[001] The present invention relates to the field of hydro turbine control systems.
The present invention, in particular, relates to the intelligent hydro turbine control
system for variable speed hydro generating units.
DESCRIPTION OF 5 THE RELATED ART:
[002] At present, the generators used in domestic and foreign hydropower stations
are conventional hydrogenerators, mainly synchronous generators, and there are
also a small number of ordinary asynchronous generators.
[003] The generator can only run at the rated speed, and the speed of the unit is
10 fixed. Therefore, the operating condition of the turbine is only determined by the
water head and load, and there is no room for adjustment.Conventional
hydrogenerating units are designed to achieve the optimal unit speed when the
weighted average water head is used.
[004] The turbine has good performance and high efficiency only when it runs near
15 the optimal unit speed. When the water head changes, the unit speed of the turbine
will also change. The current method is to adjust the speed of the turbine by
adjusting the opening angle of the guide vane. However, because the current
method of detecting the speed of the turbine is the speed measurement of the gear
plate, the response speed is slow; it takes a certain amount of time to adjust the
20 opening angle of the guide vane. During the process of adjusting the opening angle
of the guide vane, the unit speed will deviate from the optimal unit speed, while the
power and frequency output by the generator varies with the turbine and speed.
Thus the voltage and frequency stability of the generator output is very poor.
[005] Reference may be made to the following:
25 [006] Publication No. DE3855290 relates to a variable speed hydropower plant and
includes a pump turbine with S-shaped characteristics at the turbine operation. A
current time turbine operating point is grasped on a turbine characteristics diagram
- 3 -
of the pump turbine. A limit operation characteristics curve of the pump turbine is
formed in advance so as not to reach the S-shaped characteristics turbine operation
region. A reach of the limit operation characteristics curve is detected, a rotating
speed (N) of the pump turbine is lowered. An inrush of the pump turbine into the
S-shaped characteristics turbine operation region is eliminated, so 5 the continuation
of a stable and reliable turbine operation can be guaranteed.
[007] Publication No. CN202261153 provides a control device of a variable speed
constant frequency generator for the hydroelectric power generation, which
comprises a hydraulic turbine, guide vanes, a generator, a microcomputer governor,
10 a photoelectric encoder, a controller, a signal conditioning circuit, a rotor side
converter, a network side converter, a transformer, and a driving circuit, wherein
the photoelectric encoder is an absolute type photoelectric encoder; the controller
is provided with a group of output ports; the microcomputer governor is connected
with the hydraulic turbine and the guide vanes; the hydraulic turbine is
15 mechanically connected with a rotor of the generator through a coupling, and a
stator winding of the generator is switched into a power grid transformer which is
directly connected with a power grid. According to the utility model, a voltage and
a frequency which are generated by the generator can be ensured to be kept
constant.
20 [008] Publication No. CN110262223 provides a fractional order PID speed
regulating system-based modeling method for a hydraulic turbine comprehensive
model. This method includes the following steps: Step 1, establishing a hydraulic
turbine governor simulation analysis mathematical model of a fractional-order PID
speed regulating system and utilizing a mixed algorithm to optimize the objective
25 function of the fractional-order PID speed regulating system; step 2, establishing
the mathematical models of a mechanical hydraulic system and a water diversion
system of a hydraulic turbine speed regulating system; and step 3, establishing a
hydraulic turbine generator model. Through the utilization of MATLAB simulation
modeling, improvement can be performed on classic PID speed regulating systems
30 on the basis of previous research; comprehensive models which can reflect each
- 4 -
parameter of the hydraulic turbine speed regulating system and the generator system
can be established according to the analysis of embodiments; and for the running
conditions of actual hydraulic turbine units in actual application, good reaction can
be achieved on the parameters of hydraulic turbines during the fluctuation of loads
so that that guarantee can be provided for accident prediction 5 and system safety
operation.
