CN104300571B - Distributed Generation in Distribution System maximum injection power determines method - Google Patents

Abstract

The invention discloses a kind of Distributed Generation in Distribution System maximum injection power and determine method, its step is to determine the power constraint limit value S of adverse current_inv, determine voltage pulsation limit value U_lim, draw maximum short circuit current increment Delta I that distributed power source allows to cause_lim, in distribution line or bus, input the injecting power S of distributed power source₀, verify injecting power S₀Whether meet adverse current constraints, verify injecting power S₀Whether meet voltage pulsation constraints, and checking injecting power S₀Whether meet short circuit current constraints, if injecting power S₀It is satisfied by above three constraint, then increases injecting power, until occurring that any one constraint is the most satisfied, the injecting power of output previous round.The inventive method is simple, scientific and reasonable.

Description

Distributed Generation in Distribution System maximum injection power determines method

Technical field

The invention belongs to power system distributed power source and field of distribution network, particularly relate to distributed electrical in a kind of power distribution network Source maximum injection power determines method.

Background technology

Distributed power source generally refer to generated output thousands of watts to 50 megawatts miniaturization, modularity, distributing, layout For the compact electrical generating systems being connected to distribution system of customer power supply near user.Along with the relieving of Power policy, distributed Power supply displays as a kind of emerging power generation mode, and the generating set of this low capacity is provided about electricity power distribution network user Power, can become the useful supplement of centralized generating.It can reduce the loss of power when electric power transmits and be upgraded by distribution The expense brought.And for a user, relatively low expense, higher reliability, the preferable quality of power supply, higher energy profit It is that they introduce the interest place of distributed power source with the energy supply of rate and certain independence.Meanwhile, regenerative resource is used The distributed power generation of technology, such as wind-power electricity generation, solar energy power generating, hydroelectric generation, additionally provides goodish environmental effect. Centralized generating will dominate what supply of electric power was well recognized as, but, the anxiety of the energy in world wide, environmental protection problem prominent Go out, the going deep into of power market reform, occur and development in the urgent need to this new valuable power generation mode of distributed power source.

The aspects such as distributed power source accesses power distribution network will be to voltage pulsation, short circuit current, the trend flow direction bring unfavorable shadow Ring.In order to make power distribution network remain able to safely and steadily run after accessing distributed power source, need to consider distributed power source Maximum injection power problem.

Summary of the invention

The technical problem to be solved in the present invention is to provide in the power distribution network that a kind of method is simple, scientific and reasonable distributed Power supply maximum injection power determines method.

In order to solve above-mentioned technical problem, the present invention comprises the steps:

1) determine the accessed distribution line of distributed power source or the peak load of bus, and then determine the power of adverse current Constraint limit value S_inv；

2) the accessed distribution line of distributed power source or the voltage of bus and equivalent impedance parameter are obtained, in order to carry out electricity The calculating of pressure fluctuation constraints, and then determine voltage pulsation limit Δ U_lim；

3) determine that distributed power source accesses the short circuit current limit value under electric pressure, and distributed power source access before short Road levels of current, thus draw maximum short circuit current increment Delta I that distributed power source allows to cause_lim；

4) in distribution line or bus, input the injecting power S of a distributed power source₀；

5) checking injecting power S₀Whether meeting adverse current constraints, the condition of adverse current constraint is:

S_inv=k×L_max

S₀<S_inv

Wherein, S_invFor the power constraint limit value of adverse current, L_maxFor peak load, k can be according to situation value, S₀For distributed The injecting power of power supply,

If meeting adverse current constraints, then carry out next step checking, if being unsatisfactory for adverse current constraints, then output injection merit Rate S₀-Δ S, wherein, Δ S is injecting power variable quantity and S₀-Δ S is the maximum injection power of the distributed power source meeting condition；

6) checking injecting power S₀Whether meeting voltage pulsation constraints, the condition of voltage pulsation constraint is:

