A Bridge Modular Switched-Capacitor-Based Multilevel Inverter With Optimized SPWM Control Method And Enhanced Power-Decoupling Ability

ABSTRACT:

Micro-inverters operating into the single-phase grid from new energy source with low-voltage output face the challenges of efficiency bottleneck and twice-line-frequency variation. This paper proposed a multilevel inverter based on bridge modular switched-capacitor (BMSC) circuits with its superiority in conversion efficiency and power density. The topology is composed of DC-DC and DC-AC stages with independent control for each stage, aiming to improve system stability and simplify the control method. The BMSC DC-DC stage, which can be expanded to synthesize more levels, not only features multilevel voltage gain but also partially replaces the original bulk input capacitor and functions as an active energy buffer to enhance power decoupling ability between DC and AC sides. In DC-AC stage, the control strategy of optimized unipolar frequency doubling sine-wave pulse-width modulation (UFD-SPWM) is proposed to  improve the quality of output waveform. Meanwhile, the multilevel voltage phase has been optimized to reduce the power loss further. Finally, a prototype has been built and tested. Associated with the simulation, the experimental results validate the practicability of these analyses.

KEYWORDS:

  1. Switched-capacitor circuit
  2. Multilevel inverter
  3. Power decoupling
  4. Optimized unipolar frequency doubling SPWM.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

 

(a)

(b)

Fig.1 Topology of the proposed converter.(a) General topology of bridge  modular switched-capacitor-based multilevel inverter (b) Seven-level inverter.

EXPECTED SIMULATION RESULTS

(a)

                                                         (b)

(c)

Fig.2 Simulation waveforms of seven-level inverter.(a) Us1_DS, Us3_DS, Us1a_DS and Us2a_DS. (b) UC2a, Ud, UX, Uo and io. (c) Spectrum of Uo.

(a)

(b)

(c)

(d)

Fig.3 Simulation comparison of power decoupling ability at different Cin. Under proposed control strategy:(a)Ui and Po. (b)Ud and Po. Under conventional control strategy:(c) Ui and Po. (d) Ud and Po.

CONCLUSION:

A bridge modular switched-capacitor-based multilevel inverter with optimized UFD-SPWM control method is proposed in the paper. The switched-capacitor-based stage can obtain high conversion efficiency and multiple voltage levels. Meanwhile, it functions as an active energy buffer, enhancing the power decoupling ability and conducing to cut the total size of the twice-line energy buffering capacitance. Furthermore, voltage multi-level in DC-link reduces the switching loss of inversion stage because turn-off voltage stress of switches changes with phase of output voltage rather than always suffers from one relatively high DC voltage. Most importantly, the control method of UFD-SPWM, doubling equivalent witching frequency, is employed in the inversion stage for a high quality output waveform with reduced harmonic. In addition, the optimized voltage level phase maximizes the fundamental component in output voltage pulses to reduce harmonic backflow as possible. Hence, the comprehensive system efficiency has been promoted and up to peak value of 97.6%. Finally, two conversion stages are controlled independently for promoting reliability and decreasing complexity. In future work, detailed loss discussion, including theoretic calculation and validation of loss breakdown, will be presented.

REFERENCES:

[1] M. Jun, “A new selective loop bias mapping phase disposition PWM with dynamic voltage balance capability for modular multilevel converter,” IEEE Trans. Ind. Electron., vol. 61, no. 2, pp. 798-807, Feb. 2014.

[2] N. Mehdi, and G. Moschopoulos, “A novel single-stage multilevel type full-bridge converter,” IEEE Trans. Ind. Electron., vol. 60, no. 1, pp. 31-42, Jan. 2013.

[3] E. Ehsan and N. B. Mariun, “Experimental results of 47-level switchladder multilevel inverter,” IEEE Trans. Ind. Electron., vol. 60, no. 11, pp. 4960-4967, Nov. 2013.

[4] J. Lai, “Power conditioning circuit topologies,” IEEE Trans. Ind. Electron., vol. 3, no. 2, pp. 24-34, Jun. 2009.

[5] L. He, C. Cheng, “Flying-Capacitor-Clamped Five-Level Inverter Based on Switched-Capacitor Topology,” IEEE Trans. Ind. Electron., vol. 63, no.12, pp. 7814-7822, Sep. 2016.