[009] Publication No. CN102352812 discloses a sliding modebased hydro turbine
governing system dead zone nonlinear compensation method in the technical field
of hydro turbine control.The method comprises the following steps: constructing a
10 state space model for a hydro turbine governing system, and introducing an
additional state variable; designing a sliding mode governor, and making an ideal
hydro turbine governing system approximately stable by regulating the controlling
quantity of the sliding mode governor, and designing a dead zone nonlinear
compensator to compensate dead zone nonlinearity of an actual hydro turbine
15 governing system. By this method, the automation level of the hydro turbine
governing system is improved, the safety of the system is improved, the mechanical
wear of the set is reduced, the equipment maintenance cost is reduced, and the
economic performance of a hydroelectric generating set is improved.
[010] Publication No. DE3332544 relates to a control device is described for a small
20 hydroelectric power system, especially a flow turbine, for operation in the case of
a power station having a synchronous generator which can be changed over between
independent operation and network operation. In independent operation, the control
device operates using speed regulation. When a changeover is made to network
operation, the use of speed as the control variable is dispensed with and the control
25 device operates using water-level or volume-flow control. This is made possible in
that the speed of the synchronous generator and of the water turbine is kept constant
by the network if the network power is virtually infinitely large in comparison with
the turbine power.
[011] Publication No. US4823018 relates to a control system for a variable speed
30 water turbine generator apparatus,including a first function generator that is
- 5 -
responsive to an output command signal. The first function generator produces a
rotation number command signal. A speed adjuster produces an output signal in
accordance with a different signal between the first function generator output and
an actual rotation number. An adder adds the generator output command signal to
the speed adjuster output signal to determine an overall output 5 command signal. An
output adjuster produces an output signal in accordance with a difference between
the adder output and an actual power output of the generator for controlling the
firing angles of the frequency converter. A second function generator, responsive
to the generator output command signal, determines an opening command signal
10 for the variable opening vanes. An opening adjuster produces an output signal in
accordance with a difference signal between the second function generator output
and an actual opening of the variable opening vanes to control the variable opening
vanes. The first and second function generators increase command values for the
rotation number and the variable opening vanes, respectively, as the output
15 command signal increases. The frequency converter is further controlled to
maintain the rotation number within a predetermined operating range.
[012] Publication No. 201911024489 relates to micro hydro plant, particularly to
the controller design for the micro hydro plant. More particularly, the present
invention is related to a system for intelligent and adaptive control for micro hydro
20 plants. It presents development of a new control system comprising nLMS and FTF
as linear components and ANN and Fuzzy PI as nonlinear components, and it
discloses a system with designof an offline ANN based PI controller to work under
varying input parameters such as water starting time, regulation parameter and the
nominal loading for a hydroelectric plant.
25 [013] Publication No. IN201402979P2 relates to a method and apparatus for
reducing electromagnetic drag in an electric machine,including a laminated stator
having wire slots, disposed around the inner periphery spaced into sectors separated
by a pole iron support structure. The slots contain induction windings. A series of
wound lateral pole irons may be arranged around the inner periphery of the stator,
30 the first ends of which extend into the slots in the sectors. A support structure
- 6 -
supports the lateral pole irons by forming a circular opening concentric with the
inner periphery of the stator. A rotor may be inserted into the circular opening of
the lateral pole iron support structure and supported at the stator lateral pole iron
ends by support means. A plurality of rotor inserts may contain free-wheeling
permanent magnet inserts spaced along an outer periphery of the 5 rotor. The rotor
may be inserted into the circular opening of the lateral pole iron support structure,
and the free-wheeling permanent magnet inserts may be inserted into cavities along
the outer periphery of the rotor.
[014] The article entitled, “Variable speed drive as an alternative solution for a
10 micro-hydropower plant” by Malik Usman Akhtar; diva-portal.org; 2012 talks
about the variable speed drive as an alternative solution a microhydropower plant.
The detailed mathematical model for a micro-system, including a Kaplan turbine,
mechanical shaft, and electrical machines, is presented and validated through
simulations. A control strategy for an autonomous operation of a doubly-fed
15 induction machine-based drive is developed for a wide range of speed. The drive
can operate at a unity power factor. The possible applications of the analyzed
system are also presented. As a positive side of the system, it is found that the direct
interaction between the power electronic converters and the utility grid can be
avoided by exploiting the proposed topology, which might lead to a better quality
20 of the produced power in terms of harmonics. This could also lead to the removal
or reduction of the size of the harmonic filters that are being used in conventional
doubly fed induction generator installations. As regards the drawbacks of the
system, a comparison of converter and generator ratings between the analyzed
solution and the conventional solution was performed. While the rating of the
25 converterremains the same, there is one more electrical machine, and the doublyfed
generator rating is slightly increased. Losses are also slightly larger due to the
presence of the second machine.
