Summary of the invention
The advantages such as particle cluster algorithm is simple to operate with it, fast convergence rate are to carry out in multi-objective optimization question application wider, but when in algorithm, inertia weight coefficient is larger, particle may produce to the fine search of optimum solution the adverse consequences that search precision is not high owing to lacking; By adopting adaptive inertial coefficient to adjust inertia weight coefficient, larger inertia weight value is conducive to jump out local optimum, is adapted to search volume to develop on a large scale; Less inertia weight value can improve the precision of algorithm and be beneficial to algorithm local convergence, is applicable to exploitation among a small circle; Conventionally PSO algorithm only relies on optimal value and does not make full use of the information of other particles in iterative process, and when problem is comparatively complicated, algorithm is easy to be absorbed in local optimum.For fear of the generation of this situation, the weighted mean value with the individuality optimum of all particles in the speed of particle cluster algorithm and position updating process replaces global optimum, considers that all individualities adjust speed and the position of particle to the guidance quality of group activity; In standard particle group algorithm, only stipulate the limit value of particle rapidity, but particle position limit value has not been determined, made algorithm easily be absorbed in local optimum; By the renewal of position being carried out to fuzzy control, can effectively avoid being absorbed in local optimum.
its beneficial effect is:
1) this algorithm has the population of avoiding and is absorbed in local optimum, and inertia weight is carried out to adaptive control energy;
2) unified infield and the corresponding parameter of optimizing active and passive filtration unit in given distribution system, reduce the loss of system, line voltage current distortion rate is controlled in national regulation limit value, in the situation that guaranteeing power distribution network safe and stable operation, reach the object of filter first cost minimum;
3) greatly reduce quantity and the capacity of required current transformer, reached good filter effect and optimistic economic benefit, there is actual application value;
Below in conjunction with accompanying drawing, the invention will be further described.
embodiment
The search volume of a D dimension, by m the molecular population of grain
, the
ithe position of individual particle is
, present speed is
; In each iteration, the desired positions that particle individuality searches is
be called individual optimum and be denoted as P
best; In colony all particle search to desired positions be
be called global optimum, be denoted as G
best.Particle upgrades respectively oneself speed and position according to formula (1) and formula (2):
(1)
i = 1,2,…,M (2)
tfor iterations; c
1and c
2for the study factor, rand
1and rand
2it is [0,1] interval interior equally distributed random number;
wfor inertia weight.The speed of particle is limited to [v
max, v
max] between
Adopt adaptive inertial coefficient to adjust inertia weight coefficient:
(3)
In formula: λ regulates
wthe positive coefficient of pace of change,
tfor current iteration number of times,
w 0 for the upper limit of w (t), t
maxfor maximum iteration time; Larger
wvalue is conducive to jump out local optimum, is adapted to search volume to develop on a large scale; Less
wvalue can improve the precision of algorithm and be beneficial to algorithm local convergence, is applicable to exploitation among a small circle
The optimum weighted mean value of individuality of all particles is expressed as:
(4)
be weight vectors, reacted the percentage contribution of i particle and met
, the formula that the position of particle is upgraded becomes:
(5)
In standard particle group algorithm, only stipulate the limit value of particle rapidity, but particle position limit value has not been determined, made algorithm easily be absorbed in local optimum; The renewal of position is carried out to fuzzy control herein and can effectively avoid being absorbed in local optimum, formula 5 is carried out to fuzzy control and draw:
(6)
(7)
Wherein,
for
sshape subordinate function,
tbe a given threshold values, with t
maxclosely related, a, c is constant.When
time,
get 1, during this time, the variation of particle position is larger; When t>T, the change of particle will slow down, and while arriving certain iterations, the variation of particle can add hurry up again, can effectively avoid being absorbed in local optimum.
