Electrical engineering is a professional engineering discipline that generally deals with the study and application of electricity, electronics, and electromagnetism. This field first became an identifiable occupation in the later half of the 19th century after commercialization of the electric telegraph, the telephone, and electric power distribution and use. Subsequently, broadcasting and recording media made electronics part of daily life. The invention of the transistor, and later the integrated circuit, brought down the cost of electronics to the point they can be used in almost any household object.
This paper presents a study on the modeling of a STAT-COM (Static Synchronous Compensator) used for reactive power compensation on a distribution network. The power circuits of the D-STATCOM and the distribution network are modeled by specific blocks from the Power System Blockset while the control system is modeled by Simulink blocks. Static and dynamic performance of a E3 Mvar D-STATCOM on a 25-kV network is evaluated. An “average modeling” approach is proposed to simplify the PWM inverter operation and to accelerate the simulation for control parameters adjusting purpose. Simulation performance obtained with both modeling approaches are presented and compared.
Fig. 1. The cascade H-bridge converter based DSTATCOM.
EXPECTED SIMULATION RESULTS
Fig. 2 Waveforms illustrating the D-STATCOM dynamic performance.
Fig. 3 Voltage and current waveforms during the change from inductive to capacitive operation at t = 0.2 s.
Fig. 4 Comparison between responses of detailed and average models for a step change in the network internal voltage.
A detailed model of a D-STATCOM has been developed for use in Simulink environment with the Power System Blockset. Models of both power circuit and control system have been implemented in the same Simulink diagram allowing smooth simulation. Two modeling approaches (device and average modeling) have been presented and applied to the case of a +3Mvar D-STATCOM connected to a 25-kV distribution network. The obtained simulation results have demonstrated the validity of the developed models. Average modeling allows a faster simulation which is well suited to controller tuning purposes.
 K.K. Sen, “STATCOM: Theory, Modeling, Applications,” in IEEE PES 1999 Winter Meeting Proceedings, pp. 11 77- 1183.
 Flexible AC Transmission Systems (FACTS), edited by Y.H. Song and A.T. Johns, The Institution of Electrical Engineers, London, UK, 1999.
 K.V. Patil, et al., “Application of STATCOM for Damping Torsional Oscillations in Series Compensated AC Systems,” IEEE Trans. on Energy Conversion, Vol. 13, No. 3,Sept. 1998, pp.237-243.
 C.D. Schauder, H. Mehta, “Vector Analysis and Control of Advanced Static VAR Compensators,” IEE Proceedings- [SI Power System Blockset For Use with Sirnulink, User’s Guide, The MathWorks Inc., 2000. C, Vol. 140, NO. 4, July 1993, pp. 299-306.
This paper presents the simulation studies on a Cascaded H-Bridge converter based Distribution Static Synchronous Compensator (DSTATCOM) for improving the power quality of a distribution system. Voltage source converter based DSTATCOM has been established as the most preferred solution for management of reactive power in distribution utilities and for improving voltage regulation, power factor and power quality in industries. For high power applications, cascaded H-Bridge converter is the most ideal choice compared to two-level inverter with series connected power devices. In the present work DSTATCOM controller is designed using DQO modelling for reactive power management and thereby improving the power factor in distribution systems. The dc link voltage and the three phase load currents are used as feedback signals for the controller and it is designed in such a way that DSTATCOM is able to supply the reactive current demanded by the load both during steady state and transient conditions using sinusoidal pulse width modulation control.
- Cascaded H-Bridge Converter
- Reactive power compensation
- Sinusoidal PWM
SIMULINK BLOCK DIAGRAM:
Fig. 1. The cascade H-bridge converter based DSTATCOM.
EXPECTED SIMULATION RESULTS
Fig. 2. The phase voltage (top trace ) and line-to-line voltages of H-bridge cascaded inverter.
Fig. 3. Source phase voltage (top trace) and source phase Current (bottom trace) with DSTATCOM in closed loop power factor control mode.
Fig. 4. DC link voltage (Vd,) (Top or First Trace), direct and quadrature axis source currents (Second Trace) ,inverter currents Id and Iq (Third Trace) and load reactive current (Bottom Trace).
