CN105740966A - Expansion planning method of power distribution network containing distributed power sources - Google Patents

Abstract

The invention relates to an expansion planning method of a power distribution network containing distributed power sources. The method includes the following steps of: calculation of distributed power source maximum capacity Pmin which can be absorbed by an existing power distribution network; load prediction; source load coordination; source network coordination; and load and network coordination. With the method of the invention adopted, and the power sources and a power grid can be effectively combined, can complement each other's advantages, and develop in a coordinated manner; the specific connection positions of the distributed power sources can be determined under a condition that distributed power source planned connection capacity is given; power grid expansion investment cost can be decreased; adverse effects of the distributed power sources on the grid power can be minimized; the benefits of the grid power can be maximized; coordination among load prediction amount, distributed power source planned capacity, substation capacity and line current carrying ability is fully considered; and the active absorption capacity of the distributed power sources can be improved with load growth requirements satisfied. The method has a high practical value.

Description

A kind of power distribution network Expansion Planning method containing distributed power source

Technical field

The present invention relates to the technical field of distribution network planning method, especially a kind of power distribution network Expansion Planning method containing distributed power source.

Background technology

Fast development along with economic growth and industrial technology, society's power consumption is also increasing sharply, when existing network can not meet local growing workload demand or certain user power supply reliability is proposed requirements at the higher level time, it is necessary to system is carried out corresponding Expansion Planning.The main task of distribution system Expansion Planning is to determine the system Construction scheme of optimum according to the result of Spatial Load Forecasting in planning period network and the basal conditions of existing network, under the premise meeting load growth and safe and reliable supply electric energy, make the construction of distribution system and operating cost minimum.Traditional extended method usually increases the purchase of electricity of normal power supplies, namely under meeting the premise that future load growth requires and the network operation retrains, find one group optimum decision variable (such as transformer station position and capacity, the path of feeder line and size etc.), make the expense sums such as investment, operation, maintenance and network loss minimum.

Distributed power generation is a kind of novel, rising generating and comprehensive utilization of energy mode, it has reducing investment outlay, reduces loss, improves the advantages such as system reliability, efficiency is high, variety of energy sources is various, its position feature flexible, scattered has adapted to dispersion electricity needs and resource distribution admirably simultaneously, it may not only be applied to power peak regulation, builds stand-by station or cogeneration power station, outlying district Independent Power Generation can be realized again, obtain the extensive concern in power industry field in recent years.Along with the appearance of distributed power generation, planning personnel has had more more options when formulating increase-volume scheme, is not only newly-built transformer station and feeder line, it is also possible to distributed power generation is included in new selection, to realize significantly more benefit.Distributed power generation and electrical network are combined be reduce investment outlay cost, improve efficiency of energy utilization, strengthen the important way of Power System Reliability and motility.Distributed power generation continue rapidly growth momentum and its in systems irrational a large amount of infiltration will produce to have a strong impact on to electrical network, from this aspect, also require that the distribution network planning taking into account distributed power generation must be carried out prospective research by Electric Power Network Planning personnel.

When substantial amounts of distributed power source occurs in programme, substantial amounts of change at random makes the complexity of system greatly increase, traditional planing method does not have the ability of abundance to solve the planning problem comprising distributed power source, this is primarily due to traditional planing method and has all been simplified by planning problem to some extent, lacks good processing method for the uncertain factor being difficult to quantitative expression of objective reality in planning.It is mainly manifested in the following aspects:

(1) appearance of distributed power source can make the load prediction of power system, planning and the operation will in the face of the uncertainty bigger than the past.Traditional distribution network planning is generally carry out according to the step of " load prediction one power source planning one network planning ".When load prediction, not only it is to be understood that load Prediction of Total value, it will also be clear that the rule of power load distributing and growth.And substantial amounts of user installation distributed power source provides electric energy for it, necessarily the load growth pattern of whole power system is produced impact so that distribution network planning personnel are more difficult to the growth pattern of Accurate Prediction load, thus distribution network planning is impacted.

