DE19711534A1 - Method for regulating the continuous voltage of a current rectifier - Google Patents

Abstract

Method for regulating the continuous voltage(Ua) of a current rectifier(3), of the type in which: a) the alternating voltage side is connected by a transformer(Tr) to an a.c. source(1) and the continuous voltage(Ua) is output at the continuous side, b) the current regulator is constructed in the form of a four part regulator and has valves(T1 -T4) which can be controlled, c) a control voltage(Uat), for controlling the valves(T1 T4), can be controlled as a function of the voltage regulation having a regulation intensity hierarchically lower, and d) as a function of the difference between a signal proportional to the network supply voltage(UN) and the calculated model voltage of the transformer(UM). The model voltage of the transformer(UM) is calculated with the actualised transformer parameters(R,L). The model voltage of the transformer(UM) is calculated with mean time values taken from the transformer parameters(Rm,Lm). The control voltage(Ustk) is given by the formula: Ustk = UN - DELTA U - UM, DELTA U is the magnitude of the regulation of a regulator(24). The model voltage of the transformer(UM) is given by the formula: UM = Rm(i1pw sin(wt) + iaqwcos(wt) - Lm(i1pw cos(wt) + iaqw sin(wt) Rm and Lm are the values of the ohmic resistance and inductance of the transformer(Tr), i1gw is the magnitude of the regulation for the voltage regulator(22), iaqw is the step value which can be determined for the amplitude of the reactive part of a current sum of the transformer, w is the frequency of the voltage network(UN) and t designates the time.

Description

TECHNICAL AREA

The invention is based on a method for Regulation of the DC voltage of a rectifier according to the Preamble of claim 1.

STATE OF THE ART

With the preamble of claim 1, the invention takes to a prior art reference, as it is from DE 195 42 163 A1 is known. There the DC voltage becomes one Rectifier connected to a 1. Secondary winding of a mains transformer is connected, by means of controllable valves of a 4-quadrant actuator of the Rectifier regulated. A control voltage for this controllable valves is provided by a voltage regulator subordinate current controller specified. By a AC load, e.g. B. an auxiliary device from Railway vehicles, the phase of the primary current of the operatively connected to the rectifier Mains transformer are undesirably moved. To do this compensate, the control voltage is also dependent on Imaginary part of this primary current, which by means of a Fourier analysis is obtained, regulated. This A transformer model is fixed with voltage regulation given transformer parameters for the resulting Winding resistance and the leakage inductance of the Secondary winding and the one converted to the secondary side  Primary winding. The disadvantage is that the relative slow current regulators must compensate for strong control differences, if this z. B. by a temperature increase Change transformer windings. Due to the constant static Load on the controller deteriorates its dynamic Behavior. The current regulator is actually for discontinuities provided by the auxiliary power converter which Train busbar or caused by jumps in the bracket.

PRESENTATION OF THE INVENTION

The invention as defined in claim 1 solves the task of a method for regulating the DC voltage a rectifier of the type mentioned in the beginning to further develop the control dynamics of the converter is improved.

Advantageous embodiments of the invention are in the dependent claims defined.

An advantage of the invention is that the current regulator is relieved and its network behavior is improved. this happens by calculating and averaging the transformer parameters of the Drive units that are slowly tracked while driving.

Through the current recording of the resulting parameters of the Transformers for the individual network circuits are the temperature-dependent resistances and the Couplings of the secondary windings in the bill involved. The scheme can use the same number of Transformer models such as network circuits can be equipped.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated below by means of an embodiment game explained. Show it:

Fig. 1 is a rectifier which is connected on the AC side to a power transformer and the dc side via an inverter to an alternating current load, with an associated control circuit for regulating the direct voltage of the rectifier,

Fig. 2-4 time course of the current controller manipulated variable for circuits of transformer secondary windings 3,

Fig. 5 relative errors of the ohmic resistance of 3 transformer secondary windings and

Fig. 6 relative errors of the inductive resistance 3 transformer secondary windings.

WAYS OF CARRYING OUT THE INVENTION

For the sake of simplicity, the names of are below Voltages, currents with proportional signals and Equal to actual values.

A mains transformer (Tr) has 2 primary windings (PW1) and (PW2) connected in parallel to one another via a current bracket ( 2 ) with a contact line or with an alternating current network ( 1 ) with a single-phase alternating voltage or mains voltage (U _N ) of 15 kV and a frequency of 16 2/3 Hz (or 25 kV and 50 Hz) and on the other hand electrically connected via a vehicle wheel ( 8 ) of a rail vehicle, not shown, to an earthed vehicle rail ( 9 ).

