Top PDF Comparison of Power Quality Improvement by D STATCOM and Distributed Generation in Distribution System

In this Paper, the operation and control of single phase DGsources are considered in a three-phase utility connected grid. The single phase sources are operated to deliver available maximum power generated while the rest of the power demands in each of the phases are supplied by utility (and if available, three phase DG sources). The imbalance in three phase power is compensated two ways –either through a DSTATCOM or through a DG-compensator. A DSTATCOM can compensate for unbalances and nonlinearities, while providing reactive power support. The size of the dc capacitor determines how much reactive power support the DSTATCOM can provide without any drop in voltage. The choice of this capacitor is thus a trade-off between the reactive support and system response. Alternatively a three phase DG-compensator can be connected at the PCC to share the real and reactive power with utility and to compensate for the unbalance and nonlinearities in the system. The efficacy of the compensation is validated through extensive simulations and calculation of THD With the proposed structure of distribution system, it is possible to operate single phase DG sources in a utility connected grid and this might become a useful tool as their penetration in distribution systems increases.

Abstract— Now a day’s Improvement of Power quality has become a major area of concern in electrical power system. Increased sensitive and sophisticated loads results nonstandard voltage, current and frequency and reduce quality of power. This nonstandard power results failure of the loads connected to the distribution systems. Thus it has been very important to improve the quality of power which is very severe for the industrial customers as it can cause malfunctioning of several sensitive electronic equipments. Voltage quality is the major problem which is very severe for the sensitive electronic equipments. This paper describes voltage quality improvement by using Dynamic Voltage Restorer (DVR) and Distribution Static Synchronous Compensator (D-STATCOM). DVR or D-STATCOM is a custom power device (CPD), which is connected in series or in shunt with the network to maintain flat voltage profile in electrical distribution system. This paper presents modelling and simulation of DVR and D-STATCOM in MATLAB SIMULINK. Switching or triggering signals for the switching devices are provided by PI controller and discrete PWM generator which are used to control the output of DVR and D- STATCOM. Simulation result shows the performance of DVR and D-STATCOM under various faults such as single line to ground fault (LG), double line to ground fault (LLG), three phase to ground fault etc. The simulation result shows DVR is more efficient than D-STATCOM for power quality improvement.

In this paper we have modeled and analyzed the PV (photovoltaic) power system is being integrated with D- Statcom to low voltage power distribution grid at consumer end to compensate the harmonics coming from grid side inverter and other side we have different loads in that, most of the unbalanced nonlinear loads injects harmonic currents to source side and effects the source current. By using D-Statcom, the source current does not effect. In this, we have studied and analyzed the operation and performance of D-statcom at unbalanced non linear load condition and also gives the comparison by using with and without D-statcom. This proposed model is implemented using MATLAB SIMULINK software and the obtained resultant waveforms are evaluated and system stability effectiveness and power system performance have been established.

This paper analyzes the key issues in the Power Quality problems, as one of the prominent power quality problems, the origin, consequences and mitigation techniques of voltage sag problem has been discussed in detail. The STATCOM is applied to regulate transmission voltage to allow greater power flow in a voltage limited transmission network, in the same manner as a static var compensator (SVC), the STATCOM has further potential by giving an inherently faster response and greater output to a system with depressed voltage and offers improved quality of supply. The FACTS controllers are shown in Fig.1.The main applications of the STATCOM are; Distribution STATCOM (D-STATCOM) exhibits high speed control of reactive power to provide voltage stabilization and other type of system control. The DSTATCOM protects the utility transmission or distribution system from voltage sag and /or flicker caused by rapidly varying reactive current demand. During the transient conditions the D-STATCOM provides leading or lagging reactive power to active system stability, power factor correction and load balancing and /or harmonic compensation of a particular load [6,7].

Power quality is one of major concerns in the present era. It has become important, especially, with the introduction of sophisticated devices, whose performance is very sensitive to the quality of power supply. Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure of end use equipments. One of the major problems deal here is the harmonics reactive power compensation and power factor. The influence of the wind turbine in the grid system concerning the power quality measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operation and these are measured according to national/international guidelines. As a promising renewable alternative, the wind power is one of the significant source of generation. Reactive power compensation and harmonic reduction in a low voltage distribution networks for integration of wind power to the grid are the main issues addressed in this paper. The paper study demonstrates the power quality problem due to installation of wind turbine with the grid. In this proposed scheme STATIC COMPENSATOR (STATCOM) is connected at a point of common coupling with a PV energy system to mitigate the power quality issues. The PV energy system is integrated to sustain the real power source under fluctuating wind power. The STATCOM control scheme for the grid connected wind energy generation system for power quality improvement is simulated using MATLAB/SIMULINK.

