STATCOM-Based Voltage Regulator for Self-Excited Induction Generator Feeding Nonlinear Loads

IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 53, NO. 5, OCTOBER, 2006

ABSTRACT: This paper deals with the performance analysis of a static compensator (STATCOM)-based voltage regulator for self-excited induction generators (SEIGs) supplying nonlinear loads. In practice, a number of loads are nonlinear in nature, and therefore, they inject harmonics in the generating systems. The SEIG’s performance, being a weak isolated system, is very much affected by these harmonics. The additional drawbacks of the SEIG are poor voltage regulation and that it requires an adjustable reactive power source with varying loads to maintain a constant terminal voltage. A three-phase insulated-gate-bipolar transistor- based current-controlled voltage source inverter working as STATCOM is used for harmonic elimination, and it provides the required reactive power for the SEIG, with varying loads to maintain a constant terminal voltage. A dynamic model of the SEIG–STATCOM feeding nonlinear loads using stationary d−q axes reference frame is developed for predicting the behaviour of the system under transient conditions. The simulated results show that SEIG terminal voltage is maintained constant, even with nonlinear balanced and unbalanced loads, and free from harmonics using STATCOM-based voltage regulator.

KEYWORDS:

  1. Harmonic elimination
  2. Load balancing
  3. Nonlinear loads
  4. Self-excited induction generator (SEIG)
  5. Static compensator (STATCOM)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Schematic diagram of proposed scheme of SEIG–STATCOM system

CONTROL SYSTEM:

Fig.2 Control scheme of SEIG–STATCOM system

EXPECTED SIMULATION RESULTS:

 Fig. 3. Voltage buildup of SEIG and switching in STATCOM.

Fig. 4. Waveform of three-phase SEIG–STATCOM system supplying diode rectifier with resistive load change from no load, to three-phase (22 kW), to one-phase (15 kW), to three-phase (22 kW) loads, and to no load.

Fig. 5. Waveform of three-phase SEIG–STATCOM system supplying diode rectifier with capacitive filter and resistive load change from no load, to three-phase (15 kW), to one-phase (24 kW), to three-phase (15 kW) loads, and to no load.

Fig. 6. Waveforms of three-phase SEIG–STATCOM system supplying diode rectifier with capacitive filter and resistive load change from no load, to three-phase (15 kW), to three-phase (22 kW), to three-phase (15 kW) loads, and to no load.

Fig. 7. Waveforms of three-phase SEIG–STATCOM system supplying thyristorized rectifier with resistive load change from no load, to three-phase (18 kW) at 60firing angle, to no load.

 CONCLUSION:

It has been observed that the developed mathematical model of a three-phase SEIG–STATCOM is capable of simulating its performance while feeding nonlinear loads under transient conditions. From the simulated results, it has been found that the SEIG terminal voltage remains constant, with the sinusoidal feeding of the three-phase or single-phase rectifiers with resistive and with dc capacitive filter and resistive loads. When a single-phase rectifier load is connected, the STATCOM balances the unbalanced load currents, and the generator currents and voltage remain balanced and sinusoidal; therefore, the STATCOM acts as a load balancer. The rectifier-based nonlinear load generates the harmonics, which are also eliminated by STATCOM. Therefore, it is concluded that STATCOM acts as voltage regulator, load balancer, and harmonic eliminator, resulting in an SEIG system that is an ideal ac power-generating system.

REFERENCES:

[1] C. Grantham, D. Sutanto, and B. Mismail, “Steady state and transient analysis of self-excited induction generator,” Proc. Inst. Electr. Eng., vol. 136, no. 2, pp. 61–68, Mar. 1989.

[2] K. E. Hallenius, P. Vas, and J. E. Brown, “The analysis of saturated self excited asynchronous generator,” IEEE Trans. Energy Convers., vol. 6, no. 2, pp. 336–341, Jun. 1991.

[3] M. H. Salama and P. G. Holmes, “Transient and steady-state load performance of a stand-alone self-excited induction generator,” Proc. Inst. Electr. Eng.—Electr. Power Appl., vol. 143, no. 1, pp. 50–58, Jan. 1996.

[4] L. Wang and R. Y. Deng, “Transient performance of an isolated induction generator under unbalanced excitation capacitors,” IEEE Trans. Energy Convers., vol. 14, no. 4, pp. 887–893, Dec. 1999.

Commutation Torque Ripple Reduction in BLDC Motor Using Modified SEPIC Converter and Three-level NPC Inverter

IEEE Transactions on Power Electronics, 2016

ABSTRACT: This paper presents a new power converter topology to suppress the torque ripple due to the phase current commutation of a brushless DC motor (BLDCM) drive system. A combination of a 3-level diode clamped multilevel inverter (3-level DCMLI), a modified single-ended primary-inductor converter (SEPIC), and a dc-bus voltage selector circuit are employed in the proposed torque ripple suppression circuit. For efficient suppression of torque pulsation, the dc-bus voltage selector circuit is used to apply the regulated dc-bus voltage from the modified SEPIC converter during the commutation interval. In order to further mitigate the torque ripple pulsation, the 3-level DCMLI is used in the proposed circuit. Finally, simulation and experimental results show that the proposed topology is an attractive option to reduce the commutation torque ripple significantly at low and high speed applications.

