CN105305392A - Symmetrical component method for short circuit calculation of voltage-controlled type IIDG included power distribution network - Google Patents

Abstract

The invention discloses a symmetrical component method for short circuit calculation of the voltage-controlled type IIDG included power distribution network. The method comprises the following steps that when the power distribution network has an asymmetric fault, the relation between the three-phase average power of the voltage-controlled type IIDG and the power of positive and negative sequence network is analyzed; a short circuit calculation sequence component model considering symmetrical control for the voltage type IIDG is established; change rule of fault current of the voltage type IIDG is obtained by combining interaction between the voltage type IIDG and the positive and negative sequence network of the power distribution network; and a symmetrical component iteration algorithm for calculating the short circuit current of the voltage-controlled type IIDG included power distribution network is provided, and the short circuit current of the voltage-controlled type IIDG included power distribution network is calculated. According to the method, sequence component method is used for short circuit calculation, the complexity and solution scale of the phase component method can be effectively reduced, and calculation of IIDG short circuit current sequence component can be applied to protection of the power distribution network and control for the power distribution network under asymmetric fault.

Description

Be applicable to the short circuit calculation symmetrical component method containing voltage control type IIDG power distribution network

Technical field

The present invention relates to distributed generation system technical field, particularly relate to a kind of short circuit calculation symmetrical component method be applicable to containing voltage-type IIDG power distribution network.

Background technology

The access of distributed power generation will change electric network swim and short circuit current distribution, wherein inverse distributed power (InverterInterfacedDistributedGenerator, IIDG) with the control performance of fast and flexible, extensive use in power distribution network and micro-capacitance sensor distributed power generation.Take over seamlessly to realize grid-connected and island mode, in micro-capacitance sensor, IIDG adopts droop control, constant voltage constant frequency to control usually.And for accessing the IIDG that is incorporated into the power networks of power distribution network, then mainly adopt power limitation control, follow the tracks of the difference of electricity by IIDG inner ring, its controller can be divided into voltage-controlled type and current-control type (being called for short voltage-type or current mode).Compared with synchronous generator, IIDG has different fault signatures, and particularly for voltage-type IIDG, it will occur typical time transient state and transient process after power distribution network short circuit.IIDG accesses the basis that the accident analysis of power distribution network is planning and designing, protection seting and stable operation; but adopt the equivalent voltage source method of the standards such as IEC60909 to calculate; because the control characteristic short circuit calculation resultant error not taking into account IIDG is comparatively large, therefore need to study the distribution network failure electric current Analytic Calculation Method containing IIDG.

During power distribution network short circuit, the reciprocation of IIDG and network determines that its short circuit current responds, and time-domain-simulation, physical analogy are the common methods of research IIDG fault characteristic, but are difficult to obtain analytic solutions.There is the addition method researched and proposed and calculate containing DG distribution network failure, but do not consider the dynamic process that IIDG controls.Also have research to think and the exponentially rule change of current mode IIDG short circuit current only calculate its dynamic response according to IIDG steady-state current before and after distribution network failure, can not accurate analysis short circuit current transient process and determine out-of-limit moment of short circuit current.There is document to control the change of power output in transfer function and fault for voltage-type IIDG, set up the phase component model calculating its each phase short circuit current size.Owing to not considering the phase place change of IIDG phase current, the short circuit current order components of voltage-type IIDG when cannot calculate power distribution network unbalanced fault.

Adopt phase component method to carry out short circuit calculation can effectively reduce the complexity of phase components method and solve scale, and the calculating of IIDG short circuit current order components can be used for distribution protection and the control under power distribution network unbalanced fault thereof.Therefore, set up the order components analytic modell analytical model of voltage-type IIDG short circuit calculation, be more conducive to the combination of IIDG control mode and distribution network failure analytical method.

Summary of the invention

For above shortcomings in prior art, the invention provides a kind of short circuit calculation symmetrical component method be applicable to containing voltage control type IIDG power distribution network, the method adopts phase component method to carry out short circuit calculation, can effectively reduce the complexity of phase components method and solve scale; Method provided by the invention can join in the calculation of short-circuit current of conventional electrical distribution net, also can take into account the current limliting constraint of IIDG simultaneously.

In order to solve the problems of the technologies described above, present invention employs following technical scheme:

When first analyzing power distribution network unbalanced fault, voltage-type IIDG three-phase average power and positive-negative sequence net power relation; Set up the short circuit calculation order components model taken into account voltage-type IIDG symmetry and control; In conjunction with the reciprocation of voltage-type IIDG and power distribution network positive-negative sequence network, obtain fault current Changing Pattern and the recurrence formula of voltage-type IIDG; Propose the symmetrical component iterative algorithm of the power distribution network short circuit current calculated containing voltage-type IIDG, calculate the short circuit current of the power distribution network containing voltage-type IIDG.