 

 

 

 

Standalone Photovoltaic Water Pumping System Using Induction Motor Drive with Reduced Sensors

ABSTRACT

A simple and efficient solar photovoltaic (PV) water pumping system utilizing an induction motor drive (IMD) is presented in this paper. This solar PV water pumping system comprises of two stages of power conversion. The first stage extracts the maximum power from a solar PV array by controlling the duty ratio of a DC-DC boost converter. The DC bus voltage is maintained by the controlling the motor speed. This regulation helps in reduction of motor losses because of reduction in motor currents at higher voltage for same power injection. To control the duty ratio, an incremental conductance (INC) based maximum power point tracking (MPPT) control technique is utilized. A scalar controlled voltage source inverter (VSI) serves the purpose of operating an IMD. The stator frequency reference of IMD is generated by the proposed control scheme. The proposed system is modeled and its performance is simulated in detail. The scalar control eliminates the requirement of speed sensor/encoder. Precisely, the need of motor current sensor is also eliminated. Moreover, the dynamics are improved by an additional speed feedforward term in the control scheme. The proposed control scheme makes the system inherently immune to the pump’s constant variation. The prototype of PV powered IMD emulating the pump characteristics, is developed in the laboratory to examine the performance under different operating conditions.

 

KEYWORDS:

  1. Photovoltaic cells
  2. MPPT
  3. Water pumping
  4. Scalar control
  5. Induction motor drives

SOFTWARE:MATLAB/SIMULINK

 

SYSTEM ARCHITECTURE:

System architechure for the standalone solar water pumping system

Fig. 1 System architechure for the standalone solar water pumping system

  

EXPECTED SIMULATION RESULTS:

Fig.2 Starting performance of the proposed system

Steady state and transient behavior of proposed system

Fig.3 Steady state and transient behavior of proposed system

Influence of the wrong estimation of pump’s constant

Fig.4 Influence of the wrong estimation of pump’s constant

A brief cost estimation of the proposed solar water pumping system

Fig. 5 A brief cost estimation of the proposed solar water pumping system

 

CONCLUSION

The standalone photovoltaic water pumping system with reduced sensor, has been proposed. It utilizes only three sensors. The reference speed generation for V/f control scheme has been proposed based on the available power the regulating the active power at DC bus. The PWM frequency and pump affinity law have been used to control the speed of an induction motor drive. Its feasibility of operation has been verified through simulation and experimental validation. Various performance conditions such as starting, variation in radiation and steady state have been experimentally verified and found to be satisfactory. The main contribution of the proposed control scheme is that it is inherently, immune to the error in estimation of pump’s constant. The system tracks the MPP with acceptable tolerance even at varying radiation.

 

REFERENCES

  • Drury, T. Jenkin, D. Jordan, and R. Margolis, “Photovoltaic investment risk and uncertainty for residential customers,” IEEE J. Photovoltaics, vol. 4, no. 1, pp. 278–284, Jan. 2014.
  • Muljadi, “PV water pumping with a peak-power tracker using a simple six-step square-wave inverter,” IEEE Trans. on Ind. Appl., vol. 33, no. 3, pp. 714-721, May-Jun 1997.
  • Sharma, S. Kumar and B. Singh, “Solar array fed water pumping system using induction motor drive,” 1st IEEE Intern. Conf. on Power Electronics, Intelligent Control and Energy Systems (ICPEICES), Delhi, 2016.
  • Franklin, J. Cerqueira and E. de Santana, “Fuzzy and PI controllers in pumping water system using photovoltaic electric generation,” IEEE Trans. Latin America, vol. 12, no. 6, pp. 1049-1054, Sept. 2014.
  • Kumar and B. Singh, “BLDC Motor-Driven Solar PV Array-Fed Water Pumping System Employing Zeta Converter,” IEEE Trans. Ind. Appl., vol. 52, no. 3, pp. 2315-2322, May-June 2016.

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aThree-Phase Transformerless Shunt Active Power Filter with Reduced Switch Count for Harmonic Compensation in Grid-Connected Applications

ABSTRACT:

Shunt active power filter is the preeminent solution against nonlinear loads, current harmonics and power quality problems. APF topologies for harmonic compensation use numerous high-power rating components and are therefore disadvantageous. Hybrid topologies combining low-power rating APF with passive filters are used to reduce the power rating of voltage source inverter. Hybrid APF topologies for high-power rating systems use a transformer with large numbers of passive components. In this paper, a novel four-switch two-leg VSI topology for a three-phase SAPF is proposed for reducing the system cost and size. The proposed topology comprises a two-arm bridge structure, four switches, coupling inductors, and sets of LC PFs. The third leg of the three-phase VSI is removed by eliminating the set of power switching devices, thereby directly connecting the phase with the negative terminals of the dc-link capacitor. The proposed topology enhances the harmonic compensation capability and provides complete reactive power compensation compared with conventional APF topologies. The new experimental prototype is tested in the laboratory to verify the results in terms of total harmonic distortion, balanced supply current, and harmonic compensation, following the IEEE-519 standard.

KEYWORDS:

  1. Harmonics
  2. hybrid topology
  3. nonlinear load
  4. power quality (PQ)
  5. Transformerless inverter
  6. Grid-connected system

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Proposed transformerless APF system

EXPECTED SIMULATION RESULTS:

 Fig. 2. Steady state operation of the proposed SAPF a) Utility voltage (THDv=4%) b) Utility current (THDi=4.1%) c) Load current (THDi=30.1%) d) Compensating filter current.

