Modeling and control of cascaded h bridge multilevel inverter ijaerdv05i0238178

Scientific Journal of Impact Factor (SJIF): 5.71

e-ISSN (O): 2348-4470 p-ISSN (P): 2348-6406

International Journal of Advance Engineering and Research Development Volume 5, Issue 02, February -2018

Modeling and Control of Cascaded H-Bridge Multilevel Inverter MULUGURI SIVAKUMAR1, RAMMOHANARAO M2 1

PG Scholar, Dept. of EEE, Sri Mittapalli College of Engineering, Tummalapalem, Guntur (Dt), AP, India, Associate Prof, Dept. of EEE, Sri Mittapalli College of Engineering, Tummalapalem, Guntur (Dt), AP, India,

2

Abstract - The scope of the output power is an imperative and obvious restriction of two-level inverters. To defeat this drawback, multilevel inverters are presented. As of late, Cascade H-Bridge inverters have raised as one of the prevalent converter topologies utilized as a part of various mechanical applications. In this paper we have examined about a specific condition that the RMS estimation of the inverter yield voltage varies with certain frequency and adequacy. This paper exhibits the use of this unique outputting cascaded H-bridge (CHB) multilevel converter, grid connected wind turbine converter testing. In this paper, by contrasting and the other control techniques new control methodology is proposed which is basic and successful and furthermore the demonstrating and examination of this specific RMS esteem criticism control system is explained. Reproduction work is finished utilizing the MATLAB programming and trial comes about have been displayed to approve the hypothesis.

Keywords: cascaded H-bridge (CHB) multilevel converter, two-level inverter, RMS estimation, multilevel inverter.

1. Introduction Presently a dayâ€&#x;s modern applications needs higher power rating which came to umber watt run. For a medium voltage grid.

It is troublesome to associate just a single power semiconductor switch specifically. Thus, multilevel power converter structure has been presented as an option in high power and medium voltage applications. A multilevel converter accomplishes high power appraisals, as well as empowers the utilization of sustainable power sources, for example, photovoltaic, wind, and power devices can be effectively interfaced to a multilevel converter framework for medium voltage high power drives, conveyed vitality sources and half and half electric vehicles. The scope of yield control is restricted in two level inverters, this impediment is overwhelmed by multilevel inverter and they have highlights, for example, high unwavering quality because of its particular topology, less misshaped input present and less exchanging misfortunes. Among the topologies of multilevel inverter Cascade Multilevel Inverter (CMIL) is a standout amongst the most essential topology on account of following highlights, for example, no uncommonly planned transformer is required when contrasted with multi heartbeat inverter, involves less space and capacity to incorporate better consonant range. With the preferences over other multilevel converters, for example, nonpartisan point clasped converter and flying capacitor converter, CHB multilevel converters are playing a more huge part in control converter family for high-power, high-voltage applications because of relatively ease, no requirement for various capacitors and diodes, simplicity of control, astounding performance and ability of fault tolerant. The real uses of the CHB multilevel converter are VAR pay, center voltage variable speed drive and consecutive framework. Numerous specialists have added to the examination of CHB multilevel converters. These days, sustainable power source frameworks are experiencing a vital advancement. Among them wind vitality emerges for its introduced limit, control age enduring development. In this paper in view of CHB structure wind turbine testing framework control technique is examined. A network associated wind turbine converter testing framework. Is developed through the blend of CHB multilevel converter, three-stage PWM converter and transformers as portrayed in Fig.1. Keeping in mind the end goal to mimic a 35 kV-control framework and deliver a fluctuating voltage whose RMS esteem changes with certain frequency and sufficiency, the control of CHB multilevel inverter ought to be scrupulously composed given that the DCbridge voltage is perpetual and each stage is controlled independently as a solitary stage inverter. The mix of three singlestage CHB multilevel inverters builds a three-stage framework in which each and every CHB multilevel inverter fills in as a solitary stage inverter. As a result to this announcement, the control system of single-stage inverter can be considered as reference for CHB multilevel converter control. Numerous control plans have been proposed amid past decades for singlestage inverters;however those control methodologies realize downsides, for example, trouble in displaying, complex outline and equipment usage, delicate to framework parameters and stacking conditions, or basically consistent state mistakes. Also, larger part of these control procedures normally just worry about the specific sorts of burdens which contracts the extent of the advantage found. In light of the controller structure, applying a solitary voltage controller is sufficient for the control of single-stage inverter AC voltage, yet this isn't sufficient when managing all the more requesting applications with higher performance necessities, where more often than not no less than one current-circle is required too. Multihop current-voltage PID control procedure can speaks to a basic arrangement when planned utilizing frequency reaction systems giving various

