A STATCOM-Control Scheme for Grid Connected Wind Energy System for Power Quality Improvement

ABSTRACT:

Injection of the wind power into an electric grid affects the power quality. The performance of the wind turbine and thereby power quality are determined on the basis of measurements and the norms followed according to the guideline specified in International Electro-technical Commission standard, IEC-61400. The influence of the wind turbine in the grid system concerning the power quality measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operation and these are measured according to national/international guidelines. The paper study demonstrates the power quality problem due to installation of wind turbine with the grid. In this proposed scheme STATic COMpensator (STATCOM) is connected at a point of common coupling with a battery energy storage system (BESS) to mitigate the power quality issues.

The battery energy storage is integrated to sustain the real power source under fluctuating wind power. The STATCOM control scheme for the grid connected wind energy generation system for power quality improvement is simulated using MATLAB/SIMULINK in power system block set. The effectiveness of the proposed scheme relives the main supply source from the reactive power demand of the load and the induction generator. The development of the grid co-ordination rule and the scheme for improvement in power quality norms as per IEC-standard on the grid has been presented.

 

KEYWORDS:

  1. International electro-technical commission (IEC)
  2. power quality
  3. wind generating system (WGS)

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

  statcom

Fig.1.System operational scheme in grid system.

 

EXPECTED SIMULATION RESULTS:

  

Fig. 1. Three phase injected inverter Current.

Fig. 2. (a) Source Current. (b) Load Current. (c) Inverter Injected Current. (d) Wind generator (Induction generator) current.


Fig. 3. (a) DC link voltage. (b) Current through Capacitor, 
STATCOM output voltage.

Fig. 5. Supply Voltage and Current at PCC.


Fig.6.(a) Source Current. (b) FFT of source current.                

Fig.7.(a) Source Current. (b) FFT of source current

 

CONCLUSION:

The paper presents the STATCOM-based control scheme for power quality improvement in grid connected wind generating system and with non linear load. The power quality issues and its consequences on the consumer and electric utility are presented. The operation of the control system developed for the STATCOM-BESS in MATLAB/SIMULINK for maintaining the power quality is simulated. It has a capability to cancel out the harmonic parts of the load current. It maintains the source voltage and current in-phase and support the reactive power demand for the wind generator and load at PCC in the grid system, thus it gives an opportunity to enhance the utilization factor of transmission line. The integrated wind generation and STATCOM with BESS have shown the outstanding performance. Thus the proposed scheme in the grid connected system fulfills the power quality norms as per the IEC standard 61400-21.

 

REFERENCES:

 Sannino, “Global power systems for sustainable development,” in IEEE General Meeting, Denver, CO, Jun. 2004.

  • S. Hook, Y. Liu, and S. Atcitty, “Mitigation of the wind generation integration related power quality issues by energy storage,” EPQU J., vol. XII, no. 2, 2006.
  • Billinton and Y. Gao, “Energy conversion system models for adequacy assessment of generating systems incorporating wind energy,” IEEE Trans. on E. Conv., vol. 23, no. 1, pp. 163–169, 2008, Multistate.
  • Wind Turbine Generating System—Part 21, International standard-IEC 61400-21,
  • Manel, “Power electronic system for grid integration of renewable energy source: A survey,” IEEE Trans. Ind. Electron., vol. 53, no. 4, pp. 1002–1014, 2006, Carrasco.

Three-Level 48-Pulse STATCOM with Pulse Width Modulation

ABSTRACT:

 In this paper, a new control strategy of a three level 48-pulse static synchronous compensator (STATCOM) is proposed with a constant dc link voltage and pulse width modulation at fundamental frequency switching. The proposed STATCOM is realized using eight units of three-level voltage source converters (VSCs) to form a three-level 48-pulse STATCOM. The conduction angle of each three-level VSC is modulated to control the ac converter output voltage, which controls the reactive power of the STATCOM. A fuzzy logic controller is used to control the STATCOM. The dynamic performance of the STATCOM is studied for the control of the reference reactive power, the reference terminal voltage and under the switching of inductive and capacitive loads.

