Improving the Behaviors of Wind - Diesel Hybrid System in Smart Grid by Using Statcom Cai tien chat lugng dieu khien he Statcom cho he lai Diesel - Gio dirng trong luai dien thong minh
Trang 1Improving the Behaviors of Wind - Diesel Hybrid System
in Smart Grid by Using Statcom
Cai tien chat lugng dieu khien he Statcom cho he lai Diesel - Gio
dirng trong luai dien thong minh
Bui Dang Thanh Hanoi University of Science and Technology - No 1 Dai Co Viet Str., Ha Noi, Viet Nam
Received: April 15, 2014; accepted October 28, 2014
Abstract
The paper presents studies of a wind-diesel hybrid system and the influence of mam factors on the quality of power in a smart grid A Statcom static compensation system is designed and simulated in Matlab in order to apply to the wind-diesel hybrid system The PI controllers are developed to compensate for the shortfall in power in the system A PSO (Particle Swarm Optimization) algorithm is used to optimize PI parameters The results obtained in tfie paper indicates the obvious effects of using Statcom in stabilizing the local smart grid
with traditional methods
Keywords: Statcom, PI controller, PSO, Wind- Diesel hybrid system, PWM
Tom tat
Bai bio trinh bay cac nghi§n cuv vi he lai Diesel-gid, inh hwang cua cic yeu to din chit lifong dien nang
cho h$ lai Diesel-gio Cac bd diiu khiin PI dwoc phit triin nhim bu lai cic thiiu hut cdng suit trong he thong Giai thu$t PSO duvyc ip dung de xac dmh b0 thdng so toi uv cho bd diiu khien PI Cic kit qui dat dum; trong bdi bio da chi ra hieu qua rd ret cua viec su" dung Statcom trong 6n dmh iwai di^n ci^c bg thong minh, ngoii
ra chat luxpng diiu khiin cua dien ip DC tren ty khi ap dung phieang phip tdi uv PSO da dwqfc cii thien dang
ki khi so sanh vai phuomg phap truyin thong
TCF kh6a: Bii tTnh Statcom, digu khiln PI, giai thuSt PSO he lai Diesel-gio, dieu che dp rpng xung PWM
1 Introduction to the instability of the source and the low inertia of
c , j r n j ^ j 4 cu J J generators in small power systems
Smart grid [ 1 ] is deiined as a set ot hardware and r J
sofhvare tools which are used to ttansmit power more Statcom (Static Synchronous Compensator) is a information instantaneously according to the actual performance and stability of the independent system needs Smart grid reaches high efficiency in power with the participation of wind power Basing on the fransmission line According to [2], the smart grid uses compensate qmckly for the temporary shortfall of the digital technology to optimize the use of energy, to reactive power as well as to improve performance and match "green" and smart energy sources to customers stability of wind power plants when there are through smart devices problems
Nowadays, the wind energy is a natural energy The PSO algorithm is applied to determine the source which has the largest reserve in the world The optimized parameters of PI confroUer in Statcom that exploitation of this energy in the near future will we apply to the wind-diesel hybnd system
certainly be stepped up basing on dominant advantages — - , • ^
i-, f, J T 1 he paper includes 5 sections After this
of this renewable and green energy source In some _ j - - ^ , , ,- , I , , ,, - • 1 J ^.u J mtruduction, section 2 presents the wmd-diesel hybnd areas where there is no national grid, the wind power ' ^ , , ^ ijuim will be used with diesel generators, and grid system; section 3 presents the synthesis of Statcom
^ , - , ^- -ir u J 1 ri i i.L- ' J J i conttoller Simulation results are given and analyzed
stabilization will be done locally at this mdependent - ^ „ , , , , • auaLy£.cu
„ , » - - - L T ^ f 11 I _ in section 4, followed by the cone usion
gnd Maintaining stability tor small-scale smart power •' systems using wind turbine is a technical challenge due
• Corresponding Author: Tel: (+844) 3868 351t
Trang 22 Wind - Diesel hybrid system
The wmd-diesel hybrid system is a system that
combines w^nd tairbmes and diesel generators The
wind-diesel hybrid system can be a new wmd-diesel
electrical system or wmd turbines integrated with an
available diesel electrical system contaming many
generators to form a distnbution grid The purpose of
using wind turbmes is to reduce the consumption of
diesel fuel; therefore, we can enhance economic
efficiency and envfronmental friendliness [3, 4]
During the operation process, the vnnd turbine
will suffer the impacts of environment such as
these make the power generated unstable If the
consumption loads ofthe power grid are asynchronous
elecfrical machmes, when there are problems with the
wmd source, these machines requires a large
consumption of reactive power from the grid The lack
of reactive power is the main cause of grid voltage