A 1st secondary winding (SW1) of the mains transformer (Tr) is operatively connected to a rectifier ( 3 ) via a 1st current transformer ( 7 ), from which an alternating current strength or a rectifier current (i ₁ ) can be tapped. The rectifier ( 3 ) is a 4-quadrant controller with 4 GTO thyristors (T1-T4) in its bridge branches with anti-parallel diodes. On the DC side, the rectifier ( 3 ) is connected on the one hand via a positive voltage rail (P) and on the other hand via a negative voltage rail (N) via a DC voltage intermediate circuit ( 4 ) to an inverter ( 5 ) which drives an asynchronous machine ( 6 ) on the AC side. The DC voltage intermediate circuit ( 4 ) has a capacitor (C) and a suction circuit. Between the positive voltage rail (P) and the negative voltage rail (N) there is an intermediate circuit voltage or DC voltage (U _d ) which is to be regulated in its amplitude. Instead of the asynchronous machine ( 6 ), a direct current arc furnace or a second alternating current network could also be provided as the alternating current load.

At a k. Secondary winding (SWk) of the mains transformer (Tr) can be connected to the same circuit (not shown) as to the first secondary winding (SW1). At a k. A rectifier current (i _k ) can be tapped from the current transformer ( 7 ).

The control circuit specified below for regulating the amplitude of the direct voltage (U _d ) comprises a PI controller or voltage regulator ( 22 ), to which a predeterminable direct voltage setpoint (U _dw ) and a measured actual value of the rectifier direct voltage (U _d ) are fed on the input side. On the output side, the voltage regulator ( 22 ) supplies a regulator _{manipulated variable} (i _1pw ), corresponding to a setpoint of the amplitude of the active component of the rectifier current (i ₁ ), to a 1st factor input (x) of a multiplier ( 23 ). A second factor input (y) of the multiplier ( 23 ) receives a sine signal (sin (ω.t)) from a sine-cosine generator ( 10 ), to the input of which a signal proportional to the mains voltage (U _N ) is fed, whereby ω is the angular frequency of the alternating current or the mains voltage (U _N ) and t means time.

A PI controller or current controller ( 24 ) receives the rectifier current actual value (i ₁ ) from the first current converter ( 7 ) and a rectifier current setpoint (i _w ) from the output of the multiplier ( 23 ); on the output side, it supplies a current controller manipulated variable (ΔU) to a negating input of a summer ( 25 ). On the output side, this supplies a control voltage (U _St1 ) to a pulse width _modulator or control pulse _generator ( 26 ), which supplies 4 control signals (S26) to the 4 GTO thyristors (T1-T4). For reasons of better clarity, only one connecting line to the GTO Thyristor (T4) is located.

A function generator or Fourier transformer ( 11 ) is supplied on the input side with the actual current value (i ₁ ) from the output of the first current transformer ( 7 ) and the sine signal (sin (ω.t)) from the sine-cosine generator ( 10 ); on the output side, it supplies the real part (Re (i ₁ )) of the fundamental oscillation of the current (i ₁ ), corresponding to the fundamental oscillation component of the Fourier transformation, ie for n = 1, n = ordinal number of the harmonics.

A function generator or Fourier transformer ( 12 ) is supplied on the input side with the actual current value (i ₁ ) from the output of the 1st current transformer ( 7 ) and the cosine signal (cos (ω.t)) from the sine-cosine generator ( 10 ); On the output side, it supplies the imaginary part (IM (i ₁ )) of the fundamental oscillation of the current (i ₁ ), corresponding to the fundamental oscillation component of the Fourier transformation.

For the analysis of periodic signals z (i ₁ , U _N , U _st ) with a digital computer, these signals are sampled N times synchronously with the oscillation period. The Fourier series expansion transforms the signal z from the time domain into the frequency domain; it supplies the sine component or real part of z according to:

and the cosine part or imaginary part (Im (z)) according to:

with N = number of sampling points (e.g. in the range of 20-100), N.T = period of the fundamental, k = continuous Summation number, T = reciprocal sampling frequency and k.T = t = Time.

A function generator or Fourier transformer ( 13 ) is supplied on the input side with an actual value proportional to the mains voltage (U _N ) from the input of the sine-cosine generator ( 10 ) and the sine signal (sin (ω.t)); on the output side, it supplies the real part (Re (U _N )) of the fundamental oscillation of the mains voltage (U _N ).

