CN105375482A - Power-supply network flow calculation method for tramcar - Google Patents

Abstract

The invention discloses a power-supply network flow calculation method for a tramcar. The power-supply network flow calculation method comprises steps of setting a traction substation initial state as Switch on, wherein a locomotive initial model is a constant power source and initial voltage is system floating voltage, utilizing a current vector iterative method to solve a node voltage equation, performing detection on DC bus voltage and regenerative braking locomotive voltage, if the regenerative braking locomotive voltage is greater than Umax or the DC bus voltage of the traction substation is greater than U0+Beta, automatically modifying the model by a program, replacing the regenerative braking locomotive, the voltage of which crosses the limit, with a power supply modified model, solving the new node voltage equation by the program after the model is modified until the voltage of any node does not cross the limit, comparing the power of each generative braking locomotive with the available braking power, and modifying the locomotive model according to a formulated limitation condition. The invention expresses the overvoltage regenerative braking locomotive through the power supply correction model, brings forward an iteration method for modifying internal resistance and thus guarantees the convergence of the flow calculation.

Description

A kind of power supply network tidal current computing method of tramcar

Technical field:

The present invention relates to net Load flow calculation technical field, relate to a kind of power supply network tidal current computing method about tramcar in particular.

Background technology:

Urban tram DC Traction Network tidal current computing method can be divided into two kinds: the linear system tidal current computing method based on constant current supply model locomotive and the non linear system tidal current computing method based on constant power source model locomotive.Adjacent locomotives can not be taken into account due to locomotive by constant current supply modeling and get influencing each other of stream, based on constant power source model locomotive direct-current traction power supply emulation in closer to truth, therefore, present most of direct-current traction power supply software for calculation adopts constant power source model locomotive.But this model can make power flow equation non-linearization, therefore solve by the method for iteration.When calculating with iterative algorithm the traction power network flow considering regenerative braking, situation will become complicated, and regenerating braking energy superfluous in system causes city rail DC Traction Network Load flow calculation to restrain.Therefore, the problem causing city rail DC Traction Network Load flow calculation to restrain for regenerating braking energy superfluous in prior art is improved.

Summary of the invention:

Object of the present invention is exactly the deficiency for prior art, a kind of power supply network tidal current computing method of tramcar is provided, it represents overvoltage regenerative braking locomotive by power supply correction model, proposes a kind of alternative manner revising internal resistance, thus ensure that the convergence of Load flow calculation.

Technology solution of the present invention is as follows:

A power supply network tidal current computing method for tramcar, comprises the following steps,

A) electric traction institute initial condition is set to Swichon, the locomotive initial model of tramcar is constant power source, and initial voltage is system floating voltage;

B) current phasor iterative method is utilized to obtain the solution of nodal voltage equation;

C) DC bus-bar voltage of electric traction and regenerative braking locomotive voltage are tested, if regenerative braking locomotive voltage is greater than U _maxor traction institute DC bus-bar voltage is greater than U ₀+ β, program will revise model automatically, and replaced by the regenerative braking electricity for locomotive source correction model of voltage out-of-limit, after having revised model, program solves new nodal voltage equation again, until arbitrary node voltage is not out-of-limit, U _maxfor voltage threshold limit value, β is the change in voltage allowance allowed.

D) braking power available with it for each regenerative braking locomotive power is compared, according to the limit value condition amendment model locomotive formulated;

E) terminate to calculate.

Preferred as technique scheme, described step c) in power supply correction model be equivalent to the parallel form of current source and internal resistance by Thevenin's theorem.

Preferred as technique scheme, described steps d) in the limit value condition formulated be,

(1) P _brake≤ P ^(k), braking power is less than Traction networks demand power, because power supply correction model is to Traction networks injecting power P ^(k)time, output voltage can not more than U _max, therefore locomotive is to Traction networks injecting power P _braketime, voltage also can not be out-of-limit, at this moment should change back constant power source by regenerative braking model locomotive, ensures that whole braking energies of this car inject electrical network as regenerated energy;

(2) P _brake>P ^(k), braking power is greater than Traction networks demand power, now locomotive brake energy surplus, and unnecessary energy should be braked resistance absorption.The condition that brake resistance drops into is that locomotive voltage reaches U _max, locomotive voltage is tested, if U>U _max-α (α is taken as 1V), so this result meets the requirements, and calculates and terminates; Otherwise, just need to reduce internal resistance, make voltage bring up to U _maxmore than-α.

Beneficial effect of the present invention is: adopt power supply correction model to represent overvoltage regenerative braking locomotive, power supply correction model is in series by ideal voltage source and internal resistance regulating, internal resistance value is adjusted with alternative manner, the locomotive voltage of braking energy surplus can be made to approach locomotive maximum allowable voltage fast, force brake resistance to drop into and absorb superfluous braking energy, make the locomotive voltage of braking energy surplus reach the voltage levvl that brake resistance is dropped into fast, DC Traction Network Load flow calculation can reliable conveyance.

Accompanying drawing illustrates:

Fig. 1 is the flow chart of computational methods of the present invention.

