Inverter topologies for DSTATCOM applications—a simulation study

ABSTRACT

This paper describes a few different topologies of inverters used for realizing a distribution static compensator (DSTATCOM). A brief introduction of the need for shunt compensation as well as the requirements of the shunt compensator has also been given. An algorithm for generating references has been described. Three major topologies of inverters – three-leg inverter with single dc capacitor, three-leg inverter with neutral clamped dc capacitors, four-leg inverter and three single-phase inverters with common dc capacitor – have been described and simulated. DSTATCOM topologies for high voltage distribution systems have also been described. The Voltage Source Converter (VSC) topologies have been compared on the basis of the performance of the inverter for certain chosen system conditions and the number of switch devices and dc capacitors used. All simulations have been performed using PSCAD/EMTDC.

KEYWORDS:

1.      DSTATCOM

2.      VSC

3.      Hysteresis current control

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Single-phase circuit showing the DSTATCOM.

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation of three-leg VSC with balanced load: (a) source voltages; (b) source currents; (c) load currents; (d) source voltage and current.

Fig. 3. Simulation of three-leg VSC for unbalanced load: (a) phase a injected currents; (b) phase b injected currents; (c) phase c injected currents; (d)source currents; (e) load currents; (f) source voltage and current.

Fig. 4. Simulation of three-leg VSC for unbalanced load with modified reference currents: (a) phase a injected currents; (b) phase b injected currents; (c) phase c injected currents; (d) source currents; (e) load currents; (f) source voltage and current.

Fig. 5. Simulation of three-leg VSC with neutral clamped dc capacitors without dc in the load current: (a) source voltages; (b) source currents; (c) load currents; (d) source voltage and current; (e) dc link voltage; (f) dc capacitor voltages.

Fig. 6. Simulation of three-leg VSC with neutral clamped dc capacitors with dc in the load current: (a) source voltages; (b) source currents; (c) load currents; (d) source voltage and current; (e) dc link voltage; (f) dc capacitor voltages.

Fig. 7. Simulation of three-leg VSC with neutral clamped dc capacitors with dc in the load current using modified reference currents: (a) compensator current; (b) source current; (c) load current; (d) source voltage and current; (e) dc link voltage; (f) dc capacitor voltages.

Fig. 8. Simulation of four-leg VSC: (a) source voltages; (b) source currents; (c) load currents; (d) source voltage and current; (e) dc link voltage.

Fig. 9. Simulation of four-leg VSC for load currents with a dc component: (a) source voltages; (b) load currents; (c) source currents; (d) source voltage and current; (e) dc capacitor voltage; (f) phase c injected current (HV side); (g) phase c injected current (LV side); (h) transformer flux.

CONCLUSION

Based on the simulation results shown in the previous sections, a comparative study of the features of the DSTATCOM for low voltage distribution systems is given in Table 4. A comparison of DSTATCOM topologies for high voltage distribution systems can be made along similar lines with similar conclusions. The paper describes an algorithm [1] used to generate references for the currents to be injected by the DSTATCOM. It has been proved that the references would result in source currents that are balanced sinusoids. Limitations of the DSTATCOM topologies that are widely in use are highlighted and improvements have been suggested when a topology fails. From the comparison in Table 4 and the simulation results of Section 3.3, the four-leg VSC is the most suitable topology to realize a DSTATCOM. For high voltage distribution systems, it has been shown through simulation results that the DSTATCOM using the four-leg VSC is capable of compensating dc currents despite the VSC being connected to the distribution system through step-down transformers. It has been shown that the ampereturns on both windings of the transformer due to the currents injected by the DSTATCOM cancel each other and the transformer does not saturate.

REFERENCES

[1]   Ghosh, A. Joshi, A new approach to load balancing and power factor correction in power distribution system, IEEE Trans. Power Deliv. 15 (July (3)) (2000) 417–422.

