CN105958485A - Power flow calculation method for flexible interconnecting alternating current-direct current hybrid power distribution network - Google Patents

Abstract

The invention provides a power flow calculation method for a flexible interconnecting alternating current-direct current hybrid power distribution network. The power flow calculation method comprises the steps of A, establishing an alternating current power distribution system model and a direct current power distribution system model; B, disassembling the alternating current and direct current hybrid power distribution system; C, establishing a mathematical model for a power exchange interface between an alternating current sub network and a direct current sub network; D, carrying out power flow calculation on the alternating current sub network; E, carrying out power flow calculation on the direct current sub network; and F outputting the power flow calculation result. According to the technical scheme provided by the invention, the alternating current and direct current hybrid power distribution system is disassembled into the alternating current system and the direct current system; different power flow calculation methods are carried out on the alternating current system and the direct current system separately; and in addition, power exchange is only implemented on certain calculation nodes, so that the calculation speed is greatly enhanced.

Description

A kind of tidal current computing method of flexible interconnection alternating current-direct current mixing power distribution network

Technical field

The present invention relates to the tidal current computing method that a kind of power distribution network runs, a kind of flexible interconnection is handed over straight The tidal current computing method of stream mixing power distribution network.

Background technology

Alternating current-direct current mixing power distribution network can preferably receive distributed power source and DC load, alleviates urban distribution network station The contradiction that some corridor finite sum load density is high, can provide dynamic reactive support at load center simultaneously, and carry The safety and stability level of high system.In alternating current-direct current mixing power distribution network, flexible direct current technology changes power distribution network Topological structure, improves the power flowcontrol ability of by stages.But the net occurred in alternating current-direct current mixing distribution system Network and a large amount of DC equipment significantly change grid structure and the method for operation of conventional AC power distribution network.

Load flow calculation is one of substance of power system computation, is also power system safety and stability calculating point The basis of analysis, in planning and designing, runs in control and extensively applies.Need to open to alternating current-direct current mixing distribution system Sending out high-speed simulation instrument corresponding, it is the basic function that emulates of alternating current-direct current mixing power distribution network that Power flow simulation calculates. Along with the continuous expansion of alternating current-direct current mixing electrical network scale, its convergence calculated to Power flow simulation brings new Challenge.The engineering calculation of ultra-large alternating current-direct current mixing power distribution network is frequently encountered Load flow calculation convergence difficulties The phenomenon even not restrained, causes cannot effectively obtaining feasible solution, seriously constrains work efficiency, and affect Follow-up safety and stability computational analysis.The tidal current computing method of existing AC system is the most ripe, but Be ultra-large alternating current-direct current mixing distribution system Load flow calculation convergence problem be always difficult point, be simultaneous for What the Load flow calculation algorithm of AC/DC network was main concentrates on power transmission network field, the structure and parameter of distribution network Unsymmetry, the feature such as complexity of network size cause alternating current-direct current mixed current computational methods with in power transmission network The difference of tidal current computing method.

Accordingly, it is desirable to provide a kind of technical scheme meets the needs of prior art.

Summary of the invention

In order to overcome above-mentioned the deficiencies in the prior art, the present invention provides a kind of flexible interconnection alternating current-direct current mixing power distribution network Tidal current computing method, it comprises the steps:

A. alternating-current system and direct-flow distribution system model are set up；

B. partition AC and DC mixing distribution system；

C. the mathematical model of Power Exchange interface between exchange subnet and direct current subnet is set up；

D. described exchange subnet is carried out Load flow calculation；

E. described direct current subnet is carried out Load flow calculation；

F. calculation of tidal current is exported.

Step A includes: set up AC system power flow equation and straight-flow system power flow equation.