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International Journal of Advance Engineering and Research Development (IJAERD) Volume 5, Issue 02, February-2018, e-ISSN: 2348 - 4470, print-ISSN: 2348-6406 points of interest as far as outline and simplicity of usage, at last accomplishing great direction and an all around characterized district of unsurprising strength for the converter activity. These multiloop PID conspires for the most part utilize either filter inductor or filter capacitorpresent as criticism factors, or a more mind boggling structure, both filter inductor current and load present as input factors. The bad mark of this control is that it is liable to relentless state mistakes because of its limited circle pick up at central frequency, and furthermore that it has a variable dynamic reaction relying upon the stacking conditions. To conquer these inadequacies, a few control plans have been proposed including adding proportional plus resonant (PR) or PID plus resonant (PID+R) compensator into the external voltage direction circleor utilizing single-phase d-q outline controls with orthogonal stationary β-pivot termsthe inverter can hypothetically accomplish zero unfaltering state mistake and quick unique reaction separately. The correlation of these multiloop controls is given. Be that as it may, these prompt inconveniency in useful applications due to the accompanying reasons: 1) Inferable from the variety of the fluctuating frequency, parameter of the thunderous compensator is difficult to pick; 2) Since the PR or PID+R compensator is dependably nonideal, zero steady statemistakes can't be accomplished by and by; 3) In view of the powerful appraising and high voltage, the controller parameter configuration ought to be basic and solid; 4) Current sensors with high evaluations and wide data transfer capacity must be utilized which, much of the time, makes these multiloop controls financially ugly; 5) Likewise, trouble in demonstrating, complex plan and delicate to framework parameters and load conditions. This paper thoroughly explores dissimilar multiloop controls for single-stage inverters and presents an exceptional RMS input control without breaking a sweat of performance and astounding performance. The trial confirmation of the control methodology is done in the 35 kv-6 mw wind turbine converter testing hardware.

Fig. 1 Main circuit topology of the wind turbine lowfrequencydisturbance testing system 2. Proposed Topology The modulation control systems for multi level inverters can be ordered by exchanging frequency. Tweak methods which have numerous compensations for the semi conductors in a single time of the basic yield voltage have high exchanging frequency. Extremely famous techniques in mechanical application are transporter based PWM with triangular bearers, they are: stage moved bearer based and level moved transporter based PWM plans. Regulation control procedures that work with low exchanging frequency by and large perform maybe a couple substitutions of the power semi conductors amid one cycle of the yield voltage. Creating stair case wave frame. For this low exchanging frequency, mainstream control strategy is particular symphonious disposal pwm technique.

A. PSC-PWM CHB Multilevel Converter: The stage moved transporter PWM (PSCPWM) is a broadly used balance system for CHB multilevel converter because of its low THD, great linearity and wide data transfer capacity. In any case, since the PSC-PWM has unique sorts of varieties, the performance separates from each other, for example, extraordinary stage moved edge, different balances for each and every H-bridge (two-level balance and three level tweak). Some of these are just direct varieties of past methodologies, while others make contrasts in natural rule. In psc pwm all the triangular transporters have a similar frequency and same pinnacle top sufficiency .yet there is a stage move between any two nearby

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International Journal of Advance Engineering and Research Development (IJAERD) Volume 5, Issue 02, February-2018, e-ISSN: 2348 - 4470, print-ISSN: 2348-6406 bearer waves. For m Voltage levels (m-1) transporter signals are required and they are stage moved with a point of θ=(360°/m-1). The entryway signals are created with legitimate correlation of bearer wave and balancing signal . This paper applies a particular PSC-PWM, in which each and every H-bridge utilizes twofold frequency balance, or purported threelevel regulation. In this way, the yield voltage of the CHB multilevel inverter has 2n + 1 levels and the proportional exchanging frequency is 2nk (n is the quantity of the cascaded H-spans, k is H-bridge bearer frequency). Note that for examination reason, the CHB multilevel inverter can be fused inside the control circle as a settled pick up factor which equivalents to n times of the modulation record, gave that the exchanging frequency is significantly higher than the required yield frequency and the inverter isn't working in over modulation local.

