FR2761213A1 - PROCESS FOR REGULATING THE CONTINUOUS VOLTAGE OF A CURRENT RECTIFIER - Google Patents

Abstract

A direct voltage (Ua) of a rectifier (3) is regulated by means of controlled valves (T1-T4) belonging to a 4 quadrant regulator of the rectifier (3). A direct voltage (USt) is predetermined by means of a voltage regulator (22) equipped with an intensity regulator (24). The control voltage (USt1) is: Ust1 = UN -DELTAU-UM where DELTAU is the current regulator setting variable (24), the transformer model voltage UM is: (CF DRAWING IN BOPI) Rm, or Lm being updated mean values of the resistance R and the inductance L of the transformer (Tr), i1pw the manipulated variable of the voltage regulator (22), isqw a setpoint value for the amplitude of the reactive part of a transformer sum current, and omega the network frequency.

Description

METHOD FOR REGULATING THE CONTINUOUS VOLTAGE OF A

CURRENT RECTIFIER

  The invention relates to a method for regulating the DC voltage of a current rectifier, wherein: a) the AC voltage side is operably connected by a transformer to an AC voltage source and the DC voltage can be taken from the DC voltage side, b) the current regulator is constructed as a 4-quadrant regulator and has at least one controllable valve for each valve branch, c) a control control voltage for these valves may be be controlled according to a voltage regulation with a lower intensity regulation, and d) in addition, depending on the difference of a signal proportional to the mains voltage and a voltage of calculated transformer model,

  A process of this type is described in DE 19542163.

  In this document, the DC voltage of a current rectifier, which is connected on the AC side to a first secondary winding of a grid transformer, is regulated by controllable valves belonging to a 4-quadrant controller. of the current regulator. A control voltage for these controllable valves is provided by a voltage regulator to which an intensity regulator is assigned, placed hierarchically at a lower position. By the presence of an alternating current load, for example an auxiliary device coming from railway vehicles, the in-phase position of the primary current of the mains transformer, operably connected to the current rectifier, can be undesirably modified. To compensate for this, the control voltage is regulated according to the imaginary part of this primary current, which is obtained by means of a Fourier analysis. At the base of this voltage regulation, there is a transformer model having predetermined transformer parameters, fixed for the winding resistance and the dispersion inductivity of the secondary winding and the primary winding converted on the secondary side. It is therefore disadvantageous that the intensity regulator, which is relatively slow, must regulate the elimination of large differences in regulation, for example when this varies as a result of an increase in the temperature of the transformer windings. . Due to the permanent static load of the regulator, its dynamic behavior eventually deteriorates. The current regulator is provided for the discontinuities caused by the auxiliary current rectifier by the collector rail.

  traction or jumps from the stirrup or pantograph.

  The problem of improving the method for regulating the DC voltage of a current rectifier of the aforementioned type, so as to improve the regulation dynamics of the current rectifier, is solved according to the invention in that the model voltage of transformer is calculated with parameters of

transformer updated.

  According to an advantageous embodiment of the invention, the transformer model voltage is calculated with time average values derived from

transformer parameters.

  According to an advantageous embodiment of the invention, the control voltage Us "is constituted according to the formula: UstC = UN-AU- t, in which AU is the intensity regulator adjustment variable of a regulator intensity (24) of the intensity control circuit, and - the transformer model voltage U is constituted according to the formula:

UM = R. [i.sin (.t + i cos (a.t)] -

  L,. [I cos (and) - i, sin (mt)], Rm and L ,, being mean values of the ohmic resistance R and the inductance L respectively of the transformer, i1 being the control variable of the regulator for the voltage regulator, i ,. being a predetermined set value for the magnitude of the reactive portion of a transformer sum current, θ being the circuit frequency of the

  mains voltage and t denoting the time, k = 1, 2, 3, ...

  and furthermore, the ohmic resistance of the transformer is constituted according to the formula:

  R = {Re (i,). [Re (UN) - Re (Ua)] + Im (i). [Im (U) -

  Im (Um)]} / [Re (ik) 2 + Im (ik> 2] and the inductive resistance L of the transformer is constituted according to the formula:

  L = (Re (ik). [Im (UN) - Im (Um <)] - Im (ik). [Re (UC) -

  Re (U.,)]} / {O. [Re (ik) 2 + Im (i) 2]}, Re being a real part, Im an imaginary part of a physical quantity, Ik being a real value of intensity in a secondary winding of the transformer. An advantage of the invention lies in the fact that the current regulator is discharged and that its network behavior is improved. This is done by calculating and averaging the transformer parameters of the training units which, during rolling, are

resumed slowly.

