A Novel Nine-Level Inverter Employing One Voltage Source and Reduced Components as High Frequency AC Power Source

 ABSTRACT:

Increasing demands for power supplies have contributed to the population of high frequency ac (HFAC) power distribution system (PDS), and in order to increase the power capacity, multilevel inverters (MLIs) frequently serving as the high-frequency (HF) source-stage have obtained a prominent development. Existing MLIs commonly use more than one voltage source or a great number of power devices to enlarge the level numbers, and HF modulation (HFM) methods are usually adopted to decrease the total harmonic distortion (THD). All of these have increased the complexity and decreased the efficiency for the conversion from dc to HF ac. In this paper, a nine-level inverter employing only one input source and fewer components is proposed for HFAC PDS. It makes full use of the conversion of series and parallel connections of one voltage source and two capacitors to realize nine output levels, thus lower THD can be obtained without HFM methods. The voltage stress on power devices is relatively relieved, which has broadened its range of applications as well. Moreover, proposed nine-level inverter is equipped with the inherent self-voltage balancing ability, thus the modulation algorithm gets simplified. The circuit structure, modulation method, capacitor calculation, loss analysis and performance comparisons are presented in this paper, and all the superior performances of proposed nine-level inverter are verified by simulation and experimental prototypes with rated output power of 200W. The accordance of theoretical analysis, simulation and experimental results confirms the feasibility of proposed nine-level inverter.

 

KEYWORDS:

1.      Nine-level inverter

2.      One voltage source

3.      Two capacitors

4.      Self-voltage balancing

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Circuit of proposed nine-level inverter.

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation waveforms of driving signals.

Fig. 3. Simulation waveforms of output voltages and currents under different load-types. (a) Ro = 32 . (b) ZL = 24+j20 Ro =24 Lo = 3.2 mHL31.2= 40.

Fig. 4. Simulation waveforms of the staircase output and capacitors’ voltages.

Fig. 5. Simulation waveform of frequency spectrum at fundamental frequency of 1 kHz.

CONCLUSION:

 In this paper, a novel nine-level inverter is proposed for HFAC PDS. Compared with the existing topologies, proposed topology can achieve nine-level staircase output with only one voltage source, fewer power devices and relatively less voltage stress. All these have enlarged its application scopes. Voltage balance problem is avoided by the inherent self-voltage balancing ability, which has simplified the modulation circuits or algorithms, and the lower THD of 3.13% is realized without using HFM methods. As a result, the switching loss is significantly reduced. The capacitor calculation and power loss analysis are conducted in this paper, and the comparisons with existing topologies further testify the superiority of proposed HF inverter. All the merits and the feasibility of proposed topology are evaluated by a simulation model and an experimental prototype with rate power of 200W, and their results illustrate that proposed inverter is a preferable topology to implement HF power source for HFAC PDS.

REFERENCES:

[1] J. Drobnik, “High frequency alternating current power distribution,” Proceedings of IEEE INTELEC, pp. 292-296, 1994.

[2] P. Jain, H. Pinheiro, “Hybrid high frequency AC power distribution architecture for telecommunication systems,” IEEE Trans. Power Electron., vol. 4, no.3, Jan. 1999.

[3] B. K. Bose, M.-H. Kin and M. D. Kankam, “High frequency AC vs. DC

distribution system for next generation hybrid electric vehicle,” in Proc. IEEE Int. Conf. Ind. Electron., Control, Instrum, (IECON), Aug. 5-10, 1996, vol.2, pp. 706-712.

[4] S. Chakraborty and M. G. Simões, “Experimental Evaluation of Active Filtering in a Single-Phase High-Frequency AC Microgrid,” IEEE Trans. Energy Convers., vol. 24, no. 3, pp. 673-682, Sept. 2009.

[5] R. Strzelecki and G. Benysek, Power Electronics in Smart Electrical Energy Networks. London, U.K., Springer-Verlag, 2008.