[015] In order to overcome the above listed prior art, the present invention aims to
provide an intelligent hydro turbine control system for variable speed hydro
30 generating units.
- 7 -
OBJECTS OF THE INVENTION:
[016] The principal object of the present invention is to provide an intelligent
controller based hydro turbine control system for variable speed hydro generating
units.
[017] Another object of the present invention is to provide an intelligent 5 controller
for guide vane opening in hydro turbine control system of a hydro generating unit
equipped with an asynchronous generator.
[018] Another object of the present invention is to provide an intelligent controller
which improves the system response during startup, synchronous to
10 subsynchronous, and synchronous to the super synchronous operation of variable
speed hydropower plant.
[019] Yet another object of the present invention is to provide a system and
controller which shall help hydropower project developers to perform quick
changeovers of generating equipment from one mode to another, i.e., generation to
15 pumping and vice-versa, and increase revenue generation.
SUMMARY OF THE INVENTION:
[020] The present invention relates to an intelligent hydro turbine control system
for variable speed hydro generating units. The controller makes the system’s
response fast. In addition, it reduces the overshoot of all performance-related
20 parameters of DFIM. The present invention relates to providing an intelligent
controller for guide vane opening in hydro turbine control system of a hydro
generating unit equipped with an asynchronous generator. The dynamic
performance is improved, i.e., overshoot and settling time (settling time for startup
process, synchronous to subsynchronous, and super synchronous is reduced by 85,
25 47, and 25 s, respectively, in comparison with PID controller, and the overshoot is
also reduced) and (settling time for startup process, synchronous to
subsynchronous, and super synchronous is reduced by 10, 7, and 10 s, respectively,
in comparison with CSMC, and the overshoot is further reduced). It shall help the
- 8 -
hydropower (HP) project developers to perform the quick changeovers of
generating equipment from one mode to another, i.e., generation to pumping and
vice versa, and increase the revenue generation.
BRIEF DESCRIPTION OF THE DRAWINGS:
[021] It is to be noted, however, that the appended drawings 5 illustrate only
typical embodiments of this invention and are therefore not to be considered
for limiting its scope, for the invention may admit to other equally effective
embodiments.
[022] Fig.1 shows a schematic of variable speed hydro generating unit;
10 [023] Fig.2 shows a block diagram of the present invention;
[024] Fig.3 showsthe startup process with PID controlled hydro- turbine;
[025] Fig.4 shows the startup process with CSMC controlled hydro- turbine;
[026] Fig.5 shows the startup process with iPI CSMC controlled hydro- turbine;
[027] Fig.6 shows synchronous to subsynchronous operation of PID controlled
15 hydro-turbine;
[028] Fig.7 shows synchronous to subsynchronous operation of CSMC controlled
hydro-turbine;
[029] Fig.8 shows synchronous to subsynchronous operation of iPI-CSMC
controlled hydro- turbine;
20 [030] Fig.9 shows synchronous to super synchronous operation of PID controlled
hydro- turbine;
[031] Fig.10 shows synchronous to super synchronous operation of CSMC
controlled hydro- turbine;
- 9 -
[032] Fig.11 shows synchronous to super synchronous operation of iPI-CSMC
controlled hydro- turbine;
[033] Fig.12 shows the experimental setup;
[034] Fig.13 shows startup process for PID, CSMC, iPI-CSMC controlled hydro-
5 turbine;
[035] Fig.14 shows synchronous to subsynchronous operation for PID, CSMC, and
iPI-CSMC controlled hydro-turbine;
[036] Fig.15 shows synchronous to super synchronous operation for PID, CSMC,
and iPI-CSMC controlled hydro-turbine.
10 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[037] The present invention provides a controller for guide vane opening (GVO)
for the hydro turbine control system (HTCS) of variable speed hydro generating
units.
