Power Quality Improvement in Conventional Electronic Load Controller for an Isolated Power Generation

ABSTRACT:

This paper deals with the power quality improvement in a conventional electronic load controller (ELC) used for isolated pico-hydropower generation based on an asynchronous generator (AG). The conventional ELC is based on a six-pulse uncontrolled diode bridge rectifier with a chopper and an auxiliary load. It causes harmonic currents injection resulting distortion in the current and terminal voltage of the generator. The proposed ELC employs a 24-pulse rectifier with 14 diodes and a chopper. A polygon wound autotransformer with reduced kilovolts ampere rating for 24-pulse ac–dc converter is designed and developed for harmonic current reduction to meet the power quality requirements as prescribed by IEEE standard-519. The comparative study of two topologies, conventional ELC (six-pulse bridge-rectifier-based ELC) and proposed ELC (24-pulse bridge-rectifier-based ELC) is carried out in MATLAB using SIMULINK and Power System Block set toolboxes. Experimental validation is carried out for both ELCs for regulating the voltage and frequency of an isolated AG driven by uncontrolled pico-hydro turbine.

KEYWORDS:

1.      Electronic load controller (ELC)

2.       Isolated asynchronous generator (IAG)

3.      Pico-hydro turbine

4.      24-pulse bridge rectifier.

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. IAG system configuration and control strategy of a chopper switch in

a six-pulse diode bridge ELC.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Simulated transient waveforms of IAG on application and removal of consumer load using six-pulse diode-bridge-rectifier-based ELC.

Fig. 3. Simulated transient waveforms on application and removal of consumer load using 24-pulse rectifier-based ELC.

Fig. 4. Waveforms and harmonic spectra of (a) conventional six-pulse ELC current (i_da ), (b) generator voltage (v_a), and (c) generator current (i_a ) under the zero consumer load conditions.

Fig. 5. Waveforms and harmonic spectra of (a) proposed 24-pulse ELC current (i_da ), (b) generator voltage (v_a ), and (c) generator current (i_a ) under the zero consumer load conditions.

 CONCLUSION:

The proposed ELC has been realized using 24-pulse converter and a chopper. A comparative study of both types of ELCs (6-pulse and 24-pulse configured ELC) has been demonstrated on the basis of simulation using standard software MATLAB and developing a hardware prototype in the laboratory environment. The proposed 24-pulse ELC has given improved performance of voltage and frequency regulation of IAG with negligible harmonic distortion in the generated voltage and current at varying consumer loads.

REFERENCES:

[1] B. Singh, “Induction generator—A prospective,” Electr. Mach. Power Syst., vol. 23, pp. 163–177, 1995.

[2] R. C. Bansal, T. S. Bhatti, and D. P. Kothari, “Bibliography on the application of induction generator in non conventional energy systems,” IEEE Trans. Energy Convers., vol. EC-18, no. 3, pp. 433–439, Sep. 2003.

[3] G. K. Singh, “Self-excited induction generator research—A survey,” Electr. Power Syst. Res., vol. 69, no. 2/3, pp. 107–114, May 2004.

[4] R. C. Bansal, “Three phase isolated asynchronous generators: An overview,” IEEE Trans. Energy Convers., vol. 20, no. 2, pp. 292–299, Jun. 2005.

[5] O. Ojo, O. Omozusi, and A. A. Jimoh, “The operation of an inverter assisted single phase induction generator,” IEEE Trans. Ind. Electron., vol. 47, no. 3, pp. 632–640, Jun. 2000.

A Control Strategy for Unified Power Quality Conditioner

ABSTRACT:

 This paper presents a control strategy for a Unified Power Quality Conditioner. This control strategy is used in three-phase three-wire systems. The UPQC device combines a shunt-active tilter together with a series-active filter in a hack to- back configuration, to simultaneously compensate the supply voltage and the load current. Previous works presented a control strategy for shunt-active filter that guarantees sinusoidal, balanced and minimized source currents even if under unbalanced and / or distorted system voltages, also known as “Sinusoidal Fryze Currents”. Then, this control strategy was extended to develop a dual control strategy for series-active filter. Now, this paper develops the integration principles of shunt current compensation and series voltages compensation, both based on instantaneous active and non-active powers, directly calculated from a-b-c phase voltages and line currents. Simulation results are presented to validate the proposed UPQC control strategy.

KEYWORDS:

1.      Active Filters

2.      Active Power Line Conditioners

3.      Instantaneous Active and Reactive Power

4.      Sinusoidal Fryze Currents

5.      Sinusoidal Fryze Voltages

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 . General configuration of the Unified Power Quality Conditioner - UPQC.

 EXPECTED SIMULATION RESULTS:

Fig. 2: Load current. current of the shunt active filter and source current.