When analyzing power distribution network unbalanced fault, voltage-type IIDG three-phase average power and positive-negative sequence net power relation, concrete steps are as follows:

Voltage-type IIDG three-phase instantaneous power is by its terminal voltage vector u _g=[u _ga, u _gb, u _gc] and current phasor i _g=[i _ga, i _gb, i _gc] determine, three phases active power p _g=u _gi _g, three phase reactive power q _g=| u _g× i _g|; When power distribution network unbalanced fault, voltage-type IIDG terminal voltage u _gand current i _gall comprise positive-negative sequence component, i.e. u _g=u _g ¹+ u _g ², three phases active power is the half-period average value of instantaneous active power:

$Q_g=u_g\·i_g=U_g^1{I}_g^{1}cos({\mathrm{\θ}}_u^1-{\mathrm{\θ}}_i^1)+U_g^2{I}_g^{2}cos({\mathrm{\θ}}_u^2-{\mathrm{\θ}}_i^2)=P_g^1+P_g^2---\left(1\right)$

Positive-negative sequence electric current and voltage apposition u _g ¹× i _g ¹and u _g ²× i _g ²oppositely, the mean value of three phase reactive power can be obtained:

$q_g=\left|u_g^1\×i_g^1+u_g^2\×i_g^2\right|=\left|u_g^1\×i_g^1\right|-\left|u_g^2\×i_g^2\right|=U_g^1{I}_g^{1}sin({\mathrm{\θ}}_u^1-{\mathrm{\θ}}_i^1)-U_g^2{I}_g^{2}sin({\mathrm{\θ}}_u^2-{\mathrm{\θ}}_i^2)=q_g^1-q_g^2---\left(2\right)$

θ in formula (1) _u ¹, θ _u ¹for voltage-type IIDG terminal voltage positive-negative sequence component phase angle, θ _i ¹, θ _i ²for voltage-type IIDG output current positive-negative sequence component phase angle.

In conjunction with the reciprocation of voltage-type IIDG and power distribution network positive-negative sequence network, obtain the fault current Changing Pattern of voltage-type IIDG, concrete steps are as follows:

During containing voltage-type IIDG power distribution network short circuit calculation, by calculate voltage-type IIDG short circuit current order components initial value in the 1st Δ t, then in a kth Δ t, the steady-state component of IIDG short circuit current is:

${\stackrel{\·}{I}}_{gi\left(k\right)s}=\frac{{\stackrel{\·}{E}}_{gi\left(k\right)}-{\stackrel{\·}{U}}_{iocs}}{Z_{ii}+Z_{gi}}=\frac{{\stackrel{\·}{E}}_{gi\left(k\right)}-{\stackrel{\·}{U}}_{iocs}}{Z_{ii}+Z_{gi}}=I_{gi\left(k\right)s}{e}^{{\mathrm{\θ}}_{is}}---\left(3\right)$

The instantaneous value of formula (3) short circuit currents steady-state component is i _{gi (k) s}(t)=I _{gi (k) s}cos (ω t+ θ _is), in kth-1 Δ t, voltage-type IIDG short circuit current is set to i _{gi (k-1)}(t)=I _{gi (k-1)}cos (ω t+ θ _i), and iIDG built-in potential during iteration secondary to kth, for node i open circuit voltage steady-state value, θ _is, θ _ibe respectively IIDG steady short and temporary short circuit current phase angle.

If during t=0, power distribution network is short-circuited fault, then in a kth Δ t, voltage-type IIDG short circuit current is:

$i_{gi\left(k\right)}\left(t\right)=\[I_{gi(k-1)}{\mathrm{cos\θ}}_i-I_{gi\left(k\right)s}{\mathrm{cos\θ}}_{is}\]e^{-t/{\mathrm{\τ}}_{gi}}+I_{gi\left(k\right)s}cos(\mathrm{\ω}t+{\mathrm{\θ}}_{is})---\left(4\right)$

In formula (4), τ _gi=(L _ii+ L _gi)/(R _ii+ R _gi), L _ii, R _iibe respectively Z _iiinductance and resistance, L _gi, R _gibe respectively Z _giinductance and resistance;

Can obtain voltage-type IIDG short circuit current effective value in a kth Δ t by formula (4) is:

$I_{gi\left(k\right)}\left(t\right)=I_{gi\left(k\right)s}+(I_{gi(k-1)}{\mathrm{cos\θ}}_i-I_{gi\left(k\right)s}{\mathrm{cos\θ}}_{is})e^{-t/{\mathrm{\τ}}_{gi}}---\left(5\right)$

If power outer shroud PI transfer function is G _pI ^p(s)=k _p ^p+ k _i ^p/ s and G _pI ^q(s)=k _p ^q+ k _i ^q/ s, and the phase angle of kth-1 step size voltage type IIDG electromotive force and amplitude are δ _(k-1)and E _{m (k-1)}; Power deviation dP _gand dQ _gafter PI, upgrade built-in potential, the phase angle of i-th voltage-type IIDG built-in potential can be obtained according to PI power outer shroud and amplitude recurrence formula is:

$\left\{\begin{array}{c}{\mathrm{\δ}}_{i\left(k\right)}={\mathrm{\δ}}_{i(k-1)}+k_p^P({\mathrm{dP}}_{gi\left(k\right)}-{\mathrm{dP}}_{gi(k-1)})+\frac{k_i^P\mathrm{\Δ}t}{2}\·({\mathrm{dP}}_{gi\left(k\right)}+{\mathrm{dP}}_{gi(k-1)})\\ E_{mi\left(k\right)}=E_{mi(k-1)}+k_p^Q({\mathrm{dQ}}_{gi\left(k\right)}-{\mathrm{dQ}}_{gi(k-1)})+\frac{k_i^Q\mathrm{\Δ}t}{2}\·({\mathrm{dQ}}_{gi\left(k\right)}+{\mathrm{dQ}}_{gi(k-1)}),i=2,...,m+1\end{array}\right.---\left(6\right)$

In formula, k _p ^p, k _i ^p, k _p ^q, k _i ^qfor the parameter of power outer shroud PI transfer function.

As a kind of prioritization scheme of the present invention, calculate the symmetrical component iterative algorithm of the power distribution network short circuit current containing voltage-type IIDG, calculate the short circuit current of the power distribution network containing voltage-type IIDG, concrete steps are as follows:

1., original distribution nodal impedance matrix Z is formed _o ¹and Z _o ², by voltage-type IIDG set value of the power, built-in potential before calculating voltage type IIDG fault fault front voltage and PRE-FAULT CURRENT

2., Z is utilized _o ¹, Z _o ²calculating voltage type IIDG positive-negative sequence damping time constant τ _gi ¹and τ _gi ²;

3., k=1 is made;

4., according to accident analysis principle of stacking, power distribution network is resolved into two networks of normal operation and fault component, each node voltage positive-negative sequence component can be calculated the active reactive power P of each voltage-type IIDG _{gi (k-1)}and Q _{gi (k-1)};

5., by the built-in potential positive-negative sequence component of m platform voltage-type IIDG substitute into fault positive-negative sequence net, calculate the short circuit current stable state positive-negative sequence component of IIDG kth-1 Δ t and the active power positive-negative sequence power steady-state component P of correspondence ¹ _{gi (k-1) s}, P ² _{gi (k-1) s}, reactive power positive-negative sequence steady-state component Q ¹gi (k-1) s, Q ²gi (k-1) s;

6. formula (5) calculating voltage type IIDG kth Δ t short circuit current positive-negative sequence steady-state component, is utilized and the active power positive-negative sequence steady-state component P of correspondence ¹ _{gi (k)}, P ² _{gi (k)}, reactive power positive-negative sequence steady-state component Q ¹ _{gi (k)}, Q ² _{gi (k)};

7., by when normally running, dP _{gi (0)}=0, dQ _{gi (0)}=0, calculate the voltage-type IIDG active power deviation dP of a kth Δ t _{gi (k)}with reactive power dQ _{gi (k)}; Voltage-type IIDG electromotive force phase angle and the amplitude of a kth Δ t is tried to achieve, i.e. the equivalent electromotive force of voltage-type IIDG positive-negative sequence net by formula (8)

8., k=k+1 is made;

If 4. 9. iterations k≤N, then return step; Otherwise accident analysis terminates, export the short circuit current positive-negative sequence component of each voltage-type IIDG

Compared with prior art, tool of the present invention has the following advantages: a kind of symmetrical component method calculated containing voltage-type IIDG power distribution network short circuit current that the present invention proposes, consider that IIDG power controls the reciprocation with network equation, and using alternative manner to realize the decoupling computation of built-in potential control and network equation, the phase component method adopted during short circuit calculation can effectively reduce the complexity of phase components method and solve scale; The voltage-type IIDG short circuit calculation order components analytic modell analytical model set up; be conducive to the combination of IIDG control mode and distribution network failure analytical method, and the calculating of IIDG short circuit current order components can be used for distribution protection and the control under power distribution network unbalanced fault thereof.

Accompanying drawing explanation

Fig. 1 is the equivalent circuit diagram of node i access voltage-type IIDG.

Fig. 2 is the Thevenin's equivalence circuit of voltage-type IIDG access node i.

Fig. 3 is voltage-type IIDG short circuit current Changing Pattern schematic diagram.

Fig. 4 is applicable to the flow chart containing voltage-type IIDG power distribution network short circuit calculation symmetrical component method.

Embodiment

For making the object of the embodiment of the present invention, technical scheme and advantage more clear, below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described.

Core of the present invention is to provide a kind of short circuit calculation symmetrical component method be applicable to containing voltage-type IIDG power distribution network, and the method can realize the analytical Calculation of voltage-type IIDG short circuit current.Adopt phase component method to carry out short circuit calculation can effectively reduce the complexity of phase components method and solve scale, and the calculating of IIDG short circuit current order components can be used for distribution protection and the control under power distribution network unbalanced fault thereof.Therefore, set up the order components analytic modell analytical model of voltage-type IIDG short circuit calculation, be more conducive to the combination of IIDG control mode and distribution network failure analytical method, the short circuit current of accurate calculating voltage type IIDG.

