A Switched-Capacitor Inverter Using Series/Parallel Conversion with Inductive Load

 ABSTRACT

A novel switched-capacitor inverter is proposed. The proposed inverter outputs larger voltage than the input voltage by switching the capacitors in series and in parallel. The maximum output voltage is determined by the number of the capacitors. The proposed inverter, which does not need any inductors, can be smaller than a conventional two-stage unit which consists of a boost converter and an inverter bridge. Its output harmonics are reduced compared to a conventional voltage source single phase full bridge inverter. In this paper, the circuit configuration, the theoretical operation, the simulation results with MATLAB/ SIMULINK, and the experimental results are shown. The experimental results accorded with the theoretical calculation and the simulation results.

 

KEYWORDS

1.      Charge pump

2.       Multicarrier PWM

3.       Multilevel Inverter

4.       Switched capacitor (SC)

 

SOFTWARE: MATLAB/SIMULINK

CONCLUSION

 In this paper, a novel boost switched-capacitor inverter was proposed. The circuit topology was introduced. The modulation method, the determination method of the capacitance, and the loss calculation of the proposed inverter were shown. The circuit operation of the proposed inverter was confirmed by the simulation results and the experimental results with a resistive load and an inductive load. The proposed inverter outputs a larger voltage than the input voltage by switching the capacitors in series and in parallel. The inverter can operate with an inductive load. The structure of the inverter is simpler than the conventional switched-capacitor inverters. THD of the output waveform of the inverter is reduced compared to the conventional single phase full bridge inverter as the conventional multilevel inverter.

 REFERENCES

 [1] H. Liu, L. M. Tolbert, S. Khomfoi, B. Ozpineci, and Z. Du, “Hybrid cascaded multilevel inverter with PWM control method,” in Proc. IEEE Power Electron. Spec. Conf., Jun. 2008, pp. 162–166.

[2] A. Emadi, S. S. Williamson, and A. Khaligh, “Power electronics intensive solutions for advanced electric, hybrid electric, and fuel cell vehicular power systems,” IEEE Trans. Power Electron., vol. 21, no. 3, pp. 567–577, May 2006.

[3] L. G. Franquelo, J. Rodriguez, J. I. Leon, S. Kouro, R. Portillo, and M. A. M. Prats, “The age of multilevel converters arrives,” IEEE Ind. Electron. Mag., vol. 2, no. 2, pp. 28–39, Jun. 2008.

[4] Y. Hinago and H. Koizumi, “A single phase multilevel inverter using switched series/parallel DC voltage sources,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2643–2650, Aug. 2010.

[5] S. Chandrasekaran and L. U. Gokdere, “Integrated magnetics for interleaved DC–DC boost converter for fuel cell powered vehicles,” in Proc. IEEE Power Electron. Spec. Conf., Jun. 2004, pp. 356–361.

[6] Y. Hinago and H. Koizumi, “A switched-capacitor inverter using series/ parallel conversion,” in Proc. IEEE Int. Symp. Circuits Syst., May/Jun. 2010, pp. 3188–3191.

[7] J. A. Starzyk, Y. Jan, and F. Qiu, “A dc–dc charge pump design based on voltage doublers,” IEEE Trans. Circuits Syst. I, Fundam. Theory Appl., vol. 48, no. 3, pp. 350–359, Mar. 2001.

[8] M. R. Hoque, T. Ahmad, T. R. McNutt, H. A. Mantooth, and M. M. Mojarradi, “A technique to increase the efficiency of high-voltage charge pumps,” IEEE Trans. Circuits Syst. II, Exp. Briefs, vol. 53, no. 5, pp. 364–368, May 2006.

[9] O. C.Mak and A. Ioinovici, “Switched-capacitor inverter with high power density and enhanced regulation capability,” IEEE Trans. Circuits Syst. I, Fundam. Theory Appl., vol. 45, no. 4, pp. 336–347, Apr. 1998.