Fig. 3. a) DC voltage (50V/div). b) Filter current (100A/div) at filter switched ON (t=0.15).

Fig. 4. Starting performance of the proposed SAPF. a) Utility voltage (THDv=4%) b) Utility current (THDi=4.1%) c) Load current (THDi=30.1%) d) Compensating current at switched ON.

Fig. 5. a) On-state and Off-state APF operations. b) Zoom image of utility line current (𝒊𝑺𝒂𝒃𝒄) at 5th and 7th order harmonics.

Fig. 6. Dynamic performance with the R-L load step-change waveforms of the proposed SAPF.

 CONCLUSION:

In this paper, a novel three-phase reduced switch count and transformer-less APF circuit, operating with the function of active filtering and enhanced reactive power compensation. The main point of the proposed APF circuit topology, which uses a two-leg bridge structure and only four IGBT power devices in the three-phase power converter. Compared with the other existing topologies, the elimination of the transformer and minimum active and passive component contributes to a significant reduction in the manufacturing cost, volumetric size and weight. The proposed APF system is more robust, efficient and stable to improve the feasibility and harmonic propagation of the power distribution system. A detail analysis of the both the active filter inverter and passive filter, including the reactive power capability and filtering characteristics has been presented. The series LC tuned PF at the 5th and 7th order harmonic frequencies improves the harmonic mitigation performance. However, the series ac coupling inductors can overcome the fixed reactive power compensation caused by the defined value of the LC filter. The control algorithm can ensure the regulated sinusoidal voltage, phase amplitude, and low THD in the power distribution system, along with dc-link voltage control. The experimental and simulation results have verified the feasibility of the proposed APF topology and its excellent performance in terms of both transient and steady states responses to compensate selectively either the reactive power compensation, as well as in damping out the current harmonic distortion. Furthermore, the proposed APF system based on transformerless and power switching device reduced count configuration could be used in extensive applications, such as the grid-connected power converters, grid interfaced distributed energy sources, and so on.

REFERENCES:

[1] S. D. Swain, P. K. Ray, and K. B. Mohanty, “Improvement of Power Quality Using a Robust Hybrid Series Active Power Filter,” IEEE Transactions on Power Electronics, vol. 32, pp. 3490-3498, 2017.

[2] A. Javadi, A. Hamadi, L. Woodward, and K. Al-Haddad, “Experimental Investigation on a Hybrid Series Active Power Compensator to Improve Power Quality of Typical Households,” IEEE Transactions on Industrial Electronics, vol. 63, pp. 4849-4859, 2016.

[3] W. U. Tareen, S. Mekhilef, M. Seyedmahmoudian, and B. Horan, “Active power filter (APF) for mitigation of power quality issues in grid integration of wind and photovoltaic energy conversion system,” Renewable and Sustainable Energy Reviews, vol. 70, pp. 635-655, 4// 2017.

[4] J. Solanki, N. Fröhleke, and J. Böcker, “Implementation of Hybrid Filter for 12-Pulse Thyristor Rectifier Supplying High-Current Variable-Voltage DC Load,” IEEE Transactions on Industrial Electronics, vol. 62, pp. 4691-4701, 2015.

[5] L. Asiminoaei, C. Lascu, F. Blaabjerg, and I. Boldea, “Performance Improvement of Shunt Active Power Filter With Dual Parallel Topology,” IEEE Transactions on Power Electronics, vol. 22, pp. 247-259, 2007.

Intelligent Maximum Power Tracking and Inverter Hysteresis Current Control of Grid-connected PV Systems

 ABSTRACT:

This paper proposes a maximum power point tracking scheme using neural networks for a grid connected photovoltaic system. The system is composed of a photovoltaic array, a boost converter, a three phase inverter and grid. The neural network proposed can predict the required terminal voltage of the array in order to obtain maximum power. The duty cycle is calculated and the boost converter switches are controlled. Hysteresis current technique is applied on the three phase inverter so that the output voltage of the converter remains constant at any required set point. The complete system is simulated using MATLAB/SIMULINK software under sudden weather conditions changes. Results show accurate and fast response of the converter and inverter control and which leads to fast maximum power point tracking.

 

KEYWORDS:

  1. Neural networks
  2. Grid connected
  3. Maximum power point tracking
  4. Photovoltaic system
  5. Hysteresis control.

 

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Block diagram of the grid connected photovoltaic system

 

EXPECTED SIMULATION RESULTS:

 

Fig. 2. Power-voltage curves for the two cases

Fig. 3. (a) Temperature, (b) Irradiance, (c) Output power of the array, (d)Terminal voltage of the array.

Fig. 4. (a) Reference voltage of inverter control, (b) Voltage at inverter’s DC side.