During power distribution network diverse location access multiple stage voltage-type IIDG, its equivalence is become voltage source access electrical network, obtain shown in accompanying drawing 1 containing voltage-type IIDG power distribution network equivalent circuit, IIDG three-phase average power and positive-negative sequence net power relation during derivation unbalanced fault thus, and obtain the equivalent circuit shown in accompanying drawing 2 according to Thevenin's equivalence, and then set up voltage-type IIDG short circuit calculation order components model; In conjunction with the reciprocation of IIDG and power distribution network positive-negative sequence network, the fault current Changing Pattern of derivation voltage-type IIDG; Finally, the symmetrical component iterative algorithm of the power distribution network short circuit current calculated containing voltage-type IIDG is proposed.Concrete implementation step is as follows:

S1: when analyzing power distribution network unbalanced fault, voltage-type IIDG three-phase average power and positive-negative sequence net power relation, concrete steps are as follows:

Voltage-type IIDG three-phase instantaneous power is by its terminal voltage vector u _g=[u _ga, u _gb, u _gc] and current phasor i _g=[i _ga, i _gb, i _gc] determine, three phases active power p _g=u _gi _g, three phase reactive power q _g=| u _g× i _g|; When power distribution network unbalanced fault, voltage-type IIDG terminal voltage u _gand current i _gall comprise positive-negative sequence component, i.e. u _g=u _g ¹+ u _g ², i _g=i _g ¹+ i _g ², wherein, u _g ¹, u _g ²for the positive-negative sequence component of voltage-type IIDG terminal voltage, for the positive-negative sequence component of voltage-type IIDG electric current.Three phases active power is the half-period average value of instantaneous active power:

$Q_g=u_g\·i_g=U_g^1{I}_g^{1}cos({\mathrm{\θ}}_u^1-{\mathrm{\θ}}_i^1)+U_g^2{I}_g^{2}cos({\mathrm{\θ}}_u^2-{\mathrm{\θ}}_i^2)=P_g^1+P_g^2---\left(1\right)$

Positive-negative sequence electric current and voltage apposition u _g ¹× i _g ¹and u _g ²× i _g ²oppositely, the mean value of three phase reactive power can be obtained:

$q_g=\left|u_g^1\×i_g^1+u_g^2\×i_g^2\right|=\left|u_g^1\×i_g^1\right|-\left|u_g^2\×i_g^2\right|=U_{gg}^1{I}^{1}sin({\mathrm{\θ}}_u^1-{\mathrm{\θ}}_i^1)-U_g^2{I}_g^{2}sin({\mathrm{\θ}}_u^2-{\mathrm{\θ}}_i^2)=q_g^1-q_g^2---\left(2\right)$

θ in formula (2) _u ¹, θ _u ¹for voltage-type IIDG terminal voltage positive-negative sequence component phase angle, θ _i ¹, θ _i ²for voltage-type IIDG output current positive-negative sequence component phase angle.

S2: set up and take into account voltage-type IIDG short circuit calculation order components model, concrete steps are as follows:

Suppose containing n node in accompanying drawing 1 power distribution network, and have m platform voltage-type IIDG to access power distribution network, node 1 is the equivalent power supply point of major network, and node 2 is IIDG access point to (m+1).As shown in Figure 2, its medium value electromotive force is node i open circuit voltage to node i thevenin equivalent circuit equivalent internal impedance is the self-impedance Z of node i _ii, node i open circuit voltage is:

${\stackrel{\·}{U}}_{ioc}=\underset{j=1,j\≠i}{\overset{m+1}{\Σ}}{Z}_{ij}{\stackrel{\·}{I}}_j=Z_{i1}{\stackrel{\·}{I}}_{s1}+\underset{j=2,j\≠i}{\overset{m+1}{\Σ}}{Z}_{ij}{\stackrel{\·}{I}}_{gj},i=2,...,m+1---\left(3\right)$

In formula (3), with the promise being respectively power supply point is paused equal currents and jth platform IIDG Injection Current.The IIDG that is incorporated into the power networks during normal operation adopts power limitation control, can obtain its power output be by accompanying drawing 2:

$P_{gi}+{\mathrm{jQ}}_{gi}=\frac{{\stackrel{\·}{E}}_{gi}{Z}_{ii}+{\stackrel{\·}{U}}_{ioc}{Z}_{gi}}{Z_{ii}+Z_{gi}}\·{\left(\frac{{\stackrel{\·}{E}}_{gi}-{\stackrel{\·}{U}}_{ioc}}{Z_{ii}+Z_{gi}}\right)}^{*},i=2,...,m+1---\left(4\right)$

In formula (4), P _gi, Q _giwith the active power of i node voltage type IIDG, reactive power and built-in potential is accessed, Z when being respectively normal operation _gi=Z _ti+ Z _fifor the equivalent internal impedance of IIDG, Z _ti, Z _fibe respectively IIDG Transformer Short Circuit Impedance and filtering impedance, Z _iifor the self-impedance of node i, for node i open circuit voltage.M platform IIDG can be calculated in the machine end electric current of steady operation point and built-in potential phasor according to formula (3) and (4).

