Evaluation of a Multilevel Cascaded-Type Dynamic Voltage Restorer Employing Discontinuous Space Vector Modulation

ABSTRACT:

In this paper, the use of a multilevel cascaded inverter as a dynamic voltage restorer (DVR) is explored. Two intermittent staggered space vector regulation (SVM) systems are executed for DVR control and are appeared to diminish inverter exchanging misfortunes while keeping up for all intents and purposes indistinguishable consonant execution from the ordinary staggered SVM at a high number of levels. This paper additionally shows a numerical relationship for registering the bending at the purpose of basic coupling (PCC) as a component of the mutilation of the DVR. This empowers the determination of the quantity of levels required for a specific application. An all-inclusive hang span bolster contrasted with the two-level DVR is another favorable position of the DVR with a multilevel cascaded inverter. The basic mode voltage (CMV) at the PCC has been assessed for the three SVM strategies (the regular staggered SVM and the two spasmodic SVM), introducing a lower CMV for the second broken SVM. A structure precedent is displayed for a 11-kV 5-MVA DVR multilevel cascaded inverter for up to 17 levels, utilizing the ordinary staggered SVM and the two irregular SVM methods.

 

BLOCK DIAGRAM:

Fig. 1 Proposed DVR in a distribution system.

 

EXPECTED SIMULATION RESULTS:

Fig.2 Load and DVR voltages employing conventional SVM.

Fig 3. Load and DVR voltages employing DB1 SVM.

Fig. 4. Load and DVR voltages employing DB2 SVM.

Fig.5. Load and DVR voltages employing conventional SVM at L = 1 mH.

Fig.6 Load and DVR voltages employing conventional SVM at L = 0 mH.

 

 CONCLUSION:

Notwithstanding encouraging transformer-less DVR task and decreasing separating necessities with the staggered DVR, contrasted with the two-level DVR, the primary commitment of this paper, to the DVR staggered fell inverter, can be condensed as pursues.

1) Reduced exchanging misfortunes can be acquired utilizing broken SVM while keeping up for all intents and purposes indistinguishable consonant execution from the traditional staggered SVM at a high number of levels.

2) The staggered DVR consonant execution has been assessed from the perspective of PCC up to 17 levels for various voltage droop profundities (beforehand, the consideration has been arranged to assess the DVR yield voltage symphonious execution).

3) Multilevel fell sort DVR can bolster an all-encompassing list length contrasted with the two-level DVR.

4) The CMV at the PCC has been assessed for the three SVM systems (the customary staggered SVM and the two intermittent SVM) for up to 17 levels and for various droop profundities, exhibiting a lower CMV for the second spasmodic SVM. The principal broken SVM method presents the most astounding CMV.

Artificial Neural Network (ANN) based Dynamic Voltage Restorer for Improvement of Power Quality

ABSTRACT:

Dynamic Voltage Restorer (DVR) is a custom power gadget utilized as a successful arrangement in shielding touchy burdens from voltage aggravations in power dissemination frameworks. The productivity of the control system, that directs the exchanging of the inverters, decides the DVR effectiveness. Corresponding Integral-Derivative (PID) control is the general method to do that. The power quality rebuilding capacities of this controller are constrained, and it produces critical measure of music – all of which comes from this straight procedure’s application for controlling non-direct DVR. As an answer, this paper proposes an Artificial Neural Network (ANN) based controller for improving rebuilding and sounds concealment abilities of DVR. A point by point examination of Neural Network controller with PID driven controller and Fuzzy rationale driven controller is additionally represented, where the proposed controller exhibited unrivaled execution with a unimportant 13.5% Total Harmonic Distortion.

 

CIRCUIT DIAGRAM:

Fig. 1 Simulation model for sag mitigation with ANN controller.

  

EXPECTED SIMULATION RESULTS:

Fig.2 Three phase sag mitigation based on ANN controlled DVR. (a) Instantaneous voltage at stable condition; (b) Instantantaneous voltage when sag occurs; (c) Voltage required to mitigate voltage sag; (d) Output voltage of the inverter circuit; (e) Generated PWM for inverter; (f) Instantaneous voltage after voltage restoration.

Fig 3. Restored Voltage Using (a) PID controller; (b) Fuzzy controller; (c) ANN controller; (d)THD comparison: the least THD can be seen at ANN based DVR, the range of the harmonics is also truncated by a huge amount by this method.