(2) distribution network planning generally considers 5～20 years, in this time limit, often assumes that network load increases year by year, and new middle pressure, low pressure node constantly occur, it is necessary to increases and builds one or more electric substations.Owing to the dynamic attribute of planning problem is with its dimension closely related (generally several thousand nodes need to consider) simultaneously, if many electromotor nodes occur again so that the network arrangement scheme (can so that the minimum scheme of construction cost, maintenance cost and electric energy loss) searching out optimum in all possible network structure is just more difficult.

(3) for wanting to install the user of distributed power source or independent power producer at power distribution network, they with think there is certain conflicting between the existing safety of maintenance system and the constant power distribution network company of quality level.Because having a large amount of distributed power source to access distribution system to be incorporated into the power networks; distribution network system structure will be produced profound influence by this; the dependence of big power station and transmission of electricity is gradually reduced; original one-way electric power feed characteristics of tidal flow there occurs change, and a series of global questions including Voltage Cortrol, reactive balance, relay protection etc. are by the operation of influential system.In order to safeguard the safe and stable operation of electrical network, it is necessary to enable distributed power source to accept scheduling.Realize this target; it is accomplished by by power electronic equipment its control carrying out necessity and adjustment; distributed power unit is integrated in existing distribution system; this not only needs to transform existing electrical power distribution automatization system, also will by passive to actively managing electrical network (Voltage Cortrol, protective policy, interference and interface problem).

Additionally, the variation of the machine set type of distributed power source and the adopted energy thereof so that in power distribution network, how to determine rational power supply architecture, how to coordinate and effectively utilize the problem that all types of power supplys becomes in the urgent need to address.

Distributed power source rationally accesses power distribution network and can be effectively improved distribution network voltage, reduces system active power loss, improve system loading rate；Whereas if on-position and capacity are unreasonable, then can affect the safe and stable operation of power distribution network.How distributed power source configuration is coordinated mutually with distribution network planning, to being effectively improved resource utilization, ensureing that power grid security reliability service is significant.

Summary of the invention

The shortcoming that the invention solves the problems that above-mentioned prior art, it is provided that a kind of power distribution network Expansion Planning method containing distributed power source that cost is less, more efficient.

This invention address that the technical scheme that its technical problem adopts: this power distribution network Expansion Planning method containing distributed power source, specifically comprise the following steps that

(1) the distributed power source heap(ed) capacity P that existing power distribution network can be dissolved is calculated_min, in this, as the foundation weighing existing power distribution network maximum bearing ability；

(2) load prediction is carried out, it is determined that the loading P that planning level year is local_L, determine, according to resource distribution and geographical environment situation, the distributed power source capacity P that planning accesses_DG；

(3) source lotus is coordinated: compare loading P_LWith distributed power source capacity P_DGIf, P_DG>P_L, illustrate that distributed power source capacity can not be dissolved by local load completely, go to step (4)；If P_DG<P_L, illustrate that distributed power source capacity can be dissolved by local load completely, go to step (5)；

(4) source net is coordinated: compare distributed power source capacity P_DGWith smaller value P_minIf, P_DG<P_min, illustrate that existing power distribution network can bear the distributed power source of access, go to step (6)；If P_DG>P_min, illustrate that distributed power source capacity exceedes existing power distribution network ability to bear, it is necessary to increase substation capacity or newly-built circuit；

(5) lotus net is coordinated: compare loading P_LWith smaller value P_minIf, P_L<P_min, illustrate that existing power distribution network disclosure satisfy that the growth of load, it is not necessary to enlarging；If P_L>P_min, what load was described grows beyond existing power distribution network ability to bear, it is necessary to increase substation capacity or newly-built circuit；

(6) according to natural resources distribution and geographical environment situation, determine the position candidate allowing to access distributed power source, when meeting electric power netting safe running, determine on-position and the capacity of distributed power source according to the workload demand on circuit and current-carrying capacity size.

