Synchronization and Reactive Current Support of PMSG based Wind Farm during Severe Grid Fault

ABSTRACT:

Grid codes require wind farm to remain on-grid and inject specific reactive current when grid fault occurs. To satisfy the requirements, reactive power devices such as the static synchronous compensator (STATCOM) are usually used in modern wind farms. In order to produce reactive currents, the wind energy generation system (WECS) and the STATCOM are normally controlled with the phase locked loop (PLL)-oriented vector control methods. Due to the active power imbalance between the generation and consumption, the wind farm has the risk of losing synchronization with the grid under severe fault conditions. This paper analyzes the dynamic synchronization mechanism and stability criteria of the wind farm and proposes a coordinated current control scheme for the WECS and the STATCOM during severe grid fault period. The synchronization stability of both the WECS and the STATCOM is remained by the active power balancing control of the wind farm. The control objectives of the generator- and grid-side converters for the WECS are swapped to avoid the interaction between the dc-link voltage control loop and the synchronization loop. The synchronized STATCOM produces additional reactive currents to help the wind farm meet the requirements of the grid code. Effectiveness of the theoretical analyses and the proposed control method are verified by simulations.

 

KEYWORDS:

  1. Low voltage ride through (LVRT)
  2. Permanent magnet synchronous generator (PMSG)
  3. Wind farm
  4. Coordinated current control

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

Fig. 1. Configuration of the PMSG-based wind farm

  

EXPECTED SIMULATION RESULTS:

Fig. 2. System response of the PMSG-based wind farm with conventional control strategy during severe fault

Fig. 3. System response of the PMSG-based wind farm with proposed strategy during severe fault

 

CONCLUSION:

This paper studied the LOS mechanism and the coordinating LVRT scheme of the PMSG based wind farm when severe grid voltage dip occurs. The following conclusions can be derived from the theoretical analyses and simulation verification:

(1) Variable-speed wind turbines and STATCOM both have the LOS risk when the grid voltage dip is severe.

(2) The proposed active power balancing control scheme which relies on the frequency dynamic of the PLL can achieve the synchronization stability of the WECS. However, reactive current capability of the WECS would be sacrificed to implement such scheme.

(3) The coordinated current control between the PMSG based WECS and the STATCOM can achieve both the synchronization stability and the reactive current support according to the grid code under severe grid fault. The analysis results and proposed scheme are also available for the LVRT of other renewable energy conversion systems.

(4) It should be pointed out that this paper focuses on the symmetrical fault conditions. In practical applications, unsymmetrical faults occur more often than symmetrical ones. Some Europe grid codes, such as “VDE-AR-N 4120” code in Germany, are requiring the WECS to provide negative sequence current compensation during unsymmetrical fault period. In such cases, the advanced PLL, such as the second order generalized integrator (SOGI) PLL [31], should be employed to separate the positive and negative sequence components from the grid voltage. The advanced PLLs have much more complicated structures and models compared with the conventional one as indicated in this paper. Also the synchronization stability should be discussed in both positive and negative sequences. By further considering the coupling of the PLL and control loops during grid faults similarly with the case discussed in this paper, the synchronization issue would be more complicated. More studies are expected in this issue and would be our future work.

 

REFERENCES:

  • BDEW Technical Guideline, Generating Plants Connected to the Medium- Voltage Network [EB/OL], June 2008 issue.
  • Grid code-high and extra high voltage, E. ON Netz GmbH, 2006. Tech. Rep., [EB/OL].
  • Geng, C. Liu and G. Yang. LVRT Capability of DFIG-Based WECS Under Asymmetrical Grid Fault Condition [J]. IEEE Transactions on Industrial Electronics, vol. 60, no. 6, pp. 2495-2509, June 2013.
  • Chinchilla M., Arnaltes S., Burgos J. C. Control of permanent-magnet generators applied to variable-speed wind-energy systems connected to the grid [J]. IEEE Transactions on Energy Conversion, 2006, 21(1): 130-5.
  • Conroy J. F., Watson R. Frequency Response Capability of Full Converter Wind Turbine Generators in Comparison to Conventional Generation [J]. IEEE Transactions on Power Systems, 2008, 23(2): 649-56.

