SU1511798A1 - Device for controlling self-excited voltage inverter - Google Patents

Abstract

The invention relates to electrical engineering and is used to protect against overvoltages of switching thyristors in the McMurre circuit under capacitive load. The purpose of the invention is to increase reliability by reducing overvoltages. The inverter power circuit contains source 1, operating thyristors 2.3, diodes 4.5, filter 6. Parallel to load 7, a compensating capacitor 8 is turned on. The switching unit contains capacitor 9, reactor 10, thyristors 11, 12. Amplifiers 13 are available to control the thyristors 14, 16, 17 with galvanic isolation associated with the inputs to the control pulse generation unit 15, to the input of which the command unit 20 is connected. The reverse current diode current sensor 21, zero units 22, 23, drivers (differentiators) 24, 25, one-shot 26, 27, elements OR 18, 19. The invention improves the reliability of switching thyristors by reducing overvoltages. The goal is achieved by the introduction of tracking current switching. 2 Il.

Description

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The invention relates to electrical engineering and can be used in converters of direct voltage to alternating, the load of which is capacitive in nature, with the purpose of overvoltage protection.

The aim of the invention is to increase reliability, i.e., by reducing overvoltages when operating on a capacitive load.

Fig „1 shows the scheme of the proposed device; Fig. 2 shows current and voltage diagrams at the elements of the device during its operation.

The device contains a source of 1 constant voltage (expander with capacitive filter, battery and Top.), Connected with pairs of 20 series-connected working transistors 2 and 3 and diodes 4 and 5 "common point of the thyristors through filter 6: dinene with load 7, in parallel with which a capacitor battery is connected

Thyristors 2 and 3 turn on alternately and convert the constant voltage of source 1 to a variable output, which is fed through the filter 6 to the load 7. The filter 6 consists of a capacitor and a reactor tuned to resonance at the output frequency of the inverter, resulting in suppression of higher harmonics on the load 7. It is also possible to perform filter 6 and according to other schemes, for example, in the form of a single reactor „

A capacitor 8i is used to compensate for the reactive power of the load. Since the load 7 varies over a wide range, the capacitive nature of the load impedance for the inverter is possible.

To turn off all of the next thyristor 3 or 2, the previously turned on thyristor 2 or 3 is turned off for

switching-on account of the corresponding com- ator 8o Second load of load 7 of connecting thyristor 11 or 12 "With a midpoint of source 1 in the case of a single-phase inverter (Fig. 1). In the case of a multiphase inverter, this pin is connected to another phase of the inverter or to the zero point of loads. The switching circuit consisting of capacitor 9 and reactor 10,) is connected between the common point of switching thyristors 11 and 12 and working thyristors 2 and 3 Switching thyristors 11 and 12 are connected in series between the poles of the source 1 "The control inputs of thyristors II and 12 tiepe3 amplifiers 13 and 14 are galvanically connected and connected to the outputs of the control pulse generation unit 15, Tristo 2 and 3 in the circuit said bond contain on a series of amplifiers 16 and 17, the elements of the ISH 18 and 19, respectively. 45 A control unit 20 is connected to the control input of the unit 15, which sends a command to lock the switch-on. The switching circuit (9, 10) generates a current opposite to the conductivity of the working thyristor (2 or 3)

The unit 15, which generates signals for switching on working and switching thyristors, performs the functions of generation, phasing, and distribution of control pulses.

The command unit 20 serves to generate a start command for the control pulse generation unit 15 and is necessary for the normal operation of the latter. The outputs of block 15 are amplified by amplifiers .13, 14, 16, and 17

Fig. 2 shows a diagram of a switching current (T9), a voltage across a capacitor 9 (H9), and a voltage across a switching thyristor (NC) not participating in the switching process.

