CN103595040A - Power distribution network comprising direct-current distributed power supply and analysis method of comprehensive load characteristics of power distribution network - Google Patents

Abstract

The invention relates to a power distribution network comprising a direct-current distributed power supply and an analysis method of comprehensive load characteristics of the power distribution network. The power distribution network comprises static loads, a dynamic load bus and comprehensive loads, wherein the static loads are equivalent static loads formed by combining static load elements and the direct-current distributed power supply, a model structure of the comprehensive loads is a generalized comprehensive load model structure and comprises a reactive compensation device, static loads, induction motor loads, an equivalent power supply, a power distribution network equivalent impedor, the reactive compensation device, the static loads, the equivalent power supply and an induction motor are connected in parallel and are connected to an external system through the power distribution network equivalent impedor. The model structure of the comprehensive loads adopted in the power distribution network can integrally describe various load characteristics of nodes, and the problem that after a large number of distributed power generation devices are connected to the power distribution network, the power distribution network affects the comprehensive load characteristics is solved.

Description

Containing the power distribution network of direct current distributed power source and the analytical method of synthetic load characteristic thereof

Technical field

The present invention relates to power distribution network technical field, be specifically related to a kind of containing the power distribution network of direct current distributed power source and the analytical method of synthetic load characteristic thereof.

Background technology

The large multiple access 10kV of distributed power generation equipment and following power distribution network side (except the centralized access major network such as Large Scale Wind Farm Integration), physical location is widely distributed, operation characteristic is different, capacity ratio progressively increases, thereby on power supply and Electric Power Network Planning, traffic control and the control of the modern power systems of contact all will produce very important impact with it.In the electric system simulation of the basic decision foundation as Study on Power Grid Planning and traffic control control calculates, load model is that the equivalence of major network substation bus bar (the normally 110kV bus of 220kV transformer station) " synthetic load " characteristic is described.This synthetic load composition, except the dynamic load and static load that comprise in general sense, has also comprised distribution network and distributed power source naturally.In service in actual electric network, that dynamic load or static load all can not be directly by 110kV or 220kV bussed supplies, all need to power by distribution elements such as circuit and transformers, therefore distribution network will certainly affect to synthetic load characteristic, simultaneously, after a large amount of distributed power generation equipment access power distribution networks, will inevitably make these impacts further expand.Existing load model has:

Static load model: static load model represents the model of the functional relation of meritorious and reactive power and synchronization lower node voltage magnitude and frequency.In tidal current analysis, static stability analysis and the research long-term dynamics process of electric power system, and load take static load in main situation, generally adopts static load model.

Dynamic load model: when voltage is during with speed wide variation faster, should consider the dynamic characteristic of load, and with differential equation, be referred to as dynamic model.That is to say for example, characteristic when dynamic characteristic is voltage and frequency quick-speed large-scale variation (voltage is lower than motor critical voltage value).

Integrated load model: as shown in Figure 1, this integrated load model structure is induction motor and constant-impedance to classical integrated load model, is referred to as classical integrated load model (classical synthesis load model, CSLM) model.This model relatively simple for structure, parameter identification is relatively easy, and can be good at describing the dynamic characteristic of load, explicit physical meaning, the ratio of motor and ZIP load has characterized the ratio of dynamic load and static load in system.

But the static part of CSLM model is not considered the impact of distribution system impedance, in equivalent load model, equivalent motor and static load all should be considered the equivalent impedance of distribution system, the nonlinear impact of being loaded, adopts existing mathematical method static load equivalence from power distribution network cannot be shifted out; And the motor stator reactance of this model is while taking into account distribution system impedance, do not consider the reactive power compensation of distribution system and the impact of static load, in this model, distribution system equivalent impedance is directly merged with the stator impedance of equivalent motor, this processing mode, under the condition of not considering distribution network reactive power compensation and static load, be feasible, but, owing to not considering the reactive power compensation of distribution system, by causing the pressure drop of distribution system equivalent impedance to increase, worsen the service conditions of motor.

