SU1319194A1 - Method of controlling voltage converter with d.c.section - Google Patents

Abstract

The invention relates to electrical engineering and can be used in direct current transmission systems. The aim of the invention is to stabilize the transmitted active power. In this method, the value of the transmitted active power is set, the voltage of the AC network is measured and, depending on these values, the inverter control angle is formed. 1 il. CO with co 1

Description

The invention relates to electrical power engineering and can be used in direct current power transmission systems that use voltage inverter converters.

The aim of the invention is to stabilize the transmitted active power.

The drawing shows a block diagram of a device implementing the proposed method.

Voltage converter 1 includes fully controlled valves 2, reverse diodes, 3, filter capacitor 4. Converter 1 is connected to the AC mains through a transformer 5. On the rectified current side, converter 1 is connected to an adjustable voltage source 6 via a reactor 1, the device contains an AC voltage sensor 8, a rectified voltage sensor 9, blocks 10 and 11 pulsed-phase control, respectively, of the transducer 1 and the source 6, block 12 of the arcctg function realization, comparison block 13, multiplication unit 14, square root extraction unit 15, adder 16, two squaring blocks 17 and 18, two scale amplifiers 19 and 20, two pressure blocks 21 and 22, a block of 23 installation of transmitted active power Sensor 8, block 18, scale amplifier 20, block 22, block 12 and block 10 are connected in series, the output of which is connected to the control inputs of the converter valves 1. The second input of the block 22 is also connected to the OUTPUT of the block 23. The block 17, the adder 16 and the block 15 are connected in series, the output of the latter is connected to the first input of the block 14, and the input of the block 17 is connected to the output of the block 22.

The block 21 and the scale amplifier 19 are connected in series, the output of the latter is connected to the second input

block 14, and the inputs of block 21 are connected to the outputs of block 23 and sensor 8, respectively. The output of the block 13. is connected to the input of the block 1.1, the outputs of which are connected to the control inputs of the source 6. The inputs of the block 13 are connected to the output of the block 14 and the rectified voltage sensor 19.

The Converter operates as follows.

0

five

The condition for the operation of the converter with cos I / ± 1 is the fulfillment of equality

56irV | + 1 35y6 138Т7.

and

Zy woo ,, --- -cos / 3 o 5

Oh j j

Where

the average value of the voltage in the DC circuit; E is the effective value of the phase voltage in the AC network;

/ 5 - angle control converter 1 o

The transmitted active power is determined by the ratio

9fb E Ud. p.-sxn.

Solving together both equations for and and, we get

 „1 E, j

f. - arcct: g; (3.06 -),

PX

2

+ 1

and 0.726 Y- 3.06 -)

The expressions found determine the laws of change / 3 and U,

which ensures the operation of the converter at cos tf ± 1 and Р const.

A device implementing the proposed method works as follows.

The sensor 8 measures the phase voltage E of the AC network, the indicated value enters the block 18. From the output of the block 18 through the large-scale amplifier 20 with a transfer coefficient equal to 3.06 / X, the voltage proportional to Е goes to block 22, on

the other input of which is supplied with voltage from unit 23, which corresponds to the value P of the required active power transmitted through the converter. The value of X is constant, when the converter is connected to the AC mains through transformer X, it is the reactance of the transformer dissipation. From block 22, the voltage proportional to the ratio is fed to the input of block 12, which implements the arcctg function. From the output of block 12, a signal proportional to the angle / 1 is fed to the input of block 10, from the output of which the control pulses are transmitted to vents 2. From the output of block 22, voltage proportional to relation 5 also goes to block 17, from the output of which the signal comes to adder 16, on the other

3 .1

the input of which is given a single signal. The total voltage from the output of the adder 16 comes to block 15, the resulting signal from which goes to block 14, the input of block 21 receives signals from sensor 8 and block 23, from the output of block 22 through scale amplifier 19 with a transfer coefficient equal to 0.726 X , a voltage proportional to the ratio P / E arrives at the second input of block 14. From the output of block 14, a signal proportional to the required voltage U, is transmitted to one input of block 13, to the other input of which a signal comes from the output of sensor 9 rectifier mienny tension. The error signal removed from the output of the block 13 affects the phase-shifting device of the block 11. The control pulses from the output of the block 11 are transmitted to the source gate 6. As a result, the control angle in the converter and the output voltage of the source 6 are set to work with cos If +1 at P const.

The external characteristic of the converter is a characteristic of the current source; therefore, the voltage of such a converter is determined by the external circuit, in this case the rectified voltage of the source 6.

1944

Thus, the proposed method provides a more complete use of the equipment due to its operation with cos tf ± 1 at a stable value transmitted by the active power.

Claims (1)

Invention Formula The method of controlling the converter. voltage with DC link, which measures the voltage of the AC network E and determines the control angle of inverters fb, characterized in that, in order to stabilize the transmitted active power, set the value of the transmitted active power P and the control angle the inverter / form in accordance with the expression , 9 - arcctgOjOe Е 2 / Р-X), and the average value of the voltage Uj in the DC circuit is maintained equal to and  E: 0.726 (VP-X) 2 + 1, where X is the inductive phase impedance of the voltage converter.