Integrated Photovoltaic and Dynamic Voltage Restorer System Configuration

ABSTRACT:  

This paper presents a new system structure for integrating a grid-connected photovoltaic (PV) system together with a self-supported dynamic voltage restorer (DVR).

DVR

The proposed system termed as a “six-port converter,” consists of nine semiconductor switches in total. The proposed configuration retains all the essential features of normal PV and DVR systems while reducing the overall switch count from twelve to nine.

In addition, the dual functionality feature significantly enhances the system robustness against severe symmetrical/asymmetrical grid faults and voltage dips.

A detailed study on all the possible operational modes of six-port converter is presented. An appropriate control algorithm is developed and the validity of the proposed configuration is verified through extensive simulation as well as experimental studies under different operating conditions.

KEYWORDS:

  1. Bidirectional power flow
  2. Distributed power generation
  3. Photovoltaic (PV) systems
  4. Power quality
  5. Voltage control

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

 

 Fig. 1. Proposed integrated PV and DVR system configuration.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation results: operation of proposed system during health grid mode (PV-VSI: active and DVR-VSI: inactive). (a) Vpcc; (b) PQload; (c) PQgrid; (d) PQpv-VSI; and (e) PQdvr-VSI.

Fig. 3. Simulation results: operation of proposed system during fault mode (PV-VSI: inactive and DVR-VSI: active). (a) Vpcc; (b) Vdvr; (c) Vload; (d) PQload; (e) PQgrid; (f) PQpv-VSI; and (g) PQdvr-VSI.

Fig. 4. Simulation results: operation of proposed system during balance three phase sag mode (PV-VSI: active and DVR-VSI: active). (a) Vpcc; (b) Vdvr-VSI; (c) Vload; (d) PQgrid; (e) PQpv-VSI; and (f) PQdvr-VSI.

Fig. 5. Simulation results: operation of proposed system during unbalanced sag mode (PV-VSI: active and DVR-VSI: active). (a) Vpcc; (b) Vdvr-vsi; (c) Vload; (d) PQgrid; (e) PQpv-VSI; and (f) PQdvr-VSI.

Fig. 6. Simulation results: operation of proposed system during inactive PV plantmode (PV-VSI: active and DVR-VSI: active). (a) Vpcc; (b) Vload; (c) Vdc; (d) PQload; (e) PQdvr-VSI; and (f) PQpv-VSI.

 CONCLUSION:

 In this paper, a new system configuration for integrating a conventional grid-connected PV system and self supported DVR is proposed.

The proposed configuration not only exhibits all the functionalities of existing PV and DVR system, but also enhances the DVR operating range.

PV

It allows DVR to utilize active power of PV plant and thus improves the system robustness against sever grid faults.

The proposed configuration can operate in different modes based on the grid condition and PV power generation.

The discussed modes are healthy grid mode, fault mode, sag mode, and PV inactive mode.

The comprehensive simulation study and experimental validation demonstrate the effectiveness of the proposed configuration and its practical feasibility to perform under different operating conditions.

The proposed configuration could be very useful for modern load centers where on-site PV generation and strict voltage regulation are required.

REFERENCES:

[1] R. A. Walling, R. Saint, R. C. Dugan, J. Burke, and L. A. Kojovic, “Summary of distributed resources impact on power delivery systems,” IEEE Trans. Power Del., vol. 23, no. 3, pp. 1636–1644, Jul. 2008.

[2] C. Meza, J. J. Negroni, D. Biel, and F. Guinjoan, “Energy-balance modeling and discrete control for single-phase grid-connected PV central inverters,” IEEE Trans. Ind. Electron., vol. 55, no. 7, pp. 2734–2743, Jul.2008.

[3] T. Shimizu, O. Hashimoto, and G. Kimura, “A novel high-performance utility-interactive photovoltaic inverter system,” IEEE Trans. Power Electron., vol. 18, no. 2, pp. 704–711, Mar. 2003.

[4] S. B. Kjaer, J. K. Pedersen, and F. Blaabjerg, “A review of single-phase grid-connected inverters for photovoltaic modules,” IEEE Trans. Ind.Appl., vol. 41, no. 5, pp. 1292–1306, Sep./Oct. 2005.

[5] T. Esram, J. W. Kimball, P. T. Krein, P. L. Chapman, and P. Midya, m“Dynamic maximum power point tracking of photovoltaic arrays using ripple correlation control,” IEEE Trans. Power Electron., vol. 21, no. 5, pp. 1282–1291, Sep. 2006.

