A Common Capacitor Based Three Level STATCOM and Design of DFIG Converter for a Zero-Voltage Fault Ride-Through Capability

ABSTRACT:

To meet the augmented load power demand, the doubly-fed induction generator (DFIG) based wind electrical power conversion system (WECS) is a better alternative. Further, to enhance the power flow capability and raise security margin in the power system, the STATCOM type FACTS devices can be adopted as an external reactive power source. In this paper, a three-level STATCOM coordinates the system with its dc terminal voltage is connected to the common back-to-back converters. Hence, a lookup table-based control scheme in the outer control loops is adopted in the Rotor Side Converter (RSC) and the grid side converter (GSC) of DFIG to improve power flow transfer and better dynamic as well as transient stability. Moreover, the DC capacitor bank of the STATCOM and DFIG converters connected to a common dc point. The main objectives of the work are to improve voltage mitigation, operation of DFIG during symmetrical and asymmetrical faults, and limit surge currents. The DFIG parameters like winding currents, torque, rotor speed are examined at 50%, 80% and 100% comparing with earlier works. Further, we studied the DFIG system performance at 30%, 60%, and 80% symmetrical voltage dip. Zero-voltage fault ride through is investigated with proposed technique under symmetrical and asymmetrical LG fault for super-synchronous (1.2 p.u.) speed and sub-synchronous (0.8 p.u.) rotor speed. Finally, the DFIG system performance is studied with different phases to ground faults with and without a three-level STATCOM.

KEYWORDS:

  1. Doubly-fed induction generator (DFIG)
  2. Field oriented control (FOC)
  3. Common-capacitor based STATCOM
  4. Voltage compensation
  5. Balanced and unbalanced faults
  6. Zero-voltage fault ride through

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Figure 1. Grid-Connected DFIG With Three Levels Statcom Converter.

EXPECTED SIMULATION RESULTS:

Figure 2. DFIG Operation With 50% Voltage Dip (I) Using Method In [27]. And (Ii) Using Proposed Method.

Figure 3. DFIG Operation With 50% Voltage Dip (I) Using Method In [28] And (Ii) Using Proposed Method.

Figure 4. DFIG Operation With (I) 30% Dip, (Ii) 60% Dip And (Iii) 80% Dip In Grid Voltage.

Figure 5. Rotor, Stator Gsc And Grid Terminal Current Waveforms With The Proposed Technique With Slg Fault.

CONCLUSION:

A generalized DFIG wind energy conversion system based test-bed system connected to the grid is considered in the paper. The work tested in the starting cases with two different research papers works with proposed method under an 80% dip. Later, proposed methodology compared under 30%, 60%, and 80% dip, and the DFIG behavior is examined. Further, under three different cases, LG, LLG and LLG faults without and STATCOM are compared to show STATCOM controller’s effectiveness. An improved field-oriented control scheme for the DFIG with real and reactive power lookup-based control in the outer control loops. It is observed that, there is a rapid development in the back emf and decoupled current regime in the paper’s inner control loops is proposed. A three-level SATCOM is used in this paper, with the rectifier end dc-link connected to the common capacitor between the DFIG back-to-back converters. A better damping factor is observed for torque, powers, current, voltage, and speed at 60%, 80%, and 100% dip with the proposed scheme.

The proposed method employs the adjustment of external real and reactive powers using the optimal lookup table method as shown in Table 3, rotor speed, and terminal voltage in the outer control loops of both RSC and GSC. The inner control loop is fast-acting current control and back emf- based voltage injection near the decoupling voltage loop. The strategy works on decoupled real and reactive power flow controls in synchronous rotating frames leads to individual power control. This technique improves performance under normal conditions and during grid faults, with better rotor voltage control, rotor speed, and damping. The post-fault behavior of an overall system improved using the proposed technique.

Further improvement in the system behavior is observed with the common- dc link STATCOM. The rectifier end dc link is connected to the capacitor between the DFIG converters, which will reduce the cost for capacitor and measurement sensors. This paper demonstrates the DFIG-based WECS with better active and reactive power and EMT damping, surge current reduction, speed control, and effective LVRT capability. There are distortions in the rotor current waveform during the zero-voltage fault ride during the fault and considerably more when the rotor speed is at super synchronous speed. When the rotor speed is beyond the synchronous speed, the rotor current is injected into the stator terminal from the rotor side windings with RSC control scheme. Under this condition, the fault inrush current from the dc-link capacitor will pass through this rotor terminal and reach the stator windings. Under sub-synchronous speed, the rotor winding will receive the current for the stator windings, so the fault effect is less influenced at lower speeds than with higher speeds. The rotor voltage is maintained at both speeds during the LG fault. However, waveform is less distorted with lower rotor speed.