[10] B. Axelrod, Y. Berkovich, and A. Ioinovici, “A cascade boost-switchedcapacitor- converter-two level inverter with an optimized multilevel output waveform,” IEEE Trans. Circuits Syst. I, Reg. Papers, vol. 52, no. 12, pp. 2763–2770, Dec. 2005.

[11] J. I. Rodriguez and S. B. Leeb, “A multilevel inverter topology for inductively coupled power transfer,” IEEE Trans. Power Electron., vol. 21, no. 6, pp. 1607–1617, Nov. 2006.

[12] X. Kou, K. A. Corzine, and Y. L. Familiant, “A unique fault-tolerant design for flying capacitor multilevel inverter,” IEEE Trans. Power Electron., vol. 19, no. 4, pp. 979–987, Jul. 2004.

[13] S. Lu, K. A. Corzine, andM. Ferdowsi, “A unique ultracapacitor direct integration scheme in multilevel motor drives for large vehicle propulsion,” IEEE Trans. Veh. Technol., vol. 56, no. 4, pp. 1506–1515, Jul. 2007.

[14] J. I. Leon, S. Vazquez, A. J. Watson, L. G. Franquelo, P. W. Wheeler, and J. M. Carrasco, “Feed-forward space vector modulation for single-phase multilevel cascaded converters with any dc voltage ratio,” IEEE Trans. Ind. Electron., vol. 56, no. 2, pp. 315–325, Feb. 2009.

[15] B. P. McGrath and D. G. Holmes, “Multicarrier PWM strategies for multilevel inverters,” IEEE Trans. Ind. Electron., vol. 49, no. 4, pp. 858–867, Aug. 2002.

[16] R. Gupta, A. Ghosh, and A. Joshi, “Switching characterization of cascaded multilevel-inverter-controlled systems,” IEEE Trans. Ind. Electron., vol. 55, no. 3, pp. 1047–1058, Mar. 2008.

[17] J. Zhang, Y. Zou, X. Zhang, and K. Ding, “Study on a modified multilevel cascade inverter with hybrid modulation,” in Proc. IEEE Power Electron. Drive Syst., Oct. 2001, pp. 379–383.

[18] V. G. Agelidis, A. I. Balouktsis, and C. Cossar, “On attaining the multiple solutions of selective harmonic elimination PWM three-level waveforms through function minimization,” IEEE Trans. Ind. Electron., vol. 55, no. 3, pp. 996–1004, Mar. 2008.

[19] J. A. Pontt, J. R. Rodriguez, A. Liendo, P. Newman, J. Holtz, and J. M. San Martin, “Network-friendly low-switching-frequency multipulse high-power three-level PWM rectifier,” IEEE Trans. Ind. Electron., vol. 56, no. 4, pp. 1254–1262, Apr. 2009.

[20] M. K. Kazimierczuk, “Switching losses with linear MOSFET output capacitance,” in Pulse-Width Modulated DC–DC Power Converters, 1st ed. West Sussex, U.K.: Wiley, 2008, ch. 2, pp. 37–38, sec. 2.

Fixed Switching Frequency Sliding Mode Control for Single-Phase Unipolar Inverters

ABSTRACT:

Sliding mode control (SMC) is recognized as robust controller with a high stability in a wide range of operating conditions, although it suffers from chattering problem. In addition, it cannot be directly applied to multi switches power converters. In this paper, a high performance and fixed switching frequency sliding mode controller is proposed for a single-phase unipolar inverter. The chattering problem of SMC is eliminated by smoothing the control law in a narrow boundary layer, and a pulse width modulator produces the fixed frequency switching law for the inverter. The smoothing procedure is based on limitation of pulse width modulator. Although the smoothed control law limits the performance of SMC, regulation and dynamic response of the inverter output voltage are in an acceptable superior range. The performance of the proposed controller is verified by both simulation and experiments on a prototype 6-kVA inverter. The experimental results show that the total harmonic distortion of the output voltage is less than 1.1% and 1.7% at maximum linear and nonlinear load, respectively. Furthermore, the output dynamic performance of the inverter strictly conforms the standard IEC62040-3. Moreover, the measured efficiency of the inverter in the worst condition is better than 95.5%.