Electric Spring for Voltage and Power Stability and Power Factor Correction

ABSTRACT:  

Electric Spring (ES), a new smart grid technology,
has earlier been used for providing voltage and power stability in
a weakly regulated/stand-alone renewable energy source powered
grid. It has been proposed as a demand side management
technique to provide voltage and power regulation. In this paper,
a new control scheme is presented for the implementation of the
electric spring, in conjunction with non-critical building loads like
electric heaters, refrigerators and central air conditioning system.
This control scheme would be able to provide power factor
correction of the system, voltage support, and power balance
for the critical loads, such as the building’s security system, in
addition to the existing characteristics of electric spring of voltage
and power stability. The proposed control scheme is compared
with original ES’s control scheme where only reactive-power
is injected. The improvised control scheme opens new avenues
for the utilization of the electric spring to a greater extent by
providing voltage and power stability and enhancing the power
quality in the renewable energy powered microgrids

 BLOCK DIAGRAM:

Fig. 1. Electric Spring in a circuit

EXPECTED SIMULATION RESULTS:

Fig. 2. Over-voltage, Conventional ES: Power Factor of system (ES turned on at t = 0.5 sec)

Fig. 3. Over-voltage, Conventional ES: Active and Reactive power across critical load, non-critical load, and electric spring (ES turned on at t=0.5 sec)

Fig. 4 Under-voltage, Conventional ES: RMS Line voltage, ES Voltage, and Non-Critical load voltage (ES turned on at t=0.5 sec)

Fig. 5. Under-voltage, Conventional ES: Power Factor of system (ES turned on at t = 0.5 sec)

Fig. 6. Under-voltage, Conventional ES: Active and Reactive power across critical load, non-critical load, and electric spring (ES turned on at t=0.5 sec)

Fig. 7. Over-voltage, Improvised ES: RMS Line voltage, ES Voltage, and Non-Critical load voltage (ES turned on at t=0.5 sec)

Fig. 8. Over-voltage, Improvised ES: Power Factor of system (ES turned on at t = 0.5 sec)

CONCLUSION

In this paper as well as earlier literature s, the Electric Spring
was demonstrated as an ingenious solution to the problem of
voltage and power instability associated with renewable energy
powered grids. Further in this paper, by the implementation of
the proposed improvised control scheme it was demonstrated
that the improvised Electric Spring (a) maintained line voltage
to reference voltage of 230 Volt, (b) maintained constant
power to the critical load, and (c) improved overall power
factor of the system compared to the conventional ES. Also,
the proposed ‘input-voltage-input-current’ control scheme is
compared to the conventional ‘input-voltage’ control. It was
shown, through simulation and hardware-in-loop emulation,
that using a single device voltage and power regulation and
power quality improvement can be achieved.

Control Scheme

It was also shown that the improvised control scheme has merit over the
conventional ES with only reactive power injection.
Also, it is proposed that electric spring could be embedded
in future home appliances. If many non-critical loads in the
buildings are equipped with ES, they could provide a reliable
and effective solution to voltage and power stability and in sit u
power factor correction in a renewable energy powered
micro-grids. It would be a unique demand side management
(D S M) solution which could be implemented without any
reliance on information and communication technologies.

REFERENCES

[1] S. Y. Hui, C. K. Lee, and F. F. Wu, “Electric springs – a new smart
grid technology,” IEEE Transactions on Smart Grid, vol. 3, no. 3, pp.
1552–1561, Sept 2012.
[2] S. Hui, C. Lee, and F. WU, “Power control circuit and
method for stabilizing a power supply,” 2012. [Online]. Available:
http://www.google.com/patents/US20120080420
[3] C. K. Lee, N. R. Ch a u d h u r i, B. Ch a u d h u r i, and S. Y. R. Hui, “Droop
control of distributed electric springs for stabilizing future power grid,”
IEEE Transactions on Smart Grid, vol. 4, no. 3, pp. 1558–1566, Sept
2013.
[4] C. K. Lee, B. Ch a u d h u r i, and S. Y. Hui, “Hardware and control
implementation of electric springs for stabilizing future smart grid with
intermittent renewable energy sources,” IEEE Journal of Emerging and
Selected Topics in Power Electronics, vol. 1, no. 1, pp. 18–27, March
2013.
[5] C. K. Lee, K. L. Che n g, and W. M. N g, “Load characterization of electric
spring,” in 2013 IEEE Energy Conversion Congress and Exposition, Sept
2013, pp. 4665–4670.