[2]    S.-J. Huang, J.-C. Wu, A control algorithm for three-phase three wired active power filters under non-ideal mains voltages, IEEE Trans. Power Electron. 14 (July (4)) (1999) 753–760.

[3]    B. Singh, K. Al-Haddad, A. Chandra, A review of active power filters for power quality improvement, IEEE Trans. Ind. Electron. 46 (October (5)) (1999) 960–971.

[4]    M. Aredes, J. Hafner, K. Heumann, Three-phase four-wire shunt active filter control strategies, IEEE Trans. Power Electron. 12 (March (2)) (1997) 311–318.

[5]   M.K. Mishra, A. Ghosh, A. Joshi, A new STATCOM topology to compensate loads containing ac and dc components, in: IEEE Power Engineering Society Winter Meeting, Singapore, January 2000.

Modeling and Simulation of a Distribution STATCOM using Sirnulink’s Power System Blockset

 ABSTRACT

This paper presents a study on the modeling of a STAT-COM (Static Synchronous Compensator) used for reactive power compensation on a distribution network. The power circuits of the D-STATCOM and the distribution network are modeled by specific blocks from the Power System Blockset while the control system is modeled by Simulink blocks. Static and dynamic performance of a E3 Mvar D-STATCOM on a 25-kV network is evaluated. An “average modeling” approach is proposed to simplify the PWM inverter operation and to accelerate the simulation for control parameters adjusting purpose. Simulation performance obtained with both modeling approaches are presented and compared.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. The cascade H-bridge converter based DSTATCOM.

EXPECTED SIMULATION RESULTS

Fig. 2 Waveforms illustrating the D-STATCOM dynamic performance.

Fig. 3 Voltage and current waveforms during the change from inductive to capacitive operation at t = 0.2 s.

Fig. 4 Comparison between responses of detailed and average models for a step change in the network internal voltage.

CONCLUSION

A detailed model of a D-STATCOM has been developed for use in Simulink environment with the Power System Blockset. Models of both power circuit and control system have been implemented in the same Simulink diagram allowing smooth simulation. Two modeling approaches (device and average modeling) have been presented and applied to the case of a +3Mvar D-STATCOM connected to a 25-kV distribution network. The obtained simulation results have demonstrated the validity of the developed models. Average modeling allows a faster simulation which is well suited to controller tuning purposes.

REFERENCES

[1] K.K. Sen, “STATCOM: Theory, Modeling, Applications,” in IEEE PES 1999 Winter Meeting Proceedings, pp. 11 77- 1183.

[2] Flexible AC Transmission Systems (FACTS), edited by Y.H. Song and A.T. Johns, The Institution of Electrical Engineers, London, UK, 1999.

[3] K.V. Patil, et al., “Application of STATCOM for Damping Torsional Oscillations in Series Compensated AC Systems,” IEEE Trans. on Energy Conversion, Vol. 13, No. 3,Sept. 1998, pp.237-243.

[4] C.D. Schauder, H. Mehta, “Vector Analysis and Control of Advanced Static VAR Compensators,” IEE Proceedings- [SI Power System Blockset For Use with Sirnulink, User’s Guide, The MathWorks Inc., 2000. C, Vol. 140, NO. 4, July 1993, pp. 299-306.

Control of Cascaded H-Bridge Converter based DSTATCOM for High Power Applications

ABSTRACT

This paper presents the simulation studies on a Cascaded H-Bridge converter based Distribution Static Synchronous Compensator (DSTATCOM) for improving the power quality of a distribution system. Voltage source converter based DSTATCOM has been established as the most preferred solution for management of reactive power in distribution utilities and for improving voltage regulation, power factor and power quality in industries. For high power applications, cascaded H-Bridge converter is the most ideal choice compared to two-level inverter with series connected power devices. In the present work DSTATCOM controller is designed using DQO modelling for reactive power management and thereby improving the power factor in distribution systems. The dc link voltage and the three phase load currents are used as feedback signals for the controller and it is designed in such a way that DSTATCOM is able to supply the reactive current demanded by the load both during steady state and transient conditions using sinusoidal pulse width modulation control.

