A Multi-Cell 21-Level Hybrid Multilevel Inverter synthesizes a reduced number of components with Voltage Boosting Property

ABSTRACT:  

 

 A multi-cell hybrid 21-Level multilevel inverter is proposed in this paper. The proposed topology includes two-unit; an H-bridge is cascaded with a modified K-type unit to generate an output voltage waveform with 21 levels based only on two unequal DC suppliers. The proposed topology's advantage lies in the fine and clear output voltage waveforms with high output efficiency. Meanwhile, the high number of output voltage waveform levels generates a low level of distortion and reduces the level of an electromagnetic interface (EMI). Moreover, it reduces the voltage stress on the switching devices and gives it a long lifetime. Also, the reduction in the number of components has a noticeable role in saving size and cost. Regarding the capacitors charging, the proposed topology presents an online method for charging and balancing the capacitor's voltage without any auxiliary circuits. The proposed topology can upgrade to a high number of output steps through the cascading connection. Undoubtedly this cascading will increase the power level to medium and high levels and reduce the harmonics content to a neglectable rate. The proposed system has been tested through the simulation results, and an experimental prototype based on the controller dSPACE (DS-1103) hardware unit used to support the simulation results.

KEYWORDS:

 

1.      21-Level Multilevel Inverter (MLI)

2.      Hybridization

3.      Modified K-type inverter

4.      Online charging

5.      Self-balancing

6.      Voltage boosting inverter

7.      Total Harmonic Distortion (THD)

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

The work in this paper presented a hybrid multilevel inverter that consisted of a series connection between two units (an HB unit with a modified K-Type unit). This combination generates an output voltage waveform with 21 steps. This high number steps in the output voltage help in reducing the level of noises in the output voltage and reduced the stress in the switching devices, which on the one hand generating fine and clear waveforms and on the other hand reduces the harmonic content in the waveforms to a deficient level (satisfying the harmonics standard IEEE519). Economically, the structure of the proposed topology presented an optimal design in terms of reducing the number of switches and DC sources which in turn enhancing the system reliability by reducing the inverter cost. For the capacitors charging process, the paper presents an online method for charging and balancing the capacitor voltages without any auxiliary circuits for that. This helps in the continuous operation of the charging and discharging process for the capacitor without disturbing the process of generating the output voltage. The proposed topology supports the modularity process in order to maximize the range of output power to the medium and high level, and the paper presented two scenarios for the series connection 2HB+K and HB+2K both the cases raise the level of the output power and enhances the system performance to achieve high efficiency. Due to the dependence on multi DC sources, this topology is suitable for renewable energy applications; DC sources are abundant. The hybrid renewable energy sources application will be more appropriate between all the renewable energy applications because the proposed topology-based mainly on two unequal DC suppliers, which will be available easily in the hybrid renewable energy sources.

REFERENCES:

[1] F. Z. Peng, W. Qian, and D. Cao, "Recent advances in multilevel converter/inverter topologies and applications," in The 2010 International Power Electronics Conference-ECCE ASIA-, 2010, pp. 492-501.

[2] J. Rodriguez, J.-S. Lai, and F. Z. Peng, "Multilevel inverters: a survey of topologies, controls, and applications," IEEE Transactions on Industrial Electronics, vol. 49, pp. 724-738, 2002.

[3] L. M. Tolbert and X. Shi, "Multilevel power converters," in Power Electronics Handbook, ed: Elsevier, 2018, pp. 385-416.

[4] K. K. Gupta, A. Ranjan, P. Bhatnagar, L. K. Sahu, and S. Jain, "Multilevel inverter topologies with reduced device count: A review," IEEE transactions on power electronics, vol. 31, pp. 135-151, 2015.

[5] P. Omer, J. Kumar, and B. S. Surjan, "A Review on Reduced Switch Count Multilevel Inverter Topologies," IEEE Access, vol. 8, pp. 22281-22302, 2020.

