Modeling and Analysis of 3-Phase VSI using SPWM Technique for Grid Connected Solar PV System

ABSTRACT:

Solar energy is one of the most promising Renewable Energy Sources (RES) that can be used to produce electric energy through Photovoltaic (PV) process. The Solar Photovoltaic (SPV) systems which directly supply power to the grid are becoming more popular. A power electronic converter which converts DC power from the PV array to AC power at required voltage and frequency levels is known as Inverter. Generally different Pulse Width Modulation (PWM) techniques have been implemented for grid connected 3-phase Voltage Source Inverter (VSI) system. This paper describes few types of PWM techniques and mathematical model of LC filter circuit is given using state space analysis. Sine-PWM technique is proposed for 3-phase VSI and implemented using the state space model of the LC filter circuit. The simulation is performed in MATLAB/Simulink platform. Simulation results are presented for the inverter and load side to demonstrate the satisfactory performance of the sine-PWM technique.

KEYWORDS:

1.      Pulse width modulation

2.      Solar photovoltaic

3.      Voltage source inverter

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. General Block Diagram of Grid Connected SPV system

EXPECTED SIMULATION RESULTS:

Fig. 2. Carrier wave (V_tri) and Modulating wave (V_sin)

 Fig. 3. Inverter Output line to line Voltages (V_iAB,V_iBC,V_iCA)

Fig. 4. Inverter Output Currents (i_iA,i_iB,i_iC)

Fig. 5. Load line to line voltages (V_LAB, V_LBC, V_LCA)

Fig. 6. Load Phase Currents (i_LA,i_LB,i_LC)

Fig. 7. Inverter output line voltage, Inverter output current, Load line

voltage, Load phase currents

CONCLUSION:

Increasing demand on energy efficiency and power quality issues, grid connected solar PV systems is taking a good place. In this paper SPWM and SVPWM techniques have been discussed for 3-phase grid connected VSI. The LC filter circuit is used in the proposed system. This filter circuit is mathematically modeled by using state space analysis and complete state space equation is obtained. The SPWM technique is implemented and simulated on 3 phases VSI using state space model of the LC filter circuit for grid connected solar PV system. Various simulation results are analyzed and presented on the inverter and load side of the proposed system in order to demonstrate the satisfactory performance of sine-PWM technique for grid connected solar PV system.

 REFERENCES:

[1] J.Y. Lee, and Y.Y. Sun, “A New SPWM Inverter with Minimum Filter Requirement,” International Journal of Electronics, Vol. 64, No. 5, pp. 815-826, 1988.

[2] K. Zhou and D. Wang, “Relationship Between Space-Vector Modulation and Three- Phase Carrier-Based PWM: A Comprehensive Analysis,” IEEE Transactions on Industrial Electronics, Vol. 49, No. 1, pp. 186- 196, February 2002.

[3] A.W. Leedy, and R.M. Nelms, “Harmonic Analysis of a Space Vector PWM Inverter using the Method of Multiple Pulses,” IEEE Transactions on Industrial Electronics, Vol. 4, pp. 1182-1187, July 2006.

[4] A.M. Khambadkone, and J. Holtz, “Current Control in Over-modulation Range for Space Vector Modulation based Vector Controlled Induction Motor Drives,” IEEE Industrial Electronics Society, Vol.2, pp. 1134- 1339, 2000.

[5] E. Hendawi, F. Khater, and A. Shaltout, “Analysis, Simulation and Implementation of Space Vector Pulse Width Modulation Inverter,” International Conference on Application of Electrical Engineering, pp. 124-131, 2010.

Indirect Vector Control of Induction Motor Using Sliding-Mode Controller

ABSTRACT:

The paper presents a sliding-mode speed control system for an indirect vector controlled induction motor drive for high performance. The analysis, design and simulation of the sliding-mode controller for indirect vector control induction motor are carried out. The proposed sliding-mode controller is compared with PI controller with no load and various load condition. The result demonstrates the robustness and effectiveness of the proposed sliding-mode control for high performance of induction motor drive system.

KEYWORDS:

1.      Indirect vector control

2.      Sliding mode control

3.      PI controller

4.      Induction motor

5.      Speed control

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Figure 1: Indirect vector controlled induction motor drive

                                                                                                                                                       

EXPECTED SIMULATION RESULTS:

Figure 2: Speed response of PI controller at no load

Figure 3:Speed response of Sliding-mode controller at no load

Figure 4: Speed response of PI controller at load

Figure 5: Speed response of Sliding- mode controller at load

Figure 6:X-Y plot of Rotor flux of PI controller

Figure 7: x-v plot of Rotor flux of Sliding-mode controller

CONCLUSION:

In this paper sliding-mode controller for the control of an indirect vector-controlled induction motor was described. The drive system was simulated with sliding-mode controller and PI controller and their performance was compared. Here simulation results shows that the designed sliding-mode controller realises a good dynamic behaviour of the motor with a rapid settling time, no overshoot and has better performance than PI controller. Sliding-mode control has more robust during change in load condition.