S3: in conjunction with the reciprocation of voltage-type IIDG and power distribution network positive-negative sequence network, obtain fault current Changing Pattern and the recurrence formula of voltage-type IIDG:

For the calculation of short-circuit current containing voltage-type IIDG power distribution network, need to consider that IIDG built-in potential regulates the reciprocation with network equation, and adopt alternative manner to realize the decoupling computation of IIDG built-in potential and network equation in failure process, concrete steps are as follows:

During containing voltage-type IIDG power distribution network short circuit calculation, by calculate voltage-type IIDG short circuit current order components initial value in the 1st Δ t; The steady-state component that can be obtained IIDG short circuit current in a kth Δ t by accompanying drawing 2 is:

${\stackrel{\·}{I}}_{gi\left(k\right)s}=\frac{{\stackrel{\·}{E}}_{gi\left(k\right)}-{\stackrel{\·}{U}}_{iocs}}{Z_{ii}+Z_{gi}}=\frac{{\stackrel{\·}{E}}_{gi\left(k\right)}-{\stackrel{\·}{U}}_{iocs}}{Z_{ii}+Z_{gi}}=I_{gi\left(k\right)s}{e}^{{\mathrm{\θ}}_{is}}---\left(5\right)$

The instantaneous value of formula (5) short circuit currents steady-state component is i _{gi (k) s}(t)=I _{gi (k) s}cos (ω t+ θ _is), in kth-1 Δ t, voltage-type IIDG short circuit current is set to i _{gi (k-1)}(t)=I _{gi (k-1)}cos (ω t+ θ _i), and iIDG built-in potential during iteration secondary to kth, for node i open circuit voltage steady-state value, θ _is,θ _ibe respectively IIDG steady short and temporary short circuit current phase angle, Z _gi=Z _ti+ Z _fifor the equivalent internal impedance of IIDG, Z _ti, Z _fibe respectively IIDG Transformer Short Circuit Impedance and filtering impedance, Z _iifor the self-impedance of node i.If power distribution network is short-circuited fault during t=0, then in a kth Δ t, IIDG short circuit current is:

$i_{gi\left(k\right)}\left(t\right)=\[I_{gi(k-1)}{\mathrm{cos\θ}}_i-I_{gi\left(k\right)s}{\mathrm{cos\θ}}_{is}\]e^{-t/{\mathrm{\τ}}_{gi}}+I_{gi\left(k\right)s}\cos (\mathrm{\ω}t+{\mathrm{\θ}}_{is})---\left(6\right)$

In formula (6), τ _gi=(L _ii+ L _gi)/(R _ii+ R _gi), L _ii, R _iiand L _gi, R _gibe respectively Z _iiand Z _giinductance, resistance.Can obtain IIDG short circuit current effective value in a kth Δ t by formula (6) is:

$I_{gi\left(k\right)}\left(t\right)=I_{gi\left(k\right)s}+(I_{gi(k-1)}{\mathrm{cos\θ}}_i-I_{gi\left(k\right)s}{\mathrm{cos\θ}}_{is})e^{-t/{\mathrm{\τ}}_{gi}}---\left(7\right)$

Voltage-type IIDG short circuit current all approximate temporally constant τ in each Δ t of visible access i node _giexponentially attenuation change.Accompanying drawing 3 is voltage-type IIDG short circuit current Changing Pattern.The constant i.e. τ of network configuration in distribution network failure process _giconstant, but the initial current in each Δ t and short circuit current steady-state component difference.Now, because in iteration step length, IIDG built-in potential remains unchanged, the meritorious and reactive power that thus IIDG exports in each Δ t is also approximate presents exponential law change.

If power outer shroud PI transfer function is G _pI ^p(s)=k _p ^p+ k _i ^p/ s and G _pI ^q(s)=k _p ^q+ k _i ^q/ s, and the phase angle of kth-1 step-length IIDG electromotive force and amplitude are δ _(k-1)and E _{m (k-1)}.Power deviation dP _gand dQ _gafter PI, upgrade built-in potential, the phase angle of i-th voltage-type IIDG built-in potential can be obtained according to PI power outer shroud and amplitude recurrence formula is:

$\left\{\begin{array}{c}{\mathrm{\δ}}_{i\left(k\right)}={\mathrm{\δ}}_{i(k-1)}+k_p^P({\mathrm{dP}}_{gi\left(k\right)}-{\mathrm{dP}}_{gi(k-1)})+\frac{k_i^P\mathrm{\Δ}t}{2}\·({\mathrm{dP}}_{gi\left(k\right)}+{\mathrm{dP}}_{gi(k-1)})\\ E_{mi\left(k\right)}=E_{mi(k-1)}+k_p^Q({\mathrm{dQ}}_{gi\left(k\right)}-{\mathrm{dQ}}_{gi(k-1)})+\frac{k_i^Q\mathrm{\Δ}t}{2}\·({\mathrm{dQ}}_{gi\left(k\right)}+{\mathrm{dQ}}_{gi(k-1)}),i=2,...,m+1\end{array}\right.---\left(8\right)$

In formula (8), Δ t is iteration step length, k _p ^p, k _i ^p, k _p ^q, k _i ^qfor the parameter of power outer shroud PI transfer function, δ _{i (k-1)}and E _{mi (k-1)}for the phase angle of kth-1 step size voltage type IIDG electromotive force and amplitude are, dP _{gi (k)}, dQ _{gi (k)}, dP _{gi (k-1)}and dQ _{gi (k-1)}be respectively the power deviation of kth and k-1 step-length.Generate three-phase voltage signal according to IIDG built-in potential phase angle and amplitude, comprise potential component with because voltage-type IIDG adopts symmetrical control, namely its three-phase voltage only comprises positive sequence component ${\stackrel{\·}{E}}_{gi\left(k\right)}^1=E_{mi\left(k\right)}{e}^{{\mathrm{j\δ}}_{i\left(k\right)}}$ With ${\stackrel{\·}{E}}_{gi\left(k\right)}^2=0.$

The IIDG short circuit current effective value I of a kth Δ t end can be calculated when getting t=Δ t in formula (7) _{gi (k)}(Δ t).As shown in Figure 3, it can be used as the initial current of kth+1 iteration step length, the control strategy of recycling voltage-type IIDG upgrades its built-in potential, and then calculates the steady-state current I of kth+1 step-length in conjunction with network equation _{gi (k+1) s}.Utilize the exponential damping law of IIDG fault current in Δ t accordingly, the IIDG fault current of subsequent time can be calculated.

S4: the symmetrical component iterative algorithm proposing the power distribution network short circuit current calculated containing voltage-type IIDG, calculates the short circuit current of the power distribution network containing voltage-type IIDG:

During iterative computation, in iteration step length, IIDG built-in potential remains unchanged, and IIDG fault current exponentially attenuation law, its meritorious and reactive power exported is also approximate presents exponential law change.Calculate the short circuit current of the power distribution network containing voltage-type IIDG, concrete steps are as follows:

1) original distribution nodal impedance matrix Z is formed _o ¹and Z _o ², by voltage-type IIDG set value of the power, simultaneous formula (3) and (4), built-in potential before calculating voltage type IIDG fault fault front voltage and PRE-FAULT CURRENT

2) Z is utilized _o ¹, Z _o ²calculating voltage type IIDG positive-negative sequence damping time constant τ _gi ¹and τ _gi ²;

3) k=1 is made;

4) according to accident analysis principle of stacking, power distribution network is resolved into two networks of normal operation and fault component, in conjunction with Load flow calculation and accident analysis, calculate each node voltage positive sequence component voltage positive-negative sequence component the active-power P of each voltage-type IIDG _{gi (k-1)}and reactive power Q _{gi (k-1)};

5) by the electromotive force positive-negative sequence component of m platform voltage-type IIDG with substitute into the short circuit current stable state positive-negative sequence component that fault positive-negative sequence net calculates IIDG kth-1 Δ t and the active power positive-negative sequence steady-state component P of correspondence ¹ _{gi (k-1) s}, P ² _{gi (k-1) s}, reactive power positive-negative sequence steady-state component Q ¹ _{gi (k-1) s}, Q ² _{gi (k-1) s};

6) formula (7) calculating voltage type IIDG kth Δ t short circuit current positive-negative sequence steady-state component is utilized and the active power positive-negative sequence steady-state component P of correspondence ¹ _{gi (k)}, P ² _{gi (k)}, reactive power positive-negative sequence steady-state component Q ¹ _{gi (k)}, Q ² _{gi (k)};

7) by when normally running, dP _{gi (0)}=0, dQ _{gi (0)}=0, calculate the voltage-type IIDG active power deviation dP of a kth Δ t _{gi (k)}with reactive power dQ _{gi (k)}; Voltage-type IIDG electromotive force phase angle and the amplitude of a kth Δ t is tried to achieve, i.e. the equivalent electromotive force of voltage-type IIDG positive-negative sequence net by formula (8)

8) k=k+1 is made;

9) if iterations k≤N (after fault 10 cycles, N=20), then step S4d is returned; Otherwise accident analysis terminates, export the short circuit current positive-negative sequence component of each voltage-type IIDG

What finally illustrate is, above embodiment is only in order to illustrate technical scheme of the present invention and unrestricted, although with reference to preferred embodiment to invention has been detailed description, those of ordinary skill in the art is to be understood that, can modify to technical scheme of the present invention or equivalent replacement, and not departing from aim and the scope of technical solution of the present invention, it all should be encompassed in the middle of right of the present invention.