A Modified Carrier-Based Advanced Modulation Technique For Improved Switching Performance of Magnetic Linked Medium Voltage Converters

ABSTRACT:  

The high-frequency magnetic link is gaining popularity due to its light weight, small volume, and inherent voltage balancing capability. Those features can simplify the utilization of multilevel converter (MLC) for the integration of renewable energy sources to the grid with compact size and exert economic feasibility. The modulation and control of MLC are crucial issues especially for grid connected applications. To support the grid, the converter may need to operate in over-modulation (OVM) region for short periods depending upon the loading conditions. This OVM operation of the converter causes increased harmonic losses and adverse effects on overall system efficiency. On top of that, the size and cost of filtering circuitry become critical to eliminate the unwanted harmonics. In this regard, a modified OVM scheme with phase disposed carriers for grid connected high frequency magnetic link-based cascaded H-bridge (CHB) MLC is proposed for the suppression of harmonics and the reduction of converter loss. Furthermore, with the proposed OVM technique, the voltage gain with modulation index can be increased up to the range which is unlikely to be achieved using the classical ones. Extensive simulations are carried out with a 2.24 MVA permanent magnet synchronous generator-based wind energy conversion system which is connected to the 11 kV ac grid through a high-frequency magnetic link and a 5-level CHB MLC. A scaled down laboratory prototype is implemented to validate the performance of the converter.

KEYWORDS:

1.      Multilevel converter

2.      Over modulation

3.      Grid connection

4.      High-frequency magnetic link

5.      Wind energy

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

To improve the system performance, a modified OVM technique is presented in this paper with grid connected and islanded operation. With the proposed modified carrier signal based BCPWM techniques, the overall loss and THD are decreased for both the islanded and grid connected modes compared with the traditional OVM techniques. Moreover, the voltage gain can be increased and remains approximately constant in the proposed method, which may not be possible to obtain using the traditional OVM methods. In this paper, a high-frequency magnetic link-based fully-rated CHB converter is developed for wind energy applications and the behavior of the system under rated and overrated load conditions are investigated.The use of magnetic link for the generation of isolated and balanced dc sources of the MLC inherently overcomes the voltage imbalance problem of CHB MLC and hence effectively simplifies the system control complexities. The core loss of high-frequency magnetic link is also measured to identify the overall loss of the system. The effectiveness of the proposed technology is confirmed by the simulation and experimental results.

REFERENCES:

 

[1] M. R. Islam, Y. G. Guo, J. G. Zhu, H. Lu, and J. X. Jin, “High-frequency magnetic-link medium-voltage converter for superconducting generator-based high-power density wind generation systems,” IEEE Trans. Appl. Supercond., vol. 24, no. 5, pp. 1–5, Oct. 2014.

[2] N. Mendis, K. M. Muttaqi, S. Perera, and S. Kamalasadan, “An effective power management strategy for a wind–diesel–hydrogen-based remote area power Supply System to meet fluctuating demands under generation uncertainty,” IEEE Trans. Ind. Appl., vol. 51, no. 2, pp. 1228–1238, Mar.–Apr. 2015.

[3] B. Jain, S. Jain, and R. K. Nema, “Control strategies of grid interfaced wind energy conversion system: An overview,” Renew. Sustain. Energy Rev., vol. 47, pp. 983–996, Apr. 2015.

[4] Y. Tan, K. M. Muttaqi, P. Ciufo, and L. Meegahapola, “Enhanced frequency response strategy for a PMSG-based wind energy conversion system using ultracapacitor in remote area power supply systems,” IEEE Trans. Ind. Appl., vol. 53, no. 1, pp. 549–558, Jan.–Feb. 2017.

[5] M. R. Islam, Y. G. Guo, and J. G. Zhu, “A multilevel medium-voltage inverter for step-up-transformer-less grid connection of photovoltaic power plants,” IEEE J. Photovolt., vol. 4, no. 3, pp. 881‒889, May 2014.

 

A Dual Control Strategy for Power Sharing Improvement In Islanded Mode of AC Microgrid

 ABSTRACT:  

Parallel operation of inverter modules is the solution to increase the reliability, efficiency, and redundancy of inverters in microgrids. Load sharing among inverters in distributed generators (DGs) is a key issue. This study investigates the feasibility of power-sharing among parallel DGs using a dual control strategy in islanded mode of a microgrid. PQ control and droop control techniques are established to control the microgrid operation. P-f and Q-E droop control is used to attain real and reactive power sharing. The frequency variation caused by load change is an issue in droop control strategy whereas the tracking error of inverter power in PQ control is also a challenge. To address these issues, two DGs are interfaced with two parallel inverters in an islanded AC microgrid. PQ control is investigated for controlling the output real and reactive power of the DGs by assigning their references. The inverter under enhanced droop control implements power reallocation to restore the frequency among the distributed generators with predefined droop characteristics. A dual control strategy is proposed for the AC microgrid under islanded operation without communication link. Simulation studies are carried out using MATLAB/SIMULINK and the results show the validity and effective power-sharing performance of the system while maintaining a stable operation when the microgrid is in islanding mode.