The invention have the advantages that: the present invention makes power supply effectively be combined with electrical network, have complementary advantages, coordinated development, when given distributed power source plans access capacity, determine the on-position that distributed power source is concrete, save electrical network extension cost of investment, to minimize the distributed power source adverse effect to electrical network, maximize its benefit, fully take into account load prediction amount, distributed power source planned capacity, cooperation between substation capacity and line energizing flow ability, the active digestion capability of distributed power source can be improved again while adapting to load growth, there is important practical value.

Accompanying drawing explanation

Fig. 1 is the power distribution network Expansion Planning flow process containing distributed power source；

Fig. 2 is the geographical wiring diagram after simplifying；

Fig. 3 is distributed power source geographical position and candidate's access node.

Detailed description of the invention

The invention will be further described below:

This power distribution network Expansion Planning method containing distributed power source, specifically comprises the following steps that

(1) the distributed power source heap(ed) capacity P that existing power distribution network can be dissolved is calculated_min, in this, as the foundation weighing existing power distribution network maximum bearing ability；

(2) load prediction is carried out, it is determined that the loading P that planning level year is local_L, determine, according to resource distribution and geographical environment situation, the distributed power source capacity P that planning accesses_DG；

(3) source lotus is coordinated: compare loading P_LWith distributed power source capacity P_DGIf, P_DG>P_L, illustrate that distributed power source capacity can not be dissolved by local load completely, go to step (4)；If P_DG<P_L, illustrate that distributed power source capacity can be dissolved by local load completely, go to step (5)；

(4) source net is coordinated: compare distributed power source capacity P_DGWith smaller value P_minIf, P_DG<P_min, illustrate that existing power distribution network can bear the distributed power source of access, go to step (6)；If P_DG>P_min, illustrate that distributed power source capacity exceedes existing power distribution network ability to bear, it is necessary to increase substation capacity or newly-built circuit；

(5) lotus net is coordinated: compare loading P_LWith smaller value P_minIf, P_L<P_min, illustrate that existing power distribution network disclosure satisfy that the growth of load, it is not necessary to enlarging；If P_L>P_min, what load was described grows beyond existing power distribution network ability to bear, it is necessary to increase substation capacity or newly-built circuit；

(6) according to natural resources distribution and geographical environment situation, determine the position candidate allowing to access distributed power source, when meeting electric power netting safe running, determine on-position and the capacity of distributed power source according to the workload demand on circuit and current-carrying capacity size.

Distributed power source can affect grid nodes voltage, Line Flow, short circuit current, reliability etc. after accessing power distribution network, on-position and the capacity of influence degree and distributed power source have substantial connection, therefore reasonably select the position of distributed power source access and capacity particularly significant.When given distributed power source plans access capacity, it is determined that the on-position that distributed power source is concrete.Initially set up power distribution network Expansion Planning model, be described in detail below:

1. economy objectives function

It is generally minimum for target with Financial cost that distributed power source accesses power distribution network, wherein mainly includes newly-built circuit cost, line loss expense and interruption cost three part, and therefore object function is:

$\begin{array}{c}\begin{array}{cc}\min & F_{\cos t}=C_L+C_{loss}+C_{outage}\end{array}\\ =\underset{i=1}{\overset{n_l}{\&Sigma;}}{C}_{Pl}{l}_i+\underset{i=1}{\overset{n_l}{\&Sigma;}}{C}_{PE}{\mathrm{\&Delta;P}}_{li}T+EENS\&CenterDot;C_{PE}\end{array}---\left(1\right)$

In formula, C_LCost for newly-built circuit；C_lossFor line loss expense；C_outageTake for loss of outage；n_DGFor accessing the distributed power source number of power distribution network；C_DGiCost of investment (ten thousand yuan) for i-th distributed power source；C_PlCost (unit/km) for unit length circuit；l_iIt is i-th newly-built line length (km)；C_PEIt is unit price of power (unit/kW)；ΔP_liActive loss (kW) for i-th line road；T is that circuit runs the time (h)；EENS, for lacking delivery (kWh), represents by circuit cutting load amount after out-of-limit.