KEYWORDS:

  1. Fuzzy logic control (FLC)
  2. Static synchronous compensator (STATCOM)
  3. Voltage source converter (VSC)
  4. Flexible ac transmission system (FACTS)
  5. Power frequency switching (PFS)

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 System configuration for simulation

 EXPECTED SIMULATION RESULTS:

 

 Fig. 2 a Dynamic performance of STATCOM for varying the reference reactive power. b Zoomed-in waveforms of the STATCOM ac current as well the dc current during a floating, b capacitive and c inductive operations

 

Fig. 3 Dynamic performance of STATCOM for varying the reference terminal voltage

Fig. 4 Dynamic performance of STATCOM by switching on inductive and capacitive loads

Fig. 5 a ac terminal voltage without STATCOM on switching non-linear load. b Dynamic performance of STATCOM and ac terminal voltage by switching on switching non-linear load

Fig. 6 Dynamic performance of STATCOM by switching on large value of apparent power

Fig. 7 Dynamic performance of STATCOM under short circuit of the upper half of the dc bus capacitance

Fig. 8 Dynamic performance of STATCOM under short circuit of the complete dc bus capacitance

Fig. 9 a Variation of the dc voltage with sudden load change using a PI and an FLC. b Variation of the ac terminal voltage with sudden load change using a PI and an FLC

CONCLUSION:

A new control strategy of a three-level 48-pulse STATCOM has been proposed with a constant dc link voltage and pulse width modulation at fundamental frequency switching. Its performance has been validated using MATLAB/Simulink. Simulation results have validated the satisfactory dynamic and steady performances of the proposed STATCOM operation. The harmonic content of the STATCOM current is found well below 5 % as per IEEE 519 standard [27].

 REFERENCES:

  1. T. Johns, A. Ter-Gazarian, D.F. Warne, Flexible ac transmission systems (FACTS), IEE Power Energy Series, the Institute of Electrical Engineers, London, UK, 1999
  2. N.G. Hingorani, L. Gyugyi, Understanding FACTS: Concepts and Technology of Flexible ac Transmission Systems (IEEE Press, 2000)
  3. R.M. Mathur, R.K. Verma, Thyristor-Based FACTS Controllers for Electrical Transmission Systems (Wiley-IEEE Press, 2002)
  4. K.R. Padiyar, FACTS Controllers in Power Transmission and Distribution (New Age International (P) Limited Publishers, India, 2007)
  5. K.K. Sen, Introduction to FACTS Controllers: Theory, Modeling and Applications (Wiley-IEEE Press, 2009)

 

Performance Investigation of Isolated Wind–Diesel Hybrid Power Systems With WECS Having PMIG

 

ABSTRACT:

This paper presents the automatic reactive power control of isolated wind–diesel hybrid power systems having a permanent-magnet induction generator for a wind energy conversion system and a synchronous generator for a diesel generator set. To minimize the gap between reactive power generation and demand, a variable source of reactive power is used such as a static synchronous compensator. The mathematical model of the system used for simulation is based on small-signal analysis. Three examples of the wind–diesel hybrid power system are considered with different wind power generation capacities to study the effect of the wind power generation on the system performance. This paper also shows the dynamic performance of the hybrid system with and without change in input wind power plus 1% step increase in reactive power load.

KEYWORDS:

  1. Permanent-magnet induction generator (IG) (PMIG)
  2. Static synchronous compensator (STATCOM)
  3. Synchronous generator (SG)
  4. Wind–diesel hybrid system

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 Fig. 1. Single line diagram of an isolated wind–diesel hybrid power system.

EXPECTED SIMULATION RESULTS:

 Fig. 2. Transient responses of the system (W-D with IG) for 1% step increase in load, with no change in input wind power.

Fig. 3. Transient responses of the system (W-D with PMIG) for 1% step increase in load, with no change in input wind power.

Fig. 4. Transient responses of the W-D systems with IG for 1% step increase in load plus 1% step increase in input wind power.

Fig. 5. Transient responses of the W-D systems with PMIG for 1% step increase in load plus 1% step increase in input wind power.

