SU1467707A1 - Method of controlling two rectifier converters supplied from common mains - Google Patents

Abstract

The invention relates to electrical engineering and can be used to power a two-motor electric drive, induction heating furnaces. The purpose of the invention is to improve the energy performance. According to the control method, a control signal is generated.

Description

(L

but

about: vj

Phasing of the control angles of like groups by Ti / n, and then synchronously changing the control angles of the thyristors of the cathode groups of each mittener. Using blocks 3 and. 4, the priority parameters (current, active or reactive power) of each converter are monitored, which are compared in block 5 of the priority comparison. Depending on the ratio of the signals at one of the outputs of block 5, we obtain a logical unit that, acting on the opening key 6 or 7, sends a signal to set the angle from block 9 to the adder 10 or 11, where

one

The invention relates to a converter technique and can be used in the control of converter devices feeding the systems of a twin-motor electric drive, induction heating and smelting furnaces of engineering plants and repair shops.

The aim of the invention is to improve the energy performance.

Fig. 1 shows a functional diagram of a device implementing a method for controlling two valve converters; Fig. 2 illustrates voltage and current diagrams of two transducers.

Figure 1 shows two bridge converters 1 and 2 with impulse Hb-phase control units for controlling the cathode and anode groups, the first and second blocks 3 and 4 of the priority parameter measurements included in the secondary transducer circuit to measure the values of the priority parameters (current, active or reactive power), block 5 is compared with two outputs, the inputs of which are connected to the output of blocks 3 and 4, the first and second electronic disconnecting keys 6 and 7, the first inputs of which are connected respectively to the first and second inputs of block 5 , block 8 for The minimum control angle, block 9, is its summation with the setting signal of block 8. As a result, the anode group of one of the converters is acted upon by the sum signal. and the anode group of the other. At the same time, these signals are sent to the cathode groups through nonlinear blocks 12, 14, 13 and 15 corresponding converters. The resonant harmonic separation unit 16 is used to determine the order of the harmonic n resonated in the network, and a signal is formed that is proportional to the resonant harmonic and is fed to the input 9 of the 1G / n angle setting unit. 2 Il.

a tribute to the Tf / n angle, the first and second adders 10 and 11 with two inputs and two outputs, the first inputs of which are connected to the outputs of keys 6 and 7, and the second inputs - with the output of block 8., the second outputs of adders 10 and 11 are connected to the inputs pulse-phase control units of anodic transducer groups, two calculation blocks 12 and 13, connected in series with calculation COSX blocks 14 and 15, whose outputs are connected to the inputs of pulse-phase control blocks of the cathode converter groups, and blocks 14 and 15 have two inputs, the first inputs are connected to the output of blocks 12 and 13, and the inputs of these blocks with the first steps of the adders 10 and 11, the second inputs of the blocks 14 and 15 are given signals U o1 and and o) J setting the input voltages of the first and second converters, block 16 resonant harmonics connected to the mains. The output of block 9 is connected to the second inputs of keys 6 and 7, and the input is connected to the output of block 16. Converters 1 and 2 feed loads 17 and 18.

The control angles of the valve groups of bridge converters (Fig. 2) are respectively equal: the anode group of the first converter,;, the cathode group of the first converter;

l a (- anode group of the second converter dj, the cathode group of the second converter.

If we accept with / 1 af, then taking into account the value of the rectified voltage at the output of the first converter

arccos (

2Ud, U.

- cos

1 minute

where and

of.

Udl,

-purpose voltage at the output of the first converter 5

- the highest rectified voltage.

Taking into account the fact that the effective value of the nth order harmonic is observed when the control pulses of the second converter are shifted by Lc ii / n relative to the first, we obtain

7 MUH

1G / P

arcos

2UcJ5

- cos

(,

nf

 /P),

where u is the rectified voltage at the output of the second converter.

The minimum value of the selected parameter while improving the energy performance of two jointly operating converters is possible if the converter that is less loaded in the selected parameter is used as the first converter.

In the process of controlling two valve converters, in order to improve the harmonic composition of the voltage by selectively affecting the harmonic composition of the current, it is advisable to take the rectified value of the inverter load current as a priority parameter. Since electric networks are characterized by a certain value of inductive resistance, as a result of the passage of current in the line, a voltage drop occurs, the harmonic composition of which is entirely determined by the harmonic composition of the current. In the process of selective action on the harmonic current and current, by changing the angle o (j by the value of the system,

four

to

15

20

25

 .

thirty

35

40

45

50

55

current jolts, and hence voltage fluctuations. The effectiveness of the method in the process of regulating 1 depends on which of the converters is subjected to regulation. Ll reducing the voltage fluctuations in the network when selectively changing the harmonic composition of the current to be regulated less loaded transducer.

The device, implemented the lean method, works as follows.