 

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 rectifier

5.      Multilevel converter

6.      Power quality

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Proposed HPUC five-level buck PFC rectifier

 EXPECTED SIMULATION RESULTS:

Fig. 2. Experimental results of the proposed HPUC rectifier connected to 120V RMS AC grid and supplying two DC loads at 125V DC. a) Output DC voltages regulated at 125V with grid side synchronised voltage and current b) DC loads currents with grid side synchronised voltage and current c) 5-Level voltage waveform at the input of the HPUC rectifier d) RMS and THD values of the AC side synchronised voltage and current waveforms

 

 

Fig. 3. Test results during 200% increase in Load1 from 53_ to 160_

Fig. 4. Test results during 50% decrease in Load2 from 80_ to 40_

Fig. 5. Supply voltage variation while the output DC voltages are regulated at 125V as buck mode of operation.

 

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.

A Novel Multilevel DC/AC Inverter Based on Three-Level Half Bridge With Voltage Vector Selecting Algorithm

ABSTRACT:

A novel multilevel inverter based on a three-level half bridge is proposed for the DC/AC applications. For each power cell, only one DC power source is needed and five-level output AC voltage is realized. The inverter consists of two parts, the three-level half bridge, and the voltage vector selector, and each part consists of the four MOSFETs. Both positive and negative voltage levels are generated at the output, thus, no extra H bridges are needed. The switches of the three-level half bridge are connected in series, and the output voltages are (Vo, Vo/2, and 0). The voltage vector selector is used to output minus voltages (􀀀Vo and 􀀀Vo/2) by different conducting states. With complementary working models, the voltages of the two input capacitors are balanced. Besides, the power cell is able to be cascaded for more voltage levels and for higher power purpose. The control algorithm and two output strategies adopted in the proposed inverter are introduced, and the effectiveness is verified by simulation and experimental results.

KEYWORDS:

1.      Bridge circuits

2.      DC-AC power converters

3.      Modular multilevel converters

4.      Pulse width modulation converters

5.      Voltage control

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 

Figure 1. The proposed hybrid ZVS bidirectional DC/AC inverter topology.

 EXPECTED SIMULATION RESULTS:

Figure 2. Waveforms with LFF strategy.

Figure 3. Waveforms with HFSPWM strategy.

Figure 4. Voltages of input capacitors C1 and C2.

Figure 5. Output waveforms of 2-level cascaded topologies.

 CONCLUSION:

 A novel multilevel inverter based on a three-level half bridge is proposed for DC/AC applications in this paper. For each power cell, only one DC power source is needed and 5-level output AC voltage is realized. Both positive and negative voltage levels are generated at the output, thus no extra H bridges are needed. The non-isolated topology (transformerless) eliminates magnetic losses. The operating principle and the working stages of the proposed inverter are introduced, while the two output strategies are discussed in detail. Besides, voltage balance strategy is adopted to balance the bus capacitor voltages, and stage optimization method is applied to further reduce the switching losses. Finally, a simulation is carried out to verify the two output strategies, voltage balance strategy and the cascaded ability, and a laboratorial experiment is carried out to test the THD losses and the total efficiency.

REFERENCES:

[1] A. Jahid, M. K. H. Monju, M. E. Hossain, and M. F. Hossain, ``Renewable energy assisted cost aware sustainable off-grid base stations with energy cooperation,'' IEEE Access, vol. 6, pp. 60900_60920, Oct. 2018.

[2] S. Xie, W. Zhong, K. Xie, R. Yu, and Y. Zhang, ``Fair energy scheduling for vehicle-to-grid networks using adaptive dynamic programming,'' IEEE Trans. Neural Netw. Learn. Syst., vol. 27, no. 8, pp. 1697_1707, Aug. 2016.

[3] A. Garcia-Bediaga, I. Villar, A. Rujas, and L. Mir, ``DAB modulation schema with extended ZVS region for applications with wide input/output voltage,'' IET Power Electron., vol. 11, no. 13, pp. 2109_2116, Nov. 2018.