B.Multi loop V-I Control:Multiloop current-voltage control is the most predominant control conspires because of its simplicity of performance and great performance. Fig. 2 and Fig. 3 are the previously mentioned control conspires that are broadly used. These controls are the advancement of multiloop PID controls has said previously. Fig. 2 demonstrates the filter capacitor current criticism control including PR or PID+R compensator into the voltage direction circle. At the point when financial effectiveness is contemplated, this control is the best decision for Uninterruptible Power Supply (UPS) with acceptable relentless state and transient performance, since it requires just a single current estimation with a generally ease current sensor. Nonetheless, this plan can't fuse inverter over current security since the inverter yield current isn't accessible to actualize an over current fault.

Figure 2. Filter capacitor current feedback control

Figure 3. Filter inductor current feedback control (oradding load current feedback control) Fig. 3 demonstrates the filter inductor current input control including PR or PID+R compensator into the voltage direction circle. This permits over current insurance to be effortlessly added to the control hardware. The estimation of inductor current

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International Journal of Advance Engineering and Research Development (IJAERD) Volume 5, Issue 02, February-2018, e-ISSN: 2348 - 4470, print-ISSN: 2348-6406 however requires the utilization of current sensors with a higher rating and more extensive transfer speed, since the inductor current contains the vast majority of the sounds drawn by the heap. Besides, the transient performance of the control framework will be bargained because of similarly little bandwidth and bring down low-frequency circle pick up. Besides, by including load current input (not all that called Feed forward) into the criticism circle which is likewise portrayed in Fig. 3, it accomplishes the performance advantage of thefilter permitting inverter over current security to be actualized. Note that this sort of control is the most costly one since it needs two elite current sensors for each stage estimating burden and inductor current. Also, it can be watched how the LCF assists diminish the voltage blunder because of the low-frequency circle pick up change, particularly under overwhelming stacking condition. Besides, thePID+R including burden and inductor criticism controller displays the most elevated transmission capacity and circle pick up which brings about little unfaltering state blunder and best powerful reaction. All things considered, with the data transmission and circle increase expanded contrasting and the customary multiloop PI control; these controls experience the ill effects of precariousness with second request loads, for example, LC filter loads. C.Proposed Control Scheme From the proposed control conspire, the breeze turbine fills in as a present source stack maneuvering and nourishing force into the testing equipment or the power framework, the RMS input control is a superior decision for simplicity of control parameters plan, exact yield plentifulness, and substantial steadiness edge (Fig. 4). Control graphs are portrayed in Fig. 6 and Fig. 7.

Figure 4. RMS feedback voltage control (addingsinusoidal signal in the instantaneous inner-loop) Where, Vdistrub - fluctuating signal A- Amplitude - Angular frequency And φ- Phaseof the modulated sinusoidal signal respectively.

It can be watched clearly that Vdistrub has three frequency parts, they are central segment and two segments that appropriate symmetrically separated from the major frequency by which is the fluctuating frequency.

Figure 5. RMS feedback voltage control (addingperturbation signal in the instantaneous inner-loop) As indicated by the regular RMS criticism control, the instantaneous inward circle reference flag is the thing that requirements to be produced. At the point when basically supplanting the sinusoidal reference by this fluctuating sign (Fig. 5), the exactness of the fluctuating yield will be weakened for the accompanying reason: the external circle reference is a consistent esteem, while the criticism is the sliding window RMS of the fluctuating voltage which varies too, in this manner the reference and the input can never coordinate. Fig. 8 demonstrates the proposed control scheme.