Control of permanent magnet synchronous generator-based stand-alone wind energy conversion system

ABSTRACT:

This study deals with an implementation of a constant speed permanent magnet synchronous generator (PMSG)-based three-phase stand-alone wind energy conversion system (SWECS). The voltage and frequency controller is realised using only a single voltage source converter (VSC) and a battery energy storage system (BESS). The BESS is used to provide load leveling under varying wind speeds and to control frequency of SWECS. The voltage of PMSG is regulated under varying wind speeds and loads by supplying the reactive power from VSC. The performance of SWECS is demonstrated as a load leveller, a load balancer, a harmonic compensator and a voltage and frequency controller.

 

SOFTWARE: MATLAB/SIMULINK

  

CIRCUIT DIAGRAM:

Fig. 1 Proposed system configurations of VFC for PMSG-based SWECS

a System configuration of VFC for PMSG-based 3P3W SWECS

b System configuration of VFC for PMSG-based 3P4W SWECS

  

EXPECTED SIMULATION RESULTS:

Fig. 2 Simulated performance of VFC under fall in wind speed (12 –10 m/s) at fixed balanced linear loads

Fig. 3 Simulated performance of VFC under rise in wind speed (10 –12 m/s) at balanced linear loads

 

CONCLUSION:

A VFC for a PMSG in stand-alone WECS has been designed, modelled and developed for feeding three-phase consumer loads. The VFC has been realised using a VSC and a battery energy storage system. A new control strategy for VFC has been realised using IcosF algorithm and implemented for PMSG-based SWECS. The performance of VFC has been found satisfactory under varying wind speeds and loads. The VFC has performed the functions of load leveller, load balancer and a harmonic eliminator along with VFC.

REFERENCES:

  • Patel, M.R.: ‘Wind and solar power systems’ (CRC Press, Washington, DC, 2006, 2nd edn.)
  • David, S.B., Jenkins, N., Bossanyi, E.: ‘Wind energy handbook’ (John Wiley & Sons. Ltd., 2001)
  • Simoes, M.G., Farret, F.A.: ‘Renewable energy systems’ (CRC Press, Florida, 2004)
  • Lai, L.L., Chan, T.F.: ‘Distributed generation -induction and permanent magnet generators’ (John Wiley and Sons Ltd., 2007
  • Heier, S.: ‘Grid integration of wind energy conversion systems’ (Wiley, New York, 1998)

Control of a Stand Alone Variable Speed Wind Turbine with a Permanent Magnet Synchronous Generator

ABSTRACT:

A novel control strategy for the operation of a permanent magnet synchronous generator (PMSG) based stand alone variable speed wind turbine is presented in this paper,. The direct drive PMSG is connected to the load through a switch mode rectifier and a vector controlled pulse width modulated (PWM) IGBT-inverter. The generator side switch mode rectifier is controlled to achieve maximum power from the wind. The load side PWM inverter is using a relatively complex vector control scheme to control the amplitude and frequency of the inverter output voltage. As there is no grid in a stand-alone system, the output voltage has to be controlled in terms of amplitude and frequency. The stand alone control is featured with output voltage and frequency controller capable of handling variable load. A damp resistor controller is used to dissipate excess power during fault or over-generation. The potential excess of power will be dissipated in the damp resistor with the chopper control and the dc link voltage will be maintained. Extensive simulations have been performed using Matlab/Simpower. Simulation results show that the controllers can extract maximum power and regulate the voltage and frequency under varying load condition. The controller performs very well during dynamic and steady state condition.

  

KEYWORDS:

  1. Permanent magnet synchronous generator
  2. Maximum power extraction
  3. Switch-mode rectifier
  4. Stand alone variable
  5. Speed wind turbine
  6. Voltage and frequency control

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

Figure 1.Control Structure of a PMSG based standalone variable speed wind turbine.

 

EXPECTED SIMULATION RESULTS:

 

Figure 2. Response of the system for a step change of wind speed from 10 m/s to 12 m/s to 9 m/s to 10 m/s.

