T ^ P CHi KHOA HQC & C N G NGHE CAC T R U ' N G DAI HQC KY T H U J L T * S 86-2012 NOVEL DESIGN FOR SPEED AND ACTIVE POWER CONTROL OF A SMALL HYDRAULIC TURBINE ( PHUONG PHAP MCil THIET KE H$ T H N G DIEU KHIEN TOC DQ VA CONG SUAT CHO NHA M A Y THUY DIEN NHO Nguyen Hong Quang Hanoi University of Science and Technology Received Mach 31", 2011 \ ABSTRACT In recent years, the development of small hydro power stations has been widely applied accr Vietnam This paper shows the complete design process for a hydro turbine controller The algorith is given based on the typical mathematical models of the target system The controller parameters obtained from the novel analytical formulars which take into account the wide range of operating points of hydraulic turbine In addition, the paper also presents the details design of microcontrolle based implementation, the use of hardware in loop (MIL) to verify the model in the laboratory condit The expenence result from hydro controller of Rhyninh hydro turbine unit in Central Vietnam is g as an illustration TOM TAT Trong nhung nSm gin d§y, vl^c phat trien nha may thuy dien nho dang day manh tren toan nuoc Vi0t Nam Trong xu hifong lam chu cdng ngh$ dieu khien thuy di$n nay, tdc gia trinh bay h$ thong diiu khien tdc co ban Thu$t toan dieu khien xay dung tren md hinh toan hoc cua /i# thon va tinh den dai ho$t dgng cua turbine thuy luc B^i b^o cung trinh bdy ve phan cung he thong sif dun vi diiu khien va mo hinh biin vat ly thi nghiem kiem dinh thuat todn Cuoi cOng, ket qua chay he diiu tdc tai nha mdy thuy di0n Rhyninh, miin Trung Viet Nam tfupc (?tra nhw minh hga cho tin dung din cua phuxyng phap thiet ki ] INTRODUCTION The motivation of the work presented here is in the development of digital turbine governor for the old Rhyninh hydro station The main problem was to deal with the difficulties of finding the controller's gain given the poor information of the hydro turbine, manufactured by Czechoslovakia neariy 30 years ago The findings of mathematical model of hydro turbine unit was somehow presented in [1] However, the method of parameter identification, which relies on neural network algorithms, is very time consuming Futhermore, the stability is not ensured for different loads Reference [3] considers the nonlinear and lime-varying property oi hydraulic turbine regulating system, and i robust pole assignment controller was proposed The study was accounted for the uncertainty of wate time constant Tw, which is serious for the stability of governor system The applicablities of this design in the real-world turbine controller is still agumented, given the background of field engineers The model-based controller design procedure for determining governor parameters described in this paper is natural and straitforward The problem was solved in orderly maner First, the appropriate mathematical model of the main system is created in form of different equations The controllers are chosen using the well-known proportional-integral- derivative / proportional integral (PID/PI) controllers Then, the designer has to choose closed-loop poles from the required characteristics o' the controlled system (overshoot, rise time, s^ulmg time, etc.) The target was to obtain equations for the controller parameters that are flinctions of the system's operating point and the required closed-loop dynamics, thus, there is no need for heuristic tuning The procedure can be uied foi a new turbine governor design and ;or refiirbishing old turbine governors TAP CHi KHOA HQC & C N G NGHE CAC TRUCfNGD^I HQC KY THUAT * S 86-2012 H : working water height [m] Ho: initial water height [m] Q : water flow [mVs] A : area of penstock [m'] L: length of penstock [m] flg: gravitational constant [mVs] t : time [s]^ The verification of the controllers can be seen in the real-time digital simulator, which implemented in Matlab Real-Time