Power Quality Enhancement in Residential Smart Grids through Power Factor Correction Stages

Power Quality Enhancement titles

ABSTRACT:

The proliferation of non-linear loads and the increasing penetration of Distributed Energy Resources (D ER) in Medium-Voltage (M V) and Low-Voltage (L V) distribution grids, make it more difficult to maintain the power quality levels in residential electrical grids, especially in the case of weak grids. Most household appliances contain a conventional Power Factor Corrector (PFC) rectifier, which maximizes the load Power Factor (PF) but does not contribute to the regulation of the voltage Total Harmonic Distortion (TH D V ) in residential electrical grids.

This

manuscript proposes a modification for PFC controllers by adapting the operation mode depending on the measured TH D V . As a result, the PF Cs operate either in a low current Total Harmonic Distortion (TH DI ) mode or in the conventional resistor emulator mode and contribute to the regulation of the TH D V and the PF at the distribution feeders. To prove the concept, the modification is applied to a current sensor less Non-Linear Controller (N LC) applied to a single-phase Boost rectifier. Experimental results show its performance in a PFC front-end stage operating in Continuous Conduction Mode (CC M) connected to the grid with different TH D V.

BLOCK DIAGRAM:

 

 Fig. 1. Residential L V grid with household appliances feed through conventional AC/DC stages (without the proposed operation mode selector) and the proposed P Q E controller.

 EXPECTED SIMULATION RESULTS:

 

Fig. 2. Experimental results of P Q E PFC at 50 Hz. Voltage and current wave forms in a) resistor emulator mode (k = 0), b) sinusoidal current mode (k = 1) and c) measured spectra in both operation modes.

Fig. 3. Experimental results of  P Q E PFC at 60 Hz. Voltage and current wave forms in a) resistor emulator mode (k = 0), b) sinusoidal current mode (k = 1) and c) measured spectra in both operation modes.

Fig. 4. Experimental results of P Q E PFC at 400 Hz. Voltage and current wave forms in a) resistor emulator mode (k = 0), b) sinusoidal current mode (k = 1) and c) measured spectra in both operation modes.

CONCLUSION:

The consequence on the electrical power quality of connecting household appliances to the grid through PFC stages has been assessed considering different TH D V scenarios. As has been shown in (17) and (23), there are conditions under which sinusoidal current consumption results in better PF at the PC C than with resistor emulator behavior, commonly assumed to be ideal for PFC stages. A modification of the carrier signal of N LC controllers applied to PFC stages is designed to impress sinusoidal input current despite the input voltage distortion. The line current estimation with no interaction with the power stage implements the N LC with high noise immunity. The digital implementation of the non-linear controller is appropriate to define the carrier and to include additional reduction of the current distortion depending on the application.

P Q E controller

The P Q E controller can be applied to mitigate the effect of nonlinear loads within household appliances on residential electrical grids. The operation mode of the digital controller can be autonomously adjusted through the locally measured TH D V , without extra circuitry. The user or a TH D V threshold detection selects the convenient behavior (either resistor emulator or pure sinusoidal current). Experimental results obtained with high TH D V (above 5 %) confirm the feasibility of the P Q E controller in both sinusoidal current and resist i v e emulator modes.

REFERENCES:

[1] IEEE Std. 519-2014 (Revision of IEEE Std. 519-1992), IEEE Recommended Practice and Requirements for Harmonic Control in Electric Power Systems, D OI 10.1109/IEEE STD.2014.6826459, pp. 1–29, Jun. 2014.

[2] Y. J. Wang, R. M. O’Connell, and G. Brownfield, “Modeling and prediction of distribution system voltage distortion caused by nonlinear residential loads,” IEEE Trans. Power Del., vol. 16, D OI 10.1109/61.956765, no. 4, pp. 744–751, Oct. 2001.

[3] H. Ora e e, “A quantitative approach to estimate the life expectancy of motor insulation systems,” IEEE Trans. Die l e ct r. Elect r. In s u l., vol. 7, D OI 10.1109/94.891990, no. 6, pp. 790–796, Dec. 2000.

[4] D. Fab i an i and G. C. Mont an a r i, “The effect of voltage distortion on ageing acceleration of insulation systems under partial discharge activity,” IEEE Elect r. Ins u l. Mag., vol. 17, D OI 10.1109/57.925300, no. 3, pp. 24–33, May. 2001.