 

CONCLUSION:

DVRs are a famous decision for upgrading power quality in power frameworks, with a variety of control framework on offer to drive these gadgets. In this paper, utilization of ANN to work DVR for giving preferable execution over existing frameworks to relieve voltage list, swell, and music has been illustrated. Issue articulation and hypothetical foundation, structure of the proposed strategy, preparing system of the ANN utilized have been portrayed in detail. Recreation results demonstrating the DVR execution amid voltage droop have been exhibited. Examination of the proposed technique with the well known PID controller, and nonlinear Fuzzy controller has been completed, where the proposed ANN controller showed up as the best choice to reestablish framework voltage while alleviating THD to the best degree.

Power Quality Improvement and Low Voltage Ride through Capability in Hybrid Wind-PV Farms Grid-Connected Using Dynamic Voltage Restorer

ABSTRACT:

The paper proposes the utilization of a Dynamic Voltage Restorer (DVR) to upgrade the power quality and enhance the low voltage ride through (LVRT) capacity of a three-stage medium-voltage organize associated with a cross breed dissemination age (DG) framework. In this framework, the photovoltaic (PV) plant and the breeze turbine generator (WTG) are associated with a similar purpose of normal coupling (PCC) with a touchy load. The WTG comprises of a DFIG generator associated with the system by means of a stage up transformer. The PV framework is associated with the PCC by means of a two-organize vitality transformation (DC-DC converter and DC-AC inverter).

This topology permits, first, the extraction of most extreme power dependent on the gradual inductance method. Second, it permits the association of the PV framework to the general population matrix through a stage up transformer. Likewise, the DVR dependent on Fuzzy Logic Controller (FLC) is associated with the equivalent PCC. Diverse blame condition situations are tried for enhancing the productivity and the nature of the power supply and consistence with the necessities of the LVRT framework code. The aftereffects of the LVRT ability, voltage dependability, dynamic power, responsive power, infused current, and DC connect voltage, speed of turbine and power factor at the PCC are given and without the commitment of the DVR framework.

 

BLOCK DIAGRAM:

Fig. 1. The system configuration of PV/wind hybrid power system.

EXPECTED SIMULATION RESULTS:

FIGURE 2: Voltage phase magnitude at PCC during faults with typical LVRT and HVRT characteristics requirements of Distributed Generation Code of Germany as an example.

FIGURE 3: Voltage phase magnitude at PCC during sag fault.

FIGURE 4: Voltage phase magnitude at PCC during short circuit fault

FIGURE 5: Phase voltage at PCC during sag fault.

FIGURE 6: DVR voltage contribution at PCC during sag fault.

FIGURE 7: Phase voltage at PCC during short circuit fault.

FIGURE 8: Total active power of hybrid system at PCC injected to grid.

FIGURE 9: PV active power at PCC injected to grid.

FIGURE 10: Wind active power at PCC injected to grid.

FIGURE 11: Total reactive power of hybrid system at PCC injected to grid.

FIGURE 12: PV reactive power at PCC injected to grid.

FIGURE 13: Wind reactive power at PCC injected to grid.

FIGURE 14: Total PV-WT current injected to grid at PCC.

FIGURE 15: PV current injected at PCC.

FIGURE 16: WT current injected at PCC to grid.

CONCLUSION:

The reproduction examine was completed utilizing MATLAB to show the viability of the proposed DVR control framework to enhance the power quality and LVRT ability of the half and half PV-WT control framework. The framework has been tried under various blame condition situations. The outcomes have demonstrated that the DVR associated with the PV-Wind cross breed framework at the medium voltage network is extremely viable and can relieve voltage blackouts and short out disappointment with enhanced voltage direction abilities and adaptability in the amendment of the power factor.

The consequences of the reenactment additionally demonstrate that the framework structured is secure since the required voltage ranges are regarded accurately and the DG generators work dependably. The primary favorable position of the proposed structure is the fast recuperation of voltage; the power motions overshoot decrease, control of rotor speed and keeping the framework from having a DC connect overvoltage and consequently expanding the solidness of the power framework as per LVRT prerequisites.