Unlike the traditional control, the reference of the external circle is the sliding window RMS estimation of the annoyance flag. Note that the inward circle utilizes a P controller for the sake of forestalling single-side basic immersion which prompts transformer attractive biasing.

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International Journal of Advance Engineering and Research Development (IJAERD) Volume 5, Issue 02, February-2018, e-ISSN: 2348 - 4470, print-ISSN: 2348-6406

Figure 6. Control diagram of instantaneous inner loop

Figure 7. Control diagram of RMS outer-loop

Figure 8. Proposed control scheme 3. Simulation Results

Figure 9(a). Detailed Switching Model for The Sample System Built Using Simulink

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International Journal of Advance Engineering and Research Development (IJAERD) Volume 5, Issue 02, February-2018, e-ISSN: 2348 - 4470, print-ISSN: 2348-6406

figure 9(b). Dynamic Response ofTheDeveloped Dynamic Model of The Active(P)&Reactive Power(Q)

Figure 10(a). Proposed Modeling & Control of Multilevel Inverter System Built Using Simulink

figure 10(b). Proposed System of Active (P) & ReactivePower (Q).MATLAB-Simulink reproductions of the control methodology of cascaded H-Bridge multilevel converter framework were performed. This paper shows an enhanced RMS feedback control which is appropriate for this breeze turbine converter testing framework is mimicked. The testing hardware topology is appeared in Fig. 1, and the framework parameters are as per the following, LC Filter: L = 100 ยนH, C = 90 ยนF; bearer frequency: 2 kHz, DC-interface voltage: 1000 V. For wellbeing in this high-power and high-voltage application, voltage waveform information is gathered by Fluke-1760 and is investigated by MATLAB (FFT examination). In Fig. 11 and Fig. 12, the objective fluctuating frequency is 10 Hz and fluctuating sufficiency is 10% of the crucial voltage. Clearly the trial result under the proposed control is indistinguishable to the numerical articulation in (2), while the annoyance parts under the customary control surpass their hypothetical esteem. Fig. 13 and Fig. 14are the yield voltages with a fluctuating frequency

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International Journal of Advance Engineering and Research Development (IJAERD) Volume 5, Issue 02, February-2018, e-ISSN: 2348 - 4470, print-ISSN: 2348-6406 and adequacy of 10%, 12 Hz and 9%, 1 Hz. It can be watched that the voltage waveform is all around managed which is indistinguishable to the hypothetical inference comes about.

Figure 11. Spectrum of the output voltage (10%-12Hz)

Figure 12. Spectrum of the output voltage (9%-1Hz)

Figure 13. Fluctuating output voltage (10%-12Hz)

Figure 14. Fluctuating output voltage (9%-1Hz)

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International Journal of Advance Engineering and Research Development (IJAERD) Volume 5, Issue 02, February-2018, e-ISSN: 2348 - 4470, print-ISSN: 2348-6406 4. Conclusion This paper introduces an improved RMS feedback control which is appropriate for this breeze turbine converter testing framework. The internal circle P controller inalienably prompts relentless state mistake however free of stage slack, the RMS outer-loop guarantees the amplitude accuracy of the demand.. In this way, it progressively accomplishes the control point. All the hypothetical discoveries are approved tentatively in the 35 kv-6 mw wind turbine converter testing equipment.

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About Authors: Muluguri Sivakumar is currently pursuing his M.Tech (EEE) in Power Electronics and Electrical Drives from Sri Mittapalli college of Engineering, Tummalapalem, Guntur, A.P, India. He received his B.Tech in Electrical & Electronics Engineering Department from Sri Mittapalli college of Engineering, Tummapalem, Guntur (Dt), AP, India.

RAMMOHANARAO M is Assistant Professor at Sri Mittapalli college of Engineering, Tummalapalem, Guntur, AP, India. Completed B-Tech in Electrical & Electronics engineering in 2006 from A.I.E.T, Vizag Affiliated to JNTUH, HYDERABAD and M-Tech in Power Electronics in 2012 from SVEC, Thadepalligudem Affiliated to JNTUK, KAKINADA

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