KEYWORDS:

  1. Brushless direct current motor (BLDCM),
  2. Dc-bus voltage control
  3. Modified single-ended primary-inductor converter
  4. Level diode clamped multilevel inverter (3-level DCMLI)
  5. Torque ripple

 SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

 

Fig. 1. Proposed converter topology with a dc-bus voltage selector circuit for BLDCM

 EXPECTED SIMULATION RESULTS:

 

Fig. 2. Simulated waveforms of phase current and torque at 1000 rpm and 0.825 Nm with 5 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and a switch selection circuit. (d) BLDCM fed by proposed topology.

Fig. 3 Simulated waveforms of phase current and torque at 6000 rpm and 0.825 Nm with 5 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and a switch selection circuit. (d) BLDCM fed by proposed topology.

 

Fig. 4 Simulated waveforms of phase current and torque at 1000 rpm and 0.825 Nm with 20 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and switch a selection circuit. (d) BLDCM fed by proposed topology.

Fig. 5 Simulated waveforms of phase current and torque at 6000 rpm and 0.825 Nm with 20 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and a switch selection circuit. (d) BLDCM fed by proposed topology

Fig. 6. Simulated waveforms of phase current and torque at 1000 rpm and 0.825 Nm with 80 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and a switch selection circuit. (d) BLDCM fed by proposed topology.

Fig. 7 Simulated waveforms of phase current and torque at 6000 rpm and 0.825 Nm with 80 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and a switch selection circuit. (d) BLDCM fed by proposed topology

CONCLUSION:

In this paper, a commutation torque ripple reduction circuit has been proposed using 3-level DCMLI with modified SEPIC converter and a dc-bus voltage selector circuit. A laboratory-built drive system has been tested to verify the proposed converter topology. The suggested dc-bus voltage control strategy is more effective in torque ripple reduction in the commutation interval. The proposed topology accomplishes the successful reduction of torque ripple in the commutation period and experimental results are presented to compare the performance of the proposed control technique with the conventional 2-level inverter, 3-level DCMLI, 2-level inverter with SEPIC converter and the switch selection circuit-fed BLDCM. In order to obtain significant torque ripple suppression, quietness and higher efficiency, 3-level DCMLI with modified SEPIC converter and the voltage selector circuit is a most suitable choice to obtain high-performance operation of BLDCM. The proposed topology may be used for the torque ripple suppression of BLDCM with the very low stator winding inductance.

REFERENCES:

[1] N. Milivojevic, M. Krishnamurthy, Y. Gurkaynak, A. Sathyan, Y.-J. Lee, and A. Emadi, “Stability analysis of FPGA-based control of brushless DC motors and generators using digital PWM technique,” IEEE Trans. Ind. Electron., vol. 59, no. 1, pp. 343–351, Jan. 2012.

[2] X. Huang, A. Goodman, C. Gerada, Y. Fang, and Q. Lu, “A single sided matrix converter drive for a brushless dc motor in aerospace applications,” IEEE Trans. Ind. Electron., vol. 59, no. 9, pp. 3542–3552, Sep. 2012.

[3] X. Huang, A. Goodman, C. Gerada, Y. Fang, and Q. Lu, “Design of a five-phase brushless DC motor for a safety critical aerospace application,” IEEE Trans. Ind. Electron., vol. 59, no. 9, pp. 3532-3541, Sep. 2012.

[4] J.-G. Lee, C.-S. Park, J.-J. Lee, G. H. Lee, H.-I. Cho, and J.-P. Hong, “Characteristic analysis of brushless motor condering drive type,” KIEE, pp. 589-591, Jul. 2002.

[5] T. H. Kim and M. Ehsani, “Sensorless control of BLDC motors from near-zero to high speeds,” IEEE Trans. Power Electron., vol. 19, no. 6, pp. 1635–1645, Nov. 2004.

 

 

 MPPT with Single DC–DC Converter and Inverter for Grid-Connected Hybrid Wind-Driven PMSG–PV System

IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, 2015

ABSTRACT: A new topology of a hybrid distributed generator based on photovoltaic and wind-driven permanent magnet synchronous generator is proposed. In this generator, the sources are connected together to the grid with the help of only a single boost converter followed by an inverter. Thus, compared to earlier schemes, the proposed scheme has fewer power converters. A model of the proposed scheme in the d − q-axis reference frame is developed. Two low-cost controllers are also proposed for the new hybrid scheme to separately trigger the dc–dc converter and the inverter for tracking the maximum power from both sources. The integrated operations of both proposed controllers for different conditions are demonstrated through simulation and experimentation. The steady-state performance of the system and the transient response of the controllers are also presented to demonstrate the successful operation of the new hybrid system. Comparisons of experimental and simulation results are given to validate the simulation model.

KEYWORDS:

  1. Grid-connected hybrid system
  2. Hybrid distributed generators (DGs)
  3. Smart grid
  4. Wind-driven PMSG–PV

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

Fig. 1. Proposed DG system based on PMSG–PV sources.

EXPECTED SIMULATION RESULTS:

(a)

(b)

Fig. 2. DC link steady-state waveforms. (a) Experimental (voltage—50 V/div, current—10 A/div, and time—500 ms/div). (b) Simulated (voltage—20 V/div, current—5 A/div, and time—500 ms/div.