Workshop The desgin allows to represent a wide and significant class of operating conditions (turbine startup, normal and emergency shutdown, no-load generation parallel operation with shortcircuits) and the intergration of excitafion system with additional control loops (PSS, under and over-excitation) allow deep performances checking and fine parameters tuning Implementation examples are given in Rhyninh hydro power to show the effectiveness of the proposed control algorithm The models described so far are nonlinear; thus, they are not suitable for the controller synthesis using linear method The linear model would be obtained from the vicinity of the operating point Where A is the distance from the operating point, and b|, are the coefficients as functions of the operating point for variables: IL HYDROELECTRIC POWER TURBINE W 2.1 Hydroelectric power turbine = b AH + b Ao) + b AG 11 Configuration of hydroelectric power plant system is shown in Fig I SP (Automatic Power and Frequency Control) generates the power and IVequency setpoints based on load demand Governor controller regulates turbinegenerator rotational fi-equency and controls power generation output Governor actuator is a mechanical system which actuates guide vane, adjusting flow rate of hydraulic turbine discharge- In general, there exist nonlinearities in the governor actuator dynamics, the hydraulic turbine characteristics and head losses of tunnels AY P = KpHU (2) = b^AH ^b^^Aw + b^^AG (6) = 0,5G; 6,3 = / / " - ' - , ( & ) - I ) ; Given the Ato is relatively small in grid connecting state, the linear turbine model would be as follows: ^''m The hydro turbine is described by the water flow ftinction and power fiinction In this paper, the model according to [4] is used C) (5) 13 The b|| coefficients are partial derivatives of the water flow function G b =-^-b^=0; b,,=lH; 24H 2.2 Hydraulic turbine model U = K„G4H 12 , AG l + (''ir*13''22l'*223 23 '^'m AC )T s (7) l + *n^w^ 23 ytl w (8) 1+»,,V "'*• V ° * l 3*2 r ' ' ! 1*23 dU -f{H-H,) dt L Q = AU and AU = b„AH + b„AG KF„=b,AH + b,,AG U : water flow speed [m/s] G : ideal gate opening [%] "I TT> ^ I Fig I A typical control structure of a smal hydroelectric power turbine 13 (9) (10) T ^ P CHl KHOA HQC & C N G NGHf CAC T R U ' N G D ^ I HQC KV THU^T * S 86 - i : Figure describes the relation between turbine mechanical power, water How speed, water height with gate step openning D|, : inertia moment of the unit including a rotating parts I T,n : mechanical time constant of the unit (s) III SYNTHESIS OF A GOVERNOR CONTROLLER • The speed governing and the powe governing are analyzed separately in order ti illustrate the procedure for calculating thi controller parameters in different modes o operation The practical considerations cm should take into account are the different modei of operation of the turbine governing systen and combined speed and power governing, , I Figure Gate step openning 2.3 Power-Unit Rotor Dynamics Model 3.1 Speed Governing Dynamics of a power unit in the turbine governing systems, in most of the cases, can be described by using only inertia moment of the power unit Using Newton's second law where torques are expressed as powers divided by the rotation speed, one can derive the following The control structure of speed governing is show on Figure iS)- Afi),, AP-AP, Ts + D, (11) Fig Speed governing system PL: mechanical power on the turbine shaft (per unit); In [5], the linearized model of th( hydraulic turbine is P: base power (w); b^^-b^J^^s 0)^ : angular velocity of the unit (in rad/s); Gra{s) = - \+b,,rs With the closed loop function: GAs) :y+(7;+6„7;,)5-+rxAi^' ^23^, + ^ton^' + AoP2^' + AonS^-*-bnTJJ,y (12) With (13) = h^Kj + D„/„ -I- r„ - b^jx^ + b,,D;r^^ - b,j„ K,, (14) = TJ„, - 6.,r., K, - b,„TX + 6,, ?:, (Z)/„ + r„,) (15) = D-b„ (16) (17) A^rco ^A"TCO T^P CHI KHOA HQC & CONG NGHE CAC TRUONG D„ + //^„7;, TJ.,G„(p,p, + p,p, + p,p, + /),p, + p,p, + P J P J Pu.