Fig. 6. Transient responses of the W-D1 systems with PMIG/IG for 1% step increase in input wind power plus the following: (S1) WECS uses PMIG and 10% step increase in load, (S2) WECS uses PMIG and 5%step increase in load, and (S3) WECS uses IG and 5% step increase in load.

Fig. 7. Transient responses for voltage deviations of W-D1 system without STATCOM when WECS uses PMIG for step load disturbances of (C1) 10%, (C2) 5%, and (C3) 1%.

Fig. 8 Transient responses for voltage deviations ofW-D1,W-D2, andW-D3 with STATCOM when WECS uses PMIG for 50% step load disturbances.

CONCLUSION:

Reactive power control of isolated wind–diesel hybrid power systems has been investigated when WECS uses PMIG for power generation. The WECSs are interconnected to diesel generation-based grid for the enhancement of capacity and fuel saving. The system also comprises STATCOM for reactive power support during steady-state and transient conditions. A mathematical model of the system has been derived for investigating the dynamic performance of the system. For comparison of performance with the existing systems, WECS has also been considered with IG for power generation. Three examples of wind–diesel systems with different wind power generation capacities have been considered for study. It has been observed that the STATCOM effectively stabilizes the oscillations in less than 0.01 s, caused by disturbances in reactive power load and in input wind power.

As steady-state condition is reached, the STATCOM provides the additional reactive power required by the system. It has also been observed that, as the unit size of the wind-power generation decreases, the value of the optimum gain setting increases. The W-D systems with PMIG have the added advantage of reduction in the size of the STATCOM but have comparable transient performance when W-D system uses IG for power generation. The PMIG also has higher efficiency than the IG. Therefore, PMIGs are very good options for W-D systems than IG.

REFERENCES:

[1] J. K. Kaldellis, Stand-Alone and Hybrid Wind Energy Systems: Technology, Energy Storage and Applications. Cambridge, U.K.: Woodhead Publ. Ltd., 2011.

[2] R. Hunter and G. Elliot, Wind–Diesel Systems, A Guide to the Technology and Its Implementation. Cambridge, U.K.: Cambridge Univ. Press, 1994.

[3] H. Nacfaire, Wind–Diesel and Wind Autonomous Energy Systems. London, U.K.: Elsevier Appl. Sci., 1989.

[4] T. K. Saha and D. Kastha, “Design optimization and dynamic performance analysis of a standalone hybrid wind diesel electrical power generation system,” IEEE Trans. Energy Convers., vol. 25, no. 4, pp. 1209–1217, Dec. 2010.

[5] R. Pena, R. Cardenas, J. Proboste, J. Clare, and G. Asher, “Wind–diesel generation using doubly fed induction machines,” IEEE Trans. Energy Convers., vol. 23, no. 1, pp. 202–214, Mar. 2008.

A Hybrid-STATCOM with Wide Compensation Range and Low DC-Link Voltage

ABSTRACT:

This paper planned a hybrid static synchronous compensator (hybrid-STATCOM) in a three-phase power transmission system that has a wide benefit range and low DC-link voltage. Because of these prominent quality, the system costs can be greatly reduced. In this paper, the circuit arrangement n of hybrid-STATCOM is received first.

STATCOM

Its V-I quality is then analyzed, discussed, and compared with traditional STATCOM and capacitive-coupled STATCOM (C-STATCOM). The system parameter design is then planned on the basis of application of the reactive power compensation range and prevention of the potential resonance problem. After that, a control strategy for hybrid-STATCOM is planned to allow operation under different voltage and current conditions

DC LINK

such as unbalanced current, voltage dip, and voltage fault. Finally, simulation and experimental results are provided to verify the wide compensation range and low DC-link voltage quality and the good dynamic work of the planned hybrid-STATCOM.

KEYWORDS:

 

  1. Capacitive-coupled static synchronous compensator (C-STATCOM)
  2. Hybrid static synchronous compensator (hybrid-STATCOM)
  3. Static synchronous compensator (STATCOM)
  4. Wide compensation range
  5. Low DC-link voltage

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 image001

Fig. 1. Circuit configuration of the hybrid-STATCOM.