Summary of the invention

The object of this invention is to provide a kind of containing the power distribution network of direct current distributed power source and the analytical method of synthetic load characteristic thereof, the integrated load model adopting in this power distribution network is except having considered equivalent induction-motor load and static load, outside equivalent impedance between transmission and distribution network and distribution network var compensation device, also considered the equivalent power supply under this node, can more completely simulate load and distribution system, the various part throttle characteristics of description node intactly, in order to solve after a large amount of distributed power generation equipment access power distribution networks, distribution network impacts synthetic load characteristic and existing CSLM model can worsen the problem of motor service conditions.

For achieving the above object, the solution of the present invention is: a kind of power distribution network containing direct current distributed power source, this power distribution network comprises static load bus, dynamic load bus and synthetic load bus, between described static load bus and dynamic load bus and and synthetic load bus and dynamic load bus between be serially connected with impedance, described static load bus connects static load, described dynamic load bus connects dynamic load, one side of described synthetic load bus connects synthetic load, the opposite side of described comprehensive bus connects external system by isolating transformer, described static load bus is also connected with direct current distributed power source, described static load afterwards synthetic Equivalent Static load in parallel with direct current distributed power source, the model structure of described synthetic load is a broad sense integrated load model structure, comprise reactive-load compensation equipment, static load, induction motor load, equivalent power supply and power distribution network equivalent impedance, described reactive-load compensation equipment, static load, equivalent power supply and induction motor are connected in a side of synthetic load bus in parallel, one end of described power distribution network equivalent impedance is connected to the opposite side of synthetic load bus, the other end of described power distribution network equivalent impedance accesses external system by isolating transformer.

The load model that described static load adopts is ZIP model or power function model, and the load model that described dynamic load adopts is the induction motor model of three-phase symmetrical, single rotor winding.

Described ZIP model is:

$\left\{\begin{array}{c}P=P_0[A_p{(U/U_0)}^2+B_p(U/U_0)+C_p]\\ Q=Q_0[A_q{(U/U_0)}^2+B_q(U/U_0)+C_q]\end{array}\right.$

Wherein, P is active power; Q is reactive power; P ₀, Q ₀, U ₀for initial or specified runtime value; A _p, B _p, C _pfor active voltage characterisitic parameter; A _q, B _q, C _qfor reactive voltage characterisitic parameter; And meet A _q+ B _q+ C _q=1; A _p+ B _p+ C _p=1.

Described power function model is:

$\left\{\begin{array}{c}P=P_0{(U/U_0)}^{P_u}{(f^{\′}/{f^{\′}}_0)}^{P_f}\\ Q=Q_0{(U/U_0)}^{Q_u}{(f^{\′}/{f^{\′}}_0)}^{Q_f}\end{array}\right.$

Wherein, P, Q, U, f' are respectively the actual motion value of active power, reactive power, voltage and load bus frequency, P ₀, Q ₀, U ₀, f' ₀be respectively the specified runtime value of active power, reactive power, voltage and load bus frequency; P _ufor active voltage characteristic coefficient; P _ffor meritorious frequency characteristic coefficient; Q _ufor reactive voltage characteristic coefficient; Q _ffor meritorious frequency characteristic coefficient.

The present invention also provides a kind of analytical method of above-mentioned power distribution network synthesis part throttle characteristics, and the method comprises the steps:

(1) set up the model structure of synthetic load in power distribution network, the model structure of the synthetic load in described power distribution network is a broad sense integrated load model structure, comprise reactive-load compensation equipment, static load, induction motor load and power distribution network equivalent impedance, described reactive-load compensation equipment, static load and induction motor are connected in a side of synthetic load bus in parallel, one end of described power distribution network equivalent impedance is connected to the opposite side of synthetic load bus, and the other end of described power distribution network equivalent impedance accesses external system by isolating transformer;