Dual-function PV-ECS integrated to 3P4W distribution grid using 3M-PLL control for active power transfer and power quality improvement

ABSTRACT:

This study proposes a single-stage solar photovoltaic energy conversion system (PV-ECS) integrated to a three phase four-wire (3P4W) distribution grid with dual-function capabilities, i.e. active power transfer and power quality (PQ) enhancement at the point of interaction (PoI). The PV-ECS system comprises of a solar photovoltaic array and a voltage source inverter (VSI), supplying active power (during daytime) to the distribution grid and connected single-phase and three-phase loads. Apart from transfer of power, the system also improves the PQ at the PoI by compensating reactive power and neutral current, attenuating harmonics, correcting power factor and balancing grid currents. During night, the VSI acts as a shunt active power filter mitigating PQ issues, thereby increasing the device utilisation factor. A three-phase magnitude-phase locked loop (3M-PLL) method is utilised to extract and estimate fundamental term of load currents and an incremental conductance algorithm is applied for maximum power point tracking. To demonstrate its effectiveness, the system is modelled and its performance is simulated on MATLAB and experiments are performed on a developed prototype in the laboratory.

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:


Fig. 1 System configuration and control scheme

(a) Structure diagram of 3P4W grid-connected PV-ECS

 EXPECTED SIMULATION RESULTS

Fig. 2 Dynamic behaviour of system at

(a), (b) Unbalanced load, (c) Step increase in irradiance from 700 to 1000 W/m2

 CONCLUSION:

A dual-function single-stage PV-ECS integrated to the 3P4 distribution grid has been proposed here. Two modes of operation of PV-ECS are to supply and transfer active power to the grid and tied loads as well as to improve quality of power at PoI. An In  Cbased approach is utilised here for tracking MPP of solar PV array and a 3M-PLL-based control scheme is utilised for extracting  fundamental components of load current. Simulated and test results have demonstrated the performance of the system under various conditions such as non-linear loading, unbalanced loading and varying irradiance levels. Test results have shown that the system has improved the power quality at the PoI by compensating neutral current and reactive power, correcting power factor and balancing loads on the grid side. The harmonics are reduced to below 5% on grid side, which is within the limits of an IEEE-519 standard. Moreover, test results have indicated that the system has operated suitably during night-time (sunlight unavailability) thereby increasing the utilisation factor of the VSI by two-fold. The single stage structure has decreased the losses in the system and increased the total efficacy of the system.

REFERENCES:

[1] Muro, M., Saha, D.: ‘Why rooftop solar – and full retail feed in tariffs – benefits all consumers’, 30 May 2016. Available at http:// reneweconomy.com.au/2016/rooftop-solar-net-metering-is-a-netbenefit- 28170

[2] Meza, E.: ‘India implements new 40 GW rooftop, small PV plant program’, 20 May 2016. Available at http://www.pv-magazine.com/news/details/beitrag/ india-implements-new-40-gw-rooftop–small-pv-plant-program-_100024678/ #axzz4ADc3MIV6

[3] Deo, S., Jain, C., Singh, B.: ‘A PLL-less scheme for single-phase grid interfaced load compensating solar PV generation system’, IEEE Trans. Ind. Inf., 2015, 11, (3), pp. 692–699

[4] Yang, Y., Blaabjerg, F., Wang, H., et al.: ‘Power control flexibilities for grid connected multi-functional photovoltaic inverters’, IET Renew. Power Gener., 2016, 10, (4), pp. 504–513

[5] Agarwal, R., Hussain, I., Singh, B.: ‘LMF based control algorithm for single stage three-phase grid integrated solar PV system’, IEEE Trans. Sust. Energy, 2016, 7, (4), pp. 1379–1387

 

Improved control algorithm for gridconnected cascaded H-bridge photovoltaic inverters under asymmetric operating conditions

ABSTRACT:

Here, a single-stage cascaded H-bridge (CHB) inverter is presented for grid-connected photovoltaic (PV) systems. The CHB inverter has separate DC links and allows individual control of PV arrays. The conversion efficiency is high and the harmonic generation is lower than conventional PV inverters. Although the CHB inverter is a good candidate for injection of solar power into grid, its control issues have not been completely solved. One of the main challenges in the CHB inverter is the harmonic generation when the connected PV arrays to the H-bridge cells have different amounts of insolation. This study deals with the asymmetrical operating conditions of PV arrays (or H-bridge cells) in the CHB inverter and presents an analytical equation for determination of cells’ modulation indices based on PV arrays data. Then, a control loop is added to the tracking algorithm of conventional control systems to determine whether an H-bridge cell is in the linear modulation or not. In the case of overmodulation, the corresponding DC link voltage is increased by the controller to bring it back to the linear region. The validity of new method is confirmed by simulations and experiments on a seven-level 1.7 kW CHB inverter.

