Standalone Operation of Modified Seven-LevelPacked U-Cell (MPUC) Single-Phase Inverter

ABSTRACT:  

In this paper the standalone operation of the modified seven-level Packed U-Cell (MPUC) inverter is presented and analyzed. The MPUC inverter has two DC sources and six switches, which generate seven voltage levels at the output. Compared to cascaded H-bridge and neutral point clamp multilevel inverters, the MPUC inverter generates a higher number of voltage levels using fewer components. The experimental results of the MPUC prototype validate the appropriate operation of the multilevel inverter dealing with various load types including motor, linear, and nonlinear ones. The design considerations, including output AC voltage RMS value, switching frequency, and switch voltage rating, as well as the harmonic analysis of the output voltage waveform, are taken into account to prove the advantages of the introduced multilevel inverter.

KEYWORDS:

1.      Multilevel inverter

2.      Packed u-cell

3.      Power quality

4.      Multicarrier PWM

5.      Renewable energy conversion

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Figure 1. Single-phase seven-level MPUC inverter in standalone mode of operation

EXPECTED SIMULATION RESULTS:

Figure 2. Seven-level MPUC inverter output voltage and current with DC source voltages. Ch₁: V₁,

Ch₂: V₂, Ch₃: V_ab, Ch₄: i_l.

Figure 3. One cycle of output voltage and gate pulses of MPUC inverter switches. Ch₁: V_ab, Ch₂: T₁

gate pulses, Ch₃: T₂ gate pulses, Ch₄: T₃ gate pulses

Figure 4. MPUC inverter switches’ voltage ratings. Ch₁: V_ab, Ch₂: T₁ voltage, Ch₃: T₂ voltage, Ch₄:

T₃ voltage. and nonlinear). The step-by-step process for connecting loads is depicted in Figure 7, which show

Fig.5. Test results when a nonlinear load is connected to the MPUC inverter.Ch₁  :V_ab  :Ch₄ :i_l.

Figure 6. Output voltage and current waveform of MPUC inverter when different loads are added

step by step. Ch₁: V_ab, Ch₄: i_l. (A) Transient state when nonlinear load is added to the RL load (left)

and after a while a motor load is added to the system (right); (B) steady state when a nonlinear load is

added to the RL load (left) and after a while a motor load is added to the system (right).

Figure 7. Voltage and current waveform of MPUC inverter with RMS calculation for 120 V system.

CONCLUSION:

In this paper a reconfigured PUC inverter topology has been presented and studied experimentally. The proposed MPUC inverter can generate a seven-level voltage waveform at the output with low harmonic contents. The associated switching algorithm has been designed and implemented on the introduced MPUC topology with reduced switching frequency aspect. Switches’ frequencies and ratings have been investigated experimentally to validate the good dynamic performance of the proposed topology. Moreover, the comparison of MPUC to the CHB multilevel inverter showed other advantages of the proposed multilevel inverter topology, including fewer components, a lower manufacturing price, and a smaller package due to reduced filter size.

Author Contributions: All authors contributed equally to the work presented in this paper.

Funding: This research received no external funding.

Conflicts of Interest: The authors declare no conflict of interest.

REFERENCES:

1. Bose, B.K. Multi-Level Converters; Multidisciplinary Digital Publishing Institute: Basel, Switzerland, 2015.

2. Mobarrez, M.; Bhattacharya, S.; Fregosi, D. Implementation of distributed power balancing strategy with a layer of supervision in a low-voltage DC microgrid. In Proceedings of the 2017 IEEE Applied Power Electronics Conference and Exposition (APEC), Tampa, FL, USA, 26–30 March 2017; pp. 1248–1254.

