PMSG with Inverter using Park's Transformation for Transient Fault Analysis

Transcription

1 IJSRD - International Journal for Scientific Research & Development Vol. 3, Issue 03, 2015 ISSN (online): PMSG with Inverter using Park's Transformation for Transient Fault Analysis Abhishek M. Patel 1 Dr. Jatin J. Patel 2 1 Student of M. Tech (Power system) 2 Professor 1,2 Department of Electrical Engineering 1,2 G H Patel Collage of Engineering & Technology, V.V.Nagar, India Abstract The Development of power electronic devices change the definition of control strategies of wind generation of the world. As transient stability analysis of VSWT-PMSG is required to meet the new wind grid code. In this paper we focuses on the suitable control strategies are developed for grid side inverter. The proposed control strategy can provide maximum power to grid and can also control the reactive power to maintain terminal voltage of grid is constant. symmetrical and unsymmetrical faults is analyses for network disturbance at two different locations of the transmission line. The proposed system is develop in MATLAB SIMULINK TOOLBOX. Key words: VSWT-PMSG, FACTS I. INTRODUCTION Wind Energy has continued its growth worldwide in these years MW were added in 2006, resulting in the total installed capacity of MW in the world by the end of December 2006 [1]. Therefore, it is needed to analyse the transient characteristic of wind turbine generator system (WTGS) as a huge number of wind generators will be connected with the existing network in the near future. With the current rapid industrial development in the world, energy shortage has become one of the biggest issues many countries are facing. As a consequence of rising fossil fuel price and advanced technology, more and more homes and businesses have been installing small wind turbines for the purposes of cutting energy bills and carbon dioxide emissions, and are even selling extra electricity back to the national grid. In small wind energy sector, INDIA has become the fifth largest market in the world. There are a large number of small wind turbines that have been installed in the INDIA between 2005 and By 2008, the total capacity of wind turbine generation had reached MW [2]. The INDIA is not only a big market for wind small turbines, but also has many manufactures of small wind turbines, with about 20% of world s small wind turbines made in the INDIA[3]. Fast development of wind power generation has led to the requirements for integration of wind farm into the network without compromising power system stability. Grid operators require wind farms to remain connected stably to the network during severe grid faults and to support the grid restoration by supplying ancillary services, especially in places where wind turbines provide a significant part of the total power [4].Various wind turbine concepts have been developed to maximize annual energy capture, minimize cost, improve power quality, and ensure safety together with the growth of wind energy. Historically, a SCIG wind turbine had been widely used in commercial because of its advantages such as rugged construction, low cost, brushless, operational simplicity maintenance free, easy and relatively cheap mass production. It also operates at a constant rotating speed when it is connected to a large grid, providing stable frequency control. However, with an increasing penetration level of wind turbines, the market share of SCIG wind turbines has decreased because it require large reactive power to recover flux in short circuit fault condition. It has poor capabilities to meet the new challenges of the grid connection requirements and makes it difficult to support grid voltage control. On the other hand, variable speed operation of wind turbines draws lots of attention due to the high ability of complying with grid requirements especially in case of PMSG wind turbine with a full-scale converter. Because of its full-scale converter, it can absorb or supply a large amount of reactive power to the grid. When a fault occurs, the grid-side converter can provide reactive power up to its rated value to help ride through the fault[5]. Voltage or current source inverter based flexible AC transmission system (FACTS) devices such as Thyristor Controlled Reactor (TCR), Thyristor Controlled Switched Reactor (TCSR), Static VAR Compensator (SVC) or Fixed Capacitor Thyristor Controlled Reactor (FC-TCR),Thyristor Controlled Series Capacitor (TCSC), Thyristor Controlled Switched Series Reactor (TSSR), Thyristor