 

SOFTWARE: MATLAB/SIMULINK

  

BLOCK DIAGRAM:

Grid-connected PV inverter based on the CHB inverter

Fig. 1. Grid-connected PV inverter based on the CHB inverter

 

EXPECTED SIMULATION RESULTS:

 Injected current to grid

Fig. 2. Injected current to grid

(a) By the presented algorithm ,(b) By the proposed strategy in this paper

Fig. 3. Evaluation of proposed control system behaviour before and after applying the new strategy (a) Modulation indices, (b) Modulating waveforms, (c) Arrays DC link voltages and reference values, (d) Total injected power to the grid

Fig. 4. Dynamic behaviour of the proposed control system under change of irradiance level of the first PV array

 

Fig. 5. Dynamic behaviour of the proposed control system under grid voltage swell and non-uniform distribution of irradiances

 

CONCLUSION:

In this paper, a modified control strategy was proposed for the CHB inverter in the grid-connected PV applications. Based on the circuit analysis, a mathematical relation was derived for determination of cells’ operating conditions in the CHB inverter. This relation shows the value of cells’ modulation indices based on the PV system data. Accordingly, a modified control strategy was proposed to extend the operating range of the CHB inverter under heavy mismatching conditions. In this method, the condition of each H-bridge is checked continuously and when a cell enters to the overmodulation region, its voltage is gradually increased to bring it back to the linear region. This modification helps to prevent the interruption of CHB inverter due to extra harmonic generation in the overmodulation region. The proposed method can be easily applied to the already existing control systems to increase their operating range under asymmetric conditions.

 

REFERENCES:

  • Kouro, S., Malinowski, M., Gopakumar, K., et al.: ‘Recent advances and industrial applications of multilevel converters’, IEEE Trans. Ind. Electron., 2010, 57, (8), pp. 2553–2580
  • Bedram, A., Davoudi, A., Balog, R.S.: ‘Control and circuit techniques to mitigate partial shading effects in photovoltaic arrays’, IEEE J. Photovolt.,2012, 2, (4), pp. 532–546
  • Hajizadeh, M., Fathi, S.H.: ‘Fundamental frequency switching strategy for grid-connected cascaded H-bridge multilevel inverter to mitigate voltage harmonics at the point of common coupling’, IET Power Electron., 2016, 9, (12), pp. 2387–2393
  • Kouro, S., Leon, J.I., Vinnikov, D., et al.: ‘Grid-connected photovoltaic systems: an overview of recent research and emerging PV converter technology’, IEEE Ind. Electron. Mag., 2015, 9, (1), pp. 47–61
  • Oliveira, F.M., Oliveira da Silva, S.A., Durand, F.R., et al.: ‘Grid-tied photovoltaic system based on PSO MPPT technique with active power line conditioning’, IET Power Electron., 2015, 9, (6), pp. 1180–1191

Control of Solar Photovoltaic Integrated Universal Active Filter Based on Discrete Adaptive Filter

ABSTRACT:

In this work, a novel technique based on adaptive filtering is proposed for the control of three-phase universal active power filter with a solar photovoltaic array integrated at its DC bus. Two adaptive filters along with a zero crossing detection technique are used to extract the magnitude of fundamental active component of distorted load currents, which is then used in estimation of reference signal for the shunt active filter. This technique enables extraction of active component of all three phases with reduced mathematical computation. The series active filter control is based on synchronous reference frame theory and it regulates load voltage and maintains it in-phase with voltage at point of common coupling under conditions of voltage sag and swell. The performance of the system is evaluated on an experimental prototype in the laboratory under various dynamic conditions such as sag and swells in voltage at point of common coupling, load unbalancing and change in solar irradiation intensity.