2. safety constraint

Distributed power source access after power distribution network also need to meet N-1 criterion, namely in network arbitrary independent component cut because breaking down after should not cause other apparatus overloads, therefore access scheme result must be fulfilled for N-1 verification:

m∈Ω_N-1(2)

Wherein, m represents solution to model；Ω_N-1Represent the set of access scheme meeting N-1 verification, be made up of with the constraint of equipment limit electrical network trend Constraints of Equilibrium under different faults.

It is described in detail below by concrete example:

For a certain power supply area, it is given at distributed power source herein and plans when access amount is determined, the scheme of its best on-position.Geographical wiring diagram after simplification is as in figure 2 it is shown, electric pressure and the rated capacity of this region Zhong Ge transformer station are listed in table 1.

Table 1 transformer substation voltage grade and rated capacity

When B, C, D transformer station causes full cut-off because breaking down, transfer a load onto adjacent lines by interconnection switch, adjacent A transformer station continue this sub-load is powered.Calculating load factor and the N-1 check results of respective lines after three transformer station's full cut-off generation loads shift respectively, result is as shown in table 2.

The load factor of circuit and N-1 check results after the transfer of table 2 load

As shown in Table 2, when D transformer station has a power failure, load will more than A substation capacity after transferring to three lines, if accessing distributed power source at three lines, then the distributed power source capacity needed is relatively big, and cost of investment is high, considering from economy point, proper extended method is to increase substation capacity；When B transformer station and C transformer station have a power failure, after load transfer, a line and two wires load factor increase rapidly, it may be considered that access distributed power source on this two lines road to increase the thermally-stabilised nargin of circuit, alleviate line energizing flow pressure, improve the digestion capability of distributed power source simultaneously.

Backlands district, Ji wind-force is abundant, and distributed wind-power generator quickly grows, and accounts for local power load up to more than 80% at some region installed capacity of wind-driven power.A transformer station present position is positioned at small towns, power load is relatively small, and distributed power generation development is very fast, therefore will appear from the distributed power source rate of increase situation more than load growth rate the coming years, namely planning that the distributed power source capacity of access is more than local loading, distributed power source is reversely to grid transmission.According to historical statistics data and load prediction data, according to the load growth rate of annual 1%, it is up to 6.08MW to the year two thousand twenty A transformer station load, the distributed power source capacity that local planning accesses is 15MW, but the maximum distributed power source capacity that can dissolve of this region rack is only 12.12MW, and the distributed power source heap(ed) capacity therefore accessed should be 12.12MW.In order to improve system economy and power supply reliability, it is necessary to the on-position of distributed power source is optimized.

If the distributed power source of planning all accesses a certain bar circuit, then there are three kinds of situations: only access a line, only access two wires or only access three lines.Calculating respectively under these three situation, the load factor of corresponding line, result is as shown in table 3:

Line load rate after the access of table 3 distributed power source

As shown in Table 3, after distributed power source is accessed in a line and two wires, line load rate changes greatly and exceedes nominal load, this is because the distributed power source capacity accessed is relatively big, exceeds well over the former load of circuit, and trend is flowed to electrical network by load bus, causes circuit overload；And three specific electric load amounts are relatively big, the distributed power source capacity of access counteracts sub-load amount, and the active power that circuit transmits and reactive power reduce so that load factor reduces.If distributed power source only accesses a line or two wires, circuit will transship, and wire will damage because of overheated, will be enlarged by accident scope under serious conditions, threatens the safe and stable operation of whole system.It is therefore desirable to is made rational planning in the on-position of distributed power source, when meeting power distribution network safe and stable operation, it is ensured that improve the digestion capability of distributed power source while local growth load need for electricity.