A function generator or Fourier transformer ( 14 ) is supplied on the input side with an actual value proportional to the mains voltage (U _N ) from the input of the sine-cosine generator ( 10 ) and the cosine signal (cos (ω.t)); on the output side, it supplies the imaginary part (IM (U _N )) of the fundamental oscillation of the mains voltage (U _N ).

In a similar way, Fourier transformers ( 15 ) and ( 16 ) each _{receive a} signal proportional to the control voltage (U _St1 ) on the input side in addition to the sine and cosine signals. On the output side, they supply the real part (Re (U _St1 )) or the imaginary part Im (U _St1 )) of the fundamental _{oscillation of} the control voltage (U _st1 ).

The output signals of the Fourier transformers ( 11-16 ) and a angular frequency signal ω output by the sine-cosine generator ( 10 ) are fed to a function generator ( 17 ) which calculates an ohmic resistance R of the transformer (Tr) according to:

R = {Re (i ₁ ). [Re (U _N ) - Re (U _St1 )] + Im (i ₁ ). [Im (U _N ) - Im (U _St1 )]} / [Re (i ₁ ) ² + Im (i ₁ ) ² ]

and delivers this on the output side to an averager ( 18 ). The function generator ( 17 ) also calculates an inductive resistance L of the transformer (Tr) according to:

L = {Re (i ₁ ). [Im (U _N ) - Im (U _St1 )] - Im (i ₁ ) [Re (U _N ) - Re (U _St1 )]} / {ω. [Re (i ₁ ) ² + Im (i ₁ ) ² ]}

and delivers this on the output side to an averager ( 19 ).

The mean value formers ( 18 ) and ( 19 ) average the incoming values of R and L over a predeterminable time period in the range of 10 s-100 s, preferably of 1 min, and provide mean values R _m and L _{m to} a function generator ( 20 ) Available. Using these mean values R _m and L _{m, the} latter calculates a transformer model voltage U _M according to:

U _M = R _m . [I _1pw .sin (ω.t) + i _Sqw .cos (ω.t)] - L _m . [I _1pw .cos (ω.t) - i _Sqw .sin (ω.t )],

where i _{Sqw is} a predefinable target value for the amplitude of the _{reactive component of} a transformer _{total current} . For an AC voltage source ( 1 ) with low inductance, i _Sqw = 0 can be set. Otherwise you can i _Sqw z. B. determine according to DE 195 42 163 A1.

The transformer model voltage (U _M ) is fed to an inverting input and the mains voltage (U _N ) is fed to a non-inverting input of the summer ( 25 ). In the summer ( 25 ), the control voltage (U _St1 ), which is applied to the control pulse _generator ( 26 ), according to

U _St1 = U _N - ΔU - U _M

educated.

In the same way as it was described for the circuit with the 1st secondary winding (SW1), further circuits can be controlled one after the other, which are connected to other secondary windings, e.g. B. (SWk) are connected. Index 2 then takes the place of index 1 for the actual current value (i ₁ ). . ., generally k.

Figs. 2-4 show the time dependence of the current controller manipulated variables (.DELTA.U) in volts for 3 different secondary windings (SW1,... SWk) of a locomotive, not shown, in a computer simulation. The tracking or updating of the parameters of the transformer (Tr) begins about 0.6 s after the start of the test. The time (t) is plotted on the abscissa in seconds. It can be seen, in particular in FIGS. 2 and 4, that the amplitudes of the current controller manipulated variable (ΔU) decrease sharply shortly after the start of parameter adjustment, which is the aim of the present invention. At the beginning of the control, predetermined transformer parameters are used, as is the case for B. is known from the aforementioned DE 195 42 163 A1.

FIGS. 5 and 6 show in a computer simulation for 3 different secondary windings (SW1,... Swk), corresponding to FIGS. 2-5, the time course of a relative error (.DELTA.R) of the ohmic resistance (R) in% and the time course of a relative error (ΔL) of the inductive resistance (L) in%. ΔR curves ( 27-29 ) in FIG. 5 are assigned to the 3 circuits according to FIGS. 2-4, the same applies to ΔL curves ( 30-32 ) in FIG after the start of the update of the transformer parameters after about 0.6 s.

It is understood that other than those given in the example Circuits, voltages and frequencies can be used. Instead of a discrete component for the regulations, a Microprocessor or computer with which the Calculations and control processes are carried out.

The rectifier ( 3 ) can have valve sets in 2- or 3-point connection. Instead of GTO thyristors (T1-T4) z. B. transistors can be used as electrical valves.

The calculation of the real and blind part in the Fourier transformation can depend on one Harmonics of the network frequency take place, preferably in Dependence on the 1st harmonic.  