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 REFERENCES:

[1] B.K Bose "Modern power electronics and ac drives "Prentice-Hall OJ India, New Delhi, 2008.

[2] M.Masiala;B.Vafakhah,;A.Knght,;J.Salmon,;"Performa nce of PI and fuzzy logic speed control of field-oriented induction motor drive," CCECE , jul. 2007, pp. 397-400.

[3] F.Barrero;A.Gonzalez;A.Torralba,E.Galvan,;L.G.Franqu elo; "Speed control of induction motors using a novel Fuzzy-sliding mode structure,"IEEE Transaction on Fuzzy system, vol. 10, no.3, pp. 375-383, Jun 2002.

[4] H.F.Ho,K.W.E.Cheng, "position control of induction motor using indirect adaptive fuzzy sliding mode control," P ESA, , Sep. 2009, pp. 1-5.

[5] RKumar,R.A.Gupta,S.V.Bhangale, "indirect vector controlled induction motor drive with fuzzy logic based intelligent controller," IETECH Journals of Electrical Analysis, vol. 2, no. 4, pp. 211-216, 2008.

Grid-Connected PV Array with Supercapacitor Energy Storage System for Fault Ride Through

ABSTRACT:

A fault ride through, power management and control strategy for grid integrated photovoltaic (PV) system with supercapacitor energy storage system (SCESS) is presented in this paper. During normal operation the SCESS will be used to minimize the short term fluctuation as it has high power density and during fault at the grid side it will be used to store the generated power from the PV array for later use and for fault ride through. To capture the maximum available solar power, Incremental Conductance (IC) method is used for maximum power point tracking (MPPT). An independent P-Q control is implemented to transfer the generated power to the grid using a Voltage source inverter (VSI). The SCESS is connected to the system using a bi-directional buck boost converter. The system model has been developed that consists of PV module, buck converter for MPPT, buck-boost converter to connect the SCESS to the DC link. Three independent controllers are implemented for each power electronics block. The effectiveness of the proposed controller is examined on Real Time Digital Simulator (RTDS) and the results verify the superiority of the proposed approach.

KEYWORDS:

1.      Active and reactive power control

2.      Fault ride through

3.      MPPT

4.      Photovoltaic system

5.      RTDS Supercapacitor

6.      Energy storage

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Grid connected PV system with energy storage

 EXPECTED SIMULATION RESULTS:

Fig.2. Grid voltage after three phase fault is applied

Fig.3. PV array power P_PV with SCESS and with no energy storage

Fig.4. Grid active power P_g for a three phase fault with and without energy storage

Fig.5.SCESS power P_SC for the applied fault on the grid side

Fig.6. Grid reactive power Q_g during three phase fault

Fig.7. DC link voltage for the applied fault

Fig.8. PV array voltage V_PV during three phase fault

Fig.9. MPPT output voltage V_ref for the applied fault

CONCLUSION:

This paper presents grid connected PV system with supercapacitor energy storage system (SCESS) for fault ride through and to minimize the power fluctuation. Incremental conductance based MPPT is implemented to track the maximum power from the PV array. The generated DC power is connected to the grid using a buck converter, VSI, buck-boost converter with SCESS. The SCESS which is connected to the DC link controls the DC link voltage by charging and discharging process. A P-Q controller is implemented to transfer the DC link power to the grid. During normal operation the SCESS minimizes the fluctuation caused by change in irradiation and temperature. During a grid fault the power generated from the PV array will be stored in the SCESS. The SCESS supplies both active and reactive power to ride through the fault. RTDS based results have shown the validity of the proposed controller.

REFERENCES:

[1] T. Esram, P.L. Chapman, “Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques,” IEEE Transaction on Energy Conversion, vol.22, no.2, pp.439-449, June 2007

[2] J. M. Enrique, E. Durán, M. Sidrach-de-Cardona, and J. M. Andújar,“Theoretical assessment of the maximum power point tracking efficiency of photovoltaic facilities with different converter topologies,” Sol. Energy, vol. 81, no. 1, pp. 31–38, Jan. 2007.

[3] W. Xiao, N. Ozog, and W. G. Dunford, “Topology study of photovoltaic interface for maximum power point tracking,” IEEE Trans. Ind. Electron., vol. 54, no. 3, pp. 1696–1704, Jun. 2007.

[4] J. L. Agorreta, L. Reinaldos, R. González, M. Borrega, J. Balda, and L. Marroyo, “Fuzzy switching technique applied to PWM boost converter operating in mixed conduction mode for PV systems,” IEEE Trans. Ind. Electron., vol. 56, no. 11, pp. 4363– 4373, Nov. 2009.

[5] A.Schneuwly, “Charge ahead [ultracapacitor technology and applications]”, IET Power Engineering Journal, vol.19, 34-37, 2005.