Figure 3. Voltage and current responses at a constant load.

Figure 4. Frequency response, DC link voltage and modulation index at a constant load.

Figure 5. Voltage and current responses when load is reduced by 50%.

Figure.6. Frequency response, DC link voltage and modulation index when load is reduced by 50%.

 

CONCLUSION:

Control strategy for a standalone variable speed wind turbine with a PMSG is presented in this paper. A simple control strategy for the generator side converter to extract maximum power is discussed and implemented using Simpower dynamic system simulation software. The controller is capable to maximize output of the variable speed wind turbine under fluctuating wind. The load side PWM inverter is controlled using vector control scheme to maintain the amplitude and frequency of the inverter output voltage. It is seen that the controller can maintain the load voltage and frequency quite well at constant load and under varying load condition. The generating system with the proposed control strategy is suitable for a small scale standalone variable speed wind turbine installation for remote area power supply. The simulation results demonstrate that the controller works very well and shows very good dynamic and steady state performance

 

REFERENCES:

  • Müller, S., Deicke, M., and De Doncker, Rik W.: ‘Doubly fed induction genertaor system for wind turbines’, IEEE Industry Applications Magazine, May/June, 2002, pp. 26-33.
  • Polinder, F. F. A. van der Pijl, G. J. de Vilder, P. J. Tavner, “Comparison of direct-drive and geared generator concepts for wind turbines,” IEEE Trans. On energy conversion, vol . 21, no. 3, pp. 725-733, Sept. 2006.
  • F. Chan, L. L. Lai, “Permanenet-magnet machines for distributed generation: a review,” in proc. 2007 IEEE power engineering annual meeting, pp. 1-6.
  • De Broe, S. Drouilhet, and V. Gevorgian, “A peak power tracker for small wind turbines in battery charging applications,” IEEE Trans. Energy Convers., vol. 14, no. 4, pp. 1630–1635, Dec. 1999.

Battery Energy Storage System for Variable Speed Driven PMSG for Wind Energy Conversion System

ABSTRACT:

There are many loads such as remote villages, islands, etc. that are located far away from the main grid. These loads require stand-alone generating system, which can provide constant voltage and frequency for local electrification. Locally available wind power can be used in such off-grid systems. As the wind speed is variable, an AC-DC-AC conversion system is required to convert variable voltage and variable frequency power generation to constant voltage and constant frequency source. Further, as the wind power as well as load is variable there is a need of energy storage device that take care of the load mismatch. In this paper, a standalone wind energy conversion system (WECS) using a variable speed permanent magnet synchronous generator (PMSG) is proposed with a battery energy storage system.

KEYWORDS:

  1. Wind energy conversion system
  2. Isolated system
  3. BESS
  4. Permanent magnet synchronous generator

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig.1 PMSG with PWM rectifier with battery for storing the extra wind energy

EXPECTED SIMULATION RESULTS:

 Fig.2. Variation of wind speed, load voltages, load currents, generator power, battery power, load power battery current and DC link voltage.

 CONCLUSION:

The isolated operation of wind energy conversion system requires AC-DC-AC interface with the capability of converting variable voltage variable frequency to constant voltage constant frequency source. In addition the power balancing has to be done with some energy storage system, According to the proposed topology, battery energy storage system provides power balance between the generated power and the load. The power mismatch is absorbed by the BESS.

REFERENCES:

[1] Bhim Singh and Gaurav Kumar Kasal, “Solid-State Voltage and Frequency Controller for a stand alone wind power generating system,” IEEE Trans. Power Electronics, vol. 23, no.3, pp.1170–1177, 2008.

[2] Bhim Singh and Gaurav Kumar Kasal, “Voltage and Frequency Controller for a 3-Phase 4-Wire Autonomous Wind Energy Conversion System” accepted for publication in IEEE Trans. on Energy Conversion.

[3] Ghosh and G. Ledwich, Power Quality Enhancement Using Custom Power Devices. Kulwer Academic, 2002.

[4] Gipe, P. Wind power’, Chelsea Green Publishing Company, Post Mills, Vermount, USA,1995.