 

CONCLUSION:

This paper presents a complete control scheme for a grid connected photovoltaic system. The whole system was simulated and the controllers were tested. The proposed maximum power point tracking control using neural networks maintains accurately the maximum power and shows fast dynamic response against sudden environmental condition changes or disturbances. Further research can be carried out in the near future to implement a physical model of the system and to compare the applied scheme with other conventional ones.

 

REFERENCES:

  • G. Villalva, J. R. Gazoli and E. Ruppert F. “Analysis and simulation of the P&O MPPT algorithm using alinearized array model”. Power electronics conference, 2009, Brazil.
  • Safri and S. Mekhilef. “Incremental conductance MPPT method for PV systems”. Electrical and Computer Engineering (CCECE). 2011. Canada.
  • I. Sulaiman, T.K. Abdul Rahman, I.Musirin and S.Shaari. “Optimizing Three-layer Neural Network Model for Grid-Connected Photovoltaic output prediction”. Conference on innovative technologies in intelligent systems and industrial applications.2009.
  • Subiyanto, A.Mohamed and M.A.Hannan. “Maximum Power Point Tracking in Grid Connected PV System using A Novel Fuzzy Logic Controller”. IEEE student conference on research and development, 2009.
  • Trishan Esram and Patrick L. Chapman. “Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques. “ IEEE Transactions on energy conversion, Vol.22, NO. 2, 2007.

Current harmonics Reduction of Three Phase Grid Connected Pulse Width Modulated Voltage Source Inverter by Hysteresis Current Controller with Offset Band

ABSTRACT

The development of power electronics technology gives ample of opportunity for the grid integration of renewable in an efficient way. Commonly pulse width modulated voltage source inverter is widely used for this purpose. The control technique of grid integrated inverters plays a major role for the reduction of harmonic and improvement of power quality in the system. The most commonly used current control technique for the control of the inverter is hysteresis current controller strategies. But the main drawback hysteresis current controller is the uneven switching frequency and higher harmonic distortion. In this paper a hysteresis current controller with offset band for three phase grid integrated pulse width modulated voltage source inverter has been implemented for considerable reduction of harmonic distortion and better power quality. The MATLAB-Simulink environment is used to model, study and simulate the system.

KEYWORDS

  1. Hysteresis Current Controller (HCC)
  2. Total Harmonic Distortion (THD)
  3. Pulse width modulated voltage source inverter (PWM VSI))
  4. Utility

 

SOFTWARE: MATLAB/SIMULINK

  

BLOCK DIAGRAM

Fig. 1. Overall Block diagram for three phase grid connected PWM-VSI

 

EXPECTED SIMULATION RESULTS

Fig. 2. Result of (a) DC Link Voltage (b) Grid voltage (c) grid current

Fig. 3. Grid current and reference current during change in load

Fig. 4 Current Error for HCC

Fig. 5. Active Power of load during change in load

Fig. 6. Reactive Power of load during change in load

Fig. 7. Result for HCC in steady state condition (a) DC link voltage (b) grid voltage (c) Grid current (d) THD

Fig. 8 Result of three phase grid current for HCC with offset band

Fig. 9 Grid current and reference current during change in load

Fig. 10. Current Error for HCC with offset

Fig. 11. Zero state of the inverter

Fig. 12. THD for HCC with offset band

CONCLUSION

The HCC with offset scheme is implemented to achieve lower THD and power quality improvement of the three phase grid connected PWM-VSI. The result obtained from simulation is compared with HCC system. The result reveals that the HCC with offset scheme has lower THD i.e. 2.10% as compared to HCC which is 3.22% and also the average switching frequency is less due to the zero level in the inverter output voltage. The another advantage of HCC with offset scheme is, average value of the current error is smaller as compared to HCC which can be verified by comparing the result of current error of both the schemes. It implies the power quality is superior in case of HCC with offset band.

 

REFERENCES

  • Falk, ,  “Prolog   to   renewable   energy   today   and   tomorrow,”  in Proceedings of the IEEE , vol.89, no.8, pp.1214-1215, Aug. 2001
  • Kroposki, B.; Pink, C.; DeBlasio, R.; Thomas, H.; Simões, M.; Sen, P.K., “Benefits of Power Electronic Interfaces for Distributed Energy Systems,” IEEE Transactions on Energy Conversion, , vol.25, no.3, pp.901-908, Sept.
  • Bose, B.K., “Global Energy Scenario and Impact of Power Electronics in 21st Century,” IEEE Transactions on Industrial Electronics, , vol.60, no.7, pp.2638-2651, July
  • Sung-Hun Ko; Lee, S.R.; Dehbonei, H.; Nayar, C.V., “Application of voltage- and current controlled voltage source inverters for distributed generation systems,” IEEE Transactions on Energy Conversion, , vol.21, no.3, pp.782-792, Sept.
  • G. Holmes, T. A. Lipo, B. P. McGrath, and W. Y. Kong, “Optimised design of stationary frame three phase AC current regulators,” IEEE Trans. Power Electron., vol. 24, no. 11, pp. 2417–2426, Nov. 2009.