Reference list

1

AC voltage source, AC network, catenary

2nd

Current bracket

3rd

Rectifier, 4 quadrant controller

4th

DC link

5

Inverter

6

Asynchronous machine

7

Power converter

8th

Wheel, vehicle wheel

9

Rail, vehicle rail

10th

Sine-cosine generator

11-16

Fourier transformers

17th

Function builder for R and L

18th

Averager for R

19th

Averager for L

20th

Function generator for a transformer model voltage

22

Voltage regulator, PI regulator

23

Multiplier

24th

Current controller, PI controller

25th

Totalizer

26

Pulse width modulator, control pulse generator
C capacitor, intermediate circuit capacitor
cos (ω.t) cosine signal
i electricity
IM imaginary part
i ₁

AC current through SW1, rectifier current, rectifier current actual value
i _k

AC current through SWk
i _1pw

Target value of the amplitude of the active component of i ₁

i _Sqw

Target value of the amplitude of the reactive component of i ₁

i _w

Current setpoint, rectifier current setpoint
L inductance of Tr
L _m

Mean of L
N negative voltage rail from

3rd

P positive voltage rail from

3rd

Ohmic resistance of Tr
Re real part
R _m

Mean of R
sin (ω.t) sinusoidal signal
SW1 1. Transformer secondary winding
SWk k. Secondary transformer winding
t time
Tr transformer, mains transformer
T1-T4 GTO thyristors, controllable electric valves
U _d

Rectifier DC voltage, DC link voltage
U _dw

Setpoint of U _d

U _N

Mains voltage
U _St1

,. . . U _pcs

Control voltage for

3rd

, Output signal from

25th

U _M

Transformer model voltage, output signal from

20th

x, y factors
ΔL relative error of L
ΔR relative error of R
ΔU current controller manipulated variable, output signal from

24th

ω angular frequency of the alternating current of

1

Claims (4)

1. Method for regulating the direct voltage (U _d ) of a rectifier ( 3 ),

• a) which is operatively connected to an AC voltage source ( 1 ) via a transformer (Tr) and on which the DC voltage (U _d ) can be tapped,
• b) which is constructed as a 4-quadrant actuator and has at least one controllable valve (T1-T4) per valve branch,
• c) wherein a control voltage (U _St ) for controlling these controllable valves (T1-T4) in dependence on a voltage regulation with subordinate current regulation and
• d) is also formed as a function of the difference between a signal proportional to the mains voltage (U _N ) and a calculated transformer model voltage (U _M ),
  characterized,
• e) that the transformer model voltage (U _M ) is calculated with updated transformer parameters (R, L).

2. The method according to claim 1, characterized in that the transformer model voltage (U _M ) is calculated with temporal averages of transformer parameters (R _m , L _m ). 3. The method according to claim 2, characterized in that

• a) that the control voltage U _Stk according to:
  U _Stk = U _N - ΔU - U _M
  is formed, wherein ΔU is the current controller manipulated variable of a current controller ( 24 ) of the current control loop, and
• b) that the transformer model voltage U _M according to:
  U _M = R _m . [I _1pw .sin (ω.t) + i _Sqw .cos (ω.t)] - L _m . [I _1pw .cos (ω.t) - i _Sqw .sin (ω.t )]
  is formed, where R _m and L _m mean _{values of} the ohmic resistance R and the inductive resistance L of the transformer (Tr), i _1pw the _{regulator manipulated variable of} a voltage regulator ( 22 ) of the voltage _{control loop} , i _Sqw a predefinable setpoint for the amplitude of the _{reactive component} Total transformer current, ω denote the angular frequency of the mains voltage (U _N ) and t the time, k = 1, 2, 3,. . .

4. The method according to claim 3, characterized in

• a) that the ohmic resistance R of the transformer (Tr) according to:
  R = {Re (i _k ). [Re (U _N ) - Re (U _Stk )] + Im (i _k ). [Im (U _N ) - Im (U _Stk )]} / [Re (i _k ) ² + Im (i _k ) ² ]
  and
• b) the inductive resistance L of the transformer (Tr) according to:
  L = {Re (i _k ). [Im (U _N ) - Im (U _Stk )] - Im (i _k ). [Re (U _N ) - Re (U _Stk )]} / {ω. [Re ( i _k ) ² + Im (i _k ) ² ]}
  is formed, where Re is a real part, Im is an imaginary part of a physical quantity and i _{k is} an actual current value through a secondary winding (SWk) of the transformer (Tr).