Embodiment:

Embodiment: by particular specific embodiment, embodiments of the present invention are described below, those skilled in the art can understand other advantages of the present invention and effect easily by content disclosed in the present specification.

As shown in Figure 1, a kind of power supply network tidal current computing method of tramcar, comprises the following steps,

A) electric traction institute initial condition is set to Swichon, the locomotive initial model of tramcar is constant power source, and initial voltage is system floating voltage;

B) current phasor iterative method is utilized to obtain the solution of nodal voltage equation;

C) DC bus-bar voltage of electric traction and regenerative braking locomotive voltage are tested, if regenerative braking locomotive voltage is greater than U _maxor traction institute DC bus-bar voltage is greater than U ₀+ β, program will revise model automatically, and replaced by the regenerative braking electricity for locomotive source correction model of voltage out-of-limit, after having revised model, program solves new nodal voltage equation again, until arbitrary node voltage is not out-of-limit, U _maxfor voltage threshold limit value, β is the change in voltage allowance allowed.

D) braking power available with it for each regenerative braking locomotive power is compared, according to the limit value condition amendment model locomotive formulated;

E) terminate to calculate.

Concrete computational process is as follows, and DC traction power-supply system can describe with nodal voltage equation below:

[G][U] ⁽ⁿ⁺¹⁾＝[I] ⁽ⁿ⁾

In formula, n is for calculating iterations, and [G] is the node admittance matrix of m × m, and m is interstitial content, [I] ⁽ⁿ⁾be n-th iteration node Injection Current column vector, [U] ⁽ⁿ⁺¹⁾for amount to be asked.

In order to form nodal voltage equation, traction voltage source series resistance model Thevenin's theorem be equivalent to the form of current source shunt resistance.Model locomotive is also converted to ideal current source by constant power source, and its value following formula is asked for.

$I_i^{\left(n\right)}=P_i/U_i^{\left(n\right)}$

In formula, i is locomotive unit number, P _ifor i locomotive power, invariable in an iterative process, its value provides by drawing calculating, hereafter this power is called available horsepower.

[I] is the node current column vector corresponding with [G], is made up of traction institute's Injection Current and locomotive Injection Current.Locomotive initial voltage is system floating voltage, and the size of described floating voltage is 1600V, by formula the locomotive initial current obtained is brought into formula [G] [U] ⁽ⁿ⁺¹⁾=[I] ⁽ⁿ⁾, obtain new locomotive voltage, then new locomotive voltage brought into formula upgrade locomotive electric current, until train voltage deviation reaches License Value, iteration stopping.Nodal voltage equation is system of linear equations, adopts QR decomposition method direct solution nodal voltage equation group in the present embodiment.

Represent overvoltage regenerative braking locomotive by power supply correction model in the present embodiment, this model changes power output and voltage by amendment internal resistance, thus restriction excess energy injects Traction networks.Power source model is in series by ideal voltage source and adjustable internal resistance, and voltage source numerical value is set to locomotive maximum permissible voltage U _max, described maximum permissible voltage U _maxsize be 1800V, can ensure that locomotive voltage can not more than U like this _max.Internal resistance initial value is tried to achieve by following formula:

${\mathrm{Re}}^{\left(0\right)}=\frac{P_{Brake}}{(U_{max}-U_0)U_0}$

In formula, U ₀for traction institute floating voltage, described floating voltage size is 1600V, P _brakefor by drawing the available brake power of this locomotive calculated, wherein, injecting electrical network direction is just.By formula the Re obtained ⁽⁰⁾the output voltage of power supply can be made to equal U ₀time power output be P _brake.

The functional relation of output power of power supply and output voltage is:

$P\left(U\right)=-\frac{1}{\mathrm{Re}}{(U-\frac{U_{max}}{2})}^2+\frac{U_{max}^2}{4\mathrm{Re}}$

By formula find out, output power of power supply is the binary function of locomotive voltage and internal resistance.When power output P is constant, reduces internal resistance value and can improve output voltage U.

The energy that regenerative braking locomotive injects Traction networks is regenerated energy.Work as Re=Re ^(k)time, the regenerative braking locomotive based on power source model injects the power P of Traction networks ^(k)=(U _max-U ₀) U ₀/ Re ^(k).Then judge that whether locomotive brake energy is superfluous.

(1) P _brake≤ P ^(k), braking power is less than Traction networks demand power, because power supply correction model is to Traction networks injecting power P ^(k)time, output voltage can not more than U _max, therefore locomotive is to Traction networks injecting power P _braketime, voltage also can not be out-of-limit, at this moment should change back constant power source by regenerative braking model locomotive, ensures that whole braking energies of this car inject electrical network as regenerated energy.

(2) P _brake>P ^(k), braking power is greater than Traction networks demand power, now locomotive brake energy surplus, and unnecessary energy should be braked resistance absorption.The condition that brake resistance drops into is that locomotive voltage reaches U _max, locomotive voltage is tested, if U>U _max-α (α is taken as 1V), so this result meets the requirements, and calculates and terminates; Otherwise, just need to reduce internal resistance, make voltage bring up to U _maxmore than-α.