[5] Rai, G.D. (2000) ‘Non conventional energy sources’, Khanna Publishers, 4th Edition, New Delhi (India)

An Autonomous Wind Energy Conversion System with Permanent Magnet Synchronous Generator

ABSTRACT:

This paper deals with a permanent magnet synchronous generator (PMSG) based variable speed autonomous wind energy conversion system (AWECS). Back back connected voltage source converter (VSC) and a voltage source inverter (VSI) with a battery energy storage system (BESS) at the intermediate dc link are used to realize the voltage and frequency controller (VFC). The BESS is used for load leveling and to ensure the reliability of the supply to consumers connected at load bus under change in wind speed. The generator-side converter operated in vector control mode for achieving maximum power point tracking (MPPT) and to achieve unity power factor operation at PMSG terminals. The load-side converter is operated to regulate amplitude of the load voltage and frequency under change in load conditions. The three-phase four wire consumer loads are fed with a non-isolated star-delta transformer connected at the load bus to provide stable neutral terminal. The proposed AWECS is modeled, design and simulated using MATLAB R2007b simulink with its sim power system toolbox and discrete step solver.

KEYWORDS:

  1. Battery
  2. Permanent Magnet Synchronous Generator
  3. Star-delta Transformer
  4. Voltage Source Converters
  5. Maximum Power Point Tracking
  6. Wind Energy

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

Fig. 1 Proposed control scheme of VFC for PMSG based AWECS

 EXPECTED SIMULATION RESULTS:

 

 Fig. 2 Performance of Controller during fall in wind speed

Fig. 3 Performance of Controller during rise in wind speed

Fig. 4 Performance of Controller at fixed wind speed and balanced/unbalanced non-linear loads

CONCLUSION:

 A new configuration of voltage and frequency controller for a permanent magnet synchronous generator based variable speed autonomous wind energy conversion system has been designed modeled and its performance is simulated. The VFC has used two back-back connected VSC’s and BESS at intermediate dc link. The GSC has been controlled in vector controlled to achieve MPPT, unity power factor operation of PMSG. The LSI has been controlled to maintain amplitude of load voltage and its frequency. The VFC has performed the function of a load leveler, a load balancer, and a harmonic eliminator.

REFERENCES:

[1] J. F. Gieras and M. Wing, Permanent Magnet Motor Technology – Design and Application, Marcel Dekker Inc., New York, 2002.

[2] M. Kimura, H. Koharagi, K. Imaie, S. Dodo, H. Arita and K. Tsubouchi, “A permanent magnet synchronous generator with variable speed input for co-generation system,” IEEE Power Engineering Society Winter Meeting, 2001, vol. 3, 28 Jan.-1 Feb. 2001, pp. 1419 – 1424.

[3] T.F. Chan, L.L. Lai, Yan Lie-Tong, “Performance of a three-phase AC generator with inset NdFeB permanent-magnet rotor,” IEEE Trans. Energy Conversion, vol.19, no.1, pp. 88- 94, March 2004.

[4] T.F. Chan, W. Wang, L.L. Lai, “Analysis and performance of a permanent-magnet synchronous generator supplying an isolated load,” IET, Electric Power Applications, vol. 4, no. 3, pp.169-176, March 2010.

[5] K. Amei, Y. Takayasu, T. Ohji and M. Sakui, “A maximum power control of wind generator system using a permanent magnet synchronous generator and a boost chopper circuit,” Proc. of the Power Conversion Conference, PCC Osaka 2002, vol. 3, 2-5 April 2002, pp. 1447 – 1452.

A Unified Nonlinear Controller Design for On-grid/Off-grid Wind Energy Battery-Storage System

ABSTRACT:

The goal of this paper is to investigate the application of nonlinear control technique to a multi-input multi output (MIMO) nonlinear model of a wind energy battery storage system using a permanent magnet synchronous generator (PMSG). The challenge is that the system should operate in both grid-connected and standalone modes while ensuring a seamless transition between the two modes and an efficient power distribution between the load, the battery and the grid. Our approach is different from the conventional methods found in literature, which use a different controller for each of the modes. Instead, in this work, a single unified nonlinear controller is proposed. The proposed control system is evaluated in simulation. The results showed that the proposed control scheme gives high dynamic responses in response to grid power outage and load variation as well as zero steady-state error.