KEYWORDS:

1.      Microgrid

2.      Inverter parallel operation control strategy

3.      Droop control strategy

4.      Frequency restore

5.      Power sharing

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In this paper, the enhanced droop and PQ control strategies for controlling parallel DGs in islanding mode of AC micro-grids were investigated to achieve flexible power regulation. The main advantage of this dual control strategy is to enable operation without any communication between the parallel DGs. The power tracking error for PQ control based inverters was investigated and the enhanced droop control implemented with predefined droop characteristics for power reallocation was proposed. To improve and restore the frequency, a frequency restoration scheme (FRS) implemented among the distributed generators was developed. The proposed droop controller provides stable operating under different control strategies in islanded operation and the DG voltage can quickly respond to the required voltage demand. The PQ controller can effectively track the active and reactive power and the droop control provides voltage control in islanded mode. The simulation results obtained from MATLAB/SIMULINK verified the stability of the load voltage and frequency.

REFERENCES:

1. Parhizi, S., et al. (2015). State of the art in research on micro-grids: A review. IEEE Access, 3, 890–925.

2. Lopes, J. A. P., Moreira, C. L., & Madureira, A. G. (2006). Defining control strategies for micro-grids islanded operation. IEEE Transactions on Power Apparatus and Systems, 21(2), 916–924.

3. Ahmed, M. N., et al. (2015). An overview on microgrid control strategies. International Journal of Engineering and Advanced Technology (IJEAT), 4(5), 93–98.

4. Lasseter, R. H. (2002). Micro-grids. In 2002 IEEE Power Engineering Society Winter Meeting. Conference Proceedings (Cat. No.02CH37309) (Vol. 1, pp. 305–308).

5. Basak, P., Saha, A. K., Chowdhury, S., & Chowdhury, S. P. (2009). Micro-grid: Control techniques and modeling. 44th International Universities Power Engineering Conference (UPEC), Glasgow IEEE. (pp. 1–5).

Modified Cascaded H-bridge Multilevel Inverter for Hybrid Renewable Energy Applications

 ABSTRACT:

Renewable energy sources and technologies have the potential to provide solutions to the longstanding energy problems being faced by developing countries. The renewable energy sources like wind energy, solar energy, geothermal energy, ocean energy, biomass energy and fuel cell technology can be used to overcome energy shortage in India. This paper proposes a modified multi-level inverter (MLI) topology for Hybrid Renewable Energy Sources (HRES) and a design of hybrid solar-wind power generation model with 9-level, 13-level and 17-level inverter topologies. A HRES connected to a modified Cascaded H-Bridge Multi Level Inverter (CHB-MLI) is developed, whose switches are controlled using Artificial Neural Network (ANN) model. The proposed hybrid energy system model consists of 10 Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) that intend to give 17 levels of output voltage. The proposed topology performs effectively with reduced number of components and reduced Total Harmonic Distortion (THD). The performance of the proposed system is analyzed by designing the model in MATLAB/SIMULINK environment. The simulation results of the proposed inverter for the HRES application are compared with the results of the existing topologies to show the effectiveness of the proposed model.

