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


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.


  1. Adaptive Proportional Resonant Controller
  2. Grid Impedance Estimation
  3. LCL Filter
  4. Look-up Table



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


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.


 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.


[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-Level Packed U-Cell (MPUC) Single-Phase Inverter

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.

1. Multilevel inverter
2. Packed u-cell
3. Power quality
4. Multicarrier PWM
5. Renewable energy conversion


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


Figure 2. Seven-level MPUC inverter output voltage and current with DC source voltages. Ch1: V1,
Ch2: V2, Ch3: Vab, Ch4: il.

Figure 3. One cycle of output voltage and gate pulses of MPUC inverter switches. Ch1: Vab, Ch2: T1
gate pulses, Ch3: T2 gate pulses, Ch4: T3 gate pulses

Figure 4. MPUC inverter switches’ voltage ratings. Ch1: Vab, 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 :Vab :Ch4 :il.

Figure 6. Output voltage and current waveform of MPUC inverter when different loads are added
step by step. Ch1: Vab, Ch4: il. (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.


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.

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


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.


  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



Fig. 1. PV fed induction motor drive configuration


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

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




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



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



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


 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.


[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 Systemfor Electric Vehicles


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.


  1. Hybrid energy storage system
  2. Integrated magnetic structure
  3. Electric vehicles
  4. DC-DC converter
  5. Power dynamic limitation



Fig.1 Topology of the hybrid energy storage system


(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



 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.


[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


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 (FC/L), which is developed to define the number of the required components per pole voltage level. A detailed comparison based on (FC/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.


  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



Fig. 1. Proposed three-phase MLI topology.


Fig. 2. Output line-to-line voltages ( VAB,VBC , and VCA ) with low frequency (50 Hz) modulation technique. (a) Simulation.

Fig. 3. Output phase voltages ( VAN,VBN , and VCN ) with low frequency modulation technique. (a) Simulation.

Fig. 4. Inverter outputs with R-L load (VAB ,VAN , and IAN) with low frequency modulation technique. (a) Simulation.

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

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

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

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

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

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

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

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

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


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.


[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.

An Efficient Constant Current Controller for PV SolarPower Generator Integrated with the Grid


This paper presents the detailed design and modeling of grid integrated with the Photovoltaic Solar Power Generator. As the Photovoltaic System uses the solar energy as one of the renewable energies for the electrical energy production has an enormous potential. The PV system is developing very rapidly as compared to its counterparts of the renewable energies. The DC voltage generated by the PV system is boosted by the DC-DC Boost converter. The utility grid is incorporated with the PV Solar Power Generator through the 3-ı PWM DC-AC inverter, whose control is provided by a constant current controller. This controller uses a 3-ı phase locked loop (PLL) for tracking the phase angle of the utility grid and reacts fast enough to the changes in load or grid connection states, as a result, it seems to be efficient in supplying to load the constant voltage without phase jump. The complete mathematical model for the grid connected PV system is developed and simulated. The results verify that the proposed system is proficient to supply the local loads.


  1. PV Solar Power Generator
  2. DC-DC Boost Converter
  3. PWM inverter
  4. PLL
  5. Constant Current Controller (CCC)



Fig.1 Switching Model of Solar Inverter


Fig.2 P-V Curve of the Solar Array

Fig. 3 V-I Curve of the Solar Array

Fig. 4 DC voltage delivered by the Boost converter

Fig. 5Inverter output voltage before filtering

Fig. 6 Inverter output voltage after filtering

Fig. 7 Load current for supplying the 2 MW load.

Fig.8 Load current for supplying the load of about 30 MW, 2 MVAr


For improving the energy efficiency and power quality issues with the increment of the world energy demand, the power generation using the renewable energy source is the only solution. There are several countries located in the tropical and temperature regions, where the direct solar density may reach up to 1000W/m2. Hence PV system is considered as a primary resource. In this paper, the detailed modeling of grid connected PV generation system is developed. The DC-DC boost converter is used to optimize the PV array output with the closed loop control for keeping the DC bus voltage to be constant. The 2 level 3-phase inverter is converting the DC into the sinusoidal AC voltage. The control of the solar inverter is provided through the constant current controller. This controller tracks the phase and frequency of the utility grid voltage using the Phase- Locked-Loop (PLL) system and generates the switching pulses for the solar inverter. Using this controller the output voltage of the solar inverter and the grid voltage are in phase. Thus the PV system can be integrated to the grid. The simulation results the presented in this paper to validate the grid connected PV system model and the applied control scheme.