(2), according to synthetic load step (1) Suo Shu, the shared ratio of dynamic load in this synthetic load that can obtain is:

${K_m}^{\′\′}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{sys}}}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{IM}}+P_{\mathrm{seq}}}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{IM}}+(P_S-P_{\mathrm{DG}})}$

Wherein, Km " be the shared ratio of dynamic load in synthetic load, P _iMfor induction motor load power, P _sfor static load power, P _dGfor exerting oneself of direct current distributed power source, Psys is that external system is supplied with load, and Pseq is Equivalent Static load power;

(3) from step (2): when 0 < Km ' ' < 1, P _dG< P _s, show that the undercapacity of direct current distributed power source is to supply with static load;

When Km ' '>=1, P _s≤ P _dG< P _s+ P _iM, show that exerting oneself of direct current distributed power source is enough to supply with static load, but be not enough to supply with total load;

When Km ' '≤0, P _dG>=P _s+ P _iM, show that exerting oneself of direct current distributed power source is enough to supply with total load.

The load model that described static load adopts is ZIP model or power function model, and the load model that described dynamic load adopts is the induction motor model of three-phase symmetrical, single rotor winding.

Described ZIP model is:

$\left\{\begin{array}{c}P=P_0[A_p{(U/U_0)}^2+B_p(U/U_0)+C_p]\\ Q=Q_0[A_q{(U/U_0)}^2+B_q(U/U_0)+C_q]\end{array}\right.$

Wherein, P is active power; Q is reactive power; P ₀, Q ₀, U ₀for initial or specified runtime value; A _p, B _p, C _pfor active voltage characterisitic parameter; A _q, B _q, C _qfor reactive voltage characterisitic parameter; And meet A _q+ B _q+ C _q=1; A _p+ B _p+ C _p=1.

Described power function model is:

$\left\{\begin{array}{c}P=P_0{(U/U_0)}^{P_u}{(f^{\&prime;}/{f^{\&prime;}}_0)}^{P_f}\\ Q=Q_0{(U/U_0)}^{Q_u}{(f^{\&prime;}/{f^{\&prime;}}_0)}^{Q_f}\end{array}\right.$

Wherein, P, Q, U, f' are respectively the actual motion value of active power, reactive power, voltage and load bus frequency, P ₀, Q ₀, U ₀, f' ₀be respectively the specified runtime value of active power, reactive power, voltage and load bus frequency; P _ufor active voltage characteristic coefficient; P _ffor meritorious frequency characteristic coefficient; Q _ufor reactive voltage characteristic coefficient; Q _ffor meritorious frequency characteristic coefficient.

The beneficial effect that the present invention reaches: the integrated load model that adopts broad sense in power distribution network of the present invention, this integrated load model has been considered distribution network and reactive power compensation, overcome the deficiency of the integrated load model of existing classics, can more completely simulate load and distribution system; This load model is relatively simple for structure, compare with classical integrated load model, broad sense integrated load model descriptive power is the most comprehensive, the various part throttle characteristics of description node intactly, more meticulous, more symmetrical with meticulous electric system simulation calculation requirement, make the accurate model of other element can bring into play due effect, make electric system simulation result of calculation more accurately with reliable.

Accompanying drawing explanation

Fig. 1 is the structure principle chart of existing CSLM model;

Fig. 2 is distribution net work structure figure of the present invention;

Fig. 3 is the structure principle chart of broad sense integrated load model of the present invention;

Fig. 4 is the model structure block diagram that the present invention describes synthetic load characteristic.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further detailed explanation.