Claims (4)

1. be applicable to the short circuit calculation symmetrical component method containing voltage control type IIDG power distribution network, it is characterized in that:

When A, first analysis power distribution network unbalanced fault, voltage-type IIDG three-phase average power and positive-negative sequence net power relation;

The short circuit calculation order components model that voltage-type IIDG symmetry controls is taken into account in B, foundation;

C, reciprocation in conjunction with voltage-type IIDG and power distribution network positive-negative sequence network, obtain fault current Changing Pattern and the recurrence formula of voltage-type IIDG;

D, proposition calculating, containing the symmetrical component iterative algorithm of the power distribution network short circuit current of voltage-type IIDG, calculate the short circuit current of the power distribution network containing voltage-type IIDG.

2. be applicable to the short circuit calculation symmetrical component method containing voltage control type IIDG power distribution network as claimed in claim 1, it is characterized in that, when analyzing power distribution network unbalanced fault in described steps A, voltage-type IIDG three-phase average power and positive-negative sequence net power relation, concrete steps are as follows:

Voltage-type IIDG three-phase instantaneous power is by its terminal voltage vector u _g=[u _ga, u _gb, u _gc] and current phasor i _g=[i _ga, i _gb, i _gc] determine, three phases active power p _g=u _gi _g, three phase reactive power q _g=| u _g× i _g|; When power distribution network unbalanced fault, voltage-type IIDG terminal voltage u _gand current i _gall comprise positive-negative sequence component, i.e. u _g=u _g ¹+ u _g ², i _g=i _g ¹+ i _g ², three phases active power is the half-period average value of instantaneous active power:

$Q_g=u_g\·i_g=U_g^1{I}_g^{1}cos({\mathrm{\θ}}_u^1-{\mathrm{\θ}}_i^1)+U_g^2{I}_g^{2}cos({\mathrm{\θ}}_u^2-{\mathrm{\θ}}_i^2)=P_g^1+P_g^2---\left(1\right)$

Positive-negative sequence electric current and voltage apposition u _g ¹× i _g ¹and u _g ²× i _g ²oppositely, the mean value of three phase reactive power can be obtained:

$q_g=\left|u_g^1\×i_g^1+u_g^2\×i_g^2\right|=\left|u_g^1\×i_g^1\right|-\left|u_g^2\×i_g^2\right|=U_g^1{I}_g^{1}sin({\mathrm{\θ}}_u^1-{\mathrm{\θ}}_i^1)-U_g^2{I}_g^{2}sin({\mathrm{\θ}}_u^2-{\mathrm{\θ}}_i^2)=q_g^1-q_g^2---\left(2\right)$

θ in formula _u ¹, θ _u ¹for voltage-type IIDG terminal voltage positive-negative sequence component phase angle, θ _i ¹, θ _i ²for voltage-type IIDG output current positive-negative sequence component phase angle.

3. be applicable to the short circuit calculation symmetrical component method containing voltage control type IIDG power distribution network as claimed in claim 1, it is characterized in that, described step C is in conjunction with the reciprocation of voltage-type IIDG and power distribution network positive-negative sequence network, and obtain the fault current Changing Pattern of voltage-type IIDG, concrete steps are as follows:

During containing voltage-type IIDG power distribution network short circuit calculation, by calculate voltage-type IIDG short circuit current order components initial value in the 1st Δ t, then in a kth Δ t, the steady-state component of IIDG short circuit current is:

${\stackrel{\·}{I}}_{gi\left(k\right)s}=\frac{{\stackrel{\·}{E}}_{gi\left(k\right)}-{\stackrel{\·}{U}}_{iocs}}{Z_{ii}+Z_{gi}}=\frac{{\stackrel{\·}{E}}_{gi\left(k\right)}-{\stackrel{\·}{U}}_{iocs}}{Z_{ii}+Z_{gi}}=I_{gi\left(k\right)s}{e}^{{\mathrm{\θ}}_{is}}---\left(3\right)$

The instantaneous value of formula short circuit currents steady-state component is i _{gi (k) s}(t)=I _{gi (k) s}cos (ω t+ θ _is), in kth-1 Δ t, voltage-type IIDG short circuit current is set to i _{gi (k-1)}(t)=I _{gi (k-1)}cos (ω t+ θ _i), and iIDG built-in potential during iteration secondary to kth, for node i open circuit voltage steady-state value, θ _is,θ _ibe respectively IIDG steady short and temporary short circuit current phase angle.