$\mathrm{\&Delta;U}=(R_s+{\mathrm{jX}}_s)\&CenterDot;({\mathrm{\&Delta;I}}_p+\mathrm{j\&Delta;}{I}_q)$

$=\left|Z_s\right|(\cos \mathrm{\&phi;}+j\sin \mathrm{\&phi;})\&CenterDot;\left|\mathrm{\&Delta;I}\right|(\cos \mathrm{\&theta;}+j\sin \mathrm{\&theta;})$

$=\frac{u^2}{S_k}\frac{{\mathrm{\&Delta;S}}_n}{U}\&CenterDot;[(\cos \mathrm{\&phi;}\cos \mathrm{\&theta;}-\sin \mathrm{\&phi;}\sin \mathrm{\&theta;})+j(\sin \mathrm{\&phi;}\cos \mathrm{\&theta;}+\cos \mathrm{\&phi;}\sin \mathrm{\&theta;})]$

ΔU<ΔU_lim

Wherein, the voltage change of access point, S when Δ U is generated energy fluctuation_kFor grid integration point capacity of short circuit, Δ S_nFor The changed power that distributed power source injects, θ is distributed power source power-factor angle, (R_s+jX_s) it is electrical network equiva lent impedance, U is for connecing Entering point voltage, φ is the electric network impedance angle entered from the point of view of accessing, Δ U_limFor voltage pulsation limit value,

If meeting voltage pulsation constraints, then carry out next step checking, if being unsatisfactory for voltage pulsation constraints, the most defeated Go out injecting power S₀-Δ S, wherein, Δ S is injecting power variable quantity and S₀-Δ S is the maximum of the distributed power source meeting condition Injecting power；

7) checking injecting power S₀Whether meeting short circuit current constraints, the condition of short circuit current constraint is:

ΔI_lim=I_thr-I₀

ΔI<ΔI_lim

Wherein, I₀Short circuit current level during for not accessing distributed power source in power distribution network, I_thrUnder same electric pressure Short-circuit current limit value, Δ I_limThe maximum short circuit current increment caused is allowed for distributed power source,

If meeting short circuit current constraints, then increase injecting power, i.e. increase on the basis of former injecting power and inject Power variation Δ S also backs within the above-mentioned 5th) step, the most progressively checking is until there is any one constraints not Meeting, the injecting power of output previous round, the injecting power the most now exported is the maximum injection power of distributed power source again； If being unsatisfactory for short circuit current constraints, then output injection power S₀-Δ S, wherein, Δ S is injecting power variable quantity and S₀-ΔS For meeting the maximum injection power of the distributed power source of condition.

During initialization, in distribution line or bus, input the initial injecting power S ' of a distributed power source, described Initial injecting power S ' meets described adverse current constraints, voltage pulsation constraints and short circuit current constraints, and initially During change, S₀=S′。

Use technique scheme, the invention has the beneficial effects as follows:

1, method is simple, scientific and reasonable；

2, on the premise of can requiring meeting technology, the maximum injection power of distributed power source is determined；

3, instruct and promote that distributed power source is grid-connected, it is thus achieved that considerable economic and social benefit.

Accompanying drawing explanation

Fig. 1 is the calculation flow chart that Distributed Generation in Distribution System maximum injection power of the present invention determines method；

Fig. 2 is the thevenin equivalent circuit on its access point of the system containing distributed power source.

Detailed description of the invention

The present invention is further detailed explanation with detailed description of the invention below in conjunction with the accompanying drawings:

Seeing Fig. 1 and Fig. 2, the Distributed Generation in Distribution System maximum injection power of the present invention determines method to include as follows to walk Rapid:

1) determine the accessed distribution line of distributed power source or the peak load of bus, and then determine the power of adverse current Constraint limit value S_inv；

2) the accessed distribution line of distributed power source or the voltage of bus and equivalent impedance parameter are obtained, in order to carry out electricity The calculating of pressure fluctuation constraints, and then determine voltage pulsation limit Δ U_lim；