[5] T. J. Dion i s e and V. Lo r ch, “Harmonic filter analysis and redesign for a modern steel facility with two melt furnaces using dedicated capacitor banks,” in IEEE I AS Annual Meeting, vol. 1, D OI 10.1109/I AS.2006.256496, pp. 137–143, Oct. 2006.

Performance Improvement of DVR by Control of Reduced-Rating with A Battery Energy Storage

ABSTRACT:

Performance improvement of Voltage infusion strategies for DVRs (Dynamic Voltage Restorers) and working modes are settled in this paper. Utilizing fuzzy logic control DVR with dc link& with Battery Energy Storage System frameworks are worked. Power quality issues for the most part consonant contortion, voltage swell and droop are diminished with DVR utilizing Synchronous Reference Theory (SRF hypothesis) with the assistance of fuzzificaton waveforms are watched.

 

 BLOCK DIAGRAM:

 Fig.1.Block Diagram of DVR

 EXPECTED SIMULATION RESULTS:

Fig.2 Voltage waveforms at common coupling point (PCC) and load during harmonic distortion

Fig.3. the dc voltage injection from Battery energy Storage System connected DVR system at voltage swelling period

 Fig.4. DVR waveforms during voltage sag at time of voltage in phase injection

 Fig.5 Amplitude of load voltages and PCC voltages w.r.t time

 Fig 6.DVR waveforms during harmonic distortion at the time of voltage in phase injection

CONCLUSION:

By applying distinctive voltage infusion conspires the job of DVR has been appeared with a most recent control strategy. The introduction of DVR has been offset with different plans with a decreased rating VSC. For gaining the power of DVR, the reference stack voltages have been resolved with the assistance of unit vectors, for which the blunder of voltage addition is diminished. By utilizing SRF hypothesis the reference DVR voltages have been resolved. At last, the outcome inferred are that the in stage voltage addition with PCC voltage diminishes the DVR rating and yet at its DC transport the vitality source is squandered. battery energy storage system. Performance Improvement of DVR by Control of Reduced-Rating with A Battery Energy Storage.

 

Performance Analysis of DVR, DSTATCOM and UPQC For Improving The Power Quality With Various Control Strategies

ABSTRACT:

Here, we have examined the voltage quality enhancement techniques by utilizing Dynamic Voltage Restorer (DVR), Distribution Static Synchronous Compensator (D-STATCOM) and Unified Power Quality Conditioner (UPQC) utilizing two distinctive controller Strategies. The controllers utilized are Proportional Integral Controller (PIC) and Fuzzy Logic Controller (FLC). A PI Controller computes a mistake an incentive as the distinction between a deliberate variable and wanted set point. The fluffy rationale controller has continuous sources of info estimated at each example time, named mistake and blunder rate and one yield named activating sign for each stage. The information signals are fuzzified and spoken to in fluffy set documentations as capacities. The characterized ‘If … At that point .. .’ rules deliver yield impelling signs and these signs are defuzzified to simple control signals for contrasting with a transporter motion with control PWM inverter.

 

 BLOCK DIAGRAM:

Fig 1. The equivalent circuit diagram of DVR

 

Fig 2. The equivalent circuit diagram of DST A TCOM

Fig 3.The circuit diagram of UPQC

 EXPECTED SIMULATION RESULTS:

 

Fig 4. Input voltage and input current waveform without compensation

 

Fig 5. Load voltage and load current waveform without compensation

Fig 6. load voltage and load current waveform after compensation(DVR)

Fig 7. Output load voltage without compensation

Fig 8. Output load voltage with compensation using FLC

Fig 9.load voltage and load current waveform after compensation (D-STATCOM)

Fig 10. Load voltage and load current waveform after compensation (D-STATCOM)

Fig 11. Load voltage and load current waveform for UPQC with PI Controller.