[038] The present invention provides an intelligent controller for GVO in HTCS of
15 a hydro generating unit equipped with doubly fed induction machine (DFIM). The
controller makes the system’s response fast. In addition, it reduces the overshoot of
all performance-related parameters of DFIM. The schematic block diagram of the
system and controller is depicted in Fig. 1.
[039] The invention comprises a reservoir, penstock, turbine, generator, guide vane,
20 unit circuit breaker (UCB 1), generator circuit breaker (GCB 2), unit transformer
(3), excitation transformer (4), doubly fed induction machine (5), grid side
converter (6), rotor side converter (7), guide vane (8), hydraulic governor control
system (9), and the grid.
[040] The control of the output/speed of the unit is by adjusting the position of GVO
25 (in the case of Francis and Kaplan turbines) and needles of injecting nozzles (in the
case of Pelton wheel). These can be kept in any position between a fully closed and
- 10 -
nearly fully open position and regulate the flow of water to the runner to match the
required output at the existinghead. A closed-loop feedback controller generally
called a governor, is used to accomplish this.The modern governors use a PID
controller to have a stable and fast response to the system’s transient conditions.
The inlet valve and intake gates, on the contrary, are devices that 5 can either be in a
fully closed or fully open position to cutoff the water supply to the turbine and
penstock, respectively. Since they have only two locations of operation, only the
open/close commands are required. The PID-type controller has no application in
its control.
10 [041] Turbine water flow and output power are defined as follows based on the
modeling:
????? =
(??????????)
????
(1)
???? = ?????????????? (???? - ??????)(2)
[042] where???? – water flow, ???? - static head, ???? - net head, ????- water starting time,
15 ???? – turbine output power, ????- turbine efficiency, ??????- water flow at the no-load
condition and ?????? - is a constant used to convert the base value of a turbine to the
base value of a DFIM model.
[043] The DFIM converter control consists of rotor side and grid side control
strategies separately. Electromagnetic torque and reactive components of DFIM are
20 controlled through rotor side controller. The dc-link voltage and reactive power
component of grid are controlled through grid side controller. Equations (3), (4),
(5), and (6) are the control equations for active power (Pg), reactive power (Qg),
electromagnetic torque (Te), and machine reactive power (Qm), respectively.
???? =
??
??
?????????????? (3)
???? = -
??
??
25 ??????????????(4)
???? =
??
??
???? (?????? ?????? - ?????? ?????? )(5)
???? =
??
??
????[
????
????
-
????
????
] ?????? (6)
- 11 -
[044] where vg– grid voltage, igd- d-axis grid current, igq – q-axis grid current, isqstator
q-axis current, isd-stator d-axis current, ird-rotor d-axis current, irq-rotor q-axis
current, Lm – magnetizing inductance, vs- stator voltage, fs–stator flux, and Ls- stator
inductance.
[045] iPI-5 CSMC controller
[046] CSMC is employed to control the position of the guide vane in HTCS. The
CSMC scheme significantly improves the dynamic response, viz., overshoot and
settling time. It combines two sliding surfaces, i.e., the sliding-mode surface and a
complimentary sliding-mode surface. These two surfaces are derived by using
10 electrical torque, mechanical dynamic equations, and speed error of DFIM, as given
in the following sections. It is used because of its simplicity and high robustness for
the system uncertainties.
[047] Input/output are combined as mono variables. A finite-dimensional SISO
(single input, single output) system is described by equation (7)
15 ??(??, ??, ??? ……………………. ??(??), µ, µ? ………………………µ(??) = 0(7)
[048] where E is the linear or nonlinear smooth function of its augments, t is a
continuous variable, y is a controlled output signal, and u is the control signal.
Assuming an integer n, 00, non-physical constant
?? = ??(??) - ??µ, which is obtained from µ and estimation of nth order derivative of
y.
25 [049] To get the desired behavior, for n=1, the control law for iPI is
µ = -
??
??
(?? ??
- ????? + ???? + ???? ? ?? ????) (10)
- 12 -
[050] where, ???? and ???? are the usual tuning constants of PI controller.