 EXPECTED SIMULATION RESULTS:

 image002

Fig. 2. Dynamic compensation waveforms of load voltage, source current, and load and source reactive powers by applying hybrid-STATCOM under different loadings cases.

image003

Fig. 3 Dynamic compensation waveforms of vx and isx by applying hybrid-STATCOM under (a) inductive load, (b) capacitive load and (c) changing from capacitive load to inductive load.

image004

Fig. 4. Dynamic compensation waveforms of vx and isx by applying hybrid-STATCOM under unbalanced loads.

image005

Fig. 5. Dynamic compensation waveforms of vx and isx by applying hybrid-STATCOM under voltage fault condition.

image005

Fig. 6. Dynamic compensation waveforms of vx and isx by applying hybrid-STATCOM during voltage dip.

 CONCLUSION:

In this paper, a hybrid-STATCOM in three-phase power system is planned and discussed as a cost-effective reactive power compensator for medium voltage level application. The system configuration and V-I quality of the hybrid-STATCOM are analyzed, discussed, and compared with traditional STATCOM and C-STATCOM.

PARAMETER

In addition, its parameter design method is planned on the basis of application of the reactive power benefit range and prevention of a potential resonance problem. Moreover, the control strategy of the hybrid-STATCOM is developed under different voltage and current conditions.

HYBRID STATCOM

Finally, the wide benefit range and low DC-link voltage quality with good dynamic work of the hybrid-STATCOM are proved by both simulation and experimental results.

 REFERENCES:

[1] J. Dixon, L. Moran, J. Rodriguez, and R. Domke, “Reactive power compensation technologies: State-of-the-art review,” Proc. IEEE, vol. 93, no. 12, pp. 2144–2164, Dec. 2005.

[2] L. Gyugyi, R. A. Otto, and T. H. Putman, “Principles and applications of static thyristor-controlled shunt compensators,” IEEE Trans. Power App. Syst., vol. PAS-97, no. 5, pp. 1935–1945, Sep./Oct. 1978.

[3] T. J. Dionise, “Assessing the performance of a static var compensator for an electric arc furnace,” IEEE Trans. Ind. Appl., vol. 50, no. 3, pp. 1619–1629, Jun. 2014.a

[4] F. Z. Peng and J. S. Lai, “Generalized instantaneous reactive power theory for three-phase power systems,” IEEE Trans. Instrum. Meas., vol. 45, no. 1, pp. 293–297, Feb. 1996.

[5] L. K. Haw, M. S. Dahidah, and H. A. F. Almurib, “A new reactive current reference algorithm for the STATCOM system based on cascaded multilevel inverters,” IEEE Trans. Power Electron., vol. 30, no. 7, pp. 3577–3588, Jul. 2015.

A Novel Control Method for Transformerless H-Bridge Cascaded STATCOM With Star Configuration

 

ABSTRACT:

 This paper presents a transformerless static synchronous compensator (STATCOM) system based on multilevel H-bridge converter with star configuration. This proposed control methods devote themselves not only to the current loop control but also to the dc capacitor voltage control. With regards to the current loop control, a nonlinear controller based on the passivity-based control (PBC) theory is used in this cascaded structure STATCOM for the first time. As to the dc capacitor voltage control, overall voltage control is realized by adopting a proportional resonant controller. Clustered balancing control is obtained by using an active disturbances rejection controller. Individual balancing control is achieved by shifting the modulation wave vertically which can be easily implemented in a field-programmable gate array. Two actual H-bridge cascaded STATCOMs rated at 10 kV 2 MVA are constructed and a series of verification tests are executed. The experimental results prove that H-bridge cascaded STATCOM with the proposed control methods has excellent dynamic performance and strong robustness. The dc capacitor voltage can be maintained at the given value effectively.

KEYWORDS

 

  1. Active disturbances rejection controller (ADRC)
  2. H-bridge cascaded
  3. Passivity-based control (PBC)
  4. Proportional resonant (PR) controller
  5. Shifting modulation wave
  6. Static synchronous compensator (STATCOM).