The dc-link voltage distortions during the fault are more with super- synchronous speed than sub-synchronous speed operation for zero voltage ride through. The dc-link voltage is more stubborn and stable when the rotor speed is lesser than the synchronous speed. The STATCOM current is observed to be more in faulty phase than with other two healthy phases. The reason and analysis are the same as that with the symmetrical fault study. The deviation of the fault current at the STATCOM terminal is re-injected to the grid via the closed path with the dc-link capacitor terminal. The post-fault performance is superior with a serious 100% voltage dip case and also found better dynamic response because of the RSC and GSC proposed technique and the STATCOM controller. Further, an effective operation is experienced with a common link dc capacitor STATCOM than with a conventional topology. Hence, simulated results show better performance and profitable operation during and after the faults than the earlier famous methods.

With the proposed method, rotor and stator current during fault are maintained, not getting zero value and limiting surge currents to a dangerous value. However, stator and rotor current is not supported to their pre-fault value during the fault period. The torque reduction to a smaller value observed increases the grid fault dip value, but there are no surges and oscillations with the proposed method. The rotor speed is also maintained almost constant even for significant voltage dip. As a result, the post fault recovery in the DFIG is smooth and instantaneous, observed for winding voltages, currents, EMT, active and reactive powers, dc-link capacitor voltage, and rotor speed.

All the objectives specified in the Introduction section are met 1) rotor and stator current surges are limited, current surges ate within 1.5 times the operating value, mitigation in the rotor voltage observed. Furthermore, the reactive power support by STATCOM, RSC and GSC improved the DFIG WECS during and after the fault. Thereby 1) enhancement in overall dynamic and transient stability is observed. 2) The rotor speed is almost constant even for a significant grid voltage dip which is better than many research papers. 3) The electromagnetic torque (EMT) and active and reactive power flow oscillations are damped completely, and sustainable control observed with the technique. 4) The proposed method is suitable for grid faults like symmetrical, asymmetrical, and recurring faults. Better DFIG performance is expected with LVRT capability for symmetrical and asymmetrical faults with future research activities.

REFERENCES:

[1] H. A. Mohammadpour, A. Ghaderi, H. Mohammadpour, and E. Santi, “SSR damping in wind farms using observed-state feedback control of DFIG converters,” Electr. Power Syst. Res., vol. 123, pp. 57_66, Jun. 2015.

[2] F. Blaabjerg and K. Ma, “Future on power electronics for wind turbine systems,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 1, no. 3, pp. 139_152, Sep. 2013.

[3] T. D. Vrionis, X. I. Koutiva, and N. A. Vovos, “A genetic algorithm based low voltage ride-through control strategy for grid connected doubly fed induction wind generators,” IEEE Trans. Power Syst., vol. 29, no. 3, pp. 1325_1334, May 2014.

[4] A. M. Eltamaly and H. M. Farh, “Maximum power extraction from wind energy system based on fuzzy logic control,” Electr. Power Syst. Res., vol. 97, pp. 144_150, Apr. 2013.

[5] Y. Weng and Y. Hsu, “Sliding mode regulator for maximum power tracking and copper loss minimisation of a doubly fed induction generator,” IET Renew. Power Gener., vol. 9, no. 4, pp. 297_305, May 2015.

A Novel V2V Charging Method Addressing the Last Mile Connectivity

ABSTRACT:

One of the main drawbacks in adopting EV vehicles is the last mile connectivity issue. There is always a chance that the user/rider may get stranded without EV charge and no EV charging stations nearby. With the aim of solving such an exigency, this paper proposes a novel V2V charging technique which allows charge transfer between two EVs off the grid, and discusses its modes of operation. Non-isolated bidirectional DC-DC converters with average current control technique are simulated in a MATLAB/Simulink environment to verify and validate the efficiency and charging time for the proposed charging technique.

KEYWORDS:

  1. V2V charging
  2. Bi-directional converter
  3. Pricing strategy

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1: Block diagram of V2V technology

EXPECTED SIMULATION RESULTS:

Figure 2: SOC% plots where higher SOC battery is charging and lower SOC battery is discharging

Figure 3: SOC% plots where higher SOC battery is discharging and lower SOC battery is charging

CONCLUSION:

A V2V charging scheme is proposed to synchronize the charging between two electric vehicles. This is particularly needed when an EV user is left stranded without battery charge and with no access to EV charging station. In this scenario, the proposed model allows another EV user to assist the stranded EV by charging from his EV thus solving last mile connectivity issues. The proposed model consists of a dual converter in the electric vehicle which enables fast DC charging or discharging. Extensive MATLAB simulation results on the model proves that the proposed work is capable of charging an EV from another under average current control method. The efficiency, SOC status and charging time for the proposed method is also analyzed. From the analysis it is evident that as the SOC difference increases the efficiency obtained also increases. To reduce the charging time and to enhance the efficiency average current control method is simulated and analyzed. The results obtained are presented and the results confirm the effectiveness of the proposed work.