Fig 3 Supply voltage. compensating voltage and the compensated voltage delivered to the critical load

Fig. 4. DC link voltage signal v_DC and DC voltage regulator signal G_loss

Fig. 5. Source currents, compensated voltages  and the compensated

voltage V_aw together with the source current l

CONCLUSION:

A control strategy for Unified Power Quality Conditioner - the UPQC - is proposed. Simulation results have validated the proposed control strategy, for the use in three-phase three-wire systems. In case of using in three phase four-wire systems, there is the necessity of compensating the neutral current. In this case, three-phase four wire PWM converter is necessary.

The computational efforts to develop the proposed control strategy is reduced, if compared with pq-Theory based controllers, since the α-β-0 transformation is avoided. For three-phase three-wire systems, the performance of the proposed approach is comparable with those based on the pq Theory, without loss of robustness even if operating under distorted and unbalanced system voltage conditions.

Presently, the authors are working on the possibility of extending the proposed control strategy for the use in three phase four-wire systems.

REFERENCES:

[1] S. Fryze. "Wirk-. Blind- und Scheinleistung in elektrischen Stromkainsen mit nicht-sinusfomigen Verlauf von Strom und Spannung." ETZ-Arch. Elektrotech.. vol. 53. 1932, pp. 596-599. 625-627. 700-702.

[2] L. Malesani. L. Rosseto. P. Tenti. "Active Filter for Reactive Power and Harmonics Compensation", IEEE - PESC 1986. pp. 321-330.

[3] Luis F.C. Monteiro, M. Aredes. "A Comparative Analysis among Different Control Strategies for Shunt Active Filters." Proc. (CDROM) of the V INDUSCON - Conferencia de Aplicacoes In dustriais. Salvador. Brazil, July 2002. pp.345-350.

[4] T. Furuhashi, S . Okuma. Y. Uchikawa, "A Study on the Theory of Instantaneous Reactive Power," IEEE Trans. on Industrial Electronics. vol. 37. no. 1. pp. 86-90. Feb. 1990.

[5] L. Rossetto, P. Tenti. "Evaluation of Instantaneous Power Terms in Multi-Phase Systems: Techniques and Application to Power- Conditioning Equipments." ETEP - Eur.. Trans.elect. Po wer Eng . vol. 4. no. 6. pp. 469-475, Nov./Dec. 1994.

Implementation of a DC Power System with PV Grid-Connection and Active Power Filtering

 ABSTRACT:  

The objective of this paper is to develop a DC power supply system with photovoltaic (PV) grid-connection and active power filtering. The proposed power supply system consists of an input stage and an output stage. In the input stage, a dc/dc converter incorporated with the perturbation-and-observation method can draw the maximum power from the PV source, which can be delivered to the output stage. On the other hand, grid connection or active power filtering, depending on the power of photovoltaic; will be implemented by a dc/ac inverter in the output stage. Two microcontrollers are adopted in the proposed system, of which one is to implement the MPPT algorithm, the other is used to determine the operation modes, which can be grid connection mode, direct supply mode or active power filtering mode. Finally, the experimental results are measured to verify the proposed algorithms and feasibility of the system.

KEYWORDS:

1.      12 Pulse AClDC Converter

2.       Phase Controller

3.      Autotransformer

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Block diagram of the proposed DC power system

 EXPECTED SIMULATION RESULTS:

 Fig. 2 The P_in, V₁ and i₁ waveforms of the MPPT Algorithm

(V₁: 100 V/div,i₁: 2 A/div, P_in: 200 W/div, time: 10 s/div)

Fig. 3 Experimental results of the MPPT function of the boost converter operate under input voltage change (150V→200V→150V).

(V_ac: 100 V/div,i_C : 5 A/div, time: 10 ms/div)

(a)

(V_ac: 100 V/div,i_C : 5 A/div, time: 10 ms/div)

(b)

(V_ac: 100 V/div,i_C : 5 A/div, time: 10 ms/div)

Fig. 4 The AC voltage V_ac and output current i_o waveforms while output power is (a) 1kW, (b) 500W and (c) 250W.

(i_L : 5 A/div, time: 10 ms/div)

Fig. 5 The load current waveform with R_n=50Ω.

 Fig. 6 Comparison the measured harmonic amount of

grid voltage and current with Europe harmonic standard IEC 1000-3-2 Class A before compensation

Fig. 7 Comparison the measured harmonic amount of grid voltage and current with Europe harmonic standard IEC 1000-3-2 Class A after compensation

(V_ac : 200 V/div,i_S : 10 A/div, i_C : 5 A/div time: 10 ms/div)

Fig. 8 The measured results of AC voltage V_ac, AC current i_s and compensated current i_c of the system operate under the active power filtering mode.

(a)

(b)

(V_ac : 200 V/div,i_ac : 10 A/div, i_C : 5 A/div, time: 20 ms/div)

Fig. 9 The load variations of the proposed power system operates under active power filtering mode (a) heavy load → light load, and (b) light load →heavy load.

 (V_S : 100 V/div,V_C1 : 300 V/div, i₁ : 5 A/div, i_C : 2 A/div, P_in : 500 W/div )

Fig. 10 The operational mode switching of the proposed r system.