3) determine that distributed power source accesses the short circuit current limit value under electric pressure, and distributed power source access before short Road levels of current, thus draw maximum short circuit current increment Delta I that distributed power source allows to cause_lim；

4) in distribution line or bus, input the injecting power S of a distributed power source₀；

5) checking injecting power S₀Whether meeting adverse current constraints, the condition of adverse current constraint is:

S_inv=k×L_max

S₀<S_inv

Wherein, S_invFor the power constraint limit value of adverse current, L_maxFor peak load, k can be according to situation value, S₀For distributed The injecting power of power supply,

If meeting adverse current constraints, then carry out next step checking, if being unsatisfactory for adverse current constraints, then output injection merit Rate S₀-Δ S, wherein, Δ S is injecting power variable quantity and S₀-Δ S is the maximum injection power of the distributed power source meeting condition；

6) checking injecting power S₀Whether meeting voltage pulsation constraints, the condition of voltage pulsation constraint is:

$\mathrm{\&Delta;U}=(R_s+{\mathrm{jX}}_s)\&CenterDot;({\mathrm{\&Delta;I}}_p+\mathrm{j\&Delta;}{I}_q)$

$=\left|Z_s\right|(\cos \mathrm{\&phi;}+j\sin \mathrm{\&phi;})\&CenterDot;\left|\mathrm{\&Delta;I}\right|(\cos \mathrm{\&theta;}+j\sin \mathrm{\&theta;})$

$=\frac{u^2}{S_k}\frac{{\mathrm{\&Delta;S}}_n}{U}\&CenterDot;[(\cos \mathrm{\&phi;}\cos \mathrm{\&theta;}-\sin \mathrm{\&phi;}\sin \mathrm{\&theta;})+j(\sin \mathrm{\&phi;}\cos \mathrm{\&theta;}+\cos \mathrm{\&phi;}\sin \mathrm{\&theta;})]$

ΔU<ΔU_lim

Wherein, the voltage change of access point, S when Δ U is generated energy fluctuation_kFor grid integration point capacity of short circuit, Δ S_nFor The changed power that distributed power source injects, θ is distributed power source power-factor angle, (R_s+jX_s) it is electrical network equiva lent impedance, U is for connecing Entering point voltage, φ is the electric network impedance angle entered from the point of view of accessing, Δ U_limFor voltage pulsation limit value,

If meeting voltage pulsation constraints, then carry out next step checking, if being unsatisfactory for voltage pulsation constraints, the most defeated Go out injecting power S₀-Δ S, wherein, Δ S is injecting power variable quantity and S₀-Δ S is the maximum of the distributed power source meeting condition Injecting power；

7) checking injecting power S₀Whether meeting short circuit current constraints, the condition of short circuit current constraint is:

ΔI_lim=I_thr-I₀

ΔI<ΔI_lim

Wherein, I₀Short circuit current level during for not accessing distributed power source in power distribution network, I_thrUnder same electric pressure Short-circuit current limit value, Δ I_limThe maximum short circuit current increment caused is allowed for distributed power source,

If meeting short circuit current constraints, then increase injecting power, i.e. increase on the basis of former injecting power and inject Power variation Δ S also backs within the above-mentioned 5th) step, the most progressively checking is until there is any one constraints not Meeting, the injecting power of output previous round, the injecting power the most now exported is the maximum injection power of distributed power source again； If being unsatisfactory for short circuit current constraints, then output injection power S₀-Δ S, wherein, Δ S is injecting power variable quantity and S₀-ΔS For meeting the maximum injection power of the distributed power source of condition.

During initialization, in distribution line or bus, input the initial injecting power S ' of a distributed power source, described Initial injecting power S ' meets described adverse current constraints, voltage pulsation constraints and short circuit current constraints, and initially During change, S₀=S′。

Below three constraintss are described further:

1. adverse current constraint

In power distribution network, distributed power source sends power and does not allows to pass through its access device upper electric pressure of injection.For Prevent adverse current from upper level electrical network is produced large effect, cause upper level electrical network needs to be made at aspects such as relay protection are arranged Adjusting on a large scale, quantity of electricity produced by distributed power source should be tried one's best this grade of distribution region inner equilibrium, is therefore distributed The EIAJ of formula power supply should be less than the peak load in the range of transformer-supplied under this electric pressure.