KEYWORDS:

  1. Battery storage
  2. Bi-directional buck-boost converter
  3. Feedback linearization
  4. Grid-connected
  5. Multi-input mutioutput
  6. Permanent magnet synchronous generator
  7. Stand-alone
  8. Wind turbine

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

Fig. 1. WECS based permanent magnet synchronous generator.

 EXPECTED SIMULATION RESULTS:

 

Fig. 2. Optimum Rotor Speed and Output Power.

Fig. 3. Voltage and current of the load.

Fig. 4. dc-link voltage.

Fig. 5. Wind Turbine Output Power (MW).

Fig. 6. Load Power (MW).

Fig. 7. Charge/discharge of Battery (%).

Fig. 8. Grid Power (MW).

CONCLUSION:

This paper has proposed a nonlinear MIMO controller based on the feedback linearization theory to regulate the load voltage in both grid-connected and stand-alone mode while ensuring a seamless transition between the two modes and an efficient power distribution between the load, the battery and the grid. Our approach is different from the conventional methods found in literature, which use a different controller, PID based, for each mode of operation. Instead, in this work, a single unified nonlinear controller is proposed. The performance of the proposed controller has been tested with different wind speeds as well as in the two modes of operation with dynamic load. The simulation results show that applying nonlinear feedback linearization based control strategy provides a good control performance. This performance is characterized by fast and smooth transient response as well as good steady state stability and reference tracking quality, even with variable wind speed and dynamic load operation. However, this study assume that the system parameters are fixed. A future work will be to test the system when parameters are unknown using adaptive control design theory.

REFERENCES:

[1] M. Fatu, F. Blaabjerg, and I. Boldea, “Grid to standalone transition motion-sensorless dual-inverter control of pmsg with asymmetrical grid voltage sags and harmonics filtering,” IEEE Transactions on Power Electronics, vol. 29, no. 7, pp. 3463–3472, Jul. 2014.

[2] M. Fatu, L. Tutelea, R. Teodorescu, F. Blaabjerg, and I. Boldea, “Motion sensorless bidirectional pwm converter control with seamless switching from power grid to stand alone and back,” in Power Electronics Specialists Conference, 2007. PESC 2007. IEEE. IEEE, 2007, pp. 1239–1244.

[3] R. Teodorescu and F. Blaabjerg, “Flexible control of small wind turbines with grid failure detection operating in stand-alone and grid-connected mode,” IEEE Transactions on Power Electronics, vol. 19, no. 5, pp. 1323–1332, Sept. 2004.

[4] T. Chaiyatham and I. Ngamroo, “Optimal fuzzy gain scheduling of pid controller of superconducting magnetic energy storage for power system stabilization,” International Journal of Innovative Computing, Information and Control, vol. 9, no. 2, pp. 651–666, 2013.

[5] N. Instruments, “Improving pid controller performance,” 2009.

A Modified Active Power Control Scheme for Enhanced Operation of PMSG Based WGs

ABSTRACT:

This paper emphasises the development of a simplified active power control scheme for enhanced operation of grid integrated permanent magnet synchronous generator (PMSG) based wind-driven generators (WGs). An active power reference generation scheme is proposed for the machine side converter (MSC) to inject active power into the grid even under grid disturbances, without violating system components rating. In this scheme, the controller employed for MSC adjusts the active power captured proportionate to the drop in the grid voltage upon considering wind speed and rotor speed. Furthermore, unlike dual vector control scheme, the grid side converter (GSC) controller is implemented in a positive synchronous frame (PSF) with the proposed current oscillation cancellation scheme to suppress the oscillations in dc-link voltage, active and reactive power of the grid and to obtain symmetrical sinusoidal grid current. Extensive analytical simulation has been carried out in PSCAD/ EMTDC to validate the superiority of proposed control scheme over the conventional schemes when WG is subjected to various grid disturbances. The reduced percentage of oscillation in the system parameters such as dc-link voltage and grid active power confirms the efficacy of the proposed method when compared with the conventional control techniques.