Fig 12 Load voltage and load current waveform with compensation

CONCLUSION:

In this paper, we have considered the arrangement, shunt and arrangement shunt compensators. Execution examination has been finished by looking at the power quality utilizing each compensator. The execution of DVR has been dissected with PI controller the heap voltage amid blame is practically equivalent to the ideal load voltage. Load current greatness is practically equivalent yet at the same time there are a few awkward nature between the stages for a little span of time. DVR have been found to manage voltage under Fuzzy Logic controller. Unmistakably DVR diminishes sounds from load voltage successfully and makes it smooth. Henceforth, it is reasoned that DVR has a tremendous extension in enhancing power quality in appropriation frameworks. DSTATCOM is demonstrated to repay voltage levels under defective conditions. Utilizing PI controller, sounds have been diminished extensively. Be that as it may, current got lopsided for the whole span of time. By utilizing the Fuzzy Logic Controller rather than the PI Controller gives better transient reaction. The DC Link voltage is all of a sudden expanded over the reference esteem. Also, it is taken back to its reference esteem. A decent voltage control is likewise accomplished by actualizing Fuzzy rationale control. Additionally the enduring state is achieved quicker. The control techniques of UPQC were portrayed and contrasted with deference with its execution through reenactment. The power quality issues are nearly decreased. The shut circle control plans of current control, for the proposed UPQC have been examined. Absolute consonant mutilation was broke down and it depicts that the UPQC with fluffy controller gives more effectiveness than alternate procedures.

Permanent Magnet Synchronous Generator Based Wind Energy and DG Hybrid System

ABSTRACT:

This paper examines the utilization of changeless magnet synchronous generators (PMSGs) for a breeze vitality transformation framework (WECS) and a diesel motor driven generator (DG hybrid system) set of an independent cross breed framework with a battery vitality stockpiling framework (BESS). For voltage control at the purpose of normal coupling (PCC) and adjusted supply at terminals of DG hybrid system set, a solitary stage D-Q hypothesis based control calculation is connected for the exchanging of voltage source converter (VSC) of BESS and the greatest power point following (MPPT) is accomplished for WECS with a gradual conductance procedure for the exchanging of a dc-dc help converter. Recreation aftereffects of created model of proposed independent mixture framework, which is produced in MATLAB show execution of both the controllers and power quality enhancement of the half breed framework.

 

 SCHEMATIC DIAGRAM:

 

Fig. 1 Schematic diagram of Wind-Diesel hybrid configuration

 EXPECTED SIMULATION RESULTS:

Fig. 2 (a) Characteristics of the system with constant wind speed under varying loads.

Fig. 3 (b) Estimation of supply currents and voltages using control algorithm

Fig.4 (c) dynamic Performance of controller of hybrid system under varying linear loads at 10 m/s wind speed

Fig. 5(a) Characteristics of the system with constant wind speed under varying loads.

Fig. 6(b) Estimation of supply currents and voltages using control algorithm

Fig.7(c) dynamic Performance of controller of hybrid system under varying nonlinear loads at 10 m/s wind speed.

Fig. 8 waveforms and harmonic spectra (a) Phase ‘a’ supply voltage of at PCC (b) Phase ‘a’ supply current under nonlinear unbalanced loads.

Fig. 9 Controllers’ performance under wind speed reduction (11 m/s-8 m/s)

Fig. 10  Controllers’ performance under rise in wind speed (8 m/s-11 m/s)

 CONCLUSION:

A 3-φ independent breeze diesel half breed framework utilizing PMSG alongside BESS has been recreated in MATLAB utilizing Simpower framework tool compartments. Different parts have been intended for the cross breed framework and controller’s acceptable execution has been delineated utilizing 1-φ-D-Q hypothesis with SOGI channels for different loads under unique conditions while keeping up consistent voltage at PCC and adjusted source flows of diesel generator and furthermore for music concealment according to rules of IEEE-519-1992 standard. A mechanical sensor less methodology has been utilized for accomplishing MPPT through gradual conductance procedure.

 

Single Phase Series Active Power Filter Based on 15-Level Cascaded Inverter Topology

ABSTRACT:

A topology of series active power filter (SAP F) based on a single phase half-bridge cascaded multilevel invert er is proposed in order to compensate voltage harmonics of the load connected to the point of common coupling (P CC). This paper presents the main parts of the invert er and The proposed invert er with the simple control easily obtains any voltage reference. Therefore, the invert er acts as a harmonic source when the reference is a non-sinusoidal signal.

prototype

A prototype of 15-level invert er based SAP F is manufactured without using a parallel passive filter (PP F) because it is intended to represent the compensation capability of the SAP F by itself. The load connected to P CC whose voltage is non-sinusoidal is filtered both in simulation and experimental studies. The validity of the proposed invert er based SAP F is verified by simulation as well as experimental study. Both simulation and experimental results show that the proposed multilevel invert er is suitable for SAP F applications.

 

CIRCUIT DIAGRAM:

Figure 1. The basic configuration of the proposed system.