Fig 5. Individual Capacitor voltages of three level Cascaded H-Bridge Inverter.
The paper presents the principle of operation of cascaded H-bridge converter and simulation studies on cascaded converter based DSTATCOM using Sinusoidal PWM control. It is observed that the DSTATCOM is capable of supplying the reactive power demanded by the load both during steady state and transient operating conditions. The harmonics in cascaded H-bridge three-level inverter current are less compared to two-level inverter operating at same switching frequency.
 Jih-Sheng Lal, Fang Zheng Peng,” Multilevel Converters – A New Breed of Power Converters”, IEEE Transactions on Industry Applications, Vol.32, no.3, pp.509,1996.
 Muni B.P., Rao S.E., Vithal J.V.R., Saxena S.N., Lakshminarayana S., Das R.L., Lal G., Arunachalam M., “DSTATCOM for Distribution Utility and Industrial Applications”, Conference Proceedings, IEEE, Region Tenth Annual Conference, TENCON-03. Page(s): 278- 282 Vol. 1
 Bishnu P. Muni, S.Eswar Rao, JVR Vithal and SN Saxena, “Development of Distribution STATCOM for power Distribution Network” Conference Records, International conference on “Present and Future Trends in Transmission and Convergence”, New Delhi, Dec.2002,pp. VII_26-33.
 F.Z. Peng, J. S. Lai, J.W. Mckeever, J. Van Coevering, “A Multilevel Voltage – Source inverter with Separate dc sources for Static Var Generation” IEEE Transactions on Industry Applications, Vol. 32, No. 5, Sep 1996, ppl 130-1138.
 K.Anuradha, B.P.Muni, A.D.Rajkumar,” Simulation of Cascaded HBridge Converter Based DSTATCOM” First IEEE Conference on Industrial Electronics and Applications, May 2006, pp 501-505.
Power Electronics Projects Maharashtra -2015/2016/2017
Asoka technologies provide Power Electronics Projects Telangana
ELECTRICAL ENGINEERING is a field of engineering that generally deals with the study and application of electricity, electronics. This field first became an referable occupation in the later half of the 19th century. After degradation of the electric telegraph, the telephone and electric power distribution and use. Finally, broad casting and recording media made electronics part of daily life.The invention of the transistor, and later the integrated circuit, reduced the cost of electronics. Thus it can be used in almost any household object.
POWER ELECTRONICS is the application of solid-state electronics to the control and conversion of electric power. The first high power electronic devices were mercury-arc valves. In modern systems, the semiconductor switching devices performs the conversion. Examples of these devices are diodes, thyristors and transistors, pioneered by R. D. Middlebrook and others beginning in the 1950s. In contrast to electronic systems, in power electronics substantial amounts of electrical energy are processed. An AC/DC converter (rectifier) is the most typical power electronics device. It is found in many consumer electronic devices, e.g. television sets, personal computers, battery chargers, etc. The power range is typically from tens of watts to several hundred watts. In industry a common application is the variable speed drive (VSD) that is used to control an induction motor. The power range of VSDs start from a few hundred watts and end at tens of megawatts.
An ELECTRIC POWER SYSTEM is a network of electrical components deployed to supply, transfer, and use electric power. An example of an electric power system is the the grid that provides power to an extended area. An electrical grid power system can be broadly divided into the generators, the transmission system and the distribution system. The generators supply the power. The transmission system carries the power from the generating centres to the load centres. The distribution system feeds the power to nearby homes and industries. Smaller power systems are also found in industry, hospitals, commercial buildings and homes. The majority of these systems rely upon three-phase AC power—the standard for large-scale power transmission and distribution across the modern world. Specialised power systems that do not always rely upon three-phase AC power are found in aircraft, electric rail systems, ocean liners and automobiles.