KEYWORDS:

  1. Fault ride through
  2. Grid disturbances
  3. Positive synchronous frame
  4. Permanent magnet synchronous generator
  5. Wind-driven generator

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 Fig.1 PMSG based grid integrated WG.

 EXPECTED SIMULATION RESULTS:

 

Fig.2 Behavior of PMSG based WG during step change in wind speed (a) wind speed profile, m/s; (b) rotor speed, rad/s; (c) dc-link voltage, V; (d) grid active power, W; (f) grid current, A.

 Fig.3 Performance evaluation of proposed controller for the voltage profile of IEGC during symmetrical fault: (a) grid phase voltage, V; (b) MSC active power reference and grid power, W; (c) rotor speed, rad/s; (d) electromagnetic torque, N-m; (e) dc-link voltage, V; (f) grid current, A.

Fig.4 Performance of controllers (I, II and proposed controller) during Type – F fault of 50% voltage sag with -12.5o phase-angle jump (a) dc-link voltage, V; (b) grid active power, W; (c) grid current, A. (d) grid current loci in stationary reference frame during fault period

Fig.5 Performance of controllers (I, II and proposed controller) under distorted utility (a) grid active power, W; (b) grid current, A (zoomed in view).

 CONCLUSION:

 A modified active power control and current oscillation cancellation scheme are proposed for the MSC and GSC, respectively to strengthen the FRT compliance of the PMSG based WG. A 1.5 MW system is considered to validate the performance of proposed controller. Reduced active power regulation proportionate to retained grid voltage during fault conditions guarantees the dc-link voltage and GSC peak current are within its operating limits. Unlike dual vector control scheme, the GSC is implemented in PSF with oscillation cancellation terms and positive sequence grid angular frequency to suppress the oscillation in system parameters and to obtain symmetrical sinusoidal grid current. The control scheme is validated for various types of fault and distorted grid conditions. The reduced percentage of oscillation in the system parameters as recorded in Table I confirms the efficacy of the proposed method when compared with the controllers (I) and (II). As a future work, the proposed control scheme can be deployed to address weak grid condition with an improvised design.

REFERENCES:

[1] H. Polinder, F. F. A. van der Pijl, G. -J. de Vilder, and P. J. Tavner, “Comparison of Direct-drive and Geared Generator Concepts for Wind Turbines,” IEEE Trans. Energy Convers., vol. 21, no. 3, pp. 725–733, Sep. 2006.

[2] P. Li, Y. -D. Song, D. -Y. Li, W. -C. Cai, and K. Zhang. “Control and Monitoring for Grid-Friendly Wind Turbines: Research Overview and Suggested Approach,” IEEE Trans. Power Electron., vol. 30, no. 4, pp. 1979-1986, Apr. 2015.

[3] M. Chinchilla, S. Arnaltes, and J. Burgos, “Control of Permanent-Magnet Generators Applied to Variable-Speed Wind-Energy Systems Connected to the Grid,” IEEE Trans. Energy Convers., vol. 21, no. 1, pp. 130–135, Mar.2006.

[4] J. F. Conroy and R. Watson, “Low-Voltage Ride-Through of a Full Converter Wind Turbine with Permanent Magnet Generator,” IET Renew. Power. Gener., vol. 1, no. 3, pp. 182–189, Sep. 2007.

[5] A. D. Hansen, and G. Michalke, “Multi-pole Permanent Magnet Synchronous Generator Wind Turbines Grid Support Capability in Uninterrupted Operation during Grid Faults,” IET Renew. Renew. Power Gener., vol. 3, no. 3, pp. 333–348, Nov. 2009.