[1] A. M. Hava, T. A. Lipo and W. L. Erdman. “Utility interface issues for line connected PWM voltage source converters: a comparative study”, Proceeding of APEC’95, Dallas (USA), pp. 125-132, March 1995.

[2] L. J. BORLE, M. S. DYMOND and C. V. NAYAR, “Development and testing of a 20 kW grid interactive photovoltaic power conditioning system in Western Australia”, IEEE Transaction, Vol. 33, No. 2, pp. 502-508, 1997.

[3] M. Calais, J. Myrzik, T. Spooner, V. Agelidis, “Inverters for single- phase grid connected photovoltaic systems – an overview”, IEEE 33rd Annual Power Electronics Specialists Conference, Volume 4, 23-27 June 2002

[4] S. K. Chung, “Phase-Locked Loop for Grid connected Three-phase Power Conversion Systems”, IEE Proceeding on Electronic Power Application, Vol. 147, No. 3, pp. 213-219, 2000.

[5] S. Rahman, “Going green: the growth of renewable energy”, IEEE Power and Energy Magazine, 16-18 Nov./Dec. 2003.

A 5-level High Efficiency Low Cost HybridNeutral Point Clamped Transformerless Inverterfor Grid Connected Photovoltaic Application


With the increase in the level of solar energy integration into the power grid, there arises a need for highly efficient multilevel transformerless grid connected inverter which is able to inject more power into the grid. In this paper, a novel 5-level Hybrid Neutral Point Clamped transformerless  inverter topology is proposed which has no inherent ground leakage current. The proposed inverter is analyzed in detail and its switching pattern to generate multilevel output is discussed. The proposed inverter is compared with some popular transformerless inverter topologies. Simulations and experiments results confirm the feasibility and good performance of the proposed inverter.



Fig. 1. Proposed hybrid neutral point clamped inverter


Fig. 2. Inverter operation at UPF

Fig. 3. Inverter operation at 300 lag PF

Fig. 4. Inverter output for increase of modulation index from 0.45 to 0.95

Fig. 5. Inverter output for decrease of modulation index from 0.95 to 0.45

Fig. 6. Dynamic performance of inverter for increase of load

Fig. 7. Dynamic performance of inverter for decrease of load

Fig. 8. Inverter operation with chopper balancing circuit activated

Fig. 9. Inverter operation with chopper balancing circuit deactivated


 A 5-level Hybrid neutral point clamped transformerless PV grid connected inverter is presented in this paper. The main characteristics of proposed transformerless inverter are:

1) Lower stress on the grid interfacing inductor, thereby reducing the filtering cost and size as compared to conventional 3-level inverters like H5 and HERIC  inverter.

2) Lower cost as compared to 5L-DCMLI as the proposed inverter requires less no of clamping diodes.

3) Higher power handling capability as compared to conventional 3-level inverters.

4) Higher efficiency as compared to 5L-DCMLI and H5 inverter.

5) No common mode leakage current as the proposed inverter belongs to the family of half bridge inverters.

6) The proposed inverter is capable of exchanging reactive power with the grid.

Therefore, with excellent performance in eliminating the CM current, multilevel output voltage and high efficiency, the proposed inverter provides an exciting alternative to the conventional transformerless grid-connected PV inverters. Moreover, due to its superiority over the 5L-DCMLI in terms of efficiency and cost parameters, the pertinence of the proposed inverter is not limited to grid connected PV inverters and it can find its way for all the applications where currently 5L-DCMLI are employed.


[1] M. Calais and V. G. Agelidis,“Multilevel converters for single-phase grid connected photovoltaic systems-an overview,” Industrial Electronics, 1998. Proceedings. ISIE ’98. IEEE International Symposium on, Pretoria, 1998, pp. 224-229 vol.1. doi: 10.1109/ISIE.1998.707781 [2] R. Teodorescu, M. Liserre et al., “Grid converters for photovoltaic and wind power systems”. John Wiley & Sons, 2011, vol. 29.

[3] E. Gubia, P. Sanchis, A. Ursua, J. Lopez, and L. Marroyo, “Ground currents in single phase transformerless photovoltaic systems”, Progress in Photovoltaics: Research and Applications, vol. 15, no. 7, pp. 629650, 2007.

[4] H. Xiao and S. Xie, “Leakage current analytical model and application in single-phase transformerless photovoltaic grid-connected inverter”, IEEE Transactions on Electromagnetic Compatibility, vol. 52, DOI 10.1109/TEMC.2010.2064169, no. 4, pp. 902913, Nov. 2010.