(a)

(b)

Fig. 3. Steady-state grid voltage and current waveforms. (a) Experimental (voltage—50 V/div, current—10 A/div, and time—20 ms/div). (b) Simulated (voltage—50 V/div, current—5 A/div, and time— 20 ms/div).

Experimental (Voltage 50V/div, Duty-cycle 0.6/div, Time 2s/div)

Simulated (Voltage 20V/div, Duty-cycle 0.5/div, Time 2s/div)

(a) Changes in rectifier output voltage and duty cycle of the boost converter.

Experimental (Voltage 50V/div, Current 10 A/div, Time 2s/div)

Simulated (Voltage 50V/div, Current 10/div)

(b) Changes in dc-link voltage and current

Experimental (Voltage 50V/div, Current 10A/div, Time 2s/div)

Simulated (Voltage 50V/div, Current 10A/div, Time 2s/div)

Fig.4. Transient response for a step change in PMSG shaft speed.. (c) Changes in grid current.

 CONCLUSION:

A new reliable hybrid DG system based on PV and wind driven PMSG as sources, with only a boost converter followed by an inverter stage, has been successfully implemented. The mathematical model developed for the proposed DG scheme has been used to study the system performance in MATLAB. The investigations carried out in a laboratory prototype for different irradiations and PMSG shaft speeds amply confirm the utility of the proposed hybrid generator in zero-net-energy buildings. In addition, it has been established through experimentation and simulation that the two controllers, digital MPPT controller and hysteresis current controller, which are designed specifically for the proposed system, have exactly tracked the maximum powers from both sources. Maintenance-free operation, reliability, and low cost are the features required for the DG employed in secondary distribution systems. It is for this reason that the developed controllers employ very low cost microcontrollers and analog circuitry. Furthermore, the results of the experimental investigations are found to be matching closely with the simulation results, thereby validating the developed model. The steady state waveforms captured at the grid side show that the power generated by the DG system is fed to the grid at unity power factor. The voltage THD and the current THD of the generator meet the required power quality norms recommended by IEEE. The proposed scheme easily finds application for erection at domestic consumer sites in a smart grid scenario.

REFERENCES:

[1] J. Byun, S. Park, B. Kang, I. Hong, and S. Park, “Design and implementation of an intelligent energy saving system based on standby power reduction for a future zero-energy home environment,” IEEE Trans. Consum. Electron., vol. 59, no. 3, pp. 507–514, Oct. 2013.

[2] J. He, Y. W. Li, and F. Blaabjerg, “Flexible microgrid power quality enhancement using adaptive hybrid voltage and current controller,” IEEE Trans. Ind. Electron., vol. 61, no. 6, pp. 2784–2794, Jun. 2014.

[3] W. Li, X. Ruan, C. Bao, D. Pan, and X. Wang, “Grid synchronization systems of three-phase grid-connected power converters: A complexvector- filter perspective,” IEEE Trans. Ind. Electron., vol. 61, no. 4, pp. 1855–1870, Apr. 2014.

[4] C. Liu, K. T. Chau, and X. Zhang, “An efficient wind-photovoltaic hybrid generation system using doubly excited permanent-magnet brushless machine,” IEEE Trans. Ind. Electron, vol. 57, no. 3, pp. 831–839, Mar. 2010.

[5] S. A. Daniel and N. A. Gounden, “A novel hybrid isolated generating system based on PV fed inverter-assisted wind-driven induction generators,” IEEE Trans. Energy Convers., vol. 19, no. 2, pp. 416–422, Jun. 2004.

Design of External Inductor for Improving Performance of Voltage Controlled DSTATCOM

IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, 2015

ABSTRACT: A distribution static compensator (DSTATCOM) is used for load voltage regulation and its performance mainly depends upon the feeder impedance and its nature (resistive, inductive, stiff, non-stiff). However, a study for analyzing voltage regulation performance of DSTATCOM depending upon network parameters is not well defined. This paper aims to provide a comprehensive study of design, operation, and flexible control of a DSTATCOM operating in voltage control mode. A detailed analysis of the voltage regulation capability of DSTATCOM under various feeder impedances is presented. Then, a benchmark design procedure to compute the value of external inductor is presented. A dynamic reference load voltage generation scheme is also developed which allows DSTATCOM to compensate load reactive power during normal operation, in addition to providing voltage support during disturbances. Simulation and experimental results validate the effectiveness of the proposed scheme.

KEYWORDS:

  1. Distribution static compensator (DSTATCOM)
  2. Current control
  3. Voltage control
  4. Power factor
  5. Power quality

 SOFTWARE: MATLAB/SIMULINK

EQUIVALENT CIRCUIT DIAGRAM:

 

 Fig. 1. Three phase equivalent circuit of DSTATCOM topology in distribution system.

EXPECTED SIMULATION RESULTS:

Fig. 2. Voltage regulation performance of conventional DSTATCOM with resistive feeder. (a) PCC voltages. (b) Load Voltages. (c) Source currents. (d) Filter currents. (e) Load currents.

Fig. 3. Simulation results. (a) During normal operation (i)-(v). (b) During voltage sag (vi)-(x). (c) During voltage swell (xi)-(xv).

