電力系統(tǒng)外文翻譯--大型電力系統(tǒng)中由于雙饋感應(yīng)發(fā)電機的滲透增加引起的阻尼功率振蕩的輔助控制（英文）

1、 1Abstract--This work investigates the impact of increased pene-tration of doubly fed induction generators (DFIGs) on electrome- chanical modes of oscillations of a large interconnected power system. The work proposes

2、a control mechanism aimed at design- ing the power system stabilizer (PSS) for a DFIG similar to the PSS of synchronous machines. The wind generator power output is taken as input to the PSS. The active power command i

3、s mod- ulated in phase opposition to the power system oscillation and is fed to the active power control loop of the DFIG. An additional control block with the DFIG terminal voltage as the PSS input signal is fed to t

4、he reactive power control loop. The mechanism serves the purpose of improving the damping of critical mode which is validated by eigenvalue analysis. The work also com- pares two different control mechanisms that can b

5、e employed for damping low frequency inter area modes of oscillations. With the latter based on the idea of modifying the torque set point of the DFIG for changes in grid frequency. The proposed technique is tested o

6、n a large test system representing the Midwestern portion of the U.S. interconnection. Index Terms—Doubly fed induction generator, wind turbine generators, transient stability, small signal stability, sensitivity, iner

7、tia. I. INTRODUCTION ROWING environmental concerns and attempts to re- duce dependency on fossil fuel resources are bringing renewable energy resources to the mainstream of the electric power sector. Among the various

8、renewable resources, wind power is assumed to have the most favorable technical and economical prospects [1]. When deployed in small scale, as was done traditionally, the impact of wind turbine generators (WTGs) on p

9、ower system stability is minimal. In contrast, when the penetration level increases, the dynamic perfor- mance of the power system could be affected. This work was supported by the National Science Foundation under the

10、 Grants NSF ECCS-0652513 and EEC-9908690 at the Power System Engi- neering Research Center. Durga Gautam is with the Department of Electrical Engineering, Arizona State University, AZ, USA (e-mail: durga.gautam@asu.edu)

11、. Vijay Vittal is with the Department of Electrical Engineering, Arizona State University, AZ, USA (e-mail: vijay.vittal@asu.edu) Raja Ayyanar is with the Department of Electrical Engineering, Arizona State University, T

12、empe, AZ 85287, USA (e-mail: rayyanar@asu.edu). Terry Harbour is a senior utility engineer. Among the several wind generation technologies, variable speed wind turbines utilizing doubly fed induction generators (DFIGs)

13、are gaining prominence in the power industry. As the performance is largely determined by the converter and the associated controls, a DFIG is an asynchronous generator. Since DFIGs are asynchronous machines, they pr

14、imarily have four mechanisms by which they can affect the damping of electromechanical modes (since they themselves do not partic- ipate in the modes): 1. Displacing synchronous machines thereby affecting the modes 2.

15、 Impacting major path flows thereby affecting the synchro-nizing forces 3. Displacing synchronous machines that have power system stabilizers 4. DFIG controls interacting with the damping torque on near-by large synchron

16、ous generators The power electronic converter at the heart of the DFIG controls the performance and acts as an interface between the machine and the grid. With conventional control, rotor cur- rents are always control

17、led to extract maximum energy from the wind. Hence, with the increased penetration of DFIG based wind farms, the effective inertia of the system will be reduced and system reliability following large disturbances cou

18、ld be significantly affected. In order to improve the system damping with the high pe-netration of DFIG based wind farms, the concept of auxiliary PSS loop for DFIG has been introduced in the literature re- cently. The

19、auxiliary PSS loop proposed in [2] is believed to change the stator currents of DFIGs so as to increase the damping torques of the synchronous generators in the system. The control philosophy adopted is similar to the

20、 PSS of the synchronous generators and consists of a washout block, PSS gain and phase compensation while the input signal is derived from the DFIG stator electrical power. An auxiliary signal derived from the freque