fluctuation, reducing the power factor of the grid,
affecting greatly the stability and quahty ofthe system
Statcom is an effective solution to this problem
When the Statcom is used to compensate for the
reactive power in distribution system, it is called
D-Statcom (Distribution- D-Statcom) Fast response is one
outstanding advantage ofthe D-Statcomin improving
the dynamic responses ofthe system [5]
In our research, a D-Statcom is used to
compensate for the reactive power and to adjust the
gnd voltage in the wmd-diesel hybrid system in the
case of 3-phase problems The simulation results show
that the use of D-Statcom improve evidently the
dynamic of the system In addition, the method of
determining the parameters for Statcom confroUer also
gives positive results
3 Synthesis of Statcom controller
3.1 Wind-diesel hybrid model
Model of Emergency Diesel Generator and Asynchronous Motor in SimPowerSystems in Matiab/ Simulink is used to simulate the wmd-diesel hybrid system in this research, which are described in Fig 2 The electncal source in Fig.2 is 3-phase power sources of 25kV, lOOOMVA,, Phase Fault and 3-Phase Breaker blocks are used to simulate the moments when there are problems with the wind source and cutting the wind source having problems off the gnd; Wind source is modeled by an induction motor (asynchronous machine ASM 2250HP), supplying the grid via a 2.4 to 25kV fransformer The diesel generator is simulated by a synchronous generator SM 3125MVA using diesel engine integrating automatic speed and voltage confrollers The diesel engine model includes asynchronous motors, a speed confroUer and a load The engine will run at a speed that can be adjusted via the throttle signal The throttle signal conttols directly the output torque generated by the engine and conttols indirectly the speed at that the engine is running Simulation parameters for diesel models are selected according to [4]
Fig 1 Wmd-diesel hybrid system
Trang 3Fig 4 Conttol two-loop structure of Statcom
Fig 5 Control diagram of Statcom
3.2 Designing D-STA TCOM
The connection diagram of STATCOM with a
typical disttibution grid shown in Fig 3:
Where Vas, Vbs, Vcs are voltage levels
generated by VSC, Ls characterizes the leakage
inductance of coupling transformer; Rs characterizes
the fransmission loss of VSC and couphng
ttansformer; Re characterizes the switching loss of
VSC and power loss on the capacitor; Vdc is the DC
voltage across the capacitor, Rl and Ll are the local
common coupling; and Van, Vbn, Ven, Rn, Ln are
values characterizing the distribution grid
Statcom is the phase angle conttoller of voltage
and current, so in our designs, we need a converter to
to the signal components in the rotating synchronous
reference system, where each cunent and voltage
vector is characterized by the length (module) and the
phase angle position, which are represented in an
orthogonal coordinate system d-q
The dynamic characteristics of D-Statcom is a
multi-variant process with many input and output
variables To simphfy the confrol process and to adjust
easily parameters of conttollers, we build a
double-The muhi-variant conttol problem in the kinematic process of D-Statcom system is converted into die mvanant conttol problem, in this case they are two conttol loops VDC and |vl| In each confrol loop
we use a cascade conttol with two sub-conttol loops: Adjusting the inner current and outer voltage When there are differences between the actual voltage amplitude |vl| and installed value |vl| *, PI2 conttoller generates the signal to set current iqs * to adjust the reactive power ofthe load
The basic block diagram of a D-Statcom conttol system is described in Fig 5
The 3-phase voltage signal Vabc, 3-phase current labc are put mto the voltage and cunent measuring system, they are calculated by abc-dq ttansformation (the synchronous reference signal sin(ojt) and cos((Dt) the output of the measuring block is the signal with
voltage amplitude Vmag and cunent components Id, Iq,
system
AC vohage regulator maintains AC voltage
Vmag equal to the reference value Vac ref
DC voltage regulator maintains the voltage across the capacitor equal to the reference value Vdc ref
The iimer current conttoller contains two cunent conttollers in d axis and q axis The outputs of
conttollers are Vd, Vq used to synthesize PWM
voltage Cunent set point Iq ref is taken from AC voltage regulator Current set point Id is taken from
DC voltage regulator
The amplitude modulation index m and phase
angle modulation (p calculated from the voltage
component Vd, Vq is put into the PWM inverter to
generate sine wave at the output