CONCLUSION:

This paper has presented design, operation, and control of a DSTATCOM operating in voltage control mode (VCM). After providing a detailed exploration of voltage regulation capability of DSTATCOM under various feeder scenarios, a benchmark design procedure for selecting suitable value of external inductor is proposed. An algorithm is formulated for dynamic reference load voltage magnitude generation. The DSTATCOM has improved voltage regulation capability with a reduced current rating VSI, reduced losses in the VSI and feeder. Also, dynamic reference load voltage generation scheme allows DSTATCOM to set different constant reference voltage during voltage disturbances. Simulation and experimental results validate the effectiveness of the proposed solution. The external inductor is a very simple and cheap solution for improving the voltage regulation, however it remains connected throughout the operation and continuous voltage drop across it occurs. The future work includes operation of this fixed inductor as a controlled reactor so that its effect can be minimized by varying its inductance.

REFERENCES:

[1] M. H. Bollen, Understanding power quality problems. vol. 3, IEEE press New York, 2000.

[2] S. Ostroznik, P. Bajec, and P. Zajec, “A study of a hybrid filter,” IEEE Trans. Ind. Electron., vol. 57, no. 3, pp. 935–942, Mar. 2010.

[3] C. Kumar and M. Mishra, “A voltage-controlled DSTATCOM for power quality improvement,” IEEE Trans. Power Del., vol. 29, no. 3, pp. 1499– 1507, June 2014.

[4] Q. Liu, L. Peng, Y. Kang, S. Tang, D. Wu, and Y. Qi, “A novel design and optimization method of an LCL filter for a shunt active power filter,” IEEE Trans. Ind. Electron., vol. 61, no. 8, pp. 4000–4010, Aug. 2014.

[5] T. Aziz, M. Hossain, T. Saha, and N. Mithulananthan, “VAR planning with tuning of STATCOM in a DG integrated industrial system,” IEEE Trans. Power Del., vol. 28, no. 2, pp. 875–885, Apr. 2013.

A New BLDC Motor Drives Method Based on BUCK Converter for Torque Ripple Reduction

2006, IEEE

ABSTRACT: This paper presents a comprehensive analysis on torque ripples of brushless dc motor drives in conduction region and commutation region. A novel method for reducing the torque ripple in brushless dc motors with a single current sensor has been proposed by adding BUCK converter in the front of 3-phase inverter.In such drives, torque ripple suppression technique is theoretically effective in commutation region as well as conduction region. Effectiveness and feasibility of the proposed control method is verified through experiments.

KEYWORDS:

  1. Brushless dc motor
  2. Torque ripple
  3. Conduction region
  4. Commutation region

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig1. The new proposed circuit configuration

EXPECTED SIMULATION RESULTS:

 

Fig.2. The 2-phase current-waveforms of conventional modulation mode

Fig.3. The 2-phase current-waveforms of new proposed modulation mode

Fig.4.The commutation current-waveforms of conventional modulation mode

Fig.5.The commutation current-waveforms of new proposed modulation mode

CONCLUSION:

In this paper,a new torque ripple reduction method based on buck converter has been proposed for brushless dc motor drives using a single dc current sensor. In such control method, the dc-link current sensor can give correct information corresponding to the motor phase currents to eliminate torque ripples in conduction region. Meanwhile, torque ripples have been attenuated effectively during commutation region. Subsequently effectiveness and feasibility of the proposed control method are verified through experiments.

REFERENCES:

[1] Joong-Ho Song and Ick Choy, “Commutation torque ripple reduction in brushless DC motor drives using a single DC current sensor,”IEEE Trans. on Power Electronics,vol. 19, No.2 ,pp.312-319,March 2004.

[2] Byoung-Hee Kang,Choel-Ju Kim,Hyung-Su Mok and Gyu-Ha Choe, “Analysis of torque ripple in BLDC motor with commutation time,”Proceedings of IEEE,vol.2,pp.1044-1048, June 2001.

[3] Carlson R,Lajoie-Mazenc M and Fagundes J.C.d.S, “Analysis of torque ripple due to phase communtation in brushless DC machines,”IEEE Trans. on Industry Applications,vol.28,no.3, pp.632-638,May-June 1992.

[4] Luk P.C.K and Lee C.K, “Efficient modeling for a brushless DC motor drive,”International Conference on Industrial Electronics,Control and Instrumentation,vol.1,pp.188-191, September 1994.

[5] Lei Hao,Toliyat,H.A, “BLDC motor full speed range operation including the flux-weakening region,”IEEE-IAS Annual Meeting,vol.1,pp.618-624, Octorber 2003.

Dynamic voltage restoration projects in hydearbad

Dynamic voltage restoration (DVR)

Dynamic voltage restoration (DVR) is a method of overcoming voltage sags that occur in electrical power distribution.These are a problem because spikes consume power and sags reduce efficiency of some devices. DVR saves energy through voltage injections that can affect the phase and wave-shape of the power being supplied.

Devices used for DVR include static var devices, which are series compensation devices that use voltage source converters (VSC). The first such system in North America was installed in 1996 – a 12.47 kV system located in Anderson, South Carolina.