 

Development of 10kW Three-Phase Grid Connected Inverter

 

ABSTRACT:

In this paper, modeling, simulation and experimental study of a 10kW three-phase grid connected inverter are presented. The mathematical model of the system is derived, and characteristic curves of the system are obtained in MATLAB with m-file for various switching frequencies, dc-link voltages and filter inductance values. The curves are used for parameter selection of three-phase grid connected inverter design. The parameters of the system are selected from these curves, and the system is simulated in Simulink. Modeling and simulation results are verified with experimental results at 10kW for steady state response, at 5kW for dynamic response and at −3.6 kVAr for reactive power. The inverter is controlled with Space Vector Pulse Width Modulation technique in d-q reference frame, and dSPACE DS1103 controller board is used in the experimental study. Grid current total harmonic distortion value  and efficiency are measured 3.59% and 97.6%, respectively.

KEYWORDS:

  1. Grid Connected Inverter
  2. Inverter Modeling
  3. Space Vector Pulse Width Modulation
  4. Total Harmonic Distortion

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Block diagram of the grid connected inverter.

EXPECTED SIMULATION RESULTS:

 

Fig. 2. THD variation of the grid current for Vdc = 650 V.

Fig. 3. THD variation of the grid current for fsw = 3 kHz.

Fig. 4. THD variation of the grid current for fsw = 9 kHz.

Fig. 5. Three-phase grid currents and voltage for fsw = 3 kHz.

Fig. 6 d-q components of the grid current for fsw = 3 kHz

Fig. 7. Three-phase grid currents and voltage for fsw = 9 kHz

Fig. 8. d-q components of the grid current for fsw = 9 kHz.

Fig. 9. d-q components of grid current.

 CONCLUSION:

In this study, performance of a 10kW three-phase grid connected inverter is investigated for various filter inductance values, DC-link voltages and switching frequencies. The system is modeled in m-file, thus characteristic curves of the inverter are obtained for different parameters. The THD values of grid current for 3 kHz and 9 kHz with 650V DC-link voltage are 10.22%and 3.41%. For verification of the modeling results, the system is simulated in Simulink. The control algorithm is implemented in Embedded Matlab Function in the simulation. The results are compared at 3 kHz and 9 kHz switching frequency, and modeling results are verified with simulation results that are 10.22% are 3.44%. In order to verify the modeling and simulation results, a laboratory prototype that is controlled by dSPACE DS1103 control board is realized. In the experimental study, THD values are measured as 10.68 and 3.59%. Furthermore, dynamic response and reactive power generation capability of the inverter are presented. The experimental results verify the modeling and simulation results. This verification shows that the system can be designed for various system and control parameters using the design curves. The study is realized for 10kW power but it is possible to obtain the characteristic curves for differen power values. According to results, the switching frequency or filter inductance value should be high to meet THD limit. Furthermore, efficiency is another important performance indicator. The efficiency at rated power and the european efficiency of the inverter is 97.6% and 97.2%  at 9 kHz.

REFERENCES:

[1] F. Blaabjerg, M. Liserre and K. Ma: “Power Electronics Converters for Wind Turbine Systems”, IEEE Transactio on Industry Applications, vol.48, pp. 708-719, 2012.

[2] F. Blaabjerg, Z. Chen, S.B. and Kjaer: “Power Electronics as Efficient Interface in Dispersed Power Generation Systems”, IEEE Transactions on Power Electronics, vol. 19,  pp. 1184-1194, 2004.

[3] J.M. Carrasco, L.G. Franquelo, J.T. Bialasiewicz, E. Galvan, R.C.P. Guisado, M.A.M. Prats, J.I. Leon and N.M. Alfonso:  “Power-Electronic Systems for the Grid Integration   of Renewable Energy Sources: A Survey”, IEEE Transactions  on Industrial Electronics, vol. 53, pp. 1002-1016, 2006.

[4] C. Ramonas and V. Adomavicius: “Research of the Converte  Possibilities in the Grid-tied Renewable Energ  Power Plant”, Elektronika IR Elektrotechnika, vol. 19, pp  37-40, 2013.

[5] D. Meneses, F. Blaabjerg, O. Garcia and J.A. Cobos: “Review and Comparison of Step-Up Transformerless Topologies for Photovoltaic AC-Module Application”, IEEE  Transactions on Power Electronics, vol. 28, pp. 2649-2663,  2013.

A Hysteresis Current Controller for Grid-Connected Inverter with Reduced Losses

ABSTRACT:

In this paper, a hysteresis current controller with reduced losses for three-phase grid-connected inverter is proposed. In the proposed hysteresis current controller, one of the inverter phase is clamped to the positive or negative inverter buses depending on the polarity of the phase current. Totally, each inverter phase is clamped for the duration of one third of the fundamental output period. As the inverter phase is inactive when the current is the highest, the switching losses are reduced. Simulation and experimental results are included to show the effectiveness of the proposed controller.