[051] ?? ??
isan estimate of F(t), ????? = reference output trajectory, e= error defined as
?? = ?? - ???? (11)
[052] A low pass filter (LPF) is used to find the estimate of ??? and is presented by
5 ????? . Also, a filtered derivative of reference ???? is generated and presentedby ?????.
?? ??
= ????? - ??µ(12)
eest = (??? - ??? ??) = (?? -?? ??
)(13)
From (10), (11), and (12)
??µ = (-????? + ??µ + ????? - ?????? - ???? ???? ???? + ??? - ??? )
10 ??µ = ????? - ????? ,-??? - ??????? + ??µ - ???? - ???? ???? ????
????????? = ??? + ?????? + ???? ? ?? ????(14)
[053] Speed error:
?? = (?? - ???? )(15)
[054] By adding augmented control signal uaugto (10), control law of iPI-CSMC is
15 given as in (16)
µ = -
??
??
???? ??
- ????? + ?????? + ???? ? ?? ?????? + µ??????(16)
[055] Structure of closed loop system is given by
???????? + ??µ?????? = ??? + ???? + ???? ? ?? ????(17)
[056] State variables x1 and x2 are defined as
20 ???? = ??(18)
???? = ? ?? ????(19)
[057] Sliding surface is defined as
?? = ?? + ?? ? ?? ????
??
?? = ???? + ??????(20)????? = ????(21)
????? = ??? = ???????? + ??µ?????? - ???????? - ???? ????(22)
- 13 -
[058] Complementary sliding surface
???? = ?? - ?? ? ?? ????
??
?? = ???? - ??????(23)
[059] Relationship between ?? and ????
???
??
+ (?? + ???? ) = ???
???
??
= ??? - ???? - ?????? (24)?????????? =
??
??
(???? + ????
5 ??)
?? ?
???????? = ????? + ???? + ????? (25)
[060] On putting the values of ??,???,???? , and???
??
, (26) is obtained
?? ?
???????? = 2????[???????? + ?????]?? ? ???????? = 2????[???????? + ???](26)
2?????????????? + ?????????? + ??µ?????? - ???????? - ???????????? = 0(27)
10 µaug comprises of two signals as in (28)
µ?????? = µ???? + µ???????????????????? (28)
For stability,?? ? ???????? = 0; therefore, (27) becomes (29)
2?????????????? + ?????????? + ??µ?????? - ???????? - ???????????? = 0(29)
Putting ???????? = ?????? in (23), (24) is obtained
?????? =
??
??
15 (???? - ????)???? - ???????? + ????????(30)
?????????????????????? is given by
µ???????????????????? = ?? ?????? ??
????????
??
??(31)
[061] A saturation function ??????(
????????
??
) is used here to mitigate the chattering
phenomenon. It is defined as follows:
?????? ??
????????
??
?? = ??
1, ???? ?? + ???? = ??
????????
??
, ???? - ?? < ?? + ???? < ??
-1, ???? ?? + ?? ?? = -??
20 (32)
From (30) and (31), ???????? is obtained as
???????? =
??
??
(???? - ????)???? - ???????? + ???????? + ?? ?????? ??
????????
??
??(33)
From (16) and (33), control law for iPI-CSMC is defined as in (34)
- 14 -
µ = -
??
??
?????? ??
- ??????? + ???? ? ?? ???? + ???????? ?? + ?? ?????? ??
????????
??
??(34)
[062] Variable speed hydropower is a recent approach where DFIM is used. An
intelligent controller is provided for hydro turbine control system by the
hybridization of iPI and CSMC.The intelligent controller provided for guide vane
opening in HTCS of a hydro generating unit is equipped 5 with asynchronous
generating units. The dynamic performance is improved, i.e., overshoot and settling
time by iPI-CSMC controlled hydro turbine. The settling time for startup process,
synchronous to subsynchronous, and super synchronous is reduced by 85, 47, and
25s, respectively, in comparison with PID, and the overshoot is also reduced.
10 Similarly, settling time for startup process, synchronous to subsynchronous, and
super synchronous is reduced by 10, 7, and 10 s, respectively, in comparison with
CSMC, and the overshoot is further reduced. It shall help in performing quick
changeovers of generating equipment from one mode to another, i.e., generation to
pumping and vice versa, and increase the revenue generation.