Controlled Brakening Reactor (TCBR), Thyristor Controlled Voltage Reactor (TCVR), Thyristor Controlled Voltage Limiter (TCVL Thyristor Controlled Switched Series (TSSC),Thyristor Controlled Phase Angle Regulator (TC- PAR) or Thyristor Controlled Phase Shift Transformer (TC- PST),Static Synchronous Series Compensator (SSSC), Static Synchronous Compensator (STATCOM), Distributed Static Synchronous Compensator (D-STATCOM), Generalized Unified Power Flow Controller (GUPFC), Unified Power Flow Controller (UPFC), Interlink Power Flow Controller (IPFC), Generalized Interlink Power Flow Controller (GIPFC),and Hybrid Power Flow Controller (HPFC), Semiconductor Magnetic Energy Storage (SMES), Battery Energy Storage (BESS),have been used for flexible power flow control, secure loading and damping of power system oscillation[6]. However, the installation of FACTS devices at a wind farm composed of fixed speed wind generators increases the overall cost. On the other hand, variable speed WTGS equipped with full or partial rating power electronic converter has comparatively strong fault ride through capability. Moreover, it can extract the maximum power from the wind due to its variable speed operation. Therefore, the use of variable speed WTGS has been becoming very popular these days. On the other hand, variable speed operation of wind turbines draws lots of attention due to the high ability of complying with grid requirements especially in case of PMSG wind turbine with a full-scale converter. All rights reserved by

2 Because of its full-scale converter, it can absorb or supply a large amount of reactive power to the grid. When a fault occurs, the grid-side converter can provide reactive power up to its rated value to help ride through the fault[7]. In this paper, transient characteristics of VSWT- PMSG are analyse considering a frequency converter[8]. In the model system used in this paper, a PMSG wind generator is connected to the power system network through a fully controlled frequency converter composed of uncontrolled rectifier and grid-side DC/AC inverter. The detailed control schemes of both converter/inverter are presented. Simulation analyses have been performed by using MATLAB SIMULINK TOOLBOX, in which the PMSG, electrical network, both converter/inverter, and their controllers are implemented by using its standard library models. Transient performance of the control system is verified considering different types of symmetrical and unsymmetrical faults occurred at several locations in the model system. Finally, it is reported that the proposed control strategy enhances well the transient stability of VSWT driving a PMSG. II. MODEL SYSTEM The proposed model system used for the Transient analysis is shown in Fig.1. Here, one PMSG is connected to an infinite bus through the generator side converter, DC-link capacitor, grid side inverter, transformer, and double circuit transmission line. A. PMSG: Fig. 1: Model System Layout III. INDIVIDUAL COMPONENT MODELING In the simulation analyses, the PMSG model available in the package software MATLAB SIMULINK is used. The nominal speed is considered as the maximum rotor e rotor speed exceeds the maximum rotor speed. Rated Power 5 [MW] Stator Resistance 0.425[ ] Rated Voltage 392[V] Armature Reactance an internal DC-Link modelled as a capacitor and a PWM inverter. Each of converter/inverter is a standard three-phase two-level unit, composed of six IGBTs and anti parallel diodes. The layout of the electric part is depicted in the following figure2. The design procedures for various parts are explained in detail in the following sections. Fig. 2: Electrical Scheme of VSWT-PMSG Control blocks for the grid side inverter are shown in Fig.3 which is based on the cascaded control scheme. The dq quantities and three-phase electrical quantities are related to each other by a reference frame transformation. The angle of the transformation is detected from the three phase voltages (va,vb,vc) at the high-voltage side of the grid side transformer. The DC voltage of the DC-link capacitor is controlled constant by two PI controllers. The d-axis current can control the DC-link voltage. On the other hand, the q- axis current can control the reactive power of the grid side inverter. The reactive power reference is set that the terminal voltage at the high-voltage side of the transformer remains constant. Therefore, three PI controllers are used to control the reactive power of the grid side inverter. The additional PI controller provides excellent