[4] G. Xu, D. Sha, Y. Xu, and X. Liao, ``Hybrid-bridge-based DAB converter with voltage match control for wide voltage conversion gain application,'' IEEE Trans. Power Electron., vol. 33, no. 2, pp. 1378_1388, Feb. 2017.

[5] Y. Cho, W. Cha, J. Kwon, and B. Kwon, ``High-efficiency bidirectional DAB inverter using a novel hybrid modulation for stand-alone power generating system with low input voltage,'' IEEE Trans. Power Electron., vol. 31, no. 6, pp. 4138_4147, Jun. 2015.

A Novel Control Strategy for a Variable-Speed Wind Turbine With a Permanent-Magnet Synchronous Generator

 ABSTRACT:

This paper presents a novel control strategy for the operation of a direct-drive permanent-magnet synchronous generator- based stand-alone variable-speed wind turbine. The control strategy for the generator-side converter with maximum power extraction is presented. The stand-alone control is featured with output voltage and frequency controller that is capable of handling variable load. The potential excess of power is dissipated in the dump-load resistor with the chopper control, and the dc-link voltage is maintained. Dynamic representation of dc bus and small-signal analysis are presented. Simulation results show that the controllers can extract maximum power and regulate the voltage and frequency under varying wind and load conditions. The controller shows very good dynamic and steady-state performance.

KEYWORDS:

1.      Maximum power extraction

2.      Permanent magnet synchronous generator (PMSG)

3.       Switch-mode rectifier 

4.      Variable-speed wind turbine

5.      Voltage and frequency control

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Control structure of a PMSG-based stand-alone variable-speed wind turbine.

 

EXPECTED SIMULATION RESULTS:

Fig. 2. Response of the system for a step change of wind speed from 10 to 12 to 9 to 10 m/s. (a) Wind speed. (b) Generator speed. (c) Turbine torque and torque reference. (d) Torque reference and generator electromagnetic torque. (e) DC current reference and dc current. (f) DC power output.

Fig. 3. Optimum torque and generator torque.

Fig. 4. Turbine mechanical input power and electrical output power.

 Fig. 5. Instantaneous and rms voltage and currents at a constant load (full load). (a) Instantaneous load voltages. (b) RMS line voltage. (c) Instantaneous line currents. (d) RMS line current.

 

Fig. 6. DC-link voltage, rms load voltage, rms line current, frequency, and modulation index at a constant load (full load). (a) DC-link voltage. (b) RMS  load voltage (L–L). (c) RMS load current. (d) Frequency. (e)Modulation index.

 Fig. 7. Instantaneous and rms voltage and current responses when the load changes from 100% to 50% and from 50% to 100%. (a) Instantaneous load voltages. (b) RMS line voltage. (c) Instantaneous line currents. (d) RMS line current.

 

Fig. 8. Response of dc-link voltage, rms load voltage, rms line current, frequency, and modulation index when the load changes from 100% to 50% and from 50% to 100%. (a) DC-link voltage. (b) RMS load voltage (L–L). (c) RMS load current. (d) Frequency. (e) Modulation index.

 

CONCLUSION:

 

A control strategy for a direct-drive stand-alone variable speed wind turbine with a PMSG has been presented in this paper. A simple control strategy for the generator-side converter to extract maximum power is discussed and implemented using Simpower dynamic-system simulation software. The controller is capable of maximizing output of the variable-speed wind turbine under fluctuating wind. The load-side PWM inverter is controlled using vector-control scheme to maintain the amplitude and frequency of the inverter output voltage. It is seen that the controller can maintain the load voltage and frequency quite well at constant load and under varying load condition. The generating system with the proposed control strategy is suitable for a small-scale stand-alone variable-speed wind-turbine installation for remote-area power supply. The simulation results demonstrate that the controller works very well and shows very good dynamic and steady-state performance.

REFERENCES:

[1] S. Müller, M. Deicke, and R. W. De Doncker, “Doubly fed induction generator system for wind turbines,” IEEE Ind. Appl. Mag., vol. 8, no. 3, pp. 26–33, May 2002.