  Since the current parameters of the transformer for the individual network circuits are apprehended at the present time, the conduction resistances independent of the temperature are taken into account and the couplings of the secondary windings are used in the calculation. The regulation can be equipped with the same number of transformer models as we have for

network circuits.

  The invention is explained below with the aid of an exemplary embodiment. In the drawings: Fig. 1 shows a current rectifier which is connected, on the AC side, to a mains transformer and, on the DC side, to an AC load via an inverter, with the power supply circuit. corresponding regulation for the regulation of the DC voltage of the current rectifier, FIGS. 2-4 represent the temporal evolution of the adjustment variable of the intensity regulator intended for the electronic circuits of 3 secondary transformer windings, FIG. the relative errors of the ohmic resistance of the three secondary transformer windings, and Figure 6 represents the errors of the resistance

  inductive of the 3 secondary transformer windings.

  For the sake of simplicity, we have put on the same plane

  after the designations of the voltages, intensities with the signals, being proportional to them, and the real values. A network transformer (Tr) is electrically operatively connected to two primary windings (PW1) and (PW2) connected in parallel on the one hand, by means of a pantograph (2) to a nip or overhead line, or an alternating current network (1) having a single-phase alternating voltage or a mains voltage (UN) of 15 kV and a frequency of 16 2/3 Hz (or 25 kV and 50 Hz) and, on the other hand, by intermediate of a vehicle wheel (8) of a rail vehicle, not shown, to a connected vehicle rail (9)

To the earth.

  A first secondary winding (SW1) of the network transformer (Tr) is operatively connected to a current rectifier (3) by a first current converter (7), at which an AC current or a current rectifier current (it ) can be taken. The current rectifier (3) is a 4-quadrant regulator having four GTO transistors (T1-T4) in its bridge branches, with diodes connected antiparallel to them. On the DC side, the current rectifier (3) is connected, on the one hand, by a positive voltage rail (P) and, on the other hand, by a negative voltage rail (N), via a DC voltage intermediate circuit (4) to an inverter (5) which drives, on the AC side, an asynchronous motor (6). The DC voltage intermediate circuit (4) has a capacitor (C) and an absorption circuit. Between the positive voltage rail (P) and the negative voltage rail (N), an intermediate circuit voltage or a DC voltage (Ud) is applied, which must be regulated as to its amplitude. Instead of the asynchronous motor (6), it would also be possible to provide a DC arc furnace or a second alternating current grid as an AC load. At a kth secondary winding (SWk) of the network transformer (Tr), it is possible to connect an identical electric circuit (not shown) to that of the first secondary winding (SW1). We can take a current rectifier current (ik) on a kth converter of

current (7).

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  The control circuit shown below, designed for regulating the amplitude of the DC voltage (Ud) comprises a PI regulator, or voltage regulator (22) to which, on the input side, a DC voltage setpoint value is supplied. (Udw) can be predetermined and a measured actual value of the DC voltage rectifier voltage (Ud). On the output side, the voltage regulation (22) provides a regulator regulation quantity (ix,) corresponding to a set value of the amplitude of the real part of the DC rectifier (ix), to a

  first factor input (x) of a multiplier (23).

  A second factor input (y) of the multiplier (23) receives from a sine-cosine generator (10) to which a signal proportional to the mains voltage (UN), a sinusoidal signal (sin (< t)), w being the alternating current circuit frequency, or the frequency

  network (UN), and t being the time.

  On the input side of the first current converter (7), a PI regulator or an intensity regulator (24) receives the actual value of the current rectifier current (ix) and the output of the multiplier (23). a current rectifier setpoint (i,); it provides, on the output side, a current regulator adjustment variable (AU) to a non-inverting input of an adder (25). The latter provides, on the output side, a control voltage (U.se) to a pulse-width modulator or a control pulse generator (26), which supplies 4 control signals (S26) to the four GTO thyristors. (T1 - T4), o, for reasons of better visibility, only

  a connection line to the thyristor GTO (T4) has been drawn.