For 10kV access module on the spot, it is considered to this factor of load peak-valley difference, in order to make produced by distributed power source Electric power all can balance in this power supply area, needs to meet that to exert oneself as rated power and load at distributed power source be its paddy Still disclosure satisfy that the restriction occurring without adverse current during value, be necessary for so that the EIAJ accessing distributed power source is less than load Valley.According to statistics, type area's " load valley/load peak " this ratio is about 0.4-0.6.Therefore, distributed power source is total Capacity must not exceed the 40%-60% of middle pressure feeder line peak load, can ensure that the produced electric power of distributed power source is in this grating Electricity region inner equilibrium.If considering the uncertainty of load development, then it is considered as distributed power source total capacity less than middle pressure feeder line The 30% of peak load.

For access via telephone line pattern, national grid is pointed out in " distributed power source accesses electric power network technique regulation ": distributed Power supply total capacity is in principle no more than in upper level transformer-supplied region the 25% of peak load.Therefore, connect at analysis special line When entering problem, distributed power source capacity maximum is less than the 25% of transformator institute on-load.

The present worth of comprehensive case above adverse current constraint can be taken as:

S_inv=k×L_max (1)

Wherein, S_invRepresent the power constraint limit value of adverse current, L_maxRepresenting peak load, k can be according to situation value.

Countercurrently constraint requirements:

S₀<S_inv (2)

Wherein, S_invRepresent the power constraint limit value of adverse current, S₀Represent the injecting power of distributed power source.

2. voltage pulsation constraint

After distributed power source accesses electrical network, the voltage deviation of points of common connection should meet GB/T12325-2008 " electric energy matter Amount supply voltage deviation " regulation, it may be assumed that the absolute value sum of 35kV and the positive and negative deviation of above supply voltage less than nominal electricity The 10% of pressure.20kV and following three phase supply voltage deviation be nominal voltage ± 7%.

The impact of the voltage pulsation grid integration point that distributed power source causes is maximum, therefore, puts with this and assesses electricity Buckling, Fig. 2 is the thevenin equivalent circuit of grid integration point.

Current variation value Δ I when the power of distributed power source injected system changes, on circuit.When generated energy ripple Time dynamic, the voltage change of access point is Δ U.Estimated as follows by Fig. 2:

$\mathrm{\&Delta;U}=(R_s+{\mathrm{jX}}_s)\&CenterDot;({\mathrm{\&Delta;I}}_p+\mathrm{j\&Delta;}{I}_q)---\left(3\right)$

$=\left|Z_s\right|(\cos \mathrm{\&phi;}+j\sin \mathrm{\&phi;})\&CenterDot;\left|\mathrm{\&Delta;I}\right|(\cos \mathrm{\&theta;}+j\sin \mathrm{\&theta;})$

$=\frac{u^2}{S_k}\frac{{\mathrm{\&Delta;S}}_n}{U}\&CenterDot;[(\cos \mathrm{\&phi;}\cos \mathrm{\&theta;}-\sin \mathrm{\&phi;}\sin \mathrm{\&theta;})+j(\sin \mathrm{\&phi;}\cos \mathrm{\&theta;}+\cos \mathrm{\&phi;}\sin \mathrm{\&theta;})]$

In above formula, grid integration point capacity of short circuit is S_k, the changed power that distributed power source injects is Δ S_n, distributed Electrical source power factor angle θ, electrical network equiva lent impedance is (R_s+jX_s), access point voltage U, the electric network impedance angle entered from the point of view of accessing is φ。

Distributed power source site are connected to the voltage landing that infinitely great system causes:

$\mathrm{\&Delta;U}=\frac{\mathrm{PR}+\mathrm{QX}}{U_N}+j\frac{\mathrm{PX}-\mathrm{QR}}{U_N}---\left(4\right)$

In formula, P is the meritorious of injected system；Q is the idle of injected system；U_NFor system nominal voltage；R+jX is circuit Impedance.