[2] H. Polinder, F. F. A. Van der Pijl, G. J. de Vilder, and P. J. Tavner, “Comparison of direct-drive and geared generator concepts for wind turbines,” IEEE Trans. Energy Convers., vol. 3, no. 21, pp. 725–733, Sep. 2006.

[3] T. F. Chan and L. L. Lai, “Permanent-magnet machines for distributed generation: A review,” in Proc. IEEE Power Eng. Annu. Meeting, 2007, pp. 1–6.

[4] M. De Broe, S. Drouilhet, and V. Gevorgian, “A peak power tracker for small wind turbines in battery charging applications,” IEEE Trans. Energy Convers., vol. 14, no. 4, pp. 1630–1635, Dec. 1999.

[5] R. Datta and V. T. Ranganathan, “A method of tracking the peak power points for a variable speed wind energy conversion system,” IEEE Trans. Energy Convers., vol. 18, no. 1, pp. 163–168, Mar. 1999.

A New Space Vector Pulse Width Modulated Transformer Less Single-Phase Unified Power Quality Conditioner

 ABSTRACT:

Emergence of solid-state switching devices, like thyristors, GTO’s, IGBT’s and etc, are widely used for controlling electric power in power electronic equipment for various purpose such as HVDC systems, computers etc. These devices draw disturbance in voltages and currents of both source side and distribution ends due to its non-linearity. This induce harmonics, reactive power, and excess neutral current cause the system to have less efficiency and reduction in power factor. In this paper transformer less single-phase unified power quality conditioner has been implemented to reduce the voltage and current distortions. The operation and control of single-phase transformer less three leg Unified power quality conditioner is investigated with the implementation of a new pulse width modulation method for solving the coupling problem introduced by common leg switches.

KEYWORDS:

1.      TL-UPQC

2.      SVPWM

3.      Harmonics

4.      Total harmonic distortion

5.      DSTACOM

6.      DVR

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Block Diagram for Harmonic Reduction Using UPQC.

EXPECTED SIMULATION RESULTS:

Fig. 2. DC- link Voltage Waveforms.

Fig. 3. Source Current Waveforms.

Fig. 4. % THD of Source Side Current.

Fig. 5. Switching pulses of Inverter.

Fig. 6. Waveform of Supply side, Load side Voltage and Distorted Voltage at Supply Side. 

Fig. 7. % THD of Distorted Voltage Waveform.

CONCLUSION:

 

The custom power devices such as DVR helps in compensation of voltage unbalances and DTATCOM helps in the elimination of current harmonics that are entering the circuit due to the presence of a non-linear load at the consumer side. By using a unified power quality conditioner both the issues such as compensation of voltage unbalances and elimination of current harmonics can be minimized. The replacement of the series transformer with a series inductance helps to overcome the issues of cost and weight of the system. The working principle and implementation of practical two-level space vector modulation has been shown. The special switching sequence incorporated in space vector modulation technique technique used here minimizes the coupling issues that occur in the common leg operation.

REFERENCES:

[1] A. Bendre, D. Divan, W. Kranz, W. Brumsickle, Equipment failures caused by power quality disturbances, in: Proc. IEEE IAS Annual Meeting, 2004, pp. 482– 489.

[2] I. Hunter, Power quality issues-a distribution company perspective, Power Eng. J., 15 (2) (Apr. 2001) 75–80.

[3] B. Singh, K. Al-Haddad, A. Chandra, A review of active filters for power quality improvement, IEEE Trans. Ind. Electron., 46 (5) (Oct. 1999) 960–971.

[4] P. Curtis, The fundamentals of power quality and their associated problems, IEEE Press, Wiley, 2007.

[5] M. El-Habrouk, M.K. Darwish, P. Mehta, Active power filters: a review, IEE Proc., Electr. Power Appl. 147 (5) (2000) 403, https://doi.org/10.1049/ipepa: 20000522.