  On the input side, a function former or a Fourier transformer (11) is supplied with the actual current value (ix) from the output of the first current converter (7) and the sinusoidal signal (sin (wt)). from the sine-cosine generator (10); at the output side, it provides the real part (Re (ix)) of the fundamental oscillation of the current (ix), corresponding to the fundamental oscillation component of the Fourier transform,

  that is, for n 1, n = number of harmonics.

  At the input side, a function trainer or a Fourier transformer (12) is supplied with the actual current value (ix) from the output of the first current converter (7) and the cosine signal (cos (wt)) from the sine-cosine generator (10); at the output side, it provides the imaginary part (IM (i1)) of the fundamental oscillation of the current (ix), corresponding to the component

  of fundamental oscillation of the Fourier transformation.

  For the analysis of the periodic signals z (il, UN, U.t) with a numerical computer, these signals are analyzed according to a multiple N synchronously with respect to the oscillation period. Fourier series development transforms the z signal from the time range into the frequency range; this development furnishes the sine part or the real part of z, according to the formula: ## EQU1 ##. T} k = o and the cosine part, or the imaginary part (Im (z)), according to the formula: N-I Im (z) = 2 / (N.T). {__ z (k) .cos I [n.2 xk.T / (N.T). T} k = o with N = number of scanning points (eg in the range of 20-100, NT = period of time of fundamental oscillation, k = number of progressive summations, T = reciprocal scanning frequency and kT = t

= time.

  At the input side, a function trainer or a Fourier transformer (13) is supplied with the actual value proportional to the mains voltage (UN) coming from the input of the sine-cosine generator (10) and the sinusoidal signal ( sin (wt)); output side, it provides the real part (Re (UN)) of the fundamental oscillation of the voltage

Network (UN).

  To a function trainer, or a Fourier transformer (14) is supplied, on the input side, a real value proportional to the grid voltage (UN) coming from the input of the sine-cosine generator (10) and the sinusoidal signal. (cos (wt)); on the output side, it provides the imaginary part (IM (UN)) of the fundamental oscillation of the

mains voltage (UN>).

  Similarly, the Fourier transformers (15) and (16) receive on the input side, each, a signal proportional to the control voltage (Ust1) in addition to the signals or cosines. On the output side, they provide the real part (Re (U.tx)) Im ((U.t,)) of the oscillation

  fundamental of the control voltage (U.tx).

  The output signals of the Fourier transformers (11-16) and a circuit frequency signal w provided by the sine-cosine generator are fed to a function former (17) which calculates an ohmic resistance (R) of the transformer. (Tr), according to the formula:

R = {Re (il). [Re (UN) -

  Re (U.tx)] + Im (il). [Im (UN) - Im (UT1)]} / [Re (il) 2 + Im (il) 2] and output side, it is provided to a trainer of average values (18). In addition, the function formatter (17) calculates an inductive resistance (L) of the transformer (Tr) according to the formula:

  L = {Re (il). [Im (UN) - Im (UT1)] - Im (i1). [Re (UN) -

  Re (U.t,)]} / {[m.e (i1) 2 + Im (i1) 2]} and gives it, on the output side, to a value trainer

averages (19).

  The average value formers (18) and (19) determine the involved values of R and L over a predeterminable time in the range of 10 s - 100 s, preferably 1 minute, and provide average values R m, or Lm, to a function trainer (20). It calculates with these average values

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  R., or Lm, a transformer model voltage U, according to:

  UM = R-. [I,.,. sin (m-t) + im, .. cos (a.t) 1 -

  L. [ix_.cos (and) - iq..sin (m.t)], where im ,, is a predetermined setpoint value relating to the amplitude of the reactive part of a transformer sum current. For an alternative voltage source (1) of lesser inductivity, it is possible to set iq = 0. Otherwise, is, for example, can be determined

according to DE 19542163 A1.

  The transformer model voltage (U, 4) is fed to an inverting input, and the mains voltage (UN) has a non-inverting input of the summator (25). The control voltage (U.), which is supplied to the control pulse generator (26), is constituted in the summator (25) according to the formula: Um + s = un - AU - X, in the same way that what has been described for the electrical circuit of the first secondary winding (SW1), one can regulate other electrical circuits, following each other temporally, and connected to other secondary windings, for example (SWk). Instead of the index 1 for the actual value of the current (i <), then, correspondingly, the index 2 ..., so

general k.