AC system power flow equation is as follows:

$\left\{\begin{array}{c}{P}_{di}-P_{DGi}-P_{DCi}=V_i\underset{j\∉i}{\Σ}{V}_j(G_{ij}{\mathrm{cos\θ}}_{ij}+B_{ij}{\mathrm{sin\θ}}_{ij})\\ Q_{di}-Q_{DGi}-Q_{DCi}=V_i\underset{j\∉i}{\Σ}{V}_j(G_{ij}{\mathrm{sin\θ}}_{ij}-B_{ij}{\mathrm{cos\θ}}_{ij})\end{array}\right.$

In formula: P_diFor at described AC system interior joint i load have work value, Q_diFor described AC system saves Point i at load without work value；

P_DGiFor the active power of the distributed power source that described AC system interior joint i accesses, Q_DGiFor described friendship The reactive power of the distributed power source that streaming system interior joint i accesses；

P_DCiWork value, Q is had for what described intercommunion subsystem was injected by the described direct current subnet of load at node i_DCi For the described direct current subnet of load at node i described exchange subnet is injected without work value；

V_iFor the voltage magnitude of node i, V_jVoltage magnitude for node j；

G_ijFor the real part of circuit ij admittance, B_ijImaginary part for circuit ij admittance；

θ_ijFor node i and the phase angle difference of node j voltage, wherein i, j ∈ [0, N], N is described AC system In node total number.

Straight-flow system power flow equation is as follows:

$\left\{\begin{array}{c}{P}_{di}-P_{DGi}-P_{ACi}=V_i\underset{j\∉i}{\Σ}{V}_j{G}_{ij}\\ U_{Converter.m}=\frac{3\sqrt{2}}{\mathrm{\π}}{n}_{Cm}{U}_{Cm}cos\mathrm{\α}-\frac{3}{\mathrm{\π}}{n}_{Cm}{X}_{Cm}{I}_{DCm}\\ U_{Inverter.m}=\frac{3\sqrt{2}}{\mathrm{\π}}{n}_{\mathrm{Im}}{U}_{\mathrm{Im}}\cos \mathrm{\γ}-\frac{3}{\mathrm{\π}}{n}_{\mathrm{Im}}{X}_{\mathrm{Im}}{I}_{DCm}\end{array}\right.$

In formula, P_diFor at described straight-flow system interior joint i load have work value；

P_DGiFor the active power of the distributed power source that described straight-flow system interior joint i accesses, P_ACiFor node i The exchange subnet of place's load has work value to direct current subnet injection；

V_iFor the voltage magnitude of described straight-flow system interior joint i, V_jVoltage for described straight-flow system interior joint j Amplitude；

G_ijFor the real part of DC line ij admittance, wherein i, j ∈ [0, N], N is described straight-flow system interior joint Sum；

U_Converter.mFor rectification side voltage, n_cmFor rectifying bridge arm number, α is rectification side Trigger Angle, X_cmFor Rectification side change of current reactance, I_DCmFor DC current；

U_Inverter.mFor inverter side voltage, n_ImFor inverter bridge leg number, γ is inverter side blow-out angle, X_ImFor inverse Become side change of current reactance.

Step B includes:

With flexible interconnection device for partition point, described alternating current-direct current mixing distribution system is divided into exchange subnet with straight Stream subnet.

Power Exchange mathematical model described in step C is as follows:

$\left\{\begin{array}{c}{\mathrm{\ΔP}}_m=P_{{\mathrm{AC}}_m}-P_{{\mathrm{DC}}_m}=0\\ P_{DCm}=U_{Converter.m}*I_{DCm}or{P}_{DCm}=U_{Inverter.m}*I_{DCm}\\ Q_{DCm}=\frac{(U_{Cm}^2-\sqrt{U_{Am}^2{U}_{Cm}^2-P_{Cm}^2{X}_L^2})/X_L}{U_{DCm}^2}\\ Q_{ACm}=Q_{Cm}-\frac{(P_{Cm}^2+Q_{Cm}^2)X_L}{U_{Cm}^2}\end{array}\right.$

In formula, P_ACmFor the active power of inverter AC, P_DCmFor the active power of Converter DC-side, △P_mDifference for inverter both sides active power；

Q_DCmFor the through-put power of described straight-flow system seam, Q_ACmBiography for described AC system seam Defeated power；

U_CmVoltage for straight-flow system seam；

P_CmFor the active power of straight-flow system seam, Q_CmReactive power for straight-flow system seam；

X_LFor the change of current reactance being connected between described AC system with described straight-flow system.