Power Electronics Projects Maharashtra
This paper presents a high-efficiency and high-step up non isolated interleaved dc–dc converter with a common active clamp circuit. In the presented converter, the coupled-inductor boost converters are interleaved. A boost converter is used to clamp the voltage stresses of all the switches in the interleaved converters, caused by the leakage inductances present in the practical coupled inductors, to a low voltage level. The leakage energies of the interleaved converters are collected in a clamp capacitor and recycled to the output by the clamp boost converter. The proposed converter achieves high efficiency because of the recycling of the leakage energies, reduction of the switch voltage stress, mitigation of the output diode’s reverse recovery problem, and interleaving of the converters. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed, and its experimental results are presented for validation.
- Boost converter
- Coupled-inductor boost converter
- Dc–dc power converter
- High voltage gain
Fig. 1. (a) Parallel diode clamped coupled-inductor boost converter and (b) proposed interleaved coupled-inductor boost converter with single boost converter clamp (for n = 3).
EXPECTED SIMULATION RESULTS:
Fig. 2. (a) Drain-to-source voltage of the switch in a coupled-inductor boost converter without any clamping and (b) output voltage, clamp voltage and drain to- source voltage of the switch in a coupled-inductor boost converter with the proposed active-clamp circuit.
Fig. 3. (a) From top to bottom: total input current of the converter, input currents of the interleaved coupled-inductor boost converters, and (b) primary current, secondary current, and leakage current in a phase of the interleaved coupled-inductor boost converters.
Fig. 4. (a) Gate pulses to the clamp boost converter and (b) inductor current of the clamp boost converter.
Fig. 5. Gate pulses to the interleaved coupled-inductor boost converters (10 V/div).
Coupled-inductor boost converters can be interleaved to achieve high-step-up power conversion without extreme duty ratio operation while efficiently handling the high-input current. In a practical coupled-inductor boost converter, the switch is subjected to high voltage stress due to the leakage inductance present in the non ideal coupled inductor. The presented active clamp circuit, based on single boost converter, can successfully reduce the voltage stress of the switches close to the low-level voltage stress offered by an ideal coupled-inductor boost converter. The common clamp capacitor of this active-clamp circuit collects the leakage energies from all the coupled-inductor boost converters, and the boost converter recycles the leakage energies to the output. Detailed analysis of the operation and the performance of the proposed converter were presented in this paper. It has been found that with the switches of lower voltage rating, the recovered leakage energy, and the other benefits of an ideal coupled-inductor boost converter and interleaving, the converter can achieve high efficiency for high-step-up power conversion. A prototype of the converter was built and tested for validation of the operation and performance of the proposed converter. The experimental results agree with the analysis of the converter operation and the calculated efficiency of the converter.
 L. Solero, A. Lidozzi, and J. A. Pomilio, “Design of multiple-input power converter for hybrid vehicles,” IEEE Trans. Power Electron., vol. 20, no. 5, pp. 107–116, Sep. 2005.
 A. A. Ferreira, J. A. Pomilio, G. Spiazzi, and de Araujo Silva, “Energy management fuzzy logic supervisory for electric vehicle power supplies system,” IEEE Trans. Power Electron., vol. 20, no. 1, pp. 107–115, Jan. 2008.
 A. Emadi, K. Rajashekara, S. S. Williamson, and S. M. Lukic, “Topological overview of hybrid electric and fuel cell vehicular power system architectures and configurations,” IEEE Trans. Veh. Technol., vol. 54, no. 3, pp. 763–770, May 2007.
 J. Bauman and M. Kazerani, “A comparative study of fuel cell-battery, fuel cell-ultracapacitor, and fuel cell-battery-ultracapacitor vehicles,” IEEE Trans. Veh. Technol., vol. 57, no. 2, pp. 760–769, Mar. 2008.
 Q. Zhao and F. C. Lee, “High-efficiency, high step-up DC–DC converters,” IEEE Trans. Power Electron., vol. 18, no. 1, pp. 65–73, Jan. 2003.