For the dynamic process of D-Statcom which we are studying, the most important requirement of the confrol problem is to eliminate static errors in steady state For simplicity, the PI controller is used for cunent and voltage confrol loops [4, 5]
3.3 PSO algorithm
PSO is proposed by Kennedy, Eberhart and Shi
to optimize a problem by trying to improve a candidate solution with regard to a given measure of quality [6, 7] This algonthm was modeled on the foraging behavior of buds Initially, the birds fly in a random direction During operation, some individuals can fmd
a food contamer Depending on the amount of food more or less those they can that send information to other individuals in the neighboring and spread
Trang 4throughout the population Based on this information,
appropriate to look for where is the most foods PSO
algorithm maintains a swarm of particles which is
similar to a flock of bfrds, while each particle similar
to an individual in the herd The particles move in the
search space of many dimensions, in which the
position of each particle is adjusted according to its
own experience and that of all other particles, thereby
find the best target value
Setx,(t) is the position ofthe particle in the search
space R„ at time I From a random position x,(0) in the
search area, after each time step, the position of the
velocity vft):
(1)
rMm-':.(t)]
(2)
where, w is the inertia weight; ci is an individual
acceleration constant and ci is a global acceleration
constant; ri, r2 are random values taking from an
uniform distribution in the range (0, 1); yi(t) is an
optimal individual position of the particle ;, ^'- •' is a
global optimal position
For minimizing the objective fiinction, PSO
algorithm is earned out according to the steps shown
in Fig 6,
In our study, PSO is applied to determine the PI
parameter Z^[Kp K/\ following the objective fimction:
x,(l+!)=x,(l)+v,(l+l)
where Vdc is voltage on capacitor, V^^' is a set poir
value
4 Simulation Results
4.1 Simulation
We assume that at / = 0.2s, wind have
disturbance Until I = 0.3s, wind is left of grid 4.2 Model parameters
The D-Statcom model is studied with a power ol
±3Mvar and it uses voltage PWM invertor from 2 ports
of IGBT DC voltage is applied to capacitor of I0000|iF The terminals of D-STATCOM arc connected parallel with grid by ttansformer, type 800/2400V A-Y
Modulation frequency of PWM is 1.68kHz; Grid voltage: Vrms line-line = 2.4 kV; Source frequency;
y^SOHz; F„ ™/=lp.u, Vdcrer2250y; F^ PI controllei parameters: Kj^ 0.001; K, = 0.15, Id, Iq PI conttoller parameters: Kp = 0,8, Ki = 200
Circuits are simulated m SIMULINK
discrete-time with sample discrete-time T, ^ 5ps 4.3 Simulation results
By using the simulation parameters above, the results present in Fig 8
/(z) = ;.''(c'-i'.c)'dt ( 3 )
nitialize a random position and velocity
for particles
Evaluate a objective function for each
p a r t i c l e / = ^ 2, , n^
If f(xj<f(yj then y=>
r iff(yJ<f(9)Vtien y=y,
I Update the v
Update the position following (1) I
Fig 7 Description of disturbance in Wind-diesel system
H '• '•• -^ 4
Fig 8 Voltage grid amplitude in case using Statcon
Trang 5m
Fig 9 DC voltage in capacitor
Fig 10 Companson of DC voltage in capacitor in case
using PSO and default
The voltage grid amplitude m case of using the
D-Statcom is more stable When a grid disturbance
happens, Statcom compensates quickly the shortfall in
power in the system The evolution of DC voltage in
capacitor is show in Fig 9
By applying the PSO algorithm with parameters'
«i=3; w IS chosen from 0.001 to 0.012, c/-C3=0.0005;
and repeated steps is 3, we get the conttoller PI
parameters aS'
K, = 0.0069, K/ = 0,1903
The evolution of DC voltage in capacitor is
presented in Fig 10
The results indicate the conttoller parameters of
PSO method are much better than default method
5 Conclusion
The obtained results above clearly indicate the
effectiveness of the use of Statcom for stabilizmg
locally smart grid
Ll addition, the synthesis of PI confrollers for
Statcom using PSO algorithms has improved the
conttol quaUty; it is possible to reduce significantly the ttansition time and steady-state when companng with default method
If these results continue to be successfiilly implemented in practice, it would be the most promising products
Acknowledgments
The authors would like to thank the Institute for Conttol Engineering and Automation- ICEA/HUST for supporting their research activities The authors also thank the Mmistry of Education and Training of Viet Nam for supporting their research activities in the
project entitled "Studying, designing and building the wireless smart sensor network for smart grid,
B2014-01-80"
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