V2V energy transfers which were reported in the earlier literature uses the concept of connected ad-hoc networks present in parking lots etc., where the vehicles parked in the parking lot are used for energy transfer through a connected bus in the parking lot itself. The term ‘novel’ has been used here as the issue of EV being left stranded without battery charge and with no access to charging station is not addressed anywhere in the literature and also the technique of using cascaded bi-directional converters for charging one vehicle from the other vehicle adds novelty to the V2V energy transfer. Cascaded Bidirectional converters can even facilitate the charge transfer when the electric vehicles battery voltage levels are different, that’s why cascaded converters has been employed.

REFERENCES:

[1] Markel, T., Saxena. S, Kahl. K, Pratt. R, “Multi-Lab EV Smart Grid Integration Requirements Study: Providing Guidance on Technology Development and Demonstration”, National Renewable Energy Laboratory. Retrieved 2016-03-08, 2005.

[2] Liu, Wei-Shih, Jiann-Fuh Chen, Tsorng-Juu Liang, Ray-Lee Lin, and Ching-Hsiung Liu, “Analysis, design, and control of bidirectional cascaded configuration for a fuel cell hybrid power system,” IEEE Transactions on Power Electronics 25,Vol. 6, 2010, pp no:- 1565-1575.

[3] Akshya, S., Anjali Ravindran, A. Sakthi Srinidhi, Subham Panda, and Anu G. Kumar, “Grid integration for electric vehicle and photovoltaic panel for a smart home.” 2017 International Conference on Circuit, Power and Computing Technologies (ICCPCT), pp. 1-8, 2017.

[4] Nagar, Ishan, M. Rajesh, and P. V. Manitha, “A low cost energy usage recording and billing system for electric vehicle,” International Conference on Inventive Communication and Computational Technologies (ICICCT), pp. 382-384, 2017.

[5] Rajalakshmi, B., U. Soumya, and Anu G. Kumar. “Vehicle to grid bidirectional energy transfer: Grid synchronization using Hysteresis Current Control”, International Conference on Circuit, Power and Computing Technologies (ICCPCT), pp. 1-6, 2017.

A New Five-Level Buck-Boost Active Rectifier

ABSTRACT:

In this paper a new single-phase five-level buck boost active rectifier is introduced called capacitor tied switches (CTS). The proposed rectifier has two independent DC outputs that can be connected to two different loads. Different switching states and the average mode of the proposed topology are analyzed to design the associated controller aims at regulating the two output DC voltages, generating five-level voltage at the input of the rectifier and finally draw unity power factor and sinusoidal current from AC grid. From AC grid view, the rectifier works in boost mode however the generated DC voltage can be split into two separate outputs which may be less than the AC peak voltage or even more leads to work in both buck and boost operation mode. Full simulation results are shown and analyzed to validate the effective operation and good dynamic performance of the proposed five-level buck-boost rectifier.

KEYWORDS:

  1. Multilevel converter
  2. Packed U-Cell
  3. Active PFC rectifier
  4. Buck-boost rectifier
  5. Capacitor Tied Switches (CTS)

SOFTWARE: MATLAB/SIMULINK

PROPOSED DIAGRAM:

Figure 1: proposed five-level buck-boost PFC rectifier (CTS)

EXPECTED SIMULATION RESULTS:

Figure 2: simulation results during change in DC voltages from 100 V to 200 V (transition between buck and boost modes). a) vs and is *current waveform multiplied by 4 b) power factor c) input voltage of the CTS rectifier Vad d) V1 e) V2

Figure 3: harmonic spectrum of Vad and is in buck mode (100 V DC output)

Figure 4: harmonic spectrum of Vad and is in boost mode (200 V DC output)

Figure 5: simulation results during load changes in buck mode. A) vs and is *current waveform is multiplied by 15 b) input voltage of the CTS rectifier Vad

c) V1 d) i1 e) V2 f) i2

Figure 6: simulation results during the loads changes in boost mode. A) vs and is *current waveform is multiplied by 15 b) input voltage of the CTS rectifier Vad

c) V1 d) i1 e) V2 f) i2

CONCLUSION:

In this paper a new topology of buck-boost active rectifier has been introduced based on slight modification of the third U-cell of the PUC original design. The proposed rectifier called CTS includes six switches tied by two capacitors as two output independent DC terminals and generates five-level voltage waveform at the input. The latter draw low harmonic current in-phase with the grid voltage making the operation at unity power factor rectifier easy in both buck and boost mode. This topology does not need additional bulky filters while switching at low frequency which constitute a big advantage of the presented CTS rectifier. Simulation results including regulated DC voltages, high power factor, and low supply THD current mainly obtained by the five-level rectifier input voltage. Moreover, good dynamic performance, fast response and reliable operation of the implemented controller and CTS converter topology were proven and discussed in details.

REFERENCES:

[1] B. Singh, B. N. Singh, A. Chandra, K. Al-Haddad, A. Pandey, and D. P. Kothari, “A review of single-phase improved power quality ACDC converters,” Industrial Electronics, IEEE Transactions on, vol. 50, pp. 962-981, 2003.

[2] B. Singh, B. N. Singh, A. Chandra, K. Al-Haddad, A. Pandey, and D. P. Kothari, “A review of three-phase improved power quality AC-DC converters,” Industrial Electronics, IEEE Transactions on, vol. 51, pp. 641-660, 2004.