 

KEYWORDS:

  1. Power quality
  2. Universal active power filter
  3. Adaptive filtering
  4. Photovoltaic system
  5. Maximum power point tracking
  6. Quadrature signal generation

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

Fig.1 System Configuration of Solar Photovoltaic Integrated Unified Active Power Filter 

  

EXPECTED SIMULATION RESULTS

 

Fig.2 Salient Signals in Series Active Filter Control

Fig.3. Salient Signals in Extraction of Fundamental Positive Sequence Load Current using Adaptive Filter

Fig. 4. Steady State Per Phase Signals of PCC and Load Side in a PV-UAPF Compensated System

Fig. 5. Performance of PV-UAPF Under Three Phase Short Circuit Fault

CONCLUSION:

The performance of adaptive filter based PV-UAPF system under both steady state and dynamic conditions have been analyzed in detail. The method of sampling the fundamental component of load current obtained through adaptive filter enables fast extraction of fundamental active component of nonlinear load currents for all phases in one sampling. Only two adaptive filters are required to extract magnitude of active component of three phase load currents. This technique requires reduced computational resources while achieving good dynamic and steady state performance in extraction of fundamental active component of nonlinear load current. The system performance has been found to be satisfactory under various disturbances in load current, PCC voltage and solar irradiation. The series active filter is able to regulate load voltage at 220 V under variations of PCC voltage from 170 V to 270 V. The grid   current THD is maintained at approximately 3% even though the THD of load current is 28% thus meeting requirement of IEEE-519 standard. The PV-UAPF system has been able to maintain the grid currents balanced under unbalanced loading condition. The proposed topology and algorithm are suited for employing in conditions where PCC voltage sags/swells and load current harmonics are major power quality issues. Certain power quality issues not addressed include voltage distortions, flicker, neutral current compensation etc. This power quality issues can be addressed by modification of topology and control algorithm according to the requirements in the distribution system. The PV-UAPF system provides dual benefit of distributed generation as well as improving power quality of the distribution system.

 

REFERENCES:

  • R. Tummuru,M. K. Mishra, and S. Srinivas, “Dynamic energy management of hybrid energy storage system with high-gain pv converter,” IEEE Transactions on Energy Conversion, vol. 30, no. 1, pp. 150–160, March 2015.
  • Singh, A. Chandra, K. A. Haddad, Power Quality: Problems and Mitigation Techniques. London: Wiley, 2015.
  • Devassy and B. Singh, “Control of solar photovoltaic integrated upqc operating in polluted utility conditions,” IET Power Electronics, vol. 10, no. 12, pp. 1413–1421, Oct 2017.
  • Devassy and B. Singh, “Performance analysis of proportional resonant and adaline-based solar photovoltaic-integrated unified active power filter,” IET Renewable Power Generation, vol. 11, no. 11, pp. 1382–1391, 2017.
  • Ramya and J. Pratheebha, “A novel control technique of solar farm inverter as pv-upfc for the enhancement of transient stability in power grid,” in 2016 International Conference on Emerging Trends in Engineering, Technology and Science (ICETETS), Feb 2016, pp. 1–7.

Power quality improvement in distribution network using DSTATCOM with battery energy storage system

ABSTRACT

The distribution static compensator (DSTATCOM) provides fast control of active and reactive powers to enable load compensation, harmonics current elimination, voltage flicker mitigation, voltage and frequency regulation. This paper presents power quality improvement technique in the presence of grid disturbances and wind energy penetration using DSTATCOM with battery energy storage system. DSTATCOM control is provided based on synchronous reference frame theory. A modified IEEE 13 bus test feeder with DSTATCOM and wind generator is used for the study. Power quality events during grid disturbances such as feeder tripping and re-closing, voltage sag, swell and load switching have been studied in association with DSTATCOM. The power quality disturbances due to wind generator outage, synchronization and wind speed variations have also been investigated. The study has been carried out using MATLAB/SIMULINK and the simulation results are compared with real time results obtained by the use of real time digital simulator (RTDS) for validating the effectiveness of proposed methodology. The proposed method has been proved to be effective in improvement of power quality with all disturbances stated above.

 

KEYWORDS

  1. Battery energy storage system
  2. Radial distribution feeder
  3. DSTATCOM
  4. Synchronous reference frame theory

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig.1. Proposed DSTATCOM with BESS.