Step D includes: using three-phase forward-backward sweep method to carry out the Load flow calculation of described exchange subnet, it includes Before push through journey and backward steps.

Step E includes: use parallel computation that described direct current subnet is carried out Load flow calculation.

Step F includes: when the calculating of described AC system and described straight-flow system all restrains, and output is corresponding Result is as final calculation of tidal current；

Otherwise, revise the injection value of the power of described exchange subnet and described direct current subnet, re-start calculating straight To convergence.

Compared with immediate prior art, the present invention provide technical scheme have following benefit effect:

1, the present invention can realize alternating current-direct current mixing power distribution network is carried out Power flow simulation calculating, makes up this field Not enough and blank.

2, alternating current-direct current is mixed distribution system and is divided into AC system and straight-flow system calculates respectively by the present invention, adopts With different tidal current computing methods, only on specific calculation node, carry out Power Exchange, be beneficial to parallel, calculate speed Promote substantially.

3, the AC of the present invention uses three-phase Forward and backward substitution method to calculate, it is possible to realize joining three-phase imbalance The calculating of electricity system.

Accompanying drawing explanation

Fig. 1 is the alternating current-direct current mixing power distribution network network containing polymorphic type distributed power source；

Fig. 2 be the present invention be the flexible interconnection alternating current-direct current mixing power distribution network network of the present invention；

Fig. 3 is the alternating current-direct current mixing power distribution network interface schema of the present invention；

Fig. 4 is the alternating current-direct current mixing power distribution network Power Exchange figure of the present invention；

Fig. 5 is the exchange subnet tidal current computing method figure of the present invention；

Fig. 6 is the alternating current-direct current mixing distribution power system load flow calculation flow chart of the present invention.

Detailed description of the invention

Below in conjunction with Figure of description, technical scheme is described in further details.

Typical alternating current-direct current mixing power distribution network topological structure as illustrated in fig. 1 and 2, Fig. 1 is without distributed electrical The alternating current-direct current mixing power distribution network in source, Fig. 2 is that the mixing containing the exemplary distribution formula plant-grid connection such as photovoltaic, wind-powered electricity generation is handed over directly Stream power distribution network.

The method that the present invention provides:

Step 1: alternating current-direct current mixing power distribution network is divided into exchange subnet and direct current according to the position of inverter Net, and set up the model of alternating current-direct current distribution system on this basis, including power flow equation and the direct current of AC system The power flow equation of system, wherein exchange subnet power flow equation is as follows:

$\left\{\begin{array}{c}{P}_{di}-P_{DGi}-P_{DCi}=V_i\underset{j\∉i}{\Σ}{V}_j(G_{ij}{\mathrm{cos\θ}}_{ij}+B_{ij}{\mathrm{sin\θ}}_{ij})\\ Q_{di}-Q_{DGi}-Q_{DCi}=V_i\underset{j\∉i}{\Σ}{V}_j(G_{ij}{\mathrm{sin\θ}}_{ij}-B_{ij}{\mathrm{cos\θ}}_{ij})\end{array}\right.$

In formula, P_di、Q_diFor at AC network interior joint i load have work value and without work value；P_DGi、Q_DGi The active power of distributed power source accessed for AC network interior joint i and reactive power；P_DCi、Q_DCiFor joint At some i, the direct current subnet of load has work value and without work value to exchange subnet injection；V_i、V_jBe respectively node i, The voltage magnitude of j；G_ij、B_ijReal part and imaginary part, θ for circuit ij admittance_ijFor node i, j phase difference of voltage, Wherein i, j ∈ [0, N], N is nodes sum.