Power distribution network embodiment of the present invention:

As Fig. 2, power distribution network of the present invention comprises static load bus B2, dynamic load bus B3 and synthetic load bus B1, between described static load bus and dynamic load bus and and synthetic load bus and dynamic load bus between be serially connected with impedance, described static load bus connects static load, described dynamic load bus connects dynamic load, one side of described synthetic load bus connects synthetic load, the opposite side of described comprehensive bus connects external system by isolating transformer, described static load bus is also connected with direct current distributed power source, described static load afterwards synthetic Equivalent Static load in parallel with direct current distributed power source, the model structure of described synthetic load is a broad sense integrated load model structure, comprise reactive-load compensation equipment, static load, induction motor load, equivalent power supply and power distribution network equivalent impedance, described reactive-load compensation equipment, static load, equivalent power supply and induction motor are connected in a side of synthetic load bus in parallel, one end of described power distribution network equivalent impedance is connected to the opposite side of synthetic load bus, the other end of described power distribution network equivalent impedance accesses external system by isolating transformer.

In the present embodiment, the load model that static load adopts is ZIP model or power function model, and the load model that described dynamic load adopts is the induction motor model of three-phase symmetrical, single rotor winding, and described synthetic load adopts broad sense integrated load model.

Firm power, constant impedance and constant current ZIP model that static load adopts are:

$\left\{\begin{array}{c}P=P_0[A_p{(U/U_0)}^2+B_p(U/U_0)+C_p]\\ Q=Q_0[A_q{(U/U_0)}^2+B_q(U/U_0)+C_q]\end{array}\right.$

Wherein, P is active power; Q is reactive power; P ₀, Q ₀, U ₀for initial or specified runtime value; A _p, B _p, C _pfor active voltage characterisitic parameter; A _q, B _q, C _qfor reactive voltage characterisitic parameter; And meet A _q+ B _q+ C _q=1; A _p+ B _p+ C _p=1.

Described power function model is:

$\left\{\begin{array}{c}P=P_0{(U/U_0)}^{P_u}{(f^{\&prime;}/{f^{\&prime;}}_0)}^{P_f}\\ Q=Q_0{(U/U_0)}^{Q_u}{(f^{\&prime;}/{f^{\&prime;}}_0)}^{Q_f}\end{array}\right.$

Wherein, P, Q, U, f' are respectively the actual motion value of active power, reactive power, voltage and load bus frequency, P ₀, Q ₀, U ₀, f ₀be respectively the specified runtime value of active power, reactive power, voltage and load bus frequency; P _ufor active voltage characteristic coefficient; P _ffor meritorious frequency characteristic coefficient; Q _ufor reactive voltage characteristic coefficient; Q _ffor meritorious frequency characteristic coefficient.

As Fig. 3, the model structure of the synthetic load of the present embodiment is a broad sense integrated load model structure, comprise reactive-load compensation equipment, static load, induction motor load, equivalent power supply and power distribution network equivalent impedance, reactive-load compensation equipment, static load, equivalent power supply and induction motor are connected in a side of synthetic load bus in parallel, one end of power distribution network equivalent impedance is connected to the opposite side of synthetic load bus, and the other end of power distribution network equivalent impedance accesses external system by isolating transformer.

Typical direct current distributed power source-photovoltaic (PV) is controlled by MPPT, DC/DC and DC/AC conversion, after increasing battery module, can be equivalent to the voltage source of constant power output in the process of steady operation simultaneously; And in the load modeling research towards power system transient simulation, based on the constant hypothesis of transient process weather conditions, PV can regard a power consumption as for negative equivalent broad sense static load, when its part as broad sense synthetic load, can carry out equivalent description with the static load model of permanent power.

Direct current distributed generation system, no matter in steady operation or transient process, all can be realized the plan load external characteristic of constant power source.According to this plan load external characteristic of direct current distributed power source, when the power distribution network synthesis load modeling of direct current distributed power source is considered in research, direct current distributed power source can be regarded as to a power consumption is negative broad sense static load, when its part as power distribution network synthesis load, can carry out equivalent description with the broad sense static load model of permanent power.