This paper presents a hybrid-type full-bridge dc/dc converter with high efficiency. Using a hybrid control scheme with a simple circuit structure, the proposed dc/dc converter has a hybrid operation mode. Under a normal input range, the proposed converter operates as a phase-shift full-bridge series-resonant converter that provides high efficiency by applying soft switching on all switches and rectifier diodes and reducing conduction losses. When the input is lower than the normal input range, the converter operates as an active-clamp step-up converter that enhances an operation range. Due to the hybrid operation, the proposed converter operates with larger phase-shift value than the conventional converters under the normal input range. Thus, the proposed converter is capable of being designed to give high power conversion efficiency and its operation range is extended. A 1-kW prototype is implemented to confirm the theoretical analysis and validity of the proposed converter.
- Active-clamp circuit
- Full-bridge circuit
- Phase shift control.
Fig. 1. Circuit diagram of the proposed hybrid-type full-bridge dc/dc converter.
EXPECTED SIMULATION RESULTS:
Fig. 2. Experimental waveforms for the gate signals and output voltage according to the operation mode. (a) PSFB series-resonant converter mode when Vd = 350 V. (b) Active-clamp step-up converter when Vd = 250 V.
Fig. 3. Experimental waveforms for soft switching in the PSFB series resonant converter mode. (a) ZVS turn-on of S1 . (b) ZVS turn-on and ZCS turn-off of S2
.Fig. 4. Experimental waveforms for the current stress when Vd = 350 V. (a) Conventional PSFB series-resonant converter. (b) Proposed converter.
Fig. 5. Experimental waveforms for the input voltage Vd and output voltage Vo in the transition-state.
The novel hybrid-type full-bridge dc/dc converter with high efficiency has been introduced and verified by the analysis and experimental results. By using the hybrid control scheme with the simple circuit structure, the proposed converter has both the step-down and step-up functions, which ensure to cover the wide input range. Under the normal input range, the proposed converter achieves high efficiency by providing soft switching technique to all the switches and rectifier diodes, and reducing the current stress. When the input is lower than the normal input range, the proposed converter provides the step-up function by using the active-clamp circuit and voltage doubler, which extends the operation range. To confirm the validity of the proposed converter, 1 kW prototype was built and tested. Under the normal input range, the conversion efficiency is over 96% at full-load condition, and the input range from 250 to 350 V is guaranteed. Thus, the proposed converter has many advantages such as high efficiency and wide input range.
 J. A. Sabat´e, V. Vlatkovic, R. B. Ridley, F. C. Lee, and B. H. Cho, “Design considerations for high-voltage high-power full-bridge zero-voltage switching PWM converter,” in Proc. Appl. Power Electron. Conf., 1990, pp. 275–284.
 I. O. Lee and G. W. Moon, “Phase-shifted PWM converter with a wide ZVS range and reduced circulating current,” IEEE Trans. Power Electron., vol. 28, no. 2, pp. 908–919, Feb. 2013.
 Y. S. Shin, S. S. Hong, D. J. Kim, D. S. Oh, and S. K. Han, “A new changeable full bridge dc/dc converter for wide input voltage range,” in Proc. 8th Int. Conf. Power Electron. ECCE Asia, May 2011, pp. 2328–2335.
 P. K. Jain, W., Kang, H. Soin, and Y. Xi, “Analysis and design considerations of a load and line independent zero voltage switching full bridge dc/dc converter topology,” IEEE Trans. Power Electron., vol. 17, no. 5, pp. 649–657, Sep. 2002.
 I. O. Lee and G. W. Moon, “Soft-switching DC/DC converter with a full ZVS range and reduced output filter for high-voltage application,” IEEE Trans. Power Electron., vol. 28, no. 1, pp. 112–122, Jan. 2013.
This paper proposes a hybrid static synchronous compensator (hybrid-STATCOM) in a three-phase power transmission system that has a wide compensation range and low DC-link voltage. Because of these prominent characteristics, the system costs can be greatly reduced. In this paper, the circuit configuration of hybrid-STATCOM is introduced first. Its V-I characteristic is then analyzed, discussed, and compared with traditional STATCOM and capacitive-coupled STATCOM (C-STATCOM). The system parameter design is then proposed on the basis of consideration of the reactive power compensation range and avoidance of the potential resonance problem. After that, a control strategy for hybrid-STATCOM is proposed to allow operation under different voltage and current conditions, such as unbalanced current, voltage dip, and voltage fault. Finally, simulation and experimental results are provided to verify the wide compensation range and low DC-link voltage characteristics and the good dynamic performance of the proposed hybrid-STATCOM.