[3] H. Abu-Rub, M. Malinowski, and K. Al-Haddad, Power electronics for renewable energy systems, transportation and industrial applications: John Wiley & Sons, 2014.

[4] L. Yacoubi, K. Al-Haddad, L.-A. Dessaint, and F. Fnaiech, “Linear and nonlinear control techniques for a three-phase three-level NPC boost rectifier,” Industrial Electronics, IEEE Transactions on, vol. 53, pp. 1908-1918, 2006.

[5] L. Yacoubi, K. Al-Haddad, L.-A. Dessaint, and F. Fnaiech, “A DSPbased implementation of a nonlinear model reference adaptive control for a three-phase three-level NPC boost rectifier prototype,” Power Electronics, IEEE Transactions on, vol. 20, pp. 1084-1092, 2005.

The Fastest MPPT Tracking Algorithm for a PV array fed BLDC Motor Driven Air Conditioning system

ABSTRACT:

The fastest and novel adaptive voltage reference MPPT tracking algorithm for PV cluster sustained BLDC drive for aerating and cooling application is proposed in this paper. The fastest maximum power point tracking (MPPT) algorithm tracks the power instantaneously if there is any change in the solar irradiation. Low cost and energy efficiency is achieved by removing the conventional DC/DC boost converter stage which reduces the switching losses and further reduces the overall cost of the system thereby minimizing the power conversion stages. The proposed quickest MPPT algorithm for BLDC motor driven PV array fed air conditioning system is designed and modelled such that the performance is not affected even under the dynamic conditions. The proposed system is validated by simulation studies.

KEYWORDS:

  1. Instantaneous
  2. Low cost
  3. Efficient
  4. MPPT
  5. BLDC
  6. Air conditioner compressor

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Block diagram of proposed system

EXPECTED SIMULATION RESULTS:

Fig. 2. Speed of BLDC Motor

Fig. 3. Torque of BLDC Motor

(a)

(b)

(c)

Fig. 4. stator back emf’s in phase a, phase b, phase c

(a)

(b)

(c)

Fig. 5. Stator currents in phase a,phase b, phase c

Fig. 6. Solar Insolation input for PV panel\

Fig. 7. PV panel Current(Ipv)Amps

Fig. 8. PV panel Power (watts)

Fig. 9. Tracking of MPPT power

Fig. 10. PV panel Voltage (Vpv) volts

CONCLUSION:

 In this study, a novel adaptive constant voltage reference MPPT technique was proposed to extort maximum power from solar panels and simultaneously uses PV voltage and current deviations to track the Maximum power point of a PV array under varying irradiance conditions has been presented in this paper. The fastest MPPT algorithm is simulated and discussed to extract maximum power from solar panels without using DC-DC converters thereby reducing switching losses which in turn increases r efficiency and reduces the cost for PV array fed BLDC Motor driven air conditioning system. The MATLAB simulation results effectively exhibit that, the proposed adaptive constant voltage MPPT algorithm works fine and shows good dynamic and steady state performance.

REFERENCES:

[1] Rodrigo A. Gonzalez, Marcelo A. Perez, Hugues Renaudineau and Freddy Flores-Bahamonde, “Fast Maximum Power Point Tracking Algorithm based on Switching Signals Modification,” IEEE International Conference on Compatibility, Power Electronics and Power Engineering (CPE-POWERENG), pp. 448-453, 4-6 April 2017.

[2] Hassan Fathabadi, “Novel fast dynamic MPPT (maximum power point tracking) technique with the capability of very high accurate power tracking,”Elsevier journal Energy., Vol. 94, pp. 466-475, Jan. 2016.

[3] E. Mamarelis, G. Petrone and G. Spagnuolo, “Capacitor Peak Current Control for MPPT Photovoltaic Applications,” 39th Annual Conference of the IEEE Industrial Electronics Society, pp. 3347–3352, Nov 2013.

[4] Arash Kalantari , A.Rahmati and A.Abrishamifar, “A Faster Maximum Power Point Tracker Using Peak Current Control,” IEEE Symposium on Industrial Electronics and Applications, pp. 117–122, October 4-6, 2009.

[5] Neil S. D’Souza, Luiz A. C. Lopes, and Xuejun Liu, “Peak Current Control Based Maximum Power Point Trackers For Faster Transient  Responses,” Canadian Conference on Electrical and ComputerEngineering on 7-10 May 2006.

Real-Time Implementation of Model Predictive Control on 7-Level Packed U-Cell Inverter

ABSTRACT:

In this paper a model predictive control (MPC) has been designed and implemented on the Packed U-Cell (PUC) inverter which has one isolated DC source and one capacitor as an auxiliary DC link. The MPC is designed to regulate the capacitor voltage at the desired magnitude to have seven voltage levels at the output of the inverter. Since grid-connected application is targeted by this application, the inverter should be capable of supplying requested amount of active and reactive power at the point of common coupling (PCC) as well. Therefore, MPC should also consider the line current control in order to monitor the exchange of reactive power with the grid while injecting appropriate active power at low THD. Various experimental tests including change in DC source voltage, active power variation and operation at different power factor (PF) have been performed on a laboratory prototype to validate the good performance obtained by the proposed MPC. The dynamic performance of the controller during sudden changes in dc capacitor voltage, supply current and PF demonstrates the fast and accurate response and the superior operation of the proposed controller.