-,=D,.H'.^,(-2H^J, +2q,JJ-ZD„Hi„TA Pu., =-'iD„q^^H'jiJ„ G„ + Hi.l,T;G-TJ,„(p,p,p, + p,p,p, + A A A + A P I A ) PuM= HTcJ'«GJX,(p,p,p,q^,+ p,p,p.,q^^+ p,p,p,q„^+ p,p,p,q„^+ p,p,p,T„.Gi) (20) 3.2 Synthesis of power governing In which : The block diagram of the power controlled system is shown in Fig Bs : numerator of the controlled system transfer function As : denominator of the controlled system transfer function Ys : numerator of the controller transfer fiinction R Xs : denominator of the controller transfer function R Fig Power governing system The transfer ftinction describing the change of the unit power in respect to the reference power is given in P AX^+BX (21) Kpp: feedforward gain The controller will be designed using the pole placement method, with the PI controller K in form: R = K„ We would come to the transfer funtion P^f " b,,TJ,y K (22) -)-(6,,7; + T„- TJ^,,,Kp)s- + ib,,^K^, +1 -TJ,.,,K,)s + b, K, It can be seen that by designing =—K- it is possible to compensate for one of the zeros With the assumptions of turbine operating point hrc =H[co, nominal Go, The controller speed £y V = 1, parameters as ftinctions can be calculated as follows i^ _ ^ "•/> ~ AjUi (_Aipi2 ^ T^ PIJ'P, '^P'PI" '^P'TPI ' TAP Clll KHOA HQC & C6NG NGHf, CAC TRUttNG D.rt(i|J Fig i: The IIMI nilertaec (>t liirhinc i:,'nvn!or I he author has verified control perRimianee of the luwel governor eiiuipmenl b\ the sinuikition tool, and also conllnned the effecli\eiiess of the planl simulaiioii model thought experiments Fig Field tests of the turbine controller In this brief, it has been shown that PID control can achieve a substantial improvement in tracking a power target An advantage of the T^P CHi KHOA HQC & C N G NCHf CAC TRU'bNG D^l HQC KY THUAT * S6 86 PID controller is that it is relatively easy to implement and commission This makes testing easy and relatively safe, wh.ch ,s miportant when there are severe mancia consequences if , , , , , , ^ the planl should hiil durmg operation Acknowlegement ^^ ^^^^^^ gratefully ac edge the ^^.^ ^^ ^ |.^^^ ^ j C / ^ , , , ID-DTDU xi • i r* • u- u „«^kUfi •• i i rarrv nut National Project which enabled u; ' ' carry out REFERENCES i Jiang Chang Zhihuai Xiao, Shu qingwnag "Neural network predict control for the hydro turbine generator set," The second international conference on machine learning and cybernetics (1CMLC2003) 2003, pp.2-5 GUI Xiao-yang, MEI Sheng-wei, LIU Feng and LU Qiang, "Adaptive Nonlinear Control for Hydraulic Turbine Governor," IEEE Trans Proceeding of the CSEE Vol.26, No.8, pp.66-7I, Apr 2006 Har\'ey, A., Brown, A., Helliarachi, P and Inversin, A., Micro Hydel Design Manual, A Guide to Small Scale Water Power Schemes, Iniermediate Technology Publications, 1993 Kundur, P Power system stability and Control Tala-McGraw Hill Co 1221, Avenue of the Americas, New York, NY 1994 Working Group on Prime Movers, Hydraulic turbine and turbine control models for system dynamic studies, IEEE Transaction on Power System, 7, 1992, pp 167-179 W Grega, "Hardware-in-the-loop simulation and its application in control education", 29th ASEE/IEEE Frontiers in Education Conference Session 12b6, pp 12 November, 1999 Author's address: Nguyen Hong Quang -Tel: 0912.068.608, Email; quangnh(5^mail.hut.edu.vn Bp mon T^r dong hoa xi nghiep cong nghiep - Vi?n Dien Trudng Dai hpc Bach khoa Ha Npi So I - Dai C6 Viet - Hai Ba Trimg - Ha Npi ... (Hz), Tw= 0.87 (s), y,," 0.97 (u) qNi= 0.09 (mVs), T,„= (s), K,= 5, T,= 0.02 The desired poles are chosen as: p, = -0,1 ; p: = -0,l; pj=-0,14 The results of the model simulation usin| nonlinear model... simulation Similar simulation was also conducted for power govering With the desired poles are chosen as pi=-1,2 vi p:= - 1,2 and the controller parameters K.p=0,08; Ki= 0,1; Kpp= -0,08 The simulated