When distributed power source uses power electronic equipment grid-connected, power network line is shorter, and both end voltage phase angle is more or less the same, The imaginary of negligible (4) formula, when injecting power changes, the expression formula of voltage pulsation of power component being differentiated to obtain For:

$d\left(\mathrm{\&Delta;U}\right)=\frac{d\left(P\right)R+d\left(Q\right)X}{U_N}---\left(5\right)$

Distribution network voltage the most relatively low grade containing distributed power source (≤35kV).Mesolow transmission line and high voltage transmission line Road parameter characteristic is different, and high voltage transmission line presents reactance characteristic, and the low and medium voltage distribution network that distributed power source is grid-connected, system presents Electrical resistance property, R > > X, therefore when analyzing, reactance is negligible, formula (5) can be reduced to:

$d\left(\mathrm{\&Delta;U}\right)\&ap;\frac{d\left(P\right)R}{U_N}---\left(6\right)$

As can be seen here, line resistance R and electrical network rated voltage U_NIn the case of constant, distributed power source uses power electronics The grid-connected voltage pulsation caused of device depends primarily on the fluctuation of active power.

The voltage pulsation Δ U value that can obtain distributed power source access point is calculated, with relevant voltage by above formula The voltage pulsation limit Δ U of grade_limCompare, it is possible to verify whether distributed power source injecting power meets voltage pulsation at that time Constraint.

3. short circuit current constraint

The distributed power source of Small And Medium Capacity accesses in power distribution network, will provide fault current to trouble point when fault occurs. Distributed power source can represent with the model of a power sources in series reactance.Therefore required it is considered that, when fault occurs Distributed power source can provide great fault current.For different types of distributed power source, its reactance value is different, it Represent the fault current injectability of this power supply.The fault current injectability of all kinds distributed power source is as shown in table 1.

The short circuit current injectability of the dissimilar distributed power source of table 1

It is found that using synchronous generator as the fault current injectability that the distributed power source of interface is maximum from table Can reach 1000%, this value can be used for short circuit calculation to determine the worst failure condition.

The maximum short circuit current increment that distributed power source access power distribution network causes can be according to the addition method in Circuit theory Calculate.Distributed power source can be processed into current source or voltage source according to its grid-connected interface.

When not accessing distributed power source in power distribution network, short circuit current level is I₀, short circuit current pole under this electric pressure Limit value is I_thr, then the distributed power source that accesses allows the maximum short circuit current increment caused to be:

ΔI_lim=I_thr-I₀ (7)

Short circuit current increment Delta I caused when the distributed power source access power distribution network of certain power meets Δ I < Δ I_limTime, I.e. think that injecting power now meets short circuit current constraint.

In sum, present disclosure is not limited in the above embodiments, and those skilled in the art can be Other embodiment proposed within technological guidance's thought of the present invention, but these embodiments be included in the scope of the present invention it In.

Claims (2)

1. Distributed Generation in Distribution System maximum injection power determines a method, and it comprises the steps:

1) determine the accessed distribution line of distributed power source or the peak load of bus, and then determine the power constraint of adverse current Limit value S_inv；

2) the accessed distribution line of distributed power source or the voltage of bus and equivalent impedance parameter are obtained, in order to carry out voltage wave The calculating of moving constraint condition, and then determine voltage pulsation limit Δ U_lim；

3) the short circuit current limit value under distributed power source access electric pressure, and the short circuit electricity before distributed power source access are determined Flow horizontal, thus draw maximum short circuit current increment Delta I that distributed power source allows to cause_lim；

4) in distribution line or bus, input the injecting power S of a distributed power source₀；

5) checking injecting power S₀Whether meeting adverse current constraints, the condition of adverse current constraint is:

S_inv=k × L_max

S₀<S_inv

Wherein, S_invFor the power constraint limit value of adverse current, L_maxFor peak load, k can be according to situation value, S₀For distributed power source Injecting power,