 

KEYWORDS:

  1. Current controller
  2. Hysteresis
  3. Grid-connected inverter,
  4. Losses
  5. Clamped

 

SOFTWARE: MATLAB/SIMULINK

  

CIRCUIT DIAGRAM:

Power controller of grid-connected inverter

Fig. 1. Power controller of grid-connected inverter

 

EXPECTED SIMULATION RESULTS:

conventional hysteresis current controller

Fig. 2. Output current and switching pattern of: (a) conventional hysteresis current controller, (b) proposed hysteresis current controller

 proposed hysteresis current controller

Fig. 3. Output current and switching pattern of: (a) conventional hysteresis current controller, (b) proposed hysteresis current controller

 

CONCLUSION:

A simple hysteresis current controller with reduced losses has been proposed in this paper. In the proposed current controller, one of the inverter phase is clamped to the positive or negative DC bus, depending on the polarity, when the magnitude of the current is the greatest. This lead to reduction of the average switching frequency as well as the switching losses. Simulation and experimental results have shown that the proposed hysteresis controller is able to reduce the switching losses without sacrificing the output current waveform.

 

REFERENCES:

  • Jain and V. Agarwal, “A Single-Stage Grid Connected Inverter Topology for Solar PV Systems With Maximum Power Point Tracking,” IEEE Trans. Power Electron., vol. 22, no. 5, pp. 1928–1940, 2007.
  • Mohseni and S. M. Islam, “A new vector-based hysteresis current control scheme for three-phase PWM voltage-source inverters,” IEEE Trans. Power Electron., vol. 25, no. 9, pp. 2299–2309, 2010.
  • P. Kazmierkowski and M. A. Dzieniakowski, “Review of currentregulation techniques for three-phase PWM inverters,” Proc. IECON’94 – 20th Annu. Conf. IEEE Ind. Electron., vol. 1, pp. 567–575, 1994.
  • Zhang and H. Lin, “Simplified model predictive current control method of voltage-source inverter,” 8th Int. Conf. Power Electron. – ECCE Asia, pp. 1726–1733, 2011.
  • C. Hua, C. W. Wu, and C. W. Chuang, “A digital predictive current control with improved sampled inductor current for cascaded inverters,” IEEE Trans. Ind. Electron., vol. 56, no. 5, pp. 1718–1726, 2009.

Power quality improvement in distribution network using DSTATCOM with battery energy storage system

ABSTRACT

The distribution static compensator (DSTATCOM) provides fast control of active and reactive powers to enable load compensation, harmonics current elimination, voltage flicker mitigation, voltage and frequency regulation. This paper presents power quality improvement technique in the presence of grid disturbances and wind energy penetration using DSTATCOM with battery energy storage system. DSTATCOM control is provided based on synchronous reference frame theory. A modified IEEE 13 bus test feeder with DSTATCOM and wind generator is used for the study. Power quality events during grid disturbances such as feeder tripping and re-closing, voltage sag, swell and load switching have been studied in association with DSTATCOM. The power quality disturbances due to wind generator outage, synchronization and wind speed variations have also been investigated. The study has been carried out using MATLAB/SIMULINK and the simulation results are compared with real time results obtained by the use of real time digital simulator (RTDS) for validating the effectiveness of proposed methodology. The proposed method has been proved to be effective in improvement of power quality with all disturbances stated above.

 

KEYWORDS

  1. Battery energy storage system
  2. Radial distribution feeder
  3. DSTATCOM
  4. Synchronous reference frame theory

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig.1. Proposed DSTATCOM with BESS.

 

SIMULATION RESULTS

Fig.2. Feeder tripping and re-closing without DSTATCOM in the network (a) RMS voltage at bus 632, (b) active power flow and (c) reactive power flow

Fig.3. Feeder tripping and re-closing with DSTATCOM in the network (a) RMS voltage at bus 632, (b) active power flow and (c) reactive power flow

Fig.4. Load switching without DSTATCOM in the network (a) RMS voltage at bus 632, (b) active power flow and (c) reactive power flow

Fig.5. Load switching with DSTATCOM in the network (a) RMS voltage at bus 632, (b) active power flow and (c) reactive power flow.

Fig.6. Voltage sag and swell (a) without DSTATCOM, (b) with DSTATCOM and (c) reactive power flow during voltage sag and swell.

Fig. 7 Wind synchronization (a) voltage without DSTATCOM, (b) voltage with DSTATCOM, (c) active power flow with DSTATCOM and (d) reactive power flow with DSTATCOM.

Fig. 8. Wind outage (a) voltage without DSTATCOM, (b) voltage with DSTATCOM, (c) active power flow with DSTATCOM and (d) reactive power flow with DSTATCOM

Fig. 9. Wind speed variation.