Direct current subnet power flow equation is:

$\left\{\begin{array}{c}{P}_{di}-P_{DGi}-P_{ACi}=V_i\underset{j\∉i}{\Σ}{V}_j{G}_{ij}\\ U_{Converter.m}=\frac{3\sqrt{2}}{\mathrm{\π}}{n}_{Cm}{U}_{Cm}cos\mathrm{\α}-\frac{3}{\mathrm{\π}}{n}_{Cm}{X}_{Cm}{I}_{DCm}\\ U_{Inverter.m}=\frac{3\sqrt{2}}{\mathrm{\π}}{n}_{\mathrm{Im}}{U}_{\mathrm{Im}}\cos \mathrm{\γ}-\frac{3}{\mathrm{\π}}{n}_{\mathrm{Im}}{X}_{\mathrm{Im}}{I}_{DCm}\end{array}\right.$

In formula, P_diFor at DC network interior joint i load have work value；P_DGiConnect for DC network interior joint i The active power of the distributed power source entered；P_ACiFor the exchange subnet of load at node i, direct current subnet is injected There is work value；V_i、V_jIt is respectively the voltage magnitude of direct current subnet interior joint i, j；G_ijFor DC line ij admittance Real part, wherein i, j ∈ [0, N], N be DC network interior joint sum；U_Converter.mFor rectification side voltage, n_cmFor rectifying bridge arm number, α is rectification side Trigger Angle, X_cmFor rectification side change of current reactance, I_DCmFor unidirectional current Stream；U_Inverter.mFor inverter side voltage, n_ImFor inverter bridge leg number, γ is inverter side blow-out angle, X_ImFor inversion Side change of current reactance, U_cmFor rectification side change of current voltage, U_ImFor inverter side change of current voltage.

Step 2: with the flexible interconnection device of Step1 for partition point, whole alternating current-direct current mixing distribution system is divided It is split into several intercommunion subsystem and direct current subsystem.In the case of ignoring the loss of commutator and inverter, exchange The Power Exchange mathematical model of subnet and direct current subnet interface is as follows:

$\left\{\begin{array}{c}{\mathrm{\ΔP}}_m=P_{{\mathrm{AC}}_m}-P_{{\mathrm{DC}}_m}=0\\ P_{DCm}=U_{Converter.m}*I_{DCm}or{P}_{DCm}=U_{Inverter.m}*I_{DCm}\\ Q_{DCm}=\frac{(U_{Cm}^2-\sqrt{U_{Am}^2{U}_{Cm}^2-P_{Cm}^2{X}_L^2})/X_L}{U_{DCm}^2}\\ Q_{ACm}=Q_{Cm}-\frac{(P_{Cm}^2+Q_{Cm}^2)X_L}{U_{Cm}^2}\end{array}\right.$

In formula, P_ACmThe active power injected for commutator or inverter ac side, P_DCmFor commutator or inverse Become the active power of device DC side, △ P_mDifference for inverter both sides active power；

Q_DCmFor straight-flow system seam through-put power；Q_ACmFor AC system seam through-put power；U_Cm For straight-flow system seam voltage, U_AmFor AC system seam voltage；P_CmFor straight-flow system seam Active power, Q_CmReactive power for straight-flow system seam；

X_LIt is connected reactance with straight-flow system for AC system.

Voltage and the coupled relation of power between exchange subnet and direct current subnet can be calculated by above formula.

Fig. 3 shows exchange subnet and the exchange flow graph of direct current each variable of subnet, wherein, Load flow calculation Time, need direct current subnet to be injected into the power P of exchange subnet by inverter_DC,Q_DC, calculate exchange subnet In four variable P, Q, U, θ；And the variable U in direct current subnet_DC, need to exchange subnet and connect in AC system Voltage U at Kou_ACSolve.Set the voltage of AC and DC subnet, power initial value and convergence precision ε_ac、 ε_dc, and configuration node voltage matrix Z.

Step 3: for alternating current-direct current mixing power distribution network, start system is carried out Load flow calculation from exchange subnet.

As shown in Figure 4, each flexible interconnection device is that AC system power is injected by straight-flow system to calculation process Entrance, the size of injecting power is depended on last straight-flow system calculation of tidal current, and is connect by Power Exchange Mouth is determined.