KEYWORDS:

  1. PUC Inverter
  2. Multilevel Inverter
  3. Model Predictive Control
  4. Grid-Connected PV
  5. Power Quality

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. General Scheme for MPC

EXPECTED SIMULATION RESULTS:

Fig. 2. Steady state voltage and current waveforms for grid-connected PUC.

Fig. 3 Results during 20% grid voltage variation (from 140V to 110V peak).

Fig. 4. Response to transient DC bus voltage changes.

Fig. 5. Controller response to reactive power variations.

Fig. 6. Experimental results showing grid current reference amplitude 100%

increase and thereafter 50% decrease.

CONCLUSION:

In this paper, a Model Predictive Control has been designed for the 7-level PUC inverter in grid-connected mode of operation, an excellent candidate for photovoltaic and utility interface application to deliver green power to the utility. MPC is a simple and intuitive method that does not have confusing gains to adjust as well as featuring fast response during any change in the system parameters. Experimental results have been provided to show the fast response of the implemented controller on the grid-connected multilevel PUC inverter. It has been demonstrated that the DC link capacitor voltage has been regulated at desired level and 7-level voltage waveform has been generated at the output of the inverter. The injected current to the grid was successfully controlled to have regulated amplitude and synchronized waveform with the grid voltage to deliver maximum power with unity power factor. Moreover, the PF has been controlled easily to exchange reactive power with the grid while injecting the available active power. Exhaustive experimental results including change in the grid current reference, DC source and AC grid voltages variations, as well as PF have been tested and results have been illustrated which ensured the good dynamic performance of the proposed controller applied on the grid connected PUC inverter.

REFERENCES:

[1] H. Abu-Rub, M. Malinowski, and K. Al-Haddad, Power electronics for renewable energy systems, transportation and industrialapplications: John Wiley & Sons, 2014.

[2] H. Mortazavi, H. Mehrjerdi, M. Saad, S. Lefebvre, D. Asber, and L. Lenoir, “A Monitoring Technique for Reversed Power Flow Detection With High PV Penetration Level,” IEEE Trans. Smart Grid, vol. 6, no. 5, pp. 2221-2232, 2015.

[3] J. M. Carrasco, L. G. Franquelo, J. T. Bialasiewicz, E. Galván, R. P. Guisado, M. A. Prats, J. I. León, and N. Moreno-Alfonso, “Powerelectronic systems for the grid integration of renewable energy sources: A survey,” IEEE Trans. Ind. Electron., vol. 53, no. 4, pp. 1002-1016, 2006.

[4] M. G. Kashani, M. Mobarrez, and S. Bhattacharya, “Variable interleaving technique for photovoltaic cascaded DC-DC converters,” in IECON 2014-40th Annual Conference of the IEE EIndustrial Electronics Society, 2014, pp. 5612-5617.

[5] M. Mobarrez, M. G. Kashani, G. Chavan, and S. Bhattacharya, “A Novel Control Approach for Protection of Multi-Terminal VSC based HVDC Transmission System against DC Faults,” in ECCE 2015- Energy Conversion Congress & Exposition, Canada, 2015, pp. 4208- 4213.

PUC Converter Review: Topology, Control and Applications

ABSTRACT:

Packed U-Cell (PUC) converter has been introduced as a 7-level converter in early 2008. Since then, different analysis and projects have been performed on, including various applications such as inverter and rectifier, linear and nonlinear voltage controllers. In this paper, authors try to do a detail review on this topology covering all aspects like topology design in single and three-phase, operation concepts, switching sequences for different multilevel voltage waveform generation, modelling and etc. It is shown that this topology can be comparable to popular multilevel converters (CHB and NPC) in terms of device counts and applications. Moreover, some performed and published works about the PUC are mentioned to show its different industrial applications and some other converter topologies derived based on the PUC. Experimental results are provided to show the good performance of PUC converter in several applications.

KEYWORDS:

  1. Packed U-Cell
  2.  Multilevel converter
  3. Active power filter
  4. Active rectifier
  5.  Inverter
  6. Power quality

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Three-phase 3-wire/4-wire configuration of PUC inverter

EXPECTED SIMULATION RESULTS:

Fig. 2. Test results of a 7-Level PUC rectifier

Fig. 3. Test results of a sensor-less 5-Level PUC standalone inverter

Fig. 4. Test results of a Sensor-less 5-Level PUC grid-connected inverter

Fig. 5. Experimental results of 5-level PUC converter as STATCOM

Fig. 6. Three-phase 5-level PUC inverter voltage and current waveforms

CONCLUSION:

PUC converter generates various voltage levels based on the voltage ratio of its two DC links similar to the CHB topology, while using fewer components. It is an interesting topology in inverter mode due to using only one isolated DC source. It is also attractive in rectifier application because of generating dual output DC terminal in boost and buck mode. As shown in this paper, the PUC converter can be a good candidate for all modes of operation like standalone/grid-connected inverter and rectifier in various applications including PV systems, active filters, wind turbine, electric transportation, battery chargers, MMC, etc.