Dynamic Voltage Restoration

Real time implementation of unity power factor correction converter based on fuzzy logic

Power Factor Correction in BLDC motor Drives Using DC-DC Converters

Transformerless Single-Phase Universal Active Filter With UPS Features and Reduced Number of Electronic Power Switches

PI tuning of Shunt Active Filter using GA and PSO algorithm

PSO – PI Based DC Link Voltage Control Technique for Shunt Hybrid Active

Power Filter

Artificial Neural Network based Three Phase Shunt Active Power Filter

Cascaded open end winding transformer based DVR

Brushless DC motor drive with power factor  regulation using Landsman converter

Comparative Analysis of 6, 12 and 48 Pulse T-STATCOM

Versatile Unified Power Quality Conditioner Applied to Three-Phase Four-Wire Distribution Systems Using a Dual Control Strategy

IEEE Transactions on Power Electronics, 2015

ABSTRACT: This paper presents the study, analysis and practical implementation of a versatile unified power quality conditioner (UPQC), which can be connected in both three-phase three-wire or three-phase four-wire distribution systems for performing the series-parallel power-line conditioning. Thus, even when only a three-phase three-wire power system is available at a plant site, the UPQC is able to carry out power-line compensation for installed loads that require a neutral conductor to operate. Different from the control strategies used in the most of UPQC applications in which the controlled quantities are non-sinusoidal, this UPQC employs a dual compensation strategy, such that the controlled quantities are always sinusoidal. Thereby, the series converter is controlled to act as a sinusoidal current source, whereas the parallel converter operates as a sinusoidal voltage source. Thus, because the controlled quantities are sinusoidal, it is possible to reduce the complexity of the algorithms used to calculate the compensation references. Therefore, since the voltage and current controllers are implemented into the synchronous reference frame, their control references are continuous, decreasing the steady-state errors when traditional proportional-integral controllers are employed. Static and dynamic performances, as well as the effectiveness of the dual UPQC are evaluated by means of experimental results.

 KEYWORDS:

  1. Active filter
  2. Dual control strategy
  3. Power conditioning
  4. Three-phase distribution systems
  5. UPQC

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. 3P4W distribution system based on UPQC topology connected to 3P3W power system.

EXPECTED SIMULATION RESULTS:

 Fig. 2. Experimental results for the loads presented in Table III: (a) UPQC currents for unbalanced three-phase -phase load (1) (20 A/div, 5 ms/div): Load currents (𝑖𝐿𝑎, 𝑖𝐿𝑏, 𝑖𝐿𝑐) and 𝑖𝐿𝑛, Compensated source currents (𝑖𝑠𝑎, 𝑖𝑠𝑏, 𝑖𝑠𝑐), and Currents of the parallel converter (𝑖𝑐𝑎, 𝑖𝑐𝑏, 𝑖𝑐𝑐) and 𝑖𝑐𝑛; (b) Currents and voltages of phase “a” of the UPQC for the unbalanced three-phase load (2) (20 A/div, 100V/div, 5 ms/div): Load currents (𝑖𝐿𝑎, 𝑖𝐿𝑏, 𝑖𝐿𝑐); Currents of phase “a”: load 𝑖𝐿𝑎, parallel converter 𝑖𝑐𝑎 and source 𝑖𝑠𝑎; voltages and currents of phase “a”: load current 𝑖𝐿𝑎 , source current 𝑖𝑠𝑎, utility voltage 𝑣𝑠𝑎 and load voltage 𝑣𝐿𝑎, (c) UPQC currents for three-phase load (1) (2.5 ms/div): Load currents (𝑖𝐿𝑎, 𝑖𝐿𝑏, 𝑖𝐿𝑐) (5 A/div), Source compensated currents (𝑖𝑠𝑎, 𝑖𝑠𝑏, 𝑖𝑠𝑐) (10 A/div), Parallel converter currents (𝑖𝑐𝑎, 𝑖𝑐𝑏, 𝑖𝑐𝑐) (10 A/div).

Fig. 3. Voltages of the UPQC under utility harmonics and unbalances for the unbalanced three-phase load (1): (a) Utility voltages (𝑣𝑠𝑎, 𝑣𝑠𝑏, 𝑣𝑠𝑐) (50 V/div, 2,5ms/div), Load voltages (𝑣𝐿𝑎, 𝑣𝐿𝑏, 𝑣𝑠𝐿) (50 V/div, 2,5ms/div) and series compensating voltages (𝑣𝐶𝑎, 𝑣𝐶𝑏 and 𝑣𝐶𝑐) (50 V/div, 2,5ms/div); (b) (a) Utility voltages (𝑣𝑠𝑎, 𝑣𝑠𝑏, 𝑣𝑠𝑐) (50 V/div, 2,5ms/div), Load voltages (𝑣𝐿𝑎, 𝑣𝐿𝑏, 𝑣𝑠𝐿) (50 V/div, 2,5ms/div) and series compensating voltages (𝑣𝐶𝑎, 𝑣𝐶𝑏 and 𝑣𝐶𝑐) (50 V/div, 2,5ms/div)

Fig. 4. Voltages and current of the UPQC for the unbalanced three-phase load 1: (a) DC-bus voltage (𝑉𝐷𝐶) (100 V/div, 500ms/div) and load currents (𝑖𝐿𝑎, 𝑖𝐿𝑏, 𝑖𝐿𝑐) (20 A/div, 500ms/div); (b) DC-bus voltage (𝑉𝐷𝐶) (100 V/div, 500ms/div) and source currents (𝑖𝑠𝑎, 𝑖𝑠𝑏, 𝑖𝑠𝑐) (20 A/div, 500ms/div); (c) DC-bus voltage (𝑉𝐷𝐶) (100 V/div, 5ms/div) and details of the source currents (𝑖𝑠𝑎, 𝑖𝑠𝑏, 𝑖𝑠𝑐) after the first load transient (20 A/div, 5ms/div).