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

image001Fig 1.Configuration of the experimental system.

EXPECTED SIMULATION RESULTS:

 image002

Fig. 2. Experimental results verify the effect of PBC in steady-state process. (a) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid. (b) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

image003

Fig. 3. Experimental results show the dynamic performance of STATCOM in the dynamic process. Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

image004

Fig. 4. Experimental results in the startup process and stopping process. (a) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid. (b) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

image005

Fig. 5. Experimental waveforms for testing overall voltage control in the startup process.

 CONCLUSION:

 This paper has analyzed the fundamentals of STATCOM based on multilevel H-bridge converter with star configuration. And then, the actual H-bridge cascaded STATCOM rated at 10 kV 2 MVA is constructed and the novel control methods are also proposed in detail. The proposed methods has the following characteristics.

1) A PBC theory-based nonlinear controller is first used in STATCOM with this cascaded structure for the current loop control, and the viability is verified by the experimental results.

2) The PR controller is designed for overall voltage control and the experimental result proves that it has better performance in terms of response time and damping profile compared with the PI controller.

3) The ADRC is first used in H-bridge cascaded STATCOM for clustered balancing control and the experimental results verify that it can realize excellent dynamic compensation for the outside disturbance.

4) The individual balancing control method which is realized by shifting the modulation wave vertically can be easily implemented in the FPGA.

The experimental results have confirmed that the proposed methods are feasible and effective. In addition, the findings of this study can be extended to the control of any multilevel voltage source converter, especially those with H-bridge cascaded structure.

REFERENCES:

 [1] B. Gultekin and M. Ermis, “Cascaded multilevel converter-based transmission STATCOM: System design methodology and development of a 12 kV ±12 MVAr power stage,” IEEE Trans. Power Electron., vol. 28, no. 11, pp. 4930–4950, Nov. 2013.

[2] B. Gultekin, C. O. Gerc¸ek, T. Atalik, M. Deniz, N. Bic¸er, M. Ermis, K. Kose, C. Ermis, E. Koc¸, I. C¸ adirci, A. Ac¸ik, Y. Akkaya, H. Toygar, and S. Bideci, “Design and implementation of a 154-kV±50-Mvar transmission STATCOM based on 21-level cascaded multilevel converter,” IEEE Trans. Ind. Appl., vol. 48, no. 3, pp. 1030–1045, May/Jun. 2012.

[3] S. Kouro, M. Malinowski, K. Gopakumar, L. G. Franquelo, J. Pou, J. Rodriguez, B.Wu,M. A. Perez, and J. I. Leon, “Recent advances and industrial applications of multilevel converters,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2553–2580, Aug. 2010.

[4] F. Z. Peng, J.-S. Lai, J. W. McKeever, and J. VanCoevering, “A multilevel voltage-source inverter with separate DC sources for static var generation,” IEEE Trans. Ind. Appl., vol. 32, no. 5, pp. 1130–1138, Sep./Oct. 1996.

[5] Y. S. Lai and F. S. Shyu, “Topology for hybrid multilevel inverter,” Proc. Inst. Elect. Eng.—Elect. Power Appl., vol. 149, no. 6, pp. 449–458, Nov. 2002.

A Novel Control Method for Transformerless H-Bridge Cascaded STATCOM with Star Configuration

ABSTRACT

This paper presents a transformerless static synchronous compensator (STATCOM) system based on multilevel H-bridge converter with star configuration. This proposed control methods devote themselves not only to the current loop control but also to the dc capacitor voltage control. With regards to the current loop control, a nonlinear controller based on the passivity-based control (PBC) theory is used in this cascaded structure STATCOM for the first time. As to the dc capacitor voltage control, overall voltage control is realized by adopting a proportional resonant controller. Clustered balancing control is obtained by using an active disturbances rejection controller. Individual balancing control is achieved by shifting the modulation wave vertically which can be easily implemented in a field-programmable gate array. Two actual H-bridge cascaded STATCOMs rated at 10 kV 2 MVA are constructed and a series of verification tests are executed. The experimental results prove that H-bridge cascaded STATCOM with the proposed control methods has excellent dynamic performance and strong robustness. The dc capacitor voltage can be maintained at the given value effectively.