KEYWORDS

1.      Cascaded H-Bridge Converter

2.      DSTATCOM

3.      Reactive power compensation

4.       Sinusoidal PWM

SOFTWARE: MATLAB/SIMULINK

SIMULINK BLOCK DIAGRAM:

Fig. 1. The cascade H-bridge converter based DSTATCOM.

EXPECTED SIMULATION RESULTS

Fig. 2. The phase voltage (top trace ) and line-to-line voltages of H-bridge

cascaded inverter.

Fig. 3. Source phase voltage (top trace) and source phase Current (bottom

trace) with DSTATCOM in closed loop power factor control mode.

Fig. 4. DC link voltage (Vd,) (Top or First Trace), direct and quadrature axis

source currents (Second Trace) ,inverter currents Id and Iq (Third Trace) and

load reactive current (Bottom Trace).

Fig 5. Individual Capacitor voltages of three level Cascaded H-Bridge

Inverter.

CONCLUSION

The paper presents the principle of operation of cascaded H-bridge converter and simulation studies on cascaded converter based DSTATCOM using Sinusoidal PWM control. It is observed that the DSTATCOM is capable of supplying the reactive power demanded by the load both during steady state and transient operating conditions. The harmonics in cascaded H-bridge three-level inverter current are less compared to two-level inverter operating at same switching frequency.

REFERENCES

[1] Jih-Sheng Lal, Fang Zheng Peng," Multilevel Converters - A New Breed of Power Converters", IEEE Transactions on Industry Applications, Vol.32, no.3, pp.509,1996.

[2] Muni B.P., Rao S.E., Vithal J.V.R., Saxena S.N., Lakshminarayana S., Das R.L., Lal G., Arunachalam M., "DSTATCOM for Distribution Utility and Industrial Applications", Conference Proceedings, IEEE, Region Tenth Annual Conference, TENCON-03. Page(s): 278- 282 Vol. 1

[3] Bishnu P. Muni, S.Eswar Rao, JVR Vithal and SN Saxena, "Development of Distribution STATCOM for power Distribution Network" Conference Records, International conference on "Present and Future Trends in Transmission and Convergence", New Delhi, Dec.2002,pp. VII_26-33.

[4] F.Z. Peng, J. S. Lai, J.W. Mckeever, J. Van Coevering, "A Multilevel Voltage - Source inverter with Separate dc sources for Static Var Generation" IEEE Transactions on Industry Applications, Vol. 32, No. 5, Sep 1996, ppl 130-1138.

[5] K.Anuradha, B.P.Muni, A.D.Rajkumar," Simulation of Cascaded HBridge Converter Based DSTATCOM" First IEEE Conference on Industrial Electronics and Applications, May 2006, pp 501-505.

Tuning of a PI-MR Controller Based on Differential Evolution Meta heuristic Applied to the Current Control Loop of a Shunt-APF

ABSTRACT

This paper aims to present an alternative methodology to improve the tuning of proportional integral multi-resonant (PI-MR) controller applied to the current control loop of a shunt active power filter (SAPF) by using differential evolution (DE) metaheuristic method. For computing the PI-MR controller gains, the methodology based on Naslin polynomial (NP) can be employed, although its performance is limited. On the other hand, tuning procedures accomplished by trial-and error methods have been largely used. In order to fill the lack of methodological procedures to determine the PI-MR controller gains, the use of DE metaheuristic optimization algorithm is proposed to perform an optimal adjustment. The DE algorithm operates minimizing an appropriate cost function, taking into account the total harmonic distortion of the source current, the error of the compensation\ current control loop, and the saturation limit of the control action. The effectiveness of the proposed methodology is compared to the NP-based method, applied to a single phase SAPF. The proposed methodology is validated by means of both simulation and experimental results. The evaluation of the static and dynamic performances is obtained from experimental tests performed based on digital signal processor.