Fig. 5. UPQC under voltage sag disturbance (phase ‘a’): utility voltage (𝑣𝑠𝑎), load voltage (𝑣𝐿𝑎) and series compensating voltage (𝑣𝐶𝑎) (200 V/div, 25ms/div).

 CONCLUSION:

This paper presents a practical and versatile application based on UPQC, which can be used in three-phase three-wire (3P3W), as well as three-phase four-wire (3P4W) distribution systems. It was demonstrated that the UPQC installed at a 3P3W system plant site was able to perform universal active filtering even when the installed loads required a neutral conductor for connecting one or more single-phase loads (3P4W). The series-parallel active filtering allowed balanced and sinusoidal input currents, as well as balanced, sinusoidal and regulated output voltages. By using a dual control compensating strategy, the controlled voltage and current quantities are always sinusoidal. Therefore, it is possible to reduce the complexity of the algorithms used to calculate the compensation references. Furthermore, since voltage and current SRF-based controllers are employed, the control references become continuous, reducing the steady-state errors when conventional PI controllers are used. Based on digital signal processing and by means of extensive experimental tests, static and dynamic performances, as well as the effectiveness of the dual UPQC were evaluated, validating the theoretical development.

REFERENCES:

[1] H. Fujita, and H. Akagi, “The unified power quality conditioner: The integration of series and shunt active filters,” IEEE Trans. Power Electron., vol. 13, no. 2, pp. 315-322, Mar. 1998.

[2] R. J. M. Santos,. J. C. Cunha, and M. Mezaroba, “A simplified control technique for a dual unified power quality conditioner,” IEEE Trans. Ind. Electron., vol. 61, no. 11, pp. 5851-5860, Nov. 2014.

[3] B.W. França, L.F. Silva, M. A Aredes, and M., Aredes, “An improved iUPQC controller to provide additional grid-voltage regulation as a STATCOM,” IEEE Trans. Ind. Electron., , vol. 62, no. 3, pp. 1345-1352, Mar. 2015.

[4] R. A. Modesto, S. A. O. Silva, and A. A., Oliveira, “Power quality improvement using a dual unified power quality conditioner/uninterruptible power supply in three-phase four-wire systems,” IET Power Electronics, vol. 8, no. 3, pp. 1595-1605, Sept. 2015.

[5] V. Khadkikar, “Enhancing electric power quality using UPQC: A comprehensive overview,” IEEE Trans. Power Electron., vol. 27, no. 5, pp. 2284-2297, May 2012.

 

A Novel Five-Level Voltage Source Inverter With Sinusoidal Pulse Width Modulator for Medium-Voltage Applications

IEEE Transactions on Power Electronics, 2015

ABSTRACT: This paper proposes a new five-level voltage source inverter for medium-voltage high-power applications. The proposed inverter is based on the upgrade of a four-level nested neutral-point clamped converter. This inverter can operate over a wide range of voltages without the need for connecting power semiconductor in series, has high-quality output voltage and fewer components compared to other classic five-level topologies. The features and operation of the proposed converter are studied and a simple sinusoidal PWM scheme is developed to control and balance the flying capacitors to their desired values. The performance of the proposed converter is evaluated by simulation and experimental results.

 KEYWORDS:

  1. Multilevel converter
  2. Dc–ac power conversion
  3. Sinusoidal pulse width modulation (SPWM)

 SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. New five-level three-phase inverter.

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation waveforms in steady-state condition (a) inverter voltage, (b) output currents, and (c) voltages of flying capacitors (m = 0.95).

Fig. 3. Simulation waveforms in steady-state condition (a) inverter voltage,

(b) output currents, and (c) voltages of flying capacitors (m = 0.65).

Fig. 4. Simulation waveforms in steady-state condition (inductive load) (a)

inverter voltage, (b) output currents, and (c) voltages of flying capacitors (m = 0.95, PF = 0.7).

Fig. 5. Simulation waveforms in steady-state condition (capacitive load)

(a) inverter voltage, (b) output currents, and (c) voltages of flying capacitors (m = 0.9, PF = 0.7).

Fig. 6. Simulation waveforms in transient-state condition; load changes from half-load to full-load (a) inverter voltage, (b) output currents, and (c) voltages of flying capacitors (m = 0.95).

Fig. 7. Simulation waveforms; voltage of flying capacitors with and without

the controller

CONCLUSION:

This paper introduces a new five-level voltage source inverter for medium-voltage applications. The proposed topology is the upgrade of the four-level NNPC converter that can operate over a wide range of input voltage without any power semiconductor in series. The proposed converter has fewer components as com- pared with classic multilevel converters and the voltage across the power semiconductors is only one-fourth of the dc-link. A SPWM strategy is developed to control the output voltage and regulate the voltage of the flying capacitors. The proposed strategy is very intuitive and simple to implement in a digital system. The performance of the proposed converter is confirmed by simulation in MATLAB/Simulink environment and the feasibility of the proposed converter is evaluated experimentally and results are presented.