The mathematical model that in the power distribution network of generation of electricity by new energy, filter unification is distributed rationally
Objective function
(1) harmonic voltage resultant distortion rate
With each node harmonic voltage resultant distortion rate of power distribution network
tHDU i mean value be objective function, that is:
(8)
h=(2,3…H) (9)
In formula,
ifor grid nodes label, N is the total nodes of network;
hfor overtone order, Y
hi be
inode
hthe admittance matrix of subharmonic; U
li for node
ifundamental voltage effective value, U
hi for node
i's
hsubharmonic voltage effective value;
u tHUUifor node
ivoltage harmonic aberration rate
(2) filter economy
The mathematical model of passive filter and active filter show that the economy that the objective function of distributing rationally is filter is minimum, that is:
(10)
In formula,
,
whether represent installing filter branch road;
f(Q
cNij) the expression expense of passive filter and the funtcional relationship of branch road capacitor rated capacity;
f(S
ni) relevant with the capacity of compensation harmonic with the expense of active filter, funtcional relationship is as follows:
(11)
(12)
Q
cNijbe the jot constant volume of the installation capacitor of i node j bar branch road, S
nithe capacity that represents active filter; Coefficient a
0ij, a
1ij, b
0ij,b
1ijchoosing value adopt market price decision method to determine effectively to avoid blindness
The rated capacity of passive filter is comprised of fundamental wave reactive power capacity and harmonic wave reactive capability.Get nonlinear-load power factor 0.65~0.85 herein.Passive filter is at node
ithe specified installed capacity of smallest capacitor be:
(13)
(14)
In formula, Q
1 fundamental wave reactive power capacity; Q
hi harmonic wave reactive capability; C
i for node
ithe capacitance of wave filter;
Active filter compensation capacity S
i be decided by compensated total harmonic current effective value, that is:
(15)
In formula, U
1i be
ithe fundamental current of node; U
1i be
iindividual node
hinferior voltage effective value; I
hi be
inodes active filter compensate
hsubharmonic current value; Capacity S
i irrelevant with fundamental current;
(3) general objective function
Above-mentioned distributing rationally is typical multiple goal, non-linear, uncertain combinatorial optimization problem.It is impossible making above-mentioned multiple objective function reach in actual applications minimum value simultaneously, can only be by the relation between coordination function, make as far as possible both to reach more excellent, above-mentioned two indexs are normalized, can solve the skimble-scamble problem of the order of magnitude between each target
(16)
(17)
Limit
,
value between 0~1, adopts the mode of linear weighted functions to obtain general objective function to two objective functions to be:
(18)
In formula
for the weight of (1) (2) two objective functions, meet
, and
,
;
Constraint condition
(1) in searching process, the constraint of network harmonic trend:
(19)
In formula, C
tHDUthe limit value that represents the total percent harmonic distortion of voltage.According to GB GB/T14549-93 regulation, calculate
. the voltage distortion rate limit value of the power distribution network national regulation of different electric pressures is different, and general public electric wire net harmonic limits and line voltage grade are closely related, and electric pressure is higher, and Harmonic is stricter
(2) safe operation of passive filter constraint
Because harmonic wave has harm to capacitor itself, therefore, when passive filtering branch road is designed, should consider the impact of harmonic wave on wave filter rated current, voltage and capacity, following formula is voltage, electric current and the capacity-constrained in passive filter branch road:
(20)
(21)
(22)
The electric current of general capacitor can not overrate 135%, in formula, K
u , K
i , K
q be respectively permission piezoelectric voltage, excess current and the overcapacity coefficient of capacitor
(4) safe operation of active filter constraint
The capacity-constrained of active filter:
(23)
The overcapacity coefficient K that active filter allows
s represent
In sum, the Parametric optimization problem of active filter and passive filter is meeting under above constraint condition exactly, makes general objective function reach the search problem of optimum solution.
The structure of fitness function
According to above-mentioned optimization problem, adopt mixing penalty function method that above-mentioned Solution of Nonlinear Optimal Problem is become to unconstrained optimization problem herein, that is:
(24)
being penalty factor, is an indefinite array successively decreasing; h
i (X) be
iindividual equality constraints functions
i=(1,2 ..., l);
be
jindividual inequality constrain function, j=(1,2 ..., k), herein
initial value gets 1, order
, and C=1/2; By constantly reducing penalty factor, carry out taking turns without Constrain Searching, every constraint condition being met all comes in obstacle item, the constraint condition being not being met is all arranged in penalty term, from the inside and outside optimum solution of approaching on border, the optimum solution finally obtaining is exactly the optimum solution of single goal belt restraining problem respectively.