transient characteristics during network disturbance, as shown later. In inverter, the triangular carrier signal is used as the carrier wave of PWM operation. The carrier frequency chosen is 1050 Hz for the inverter, respectively. The DClink capacitor value chosen is PF. The rated DC-link voltage is 400V. Table 2: Parameters of PI Controllers Used In Grid-Side Inverter Frequency 20 [Hz] Field Flux 1.55[pu] Pole pairs 5 H 3.0 [sec] Table 1: Generator Parameters B. VSWT-PMSG with Converter-DC Link-Inverter Topology: The system analyzed is a wind turbine based on PMSG. Due to the low generator speed, the rotor shaft is coupled directly to the generator, which means that no gearbox is needed. The generator is connected to the grid via an AC/DC/AC converter, which consists of an uncontrolled diode rectifier, All rights reserved by

3 Fig. 3: Simulation Block Diagram of Grid Side Inverter A symmetrical three-line-to-ground fault, 3LG, and an unsymmetrical double-line- to-ground fault, 2LG (phases B, C, and ground) are considered network distur- bances each occurs at different fault points of the transmission line, as shown in Fig.3. The fault occurs at 0.1 sec, the circuit breakers (CB) on the faulted lines are opened at 0.2 sec, and at 0.9 sec the circuit breakers are re-closed. In the transient stability analysis, the wind speed is kept constant at the rated speed at which the PMSG reference power is at the rated level, assuming that the wind speed doesn t change dramatically within this small time duration. The time step and simulation time have been chosen as sec and 1sec, respectively. Simulations were done by using MATBLAB SIMULINK. For detailed transient stability analysis of VSTW-PMSG, two cases are considered as described below. The Matlab simulink based model for the transient stability analysis of the VSWG-PMSG is shown in Fig.4. Fig. 4: Matlab Simulation Model level, as shown in Fig.6. The response of the DC-link voltage is shown in Fig.6. From the simulation results, it is seen that the proposed control system can enhance the transient stability of the VSWT-PMSG when a 3LG fault occurs far from the wind generator. Fig. 5: Matlab Simulation Model (Subsystem) C. CASE-I: In this case, a 3LG fault is considered to occur at the middle of one transmission line (fault point F1) of Fig. 5. The grid side inverter can provide the necessary reactive power during the network disturbance, as shown in Fig. 6. Therefore, the terminal voltage can return to its pre-fault All rights reserved by

4 Fig. 6: System Parameter Waveforms (L-L-L-G) D. CASE-II: In this case, an unsymmetrical 2LG fault is considered to occur at the middle of one transmission line (fault point F2) of Fig.5. The responses of the grid side reactive power, terminal voltage of the grid, real power, and DC-link voltage are shown in Fig.7, respectively. From the simulation results, it is clear that the proposed control system can also enhance the transient stability of a VSWT-PMSG under unsymmetrical faultcondition. Fig. 7: System Parameter Waveforms (L-L-G) Fault Voltage(V) Reactive power(mvar) Current At Middle of transmission line L-L-L-G A=6520 B=6526 C= A=2163 B=2171 C=2161 L-L-G L-L-L-G L-L-G A=9854 B=6521 C= At Sending end side of transmission line A=7258 B= C=7230 A=9854 B=6521 C= Table 3: Results A=3.095 B=1960 C=1909 A=1799 B=1797 C=1797 A=5.111 B=1627 C=1576 IV. CONCLUSION This paper presents a detailed study of the transient stability of the variable speed wind turbine driving a PMSG when a network disturbance occurs in the power system. Frequency converter topology suitable for the VSWT-PMSG are presented. Then the modelling and control strategy for the generator and frequency converters are presented. The proposed control strategies can provide maximum power to the grid and can also control the reactive power to maintain the terminal voltage of the grid constant. These control strategies are suitable for improving the transient characteristics, where necessary reactive power is supplied, depending on the grid terminal voltage. Finally, symmetrical and unsymmetrical faults are considered as the network disturbances. It is found that a fault occurring near the generator side converter is more severe than a fault occurring far from the generator. Finally, it can be concluded that the proposed control system can All rights reserved by