 REFERENCES:

[1] B. Wu, High-Power Converters and AC Drives. Piscataway, NJ, USA: IEEE Press, 2006.

[2] J. Rodriguez, S. Bernet, B. Wu, J. Pontt, and S. Kouro, “Multilevel voltagesource- converter topologies for industrial medium-voltage drives,” IEEE Trans. Ind. Electron., vol. 54, no. 6, pp. 2930–2945, Dec. 2007.

[3] S. Kouro, M. Malinowski, K. Gopakumar, J. Pou, L. G. Franquelo, B.Wu, J. Rodriguez, M. A. Perez, and J. I. Leon, “Recent advances and industrial applications of multilevel converters,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2553–2580, Aug. 2010.

[4] Y. Zhang, G. Adam, T. Lim, S. Finney, andB.Williams, “Hybrid multilevel converter: Capacitor voltage balancing limits and its extension,” IEEE Trans. Ind. Informat., vol. 9, no. 4, pp. 2063–2073, Aug. 2013.

[5] M. Saeedifard, R. Iravani, and J. Pou, “Analysis and control of DCcapacitor- voltage-drift phenomenon of a passive front-end five-level converter,” IEEE Trans. Ind. Electron., vol. 54, no. 6, pp. 3255–3266, Dec. 2007.

Development and Comparison of an Improved Incremental Conductance Algorithm for Tracking the MPP of a Solar PV Panel

IEEE Transactions on Sustainable Energy, 2015

ABSTRACT: This paper proposes an adaptive and optimal control strategy for a solar photovoltaic (PV) system. The control strategy ensures that the solar PV panel is always perpendicular to sunlight and simultaneously operated at its maximum power point (MPP) for continuously harvesting maximum power. The proposed control strategy is the control combination between the solar tracker (ST) and MPP tracker that can greatly improve the generated electricity from solar PV systems. Regarding the ST system, the paper presents two drive approaches including open- and closed-loop drives. Additionally, the paper also proposes an improved incremental conductance algorithm for enhancing the speed of the MPP tracking of a solar PV panel under various atmospheric conditions as well as guaranteeing that the operating point always moves toward the MPP using this proposed algorithm. The simulation and experimental results obtained validate the effectiveness of the proposal under various atmospheric conditions.

KEYWORDS:

  1. Maximum power point tracker (MPPT)
  2. Solar tracker (ST)
  3. Solar PV panel

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Block diagram of the experimental setup.

EXPECTED SIMULATION RESULTS:

Fig. 2. Description of the variations of the solar irradiation and temperature.

Fig. 3. Obtained maximum output power with the P&O and improved InC algorithms under the variation of the solar irradiation.

Fig. 4. Obtained maximum output power with the InC and improved InC algorithms under the variation of the solar irradiation.

Fig. 5. Obtained maximum output power with the P&O and improved InC algorithms under both the variations of the solar irradiation and temperature.

Fig. 6. Obtained maximum output power with the InC and improved InC algorithms under both the variations of the solar irradiation and temperature.

Fig. 7. MPPs of the solar PV panel under the variation of the solar irradiation

Fig. 8. MPPs of the solar PV panel under both the variations of the solar irradiation and temperature.

Fig. 9. Experimental result of obtained maximum output power with the improved InC algorithm under the variation of the solar irradiation.

CONCLUSION:

It is obvious that the adaptive and optimal control strategy plays an important role in the development of solar PV systems. This strategy is based on the combination between the ST and MPPT in order to ensure that the solar PV panel is capable of harnessing the maximum solar energy following the sun’s trajectory from dawn until dusk and is always operated at the MPPs with the improved InC algorithm. The proposed InC algorithm improves the conventional InC algorithm with an approximation which reduces the computational burden as well as the application of the CV algorithm to limit the search space and increase the convergence speed of the InC algorithm. This improvement overcomes the existing drawbacks of the InC algorithm. The simulation and experimental results confirm the validity of the proposed adaptive and optimal control strategy in the solar PV panel through the comparisons with other strategies.

REFERENCES:

[1] R. Faranda and S. Leva, “Energy comparison of MPPT techniques for PV systems,” WSES Trans. Power Syst., vol. 3, no. 6, pp. 446–455, 2008.

[2] X. Jun-Ming, J. Ling-Yun, Z. Hai-Ming, and Z. Rui, “Design of track control system in PV,” in Proc. IEEE Int. Conf. Softw. Eng. Service Sci., 2010, pp. 547–550.

[3] Z. Bao-Jian, G. Guo-Hong, and Z. Yan-Li, “Designment of automatic tracking system of solar energy system,” in Proc. 2nd Int. Conf. Ind. Mechatronics Autom., 2010, pp. 689–691.

[4] W. Luo, “A solar panels automatic tracking system based on OMRON PLC,” in Proc. 7th Asian Control Conf., 2009, pp. 1611–1614.

[5] W. Chun-Sheng,W. Yi-Bo, L. Si-Yang, P. Yan-Chang, and X. Hong-Hua, “Study on automatic sun-tracking technology in PV generation,” in Proc. 3rd Int. Conf. Elect. Utility Deregulation Restruct. Power Technol., 2008, pp. 2586–2591.