Let us assume that the ratios of the signals at the output of blocks 3 and 4 are such that they correspond to a positive signal (logical unit) at the first output of block 5. Since the positive signal acts on the opening key 6, the latter is in the open state, and the adder 10 is fed proportional to the angle r from block 8. From the second code of the adder 10, a signal proportional to the angle with it is fed to the control unit of the anode group of the first converter. At the same time, from the first input, the attorney 10 sends a signal proportional to the angle c jMuNi block 12, from the output of which we receive a signal proportional to cos c / l, in-This signal is fed to the first input of the first block 14, and simultaneously to the second input of this block (as a result, at the output of block 14, we get a signal proportional to the angle c {2-1), a signal proportional to the angle 2, fed to the control unit of the cathode group of transducers. As a result, at the output of the first transducer, 11 we get e value of the rectified voltage equal.

At the second output of block 5, there is no signal (logical zero). The opening key 7 is in the closed state and from block 9 a signal proportional to the angle / g / n, determined by the order of the resonant harmonic n, is fed to the second input of the adder 11.

The number of the resonant harmonic is determined using block 15. At the same time, the input of the first adder from block 8 is given a signal proportional to the angle. As a result, at the output of the adder 1 1 forts, the signal is proportional to the fragility of the signal

1-I / n, From the second output of the adder 11, a signal proportional to the angle c / C / shifted by G / n is applied to the anode group of the converter. From the first output of the adder 11, the signal proportional to the angle o / j is fed to the input of block 13, from the output of which we receive a signal proportional to itself. This signal simultaneously with the signal Ucj is fed to the input of the nonlinear block 15, where the angle is calculated. - the nationally calculated angle ci.4i of the block 15 is fed to the input of the control unit, the cathode group of the converter 2, at the output of which we obtain the rectified voltage

If for some reason the load of the second converter has become greater than the load of the first, i.e. the signal at the output of block 4 has become larger than the signal of block 3, then the positive signal is turned on at the second output of block 5. Then converter 2 will become first, and converter 1 will become second, i.e., the angle f / / n will be added to, for converter b. As a result, the device can operate with a minimum consumption of reactive power.

Thus, the method of controlling two valve converters allows improving the energy performance of two converters, by selectively affecting the harmonic composition of distortions in the supply network, eliminating resonance effects on one of the harmonics, expanding the area of efficient use of converters for different current values loads and exerted voltages, as well as to minimize the consumption of reactive power and reduce current and power shocks by increasing nor a priority parameter for regulating and ensuring the phase shift of the control angles of like groups on / off.

The method of controlling two converters has the following advantages: the shape of the mains current of two converters does not contain harmonics

this harmonic allows us to distinguish the area of efficient use of transducers by minimizing the consumption of reactive power.

20

Claims (1)

Formula invented and The method of controlling two valve converters supplied from a common network, which consists in setting the minimum value o (m (/ c control angle, the values of U .j and the output voltages of each converter, include anode thyristors). and cathode groups of converters, at times corresponding to control angles, characterized in that, in order to improve energy performance, the permissible level of external harmonics is set, the required priority parameter is set (current, power, etc.), priority steam the meters of each of the converters compare them to each other and select the converter with the smallest value, set the control angles of the anode groups equal to the minimum value of i („„, measure the values of the highest harmonic currents in the supply network, compare these values with the specified acceptable level m, after which the harmonic components are compared with each other, beyond the given acceptable level, and the harmonic number w, which has the maximum value, is determined, after which the control angle of the anode core is set Uppa converter with the lowest priority parameter equal to (/) control of the cathode converter groups set equal to thirty 40 45 arccos (- cos., about me a cop FOR a converter with a high priority parameter value and 50 arccos 2Uofi - cos g G / n) 1 for converters with a lower priority parameter value. Gnomer, eliminates the unfavorable. where U ,,,, is the maximum rectification-resonance phenomena on the most dangerous voltage of the transformer. / 1467707 6 this harmonic allows us to distinguish the area of efficient use of transducers by minimizing the consumption of reactive power. 0 Formula invented and The method of controlling two valve converters supplied from a common network, which consists in setting the minimum value o (m (/ c control angle, the values of U .j and the output voltages of each converter, include anode thyristors and Cathode transducer groups at times corresponding to control angles, characterized in that, in order to improve energy performance, they set the permissible level of external harmonics, set the required priority parameter (current, power, etc.), measure priority pairs t- 5 ry each of the converters, compare them with each other and select the converter with the smallest value, set the control angles of the anode groups equal to the minimum value i (" m, after which the harmonic components are compared with each other, exceeding the specified acceptable level, and the harmonic number w, which has the maximum value, is determined, after which the control angle of the anode group is set s transducer with the lowest priority parameter equal to (/) control groups cathode converters are set equal to 0 0 45 arccos (- cos., about me a cop FOR a converter with a high priority parameter value and 0 arccos 2Uofi - cos g G / n) 1 for converters with a lower priority parameter value. Fi.E.