An Adaptive Proportional Resonant Controller forSingle Phase PV Grid Connected Inverter Based onBand-Pass Filter Technique

ABSTRACT:  

This paper presents an adaptive proportional resonant (PR) controller for single phase grid connected inverter that adapts its control parameters to grid impedance variations. Forth order band bass filter is designed and then integrated with the adaptive scheme for on-line detection of any variations in the resonance frequency. The estimated frequency is then processed by statistical signal processing operation to identify the variations in the grid impedance. For the on–line tuning of the PR parameters, a look-up table technique is utilized and its parameters are linked with the estimated impedance values. Simulation results based on MATLAB environment clearly verify the effectiveness of the proposed control scheme for 2 kW grid connected inverter system.

KEYWORDS:

1.      Adaptive Proportional Resonant Controller

2.      Grid Impedance Estimation

3.      LCL Filter

4.      Look-up Table

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Block diagram of the proposed adaptive PR controller.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation result of emulated grid voltage.

Fig.3. FFT analysis of grid current. (a) APR controller. (b).PR controller.

Fig. 4. Online adaptation of the APR control parameters.

Fig. 5. Grid voltage and current waveforms under changeable grid

impedance with the proposed control strategy.

CONCLUSION:

A new control strategy based on an adaptive proportional resonant (APR) controller has been developed and successfully tested on a simulated 2 kW single phase grid tide PV inverter. A fourth order Sallen-Key bandpass filter tailored to the system to capture the harmonic components around the resonant frequency has been implemented. Statistic signal processing technique was employed in order to provide the controller with signals corresponded to the changeable grid impedance. A considerable low level of current total harmonic distortion (THD) is achieved in comparison with conventional PR controller and compliance with IEEE929-Standard has been demonstrated.

REFERENCES:

[1] S. Kouro, J. I. Leon, D. Vinnikov, and L. G. Franquelo, "Grid-Connected Photovoltaic Systems: An Overview of Recent Research and Emerging PV Converter Technology," IEEE Industrial Electronics Magazine, vol. 9, pp. 47-61, 2015.

[2] "IEEE Recommended Practice for Utility Interface of Photovoltaic (PV) Systems," in IEEE Std 929-2000, ed, 2000.

[3] "IEEE Draft Application Guide for IEEE Standard 1547, Interconnecting Distributed Resources With Electric Power Systems," in IEEE Unapproved Draft Std P1547.2/D11, Sept 2008, ed, 2008, p. 1.

[4] H. M. El-Deeb, A. Elserougi, A. S. Abdel-Khalik, S. Ahmed, and A. M. Massoud, "An adaptive PR controller for inverter-based distribution generation with active damped LCL filter," in 2013 7th IEEE GCC Conference and Exhibition (GCC), 2013, pp. 462-467.

[5] W. L. Chen and J. S. Lin, "One-Dimensional Optimization for Proportional-Resonant Controller Design Against the Change in Source Impedance and Solar Irradiation in PV Systems," IEEE Transactions on Industrial Electronics, vol. 61, pp. 1845-1854, 2014.

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.