Novel Cascaded Switched-Diode Multilevel Inverter for Renewable Energy Integration

IEEE Transactions on Energy Conversion, 2016

ABSTRACT: In this paper, a new topology of two-stage cascaded switched-diode (CSD) multilevel inverter is proposed for medium voltage renewable energy integration. First, it aims to reduce the number of switches along with its gate drivers. Thus, the installation space and cost of a multilevel inverter are reduced. The spike removal switch added in the first stage of the inverter provides a flowing path for the reverse load current, and as a result, high voltage spikes occurring at the base of the stepped output voltage based upon conventional CSD multilevel inverter topologies are removed. Moreover, to resolve the problems related to dc source fluctuations of multilevel inverter used for renewable energy integration, the clock phase-shifting (CPS) one-cycle control (OCC) is developed to control the two-stage CSD multilevel inverter. By shifting the clock pulse phase of every cascaded unit, the staircase-like output voltage waveforms are obtained and a strong suppression ability against fluctuations in dc sources is achieved. Simulation and experimental results are discussed to verify the feasibility and performances of the two-stage CSD multilevel inverter controlled by the CPS OCC method.

KEYWORDS:

  1. Novel cascaded multilevel inverter
  2. Two-stage
  3. One-cycle control

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

 Fig. 1. Renewable energy generation system with multilevel inverter.

EXPECTED SIMULATION RESULTS:

 

Fig. 2. The output voltage and current of the first stage converter of the 5-level simulation prototype. (a) Output voltage ug ; (b) Output current ig .

Fig. 3. The output voltage and inductor current of the 5-level simulation

prototype. (a) Output voltage uCD ; (b) Output voltage after filter uo ; (c) Inductor current il

Fig. 4. The output voltage and current of the first stage converter of the

9-level simulation prototype. (a) Output voltage ug ; (b) Output current ig .

Fig. 5. The output voltage and inductor current of the 9-level simulation

prototype. (a) Output voltage uCD ; (b) Output voltage after filter uo ; (c) Inductor current il .

Fig. 6. The simulation results of the 5-level prototype: DC source with basic unit 1 contains a 10 Hz ripple with amplitude 16 V. (a) uo using CPS OCC; (b) uo using CPS SPWM.

Fig. 7. The simulation results of the 5-level prototype: DC source with each

basic unit contains a 10 Hz ripple with amplitude 8 V. (a) uo using CPS OCC; (b) uo using CPS SPWM.

CONCLUSION:

A new topology of two-stage CSD multilevel inverter has been proposed in this paper. n cascaded basic units and one spike removal switch form the first stage. Then by adding a full-bridge inverter as the second-stage converter, both of the positive and negative output voltage levels are generated. Since the one full-bridge converter in the output side leads to the restriction on high-voltage applications, the proposed topology is suitable for medium-voltage renewable energy integration. The comparisons with the CHB and cascaded half-bridge topologies show that the CSD topology requires less switches and related gate drivers for realizing Nlevel output voltage. As a result, the installation space and cost of the multilevel inverter are reduced. Meanwhile, the spike removal switch added in the first stage provides a flowing path for the reverse load current under R-L loads, thus, the high voltage spikes, due to the collapsing magnetic field in a very short time interval, are removed. The CPS OCC method, which is composed by n similar but dependent OCC controllers, has been designed and implemented to control the CSD multilevel inverter. Simulation and experimental results demonstrate that, by shifting the clock pulse phase of each cascaded unit, the staircase-like voltage waveforms are obtained. Moreover, to evaluate the performance of CPS OCC, in both the simulation and experiment, the DC sources mixed with low frequency ripples are implemented to simulate the DC supply from renewable energy generations, and the comparative results between CPS OCC and CPS SPWM reveal that CPS OCC possesses a superior ability in suppressing the unbalance or low frequency ripples in DC sources. These results demonstrate that the CPS OCC method can be a substitute for conventional controllers to control multilevel inverters for renewable energy integration with improved control performances.

REFERENCES:

[1] M. S. B. Ranjiana, P. S. Wankhade, and N. D. Gondhalekar, “A modified cascaded H-bridge multilevel inverter for solar applications,” in Proc. 2014 Int. Conf. Green Comput. Commun. Elect. Eng., 2014, pp. 1–7.

[2] F. S. Kang, S. J. Park, S. E. Cho, C. U. Kim, and T. Ise, “Mutilevel PWM inverters suitable for the use of stand-alone photovoltaic power systems,” IEEE Trans. Energy Convers., vol. 20, no. 4, pp. 906–915, Dec. 2005.

[3] L. V. Nguyen, H.-D. Tran, and T. T. Johnson, “Virtual prototyping for distributed control of a fault-tolerant modular multilevel inverter for photovoltaics,” IEEE Trans. Energy Convers., vol. 29, no. 4, pp. 841–850, Dec. 2014.

[4] J. Rodriguez, J. S. Lai, and F. Z. Peng, “Mutilevel inverters: A survey of topologies, controls, and application,” IEEE Trans. Ind. Electron., vol. 49, no. 4, pp. 724–738, Aug. 2002.

[5] F. Z. Peng and J. S. Lai, “Mutilevel converters—A new breed of power converters,” IEEE Trans. Ind. Appl., vol. 32, no. 3, pp. 509–517, May/Jun. 1996.