- Capacitive-coupled static synchronous compensator (C-STATCOM)
- Hybrid static synchronous compensator (hybrid-STATCOM)
- Static synchronous compensator (STATCOM)
- Wide compensation range
- Low DC-link voltage
Fig. 1. Circuit configuration of the hybrid-STATCOM.
EXPECTED SIMULATION RESULTS:
Fig. 2. Dynamic compensation waveforms of load voltage, source current, and load and source reactive powers by applying hybrid-STATCOM under different loadings cases.
Fig. 3 Dynamic compensation waveforms of vx and isx by applying hybrid-STATCOM under (a) inductive load, (b) capacitive load and (c) changing from capacitive load to inductive load.
Fig. 4. Dynamic compensation waveforms of vx and isx by applying hybrid-STATCOM under unbalanced loads.
Fig. 5. Dynamic compensation waveforms of vx and isx by applying hybrid-STATCOM under voltage fault condition.
Fig. 6. Dynamic compensation waveforms of vx and isx by applying hybrid-STATCOM during voltage dip.
In this paper, a hybrid-STATCOM in three-phase power system is proposed and discussed as a cost-effective reactive power compensator for medium voltage level application. The system configuration and V-I characteristic of the hybrid-STATCOM are analyzed, discussed, and compared with traditional STATCOM and C-STATCOM. In addition, its parameter design method is proposed on the basis of consideration of the reactive power compensation range and prevention of a potential resonance problem. Moreover, the control strategy of the hybrid-STATCOM is developed under different voltage and current conditions. Finally, the wide compensation range and low DC-link voltage characteristics with good dynamic performance of the hybrid-STATCOM are proved by both simulation and experimental results.
 J. Dixon, L. Moran, J. Rodriguez, and R. Domke, “Reactive power compensation technologies: State-of-the-art review,” Proc. IEEE, vol. 93, no. 12, pp. 2144–2164, Dec. 2005.
 L. Gyugyi, R. A. Otto, and T. H. Putman, “Principles and applications of static thyristor-controlled shunt compensators,” IEEE Trans. Power App. Syst., vol. PAS-97, no. 5, pp. 1935–1945, Sep./Oct. 1978.
 T. J. Dionise, “Assessing the performance of a static var compensator for an electric arc furnace,” IEEE Trans. Ind. Appl., vol. 50, no. 3, pp. 1619–1629, Jun. 2014.a
 F. Z. Peng and J. S. Lai, “Generalized instantaneous reactive power theory for three-phase power systems,” IEEE Trans. Instrum. Meas., vol. 45, no. 1, pp. 293–297, Feb. 1996.
 L. K. Haw, M. S. Dahidah, and H. A. F. Almurib, “A new reactive current reference algorithm for the STATCOM system based on cascaded multilevel inverters,” IEEE Trans. Power Electron., vol. 30, no. 7, pp. 3577–3588, Jul. 2015.
The paper evolves a mechanism for improving the input power factor of an AC-DC-DC conversion system. It involves the process of shaping the input current wave to phase align with the input supply through a process of error compensation. The methodology includes cohesive formulation to arrive at nearly unity power factor and enjoy the etiquettes of output voltage regulation. The theory assuages to subscribe the benefits for the entire range of operating loads. It eliminates the use of passive components and fortifies the principles of pulse width modulation (PWM) for realizing the change in duty cycle. The MA TLAB based simulation results arbitrate the viability of the proposed approach and exhibit its suitability for use in real world applications.