CONCLUSION:

A DC power system with PV grid-connection and active power filtering has been presented in this paper, in which a DC/DC converter is firstly used to promote the output voltage of PV array and achieve the MPP. The proposed system can automate switching among the grid connection mode, direct supply mode or active power filtering mode according to the output power of PV array. In addition, two microcontrollers are used to act as system controllers, in which can except implement complicate calculation and PWM output, it can also reduce the hardware complication and cost to improve the reliability and feasibility of system. The experimental results have verified the feasibility and flexibility of the proposed system.

REFERENCES:

[1] A. Lohner, T. Meyer and A. Nagel,“A New Panel- Integratable Inverter Concept for Grid-Connected Photovoltaic System,”IEEE International Symposium on Industrial Electronics, Vol. 2, June 1996, pp. 827-831.

[2] U. Herrmann, H. G. Langer, H. van der Broeck,“Low Cost DC to AC Converter for Photovoltaic Power Conversion in Residential Applications,”Proceedings of the IEEE PESC, June 1993, pp. 588-594.

[3] J. H. R. Enslin, M. S. Wolf, D. B. Snyman and W. Sweiges,“Integrated Photovoltaic Maximum Power Point Tracking Converter,”IEEE Trans. On Industrial Electronics, Vol. 44, No. 6, 1997, pp. 769-773.

[4] S. J. Chiang, K. T. Chang and C. Y. Yen,“Residential Photovoltaic Energy Storage System,” IEEE Trans. on Industrial Electronics, Vol. 45, No. 3, 1998, pp. 385-394.

[5] S. Sopitpan, P. Changmoang and S. Panyakeow,“PV Systems With/without Grid Back-up for Housing Applications,”Proceedings of the IEEE Photovoltaic Specialists Conference, 2000, pp. 1687-1690.

Speed Control of PMBLDC Motor Using MATLAB/Simulink and Effects of Load and Inertia Changes

ABSTRACT:

Modeling and simulation of electromechanical systems with machine drives are essential steps at the design stage of such systems. This paper describes the procedure of deriving a model for the brush less dc motor with 120-degree inverter system and its validation in the MATLAB/Simulink platform. The discussion arrives at a closed-loop speed control, in which PI algorithm is adopted and the position-pulse determination is done through current control for a standard trapezoidal BLDC motors. The simulation results for BLDC motor drive systems confirm the validity of the proposed method.

KEYWORDS:

1.      PMBLDC Motor

2.      Simulation and modeling

3.      Speed control

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

                                

Figure 1. PMBLDC motor drive system

EXPECTED SIMULATION RESULTS:

Steady state current

 Figure 2. Stator phase currents

 Back EMF of the BLDC motor

Figure 3. Trapezoidal back EMF

    

 

Figure 4. Reference current waveform

 Figure 5. Representative phase voltage (van)

Figure 6. Torque and speed responses during startup transients

Figure 7. Torque and speed responses - step input change - moment of

inertia 0.013 kg-m2 (step time 0.5 S)

Figure 8 Torque and speed responses at moment of inertia 0.098 kg-m'

Figure 9. Torque and speed-Step input with moment of inertia 0.098

kg-m2 (step time 0.5 S)

Figure 10. Step load torque (9Nm) at 0.75 step

Figure 11. Step load torque (25 Nm) at 0.75

 

Figure 12. Application of heavy load (100 Nm)

Figure 13. Load toque 25Nm at step of 0.5

CONCLUSION:

The nonlinear simulation model of the BLDC motors drive system with PI control based on MATLAB/Simulink platform is presented. The control structure has an inner current closed-loop and an outer-speed loop to govern the current. The speed controller regulates the rotor movement by varying the frequency of the pulse based on signal feedback from the Hall sensors. The performance of the developed PI algorithm based speed controller of the drive has revealed that the algorithm devises the behavior of the PMBLDC motor drive system work satisfactorily. Current is regulated within band by the hysteresis current regulator. And also by varying the moment of inertia observe that increase in moment of inertia it increases simulation time to reach the steady state value. Consequently, the developed controller has robust speed characteristics against parameters and inertia variations. Therefore, it can be adapted speed control for high performance BLDC motor.

REFERENCES:

 [I] Duane C.Hanselman, "Brushless Permanent-Magnet Motor Design", McGraw-Hill, Inc., New York, 1994.

[2] TJ.E. Miller, 'Brushless Permanent Magnet and Reluctance Motor Drives.' Oxford Science Publication, UK, 1989.

[3] RKrishnan, Electric Motor Drives: Modeling, Analysis, and Control, Prentice-Hall, Upper Saddle River, NJ, 2001.

[4] P Pillay and R Krishnan, "Modeling, simulation, and analysis of permanent Magnet motor drives. Part II: The brushless dc motor drive," IEEE Transactions on Industry Applications, vol.IA-25, no.2, pp.274-279, Mar./Apr. 1989.

[5] RKrishnan and A. J. Beutler, "Performance and design of an axial field permanent magnet synchronous motor servo drive," Proceedings of IEEE lASAnnual Meeting, pp.634-640,1985.