EXPECTED SIMULATION RESULTS:

Figure 2. Simulation results – Set I a) V p cc and V h P CC before compensation (50 V I div), b) invert er and load voltage after compensation (50 V I div).

Figure 3. Simulation results – Set 2 a) V p cc and V”p cc before compensation (50 V l div), b) invert er and load voltage after compensation (50 V I div).

CONCLUSION:

This paper proposes a single phase half-bridge cascaded multi level invert er based SAP F. The multi level invert er topology and operation principle is introduced and With the proposed topology, the number of output levels can easily be increased. Switching angles of the semiconductor devices used in the invert er are also obtained by a simple method, moreover A SAP F with the proposed invert er topology is simulated under different harmonic distortion levels of P CC.

aim

The aim of the simulation is to compensate the load voltage harmonics connected to P Cc. In addition to the simulations, the proposed SAP F prototype is designed and Using this prototype, experimental study is also performed. Microchip d s PIC 30 F 6010 is preferred as a controller in this prototype, because it is commercially available and inexpensive micro controller. The presentable results of the proposed system are summarized as follows;

results

  • The TH D values obtained from simulation study is similar to experimental results and the results of simulation and experimental studies demonstrate the accuracy of the simulation study.
  • The TH D values after compensation is reduced to 2.88% and 3.07% by using the proposed invert er based SAP F and After compensation, the waveform of load voltage is almost sinusoidal.
  • A highly distorted sinusoidal waveform with a TH D value of 24.12% is compensated with the proposed invert er based SAP F and the TH D value is reduced to 3.07%, with This it is shown that the proposed invert er is suitable for SAP F applications.

Both simulation and experimental studies show the validity of the proposed invert er as a SAP F.

REFERENCES:

[1] M. 1. M. Mon t e r o, E. R. Ca d a val, F. B. Gonzalez, “Comparison of control strategies for shunt active power filters in three-phase four wire systems”, IEEE Trans. Power Electron., , 22, (I), pp. 229- 236, 2007.

[2] F. Z. P e n g, H. A k a g i, and A. Na b a e, ” A new approach to harmonic compensation in power systems-A combined system of shunt passive and series active filters,” IEEE Trans. Ind. A pp l. , Vol. 26, No. 6, pp. 983- 990, N o v.l Dec. 1990.

[3] Z. Wang, Q. Wang, W. Y a o, and 1. Li u, “A series active power filter adopting hybrid control approach,” IEEE Trans. Power Electron. , Vol. 16, No. 3, pp. 301- 310, May 2001.

[4] H. Aka g i, ‘Trends in active power line conditioners,” IEEE Trans. Power Electron. , Vol. 9, No. 3, pp. 263- 268, May 1994.

[5] M. E I-H ab r o u k, M. K. D a r wish, and P. Me h ta, “Active power filters : A review,” l E E Elect r. Power App l., Vol. 147, No. 5, pp. 403-413, Sep.2000.

A Novel 7-Level Cascaded Inverter for Series Active Power Filter

ABSTRACT:

Harmonic voltage compensation of the load connected to the point of common coupling (PCC) by using a series of active power filter (SAPF) based on a single phase cascaded multilevel inverter is proposed. The proposed multilevel inverter are presented in detail. The inverter has the ability of acting as a harmonic source when the reference is a non-sinusoidal signal. To achieve this, a simple control technique is performed with the proposed inverter. A prototype of 7-level inverter based SAPF is manufactured without using a parallel passive filter (PPF) because it is designed to show SAPF own compensation capacity alone. Filtering ability of the SAPF is shown both in simulation and experimental studies. The validity of the proposed inverter based SAPF is verified by simulation as well as experimental study. The results show that the proposed multi-level inverter is suitable for SAPF applications.

KEYWORDS:

  1. Active power filter
  2. Multilevel inverter
  3. Harmonic compensation
  4. Half-bridge cascaded
  5. Power quality

 SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. The scheme of the proposed system.

EXPECTED SIMULATION RESULTS:

 

 (a) Simulation result (50 V/div), (5 ms/div)

Fig. 2. The waveform of VPCC before compensation

(a) Simulation result (50 V/div), (5 ms/div)

Fig. 3. The waveforms of the load voltage and the proposed inverter voltage after compensation.