REFERENCES:

[1] S. Kouro, M. Malinowski, K. Gopakumar, J. Pou, L. G. Franquelo, B. Wu, et al., “Recent advances and industrial applications of multilevel converters,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2553-2580, 2010.

[2] H. Abu-Rub, J. Holtz, J. Rodriguez, and G. Baoming, “Medium-voltage multilevel converters—State of the art, challenges, and requirements in industrial applications,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2581-2596, 2010.

[3] H. Abu-Rub, M. Malinowski, and K. Al-Haddad, Power electronics for renewable energy systems, transportation and industrial applications: John Wiley & Sons, 2014.

[4] J. Rodriguez, S. Bernet, P. K. Steimer, and I. E. Lizama, “A survey on neutralpoint- clamped inverters,” IEEE Trans. Ind. Electron., vol. 57, no. 7, pp. 2219- 2230, 2010.

[5] M. Malinowski, K. Gopakumar, J. Rodriguez, and M. A. Perez, “A survey on cascaded multilevel inverters,” IEEE Trans. Ind. Electron., vol. 57, no. 7, pp. 2197-2206, 2010.

Real-Time Implementation of a Packed U-Cell Seven-Level Inverter with Low Switching Frequency Voltage Regulator

ABSTRACT:

In this paper a new cascaded nonlinear controller has been designed and implemented on the packed U-Cell (PUC) seven-level inverter. Proposed controller has been designed based on a simplified model of PUC inverter and consists of a voltage controller as outer loop and a current controller as inner loop. The outer loop regulates the PUC inverter capacitor voltage as the second DC bus. The inner loop is in charge of controlling the flowing current which is also used to charge and discharge that capacitor. The main goal of the whole system is to keep the DC capacitor voltage at a certain level results in generating a smooth and quasi-sine-wave 7-level voltage waveform at the output of the inverter with low switching frequency. The proposed controller performance is verified through experimental tests. Practical results prove the good dynamic performance of the controller in fixing the PUC capacitor voltage for various and variable load conditions and yet generating low harmonic 7-level voltage waveform to deliver power to the loads. Operation as an uninterruptible power supply (UPS) or AC loads interface for photovoltaic energy conversion applications is targeted.

KEYWORDS:

  1. Packed U-Cell
  2. Multilevel Inverter
  3. Voltage Balancing
  4. Nonlinear Controller
  5. Renewable energy conversion

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Block diagram of proposed controller applied on 7-level PUC inverter

EXPECTED SIMULATION RESULTS:

Fig. 2. PUC inverter voltage and current waveforms in steady state condition

Fig. 3. Voltage regulation during a fast 66% increase in DC source amplitude

Fig. 4. Adding a nonlinear load (rectifier) to the PUC inverter while supplying an RL load

CONCLUSION:

In this paper a new cascaded nonlinear controller has been designed for 7-level PUC inverter based on the simple model derived by multilevel inverter topology concept. Experimental results showed appropriate dynamic performance of the proposed controller in stand-alone mode as UPS, renewable energy conversion system or motor drive applications. Different changes in the load and DC bus voltage have been made intentionally during the tests to challenge the controller reaction in tracking the voltage and current references. Proposed controller demonstrated satisfying performance in fixing the capacitor voltage of the PUC inverter, generating seven-level voltage with low harmonic content at the output of the PUC inverter and ensures low switching frequency operation of those switches. By applying the designed controller on the 7-level PUC inverter it can be promised to have a multilevel converter with maximum voltage levels while using less active switches and DC sources aims at manufacturing a low-cost converter with high efficiency, low switching frequency, low power losses and also low harmonic contents without using any additional bulky filters.

REFERENCES:

[1] H. Abu-Rub, M. Malinowski, and K. Al-Haddad, Power electronics for renewable energy systems, transportation and industrial applications: John Wiley & Sons, 2014.

[2] J. M. Carrasco, L. G. Franquelo, J. T. Bialasiewicz, E. Galván, R. P. Guisado, M. A. Prats, et al., “Power-electronic systems for the grid integration of renewable energy sources: A survey,” IEEE Trans. Ind. Electron., vol. 53, no. 4, pp. 1002-1016, 2006.

[3] M. Mobarrez, M. G. Kashani, G. Chavan, and S. Bhattacharya, “A Novel Control Approach for Protection of Multi-Terminal VSC based HVDC Transmission System against DC Faults,” in ECCE 2015- Energy Conversion Congress & Exposition, Canada, 2015, pp. 4208- 4213.