 

Power Quality Improvement of PMSG Based DG Set Feeding Three-Phase Loads

IEEE Transactions on Industry Applications, 2015

ABSTRACT: This paper presents power quality improvement of PMSG (Permanent Magnet Synchronous Generator) based DG (Diesel Generator) set feeding three-phase loads using STATCOM (Static Compensator). A 3-leg VSC (Voltage Source Converter) with a capacitor on the DC link is used as STATCOM. The reference source currents for the system are estimated using an Adaline based control algorithm. A PWM (Pulse Width Modulation) current controller is using for generation of gating pulses of IGBTs (Insulated Gate Bipolar Transistors) of three leg VSC of the STATCOM. The STATCOM is able to provide voltage control, harmonics elimination, power factor improvement, load balancing and load compensation. The performance of the system is experimentally tested on various types of loads under steady state and dynamic conditions. A 3-phase induction motor with variable frequency drive is used as a prototype of diesel engine with the speed regulation. Therefore, the DG set is run at constant speed so that the frequency of supply remains constant irrespective of loading condition.

KEYWORDS:

  1. STATCOM
  2. VSC
  3. IGBTs
  4. PMSG
  5. PWM
  6. DG Set
  7. Power Quality

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1 Configuration of PMSG based DG set feeding three phase loads.

EXPECTED SIMULATION RESULTS:

 

Fig. 2. Dynamic performance at linear loads (a) vsab, isa,isb and isc ,(b) vsab, iLa,iLb and iLc (c) Vdc, isa,iLa and iCa

CONCLUSION:

The STATCOM has improved the power quality of the PMSG based DG set in terms voltage control, harmonics elimination and load balancing. Under linear loads, there has been negligible voltage variation (From 219.1 V to 220.9 V) and in case of nonlinear load, the voltage increases to 221 V. Thus, the STATCOM has been found capable to maintain the terminal voltage of DG set within ± 0.5% (220 ±1 V) under different linear and nonlinear loads.

Under nonlinear loads, the load current of DG set is a quasi square with a THD of 24.4 %. The STATCOM has been found capable to eliminate these harmonics and thus the THD of source currents has been limited to 3.9 % and the THD of terminal voltage has been observed of the order of 1.8%. Therefore, the THDs of source voltage and currents have been maintained well within limits of IEEE-519 standard under nonlinear load.

It has also been found that the STATCOM maintains balanced source currents when the load is highly unbalanced due to removal of load from phase ‘c’. The load balancing has  also been achieved by proposed system with reduced stress on the winding of the generator.

The proposed system is a constant speed DG set so there is no provision of frequency control in the control algorithm.

However, the speed control mechanism of prototype of the diesel engine is able to maintain the frequency of the supply almost at 50 Hz with small variation of ±0.2 %.

Therefore, the proposed PMSG based DG set along with STATCOM can be used for feeding linear and nonlinear balanced and unbalanced loads. The proposed PMSG based DG set has also inherent advantages of low maintenance, high efficiency and rugged construction over a conventional wound field synchronous generator based DG set.

 REFERENCES:

[1] Xibo Yuan; Fei Wang; Boroyevich, D.; Yongdong Li; Burgos, R., “DC-link Voltage Control of a Full Power Converter for Wind Generator Operating in Weak-Grid Systems,” IEEE Transactions on Power Electronics, vol.24, no.9, pp.2178-2192, Sept. 2009.

[2] Li Shuhui, T.A. Haskew, R. P. Swatloski and W. Gathings, “Optimal and Direct-Current Vector Control of Direct-Driven PMSG Wind Turbines,” IEEE Trans. Power Electronics, vol.27, no.5, pp.2325-2337, May 2012.

[3] M. Singh and A. Chandra, “Application of Adaptive Network-Based Fuzzy Inference System for Sensorless Control of PMSG-Based Wind Turbine With Nonlinear-Load-Compensation Capabilities,” IEEE Trans. Power Electronics, vol.26, no.1, pp.165-175, Jan. 2011.

[4] A. Rajaei, M. Mohamadian and A. Yazdian Varjani, “Vienna-Rectifier-Based Direct Torque Control of PMSG for Wind Energy Application,” IEEE Trans. Industrial Elect., vol.60, no.7, pp.2919-2929, July 2013.

[5] Mihai Comanescu, A. Keyhani and Dai Min, “Design and analysis of 42-V permanent-magnet generator for automotive applications,” IEEE Trans. Energy Conversion, vol.18, no.1, pp.107-112, Mar 2003.