3. Franquelo, L.G.; Rodriguez, J.; Leon, J.I.; Kouro, S.; Portillo, R.; Prats, M.A.M. The age of multilevel converters arrives. IEEE Ind. Electron. Mag. 2008, 2, 28–39. [CrossRef]

4. Malinowski, M.; Gopakumar, K.; Rodriguez, J.; Perez, M.A. A survey on cascaded multilevel inverters. IEEE Trans. Ind. Electron. 2010, 57, 2197–2206. [CrossRef]

5. Nabae, A.; Takahashi, I.; Akagi, H. A new neutral-point-clamped PWM inverter. IEEE Trans. Ind. Appl. 1981,5, 518–523. [CrossRef]

Single Stage PV Array Fed Speed Sensorless Vector Control of Induction Motor Drive for Water Pumping

 ABSTRACT:  

 This paper deals with a single stage solar powered speed sensorless vector controlled induction motor drive for water pumping system, which is superior to conventional motor drive. The speed is estimated through estimated stator flux. The proposed system includes solar photovoltaic (PV) array, a three-phase voltage source inverter (VSI) and a motor-pump assembly. An incremental conductance (InC) based MPPT (Maximum Power Point Tracking) algorithm is used to harness maximum power from a PV array. The smooth starting of the motor is attained by vector control of an induction motor. The desired configuration is designed and simulated in MATLAB/Simulink platform and the design, modeling and control of the system, are validated on an experimental prototype developed in the laboratory.

KEYWORDS:

1.      Speed Sensorless Control

2.      Stator Field-Oriented Vector Control

3.      Photovoltaic (PV)

4.      InC MPPT Algorithm

5.      Induction Motor Drive (IMD)

6.      Water Pump

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. PV fed induction motor drive configuration

 EXPECTED SIMULATION RESULTS:

Fig. 2. Starting and MPPT of PV array at 1000 W/m²

Fig. 3. Intermediate signals during starting at 1000 W/m²

(a)

(b)

Fig. 4. Simulation results during starting at 1000 W/m² (a) Proposed drive (b) Waveforms showing sensed speed and estimated speed

Fig. 5. SPV array performance during decrease in insolation from 1000 W/m² to 500 W/m²

(a)

 (b)

Fig. 6. Dynamic performance during irradiance decrement from 1000 W/m² to 500 W/m² (a) Proposed drive (b) Waveforms showing sensed speed and estimated speed

Fig. 7. PV array performance on increasing insolation from 500 W/m² to 1000 W/m²

(a)

(b)

Fig. 8. Dynamic performance during irradiance decrement from 500 W/m² to 1000 W/m² (a) Proposed drive (b) Waveforms showing sensed speed and estimated speed

CONCLUSION:

A single stage solar PV array fed speed sensorless vector-controlled induction motor drive has been operated subjected to different conditions and the steady state and dynamic behaviors have been found quite satisfactory and suitable for water pumping. The torque and stator flux, have been controlled independently. The motor is started smoothly. The reference speed is generated by DC link voltage controller controlling the voltage at DC link along with the speed estimated by the feed-forward term incorporating the pump affinity law. The power of PV array is maintained at maximum power point at the time of change in irradiance. This is achieved by using incremental-conductance based MPPT algorithm. The speed PI controller has been used to control the q-axis current of the motor. Smooth operation of IMD is achieved with desired torque profile for wide range of speed control. Simulation results have displayed that the controller behavior is found satisfactory under steady state and dynamic conditions of insolation change. The suitability of the drive is also verified by experimental results under various conditions and has been found quite apt for water pumping.

REFERENCES:

[1] R. Foster, M. Ghassemi and M. Cota, Solar energy: Renewable energy and the environment, CRC Press, Taylor and francis Group, Inc. 2010.

[2] M. Kolhe, J. C. Joshi and D. P. Kothari, “Performance analysis of a directly coupled photovoltaic water-pumping system”, IEEE Trans. on Energy Convers., vol. 19, no. 3, pp. 613-618, Sept. 2004.

[3] J. V. M. Caracas, G. D. C. Farias, L. F. M. Teixeira and L. A. D. S. Ribeiro, “Implementation of a high-efficiency, high-lifetime, and low-cost converter for an autonomous photovoltaic water pumping system”, IEEE Trans. Ind. Appl., vol. 50, no. 1, pp. 631-641, Jan.-Feb. 2014.

[4] R. Kumar and B. Singh, “ Buck-boost converter fed BLDC motor for solar PV array based water pumping, ” IEEE Int. Conf. Power Electron. Drives and Energy Sys. (PEDES), 2014.