  FIGS. 2 - 4 show the time dependence of the intensity regulator control variables (AU) expressed in volts, for 3 different secondary windings (SW1, .. SWk) of a locomotive not shown, in a computer simulation . The continuation, or update, of the transformer parameters (Tr) begins about 0.6 seconds after the beginning of the text. The time (t) is plotted in seconds on the abscissa. It can be seen, in particular for FIGS. 2 and 4, that shortly after the beginning of the tracking of the parameters, the amplitudes of the current regulator adjustment variable (AU) are greatly reduced, which is the purpose of the present invention. . At the beginning of the regulation, one works with predetermined transformer parameters, as is known for example from the DE 19542163 A1, cited at the beginning. Figures 5 and 6 show in a computer simulation, for 3 different secondary windings (SW1, .. SWk), corresponding to Figures 2 - 5, the temporal evolution of a relative error (AR) of the resistance ohmic (R) expressed in percent, or the temporal rate of a relative error (AL) of the inductive resistance (L) expressed in percent. The AR curves (27-29) of FIG. 5 are associated with the three electrical circuits of FIGS. 2-4, the same is true for the curves AL (30-32) of FIG. 6. From this, it can be seen that the rapid decrease of the amplitudes of errors after the beginning of the update of the parameters

  transformer, after about 0.6 s.

  It is obvious that one can use other circuits voltages and frequencies than those indicated in the example. Instead of having a discrete component for the regulations, it is possible to provide a microprocessor, or a calculator, by means of which the

  calculations and regulatory processes.

  The current rectifier (3) may have valve sets in a 2 or 3 point circuit. Instead of GTO thyristors (T1 - T4), it is possible, for example, to use

  transistors as electric valves.

  The calculation of the real part and the imaginary part, in the Fourier transformation, can be performed according to a harmonic of the frequency of the network, preferably according to the first harmonic.

Claims (4)

  1. - Method for regulating the DC voltage (Ua) of a current rectifier (3), of the type in which: a) the AC voltage side is functionally connected, by a transformer (Tr), to a voltage source alternative (1) and the DC voltage (Ud) can be taken from the DC voltage side, b) the current regulator is constructed as a 4 quadrant controller and has at least one valve (T1 - T4) which can be controlled, for each valve branch, c) a control voltage (U> t) for controlling these valves (T1 - T4) that can be controlled is formed according to a voltage regulation with a regulation of intensity hierarchically lower, and d) further depending on the difference of a signal proportional to the mains voltage (UN) and a calculated transformer model voltage (UM), characterized in that e) the model voltage of transformer (UM) is calculated with parameters transformers (R, L) updated. 2. Method according to claim 1, characterized in that the transformer model voltage (U ,,) is calculated with time average values derived from   transformer parameters (R ,, L).   3. - Method according to claim 2, characterized in that the control voltage Ust is constituted according to the formula: U ,, = UN - AU - U ^ ,.   AU being the intensity regulator adjustment quantity of an intensity regulator (24) of the intensity control circuit, and b) the transformer model voltage UM being constituted according to the formula:   UM = P. [ion_ sin (e.t) + i.9w.cos (.t)] -   L. [i1., Cos (ot) -is ... sin (wt)], where Rm or Lm are average values of the ohmic resistance R and the inductance L respectively of the transformer (Tr), where i1x is the magnitude regulator setting for the voltage regulator (22), i. being a predetermined setpoint value for the magnitude of the reactive portion of a transformer sum current, being the mains voltage circuit frequency (UN) and t denoting the time, k = 1, 2, 3, ...   4. - Method according to claim 3, characterized in that a) the ohmic resistance of the transformer (Tr) is constituted according to the formula:   R = {Re (ik). [Re (UN) -Re (U,,)] + Im (i,). [Im (UN) -   Im (Um>)]} / [Re (ik) 2 + Im (ik) 2] and b) the inductive resistance L of the transformer (Tr) is constituted according to:   L = {Re (i). [Im (UN) -Im (U,)] - Im (ik). [Re (U,) -   Re (U.tk)]} / {["Re (i) 2 + Im (ik) 2]}, Re being a real part, Im an imaginary part of a physical quantity, Ik being a real value of intensity in a secondary winding (SWk) of transformer (Tr).