If meeting adverse current constraints, then carry out next step checking, if being unsatisfactory for adverse current constraints, then output injection power S₀- Δ S, wherein, Δ S is injecting power variable quantity and S₀-Δ S is the maximum injection power of the distributed power source meeting condition；

6) checking injecting power S₀Whether meeting voltage pulsation constraints, the condition of voltage pulsation constraint is:

$\begin{array}{c}\mathrm{\&Delta;}U=(R_s+{\mathrm{jX}}_s)\&CenterDot;({\mathrm{\&Delta;I}}_p+{\mathrm{j\&Delta;I}}_q)\\ =\left|Z_s\right|(\cos \mathrm{\&phi;}+j\sin \mathrm{\&phi;})\&CenterDot;\left|\mathrm{\&Delta;}I\right|(\cos \mathrm{\&theta;}+j\sin \mathrm{\&theta;})\\ =\frac{U^2}{S_k}\frac{{\mathrm{\&Delta;S}}_n}{U}\&CenterDot;\&lsqb;(\cos \mathrm{\&phi;}\cos \mathrm{\&theta;}-\sin \mathrm{\&phi;}\sin \mathrm{\&theta;})+j(\sin \mathrm{\&phi;}\cos \mathrm{\&theta;}+\cos \mathrm{\&phi;}\sin \mathrm{\&theta;})\&rsqb;\end{array}$

$=\frac{U\&CenterDot;{\mathrm{\&Delta;S}}_n}{S_k}\&CenterDot;\&lsqb;(\cos \mathrm{\&phi;}\cos \mathrm{\&theta;}-\sin \mathrm{\&phi;}\sin \mathrm{\&theta;})+j(\sin \mathrm{\&phi;}\cos \mathrm{\&theta;}+\cos \mathrm{\&phi;}\sin \mathrm{\&theta;})\&rsqb;$

ΔU<ΔU_lim

Wherein, the voltage change of access point, S when Δ U is generated energy fluctuation_kFor grid integration point capacity of short circuit, Δ S_nFor distribution The changed power that formula power supply injects, θ is distributed power source power-factor angle, R_s+jX_sFor electrical network equiva lent impedance, U is access point electricity Pressure, φ is the electric network impedance angle entered from the point of view of accessing, Δ U_limFor voltage pulsation limit value, Δ I is that distributed power source accesses power distribution network The short circuit current increment caused,

If meeting voltage pulsation constraints, then carrying out next step checking, if being unsatisfactory for voltage pulsation constraints, then exporting note Enter power S₀-Δ S, wherein, Δ S is injecting power variable quantity and S₀-Δ S is the maximum injection of the distributed power source meeting condition Power；

7) checking injecting power S₀Whether meeting short circuit current constraints, the condition of short circuit current constraint is:

ΔI_lim=I_thr-I₀

ΔI<ΔI_lim

Wherein, I₀Short circuit current level during for not accessing distributed power source in power distribution network, I_thrShort circuit under same electric pressure Current limit value, Δ I_limThe maximum short circuit current increment caused is allowed for distributed power source,

If meeting short circuit current constraints, then increase injecting power, on the basis of former injecting power, i.e. increase injecting power Variation delta S also backs within the above-mentioned 5th) step, the most progressively checking is until occurring that any one constraints is the fullest Foot, the injecting power of output previous round, the injecting power the most now exported is the maximum injection power of distributed power source；If no Meet short circuit current constraints, then output injection power S₀-Δ S, wherein, Δ S is injecting power variable quantity and S₀-Δ S is full The maximum injection power of the distributed power source of foot condition.

2. determine method according to the Distributed Generation in Distribution System maximum injection power described in claim 1, it is characterised in that: just During beginningization, in distribution line or bus, input the initial injecting power S ' of a distributed power source, described initial injection merit Rate S ' meets described adverse current constraints, voltage pulsation constraints and short circuit current constraints, and when initializing, S₀= S′。