[5] S. Busquets-Monge, J. Rocabert, P. Rodriguez, S. Alepuz and J. Bordonau, “Multilevel Diode-Clamped Converter for Photovoltaic Generators With Independent Voltage Control of Each Solar Array”, in IEEE Transactions on Industrial Electronics, vol. 55, no. 7, pp. 2713-2723, July 2008. Doi: 10.1109/TIE.2008.924011

Single Phase NPC Inverter Controller with IntegratedMPPT for PV Grid Connection


This paper presents a single-stage three-level Neutral Point Clamped (NPC) inverter for connection to the electrical power grid, with integrated Maximum Power Point Tracking (MPPT) algorithm to extract the maximum power available from solar photovoltaic (PV) panels. This single-stage topology is more compact than the traditional topology, it was chosen because with the proper control strategy. It is suitable to connect the PV panels to the power grid. The paper describes the design of a 5 kW NPC inverter for the interface of PV panels with the power grid, presenting the circuit parameters and the description of the control algorithms. A phase locked loop control is used to connect the inverter into the grid. Then, a proposed DC Link voltage control to regulate the input voltage of the inverter. Although an MPPT algorithm was used to optimize the energy extraction and the system efficiency. Inverter Output Current control to produce an output current (current injected in the power grid) with low Total Harmonic Distortion (THD) implemented in a DSP. Simulation and experimental results verify the correct operation of the proposed system, even with fluctuations in the solar radiation.


  1. Photovoltaic System
  2. Maximum Power Point Tracking (MPPT)
  3. Neutral Point Clamped (NPC) Inverter
  4. Phase-Locked Loop (PLL)



Figure 1. Block diagram of the NPC converter control system.


Figure 2. Block diagram of the E-PLL.


Figure 3. Startup of the proposed system with maximum solar radiation: (a)

PV current (ipanels); (b) PV panels voltage (vpanels);

(c) PV panels power (ppanels).

Figure 4. Operation with fluctuations in the solar radiation, from1000 W/m² to

800 W/m² and to 600 W/m: (a) Maximum theoretical power (pmax); (b)

Extracted power PV panels (ppanels); (c) Inverter output current (iout).

Figure 5. Reference current (iref *) and current injected into the power grid (iout).

Figure 6. Power grid voltage (vgrid) and inverter output current (iout).

Figure 7. Voltages in the two capacitors of the DC-link (vc1, vc2).


This paper presents the design, simulation and experimental results of a 5 kW single-stage three-level Neutral Point Clamped (NPC) inverter for connection to the electrical power grid, with integrated Maximum Power Point Tracking (MPPT) algorithm to extract the maximum available power from solar photovoltaic (PV) panels. It also describes the design of the PLL controller, used to track the fundamental power grid voltage in order to synchronize the NPC inverter with the power grid, and to generate a reference for the inverter output current (which consists in the injected power grid current). All the controllers have been implemented using C code, validated by simulation in PSIM, and executed in a DSP. Experimental results indicate that the current injected in the power grid follows the reference, and that the voltages in the two DC-link capacitors are kept balanced. It is shown that the proposed system is able to always extract the maximum power available from the solar PV panels, even when there are solar radiation fluctuations.


[1] S. V. Araújo, S. Member, P. Zacharias, and R. Mallwitz, “Highly Efficient Single-Phase Transformerless Inverters for Grid-Connected Photovoltaic Systems,” Ind. Electron. IEEE Trans., vol. 57, no. 9, pp. 3118–3128, 2010.

[2] S. Saridakis, E. Koutroulis, and F. Blaabjerg, “Optimal  Design of Modern Transformerless PV Inverter Topologies,” Energy Conversion, IEEE Trans., vol. 28, no. 2, pp. 394–404, 2013.

[3] R.Teodorescu, M.Liserre, and P.Rodriguez, Grid Converters for Photovoltaic and Wind Power Systems. 2011.

[4] S. Busquets-monge, J. Rocabert, P. Rodríguez, P. Alepuz, and J. Bordonau, “Multilevel Diode-Clamped Converter for Photovoltaic Generators With Independent Voltage Control of Each Solar Array,” Ind. Electron. IEEE Trans., vol. 55, no. 7, pp. 2713–2723, 2008.

[5] P. Panagis, F. Stergiopoulos, P. Marabeas, and S. Manias, “Comparison of State of the Art Multilevel Inverters,” Power Electron. Spec. Conf. 2008. PESC 2008. IEEE, pp. 4296– 4301, 2008.