 

SIMULATION RESULTS

Fig.2. Feeder tripping and re-closing without DSTATCOM in the network (a) RMS voltage at bus 632, (b) active power flow and (c) reactive power flow

Fig.3. Feeder tripping and re-closing with DSTATCOM in the network (a) RMS voltage at bus 632, (b) active power flow and (c) reactive power flow

Fig.4. Load switching without DSTATCOM in the network (a) RMS voltage at bus 632, (b) active power flow and (c) reactive power flow

Fig.5. Load switching with DSTATCOM in the network (a) RMS voltage at bus 632, (b) active power flow and (c) reactive power flow.

Fig.6. Voltage sag and swell (a) without DSTATCOM, (b) with DSTATCOM and (c) reactive power flow during voltage sag and swell.

Fig. 7 Wind synchronization (a) voltage without DSTATCOM, (b) voltage with DSTATCOM, (c) active power flow with DSTATCOM and (d) reactive power flow with DSTATCOM.

Fig. 8. Wind outage (a) voltage without DSTATCOM, (b) voltage with DSTATCOM, (c) active power flow with DSTATCOM and (d) reactive power flow with DSTATCOM

Fig. 9. Wind speed variation.

 

CONCLUSION

The proposed research work investigates into PQ events associated with distribution network due to grid disturbances such as voltage sag, swell, load switching, feeder tripping and re-closing. The DSTATCOM has been proposed to improve the power quality in the above events. The proposed DSTATCOM with SRF based control has been proved to be effective in improving the power quality in these events at grid level. The power quality events associated with wind operations such as wind generator outage, grid synchronization of wind generator and wind speed variations have been improved by the use of proposed DSTATCOM in the distribution network. From, these studies it has been established that the DSTATCOM can effectively be used to improve the power quality in the distribution network with wind generation and during grid disturbances. The results have been validated in real time utilizing RTDS. The real time results are very close to the simulation results which shows the effectiveness of proposed DSTATCOM with BESS for improvement of PQ in the distribution system.

 

REFERENCES

  • Ibrahim W, Morcos M. A power quality perspective to system operational diagnosis using fuzzy logic and adaptive techniques. IEEE Trans Power Deliv 2003;18(3):903–9. http://dx.doi.org/10.1109/TPWRD.2003.813885.
  • Ray P, Mohanty S, Kishor N. Classification of power quality disturbances due to environmental characteristics in distributed generation system. IEEE TransSust Energy 2013;4(2):302–13. http://dx.doi.org/10.1109/TSTE.2012.2224678.
  • Tascikaraoglu A, Uzunoglu M, Vural B, Erdinc O. Power quality assessment of wind turbines and comparison with conventional legal regulations: a case study in turkey. Appl Energy 2011;88(5):1864–72. http://dx.doi.org/10.1016/j. apenergy.2010.12.001.
  • Dash P, Padhee M, Barik S. Estimation of power quality indices in distributed generation systems during power islanding conditions. Int J Electr Power Energy Syst 2012;36(1):18–30. http://dx.doi.org/10.1016/j.ijepes.2011.10.019.
  • Mahela OP, Shaik AG, Gupta N. A critical review of detection and classification of power quality events. Renew Sust Energy Rev 2015;41(0):495–505. http:// dx.doi.org/10.1016/j.rser.2014.08.070.

A FACTS Device Distributed Power Flow Controller (DPFC)

ABSTRACT:

This paper presents a new component within the flexible ac-transmission system (FACTS) family, called distributed power-flow controller (DPFC). The DPF Controller is derived from the unified power-flow controller (UPFC). The DPFC can be considered as a UPFC with an eliminated common dc link. The active power exchange between the shunt and series converters, which is through the common dc link in the UPFC, is now through the transmission lines at the third- harmonic frequency. The DPFC employs the distributed FACTS (D-FACTS) concept, which is to use multiple small-size single-phase converters instead of the one large-size three-phase series converter in the UPFC. The large number of series converters provides redundancy, thereby increasing the system reliability. As the D-FACTS converters are single-phase and floating with respect to the ground, there is no high-voltage isolation required between the phases. Accordingly, the cost of the DPFC system is lower than the UPFC. The DPFC has the same control capability as the UPFC, which comprises the adjustment of the line impedance, the transmission angle, and the bus voltage. The principle and analysis of the DPFC are presented in this paper and the corresponding experimental results that are carried out on a scaled prototype are also shown.