15 [063] To analyze the control performance of iPI-CSMC for GVO and the effect of
GVO on performance measure characteristics of 250 MW DFIM, a model of a
typical HTCS is created in MATLAB/Simulink platform. DFIM is operated in
generating mode with a rated speed of one p.u. (230.77 rpm) and an initial
mechanical power of 0.06 p.u. (15 MW) for the simulation. For RSC and GSC, the
20 switching frequency is 300 Hz and 500 Hz, respectively. 5e-4 sis used as the
sampling time. All the three PID, CSMC, and iPI-CSMC controllers are represented
in the model. The machine and controller parameters are listed in the appendix. In
the next part, the results for three distinct situations (starting process, synchronous
to subsynchronous, and super synchronous) are addressed.
25 [064] (a) Startup Process
[065] The starting mechanical power is 0.06 p.u. (15 MW) in this scenario. The
GVO of a hydro-turbine for PID, CSMC, and iPI-CSMC controllers is shown in
Fig. 3(a), 4(a), and 5(a), from which it can be seen that the PID controller takes 85
s to open 0.8 p.u. (80-82 percent) guide vane, the CSMC controller takes 22
- 15 -
seconds, iPI- CSMC takes 18 s, which is 4.7 times faster than the PID controller
and 1.2 times faster than the CSMC. The hydro-turbine power and torque for the
PID, CSMC, and iPI-CSMC controllers are shown in Fig. 3(b), 4(b), and 5(b),
respectively. The PID controller takes 120 s to attain (onep.u. i.e., 250 MW) steadystate,
the CSMC takes 45 s, and the iPI- CSMC takes 35 s. The 5 transient response
of actual power, torque, rotor currents, and stator currents of DFIM is shown in Fig.
3(c) - (f), 4(c) – (f), and 5(c) – (f) when hydro turbine controlled by PID, CSMC,
and iPI-CSMC, respectively. The true power, rotor current, and stator current are
estimated to require 120 s (hydro-turbine controlled by PID controller), 45 s (hydro10
turbine controlled by CSMC controller), and 35 s (hydro-turbine controlled by the
iPI-CSMC controller) to achieve steady-state. Therefore, it is (hydro-turbine
controlled by iPI-CSMC controller) 1.28 times faster than hydro-turbine controlled
by CSMC controller and 3.42 times faster than hydro-turbine controlled by PID
controller.
15 [066] (b) Synchronous to Subsynchronous
[067] In subsynchronous mode, the machine runs at a slower speed than its
synchronous speed, with the rotor drawing power from the grid to use driving
torque. When the machine achieves steady-state, the speed controller's reference is
altered smoothly for 5 s, from one p.u. (230.77 rpm) to 0.9 p.u. (207.6 rpm). The
20 GVO of a hydro-turbine for PID and CSMC controllers is shown in Fig. 5(a), 6(a),
7(a), from which it can be seen that the PID controller takes 45 s to open 0.4 p.u.
(40 percent) guide vane, the CSMC controller takes 12 s, and the iPI-CSMC
controller takes 9 s, which is five times faster than the PID controller and 1.33 times
faster than CSMC. The hydro-turbine power and torque for the PID and CSMC
25 controllers are shown in Fig. 5(b)-(c), 6(b)-(c), and 7(b)-(c). The PID turbine output
power has a 7.8% overshoot with a settling time of 60 s to achieve steady state of
0.5 p.u. i.e., 125 MW, the CSMC controller takes 25 s, and the iPI-CSMC controller
takes 20 s. The iPI-CSMC controller entirely removes the overshoot and has three
times faster settling time than the PID controller and 1.25 times faster than CSMC,
30 as shown in Table I. The transient response of actual power, rotor currents, and
- 16 -
stator currents of DFIM are shown in Fig. 5(d)-(f), 6(d)-(f), and 7(d)-(f). The test
findings indicate that the actual power, rotor current, and stator current approach
steady-state in 60 s (hydro-turbine controlled by PID), in 25 s (hydro-turbine
controlled by CSMC), and in 20 s (hydro turbine controlled by iPI-CSMC). The
steady-state time for a hydro-turbine operated by iPI-CSMC system 5 is three times
faster than PID controller and 1.25 times faster than CSMC controller. Furthermore,
compared to a PID controller and CSMC controller, the overshoot in actual power,
rotor current, and stator current of the DFIM was greatly reduced using iPI-CSMC,
as shown in Table II.