A Unified Control and Power Management Schemefor PV-Battery-Based Hybrid Microgrids for BothGrid-Connected and Islanded Modes


Battery storage is usually employed in Photovoltaic (PV) system to mitigate the power fluctuations due to the characteristics of PV panels and solar irradiance. Control schemes for PV-battery systems must be able to stabilize the bus voltages as well as to control the power flows flexibly. This paper proposes a comprehensive control and power management system (CAPMS) for PV-battery-based hybrid microgrids with both AC and DC buses, for both grid-connected and islanded modes. The proposed CAPMS is successful in regulating the DC and AC bus voltages and frequency stably, controlling the voltage and power of each unit flexibly, and balancing the power flows in the systems automatically under different operating circumstances, regardless of disturbances from switching operating modes, fluctuations of irradiance and temperature, and change of loads. Both simulation and experimental case studies are carried out to verify the performance of the proposed method.


  1. Solar PV System
  2. Battery
  3. Control and Power Management System
  4. Distributed Energy Resource
  5. Microgrid
  6. Power Electronics
  7. dSPACE



Fig. 1. The proposed control and power management system (CAPMS) for PV-battery-based hybrid microgrids.


Fig.. 2.. (Gb)rid-connected mode Case A-1: (a) power flows and (b) voltage

values of the PV-battery system.

Fig. 3. Grid-connected mode Case A-2: power flows of the PV-battery system.

Fig. 4. Grid-connected mode Case A-3-1: PV array in power-reference mode.

Fig. 5. Grid-connected mode Case A-3-2: DC bus and PV array voltages

during transitions between MPPT and power-reference modes.

Fig. 6. Grid-connected mode Case A-4: the PV-battery system is receiving

power from the grid after 2.2 s.

Fig. 7. Grid-connected mode Case A-5: Reactive power control of the


Fig. 8. Grid-connected mode Case A-6: transition from grid-connected to

islanded mode.

Fig. 9. Islanded mode Case B-1: power flows of the PV-battery system with

changing loads.

Fig. 10. Islanded mode Case B-2: battery power changes with PV generation.

Fig. 11. Islanded mode Case B-3: bus voltage control of the PV-battery


Fig. 12. Islanded mode Case B-4: (a) unsynchronized and (b) synchronized

AC bus voltages (displaying phase-a) when closing the breaker at the PCC.


 This paper proposes a control and power management system (CAPMS) for hybrid PV-battery systems with both DC and AC buses and loads, in both grid-connected and islanded modes. The presented CAPMS is able to manage the power flows in the converters of all units flexibly and effectively, and ultimately to realize the power balance between the hybrid microgrid system and the grid. Furthermore, CAPMS ensures a reliable power supply to the system when PV power fluctuates due to unstable irradiance or when the PV array is shut down due to faults. DC and AC buses are under full control by the CAPMS in both grid-connected and islanded modes, providing a stable voltage environment for electrical loads even during transitions between these two modes. This also allows additional loads to access the system without extra converters, reducing operation and control costs. Numerous simulation and experimental case studies are carried out in Section IV that verifies the satisfactory performance of the proposed CAPMS.


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Energy Management and Control System for Laboratory Scale Microgrid based Wind-PV-Battery


This paper proposes an energy management and control system for laboratory scale microgrid based on hybrid energy resources such as wind, solar and battery. Power converters and control algorithms have been used along with dedicated energy resources for the efficient operation of the microgrid. The control algorithms are developed to provide power compatibility and energy management between different resources in the microgrid. It provides stable operation of the control in all microgrid subsystems under various power generation and load conditions. The proposed microgrid, based on hybrid energy resources, operates in autonomous mode and has an open architecture platform for testing multiple different control configurations. Real-time control system has been used to operate and validate the hybrid resources in the microgrid experimentally. The proposed laboratory scale microgrid can be used as a benchmark for future research in smart grid applications.


  1. Wind energy
  2. Solar energy
  3. Conversion
  4. Storage
  5. Hybrid system
  6. Control
  7. Energy management



 Fig. 1. Components of the laboratory scale experimental microgrid


Fig. 2. Wind turbine-generator speed

Fig. 3. PV module current


Fig. 4. DC-link voltage

Fig. 5. Battery current

Fig. 6. Power at different locations in the microgrid (variable wind power)

Fig. 7. Battery state of charge

Fig. 8. Load Voltage

Fig. 9. Power at different locations in the microgrid (variable wind power)

Fig. 10. Battery current

Fig. 11. Battery state of charge

Fig. 12. DC-bus voltage

Fig. 13. Load Voltage


 A laboratory scale experimental microgrid of distributed renewable energy sources with battery storage and energy management and control system is developed in this paper. The experimental setup is flexible and allows testing difference power electronics interfaces and combinations. The control software is open source in order to implement different control strategies. This tool contributes to the enhancement of education and research the field of renewable energy and distributed energy systems.


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