 

KEYWORDS:

  1. AC–DC power conversion
  2. Load flow control
  3. Power electronics
  4. Power semiconductor devices
  5. Power-transmission

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

facts device

Fig. 1. DPFC control block diagram.

 

EXPECTED SIMULATION RESULTS:

 Fig. 2. DPFC operation in steady state: line current.       

               

Fig. 3. DPFC operation in steady sta te:series converter voltage.

Fig. 4. DPFC operation in steady state: bus

Fig. 5. Reference voltage for the series converters. voltage and current at the Δ side of the transformer


Fig. 6. Step response of the DPFC: series converter

Fig. 7. Step response of the DPFC: linecurrent. voltage.

Fig. 8. Step response : active and reactive power injected by the series converter at the fundamental frequency.

Fig.9. Step response: bus voltage and current at the Δ of the transformer

 

CONCLUSION:

 This paper has presented a new concept called Distributed power flow controller. It emerges from the UPFC and inherits the control capability of the UPFC, which is the simultaneous adjustment of the line impedance, the transmission angle, and the bus-voltage magnitude. The common dc link between the shunt and series converters, which is used for exchanging active power in the UPFC, is eliminated. This power is now transmitted through the transmission line at the third-harmonic frequency. The series converter of the DPFC employs the D-FACTS concept, which uses multiple small single-phase converters instead of one large-size converter. The reliability of the DPFC is greatly increased because of the redundancy of the series converters. The total cost of this controller is also much lower than the UPFC, because no high-voltage isolation is required at the series-converter part and the rating of the components of is low. The DPFC concept has been verified by an experimental setup. It is proved that the shunt and series converters in the DPFC can exchange active power at the third-harmonic frequency, and the series converters are able to inject controllable active and reactive power at the fundamental frequency.

 

REFERENCES:

 -H. Song and A. Johns, Flexible ac Transmission Systems (FACTS) (IEE Power and Energy Series), vol. 30. London, U.K.: Institution of Electrical Engineers, 1999.

  • G. Hingorani and L. Gyugyi, Understanding FACTS : Concepts and Technology of Flexible AC Transmission Systems. New York: IEEE Press, 2000.
  • Gyugyi, C.D. Schauder, S. L.Williams, T. R. Rietman,D. R. Torgerson, andA. Edris, “The unified power flowcontroller:Anewapproach to power transmission control,” IEEE Trans. Power Del., vol. 10, no. 2, pp. 1085–1097, Apr. 1995.
  • -A. Edris, “Proposed terms and definitions for flexible ac transmission system (facts),” IEEE Trans. Power Del., vol. 12, no. 4, pp. 1848–1853, Oct. 1997.
  • K. Sen, “Sssc-static synchronous series compensator: Theory, modeling, and application,” IEEE Trans. Power Del., vol. 13, no. 1, pp. 241–246, Jan. 1998.

An Enhanced Voltage Sag Compensation Scheme for Dynamic Voltage Restorer

IEEE Transactions on Industrial Electronics, 2013

ABSTRACT

This paper deals with improving the voltage quality of sensitive loads from voltage sags using dynamic voltage restorer (DVR). The higher active power requirement associated with voltage phase jump compensation has caused a substantial rise in size and cost of dc link energy storage system of DVR. The existing control strategies either mitigate the phase jump or improve the utilization of dc link energy by (i) reducing the amplitude of injected voltage, or (ii) optimizing the dc bus energy support. In this paper, an enhanced sag compensation strategy is proposed that mitigates the phase jump in the load voltage while improving the overall sag compensation time. An analytical study shows that the proposed method significantly increases the DVR sag support time (more than 50%) compared with the existing phase jump compensation methods. This enhancement can also be seen as a considerable reduction in dc link capacitor size for new installation. The performance of proposed method is evaluated using simulation study.

 

KEYWORDS:

  1. Dynamic voltage restorer (DVR)
  2. Voltage source inverter (VSI)
  3. Voltage sag compensation
  4. Voltage phase jump compensation.

 

SOFTWARE: MATLAB/SIMULINK

  

BLOCK DIAGRAM:

Fig. 1. Basic DVR based system configuration

 

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation results for the proposed sag compensation method for 50% sag depth. (a) PCC voltage, (b) load voltage, (c) DVR voltage, (d) DVR active and reactive power, and (e) dc link voltage.