Novel Development of A Fuzzy Control Scheme with UPFC’s For Damping of Oscillations in Multi-Machine Power Systems

ABSTRACT:

This paper presents a novel development of a fuzzy logic controlled power system using UPFCs to damp the oscillations in a FACTS based integrated multi-machine power system consisting of 3 generators, 3 transformers, 9 buses, 4 loads & 2 UPFCs. Oscillations in power systems have to be taken a serious note of when the fault takes place in any part of the system, else this might lead to the instability mode & shutting down of the power system. UPFC based POD controllers can be used to suppress the oscillations upon the occurrence of a fault at the generator side or near the bus side. In order to improve the dynamic performance of the multi-machine power system, the behavior of the UPFC based POD controller should be coordinated, otherwise the power system performance might be deteriorated. In order to keep the advantages of the existing POD controller and to improve the UPFC-POD performance, a hybrid fuzzy coordination based controller can be used ahead of a UPFC based POD controller to increase the system dynamical performance & to coordinate the UPFC-POD combination. This paper depicts about this hybrid combination of a fuzzy with a UPFC & POD control strategy to damp the electro-mechanical oscillations. The amplification part of the conventional controller is modified by the fuzzy coordination controller. Simulink models are developed with & without the hybrid controller. The 3 phase to ground symmetrical fault is made to occur near the first generator for 200 ms. Simulations are performed with & without the controller. The digital simulation results show the effectiveness of the method presented in this paper.

KEYWORDS:

1.      UPFC

2.      POD

3.      Fuzzy logic

4.      Coordination

5.      Controller

6.      Oscillations

7.      Damping

8.      Stability

9.      SIMULINK

10.  State space model

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 : A 3-machine, 9-bus interconnected power system model with 4-loads without the controllers

Fig. 2: A 3-machine, 9-bus interconnected power system model with 4-loads & 2 POD-UPFC & the fuzzy controller

EXPECTED SIMULATION RESULTS:

 Fig. 3 : Simulation result of power angle v/s time (without Fuzzy-POD-UPFC)

 Fig. 4 : Simulation result of power angle v/s time (with UPFC & fuzzy control)

Fig. 5 : Comparison of the simulation results of power angle v/s time (without UPFC & with UPFC & fuzzy control)

 CONCLUSION:

AFACTS based multi-machine power system comprising of 3 generators, 9 buses, 3 loads with and without the 2 Fuzzy-POD-UPFC controllers was considered in this paper. SIMULINK models were developed in MATLAB 7 with & without the Fuzzy- POD-UPFC controllers for the considered multi machine model in order to damp out the oscillations. The control strategy was also developed by writing a set of fuzzy rules. The fuzzy control strategy was designed based on the conventional POD-UPFC controller & put before the POD-UPFC in the modeling.

            The main advantage of putting the fuzzy coordination controller before the POD-UPFC in modeling is the amplification part of the conventional controller being modified by the fuzzy coordination unit, thus increasing the power system stability. Simulations were run in Matlab 7 & the results were observed on the scope. Graphs of power angle vs. time were observed with and without the controller. From the simulation results, it was observed that without the Fuzzy-POD-UPFC controller, the nine bus system will be having more disturbances, while we check the power angle on the first generator.

            There are lot of ringing oscillations (overshoots / undershoots) & the output takes a lot of time to stabilize, which can be observed from the simulation results. But, from the incorporation of the Fuzzy- POD-UPFC coordination system in loop with the plant gave better results there by reducing the disturbances in the power angle and also the post fault settling time also got reduced a lot. The system stabilizes quickly, thus damping the local mode oscillations and reducing the settling time immediately after the occurrence of the fault.

            The developed control strategy is not only simple, reliable, and may be easy to implement in real time applications. The performance of the developed method in this paper thus demonstrates the damping of the power system oscillations using the effectiveness of Fuzzy-POD-UPFC coordination concepts over the damping of power system oscillations without the Fuzzy-POD-UPFC coordination scheme.

REFERENCES:

[1]. L. Gyugi, “Unified Power flow concept for flexible AC transmission systems”, IEE Proc., Vol. 139, No. 4, pp. 323–332, 1992.

[2]. M. Noroozian, L. Angquist, M. Ghandari, and G. Anderson, “Use of UPFC for optimal power flow control”, IEEE Trans. on Power Systems, Vol. 12, No. 4, pp. 1629–1634, 1997.

[3]. Nabavi-Niaki and M.R. Iravani, “Steady-state and dynamic models of unified power flow controller (UPFC) for power system studies”, IEEE’96 Winter Meeting, Paper 96, 1996.

[4]. C.D. Schauder, D.M. Hamai, and A. Edris. “Operation of the Unified Power Flow Controller (UPFC) under Practical constraints”, IEEE Trans. On Power Delivery, Vol. 13, No. 2. pp. 630~639, Apr. 1998.

[5]. Gyugyi, L., “Unified power flow controller concept for flexible AC transmission systems”, IEE Proc. Gener. Transm. Distrib., No.139, pp. 323-331, 1992