In this case speed of wind turbine is not constant. Speed of wind turbine is varies than automatically speed of generator is also continuously varies. Result of this condition is output of wind generator is not constant. So this situation wind power generation system (WPGS) is not possible to interface the electrical grid, because power quality problem occurs in the point of common coupling (PCC). We use novel idea using FACT devices and interface wind energy source to grid, proposed system FACT devise use as STATCOM. STATCOM is use for absorption of current and injection of reactive current at point of common coupling. As compare to other FACT devises STATCOM is less cost, faster in operation, small size and ability to provide active and reactive power. Control schemes reported in the literature for controlling of the STATCOM are synchronous reference frame (SRF) theory, current compensation using DC bus regulation, instantaneous reactive power(IRP) theory, a scheme based on the neural network technique. Out of all these techniques most commonly used the theories are synchronous reference frame (SRF) theory and instantaneous reactive power (IRP) theory.In this paper MATALAB based simulation of the STATCOM is carried out using instantaneous reactive power (IRP) theory for compensation of the reactive power, unbalance, reducing total harmonic distortion (T.H.D) and improving power factor of the system.

In a battery-based controller is proposed for control of voltage and frequency in the isolated WECS. However, maximum power tracking (MPT) could not be realized in this battery-based isolated system employing SCIG operated at fixed speed. In Singh et al. have proposed an electronic load controller for VFC at the stator terminals, and the controller transfers excess power from the hydropower generator to a dump load, whenever the load is less than the generated power. In this paper, a new three-phase four- wire autonomous (or isolated) wind–small hydro hybrid system is proposed for isolated locations, which cannot be connected to the grid and where the wind potential and hydro potential exist simultaneously.

In this paper a STATCOM based control technology has been proposed for commercial wind turbines for improving the power quality which can technically manage the power level associated with it. The proposed STATCOM control scheme for grid connected wind energy generation for power quality improvement has following objectives. Unity power factor at the source side, Reactive power support only from STATCOM to wind Generator & Load and Simple bang-bang controller for STATCOM to achieve fast dynamic response. The latest wind turbine generating systems are installed with pulse controlled inverters. Due to the improvement in switching techniques, the voltage and current at the point of common connection can be made in sinusoidal form and at unity power factor to improve the power quality at PCC.

The area of power quality must improve and fulfil the requirement of customers is necessary, so the devices are used for improve poor power quality and increase the satisfaction result of customers side. So the devices used for this purpose are called ―Customer Power Devices‖, in past time the capacitor banks are used for improvement of power quality but now a days new technology are used like FACTs devices, The FACTs devices are used to improve the power quality in electrical side. The STATCOM is used in distribution side is called D-STATCOM,. D-STATCOM can give good response which depends upon its energy storage capacity. If selection of energy storage device is of feasible value then it give good response but it also increases the rating of storage device so it increases the cost of storage device. So for this reason some researcher use external storage devices like super capacitor, BESS, flywheel generator, SMES etc. but it has also some problem. So the objective is to make an arrangement of capacitors which can reduce the problem of external storage devices and gives a better response without compromise system parameters. Because we can reduce the cost of system and also rating of storage device for D-STATCOM.

A voltage source converter (VSC) is a power electronic device that connected in shunt or parallel to system. It can generate a sinusoidal voltage with any required magnitude, frequency and phase angle. It also convert the dc voltage across storage devices into a set of three phase ac output voltage. It is also capable to generate or absorb reactive power. If the output voltage of the VSC is greater than ac bus terminal voltages, is said to be in capacitive mode. So, it will compensate reactive power through ac system. The type of power switch used is an IGBT. Three phase four leg VSI is modelled in Simulink by using IGBT.

DC-link voltage unbalance is one of the major limitation in cascaded inverter-based STATCOM. In this paper, a simple static var compensating scheme is proposed for a cascaded two-level inverter-based multilevel inverter. This scheme ensures regulation of dc- link voltages of inverters and reactive power compensation. The performance of the scheme is validated by simulation under different conditions. The operation of the control system developed for the STATCOM in MATLAB/SIMULINK for maintaining the power quality is simulated. Further, the cause of distortions in the injected reactive current is investigated, so Fuzzy ruled based control strategy is used. By using this Fuzzy control technique distortion factor is decreased in the reactive current waveform. Hence we can stabilize the transmission systems by improving power quality (PQ) in distribution systems and decreasing total harmonic distortion factor.

The power disturbances occur generally in all the system. Power issues remains a vital problem while considering any electronics devices as its sensitivity will changes as the load changes, which impact to the power generation and transmission , distribution system. A power voltage spike can damage valuable components. Power quality encovers a wide range of disturbances mainly such as voltage sag, swells, flickers, harmonic distortion, interruption invariant transitions. In simple words we can say that PQ is the set of electrical boundaries that allows a part of the equipment to be work in an intended manner with any losses. Custom power devices mainly work on the better regulation with zero interruptions. This paper aims at the development of the diode-clamped multi-level D-STATCOM and DVR for power quality enhancement. A controller is used to provide better voltage stabilization, sag/swell suppression and power quality factor

The inverter is the heart of the PV system and is the focus of all utility-interconnection codes and standards. A Solar inverter or PV inverter is a type of electrical inverter that is made to change the direct current (DC) electricity from a photovoltaic array into alternating current (AC) for use with home appliances and possibly a utility grid. Since the PV array is a dc source, an inverter is required to convert the dc power to normal ac power that is used in our homes and offices. To save energy they run only when the sun is up and should be located in cool locations away from direct sunlight. The PCU is a general term for all the equipment involved including the inverter and the interface with the PV (and battery system if used) and the utility grid. It is very important to point out that inverters are by design much safer than rotating generators. Of particular concern to utility engineers is how much current a generator can deliver during a fault on their system. Inverters generally produce less than 20% of the fault current as a synchronous generator of the same nameplate capacity. This is a very significant difference.