 

CONCLUSION

The proposed research work investigates into PQ events associated with distribution network due to grid disturbances such as voltage sag, swell, load switching, feeder tripping and re-closing. The DSTATCOM has been proposed to improve the power quality in the above events. The proposed DSTATCOM with SRF based control has been proved to be effective in improving the power quality in these events at grid level. The power quality events associated with wind operations such as wind generator outage, grid synchronization of wind generator and wind speed variations have been improved by the use of proposed DSTATCOM in the distribution network. From, these studies it has been established that the DSTATCOM can effectively be used to improve the power quality in the distribution network with wind generation and during grid disturbances. The results have been validated in real time utilizing RTDS. The real time results are very close to the simulation results which shows the effectiveness of proposed DSTATCOM with BESS for improvement of PQ in the distribution system.

 

REFERENCES

  • Ibrahim W, Morcos M. A power quality perspective to system operational diagnosis using fuzzy logic and adaptive techniques. IEEE Trans Power Deliv 2003;18(3):903–9. http://dx.doi.org/10.1109/TPWRD.2003.813885.
  • Ray P, Mohanty S, Kishor N. Classification of power quality disturbances due to environmental characteristics in distributed generation system. IEEE TransSust Energy 2013;4(2):302–13. http://dx.doi.org/10.1109/TSTE.2012.2224678.
  • Tascikaraoglu A, Uzunoglu M, Vural B, Erdinc O. Power quality assessment of wind turbines and comparison with conventional legal regulations: a case study in turkey. Appl Energy 2011;88(5):1864–72. http://dx.doi.org/10.1016/j. apenergy.2010.12.001.
  • Dash P, Padhee M, Barik S. Estimation of power quality indices in distributed generation systems during power islanding conditions. Int J Electr Power Energy Syst 2012;36(1):18–30. http://dx.doi.org/10.1016/j.ijepes.2011.10.019.
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Simulation and Comparison of SPWM and SVPWM Control for Three Phase Inverter

ABSTRACT:

A voltage source inverter is commonly used to supply a three-phase induction motor with variable frequency and variable voltage for variable speed applications. A suitable pulse width modulation (PWM) technique is employed to obtain the required output voltage in the line side of the inverter. The different methods for PWM generation can be broadly classified into Triangle comparison based PWM (TCPWM) and Space Vector based PWM (SVPWM). In TCPWM methods such as sine-triangle PWM, three phase reference modulating signals are compared against a common triangular carrier to generate the PWM signals for the three phases. In SVPWM methods, a revolving reference voltage vector is provided as voltage reference instead of three phase modulating waves. The magnitude and frequency of the fundamental component in the line side are controlled by the magnitude and frequency, respectively, of the reference vector. The highest possible peak phase fundamental is very less in sine triangle PWM when compared with space vector PWM. Space Vector Modulation (SVM) Technique has become the important PWM technique for three phase Voltage Source Inverters for the control of AC Induction, Brushless DC, Switched Reluctance and Permanent Magnet Synchronous Motors. The study of space vector modulation technique reveals that space vector modulation technique utilizes DC bus voltage more efficiently and generates less harmonic distortion when compared with Sinusoidal PWM (SPWM) technique. In this paper first a model for Space vector PWM is made and simulated using MATLAB/SIMULINK software and its performance is compared with Sinusoidal PWM. The simulation study reveals that Space vector PWM utilizes dc bus voltage more effectively and generates less THD when compared with sine PWM.

KEYWORDS:

  1. PWM
  2. SVPWM
  3. Three phase inverter
  4. Total harmonic distortion

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure-1. Block diagram of SPWM inverter fed induction motor.

EXPECTED SIMULATION RESULTS:

Figure-2a. Response of line voltage in SPWM.

Figure-3. Response of line voltage in SPWM.

Figure-4a. Response of line current in SPWM.

Figure-5b. Response of line current in SPWM.

Figure-6. Response of rotor speed in SPWM.

Figure.7. Response of torque in SPWM.

Figure-8. Response of line voltage in SVPWM.

Figure-9. Response of line current in SVPWM.

Figure-10. Response of rotor speed in SVPWM.

Figure-11. Response of torque in SVPWM.

 CONCLUSION:

Space vector Modulation Technique has become the most popular and important PWM technique for Three Phase Voltage Source Inverters for the control of AC Induction, Brushless DC, Switched Reluctance and Permanent Magnet Synchronous Motors. In this paper first comparative analysis of Space Vector PWM with conventional SPWM for a two level Inverter is carried out. The Simulation study reveals that SVPWM gives 15% enhanced fundamental output with better quality i.e. lesser THD compared to SPWM. PWM strategies viz. SPWM and SVPWM are implemented in MATLAB/SIMULINK software and its performance is compared with conventional PWM techniques. Owing to their fixed carrier frequencies cfin conventional PWM strategies, there are cluster harmonics around the multiples of carrier frequency. PWM strategies viz. Sinusoidal PWM and SVPWM utilize a changing carrier frequency to spread the harmonics continuously to a wideband area so that the peak harmonics are reduced greatly.