Due to the isoparametric asymmetrical type of load in distribution, the solving of AC system that the present invention provides uses three phase fronts Push back and solve for method, it include as follows before push through journey and backward steps:

(1) the front journey that pushes through:

Each node injection current is shown below；

${\left[\begin{array}{c}{I}_{ja}\\ I_{jb}\\ I_{jc}\end{array}\right]}^{\left(k\right)}=\left[\begin{array}{c}{(S_{ja}/U_{ja}^{(k-1)})}^{*}\\ {(S_{jb}/U_{jb}^{(k-1)})}^{*}\\ {(S_{jc}/U_{jc}^{(k-1)})}^{*}\end{array}\right]+\left[\begin{array}{ccc}{Y}_{ja}& & \\ & Y_{jb}& \\ & & Y_{jc}\end{array}\right]{\left[\begin{array}{c}{U}_{ja}\\ U_{jb}\\ U_{jc}\end{array}\right]}^{(k-1)}$

In formula, I_ja, I_jb, I_jcRepresent node j each phase injection current, S_ja, S_jb, S_jcRepresent that node j bears mutually Lotus power, U_ja, U_jb, U_jcRepresent each phase voltage of node j, Y_ja, Y_jb, Y_jcRepresent that node j the most relatively leads Receiving, k represents iterations.

It is calculated as follows from the beginning of feeder terminal, the calculating of the branch current in opposite tide direction:

${\left[\begin{array}{c}{I}_{la}\\ I_{lb}\\ I_{lc}\end{array}\right]}^{\left(k\right)}=-{\left[\begin{array}{c}{I}_{ja}\\ I_{jb}\\ I_{jc}\end{array}\right]}^{\left(k\right)}+\underset{m\∈M}{\Σ}{\left[\begin{array}{c}{I}_{ma}\\ I_{mb}\\ I_{mc}\end{array}\right]}^{\left(k\right)}$

In formula, I_la, I_lb, I_lcRepresenting each phase current of branch road l, M is all lower floors branch road that node j is connected Set, branch road m is the element in composition M set, i.e. branch road m be lower floor's branch road of being connected with node j it One.

(2) backward steps:

From the beginning of feeder line head end, the node voltage in fair tide direction be calculated as follows shown in formula:

${\left[\begin{array}{c}{U}_{ja}\\ U_{jb}\\ U_{jc}\end{array}\right]}^{\left(k\right)}={\left[\begin{array}{c}{U}_{ia}\\ U_{ib}\\ U_{ic}\end{array}\right]}^{\left(k\right)}-\left[\begin{array}{ccc}{Z}_{aa}& Z_{ab}& Z_{ac}\\ Z_{ba}& Z_{bb}& Z_{bc}\\ Z_{ca}& Z_{cb}& Z_{cc}\end{array}\right]{\left[\begin{array}{c}{I}_{la}\\ I_{lb}\\ I_{lc}\end{array}\right]}^{\left(k\right)}---\left(4\right)$

In formula: U_ia, U_ib, U_icRepresent each phase voltage of node i.Z_aaFor the self-impedance of a phase, Z_ab、Z_baFor The mutual impedance that a phase is alternate with b, Z_ac、Z_caFor the mutual impedance that a phase is alternate with c, Z_bbFor the self-impedance of b phase, Z_ccSelf-impedance for c phase.

Push away and two processes of back substitution before above-mentioned, complete an iteration and calculate.Push away before next round in iteration, Use one and take turns the node voltage calculating power attenuation that backward steps is tried to achieve.Push away before Mei Ci in iteration, by network voltage Calculating power is distributed；In back substitution iteration, power distribution calculate voltage's distribiuting.Repeat said process, until front The modulus value of the node voltage difference of rear twice iteration stops iteration when meeting required precision, and output AC subnet result is made For result of calculation.

Step 4: then each direct current subsystem is carried out Load flow calculation, each direct current subsystem can also be adopted Solve with parallel computation.

There is not reactive power and voltage phase angle in calculating in DC power flow, determine the control model of grid-connecting apparatus with And the control strategy of DG circulation, direct current subnet node is divided into voltage-type and power-type node.