If during t=0, power distribution network is short-circuited fault, then in a kth Δ t, voltage-type IIDG short circuit current is:

$i_{gi\left(k\right)}\left(t\right)=\[I_{gi(k-1)}{\mathrm{cos\θ}}_i-I_{gi\left(k\right)s}{\mathrm{cos\θ}}_{is}\]e^{-t/{\mathrm{\τ}}_{gi}}+I_{gi\left(k\right)s}cos(\mathrm{\ω}t+{\mathrm{\θ}}_{is})---\left(4\right)$

In formula, τ _gi=(L _ii+ L _gi)/(R _ii+ R _gi), L _ii, R _iibe respectively Z _iiinductance and resistance, L _gi, R _gibe respectively Z _giinductance and resistance;

Can obtain voltage-type IIDG short circuit current effective value in a kth Δ t by formula (4) is:

$I_{gi\left(k\right)}\left(t\right)=I_{gi\left(k\right)s}+(I_{gi(k-1)}{\mathrm{cos\θ}}_i-I_{gi\left(k\right)s}{\mathrm{cos\θ}}_{is})e^{-t/{\mathrm{\τ}}_{gi}}---\left(5\right)$

If power outer shroud PI transfer function is G _pI ^p(s)=k _p ^p+ k _i ^p/ s and G _pI ^q(s)=k _p ^q+ k _i ^q/ s, and the phase angle of kth-1 step size voltage type IIDG electromotive force and amplitude are δ _(k-1)and E _{m (k-1)}; Power deviation dP _gand dQ _gafter PI, upgrade built-in potential, the phase angle of i-th voltage-type IIDG built-in potential can be obtained according to PI power outer shroud and amplitude recurrence formula is:

$\left\{\begin{array}{c}{\mathrm{\δ}}_{i\left(k\right)}={\mathrm{\δ}}_{i(k-1)}+k_p^P({\mathrm{dP}}_{gi\left(k\right)}-{\mathrm{dP}}_{gi(k-1)})+\frac{k_i^P\mathrm{\Δ}t}{2}\·({\mathrm{dP}}_{gi\left(k\right)}+{\mathrm{dP}}_{gi(k-1)})\\ E_{mi\left(k\right)}=E_{mi(k-1)}+k_p^Q({\mathrm{dQ}}_{gi\left(k\right)}-{\mathrm{dQ}}_{gi(k-1)})+\frac{k_i^Q\mathrm{\Δ}t}{2}\·({\mathrm{dQ}}_{gi\left(k\right)}+{\mathrm{dQ}}_{gi(k-1)}),i=2,\mathrm{...},m+1\end{array}\right.---\left(6\right)$

In formula, k _p ^p, k _i ^p, k _p ^q, k _i ^qfor the parameter of power outer shroud PI transfer function.

4. as claimed in claim 1 containing voltage-type IIDG power distribution network short circuit calculation symmetrical component method, it is characterized in that, described step D proposes the symmetrical component iterative algorithm of the power distribution network short circuit current calculated containing voltage-type IIDG, calculate the short circuit current of the power distribution network containing voltage-type IIDG, concrete steps are as follows:

1., original distribution nodal impedance matrix Z is formed _o ¹and Z _o ², by voltage-type IIDG set value of the power, built-in potential before calculating voltage type IIDG fault fault front voltage and PRE-FAULT CURRENT

2., Z is utilized _o ¹, Z _o ²calculating voltage type IIDG positive-negative sequence damping time constant τ _gi ¹and τ _gi ²;

3., k=1 is made;

4., according to accident analysis principle of stacking, power distribution network is resolved into two networks of normal operation and fault component, each node voltage positive-negative sequence component can be calculated the active reactive power P of each voltage-type IIDG _{gi (k-1)}and Q _{gi (k-1)};

5., by the built-in potential positive-negative sequence component of m platform voltage-type IIDG substitute into fault positive-negative sequence net, calculate the short circuit current stable state positive-negative sequence component of IIDG kth-1 Δ t and the active power positive-negative sequence power steady-state component P of correspondence ¹ _{gi (k-1) s}, P ² _{gi (k-1) s}, reactive power positive-negative sequence steady-state component Q ¹ _{gi (k-1) s}, Q ² _{gi (k-1) s};

6. formula (5) calculating voltage type IIDG kth Δ t short circuit current positive-negative sequence steady-state component, is utilized and the active power positive-negative sequence steady-state component P of correspondence ¹ _{gi (k)}, P ² _{gi (k)}, reactive power positive-negative sequence steady-state component Q ¹ _{gi (k)}, Q ² _{gi (k)};

7., by when normally running, dP _{gi (0)}=0, dQ _{gi (0)}=0, calculate the voltage-type IIDG active power deviation dP of a kth Δ t _{gi (k)}with reactive power dQ _{gi (k)}; Voltage-type IIDG electromotive force phase angle and the amplitude of a kth Δ t is tried to achieve, i.e. the equivalent electromotive force of voltage-type IIDG positive-negative sequence net by formula (8)

8., k=k+1 is made;

If 4. 9. iterations k≤N, then return step; Otherwise accident analysis terminates, export the short circuit current positive-negative sequence component of each voltage-type IIDG