 CONCLUSION:

This paper proposes a single phase cascaded inverter based SAPF. The 7-level inverter topology and operation principle is introduced. With the proposed topology, the number of output levels can easily be increased. Switching signals of the semiconductor devices used in the inverter are also obtained by a simple method. A SAPF with the proposed inverter topology is simulated.The aim of the simulation is to compensate the load voltage harmonics connected to PCC. In addition to the simulation, the proposed SAPF prototype is designed. Using this prototype, experimental study is performed. Simulation and experimental results similar each other proves the accuracy of the analysis. The load waveform that is highly distorted with a THD value of 24.12% is compensated with the proposed inverter based SAPF and the THD value is reduced to 3.80% in experimental study. This shows that the proposed inverter is suitable for SAPF applications.

REFERENCES:

[1] M. I. M. Montero, E. R. Cadaval, F. B. Gonzalez, “Comparison of control strategies for shunt active power filters in three-phase four-wire systems”, IEEE Trans. Power Electron., vol. 22, no. 1, pp. 229–236, 2007.

[2] F. Z. Peng, H. Akagi, and A. Nabae, “A new approach to harmonic compensation in power systems—A combined system of shunt passive and series active filters,” IEEE Trans. Ind. Appl., vol. 26, no. 6, pp. 983– 990, Nov./Dec. 1990.

[3] Z. Wang, Q. Wang, W. Yao, and J. Liu, “A series active power filter adopting hybrid control approach,” IEEE Trans. Power Electron., vol. 16, no. 3, pp. 301–310, May 2001.

[4] H. Akagi, “Trends in active power line conditioners,” IEEE Trans. Power Electron., vol. 9, no. 3, pp. 263–268, May 1994.

[5] M. El-Habrouk, M. K. Darwish, and P. Mehta, “Active power filters: A review,” IEE Electr. Power Appl., vol. 147, no. 5, pp. 403–413, Sep. 2000.

Improving the Performance of Cascaded H-bridge based Interline Dynamic Voltage Restorer

IEEE Transactions on Power Delivery, 2015

 ABSTRACT:

 An interline dynamic voltage restorer (IDVR) is a new device for sag mitigation which is made of several dynamic voltage restorers (DVRs) with a common DC link, where each DVR is connected in series with a distribution feeder. During sag period, active power can be transferred from a feeder to another one and voltage sags with long durations can be mitigated. IDVR compensation capacity, however, depends greatly on the load power factor and a higher load power factor causes lower performance of IDVR. To overcome this limitation, a new idea is presented in this paper which allows to reduce the load power factor under sag condition, and therefore, the compensation capacity is increased. The proposed IDVR employs two cascaded H-bridge multilevel converters to inject AC voltage with lower THD and eliminates necessity to low-frequency isolation transformers in one side. The validity of the proposed configuration is verified by simulations in the PSCAD/EMTDC environment. Then, experimental results on a scaled-down IDVR are presented to confirm the theoretical and simulation results.

 

KEYWORDS:

  1. Back-to-back converter
  2. Cascaded H-bridge
  3. Interline dynamic voltage restorer

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Power circuit schematic of the IDVR with active power exchanging capability.

 

EXPECTED SIMULATION RESULTS:

Fig. 2. Investigating the IDVR performance when the proposed method is applied for a sag with depth of 0.4p.u.

Fig.3. Investigating the IDVR performance when the proposed method is applied for a sag with depth of 0.6p.u.

 

CONCLUSION:

In this paper, a new configuration has been proposed which not only improves the compensation capacity of the IDVR at high power factors, but also increases the performance of the compensator to mitigate deep sags at fairly moderate power factors. These advantages were achieved by decreasing the load power factor during sag condition. In this technique, the source voltages are sensed continuously and when the voltage sag is detected, the shunt reactances are switched into the circuit and decrease the load power factors to improve IDVR performance. Finally, the simulation and practical results on the CHB based IDVR confirmed the effectiveness of the proposed configuration and control scheme.

 

REFERENCES:

  • F. Comesana, D.F. Freijedo, J.D. Gandoy, O. Lopez, A.G. Yepes, J. Malvar, “Mitigation of voltage sags, imbalances and harmonics in sensitive industrial loads by means of a series power line conditioner” Electric Power systems Research 84 (2012) 20–30
  • [2] A. Felce, S. A. C. A. Inelectra, G. Matas, and Y. Da Silva, “Voltage Sag Analysis and Solution for an Industrial Plant with Embedded Induction Motors,” In Industry Applications Conference, 2004. 39th IAS Annual Meeting. Conference Record of the 2004 IEEE, vol. 4, pp. 2573-2578. IEEE, 2004.
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A Two Degrees of Freedom Resonant Control Scheme for Voltage Sag Compensation in Dynamic Voltage Restorers