10 [068] (b) Synchronous to Super synchronous
[069] In super synchronous mode, the machine runs at a higher speed than its
synchronous speed, allowing electricity to flow into the grid. When the machine
achieves steady-state, the speed controller's reference is changed smoothly for 5 s,
from one p.u. (230.77 rpm) to 1.1 p.u. (253.847 rpm). The GVO of a hydro-turbine
15 for PID, CSMC, and iPI-CSMC controllers is shown in Fig. 9(a), 10(a), and
11(a),From which it can be deduced that the PID controller takes 20 s to open 0.96
p.u. (96 percent) guide vane, the CSMC controller takes 8 s, and iPI-CSMC
controller takes 6.5 s. The time taken by the iPI-CSMC controller is 3.07 times
faster than PID controller and 1.2307 times faster than CSMC controller. The
20 hydro-turbine power and torque for the PID, CSMC, and iPI-CSMC controllers are
shown in Fig. 9(b)-(c), 10(b)-(c), and 11(b)-(c). The PID turbine output power has
a 4.3 percent undershoot with a settling period of 45s to achieve steady state of 1.1
p.u. i.e., 275 MW, CSMC entirely removesthe undershoot and has 30s settling time,
iPI-CSMC controller has 20s settling time as shown in Table I. The transient
25 response of actual power, rotor currents, and stator currents of DFIM is shown in
Fig. 9(d)-(f), 10(d)-(f), and 11(d)-(f). The test findings indicate that actual power,
rotor current, and stator current achieve steady-state in 45s (hydro-turbine
controlled by PID controller), in 30s (hydro-turbine controlled by CSMC), in 20 s
(hydro-turbine controlled by iPI-CSMC). Here, it is concluded that iPI-CSMC is
30 2.25 times faster than PID controller and 1.5 times faster than CSMC, as shown in
- 17 -
Table II. Table I summarizes the improvement in time domain specification of GVO
and turbine output power. The impact of GVO on DFIM features is seen in Table
II. The overall performance of the HPP is greatly enhanced by iPI-CSMC in
comparison to PID and CSMC.
5
[070] The experimental setup consists of 2.2 kW DFIM coupled with 5 HP
separately excited dc machine used as prime mover. Hydroturbine characteristics
(controlled by PID, CSMC, and iPI-CSMC) are matched by controlling the torque
10 of the dc machine. Stator terminal of DFIM is connected to grid, and the rotor
terminal of DFIM is connected through a 2-channeled parallel-connected power
converter (10 kW, IGBT modules). In order to mitigate the circulating current
among the power converters,twomH interphase reactors are connected in between
the rotor and RSC. Switching frequency for both GSC and RSC is chosen as 5 kHz
15 with a deadband of 6 µs. To measure the stator and rotor currents, current sensors
(fluke i400s) are used. Rotor speed is obtained by using a Quadrature Encoder Pulse
(QEP) sensor of incremental encoder type with 512 encoder resolution lines. The
feedback of these sensors is integrated into ADC channel in real-time controller.