 KEYWORDS:

1.      Battery energy storage system (BESS)

2.      Modified cascaded H-bridge Multi-level inverter (MCHBMLI)

3.      Total harmonic distortion (THD)

 SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In this paper, 9-level, 13-level and 17-level inverters are designed by employing modified cascaded MLI, followed by ANN as a control approach for the inverter. Using the ANN method, the MPP exactly searching when the solar irradiance changes sharply, and it can make the system work under a stable mode. The advantage of the ANN-based PV model method is the fast MPP approximation according to the parameters of the PV panel. The proposed new MPPT algorithm can search the MPP fast and exactly based on the feedback voltage and current with different solar irradiance and temperature of the environment. The simulations are performed in MATLAB/SIMULINK environment. The output voltage waveform shows less distortion with a reduced number of power switches and is validated by calculating THD as a performance measure. The results attained from the proposed model exhibits superiority over the previously suggested models when compared. The proposed modified system can be analyzed in the future, with different sources such as fuel cell, diesel generator, etc. in the standalone microgrid topology. This is more cost-effective due to the use of reduced number of switches and other components. Thus it helps in improving the total harmonic distortions as per the IEEE 519 standards, in terms of power quality of the islanded microgrid. The limitation of the proposed topology is that, in case of a failure of one ofH-bridges, theMLI can still be operated with decreased number of levels. However, full power cannot be supplied to the load. This can be improved by designing a fault tolerant MLI topology in the future.

REFERENCES:

1. M. A. Rosen, and I. Dincer, “Exergy as the confluence of energy, environment and sustainable development,” Exergy Int. J., Vol. 1, pp. 3–13, 2001.

2. P. Thongprasri. “Capacitor voltage balancing in the dc-link five-level full-bridge diode-clamped multilevel inverter,” 2016.

3. C. L. Kuppuswamy, and T. A. Raghavendiran. “FPGA Implementation of Carrier Disposition PWM for Closed Loop Seven Level Diode Clamped Multilevel Inverter in Speed Control of Induction Motor,” 2018.

4. F. Khoucha, S. M. Lagoun, K. Marouani, A. Kheloui, and M. El Hachemi Benbouzid, “Hybrid cascaded H-bridge multilevel-inverter induction-motor-drive direct torque control for automotive applications,” IEEE Trans. Ind. Electron., Vol. 57, no. 3, pp. 892–899, 2010.

5. V. Jammala, S. Yellasiri, and A. K. Panda, “Development of a new hybrid multilevel inverter using modified carrier SPWM switching strategy,” IEEE Trans. Power Electron., Vol. 33, no. 10, pp. 8192–8197, 2018.

A Modified Cascaded H-Bridge Multilevel Inverter For Solar Applications

 ABSTRACT:

In this paper, a modified cascaded H-bridge multilevel inverter (MLI) is proposed and designed for solar applications. Generally, as the level of conventional multilevel inverter increases, the required number of switches and size increases. The proposed topology is cascade of unit stages which involves 5 switches and two voltage source; moreover a unit stage is capable of generating 5 levels. Also, the detailed analysis of cascaded multilevel inverter is discussed which incorporates three different methodologies involving less number of power devices in order to generate maximum number of levels. This results into reduction in gate drive circuitry and less switching losses. The proposed MLI is designed for power 1.5kW and Inphase level shifting SPWM technique has been incorporated in which 5kHz carrier wave is compared with 50Hz of sinusoidal wave with a modulation index of 0.8. As a result, total harmonic distortion (THD) is achieved as 4.71% with LC-filter for above mentioned multilevel inverter. The circuits are modeled and simulated with the help of MATLAB/SIMULINK.

KEYWORDS:

1.      Modified cascaded H-bridge MLI

2.       Solar

3.      SPWM techniques

4.      Total Harmonic Distortions

 SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

In this paper, a new topology of modified cascaded H bridge MLI is designed for solar high power application. The three different methodologies have been analyzed and 9-level, 13-level and 17-level output is observed in the respective methodology. The number of switches used in the topology is less which in turn reduced the corresponding gate driving circuitry and made the circuit compact in size. The circuits of proposed MLI are simulated in MATLAB/SIMULINK and total harmonic distortions for the three methodologies are obtained by using FFT analysis window. The lowest THD observed with LC-filter is 4.71%. The proposed MLI is designed for power 1.5kW and In-Phase level shifting method is followed for the pulse generation for all three methodologies.

REFERENCES:

[1] Wei Zhao; Hyuntae Choi; G. Konstantinou; M. Ciobotaru; and V. G. Agelidis “Cascaded H-bridge Multilevel Converter for Large-scale PV Grid-Integration with Isolated DC-DC stage” PEDG, IEEE 2012.