When output power of power supply is constant, at interval U ∈ (U _max/ 2, U _max) on, output voltage can be expressed as the monotropic function of internal resistance.

$U\left(\mathrm{Re}\right)=\sqrt{\frac{U_{max}^2}{4}-\mathrm{Re}\·P}+\frac{U_{max}}{2}$

Because this function is non-linear, so with alternative manner modified R e.Iterative process is: first give Re initialize, again forms nodal voltage equation and asks for U, then according to U and U _maxdifference modified R e, through successive ignition, finally make U>U _max-α.

Formula at interval U ∈ (U _max/ 2, U _max) on inverse function be:

$\mathrm{Re}\left(U\right)=-\frac{1}{P}{U}^2+\frac{U_{max}}{P}U$

Re (U) is elementary function, so at interval U ∈ (U _max/ 2, U _max) on can lead, and then can be micro-in any point in this interval.

So, according to formula $\mathrm{Re}\left(U\right)=-\frac{1}{P}{U}^2+\frac{U_{max}}{P}U$ Differential form

$d\mathrm{Re}=(-\frac{2}{P}U+\frac{U_{max}}{P})dU$

Draw following iterative formula:

${\mathrm{Re}}^{(k+1)}={\mathrm{Re}}^{\left(k\right)}+(-\frac{2}{P^{\left(k\right)}}{U}^{\left(k\right)}+\frac{U_{max}}{P^{\left(k\right)}})(U_{max}-U^{\left(k\right)})$

Wherein, U ^(k), P ^(k)for Re=Re ^(k)time the trend solution that calculates.

In Practical Calculation process, different Re ^(k)under the P that calculates ^(k)change, but no matter P ^(k)how becoming, the variation tendency of U-Re curve is constant, according to formula ${\mathrm{Re}}^{(k+1)}={\mathrm{Re}}^{\left(k\right)}+(-\frac{2}{P^{\left(k\right)}}{U}^{\left(k\right)}+\frac{U_{max}}{P^{\left(k\right)}})(U_{max}-U^{\left(k\right)})$ The Re calculated ^(k+1)always than Re ^(k)little, be equivalent to improve power supply capacity, so just can reach the effect improving electric power output voltage.

Traction institute's rectifying device conducting and cut-off state is represented with Switchon and Switchoff in Load flow calculation.When traction institute, busbar voltage is greater than U ₀during+β, this traction institute internal resistance is set to a very large number, makes high-impedance state that traction becomes, i.e. Switchoff state; Otherwise change back Switchon by traction institute state.

Described embodiment in order to illustrative the present invention, but not for limiting the present invention.Any those skilled in the art all without prejudice under spirit of the present invention and category, can modify to described embodiment, therefore the scope of the present invention, should listed by claim of the present invention.

Claims (3)

1. a power supply network tidal current computing method for tramcar, is characterized in that: comprise the following steps,

A) electric traction institute initial condition is set to Switchon, the locomotive initial model of tramcar is constant power source, and initial voltage is system floating voltage;

B) current phasor iterative method is utilized to obtain the solution of nodal voltage equation;

C) DC bus-bar voltage of electric traction and regenerative braking locomotive voltage are tested, if regenerative braking locomotive voltage is greater than U _maxor traction institute DC bus-bar voltage is greater than U ₀+ β, program will revise model automatically, and replaced by the regenerative braking electricity for locomotive source correction model of voltage out-of-limit, after having revised model, program solves new nodal voltage equation again, until arbitrary node voltage is not out-of-limit, U _maxfor voltage threshold limit value, β is the change in voltage allowance allowed.

D) braking power available with it for each regenerative braking locomotive power is compared, according to the limit value condition amendment model locomotive formulated;

E) terminate to calculate.

2. the power supply network tidal current computing method of a kind of tramcar according to claim 1, is characterized in that: described step c) in power supply correction model be equivalent to the parallel form of current source and internal resistance by Thevenin's theorem.

3. the power supply network tidal current computing method of a kind of tramcar according to claim 1, is characterized in that: described steps d) in formulate limit value condition be,

(1) P _brake≤ P ^(k), braking power is less than Traction networks demand power, because power supply correction model is to Traction networks injecting power P ^(k)time, output voltage can not more than U _max, therefore locomotive is to Traction networks injecting power P _braketime, voltage also can not be out-of-limit, at this moment should change back constant power source by regenerative braking model locomotive, ensures that whole braking energies of this car inject electrical network as regenerated energy;

(2) P _brake>P ^(k), braking power is greater than Traction networks demand power, now locomotive brake energy surplus, and unnecessary energy should be braked resistance absorption.The condition that brake resistance drops into is that locomotive voltage reaches U _max, locomotive voltage is tested, if U>U _max-α, α are taken as 1V, and so this result meets the requirements, and calculate and terminate; Otherwise, just need to reduce internal resistance, make voltage bring up to U _maxmore than-α.