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.

Operation of Series and Shunt Converters with 48-pulse Series Connected three-level NPC Converter for UPFC

ABSTRACT:

The 48-pulse series connected 3-level Neutral Point Clamped (NPC) converter approach has been used in Unified Power Flow Controller (UPFC) application due to its near sinusoidal voltage quality. This paper investigates the control and operation of series and shunt converters with 48-pulse Voltage Source Converters (VSC) for UPFC application. A novel controller for series converter is designed based on the “angle control” of the 48-pulse voltage source converter. The complete simulation model of shunt and series converters for UPFC application is implemented in Matlab/Simulink. The practical real and reactive power operation boundary of UPFC in a 3-bus power system is specifically investigated. The performance of UPFC connected to the 500-kV grid with the proposed controller is evaluated. The simulation results validate the proposed control scheme under both steady state and dynamic operating conditions.

KEYWORDS:

1.      48-pulse converter

2.      Neutral Point Clamped (NPC) converter

3.      Angle control

4.      Unified Power Flow Controller (UPFC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. 48-pulse VSC based +100 MVA UPFC in a 3-bus power system

EXPECTED SIMULATION RESULTS:

Fig.2 Line real power (top) and reactive power (bottom) references (MVA)

Fig. 3 Measured real and reactive power, DC link voltage and converter angles (Top trace: measured line real power (MW); second top trace: measured line reactive power, (MVar); third top trace: DC bus voltage; fourth top trace: shunt converter angle α ; fifth top trace: series converter angle α ; bottom trace: series converter angle σ ).

Fig.4 Shunt converter output voltage (blue), Line voltage (green) and shunt

converter current (red) (5.42s-5.48s)

Fig.5 Shunt converter real power (blue, p.u.), reactive power (green, p.u.).

Fig.6 Current (p.u.) of transmission line L1.

Fig.7 Series converter 48 pulse converter voltage (blue, p.u.) and current

(black, p.u.) during time 2~2.03s (when real power reference is increased)

Fig. 8 Series converter angle σ vs. DC bus voltage (Top trace: line real

power and reactive power; second top trace: shunt converter injected reactive

power; third top trace: DC bus voltage; bottom trace: series converter

angle σ )

CONCLUSION:

In this paper, the control and operation of series and shunt converters with 48-pulse series connected 3-level NPC converter for UPFC application are investigated. A new angle controller for 48-pulse series converter is proposed to control the series injection voltage, and therefore the real and reactive power flow on the compensated line. The practical UPFC real and reactive power operation boundary in a 3-bus system is investigated; this provides a benchmark to set the system P and Q references. The simulation of UPFC connected to the 500-kV grid verifies the proposed controller and the independent real power and reactive power control of UPFC with series connected transformer based 48-pulse converter.

REFERENCES:

[1] N. G. Hingorani, "Power electronics in electric utilities: role of power electronics in future power systems," Proceedings of the IEEE, vol. 76, pp. 481, 1988.

[2] N. G. Hingorani and L. Gyugyi, Understanding FACTS: concepts and technology of flexible AC transmission systems: IEEE Press, 2000.

[3] L. Gyugyi, "Dynamic compensation of AC transmission lines by solid-state synchronous voltage sources," IEEE Transactions on Power Delivery, vol. 9, pp. 904, 1994.

[4] C. D. Schauder, L. Gyugyi etc. “Operation of the unified power flow controller (UPFC) under practical constraints,” IEEE Transactions on Power Delivery, vol. 13, pp. 630-639, April 1998.

[5] L. Gyugyi. “Unified power-flow control concept for flexible AC transmission systems,” IEE Proceedings - Generation, Transmission and Distribution, vo. 139, pp. 323-331, July 1992.