The present invention adopts the load model structure of broad sense synthetic load of induction motor in parallel of Equivalent Static as shown in Figure 4 to describe the power distribution network synthesis part throttle characteristics containing direct current distributed power source.In Fig. 4, P _iM, P _s, P _dGrepresent that respectively induction motor load power, static load power, direct current distributed power generation exert oneself; Direct current distributed power source is exerted oneself and synthesized Equivalent Static load, Equivalent Static load power P with static load _seqrepresent; External system is supplied with load for P _sys.Above-mentioned each power reference direction definition as shown in Figure 4, has only marked active power reference direction in figure, reactive power is similar.

The inventive method embodiment:

Method step of the present invention is as follows:

(1) set up the model structure of synthetic load in power distribution network, the model structure of the synthetic load in described power distribution network is a broad sense integrated load model structure, comprise reactive-load compensation equipment, static load, induction motor load and power distribution network equivalent impedance, described reactive-load compensation equipment, static load and induction motor are connected in a side of synthetic load bus in parallel, one end of described power distribution network equivalent impedance is connected to the opposite side of synthetic load bus, and the other end of described power distribution network equivalent impedance accesses external system by isolating transformer;

(2), according to synthetic load step (1) Suo Shu, the shared ratio of dynamic load in this synthetic load that can obtain is:

${K_m}^{\&prime;\&prime;}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{sys}}}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{IM}}+P_{\mathrm{seq}}}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{IM}}+(P_S-P_{\mathrm{DG}})}$

Wherein, K _m" be the shared ratio of dynamic load in synthetic load, P _iMfor induction motor load power, P _sfor static load power, P _dGfor exerting oneself of direct current distributed power source, Psys is that external system is supplied with load, and Pseq is Equivalent Static load power;

(3) from step (2): when 0 < Km ' ' < 1, P _dG< P _s, show that the undercapacity of direct current distributed power source is to supply with static load;

When Km ' '>=1, P _s≤ P _dG< P _s+ P _iM, show that exerting oneself of direct current distributed power source is enough to supply with static load but is not enough to supply with total load;

When Km ' '≤0, P _dG>=P _s+ P _iM, show that exerting oneself of direct current distributed power source is enough to supply with total load.

The load model that the static load of the present embodiment adopts is ZIP model or power function model, and the load model that dynamic load adopts is the induction motor model of three-phase symmetrical, single rotor winding.The scope of Km ' ' will restriction when load model is carried out to parameter identification, and in traditional discrimination method, the circumscription of Km ' ' is 0 < Km ' ' < 1.

As Fig. 4, because the access meeting of direct current distributed power source directly affects the shared ratio of static load in power distribution network synthesis load, thereby affect synthetic load characteristic, with reference to the habitual definition mode of traditional integrated load model, sound ratio in the broad sense integrated load model of definition consideration direct current distributed power source, that is:

${K_m}^{\&prime;\&prime;}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{sys}}}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{IM}}+P_{\mathrm{seq}}}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{IM}}+(P_S-P_{\mathrm{DG}})}$

Wherein, K _m" be the shared ratio of dynamic load in integrated load model, P _iMfor induction motor load power, P _sfor static load power, P _dGfor exerting oneself of direct current distributed power source, Psys is that external system is supplied with load, and Pseq is Equivalent Static load power.

1) when 0 < Km ' ' < 1, Pseq > 0 and Psys > 0, now P _dG< PS, shows that the undercapacity of direct current distributed power source is to supply with static load;

2) when Km ' ' >=1, Pseq≤0 and Psys > 0, now PS≤PDG < PS+PIM, shows that exerting oneself of direct current distributed power source is enough to supply with static load but is not enough to supply with total load;

3) when Km ' '≤0, Pseq < 0 and Psys≤0, now P _dG>=P _s+ P _iM, show that exerting oneself of direct current distributed power source is enough to supply with total load.