[5] Zhang Songbai, Zheng Xu, Youchun Li and Yixin Ni, “Optimization of MPPT step size in stand-alone solar pumping systems,” IEEE Power Eng. Society Gen. Meeting, June 2006.

A Novel Design of Hybrid Energy Storage System for Electric Vehicles

ABSTRACT:  

In order to provide long distance endurance and ensure the minimization of a cost function for electric vehicles, a new hybrid energy storage system for electric vehicle is designed in this paper. For the hybrid energy storage system, the paper proposes an optimal control algorithm designed using a Li-ion battery power dynamic limitation rule-based control based on the SOC of the super-capacitor. At the same time, the magnetic integration technology adding a second-order Bessel low-pass filter is introduced to DC-DC converters of electric vehicles. As a result, the size of battery is reduced, and the power quality of the hybrid energy storage system is optimized. Finally, the effectiveness of the proposed method is validated by simulation and experiment.

KEYWORDS:

1.      Hybrid energy storage system

2.      Integrated magnetic structure

3.      Electric vehicles

4.      DC-DC converter

5.      Power dynamic limitation

SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

Fig.1 Topology of the hybrid energy storage system

EXPECTED SIMULATION RESULTS:

(a) Power command and actual power

(b) Power of the super-capacitor and Li-ion battery

Fig.2 Simulation results of the proposed HESS

(a)     Battery current

(b)     Super-capacitor current

(c)     Load current

(d)     Load voltage

Fig.3 Simulation results of the proposed HESS applied on electric vehicles

CONCLUSION:

In this paper, a new hybrid energy storage system for electric vehicles is designed based on a Li-ion battery power dynamic limitation rule-based HESS energy management and a new bi-directional DC/DC converter. The system is compared to traditional hybrid energy storage system, showing it has significant advantage of reduced volume and weight. Moreover, the ripple of output current is reduced and the life of battery is improved.

REFERENCES:

[1] Zhikang Shuai, Chao Shen, Xin Yin, Xuan Liu, John Shen, “Fault analysis of inverter-interfaced distributed generators with different control schemes,” IEEE Transactions on Power Delivery, DOI: 10. 1109/TPWRD. 2017. 2717388.

[2] Zhikang Shuai, Yingyun Sun, Z. John Shen, Wei Tian, Chunming Tu, Yan Li, Xin Yin, “Microgrid stability: classification and a  review,” Renewable and Sustainable Energy Reviews, vol.58, pp. 167-179, Feb. 2016.

[3] N. R. Tummuru, M. K. Mishra, and S. Srinivas, “Dynamic energy management of renewable grid integrated hybrid  energy storage system, ” IEEE Trans. Ind. Electron., vol. 62, no. 12, pp. 7728-7737, Dec. 2015.

[4] T. Mesbahi, N. Rizoug, F. Khenfri, P. Bartholomeus, and P. Le Moigne, “Dynamical modelling and emulation of Li-ion batteries- supercapacitors hybrid power supply for electric vehicle applications, ” IET Electr. Syst. Transp., vol.7, no.2, pp. 161-169, Nov. 2016.

[5] A. Santucci, A. Sorniotti, and C. Lekakou, “Power split strategies for hybrid energy storage systems for vehicular applications, ” J. Power Sources, vol. 258, no.14, pp. 395-407,  2014.

New Three-Phase Symmetrical MultilevelVoltage Source Inverter

ABSTRACT:  

This paper presents a new design and implementation of a three-phase multilevel inverter (MLI) for distributed power generation system using low frequency modulation and sinusoidal pulse width modulation (SPWM) as well. It is a modular type and it can be extended for extra number of output voltage levels by adding additional modular stages. The impact of the proposed topology is its proficiency to maximize the number of voltage levels using a reduced number of isolated dc voltage sources and electronic switches. Moreover, this paper proposes a significant factor (F_C/L), which is developed to define the number of the required components per pole voltage level. A detailed comparison based on (F_C/L) is provided in order to categorize the different topologies of the MLIs addressed in the literature. In addition, a prototype has been developed and tested for various modulation indexes to verify the control technique and performance of the topology. Experimental results show a well-matching and good similarity with the simulation results.