 

KEYWORDS:

Active disturbances rejection controller (ADRC), H-bridge cascaded, passivity-based control (PBC), proportional resonant (PR) controller, shifting modulation wave, static synchronous compensator (STATCOM).

 

SOFTWARE: MATLAB/SIMULINK

 

CONTROL BLOCK DIAGRAM:

image001

Fig. 1. Control block diagram for the 10 kV 2 MVA H-bridge cascaded STATCOM.

 image002

Fig. 2. Block diagram of PBC.

 

EXPERIMENTAL RESULTS:

image003 image004

Fig. 3. Experimental results verify the effect of PBC in steady-state process. (a) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid. (b) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

 image005

Fig. 4. Experimental results show the dynamic performance of STATCOM in the dynamic process. Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

image006 image007

Fig. 5. Experimental results in the startup process and stopping process. (a) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid. (b) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

 

CONCLUSION

This paper has analyzed the fundamentals of STATCOM based on multilevel H-bridge converter with star configuration. And then, the actual H-bridge cascaded STATCOM rated at 10 kV 2 MVA is constructed and the novel control methods are also proposed in detail. The proposed method has the following characteristics.

1) A PBC theory-based nonlinear controller is first used in STATCOM with this cascaded structure for the current loop control, and the viability is verified by the experimental results.

2) The PR controller is designed for overall voltage control and the experimental result proves that it has better performance in terms of response time and damping profile compared with the PI controller.

3) The ADRC is first used in H-bridge cascaded STATCOM for clustered balancing control and the experimental results verify that it can realize excellent dynamic compensation for the outside disturbance.

4) The individual balancing control method which is realized by shifting the modulation wave vertically can be easily implemented in the FPGA.

The experimental results have confirmed that the proposed methods are feasible and effective. In addition, the findings of this study can be extended to the control of any multilevel voltage source converter, especially those with H-bridge cascaded structure.

 

REFERENCES

[1] B. Gultekin and M. Ermis, “Cascaded multilevel converter-based transmission STATCOM: System design methodology and development of a 12 kV ±12 MVAr power stage,” IEEE Trans. Power Electron., vol. 28, no. 11, pp. 4930–4950, Nov. 2013.

[2] B. Gultekin, C. O. Gerc¸ek, T. Atalik, M. Deniz, N. Bic¸er, M. Ermis, K. Kose, C. Ermis, E. Koc¸, I. C¸ adirci, A. Ac¸ik, Y. Akkaya, H. Toygar, and S. Bideci, “Design and implementation of a 154-kV±50-Mvar transmission STATCOM based on 21-level cascaded multilevel converter,” IEEE Trans. Ind. Appl., vol. 48, no. 3, pp. 1030–1045, May/Jun. 2012.

[3] S. Kouro, M. Malinowski, K. Gopakumar, L. G. Franquelo, J. Pou, J. Rodriguez, B.Wu,M. A. Perez, and J. I. Leon, “Recent advances and industrial applications of multilevel converters,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2553–2580, Aug. 2010.

[4] F. Z. Peng, J.-S. Lai, J. W. McKeever, and J. VanCoevering, “A multilevel voltage-source inverter with separateDCsources for static var generation,” IEEE Trans. Ind. Appl., vol. 32, no. 5, pp. 1130–1138, Sep./Oct. 1996.

[5] Y. S. Lai and F. S. Shyu, “Topology for hybrid multilevel inverter,” Proc. Inst. Elect. Eng.—Elect. Power Appl., vol. 149, no. 6, pp. 449–458, Nov. 2002.