KEYWORDS:

1.        Pulse widthmodulator

2.          Sliding modecontrol

3.        Unipolar single phaseinverter

 SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

 

In this paper, a fixed frequency SMC was presented for a single-phase inverter. The performance of the proposed controller has been demonstrated by a 6-kVA prototype. Experimental results show that the inverter is categorized in class1 of the IEC64020-3 standard for output dynamic performance. The inverter efficiency was measured up to 95.5% in the worst case.

Since the direct SMC cannot be applied to four switches unipolar inverter and it also suffers from the chattering problem, a PWM is employed to generate a fixed frequency switching law. The PWM modulates the smoothed discontinuous control law which is produced by SMC. To smooth the control law, the limitation of the PWM was considered.

The simulation and experimental results show that the load regulation is about 1% at the steady state as well. But, to obtain better regulation, a resonance compensator was added in the voltage loop. With this compensator, the load regulation was measured which has been below 0.2%.

REFERENCES:

[1] G. Venkataramanan and D.M. Divan, “Discrete time integral sliding mode control for discrete pulse modulated converters,” in Proc. 21st Annu. IEEE Power Electron. Spec. Conf.,  San Antonio, TX, 1990, pp.67–73.

[2] J.Y.Hung,W. Gao, and J. C.Hung, “Variable structure control:Asurvey,” IEEE Trans. Ind. Electron., vol. 40, no. 1, pp. 2–22, Feb. 1993.

[3] E. Fossas and A. Ras, “Second order sliding mode control of a buck converter,” in Proc. 41st IEEE Conf. Decision Control, 2002, pp. 346– 347.

[4] C. Rech, H. Pinheiro, H. A. Gr¨undling, H. L. Hey, and J. R. Pinheiro, “A modified discrete control law for UPS applications,” IEEE Trans. Power Electron., vol. 18, no. 5, pp. 1138–1145, Sep. 2003.

[5] K. S. Low, K. L. Zhou, and D.W.Wang, “Digital odd harmonic repetitive control of a single- phase PWM inverter,” in Proc. 30th Annu. Conf. IEEE Ind. Electron. Soc., Busan, Korea, Nov. 2–6, 2004, pp. 6–11.

ABSTRACT:

 

The scarcity of fossil fuel and the increased pollution leads the use of Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV) instead of conventional Internal Combustion (IC) engine vehicles. An Electric Vehicle requires an on-board charger (OBC) to charge the propulsion battery. The objective of the project work is to design a multifunctional on-board charger that can charge the propulsion battery when the Electric Vehicle (EV) connected to the grid. In this case, the OBC plays an AC-DC converter. The surplus energy of the propulsion battery can be supplied to the grid, in this case, the OBC plays as an inverter. The auxiliary battery can be charged via the propulsion battery when PEV is in driving stage. In this case, the OBC plays like a low voltage DC-DC converter (LDC). An OBC is designed with Boost PFC converter at the first stage to obtain unity power factor with low Total Harmonic Distortion (THD) and a Bi-directional DC-DC converter to regulate the charging voltage and current of the propulsion battery. The battery is a Li-Ion battery with a nominal voltage of 360 V and can be charged from depleted voltage of 320 V to a fully charged condition of 420 V. The function of the second stage DC-DC converter is to charge the battery in a Constant Current and Constant Voltage manner. While in driving condition of the battery the OBC operates as an LDC to charge the Auxiliary battery of the vehicle whose voltage is around 12 V. In LDC operation the Bi-Directional DC-DC converter works in Vehicle to Grid (V2G) mode. A 1KW prototype of multifunctional OBC is designed and simulated in MATLAB/Simulink. The power factor obtained at full load is 0.999 with a THD of 3.65 %. The Battery is charged in A CC mode from 320 V to 420 V with a constant battery current of 2.38 A and the charging is switched into CV mode until the battery current falls below 0.24 A. An LDC is designed to charge a 12 V auxiliary battery with CV mode from the high voltage propulsion battery.