REFERENCES:

Zhenyu Yu, Arefeen Mohammed, Issa Panahi. 1997. A Review of Three PWM Techniques. Proceedings of the American Control Conference Albuquerque, New Mexico. pp. 257-261.

  1. G. Holmes and T. A. Lipo. 2003. Pulse Width Modulation for Power Converters: Principles and Practice. M.E. El-Hawary, Ed. New Jersey: IEEE Press, Wiley- Interscience. pp. 215-313.
  2. Erfidan, S. Urugun, Y. Karabag and B. Cakir. 2004. New Software implementation of the Space Vector Modulation. Proceedings of IEEE Conference. pp.1113-1115.
  3. Rathnakumar, J. Lakshmana Perumal and T. Srinivasan. 2005. A New software implementation of space vector PWM. Proceedings of IEEE Southeast conference. pp.131-136.
  4. Hariram and N. S. Marimuthu. 2005. Space vector switching patterns for different applications- A comparative analysis. Proceedings of IEEE conference. pp. 1444-1449.

Modeling and Simulation of a Distribution STATCOM (D-STATCOM) for Power Quality Problems-Voltage Sag and Swell Based on Sinusoidal Pulse Width Modulation (SPWM)

ABSTRACT:

This paper presents the systematic procedure of the modeling and simulation of a Distribution STATCOM (DSTATCOM) for power quality problems, voltage sag and swell based on Sinusoidal Pulse Width Modulation (SPWM) technique. Power quality is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure of end use equipments. The major problems dealt here is the voltage sag and swell. To solve this problem, custom power devices are used. One of those devices is the Distribution STATCOM (D-STATCOM), which is the most efficient and effective modern custom power device used in power distribution networks. D-STATCOM injects a current in to the system to correct the voltage sag and swell.The control of the Voltage Source Converter (VSC) is done with the help of SPWM. The proposed D-STATCOM is modeled and simulated using MATLAB/SIMULINK software.

KEYWORDS:

  1. Distribution STATCOM (D-STATCOM)
  2. MATLAB/SIMULINK
  3. Power quality problems
  4. Sinusoidal Pulse  Width Modulation (SPWM)
  5. Voltage sag and swell
  6. Voltage  Source Converter (VSC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Schematic representation of the D-STATECOM for a typical custom

power application.

EXPECTED SIMULATION RESULTS:

 Fig. 2. Voltage Vrms at load point, with three-phase fault: (a) Without DSTATCOM and (b) With D-STATCOM, 750I-lf .

Fig. 3. Voltage vrms at load point, with three phase-ground fault: (a)

Without D-STATCOM and (b) With D-STATCOM.

Fig. 4. Voltage Vrms at load point, with line-ground fault: (a) Without DSTATCOM and (b) With D-STATCOM.

Fig. 5. Voltage vrms at load point, with line-line fault: (a) Without DSTATCOM and (b) With D-STATCOM.

Fig. 6. Voltage vrms at load point, with line-line-ground fault: (a) Without

D-STATCOM and (b) With D-STATCOM.

CONCLUSION:

This paper has presented the power quality problems such as voltage sags and swell. Compensation techniques of custom power electronic device D-ST ATCOM was presented. The   design and applications of D-STATCOM for voltage sags, swells and comprehensive results were presented. The Voltage Source Convert (VSC) was implemented with the help of Sinusoidal Pulse Width Modulation (SPWM). The control scheme was tested under a wide range of operating conditions, and it was observed to be very robust in every case. For modeling and simulation of a D-ST ATCOM by using the highly developed graphic facilities available in MA TLAB/SIMULINK were used. The simulations carried out here showed that the D-STATCOM provides relatively better voltage regulation capabilities.

 REFERENCES:

[I] O. Anaya-Lara, E. Acha, “Modeling and analysis of custom power  systems by PSCAD/EMTDC,” IEEE Trans. Power Delivery, vol. 17, no .I, pp. 266-272, January 2002.

[2] S. Ravi Kumar, S. Sivanagaraju, “Simualgion of D-Statcom and DVR in  power system,” ARPN jornal of engineering and applied science, vol. 2,   no. 3, pp. 7-13, June 2007.

[3] H. Hingorani, “Introducing custom power”, IEEE Spectrum, vol. 32, no.6, pp. 41-48, June 1995.

[4] N. Hingorani, “FACTS-Flexible ac transmission systems,” in Proc. IEE 5th Int Conf AC DC Transmission, London, U.K., 1991, Conf Pub.  345, pp. 1-7.

[5] Mahesh Singh, Vaibhav Tiwari, “Modeling analysis and soltion to  power quality problems,” unpublished.