A Novel Control Method for Transformerless H-Bridge Cascaded STATCOM with Star Configuration

ABSTRACT

This paper presents a transformerless static synchronous compensator (STATCOM) system based on multilevel H-bridge converter with star configuration. This proposed control methods devote themselves not only to the current loop control but also to the dc capacitor voltage control. With regards to the current loop control, a nonlinear controller based on the passivity-based control (PBC) theory is used in this cascaded structure STATCOM for the first time. As to the dc capacitor voltage control, overall voltage control is realized by adopting a proportional resonant controller. Clustered balancing control is obtained by using an active disturbances rejection controller. Individual balancing control is achieved by shifting the modulation wave vertically which can be easily implemented in a field-programmable gate array. Two actual H-bridge cascaded STATCOMs rated at 10 kV 2 MVA are constructed and a series of verification tests are executed. The experimental results prove that H-bridge cascaded STATCOM with the proposed control methods has excellent dynamic performance and strong robustness. The dc capacitor voltage can be maintained at the given value effectively.

 KEYWORDS:

Active disturbances rejection controller (ADRC), H-bridge cascaded, passivity-based control (PBC), proportional resonant (PR) controller, shifting modulation wave, static synchronous compensator (STATCOM).

 SOFTWARE: MATLAB/SIMULINK

 CONTROL BLOCK DIAGRAM:

image002

Fig. 1. Control block diagram for the 10 kV 2 MVA H-bridge cascaded STATCOM.

 image004

Fig. 2. Block diagram of PBC.

EXPERIMENTAL RESULTS:

image006

image008

Fig. 3. Experimental results verify the effect of PBC in steady-state process. (a) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid. (b) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

 image010

Fig. 4. Experimental results show the dynamic performance of STATCOM in the dynamic process. Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

image012

image014

Fig. 5. Experimental results in the startup process and stopping process. (a) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid. (b) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

CONCLUSION

This paper has analyzed the fundamentals of STATCOM based on multilevel H-bridge converter with star configuration. And then, the actual H-bridge cascaded STATCOM rated at 10 kV 2 MVA is constructed and the novel control methods are also proposed in detail. The proposed method has the following characteristics.

1) A PBC theory-based nonlinear controller is first used in STATCOM with this cascaded structure for the current loop control, and the viability is verified by the experimental results.

2) The PR controller is designed for overall voltage control and the experimental result proves that it has better performance in terms of response time and damping profile compared with the PI controller.

3) The ADRC is first used in H-bridge cascaded STATCOM for clustered balancing control and the experimental results verify that it can realize excellent dynamic compensation for the outside disturbance.

4) The individual balancing control method which is realized by shifting the modulation wave vertically can be easily implemented in the FPGA.

The experimental results have confirmed that the proposed methods are feasible and effective. In addition, the findings of this study can be extended to the control of any multilevel voltage source converter, especially those with H-bridge cascaded structure.

REFERENCES

[1] B. Gultekin and M. Ermis, “Cascaded multilevel converter-based transmission STATCOM: System design methodology and development of a 12 kV ±12 MVAr power stage,” IEEE Trans. Power Electron., vol. 28, no. 11, pp. 4930–4950, Nov. 2013.

[2] B. Gultekin, C. O. Gerc¸ek, T. Atalik, M. Deniz, N. Bic¸er, M. Ermis, K. Kose, C. Ermis, E. Koc¸, I. C¸ adirci, A. Ac¸ik, Y. Akkaya, H. Toygar, and S. Bideci, “Design and implementation of a 154-kV±50-Mvar transmission STATCOM based on 21-level cascaded multilevel converter,” IEEE Trans. Ind. Appl., vol. 48, no. 3, pp. 1030–1045, May/Jun. 2012.

[3] S. Kouro, M. Malinowski, K. Gopakumar, L. G. Franquelo, J. Pou, J. Rodriguez, B.Wu,M. A. Perez, and J. I. Leon, “Recent advances and industrial applications of multilevel converters,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2553–2580, Aug. 2010.

[4] F. Z. Peng, J.-S. Lai, J. W. McKeever, and J. VanCoevering, “A multilevel voltage-source inverter with separateDCsources for static var generation,” IEEE Trans. Ind. Appl., vol. 32, no. 5, pp. 1130–1138, Sep./Oct. 1996.

[5] Y. S. Lai and F. S. Shyu, “Topology for hybrid multilevel inverter,” Proc. Inst. Elect. Eng.—Elect. Power Appl., vol. 149, no. 6, pp. 449–458, Nov. 2002.