For the direct current subnet of m voltage-type node and n power-type node, carry out trend as the following formula Calculate:

DC(X^(k))=[Δ P_dc1,ΔP_dc2,…,ΔP_dcn,ΔV_dc1,ΔV_dc2,,…,ΔV_dcm]

ΔP_dcFor the active power increment of power-type node, Δ V_dcMagnitude of voltage increment for voltage-type node.

Wherein unknown variable:

X=[P_dc1,P_dc2,…,P_dcn,V_dc1,V_dc2,,…,V_dcm]

P_dcFor the active power of power-type node, V_dcMagnitude of voltage for voltage-type node.

Above-mentioned equation can be solved by Newton iteration method:

${\mathrm{\ΔX}}^{\left(k\right)}=J_{DC}^{-1}*DC\left(X^{\left(k\right)}\right)$

With Δ X modified chi, X^(k+1)=X^(k)-ΔX^(k).Obtain new direct current net node power and magnitude of voltage. J_DCJacobin matrix for direct current subnet.

During kth time iteration, meet max (| Δ X^(k)|) ＜ ε time terminate, wherein ε be set convergence limit.

Step 5: as it is shown in figure 5, when the calculating of AC system and straight-flow system all reaches convergence, export phase The result answered is as final calculation of tidal current.

Otherwise, revising the injection value of the power of AC and DC side, re-starting calculating until restraining.

Finally should be noted that: it is only limited by above example in order to technical scheme to be described System, those of ordinary skill in the field still can be to the detailed description of the invention of the present invention with reference to above-described embodiment Modifying or equivalent, these replace without departing from any amendment or the equivalent of spirit and scope of the invention Change, within the claims of the present invention all awaited the reply in application.

Claims (9)

1. the tidal current computing method of a flexible interconnection alternating current-direct current mixing power distribution network, it is characterised in that include as follows Step:

A. alternating-current system and direct-flow distribution system model are set up；

B. partition AC and DC mixing distribution system；

C. the mathematical model of Power Exchange interface between exchange subnet and direct current subnet is set up；

D. described exchange subnet is carried out Load flow calculation；

E. described direct current subnet is carried out Load flow calculation；

F. calculation of tidal current is exported.

Tidal current computing method the most according to claim 1, it is characterised in that described step A includes: build Grade separation streaming system power flow equation and straight-flow system power flow equation.

Tidal current computing method the most according to claim 2, it is characterised in that described AC system trend side Journey is as follows:

$\left\{\begin{array}{c}{P}_{di}-P_{DGi}-P_{DCi}=V_i\underset{j\∉i}{\mathrm{\Σ}}{V}_j(G_{ij}{\mathrm{cos\θ}}_{ij}+B_{ij}{\mathrm{sin\θ}}_{ij})\\ Q_{di}-Q_{DGi}-Q_{DCi}=V_i\underset{j\∉i}{\mathrm{\Σ}}{V}_j(G_{ij}{\mathrm{sin\θ}}_{ij}-B_{ij}{\mathrm{cos\θ}}_{ij})\end{array}\right.$

In formula: P_diFor described AC system interior joint i load have work value, Q_diFor described AC system saves Point i at load without work value；

P_DGiFor the active power of the distributed power source that described AC system interior joint i accesses, Q_DGiFor described exchange The reactive power of the distributed power source that system interior joint i accesses；

P_DCiWork value, Q is had for what described intercommunion subsystem was injected by the described direct current subnet of the load of node i_DCi For the described direct current subnet of the load of node i described exchange subnet is injected without work value；

V_iFor the voltage magnitude of node i, V_jVoltage magnitude for node j；

G_ijFor the real part of circuit ij admittance, B_ijImaginary part for circuit ij admittance；

θ_ijFor the phase difference of voltage between node i and node j, wherein i, j ∈ [0, N], N is described AC system In node total number.