[4] B. Singh, A. Chandra, and K. Al-Haddad, Power Quality: Problems and Mitigation Techniques: John Wiley & Sons, 2014.

[5] 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, 1999.

Multicarrier-SPWM Based Novel 7-Level Inverter Topology with Photovoltaic System

 ABSTRACT:

In this paper a novel 5 switch seven level DC-AC inverter is being proposed. The proposed multilevel inverter uses reduced number of switches as compared to the switches used in the conventional multilevel inverter. The inverter has been designed to generate a 7 level AC output using 5 switches. The voltage stress on each of the switches as well as the switching losses is found to be less, minimized common mode voltage (CMV) level and reduced total harmonic distortion. The proposed 7-level inverter topology has four dc sources, which is energized through the PV system. Proposed inverter is controlled with help of multicarrier sinusoidal pulse width modulation (MCSPWM).The simulation and hardware results were verified using matlab simulink and dspic microcontroller respectively.

KEYWORDS:

  1. DsPIC controller
  2. Multicarrier sinusoidal pulse width modulation (MCSPWM)
  3. Multilevel inverter
  4. PV system

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Figure 1. Novel 7 Level 5switch inverter topology

EXPECTED SIMULATION RESULTS:

Figure 2. 7-level stepped output voltage of proposed system

Figure 3. Output current of proposed system inverter topology

Figure 4. Switching pulses generation using MCSPWM

Figure 5. Voltage across the switches placed in the proposed inverter

(a)

(b)

Figure 6. THD analysis of proposed system (a) output voltage (b) output current

CONCLUSION:

In this proposed paper, the multicarrier sinusoidal pulse width modulation scheme was implemented to produce a seven level stepped output voltage with reduced harmonics. The proposed inverter energized by using photovoltaic system, which boosted through the boost converter. Also this system which minimises the common mode voltage level, voltage stress across the various switches improves output and better current control is accomplished. And the simulation and experimental results were verified using matlab16 and dspic controller respectively.

REFERENCES:

[1] Poh Chiang Loh, Feng Gao, FredeBlaabjerg, and Sokweilim,” Operational Analysis and Modulation Control of Three-Level Z-Source Inverters With Enhanced Output Waveform Quality,”IEEE Transaction On Power Electronics, Vol.24, No.7, July 2009.

[2] SamirKouro, Pablo Lezana, Mauricio Angulo and José Rodríguez, ”Multicarrier PWM with Dc-Link Ripple Feedforward Compensation For Multilevel Inverters,” IEEE Transactions on Power Electronics, Vol. 23, No.1, January2010.

[3] S. Mohamed Yousuf, P. Vijayadeepan, Dr. S. Latha, “The Comparative THD Analysis of Neutral Clamped Multilevel Z-source Inverter Using Novel PWM Control Techniques” IJMER Vol.2, Issue.3, May-June 2012 pp-1086-1091.

[4] Huafeng Xiao, ShaojunXie, Chen Yang, “Transformerless Split-inductor Neutral point clamped Three-level PV Grid-Connected Inverter” IEEE Energy Conversion congress and Exposition (ECCE), 2010 pp. 2929-2936

[5] Bharatiraja, C., Raghu, S., Rao, P., Paliniamy, K.R.S. “Comparative analysis of different PWM techniques to reduce the common mode voltage in three-level neutral-point- clamped inverters for variable speed induction drives”, International Journal of Power Electronics and Drive Systems, vol. 3, Issue 1, March 2013, Pages 105-116.

Design and Simulation of Single-Phase Five-Level Symmetrical Cascaded H-Bridge Multilevel Inverter with Reduces Number of Switches

ABSTRACT:

Multilevel inverter is an effective and practical solution for increasing power demand and reducing harmonics of ac waveforms. Such inverters synthesize a desired output voltage from several levels of dc voltages as inputs. This paper analyzes the performance of five level cascaded H-bridge multilevel inverter with reduce number of power switches. Further by reducing switches and increasing level will reduce filter cost & harmonic content. 5- Level cascaded H-bridge asymmetrical multilevel inverter topology requires 8 switches but in this new multilevel inverter it requires 6 switches in which same multilevel is obtained. Invariably switching losses and cost also reduced. In this paper only multilevel inverter circuitry will be studied. The performance has been analyzed by the MATLAB/Simulink.

KEYWORDS:

  1. Cascaded multilevel inverter
  2. SPWM
  3. APOD
  4. PD
  5. POD
  6. THD

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Figure 1: Circuit diagram of 5-level CHB MLI with reduced switches & dc sources.

EXPECTED SIMULATION RESULTS:

Figure 2: Output waveform of 5-levels single phase symmetric CHB MLI.

Figure 3: 5-levels THD in MATLAB tool.