21、ncy deviation is used as the input to the PSS in [3]. For the test system considered in the paper, inter area oscillation damping is found to improve with the proposed PSS. The supplementary control signal derived fro

22、m the terminal voltage is used as the input to the PSS in [4]. The stabilizing signal is fed to the rotor quadrature voltage in the active power control loop so as to provide additional damping. Supplementary Control

23、for Damping Power Oscillations due to Increased Penetration of Doubly Fed Induction Generators in Large Power Systems Durga Gautam, Student Member, IEEE, Vijay Vittal, Fellow, IEEE, Raja Ayyanar, Senior Member, IEEE,

24、Terry Harbour, Member, IEEE G978-1-61284-788-7/11/$26.00 ©2011 IEEE3Fig. 1. Schematic diagram showing active power and pitch angle controllers of DFIG. the rated value. When the power output increases beyond the ra

25、ted value, pitch compensator acts to increase the pitch angle and brings the power back to the rated value. The torque command (Tset) is used to compute power order (Pord) which in turn provides excitation current to

26、the rotor side converter. The maximum active power order (Pmax) from the controller is limited by the active power limiter block shown in Fig. 1. The active current command (Ip) is computed by dividing Pord from the

27、wind turbine model by the generator terminal voltage (Vterm). The active current command is limited by the short term active current capability of the converter (Ipmax). III. IMPACT ON SMALL SIGNAL STABILITY In an in

28、terconnected system, the ability to restore equili-brium between electromagnetic torque and mechanical torque is determined by the rotor angle stability of each synchronous machine. Accordingly, the increased number of

29、 asynchronous generators in the system influences the network dynamic cha- racteristics. The variable speed WTG design consisting of the power electronics converter imparts significant effect on the system dynamic per

30、formance. Following a disturbance, the change in electromagnetic torque of the synchronous machine can be characterized by two torque components, namely, the synchronizing torque component and the damping torque compon

31、ent. The present work focuses on the latter component which impacts small signal stability of the system. The small signal stability problem normally occurs due to insufficient damping torque which results in rotor osc

32、illations of increasing amplitude [8]. The eigenvalues of the system matrix A characterize the stability of the system [8]. The in- troduction of several DFIG wind farm does have the potential to change the electromec

33、hanical damping performance of the system. This can be attributed to the reduced inertia of the system thus impacting the inertial mode of oscillation of the system. IV. PROPOSED CONTROL STRATEGY This section proposes

34、 a supplementary control for a DFIG similar to the PSS of conventional synchronous machine. In order to ensure the effectiveness of the proposed mechanism, comparison is done with the control mechanism proposed in [9]

35、. A. Eigenvalue Sensitivity The basis of the present study lies in the premise that with the increased penetration of DFIG based wind farms the effec- tive inertia of the system will be reduced. In this regard, a first

36、 step proposed towards studying the system behavior with in- creased DFIG penetration is to identify how the small signal stability behavior changes with the change in inertia. The ap- proach is thus intended to evalua

37、te eigenvalue sensitivity with respect to generator inertia. The following steps are adopted while evaluating the system response with respect to small disturbances: ? Replace all the DFIGs with conventional synchro

38、nous generators of the same MVA rating which will represent the base case operating scenario for the assessment. ? Perform eigenvalue analysis in the frequency range: 0.1 to 2 Hz and damping ratio below 2.5%. ? Eval

39、uate the sensitivity of the eigenvalues with respect to inertia of each wind farm represented as a conventional synchronous machine which is aimed at observing the ef- fect of generator inertia on dynamic performance.

40、? Perform eigenvalue analysis for the case after introducing the existing as well as planned DFIG wind farms in the system. B. DFIG PSS and Oscillation Damping The PSS employed for DFIGs in this paper consists of In

41、ertia controllerto generator/converter model ?Tset Pmax Pmin Tset ?θ Prated = 1 Pe θ ωeωt Pm vw ωeWind power model Rotor two mass shaft model Reference speed setting Torque controller Pord Active power limiter Pitch