Conventionally under operation conditions, PV and FC generally access power distribution network as the distributed power source of low capacity, therefore above-mentioned first two operational mode is the most general, for these two kinds of operational modes, when direct current distributed power source is exerted oneself while increasing gradually, Equivalent Static load progressively reduces, and the sound ratio of broad sense integrated load model (dynamic load proportion) increases progressively.

The present embodiment employing distribution network is as shown in Figure 2 as simulation example, and system equivalent and load value mark in the drawings, and B1 bus is as synthetic load bus.Based on MATLAB/SIMULINK, build the as above analogue system of figure, at B2 bus access PV direct current distributed power source, suppose Infinite bus system break down (duration 0.2s), lower voltage 20% left and right, carry out power system transient simulation, can obtain the dynamic Characteristic Data that system side under disturbance is transferred to active power, reactive power and the voltage of distribution side load bus, using this as the needed measured data of power distribution network synthesis load modeling parameter identification of distinguishing method based on total body examination.According to the equivalent parameters of these data identification load models, and then the dynamic response of calculating integrated load model, compare analysis with the data of original measurement.

Integrated load model in the present embodiment is identical with above-mentioned integrated load model embodiment, does not repeat them here.

The integrated load model that power distribution network of the present invention adopts is except having considered equivalent induction-motor load and static load, outside equivalent impedance between transmission and distribution network and distribution network var compensation device, also considered the equivalent power supply under this node, can more completely simulate load and distribution system, the various part throttle characteristics of description node intactly, in order to solve after a large amount of distributed power generation equipment access power distribution networks, distribution network impacts synthetic load characteristic and existing CSLM model can worsen the problem of motor service conditions.

Claims (8)

1. the power distribution network containing direct current distributed power source, this power distribution network comprises static load bus, dynamic load bus and synthetic load bus, between described static load bus and dynamic load bus and and synthetic load bus and dynamic load bus between be serially connected with impedance, described static load bus connects static load, described dynamic load bus connects dynamic load, one side of described synthetic load bus connects synthetic load, the opposite side of described comprehensive bus connects external system by isolating transformer, it is characterized in that:

Described static load bus is also connected with direct current distributed power source, described static load afterwards synthetic Equivalent Static load in parallel with direct current distributed power source, the model structure of described synthetic load is a broad sense integrated load model structure, comprise reactive-load compensation equipment, static load, induction motor load, equivalent power supply and power distribution network equivalent impedance, described reactive-load compensation equipment, static load, equivalent power supply and induction motor are connected in a side of synthetic load bus in parallel, one end of described power distribution network equivalent impedance is connected to the opposite side of synthetic load bus, the other end of described power distribution network equivalent impedance accesses external system by isolating transformer.

2. power distribution network according to claim 1, is characterized in that the load model that described static load adopts is ZIP model or power function model, and the load model that described dynamic load adopts is the induction motor model of three-phase symmetrical, single rotor winding.

3. power distribution network according to claim 2, is characterized in that described ZIP model is:

$\left\{\begin{array}{c}P=P_0[A_p{(U/U_0)}^2+B_p(U/U_0)+C_p]\\ Q=Q_0[A_q{(U/U_0)}^2+B_q(U/U_0)+C_q]\end{array}\right.$

Wherein, P is active power; Q is reactive power; P ₀, Q ₀, U ₀for initial or specified runtime value; A _p, B _p, C _pfor active voltage characterisitic parameter; A _q, B _q, C _qfor reactive voltage characterisitic parameter; And meet A _q+ B _q+ C _q=1; A _p+ B _p+ C _p=1.

4. power distribution network according to claim 2, is characterized in that described power function model is:

$\left\{\begin{array}{c}P=P_0{(U/U_0)}^{P_u}{(f^{\&prime;}/{f^{\&prime;}}_0)}^{P_f}\\ Q=Q_0{(U/U_0)}^{Q_u}{(f^{\&prime;}/{f^{\&prime;}}_0)}^{Q_f}\end{array}\right.$

Wherein, P, Q, U, f' are respectively the actual motion value of active power, reactive power, voltage and load bus frequency, P ₀, Q ₀, U ₀, f' ₀be respectively the specified runtime value of active power, reactive power, voltage and load bus frequency; P _ufor active voltage characteristic coefficient; P _ffor meritorious frequency characteristic coefficient; Q _ufor reactive voltage characteristic coefficient; Q _ffor meritorious frequency characteristic coefficient.