[2] S. Rivera; S. Kouro; B. Wu; J. I. Leon; J. Rodriguez; and L. G. Franquelo "Cascaded H-bridge multilevel converter multistring topology for large scale photovoltaic systems," IEEE ISIE 2011, pp.1837-1844.

[3] N.A. Rahim; K. Chaniago; and J. Selvaraj "Single-Phase Seven-Level Grid Connected Inverter for Photovoltaic System", IEEE Transactions on Industrial Electronics, Vol. 58, No. 6, June 2011, pp. 2435-2443

[4] B. Singh; N. Mittal; and K. S. Verma “Multi-Level Inverter: A Literature Survey On Topologies And Control Strategies”, International Journal of Reviews in Computing, Vol. 10, July 2012, pp. 1-16

[5] Zhiguo pan; F .Z Peng; Victor Stefanoic; and Mickey Leuthen “A Diode-Clamped Multilevel Converter with Reduced Number of Clamping Diodes.”2004 IEEE.

A Novel Multilevel Multi-Output Bidirectional Active Buck PFC Rectifier

 ABSTRACT:

 

This paper presents a new family of buck type PFC (power factor corrector) rectifiers that operates in CCM (continuous conduction mode) and generates multilevel voltage waveform at the input. Due to CCM operation, commonly used AC side capacitive filter and DC side inductive filter are removed from the proposed modified packed U-cell rectifier structure. Dual DC output terminals are provided to have a 5-level voltage waveform at the input points of the rectifier where it is supplied by a grid via a line inductor. Producing different voltage levels reduces the voltage harmonics which affects the grid current harmonic contents directly. Low switching frequency of the proposed rectifier is a distinguished characteristic among other buck type rectifiers that reduces switching losses and any high switching frequency related issues, significantly. The proposed transformer-less, reduced filter and multilevel rectifier topology has been investigated experimentally to validate the good dynamic performance in generating and regulating dual 125V DC outputs terminals as telecommunication boards feeders or industrial battery chargers under various situation including change in the loads and change in the in main grid voltage amplitude.

KEYWORDS:

1.      Packed U-Cell

2.      PUC5

3.      HPUC

4.      Buck PFC rectifie

5.       Multilevel converter

6.      Power quality

 SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In this paper a 5-level rectifier operating in buck mode has been proposed which is called HPUC as a slight modification to PUC multilevel converter. It has been demonstrated that the proposed rectifier can deceive the grid by generating maximum voltage level of 250V at AC side as boost mode while splitting this voltage value at its two output terminals to provide buck mode of operation with 125V DC useable for battery chargers or telecommunication boards’ feeder. Although it has more active switches than other buck rectifier topologies and some limitations on power balance between loads, overall system works in boost mode and CCM which results in removing bulky AC and DC filters that usually used in conventional buck PFC rectifiers. Moreover, generating multilevel waveform leads to reduced harmonic component of the voltage waveform and consequently the line current. It also aims at operating with low switching frequency and small line inductor that all in all characterizes low power losses and high efficiency of the HPUC rectifier. Comprehensive theoretical studies and simulations have been performed on power balancing issue of the HPUC rectifier. Full experimental results in steady state and during load and supply variation have been illustrated to prove the fact that HPUC topology can be a good candidate in a new family of buck bridgeless PFC rectifiers with acceptable performance. Future works can be devoted to developing robust and nonlinear controllers on the proposed rectifier topology.

REFERENCES:

[1] 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.

[2] IEEE, "IEEE Recommended Practice and Requirements for Harmonic Control in Electric Power Systems," in IEEE Std 519-2014 (Revision of IEEE Std 519-1992), ed, 2014, pp. 1-29.

[3] IEC, "Limits for Harmonic Current Emissions (Equipment Input Current_ 16A Per Phase),"in IEC 61000-3-2 (Ed. 3.2, 2009), ed, 1995.

[4] 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," IEEE Trans. Ind. Electron., vol. 50, no. 5, pp. 962- 981, 2003.

[5] H. Choi, "Interleaved boundary conduction mode (BCM) buck power factor correction (PFC) converter," IEEE Trans. Power Electron., vol. 28, no. 6, pp. 2629-2634, 2013.

Latest 2020 IEEE Electrical Projects using Matlab/Simulink software

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