no. 2, pp. 722–730, Feb.2008. The insights about Robust model after control of parallel can be clarified by 6] M. Pascal, G. Garcer'a, E. Figures, and F. G. Esp'ın, "Strong mode following control of parallel UPS single-stage inverters," IEEE Trans. Ind. Electron., vol. 55, no. 8, pp. 2870–2883, Aug. 2008.
analysis similarity can prevail the good essence when b = 12 and d = 10. Though the estimation method, the FOS may be approximated as the very eminent integer-order system. A fractional-order integration can be obtain changing the sign of order ( ). Hence, the range of for integration is 0< <1. The structure of FOPI controller is shown in Fig. 4. for design a controller the Kp element, are individually designed and place in the structure show in Fig. 4.
In Fig. 1 a section of distributionpowersystem is shown, this system contains residential houses, the photovoltaic system connected by interfacing inverters and control system configuration. To explore the mentioned power grid, it is better to start with residential loads, it is obvious that various kinds of non-linear loads are being inserted in power grids and most of these loads are related to home appliance, computers and power electronic based devices. The residential grid model that is shown in Fig. 1 is a combination model of several devices to show the effects of non-linear loads and harmonic compensators on an electrical powersystem. To have a detailed vision of these devices, a CFL and a PC are selected as a sample of non- linear loads and the harmonic components of these devices are analyzed in Table 3. It is worth noting that the provided data are taken from [9, 10] in which the harmonic current of different home appliances are measured practically.
Powerquality is defined as the ability of electrical equipment to consume the energy being supplied on it. The powerquality has been important issues for consumers of electricity at entire level of usages in electrical powersystem. Powerquality problem demonstrated in frequency, voltage or current deviation and may result into increased power losses, failure of equipment and malfunctioning of equipment. The wide use of non-liner load such as power electronics based equipment such as switch mode power supplies (SMPS), frequency converters, arc welding machines, variable frequency drives (VFD), single phase converter and three phase converter-rectifier has been substantial effect on powerquality in electrical powersystem. When non-linear load are connected to the powersystem it produce voltage or current harmonics, reduce power factor, reactive power related problem, Voltage sag and swell in distributionsystem. Voltage sag, voltage swell and current harmonics are the most common PQ problem. Voltage sag and swell can cause equipment failure, malfunctioning and data loss. Current harmonics can harm the live system and other customers connected to the system [1-4].
Various operating conditions are analyzed and tested. The devices presented have shown great performance in mitigating the disturbances and improve the power factor is unity and also enhance the powerquality . It can be deduced from the results obtained that DVR clears the voltage instability and restores system voltage much better than D-STATCOM. Exchange of reactive power between these devices while compensating and mitigating the voltage sags and swells forced the DC link voltage to vary continuously. The coupling transformer gives the improved system stability .
A new language was developed to describe the fuzzy properties of reality, which are very difficult and sometime even impossible to be described using conventional methods. Fuzzy set theory has been widely used in the control area with some application to dc-to-dc converter system. A simple fuzzy logic control is built up by a group of rules based on the human knowledge of system behavior. Matlab/Simulink simulation model is built to study the dynamic behavior of dc-to-dc converter and performance of proposed controllers. Furthermore, design of fuzzy logic controller can provide desirable both small signal and large signal dynamic performance at same time, which is not possible with linear control technique. Thus, fuzzy logic controller has been potential ability to improve the robustness of dc-to-dc converters. The basic scheme of a fuzzy logic controller is shown in Fig 5 and consists of four principal components such as: a fuzzy fication interface, which converts input data into suitable linguistic values; a knowledge base, which consists of a data base with the necessary linguistic
The system is simulated by powersystem blocks set of Simulink software. The simulation model has been presented in Figure 7. Since there is a transformer with maximum of two secondary windings in Simulink, the transformer with several secondaries shown in Figure 6, three transformers have been used where their primaries are in parallel. In order to connect the transformer terminals to each other, multi-output and multi- input bus bar blocks have been employed. The semiconductor switches have been also modeled by an ideal switch block. Since the overall performance of an electronic tap-changer is
This paper has presented a novel method to improve the powerquality at point of common coupling (PCC) for a 3-phase 4- wire DG system using fuzzy logic control for grid interfacing inverter. The grid interfacing inverter is effectively utilized for power conditioning. This approach eliminates the additional power conditioning equipment to improve powerquality at PCC. Simulation results analysis has shown that the proposed controller has fast response, high accuracy of tracking the DC-voltage reference, and strong robustness to load sudden variations