KEYWORDS:

1.      Differential evolution

2.      Multi-resonant controller

3.      Optimization

4.      Shunt active power filter.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Single-phase SAPF scheme.

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation results of SAPF operating with Load 1 (utility voltage v_s(200V/div), utility current is and compensation current i_c(20A/div), load current i_L(30A/div)): (a) PI controller; (b) PI-MR_NP controller; (c) PI-MR_DE controller.

Fig. 3.Simulation results of SAPF operating with Load 2 (utility voltage v_s(200V/div), utility current i_s and compensation current i_c(20A/div), load current i_L(30A/div)): (a) PI controller; (b) PI-MR_NP controller; (c) PI-MR_DE controller.

Fig. 4. Harmonic spectra and THD of the source current obtained from simulation results with PI, PI-MRNP and PI-MRDE controllers: (a) Load 1; (b) Load 2.

CONCLUSION

This paper proposes an alternative methodology using DE metaheuristic optimization algorithm for obtaining systematic procedures to achieve the PI-MR controller gains employed in the current control loop of a SAPF. A comparative analysis involving the classical PI controller and two other PI-MR controllers was performed. The classical PI controller was tuned using the well-known frequency response method, while the MR controllers were tuned considering the NP-based approach, as well as DE metaheuristic optimization algorithm.Extensive simulation and experimental results proved that superior performance is achieved when the SAPF operates with the DE-based PI-MR controller. Therefore, it can be concluded that the DE metaheuristic method represents a promising approach for tuning PI-MR controller for active power filtering applications.

REFERENCES

[1]   R. C. Dugan, M. F. McGranaghan, S. Santoso, H. W. Beaty, Electrical Power Systems Quality, 3rd. ed., McGraw-Hill Education, USA, 2012.

[2]    R. A. Modesto, S. A. O. Silva, and A. A. Oliveira Jr., “Versatile unified power quality conditioner applied to three-phase four-wire distribution systems using a dual control strategy,” IEEE Trans. Power Electron., vol. 31, no. 8, pp. 5503–5514, Aug. 2016.

[3]    B. A. Angélico, L. B. G. Campanhol, and S. A. O. Silva, “Proportional integral/ proportional-integral-derivative tuning procedure of a single phase shunt active power filter using bode diagram,” IET Power Electron., vol. 7, no. 10, pp. 2647–2659, Aug. 2014.

[4]    B. Singh, K. Al-Haddad, and A. Chandra, “A review of active filters for power quality improvement,”IEEE Trans.Ind. Electron., vol.46, no.5, pp.960–971, Oct. 1999.

[5]   O. Vodyakho, T. Kim, S. Kwak, and C. Edrington, “Comparison of the space vector current controls for shunt active power filters,” IET Power Electron., vol. 2, no. 6, pp. 653–664, Nov. 2009.

Simultaneous Microgrid Voltage and Current Harmonics Compensation Using Coordinated Control of Dual-Interfacing-Converters

ABSTRACT

 The growing installation of distributed generation (DG) units in low voltage distribution systems has popularized the concept of nonlinear load harmonic current compensation using multi functional DG interfacing converters. It is analyzed in this paper that the compensation of local load harmonic current using a single DG interfacing converter may cause the amplification of supply voltage harmonics to sensitive loads, particularly when the main grid voltage is highly distorted. To address this limitation, unlike the operation of conventional unified power quality conditioners (UPQC) with series converter, a new simultaneous supply voltage and grid current harmonic compensation strategy is proposed using coordinated control of two shunt interfacing converters. Specifically, the first converter is responsible for local load supply voltage harmonic suppression. The second converter is used to mitigate the harmonic current produced by the interaction between the first interfacing converter and the local nonlinear load. To realize a simple control of parallel converters, a modified hybrid voltage and current controller is also developed in the paper. By using this proposed controller, the grid voltage phase-locked loop and the detection of the load current and the supply voltage harmonics are unnecessary for both interfacing converters. Thus, the computational load of interfacing converters can be significantly reduced. Simulated and experimental results are captured to validate the performance of the proposed topology and the control strategy.