Traditionally, power system distribution networks have been passive networks with a unidirectional power flow from the high voltage levels to customers at lower voltages. The presence of distributed generation makes the distribution networks active networks, with the possibility of power production at local level. Distributed generation is an approach that employs small scale power generation located on the distribution system close to the point of consumption. Distributed generation technologies often consist of renewable energy generators and offer a number of potential benefits. In comparison to distributed generation, centralized power models require distribution from the center to outlying consumers. This requires transmission across the distance. This system has many disadvantages such as emission of greenhouse gases, production of nuclear waste, inefficiency, power losses etc. Many of these issues can be mediated through distributed energies.

The power quality issues can be viewed with respect to the wind generation, transmission and distribution network, such as voltage sag, swells, flickers, harmonics etc. However the wind generator introduces disturbances into the distribution network. One of the simple methods of running a wind generating system is to use the induction generator connected directly to the grid system. The induction generator has inherent advantages of cost effectiveness and robustness. However; induction generators require reactive power for magnetization. When the generated active power of an induction generator is varied due to wind, absorbed reactive power and terminal voltage of an induction generator can be significantly affected. A proper control scheme in wind energy generation system is required under normal operating condition to allow the proper control over the active power production. In the event of increasing grid disturbance, a battery energy storage system for wind energy generating system is generally required to compensate the fluctuation generated by wind turbine. A STATCOM-based control technology has been proposed for improving the power quality which can technically manages the power level associates with the commercial wind turbines. The proposed STATCOM control scheme for grid connected wind energy generation for power quality improvement has following objectives.

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 distribution system voltage, Vs.

The power quality are not completely mitigated due to high cost of new feeders and controlled compensation of reactive power. A D-STATCOM (distributed static shunt compensator) are used for the mitigation of voltage sag as well as voltage stability, voltage flicker reduction. This paper consists a D-STATCOM with passive LCL filter and connected to 11kv distribution system in parallel or in shunted. The D-STATCOM also improve the power quality like as low power factor and harmonic distortion. In this paper section I represent introduction of test system. Section II describes the power quality issues such as voltage sag/swells. Section III represents modelling and principle of operation for the test system. Fuzzy logic control technique, system implementation and simulation results are discussed in the section IV,V and VI respectively.

In this research the D-STATCOM realizes positive sequence admittance and negative-sequence conductance to regulate positive- sequence voltage as well as suppress negative-sequence voltage. In the modern era each and every country mainly concentrates on saving the energy in best and possible way in limited number of resources and also to draw maximum output from it. Due to increasing demand in the power sector there are number of non linear loads increasing. There is need of more and more Distributed generation system in congestion with Transmission and Distribution system (TDS) and also expansion of Smart Grid System. The expansion of grids requires the generation of electricity in few large units and should be concentrated. If there is any fault in Grids then the effect will be larger and uncontrollable. To avoid this special reserves are developed called “Spinning Reserve”. This protects against any single generating plant to fail, connected in the grid. The enormous amount of electrical energy transmitted from source to consumer end so there will be loss of energy during transmission. The loss of energy depends on the configuration of the network connected to the transmission and does not affect the distributed system. The distribution losses are different from the transmission losses and they are separately measured. It has the major drawback of the cogeneration or common heat and power transfer of energy. To overcome this, small generating units are installed spread throughout the network and the whole system is decentralized known as Distributed generation system. DGS has the ability to draw the energy from convention sources as well as Renewable sources. It is also gaining the importance in rural electricity. With the installation of DGS the transmission losses are reduced to a large extent in the case of Renewable energy DGS. But non-renewable DGS are not able to access the advantage attained in Renewable. The rising demands of energy made us to think alternative sources of energy. The need of electricity is more in rural areas. Our major portion of agriculture is mainly depended on the electricity, without it the use of new technology cannot be adopted. These are possible by following two methods:

39 A literature review has been performed on different types of studies over D-STATCOM. The D-STATCOM is highly effective in providing load voltage regulation; however, maintaining load voltage at rated value has several unwanted effects from customer point of view. With voltage of 1p.u. at load point, D-STATCOM forces load to operate always at rated power. The STATCOM used in distribution systems is called D-STATCOM (Distribution- STATCOM). It can exchange both active and reactive power with the distribution system by varying the amplitude and phase angle of the converter voltage with respect to the line terminal voltage.

The control of a DG framework has been enhanced with proficiency, high unwavering quality and power thickness and less multifaceted nature. A consistent and adaptable ongoing arrangement has been proposed to deal with key issues identified with power quality. Parametric results highlight the viability and approval of the approach in which framework level power quality has been progressed. The fundamental commitment of this paper is to total up various methodologies proposed to deal with power quality issues in conveyed era systems and to give an examination between progressive methodologies utilizing different reproductions for consolidated framework.