Tidal current computing method the most according to claim 2, it is characterised in that, described straight-flow system trend side Journey is as follows:

$\left\{\begin{array}{c}{P}_{di}-P_{DGi}-P_{ACi}=V_i\underset{j\∉i}{\mathrm{\Σ}}{V}_j{G}_{ij}\\ U_{Converter.m}=\frac{3\sqrt{2}}{\mathrm{\π}}{n}_{Cm}{U}_{Cm}cos\mathrm{\α}-\frac{3}{\mathrm{\π}}{n}_{Cm}{X}_{cm}{I}_{DCm}\\ U_{Inverter.m}=\frac{3\sqrt{2}}{\mathrm{\π}}{n}_{\mathrm{Im}}{U}_{\mathrm{Im}}\cos \mathrm{\γ}-\frac{3}{\mathrm{\π}}{n}_{\mathrm{Im}}{X}_{\mathrm{Im}}{I}_{DCm}\end{array}\right.$

In formula, P_diFor described straight-flow system interior joint i load have work value；

P_DGiFor the active power of the distributed power source that described straight-flow system interior joint i accesses, P_ACiFor node i The exchange subnet of place's load has work value to direct current subnet injection；

V_iFor the voltage magnitude of described straight-flow system interior joint i, V_jVoltage for described straight-flow system interior joint j Amplitude；

G_ijFor the real part of DC line ij admittance, wherein i, j ∈ [0, N], N is described straight-flow system interior joint Sum；

U_Converter.mFor rectification side voltage, n_cmFor rectifying bridge arm number, α is rectification side Trigger Angle, X_cmFor Rectification side change of current reactance, I_DCmFor DC current；

U_Inverter.mFor inverter side voltage, n_ImFor inverter bridge leg number, γ is inverter side blow-out angle, X_ImFor inverse Become side change of current reactance；

U_CmVoltage for described straight-flow system seam.

Tidal current computing method the most according to claim 1, it is characterised in that described step B includes:

With flexible interconnection device for partition point, described alternating current-direct current mixing distribution system is divided into exchange subnet with straight Stream subnet.

Tidal current computing method the most according to claim 1, it is characterised in that merit described in described step C Rate exchange mathematical model is as follows:

$\left\{\begin{array}{c}{\mathrm{\ΔP}}_m=P_{{\mathrm{AC}}_m}-P_{{\mathrm{DC}}_m}=0\\ \begin{array}{ccc}{P}_{DCm}=U_{Converter.m}*I_{DCm}& or& P_{DCm}=U_{Inverter.m}*I_{DCm}\end{array}\\ Q_{DCm}=\frac{(U_{Cm}^2-\sqrt{U_{Am}^2{U}_{Cm}^2-P_{Cm}^2{X}_L^2})/X_L}{U_{DCm}^2}\\ Q_{ACm}=Q_{Cm}-\frac{(P_{Cm}^2+Q_{Cm}^2)X_L}{U_{Cm}^2}\end{array}\right.$

In formula, P_ACmFor the active power of inverter AC, P_DCmWattful power for described Converter DC-side Rate, △ P_mDifference for inverter both sides active power；

Q_DCmFor the through-put power of described straight-flow system seam, Q_ACmBiography for described AC system seam Defeated power；

U_CmFor the voltage of described straight-flow system seam, U_AmVoltage for described AC system seam；

P_CmFor the active power of described straight-flow system seam, Q_CmIdle for described straight-flow system seam Power；

X_LFor the change of current reactance being connected between described AC system with described straight-flow system.

Tidal current computing method the most according to claim 1, it is characterised in that described step D includes: institute The Load flow calculation stating exchange subnet uses three-phase forward-backward sweep method, and it pushes through journey and backward steps before including.

Tidal current computing method the most according to claim 1, it is characterised in that described step E includes: institute The tidal current computing method stating direct current subnet includes parallel computation technique.

Tidal current computing method the most according to claim 1, it is characterised in that described step F includes:

Whether the calculating according to described AC system and described straight-flow system restrains, and determines that the result of output determines As final calculation of tidal current or

Revise the power injection value of described exchange subnet and described direct current subnet, re-start calculating, until convergence.