Fig. 3. Simulation results for the proposed sag compensation method for 23% sag depth. (a) PCC voltage, (b) load voltage, (c) DVR voltage, (d) DVR active and reactive power, and (e) dc link voltage.

 

CONCLUSION

In this paper an enhanced sag compensation scheme is proposed for capacitor supported DVR. The proposed strategy improves the voltage quality of sensitive loads by protecting them against the grid voltage sags involving the phase jump. It also increases compensation time by operating in minimum active power mode through a controlled transition once the phase jump is compensated. To illustrate the effectiveness of the proposed method an analytical comparison is carried out with the existing phase jump compensation schemes. It is shown that compensation time can be extended from 10 to 25 cycles (considering pre sag injection as the reference method) for the designed limit of 50% sag depth with 450 phase jump. Further extension in compensation time can be achieved for intermediate sag depths. This extended compensation time can be seen as considerable reduction in dc link capacitor size (for the studied case more than 50%) for the new installation. The effectiveness of the proposed method is evaluated through extensive simulations in MATLAB/Simulink and validated on a scaled lab prototype experimentally. The experimental results demonstrate the feasibility of the proposed phase jump compensation method for practical applications.

 

REFERENCES

  • A. Martinez and J.M. Arnedo, “Voltage sag studies in distribution networks- part I: System modeling,” IEEE Trans. Power Del., vol. 21,no. 3, pp. 338–345, Jul. 2006.
  • G. Nielsen, F. Blaabjerg and N. Mohan, “Control strategies for dynamic voltage restorer, compensating voltage sags with phase jump,” in Proc. IEEE APEC, 2001, pp. 1267–1273.
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Power Quality Improvement Using UPQC Integrated with Distributed Generation Network

International Journal of Electrical and Computer Engineering Vol:8, No:7, 2014

 ABSTRACT  The increasing demand of electric power is giving an emphasis on the need for the maximum utilization of renewable energy sources. On the other hand maintaining power quality to satisfaction of utility is an essential requirement. In this paper the design aspects of a Unified Power Quality Conditioner integrated with photovoltaic system in a distributed generation is presented. The proposed system consist of series inverter, shunt inverter are connected back to back on the dc side and share a common dc-link capacitor with Distributed Generation through a boost converter. The primary task of UPQC is to minimize grid voltage and load current disturbances along with reactive and harmonic power compensation. In addition to primary tasks of UPQC, other functionalities such as compensation of voltage interruption and active power transfer to the load and grid in both islanding and interconnected mode have been addressed. The simulation model is design in MATLAB/ Simulation environment and the results are in good agreement with the published work.

 

KEYWORDS:

  1. Distributed Generation(DG)
  2. Interconnected mode
  3. Islanding mode
  4. Maximum power point tracking (MPPT)
  5. Power Quality (PQ)
  6. Unified power quality conditioner (UPQC)
  7. Photovoltaic array (PV).

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

 UPQC with DG connected to the DC link

Fig. 1. UPQC with DG connected to the DC link

 

EXPECTED SIMULATION RESULTS:

Fig. 2  Bus voltage, series compensating voltage, and load voltage

 

Fig. 3 Simulation result for upstream fault on feeder: Bus voltage, compensating voltage, load voltage

 

Fig. 4 Simulation results for load change: nonlinear load current,Feeder current, load voltage, and dc-link capacitor voltage

 

CONCLUSION

The new configuration is named unified power-quality conditioner with Photo Voltaic System (UPQC-PV). Compared to a conventional UPQC, the proposed topology is capable of fully protecting critical and sensitive loads against distortions, sags/swell, and interruption in both islanding and interconnected modes. The performance of the UPQC-PV is evaluated under various disturbance conditions and it offers the following advantages:

1) To regulate the load voltage against sag/swell and disturbances in the system to protect the nonlinear/sensitive load.

2) To compensate for the reactive and harmonic components of nonlinear load current.

3) To compensate voltage interruption and active power transfer to the load and grid in islanding mode to protect sensitive critical load.

4) Depending upon the ratings, the combined system can reduce the cost up to one fifth of the separate system. Capacity enhancement has been achieved using multi-level or multi-module and central control mode, however, the flexibility of UPQC to increase its capacity in future and to cope up with the increase load demand in medium voltage distribution system.

 

REFERENCES

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