 

 IEEE Transactions on Power Electronics, 2017

ABSTRACT:

This paper presents a two degrees of freedom (2DOF) control scheme for voltage compensation in a dynamic voltage restorer (DVR). It commences with the model of the DVR power circuit, which is the starting point for the control design procedure. The control scheme is based on a 2DOF structure implemented in a stationary reference frame (α−β), with two nested controllers used to obtain a pass-band behavior of the closed-loop transfer function, and is capable of achieving both a balanced and an unbalanced voltage sag compensation. The 2DOF control has certain advantages with regard to traditional control methods, such as the possibility of ensuring that all the poles of the closed-loop transfer function are chosen without the need for observers and reducing the number of variables to be measured. The use of the well-known double control- loop schemes which employ feedback current controllers to reduce the resonance of the plant is, therefore, unnecessary. A simple control methodology permits the dynamic behavior of the system to be controlled and completely defines the location of the poles. Furthermore, extensive simulations and experimental results obtained using a 5 kW DVR laboratory prototype show the good performance of the proposed control strategy.

 

KEYWORDS:

  1. Power Quality
  2. Dynamic Voltage Restorer (DVR)
  3. Control Design
  4. Resonant Controller
  5. Stationary Frame Controller
  6. Voltage Sag.

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

Fig. 1. Power system with a DVR included.

 

EXPECTED SIMULATION RESULTS:

 

Figure 2. DVR simulation for a balanced voltage sag. (a) Line-to-neutral three-phase voltages at PCC, (b) line-to-neutral voltages generated by the DVR, (c) line-to-neutral load voltages, and (d) error signal in α − β (redblue).

Figure 3 DVR simulation for an unbalanced voltage sag. (a) Line-to-neutral three-phase voltages at PCC, (b) line-to-neutral voltages generated by the DVR, (c) line-to-neutral load voltages, and (d) error signal in α − β (redblue).

Figure 4. DVR simulation for a 30 % balanced voltage sag. (a) Line-to neutral three-phase voltages at PCC, (b) error signal in α − β (red-blue) for the 2DOF-Resonant scheme, (c) error signal in α − β (red-blue) for double loop scheme, and (d) error signal in α−β (red-blue) for the double-loop with Posicast scheme.

Figure 5. DVR simulation for a 30 % type-E unbalanced voltage sag. (a) Line-to-neutral three-phase voltages at PCC, (b) error signal in α − β (redblue) for the 2DOF-Resonant scheme, (c) error signal in α − β (red blue) for double-loop scheme, and (d) error signal in α − β (red-blue) for the double-loop with Posicast scheme.

 

 CONCLUSION:

This paper presents a control scheme based on two nested controllers for voltage sag compensation in a DVR. The nested regulators provide the control with two degrees of freedom, and the control scheme is implemented in the stationary reference frame. Furthermore, in order to accomplish the requirements for voltage sag compensation, it is necessary to track the component at the fundamental frequency. This is achieved using a resonant term in one of the controllers. The proposed control design methodology is able to define all the poles of the closed-loop system without observers and with a reduction in the number of variables that must be measured, thus making it possible to avoid the use of the traditional current loop employed in control schemes for the DVR. The structure with the nested regulators achieves perfect zero tracking error at the nominal frequency and blocks the DC offset, signifying that it has some advantages over other control methods, such as double-loop schemes with proportional-resonant regulators. Moreover, the design methodology is thoroughly explained when the delay in the calculations is taken into account.

In this case, the design procedure allows the dominant poles of the closed-loop system to be chosen. If the closed-loop poles are chosen carefully, this control structure can also be applied to other systems which require higher delays, e.g., power converter applications with a reduced switching frequency. The design methodology can additionally be extended to the discrete domain. Comprehensive simulated and experimental results corroborate the performance of the 2DOF-Resonant control scheme for balanced and unbalanced voltage sags. The proposed control scheme is able to compensate both types of voltage sags with a very fast transient response and an accurate tracking of the reference voltage, even when the different types of loads and frequency deviations of the grid voltages are considered. Extended comparisons with a PR controller using a double-loop scheme and a PR controller in a double loop with a Posicast regulator have been carried out, demonstrating that the performance of the 2DOF-Resonant controller is superior in all cases. Moreover, the study of the stability as regards parameter variations for the compared control schemes demonstrates the more robust behavior of the 2DOF-Resonant control scheme.

 

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