- Ac-dc converter
- Power factor
- Voltage regulation
Figure 1. Power Factor Correction Control of Boost Converter
EXPECTED SIMULATION RESULTS:
Figure 2. Steady State Input AC Voltage and Input AC Current Waveform
Figure 3. Steady State Rectified DC Voltage and Rectified DC Current Waveform
Figure 4. Steady State Regulated DC Output Voltage and Regulated DC Output Current Waveform
Figure 5. Power Factor Measurement of the Proposed Power Factor Correction Boost Converter
Figure 6. FFT Spectrum of the AC input current of Proposed Power Factor Correction Boost Converter
Figure 7. Transient response of Input AC Voltage and Input AC Current Waveform
Figure 8. Transient Response of Rectified DC Voltage and Rectified DC Current Waveform
Figure 9. Transient Response of Regulated DC Output Voltage and Regulated DC Output Current Waveform
Figure 10. Power Factor Measurement of the Proposed Power Factor Correction Boost Converter at transient condition
A single stage power factor correction strategy has been proposed for full bridge diode rectifier fed boost converter to support a 400W, lA DC load. The suitability of boost converter for power factor correction has been illustrated by the elimination of input capacitor filter and low output ripple factor. The formulated control design has been effectively orchestrated to correct the power factor in addition providing good voltage regulation. The transient performance has been portrayed to up-heave the strength of the control structure with an adequate output regulation and effective harmonic elimination. The control plan has been nurtured to standardize the THD level of the system that prevents the adverse effects of harmonics being injected in the grid. The exclusion of additional passive components and interleaving configuration has been fostered to reduce the size thus making it more adaptive to low cost compact electronic applications with high standards .
 M. Milanovic, F . Mihalic, K. Jezernik and U. Milutinovic,” Single phase unity power factor correction circuits with coupled inductance,” Power Electronics Specialists Conference, 1992, vol.2, pp. l077-1082.
 M. Orabi and T Ninomiya, “Novel nonlinear representation for two stage power-factor-correction converter instability,” IEEE International Symposium on Industrial Electronics, 2003, voU, pp- 270-274.
 Yu Hung, Dan Chen, Chun-Shih Huang and Fu-Sheng Tsai, “Pulse-skipping power factor correction control schemes for ACIDC power converters,” Fourth International Conference on Power Engineering, Energy and Electrical Drives (POWERENG), 2013, pp-I087-1092.
 Lu, D.D. -C, H.H.-C. lu, V. Pjevalica, “A Single-Stage AC/DC Converter With High Power Factor, Regulated Bus Voltage, and Output Voltage,” Power Electronics, IEEE Transactions on, vo1.23, issue. I, pp. 218-228, Jan. 2008.
 M. Narimani and G. Moschopoulos, “A New Single-Phase SingleStage Three-Level Power Factor Correction AC-DC Converter,” Power Electronics, IEEE Transactions on , vol.27, issue.6, pp. 2888- 2899, June. 2012.
The aim of this study is to present a new structure for switched-capacitor multilevel inverters (SCMLIs) which can generate a great number of voltage levels with optimum number of components for both symmetric and asymmetric value of dc voltage sources. Proposed topology consists of a new switched-capacitor dc/dc converter (SCC) which has boost ability and can charge capacitors as self-balancing by using proposed binary asymmetrical algorithm and series-parallel conversion of power supply. Proposed SCC unit is used in new configuration as a sub-multilevel inverter (SMLI) and then, these proposed SMLIs are cascaded together and create a new cascaded multilevel inverter topology which is able to increase the number of output voltage levels remarkably without using any full H-bridge cell and also can pass the reverse current for inductive loads. In this case, two half bridges modules besides two additional switches are employed in each of SMLI units instead of using a full H-bridge cell which contribute to reduce the number of involved components in the current path, value of blocked voltage, the variety of isolated dc voltage sources and as a result the overall cost by less number of switches in comparison with other presented topologies. The validity of the proposed SCMLI has been carried out by several simulation and experimental results.