5 increase the low voltage ride through (LVRT) capability of the VSWT-PMSG and thus the wind generator shutdown phenomenon during network disturbances can be decreased. REFERENCES [1] World Wind Energy Association (WWEA), Wind Energy International 2014, WWEA, Germany, [2] World wind energy report 2013, World Wind Energy Association,at: /world wind energy report 2013 s pdf. [3] "Global Wind Report Annual Market Update 2013" (PDF). Global Wind Energy Council. Retrieved23 April [4] P.J. Musgrove, Wind energy conversion an introduction, IEE Proceedings on Physical Science, Measurement and Instrumentation, Management and Education, Reviews, vol. 130, no.9, pp , [5] S.M. Muyeen, R. Takahashi, T. Murata, and J. Tamura, " Low Voltage Ride Through Capability Enhancement of Fixed Speed Wind Generator".2009 IEEE Bucharest Power Tech Conference, June 28th - July 2nd, Bucharest, Romania. [6] Bindeshwar Singh, K.S. Verma, Pooja Mishra, Rashi Maheshwari, Utkarsha Srivastava, and Aanchal Baranwal,"Introduction to FACTS Controllers: A Technological Literature Survey", International Journal of Automation and Power Engineering Volume 1 Issue 9, December [7] Thi-Hoa Truong* and Kyoung-Soo Ro, "Improvement of LVRT Characteristic of SCIG Wind Turbine System by Incorporating PMSG", International Journal of Energy, Information and Communications Vol. 3, Issue 3, August, [8] S. M. Muyeen, R. Takahashi, T. Murata, and J. Tamura,"Transient Stability Enhancement of Variable Speed Wind Turbine Driven PMSG with Rectifier- Boost Converter-Inverter", Proceedings of the 2008 International Conference on Electrical Machines. [9] B. K. Bose, Power Electronics and Motor Drives Recent Progress and Perspective, IEEE Transactions on Industrial Electronics, vol. 56, no. 2 pp , [10] T. Thiringer, J. Linders, Control by Variable Rotor Speed of a Fixed-Pitch Wind Turbine Operating in a Wide Speed Range, IEEE Transactions on Energy Conversion, vol. 8, no. 3, pp , [11] P.S. Bimbhra, Generalized Theory of Electric Machines, Khanna Publishers,2002. [12] Marwa Ezzat, Mohamed Benbouzid, S.M. Muyeen and Lennart Harnefors," Low-Voltage Ride-Through Techniques for DFIG-Based Wind Turbines:State-ofthe-Art Review and Future Trends" IEEE IECON 2013, Vienne : Austria (2013) [13] S.M. Muyeen, R. Takahashi, T. Murata, and J. Tamura, " Low Voltage Ride Through Capability Enhancement of Fixed Speed Wind Generator".2009 IEEE Bucharest Power Tech Conference, June 28th - July 2nd, Bucharest, Romania [14] S. M. Muyeen, Rion Takahashi,Toshiaki Murata, and Junji Tamura, " A Variable Speed Wind Turbine Control Strategy to Meet Wind Farm Grid Code Requirements", IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 25, NO. 1, FEBRUARY 2010 [15] S. M. Muyeen and Ahmed Al-Durra, " Modelling and Control Strategies of Fuzzy Logic Controlled Inverter System for Grid Interconnected Variable Speed Wind Generator", IEEE SYSTEMS JOURNAL, VOL. 7, NO. 4, DECEMBER 2013 [16] L. Tang, R. Zavadil, Shunt Capacitor Failures Due to Wind Farm Induction Generator Selfexcitation Phenomenon IEEE Transactions on Energy Conversion, vol.8, no. 3, pp , [17] E.Rajendran, Dr.C.Kumar, G.Ponkumar" LVRT Scheme of Wind Power System using PMSG and Sinusoidal Pulse Width Modulation" International Journal of Engineering Science and Innovative Technology (IJESIT) Volume 2, March 2013 [18] Rajveer Mittal, K.S.Sandhu, D.K.Jain'" LVRT of Grid Interfaced Variable Speed Driven PMSG for WECS during Fault",International Journal of Computer and Electrical Engineering, Vol. 1, No. 4, October, 2009, [19] D Mary, Shinosh Mathew, Sreejith K," Modelling and Simulation of Grid Connected Wind Energy System", International Journal of Soft Computing and Engineering (IJSCE) ISSN: , Volume-3, Issue-1, March 2013 [20] INDIAN WIND GRID CODE, by CENTRE FOR WIND ENERGY TECHNOLOGY CHENNAI. [21] L. Zhang, C. Shen, M. L. Crow, L. Dong, S. Pekarek, and S. Atcitty, Performance Indices for the Dynamic Performance of FACTS and FACTS with Energy Storage, Electric Power Component and System, vol.33, no.3, pp , March [22] R. Takahashi, J. Tamura, M. Futami, M. Kimura, and K. Ide, A New Control Method for Wind Energy Conversion System Using a Double-Fed Synchronous Generator, IEEJ Power and Energy, Vol.126, No.2, pp , 2006 (In Japanese). [23] S.K.Salman and Anita L.J.Teo, Windmill Modeling Consideration and Factors Influencing the Stability of a Grid-Connected Wind Power-Based Embedded Generator, IEEE Trans. on Power Systems, Vol.18, No.2, p , [24] [20] S. M. Muyeen, Mohd. Hasan Ali, Rion Takahashi, Toshiaki Murata, and Junji Tamura, Transient Stability Enhancement of Wind Generator by a New Logical Pitch Controller, IEEJ Trans.PE., Vol.126-B, No.08, pp , All rights reserved by