KEYWORDS:

1.      Bi-directional DC-DC converter

2.      Boost PFC converter

3.      Electric vehicle

4.      Low voltage DC-DC converter

5.      Vehicle-to-grid.

 

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

An On-Board Electric Vehicle charger is designed for level 1 charging with a 230 V input supply. Different stages of an OBC is stated and the challenges are listed. The developments have been implemented to overcome key issues. A two stage charger topology with active PFC converter at the front end followed by a Bi-directional DC-DC converter is designed. The active PFC which is a Boost converter type produces less than 5 % THD at full load. Moreover, the PFC converter is applicable to wide variation in loads. The detailed design of the power stage, as well as the controller, is discussed with the simulated results.

A second stage DC-DC converter is designed and simulated for the charging current and voltage regulation. The converter performs very precisely by charging the propulsion battery in CC/CV mode over a wide range of voltage. A V2G controller has been developed for the DC-DC converter in order to supply power to the grid from the propulsion battery. A new Low-Voltage DC-DC converter is proposed to charge the Auxiliary battery via the propulsion battery utilizing the same OBC. The battery voltage and current waveforms are presented and the performance of the designed converter is verified.

REFERENCES:

[1] “No Title,” https://en.wikipedia.org/wiki/Electric_vehicle. .

[2] S. S. Williamson, Energy management strategies for electric and plug-in hybrid electric vehicles. Springer, 2013.

[3] a. Emadi and K. Rajashekara, “Power Electronics and Motor Drives in Electric, Hybrid Electric, and Plug-In Hybrid Electric Vehicles,” IEEE Trans. Ind. Electron., vol. 55, no. 6, pp. 2237–2245, 2008.

[4] M. Yilmaz and P. T. Krein, “Review of charging power levels and infrastructure for plug-in electric and hybrid vehicles,” 2012 IEEE Int. Electr. Veh. Conf. IEVC 2012, vol. 28, no. 5, pp. 2151–2169, 2012.

[5] H. Wang, S. Dusmez, and A. Khaligh, “Design and analysis of a full-bridge LLC-based PEV charger optimized for wide battery voltage range,” IEEE Trans. Veh. Technol., vol. 63, no. 4, pp. 1603–1613, 2014.

 

A PWM Strategy Based on State Transition for Cascaded H-Bridge Inverter under Unbalanced DC Sources

ABSTRACT:  

 

 Cascaded H-bridge converter has been widely used and researched in industry, since it is suitable for the operation under both normal and fault conditions. This paper proposes a novel PWM strategy based on state transition for cascaded H-Bridge inverter with unbalanced DC sources to achieve high quality line-to-line output voltages and maximize the linear modulation range. In this modulation strategy, the duration time of each switching state will be modified directly through the correction value. Ranges of correction value are derived by analyzing the modulation index limitation. Then, proper correction value is added into duration times to transform the switching states and extend modulation index to the maximum value. Meanwhile, balanced AC currents can be obtained under unbalanced DC sources condition, even under larger unbalanced coefficients. Furthermore, a three-phase power control algorithm (PCA) is introduced to achieve the balanced distribution of three-phase power. Compared with the traditional zero-sequence voltage injection method, the proposed strategy is more convenient and effective theoretically, and it can be applied to the higher-level cascaded H-bridge converter. The advantage and effectiveness of the proposed strategy are verified by simulation and experiment results.

KEYWORDS:

 

1.      State transition

2.      Linear modulation range

3.      Unbalanced DC sources

4.      Power control algorithm

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

A novel PWM strategy based on state transition for CHBI with unbalanced DC sources has been proposed in this paper. Compared with ZSVIM and NVM, the duration times of each switch states can be modified directly by correction value and the gate signals can be acquired easily through ST-PWM. To acquire the maximum linear modulation index, the reason of the modulation index limitation and the novel modulation strategy based on the state transition are studied. The proposed strategy can achieve high quality line-to-line output voltages and extend the modulation range as high as possible. Besides, the three-phase power control algorithm is introduced to acquire balanced power distribution. The effectiveness has been verified by simulation and experiment results.