- Cascade sub-multilevel inverter
- Series-parallel conversion
- Self-charge balancing
Fig. 1. Proposed 17-level structure
EXPECTED SIMULATION RESULTS
Fig. 2. Steady states output voltage and current waveforms (a) in simulation Fig. 12. Transient states of output waveforms in simulation (b) in experiment ( 250V/div& 2A/div)
Fig. 3. Transient states of output waveforms in simulation
- (a) (b)
Fig. 4. Harmonic orders (a) output voltage (b) output current in simulation
Fig. 5. Observed output voltage waveform at no-load condition (250V/div)
Fig. 6. Capacitors’ voltage ripple waveforms for first case study (a) in simulation (b) in experiment (25 V/dev&50V/div)
Fig. 7. Blocked voltage waveforms across switches of S1 (25V/div), S2 (100V/div), T1 (50V/div), T2 and T3 (100V/div) from left to right in the experiment
Fig. 8. Output voltage and current waveforms for (a) inductive load in experiment (250 V/div & 2 A/div) (b) sudden step load in simulation
Fig. 9. Observed capacitors’ current (a) in simulation (b) in experiment (2A/div)
Fig. 10. (a) laboratory prototype (b) Output 49-level voltage and current waveforms in the experiment (250V/div & 2A/div)
Fig. 11. Across voltage waveforms of capacitors in upper and lower stages of SCCs in proposed 49-level inverter (a) v C 1 lower stage (5V/div) (b) v C 2 lower stage (10V/div) (c) v C 1 upper stage(25V/div) (d) v C 2 upper stage(50V/div)
In this paper, at the first, a new reduced components SCC topology was presented which has boost capability remarkably and also can pass the reverse current for inductive loads through existing power switches. The voltage of all capacitors in this structure is balanced by binary asymmetrical algorithm. Next, a new sub-multilevel structure based on suggested SCC was proposed which can generate all of the voltage levels at the output (even and odd). In this case, the conventional output H-bridge cell used to convert the polarity of SCC units, has been removed, therefore number of required IGBTs and other involved components, are decreased. After that, an optimizing operation was presented which could obvious the number of required capacitors in each of SCC units that participate in the cascade sub-multilevel inverter (CSMLI) to generate maximum number of output voltage levels with less number of elements. Moreover comprehensive comparisons were given which prove the differences between improved symmetric and asymmetric CSMLIs in contrast to some of recently presented topologies in variety aspects. Finally, to confirm the performance and effectiveness of proposed CSMLI, several simulation and experimental results have been presented.
 J. Chavarria, D. Biel, F. Guinjoan, C. Meza, and J. J. Negroni, “Energy balance control of PV cascaded multilevel grid-connected inverters under level-shifted and phase-shifted PWMs,” IEEE Trans. Ind. Electron. vol. 60, no. 1, pp. 98–111, Jan. 2013.
 G. Buticchi, E. Lorenzani, and G. Franceschini, “A five-level single-phase grid-connected converter for renewable distributed systems,” IEEE Trans. Ind. Electron., vol. 60, no. 3, pp. 906–918, Mar. 2013.
 J. Rodriguez, L. J.Sheng, and P. Fang Zheng, “Multilevel inverters: A survey of topologies, controls, and applications,” IEEE Trans. Ind Electron., vol. 49, no. 4, pp. 724–738, Aug. 2002.
 L. G. Franquelo, J. Rodriguez, J. I. Leon, S. Kouro, R. Portillo, and M. A. M. Prats, “The age of multilevel converters arrives,” IEEE Trans. Industrial Electronic Magazine, vol. 2, no. 2, pp. 28–39, Jun. 2008.
 M. M. Renge and H. M. Suryawanshi, “Five-Level Diode Clamped Inverter to Eliminate Common Mode Voltage and Reduce dv/dt in Medium Voltage Rating Induction Motor Drives,” IEEE Trans. Power Electron., vol. 23, no. 4, pp. 1598-1607, Jul. 2008.
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%.
1. Pulse width modulator
2. Sliding mode control
3. Unipolar single phase inverter
Fig. 1. Proposed controller for single-phase inverters with a resonator in voltage loop.
EXPECTED SIMULATION RESULTS:
Fig. 2. Simulation result. a) Output voltage and current at 6-kW linear load. b) Output voltage and current at 6-kVA nonlinear load with CF = 2.75 and PF = +0.7.
Fig. 3. Simulation result: transient response of the output voltage for linear step load from zero to 100%
Fig. 4. Simulation result: transient response of the output voltage for linear
step load from 100% to zero.
Fig. 5. Experimental result: efficiency of inverter versus output power.
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%.
 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.
 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.
 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.
 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.
 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.