5. an analytical method for power distribution network synthesis part throttle characteristics as claimed in claim 1, is characterized in that: the method comprises the steps:

(1) set up the model structure of synthetic load in power distribution network, the model structure of the synthetic load in described power distribution network is a broad sense integrated load model structure, comprise reactive-load compensation equipment, static load, induction motor load, equivalent power supply and power distribution network equivalent impedance, described reactive-load compensation equipment, static load, equivalent power supply and induction motor are connected in a side of synthetic load bus in parallel, one end of described power distribution network equivalent impedance is connected to the opposite side of synthetic load bus, the other end of described power distribution network equivalent impedance accesses external system by isolating transformer,

(2), according to the model structure of synthetic load step (1) Suo Shu, the shared ratio of dynamic load in this synthetic load that can obtain is:

${K_m}^{\&prime;\&prime;}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{sys}}}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{IM}}+P_{\mathrm{seq}}}=\frac{P_{\mathrm{IM}}}{P_{\mathrm{IM}}+(P_S-P_{\mathrm{DG}})}$

Wherein, Km ' ' is the shared ratio of dynamic load in synthetic load, P _iMfor induction motor load power, P _sfor static load power, P _dGfor exerting oneself of direct current distributed power source, Psys is that external system is supplied with load, and Pseq is Equivalent Static load power;

(3) from step (2): when 0 < Km ' ' < 1, P _dG< P _s, show that the undercapacity of direct current distributed power source is to supply with static load;

When Km ' '>=1, P _s≤ P _dG< P _s+ P _iM, show that exerting oneself of direct current distributed power source is enough to supply with static load, but be not enough to supply with total load;

When Km ' '≤0, P _dG>=P _s+ P _iM, show that exerting oneself of direct current distributed power source is enough to supply with total load.

6. method according to claim 5, is characterized in that the load model that described static load adopts is ZIP model or power function model, and the load model that described dynamic load adopts is the induction motor model of three-phase symmetrical, single rotor winding.

7. method according to claim 6, is characterized in that described ZIP model is:

$\left\{\begin{array}{c}P=P_0[A_p{(U/U_0)}^2+B_p(U/U_0)+C_p]\\ Q=Q_0[A_q{(U/U_0)}^2+B_q(U/U_0)+C_q]\end{array}\right.$

Wherein, P is active power; Q is reactive power; P ₀, Q ₀, U ₀for initial or specified runtime value; A _p, B _p, C _pfor active voltage characterisitic parameter; A _q, B _q, C _qfor reactive voltage characterisitic parameter; And meet A _q+ B _q+ C _q=1; A _p+ B _p+ C _p=1.

8. method according to claim 6, is characterized in that described power function model is:

$\left\{\begin{array}{c}P=P_0{(U/U_0)}^{P_u}{(f^{\&prime;}/{f^{\&prime;}}_0)}^{P_f}\\ Q=Q_0{(U/U_0)}^{Q_u}{(f^{\&prime;}/{f^{\&prime;}}_0)}^{Q_f}\end{array}\right.$

Wherein, P, Q, U, f' are respectively the actual motion value of active power, reactive power, voltage and load bus frequency, P ₀, Q ₀, U ₀, f' ₀be respectively the specified runtime value of active power, reactive power, voltage and load bus frequency; P _ufor active voltage characteristic coefficient; P _ffor meritorious frequency characteristic coefficient; Q _ufor reactive voltage characteristic coefficient; Q _ffor meritorious frequency characteristic coefficient.

Images