KEYWORDS:

1.      Low frequency modulation

2.      Multi-level inverter

3.      Multi-level inverter comparison factor

4.      Sinusoidal pulse-width modulation (SPWM)

5.      Symmetrical DC power sources

6.      Three-phase

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Proposed three-phase MLI topology.

EXPECTED SIMULATION RESULTS:

Fig. 2. Output line-to-line voltages ( V_AB,V_BC , and V_CA ) with low frequency (50 Hz) modulation technique. (a) Simulation.

Fig. 3. Output phase voltages ( V_AN,V_BN , and V_CN ) with low frequency modulation technique. (a) Simulation.

Fig. 4. Inverter outputs with R-L load (V_AB ,V_AN , and I_AN) with low frequency modulation technique. (a) Simulation.

Fig. 5. Pole voltages for scheme I, m_i =0.95 and f_s=2.5kHz. (a) Simulation.

Fig. 6. Line-to-line voltages for scheme I, m_i =0.95 and f_s=2.5kHz . (a) Simulation.

Fig. 7. Phase voltages for scheme I, m_i =0.95 and f_s=2.5kHz . (a) Simulation.

Fig. 8. Pole voltages for scheme II, m_i =0.95 and f_s=2.5kHz . (a) Simulation.

Fig. 9. Line-to-line voltages for scheme II, m_i =0.95 and f_s=2.5kHz  . (a) Simulation.

Fig. 10. Phase voltages for scheme II, m_i =0.95 and f_s=2.5kHz. (a) Simulation.

Fig. 11. Line-to-line voltage and phase voltage at for scheme I, m_i =0.95 and f_s=2.5kHz . (a) Simulation.

Fig. 12. Line-to-line voltage and phase voltage for scheme II, m_i =0.95 and f_s=2.5kHz . (a) Simulation.

Fig. 13. Inverter output voltages: (a) three phase line-to-line voltages ( V_AB, V_BC, and V_CA ), (b) line-to-line voltage, phase voltage and the phase current under R-L load.

CONCLUSION:

A new modular multilevel inverter topology using two modulation control techniques is presented. The proposed has several advantages compared with existing topologies. A lower number of components count such as isolated dc-power supplies, switching devices, electrolyte capacitors, and power diodes are required. So it exhibits the merits of high efficiency, lower cost, simplified control algorithm, smaller inverter's foot print and increased the overall system reliability. Due to the modularity of the presented topology, it can be extended to higher stages number leads to a good performance issues such as low, low, and low and eliminating the output filter will be obtained. Beside the low frequency modulation, two schemes are successfully applied to control the suggested . This paper also suggests a significant factor, which defines the required components to generate one voltage level across the output pole terminals. The issue related to the cost of each used component is out of scope of this paper. The system simulation model and its control algorithm are developed using PSIM and MATLAB software package tools to validate the proposed topology. A laboratory prototype has been developed and tested for various modulation indexes to verify the control techniques and performance of the topology, the similarity between the simulation and obtained experimental results was confirmed.

REFERENCES:

[1] S. J. Park, F. S. Kang, M. H. Lee, and C. U. Kim, “A new single-phase five-level PWM inverter employing a deadbeat control scheme,” IEEE Trans. Power Electron., vol. 18, no. 3, pp. 831–843, May 2003.

[2] V. G. Agelidis, D. M. Baker, W. B. Lawrance, and C. V. Nayar, “A multilevel PWM inverter topology for photovoltaic applications,” in Proc. Int. Symp. Ind. Electron., Jul. 1997, vol. 2, pp. 589–594.

[3] G. J. Su, “Multilevel DC-link inverter,” IEEE Trans. Ind. Appl., vol. 41, no. 3, pp. 848–854, May–Jun. 2005.

[4] M. Calais, L. J. Borle, and V. G. Agelidis, “Analysis of multicarrier PWM methods for a single-phase five level inverter,” in Proc. Power Electron. Specialists Conf., 2001, vol. 3, pp. 1351–1356.

[5] C. T. Pan, C. M. Lai, and Y. L. Juan, “Output current ripple-free PWM inverters,” IEEE Trans. Circuits Syst. II, Exp. Briefs., vol. 57, no. 10, pp. 823–827, Oct. 2010.