According to above analysis, distributed power source conveniently accesses a line or two wires.Considering local resources distribution and geographical environment situation, distributed power source present position is as it is shown on figure 3, two lines road is respectively arranged with the both candidate nodes of four accessible distributed power sources.

According to the economy model that the distributed power source access point set up above optimizes, in order to reduce the cost of newly-built circuit, distributed power source is typically chosen line attachment nearby.According to Fig. 3, the access node of candidate is the node 2 on a line and the node 6 on two wires.Only consider that an access amount is the distributed power source of 12.12MW herein.Assume that distributed power source present position is identical with the distance of node 6 to node 2, then newly-built circuit cost C_LAlso identical.Therefore only need to comparing total losses and the cutting load amount of three-line under two kinds of access schemes, result is listed in table 4.

Table 4 distributed power source accesses three-line total losses and the cutting load amount of difference

As shown in Table 4, although two kinds of distributed power source access schemes are satisfied by N-1 criterion, but during access node 2, circuit between node 2 and A transformer station occurs overload to need the load on excision circuit one line, access node 6 does not then have circuit overload without cutting load, and line loss is less than access node 2, therefore considering from economy and safety perspective, distributed power source is more suitable for accessing the node 6 on two wires.

According to above-mentioned distributed power source access scheme, under the mode without increasing substation capacity or newly-built circuit, it is possible to meet the need for electricity increasing load, save cost of investment, there is good economic benefit, be a kind of feasible embodiment in Practical Project.

Angle from economy and safety, it is proposed that a kind of distributed power source considering the maximum digestion capability of rack accesses power distribution network scheme.Initially set up a kind of maximum digestion capability computation model of distributed power source based on trend constraint, then the summation of electric generation investment cost, newly-built circuit cost, line loss expense and interruption cost is minimum for target in a distributed manner, it is verified as constraints and establishes power distribution network access power distribution network Optimized model with node voltage, line energizing flow, power-balance, N-1, and then obtain the best access scheme of distributed power source.With the Ji a certain power supply area of NORTEL net for example, result shows under the premise that distributed power source planned capacity is determined, utilizes this method can obtain more rational distributed power source on-position, has important practical value.

In addition to the implementation, the present invention can also have other embodiments.All employings are equal to replacement or the technical scheme of equivalent transformation formation, all fall within the protection domain of application claims.

Claims (1)

1. the power distribution network Expansion Planning method containing distributed power source, is characterized in that: specifically comprise the following steps that

(1) the distributed power source heap(ed) capacity P that existing power distribution network can be dissolved is calculated_min, in this, as the foundation weighing existing power distribution network maximum bearing ability；

(2) load prediction is carried out, it is determined that the loading P that planning level year is local_L, determine, according to resource distribution and geographical environment situation, the distributed power source capacity P that planning accesses_DG；

(3) source lotus is coordinated: compare loading P_LWith distributed power source capacity P_DGIf, P_DG>P_L, illustrate that distributed power source capacity can not be dissolved by local load completely, go to step (4)；If P_DG<P_L, illustrate that distributed power source capacity can be dissolved by local load completely, go to step (5)；

(4) source net is coordinated: compare distributed power source capacity P_DGWith smaller value P_minIf, P_DG<P_min, illustrate that existing power distribution network can bear the distributed power source of access, go to step (6)；If P_DG>P_min, illustrate that distributed power source capacity exceedes existing power distribution network ability to bear, it is necessary to increase substation capacity or newly-built circuit；

(5) lotus net is coordinated: compare loading P_LWith smaller value P_minIf, P_L<P_min, illustrate that existing power distribution network disclosure satisfy that the growth of load, it is not necessary to enlarging；If P_L>P_min, what load was described grows beyond existing power distribution network ability to bear, it is necessary to increase substation capacity or newly-built circuit；

(6) according to natural resources distribution and geographical environment situation, determine the position candidate allowing to access distributed power source, when meeting electric power netting safe running, determine on-position and the capacity of distributed power source according to the workload demand on circuit and current-carrying capacity size.