The details of the setup shown in Fig.12. Fig. 13(a) and (b) show that PID
20 controlled hydro-turbine takes 5.61 s to reach steady-state, i.e., one p.u. (2.2 kW
power, 4.5 A stator current, and 7.5 A rotor current), CSMC controlled hydroturbine
takes 2.6 s (shown in Fig. 14 (c) and (d)), iPI-CSMC controlled hydro
turbine takes 1.4 s. The iPI-CSMC controlled hydro turbine is four times faster than
the PID controller and 1.8 times faster than CSMC controller. Fig. 14 demonstrates
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test results for transition from synchronous to subsynchronous process. For that,
rotor speed is varied from one p.u. (1500 rpm) to 0.9 p.u. (1350 rpm) as represented
in Fig. 14(a). Fig. 14(a)-(f) shows stator currents, rotor currents, and real power of
DFIM for hydro-turbine controlled by PID, CSMC, and iPI-CSMC. It is inferred
that PID controller takes 2.5 s to reach steady-state (0.5 p.u. 5 power), CSMC takes
1.25 s, and iPI-CSMC takes 1.15 s. Fig. 15. represents test results for transition from
synchronous to super synchronous process. In this case rotor speed is varied from
one p.u. (1500 rpm) to 1.1 p.u. (1650 rpm) as represented in Fig. 15(a). Fig. 15 (a)-
(f) shows stator currents, rotor currents, and real power of DFIM for hydro-turbine
10 controlled by PID, CSMC, and iPI-CSMC. It is inferred that PID takes 2.0 s to reach
steady-state (1.1 p.u. power), CSMC takes 0.9 s, and iPI-CSMC takes 0.8 s. It is
observed from test results that the response of performance measure parameters of
DFIM becomes two times faster when hydro-turbine is controlled by CSMC
compared to PID, and overshoot is also reduced. On comparing the experimental
15 92898results with simulation results, similar changes are found in all performance
related parameters of the machine. These experimental results prove the robustness
and efficiency of iPI-CSMC designed for GVO. Further, the influence of GVO on
DFIM characteristics is tabulated in Table III. It is inferred that CSMC has 2.8 times
faster response during startup process, 2.26 times faster response during
20 synchronous to subsynchronous, and 1.75 times faster response during synchronous
to super synchronous than that of PID controller. In addition, overshoot is also
reduced significantly. The response time varies with respect to the different modes
of operations because of power variation (i.e., 0 kW to 2.2 kW for startup, 2.2 kW
to 1.1 kW for synchronous to subsynchronous, and 2.2 kW to 2.4 kW for
25 synchronous to super synchronous).
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[071] Numerous modifications and adaptations of the system of the present
invention will be apparent to those skilled in the art and thus it is intended by
the appended claims to cover all such modifications and adaptations which fall
within the true spirit and scope 5 of this invention. ,

WE CLAIM:

1. A control system to regulate guide vane opening (GVO) in hydro turbine control system (HTCS) of a variable speed hydropower plant (HPP) comprises
? a reservoir and turbine, with inlet valve and intake gates that can either be in a fully closed or fully open position to cutoff the water supply to the turbine and penstock,
? generator, with generator circuit breaker (GCB 2),
? Unit circuit breaker (UCB 1),
? unit transformer (3), excitation transformer (4),
? doubly fed induction machine (5),(DFID) converter including grid side converter (6) and rotor side converter (7) characterized in thatDFIM converter control consists of rotor side and grid side control strategies separately, and electromagnetic torque and reactive components of DFIM are controlled through rotor side controller and dc-link voltage, and reactive power component of grid are controlled through grid side controller
? guide vane (8),
? hydraulic governor control system (9) with asynchronous generating and the grid wherein the control of the output/speed of the unit is by adjusting the position of guide vane opening and are kept in any position between a fully closed and nearly fully open position and regulate the flow of water to the runner to match the required output at the existinghead using a closed-loop feedback controller (9)characterized in that asynchronous generating units provided for guide vane opening in hydro turbine control system of a hydro generating unit is equipped with.
2. The control system to regulate guide vane opening (GVO) in hydro turbine control system (HTCS) of a variable speed hydropower plant (HPP), as claimed in claim 1, wherein the stator terminal of DFIM is connected to grid, and the rotor terminal of DFIM is connected through a 2-channeled parallel-connected power converter (10 kW, IGBT modules)
3. The control system to regulate guide vane opening (GVO) in hydro turbine control system (HTCS) of a variable speed hydropower plant (HPP), as claimed in claim 1, wherein the response of guide vanes is 4.7 times faster by iPI-CSMC regulated hydro-turbine than PID controlled hydro turbine and 1.2 times faster than CSMCcontrolled hydro turbine.
4. The control system to regulate guide vane opening (GVO) in hydro turbine control system (HTCS) of a variable speed hydropower plant (HPP), as claimed in claim 1, wherein thesettling time and overshoot for all performance measures parameters of 250 MW DFIM are reduced by iPI-CSMC controlled hydro-turbine compared to PID and CSMC controlled hydro-turbine.