Application of Unified Power Flow Controller in Interconnected Power Systems—Modeling, Interface, Control Strategy, and Case Study

ABSTRACT:

In this paper, a new power frequency model for unified power flow controller (UPFC) is suggested with its dc link capacitor dynamics included. Four principal control strategies for UPFC series element main control and their impacts on system stability are discussed. The main control of UPFC series element can be realized as a combination of the four control functions. The supplementary control of UPFC is added for damping power oscillation. The integrated UPFC model has then been incorporated into the conventional transient and small signal stability programs with a novel UPFC-network interface. Computer tests on a 4-generator interconnected power system show that the suggested UPFC power frequency model and the UPFC- network interface method work very well. The results also show that the suggested UPFC control strategy can realize power flow control fairly well and improve system dynamic performance significantly.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

 

Fig. 1. Transmission line with UPFC installed.

CONTROL SYSTEM:

Fig. 2. The main control and phasor diagram.

EXPECTED SIMULATION RESULTS:

Fig. 3. Plots of case 1a.

Fig. 4. Plots of case 1b.

Fig. 5. Plots of case 1c.

Fig. 6. Effects of supplementary control.

Fig. 7. Results of the suggested control scheme.

CONCLUSION:

The suggested UPFC power frequency model and the developed UPFC-network interface method work very well in the study of power system dynamics with satisfied convergence and accuracy. Four principal main control strategies are discussed and the computer tests results support the discussion conclusion very well. The constant power flow control is good for steady state control and the constant series compensation control is useful for first swing stability. The supplementary control is very efficient in damping intcrarea power oscillation. The suggested UPFC control can realize the desired control strategy flexibly and improve system dynamic performance significantly.

REFERENCES:

[1] L. Gyugyi, “Unified Power-Flow Control Concept for Flexible AC Transmission Systems,” IEE Proceedings-C, vol. 139, no. 4, pp. 323–331, July 1992.

[2] I. Papic, P. Zunko, and D. Povh, “Basic Control of Unified Power Flow Controller,” IEEE Trans. on Power Systems, vol. 12, no. 4, pp. 1734–1739, Nov. 1997.

[3] R. Mihalic, P. Zunko, and D. Povh, “Improvement of Transient Stability Using Unified Power Flow Controller,” IEEE Trans. on Power Delivery, vol. 11, no. 1, pp. 485–491, Jan. 1996.

[4] K. S. Smith, L. Ran, and J. Penman, “Dynamic Modeling of a Unifed Power Flow Controller,” IEE Proc.-Gener. Transm. Distrib., vol. 144, no. 1, pp. 7–12, Jan. 1997.

[5] M. Noroozian, L. Angquist, and M. Ghandhari, et al., “Improving Power System Dynamics by Series-connected FACTS devices,” IEEE Trans. on Power Delivery, vol. 12, no. 4, pp. 1635–1641, Oct. 1997.

High-Gain Single-Stage Boosting Inverter for Photovoltaic Applications

High-Gain Single-Stage Boosting Inverter

for Photovoltaic Applications

ABSTRACT

This paper introduces a high-gain single-stage boosting inverter (SSBI) for alternative energy generation. As compared to the traditional two-stage approach, the SSBI has a simpler topology and a lower component count. One cycle control was employed to generate ac voltage output. This paper presents theoretical analysis, simulation and experimental results obtained from a 200 W prototype. The experimental results reveal that the proposed SSBI can achieve high dc input voltage boosting, good dc–ac power decoupling, good quality of ac output waveform, and good conversion efficiency.

KEYWORDS

1.      Microinverter

2.      one cycle control (OCC)

3.      tapped inductor (TI)

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig.1. Topology of the proposed SSBI.

EXPECTED SIMULATION RESULTS

                       

Fig. 2. Simulated waveforms of the proposed SSBI on the line frequency

scale.

          

Fig. 3. Simulated waveforms of the SSBI’s output voltage Vac , dc-link voltage

Vdc , and dc input source current Ig with the TI operating at the CCM–DCM

boundary (Po = Pob ).

                

Fig. 4. Simulated waveforms of the SSBI’s output voltage Vac , dc-link voltage

Vdc , and dc input source current Ig : (a) illustrating the undistorted output

voltage Vac , when SSBI is operated in deep DCM just above the minimum

power level Po > Pomin and (b) illustrating the peak-shaving distortion of the

output voltage Vac for Po < Pomin .

CONCLUSION

A high-gain SSBI for alternative energy generation applications is presented in this paper. The proposed topology employs a TI to attain high-input voltage stepup and, consequently, allows   operation from low dc input voltage. This paper presented principles of operation, theoretical analysis of continuous and discontinuous modes including gain and voltage and current stresses. To facilitate this report, two stand-alone prototypes one for 48 V input and another for 35 V input were built and experimentally tested. Theoretical findings stand in good agreement with simulation and experimental results. Acceptable efficiency was attained with low-voltage input source. The proposed SSBI topology has the advantage of high voltage stepup which can be further increased adjusting the TI turns ratio. The SSBI allows decoupled control functions. By adjusting the boost duty cycle Dbst, the SSBI can control the dc-link voltage, whereas the output waveform can be shaped by varying the buck duty cycleDbk. The ac–dc power decoupling is attained on the high-voltage dc link and therefore requires a relatively low capacitance value. The OCC control method was applied to shape the output voltage. OCC’s fast response and low sensitivity to dc-bus voltage ripple allowed applying yet smaller decoupling capacitor value, and has demonstrated low THD output for different types of highly nonlinear loads.