 KEYWORDS:

1.      Parallel converters

2.      Active power filter

3.      Dynamic voltage restorer

4.      LCL filter

5.      Resonance; power quality

6.      Harmonic detection

7.      Phase-locked loop.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Diagram of the proposed topology.

EXPECTED SIMULATION RESULTS:

Fig. 2. Only the local load harmonic current is compensated. (From upper to lower: 𝑉_{𝑠𝑢𝑝𝑝𝑙𝑦}, 𝐼_𝑔, 𝐼₂, 𝐼_{𝐿𝑜𝑎𝑑})

Fig. 3. The harmonic spectrum of grid current 𝐼_𝑔 in Fig. 11.

Fig. 4. The harmonic spectrum of supply voltage 𝑉_{𝑠𝑢𝑝𝑝𝑙𝑦} in Fig. 11.

Fig. 5. Only the supply voltage harmonic component is compensated. (From upper to lower: 𝑉_{𝑠𝑢𝑝𝑝𝑙𝑦}, 𝐼_𝑔, 𝐼₂, 𝐼_{𝐿𝑜𝑎𝑑})

Fig. 6. The harmonic spectrum of grid current 𝐼_𝑔 in Fig. 14.

Fig. 7. The harmonic spectrum of supply voltage 𝑉_{𝑠𝑢𝑝𝑝𝑙𝑦} in Fig. 14.

 CONCLUSION

When a single multi-functional interfacing converter is adopted to compensate the harmonic current from local nonlinear loads, the quality of supply voltage to local load can hardly be improved at the same time, particular when the main grid voltage is distorted. This paper discusses a novel coordinated voltage and current controller for dual-converter system in which the local load is directly connected to the shunt capacitor of the first converter. With the configuration, the quality of supply voltage can be enhanced via a direct closed-loop harmonic voltage control of filter capacitor voltage. At the same time, the harmonic current caused by the nonlinear load and the first converter is compensated by the second converter. Thus, the quality of the grid current and the supply voltage are both significantly improved. To reduce the computational load of DG interfacing converter, the coordinated voltage and current control without using load current/supply voltage harmonic extractions or phase-lock loops is developed to realize to coordinated control of parallel converters.

REFERENCES

.

[1]   B. Singh, K. AI-Haddad, A. Chandra, “A review of active filters for power quality improvement,” IEEE Trans. Ind. Electron., vol. 46, no. 5, pp. 960 - 971, May. 1999.

[2]    P. Acuna, L. Moran, M. Rivera, J. Dixon, and J. Rodriguez, “Improved active power filter performance for renewable power generation systems,” IEEE Trans. Power Electron., vol. 29, no.2, pp. 687-694, Feb. 2013.

[3]   Y. W. Li, F. Blaabjerg, D. M. Vilathgamuwa, and P. C. Loh, “Design and Comparison of High Performance Stationary-Frame Controllers for DVR Implementation,” IEEE Trans. Power Electron., vol. 22, pp. 602-612, Mar. 2007.

[4]   C. Meyer, R. W. DeDoncker, Y. W. Li, and F. Blaabjerg, “Optimized Control Strategy for a Medium-Voltage DVR – Theoretical Investigations and Experimental Results,” IEEE Trans. Power Electron., vol. 23, pp. 2746-2754, Nov. 2008.

[5]    F. Blaabjerg, Z. Chen, and S. B. Kjaer, “Power electronics as efficient interface in dispersed power generation systems,” IEEE Trans. Power Electron., vol. 19, pp. 1184-1194, Sep. 2004.