In our current work, we incorporate PCA into the ST-PWM strategy, which is a prototype of multi-objective control. Since both modulation index extension and power control are achieved by adjusting ΔT, there is a conflict on the control objectives. That is to say, the control ability of PCA will decrease when the modulation index is extended. However, we have not yet found a strict mathematical relationship between them due to time constraints. And we will do a further research on multi-objective optimal PWM strategy and multi-objective control boundaries under unbalanced dc sources in the future.

REFERENCES:

[1] A. Marzoughi, R. Burgos, D. Boroyevich, and Y. Xue, "Investigation and comparison of cascaded H-bridge and modular multilevel converter topologies for medium-voltage drive application," in Industrial Electronics Society, IECON 2014 - 40th Annual Conference of the IEEE, 2014, pp. 1562-1568.

[2] 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, Aug. 2010.

[3] X. Zha, L. Xiong, J. Gong and F. Liu, "Cascaded multilevel converter for medium-voltage motor drive capable of regenerating with part of cells," IET Power Electronics, vol. 7, no. 5, pp. 1313-1320, May. 2014.

[4] G. Farivar, C. D. Townsend, B. Hredzak, J. Pou, and V. G. Agelidis, "Low-capacitance cascaded H-bridge multilevel StatCom," IEEE Trans. Power Electron., vol. 32, no. 3, pp. 744-1754, Mar. 2017.

[5] K. D. Teryima, G. Y. Nentawe, and A. O. David, "A Overlapping Carrier Based SPWM for a 5-Level Cascaded H-bridge Multilevel Inverter," International Journal of Power Electronics and Drive Systems (IJPEDS), vol. 7, no. 2, pp. 349-357, 2016.

A Physical Deterministic Inverse Method for Operational Satellite Remote Sensing: An Application for Sea Surface Temperature Retrievals

 ABSTRACT:  

We propose a new deterministic approach for remote sensing retrieval, called modified total least squares (MTLS), built upon the total least squares (TLS) technique. MTLS implicitly determines the optimal regularization strength to be applied to the normal equation first-order Newtonian retrieval using all of the noise terms embedded in the residual vector. The TLS technique does not include any constraint to prevent noise enhancement in the state space parameters from the existing noise in measurement space for an inversion with an ill-conditioned Jacobian. To stabilize the noise propagation into parameter space, we introduce an additional empirically derived regularization proportional to the logarithm of the condition number of the Jacobian and inversely proportional to the L2-norm of the residual vector. The derivation, operational advantages and use of the MTLS method are demonstrated by retrieving sea surface temperature from GOES-13 satellite measurements. An analytic equation is derived for the total retrieval error, and is shown to agree well with the observed error. This can also serve as a quality indicator for pixel-level retrievals. We also introduce additional tests from the MTLS solutions to identify contaminated pixels due to residual clouds, error in the water vapor profile and aerosols. Comparison of the performances of our new and other methods, namely, optimal estimation and regression-based retrieval, is performed to understand the relative prospects and problems associated with these methods. This was done using operational match-ups for 42 months of data, and demonstrates a relatively superior temporally consistent performance of the MTLS technique.

KEYWORDS:

1.      Condition number of matrix

2.      Ill-conditioned inverse methods

3.      Regularization

4.      Satellite remote sensing

5.      Sea surface temperature (SST)

6.      Total error

7.      Total least squares (TLS)

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

We have demonstrated in this work the advantage of the MTLS, which is the family of the deterministic inverse methods, for producing SST retrievals compared with other prevailing methods. In addition, it is noteworthy that MTLS does not require additional error information, e.g., well-specified errors in observational and a priori information. This may provide a significant advantage for climate-based applications where retrievals should be as independent of external error sources as possible. The MTLS retrieval is improved by using the newer version of CRTM, which implies that more accurate forward models and ancillary data can further reduce the remaining MTLS error. This package can also calculate a metric relating to the total retrieval error and automatic QI at individual pixel level. Apart from the QI, MTLS is also capable of identifying the most difficult retrievals due to cloud contamination or high WV profile error. The sensitivity analysis confirms that MTLS solution is independent of a priori/IG error. The data driven dynamic regularization property of MTLS regularizes solutions toward the IG when the problem is either highly ill-conditioned or has high observation error or both to keep the solution below the a priori error. It is found that OEM retrieval, at least as implemented for this problem, is worse than the LS solution, and sometimes worse than the a priori error, irrespective of the version of CRTM. OEM is the most popular choice for physically based operational retrievals due to the assumption that a priori based constraining of an ill-posed inversion should still yield reasonable reasonable results under conditions where there may be unaccounted for parameters or unforeseen errors, as may be the case in real-world retrieval problems. However, these results suggest that this view may be based more on perception of idealized Bayesian statistics rather than comparative scientific study with respect to alternative methods. This study has also demonstrated that the sensitivity of OEM retrievals under practical circumstances renders it more vulnerable to noise than MTLS retrievals. Even by employing dynamic error covariance matrices, OEM is unable to produce the best retrieval for a fairly linear and moderately ill-conditioned problem of SST retrieval. Moreover, the estimation of error of the errors, which is a prerequisite for OEM, is rather difficult in practice, which perhaps explains why OEM results do not match the expectation from the theory of adding to/constraining by a priori knowledge. To date, operational SST retrievals are dominated by regression (REGB), which highly simplifies RT physics. Mostly, it does produce reasonable results (SD) due to the fact that the global variance of SST fields itself is not very high (e.g., compared with gaseous distributions) and the atmospheric attenuation for 3.9-μm channel is rather low, but such methods are still subject to biases on a spatial and temporal basis, with seasonal variations, and has no inherent means of correcting for them. This derivation of MTLS is based on linear algebra. However, this paper illustrates that a deterministic classical mathematics approach can produce better retrievals for real-world RT problems compared with more recent probability-based mathematics that solve ill-posed problems using covariance matrices. The MTLS retrievals outperform the OEM retrievals due to the fact that the regularization in MTLS is data driven. As opposed to OEM that uses regularization from user-defined a priori knowledge of measurement error and forward model error, as well as a priori knowledge error of the retrieved target parameter. A reliable estimation of both the errors in an operational environment is very difficult due to the highly dynamic atmosphere, fast forward model error, including NCEP data, as well as error in the measurements. An alternate effort toward error estimation using simulation minus observation (S-O) bias correction leads to further ambiguities and may potentially mislead our fundamental science understanding. With the advent of newer sensors with improved multispectral capabilities (e.g., the Visible and Infrared Imaging Radiometer Suite and the future Advanced Baseline Imager), employing a deterministic physical method for simultaneous retrieval of SST and WV (critical for weather and climate studies), such as the MTLS package, has the potential to provide substantial improvements in the use of satellite data and derived products.

REFERENCES:

[1] P. Le Borgne, H. Roquet, and C. J. Merchant, “Estimation of sea surface temperature from the spinning enhanced visible and infrared imager, improved using numerical weather prediction,” Remote Sens. Environ., vol. 115, no. 1, pp. 55–65, Jan. 2011.

[2] C. D. Rodgers, Inverse Methods for Atmospheric Soundings: Theory and Practice. Singapore: World Scientific, 2000.

[3] S. Twomey, An Introduction to the Mathematics of Inversion in Remote Sensing and Indirect Measurements. New York, NY, USA: Elsevier, 1977.

[4] J. T. Houghton, F. W. Taylor, and C. D. Rodgers, Remote Sounding of Atmospheres. Cambridge, U.K.: Cambridge Univ. Press, 1984.

[5] J. L. Mead, “Parameter estimation: A new approach to weighting a priori information,” J. Inv. Ill-Posed Probl., vol. 16, no. 2, pp. 1–21, 2007.

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.

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