REFERENCES

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

[2] D. C. Martins and R. Demonti, “Interconnection of a photovoltaic panels array to a single-phase utility line from a static conversion system,” in Proc. IEEE Power Electron. Spec. Conf., 2000, pp. 1207–1211.

[3] Q. Li and P.Wolfs, “A current fed two-inductor boost converter with an integrated magnetic structure and passive lossless snubbers for photovoltaic module integrated converter applications,” IEEE Trans. Power Electron., vol. 22, no. 1, pp. 309–321, Jan. 2007.

[4] S. B. Kjaer, J. K. Pedersen, and F. Blaabjerg, “Power inverter topologies for photovoltaic modules—A review,” in Proc. Ind. Appl. Conf., 2002, vol. 2, pp. 782–788.

[5] C. Vartak, A. Abramovitz, and K. M. Smedley, “Analysis and design of energy regenerative snubber for transformer isolated converters,” IEEE Trans. Power Electron., vol. 29, no. 11, pp. 6030–6040, Nov. 2014.

An Envelope Type (E-Type) Module Asymmetric Multilevel Inverters With Reduced Components

ABSTRACT:

This paper presents a new E-Type module for asymmetrical multilevel inverters with reduced components. Each module produces 13 levels with four unequal DC sources and 10 switches. The design of the proposed module makes some preferable features with a better quality than similar modules such as the low number of semiconductors and DC sources and low switching frequency. Also, this module is able to create a negative level without any additional circuit such as an H-bridge which causes reduction of voltage stress on switches. Cascade connection of the proposed structure leads to a modular topology with more levels and higher voltages. Selective harmonics elimination pulse width modulation (SHE-PWM) scheme is used to achieve high quality output voltage with lower harmonics. MATLAB simulations and practical results are presented to validate the proposed module good performance. Module output voltage satisfies harmonics standard (IEEE519) without any filter in output.

KEYWORDS:

1.      Asymmetric

2.      Components

3.      E-Type

4.      Multilevel inverter

5.      Power electronics

6.      Selective harmonics elimination

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Proposed E-Type module of multilevel inverter (a) Circuit topology

 EXPECTED SIMULATION RESULTS:

Fig.2 Output voltage and FFT analysis of proposed multilevel

CONCLUSION:

This paper presented a new multilevel inverter topology named as Envelope Type (E-Type) module which can generate 13 levels with reduced components. It can be used in high voltage high power applications with unequal DC sources. As E-Type module can be easily modularized, it can be used in cascade arrangements to form high voltage outputs with low stress on semiconductors and lowering the number of devices. Modular connection of these modules leads to achieve more voltage levels with different possible paths. It causes an improvement in the reliability of the modular inverter which enables it to use different paths in case of malfunction for a switch or a driver. The main advantage of proposed module is its ability to generate both positive and negative output voltage without any H-bridge circuit at the output of the inverter. THDv% is obtained 3.46% and 4.54% in simulation and experimental results, respectively that satisfy harmonics standard (IEEE519). Also module is tested in three frequency and under different resistive – inductive loads which results shows good performance.

REFERENCES:

[1] R. Feldman, M. Tomasini, E. Amankwah, J.C. Clare, P.W. Wheeler, D.R. Trainer, R.S. Whitehouse, "A Hybrid Modular Multilevel Voltage Source Converter for HVDC Power Transmission," IEEE Trans. Ind. Appl., vol.49, no.4, pp.1577–1588, July-Aug. 2013.

[2] M. Odavic, V. Biagini, M. Sumner, P. Zanchetta, M. Degano, "Low Carrier–Fundamental Frequency Ratio PWM for Multilevel Active Shunt Power Filters for Aerospace Applications," IEEE Trans. Ind. Appl., vol.49, no.1, pp.159–167, Jan.-Feb. 2013.

[3] Liming Liu, Hui Li, Seon-Hwan Hwang, Jang-Mok Kim, "An Energy-Efficient Motor Drive With Autonomous Power Regenerative Control System Based on Cascaded Multilevel Inverters and Segmented Energy Storage," IEEE Trans. Ind. Appl., vol.49, no.1, pp.178–188, Jan.-Feb. 2013.

[4] Yushan Liu, Baoming Ge, H. Abu-Rub, F.Z. Peng, "An Effective Control Method for Quasi-Z-Source Cascade Multilevel Inverter-Based Grid-Tie Single-Phase Photovoltaic Power System," IEEE Trans. Ind. Inform., vol.10, no.1, pp.399–407, Feb. 2014.

[5] Jun Mei, Bailu Xiao, Ke Shen, L.M. Tolbert, Jian Yong Zheng, "Modular Multilevel Inverter with New Modulation Method and Its Application to Photovoltaic Grid-Connected Generator," IEEE Trans. on Power Electron., vol.28, no.11, pp.5063–5073, Nov. 2013.