CONCLUSION:

This paper showed that this modified multilevel inverter topology with reduced number of switches can be implemented for industrial drive applications. This multilevel inverter structure and its basic operations have been analyzed. A detailed procedure for calculating required voltage level on each stage has been analyzed. As conventional five-level inverter involves eight switches, it increases switching losses; cost and circuit complexity. This 5-level inverter engages only six switches which reduces switching losses, cost and circuit complexity. Moreover it effectively reduces lower order harmonics. Therefore effective reduction of total harmonics distortion is achieved.

REFERENCES:

1. http://www.esru.strath.ac.uk

2. Kavita M, Arunkumar A, Gokulnath N, Arun S (2012) New cascaded H-bridge multilevel inverter topology with reduced number of switches and sources. IOSR-JEEE 2: 26-36.

3. Peng FZ, Lai JS (2003) Multilevel converters, A new breed of power Electronics converters. IEEE Trans Ind Appl 32: 509 -517.

4. Rodriguez J, Lai JS, Peng FZ (2003) Multilevel Inverter: A survey topology control and application. IEEE Trans Ind Electro 49: 724-738.

5. Nabae A, Takahashi I, Akagi H (2003) New neutral point clamped pwm inverter. IEEE Trans Ind Appl IA-17: 518-523.

Finite Control Set Model Predictive Control for Grid Connected Packed U Cells Multilevel Inverter

ABSTRACT:

 This paper presents a Finite Control Set Model Predictive Control (FCS-MPC) for grid-tied Packed U Cells (PUC) Multilevel Inverter (MLI). The system under study consists of a single-phase 3-cells PUC inverter connected to the grid through filtering inductor. The proposed competitive topology allows the generation of 7-level output voltage with reduction of passive and active components compared to the conventional multilevel inverters. The aim of the proposed FCS-MPC technique is to achieve, under various operating conditions, grid-tie current injection with unity power factor and low Total Harmonic Distortion (THD) while balancing the capacitor voltage. Parameters sensitivity analysis was also conducted. The study is conducted on a low power case study single-phase 3-cells PUC inverter and with possible extension to higher number of cells. Theoretical analysis, simulation, and experimental results are presented and compared.

KEYWORDS:

  1. Grid Connection
  2. Model Predictive Control
  3. Packed U Cells Inverter
  4. PUC

SOFTWARE: MATLAB/SIMULINK

PROPOSED CONTROLLER:

Fig. 1. Proposed controller for the 3-cell PUC

EXPECTED SIMULATION RESULTS:

Fig. 2. PV module measurements under irradiance step change

Fig. 3. Capacitor voltages waveforms

Fig. 4. Injected grid current waveforms

Fig. 5. Grid current THD

Fig. 6. Transient test, Upper: Output voltage waveform, Lower: Capacitor C2 voltage

Fig. 7. Transient test under a 100% irradiance step change, Upper: PV power, Middle: Grid current, Lower: Capacitor C1 and C2 voltages

CONCLUSION:

This paper presented the design, simulations, and experimental validation of a FCS-MPC technique that properly deals with the complex nature of the PUC. Digital simulation for a grid-connected 7-level single-phase PUC inverter was carried out. The simulation results showed that the proposed MPC is capable of simultaneously controlling multi variables of the PUC inverter. The tuning of the weighting factor was conducted successfully based on minimizing the grid current THD as well as the capacitor voltage error. Using the properly selected weighting factor, the MPC has shown an efficient and stable tracking of the reference current at steady state and fast transient response. It is also capable of maintaining the capacitor voltage at its pre-selected and desired level. Parameters sensitivity analysis was carried out and showed that the parameters variation does not have a significant effect on the controller performance. The obtained experimental results confirmed the simulation results and demonstrated that the proposed MPC is effective in controlling the grid current with high steady-state and dynamic tracking performances while keeping balanced capacitor voltage.

REFERENCES:

[1] H. Abu-Rub, M. Malinowski, K. Al-Haddad, “Power Electronics for Renewable Energy Systems, Transportation and Industrial Applications”, John Wiley & Sons, 2014.

[2] E. Babaei, S. Alilu and S. Laali, “A New General Topology for Cascaded Multilevel Inverters With Reduced Number of Components Based on Developed H-Bridge,” in IEEE Trans. Ind. Electron., vol. 61, no. 8, pp. 3932-3939, Aug. 2014.

[3] J. Rodríguez, J.S. Lai, F.Z. Peng, “Multilevel Inverters: A Survey of Topologies, Controls, and Applications”, IEEE Trans. Ind. Electron., vol. 49, no. 4, August 2002.

[4] H. Abu-Rub, J. Holtz, J. Rodriguez and G. Baoming, “Medium-Voltage Multilevel Converters—State of the Art, Challenges, and Requirements in Industrial Applications,” IEEE Trans. Ind. Electron., vol.57, no.8, pp.2581-2596, 2010.

[5] J. Chavarria, D. Biel, F. Guinjoan, C. Meza and J. J. Negroni, “Energy-Balance Control of PV Cascaded Multilevel Grid-Connected Inverters Under Level-Shifted and Phase-Shifted PWMs,” IEEE Trans. Ind. Electron., vol.60, no.1, pp.98-111, Jan. 2013.