At time t. switch on

thyristor (for example, thyristor 11) .. Up to this point in time, the NC of thyristor 12 was close to zero, since the polarity of the voltage of the capacitor 9 (figO was such that it was subtracted from the source voltage 1 "At time t due to switching on the thyristor I1 to the thyristor I2, the source voltage 1 o is applied. The switching current flows through diode 4, since the thyristor 2 is switched off and the capacitive load current (it is considered

A current 21 is included in the reverse diode circuit, and the output is connected to zero-bodies 22 and 23, the outputs of which through the formers 24 and 25 pulses on the falling front (differentiators) are connected to single-oscillators 26 and 27, the outputs of which are connected to the elements OR 18 and 19, respectively. An inverter is used according to the McMurray scheme, which consists of elements 2, 3, 4, 5, 9, 10, 11 and 12.

The device works as follows.

Thyristors 2 and 3 turn on alternately and convert the constant voltage of source 1 to a variable output, which is fed through the filter 6 to the load 7. The filter 6 consists of a capacitor and a reactor tuned to resonance at the output frequency of the inverter, which results in the suppression of higher harmonics on the load 7. It is also possible to perform filter 6 using other schemes, for example, in the form of a single reactor “

A capacitor 8i is used to compensate for the reactive power of the load. Since the load 7 varies over a wide range, the capacitive nature of the load impedance for the inverter is possible.

To turn off all of the next thyristor 3 or 2, the previously turned on thyristor 2 or 3 is turned off for

account of the inclusion of the corresponding commutation thyristor 11 or 12 "at 0 5 0 5

In this case, the switching circuit (9, 10) creates a current opposite to the conductivity of the working thyristor (2 or 3).

The unit 15, which generates signals for switching on working and switching thyristors, performs the functions of generation, phasing, and distribution of control pulses.

The command unit 20 serves to generate a start command for the control pulse generation unit 15 and is necessary for the normal operation of the latter. The outputs of block 15 are amplified by amplifiers .13, 14, 16, and 17,

Fig. 2 shows a diagram of a switching current (T9), a voltage across a capacitor 9 (H9), and a voltage across a switching thyristor (NR) not participating in the switching process.

At time t. switch on

five

thyristor (for example, thyristor 11) .. Up to this point in time, the NC of thyristor 12 was close to zero, since the polarity of the voltage of the capacitor 9 (FIGURE O was such that it was subtracted from the source voltage 1 "At time t due to thyristor I1 to thyristor I2, a source voltage of 1 o is applied. A switching current flows through diode 4, since thyristor 2 is disconnected and a capacitive load current (

this mode) flows through diode 5. At time t, the switching current T9 drops to zero, the capacitor 9 is charged to the opposite voltage, which is now added to the voltage of source 1, applied to the thyristor 12. a voltage jump occurs, which disappears in time t (in the known circuit) when a control pulse is applied to the thyristor Z0 If this pulse is applied at time t, then there will be no overvoltage. This is the mode that is performed by

lagam scheme ..

 The current sensor 21 during the entire time of the flow of current through the reverse diodes has an output signal that triggers a null organ 22 or 23 (depending on which diode the current flows through). With the disappearance of the current, the signal of the null organ 22 (23) disappears, the shaper 24. (25) starts up, which turns on the one-shot 26 (27) o The latter sends an anticipatory signal through the OR 18 (19) element to start the corresponding amplifier 16 (17) pulses.

Single vibrators are designed to form pulses with a duration exceeding the maximum value

time interval

1-3

and are used because at low load currents (less than the holding current of the thyristor) there is not enough supply of a narrow thyristor starting pulse due to the possibility of turning off the thyristor „

It is impossible to ensure the required operation of the circuit without overvoltages programmatically without monitoring the current of the return diodes 4 and 5 or the switching current due to the fact that the switching reactor 10 is non-linear in nature. In a series of cases, the saturation throttles are connected in series with the thyristors. Under these conditions, the duration tj- t, the half-wave of the switching current T9 will vary depending on the J5J1798

Characteristics from source voltage fluctuations 1. In addition, there are: fluctuations of this magnitude as a function of temperature.

Applying a pulse earlier than the time t2 (to compensate for variations) leads to through-currents, reducing the efficiency if the load becomes inductive. In addition, large current surges occur through the work thyristor introduced into the work, as a result of which the latter can be damaged.

Thus, the proposed device ensures reliable operation of the circuit, excluding overvoltage. As a result, the reliability of operation is improved and the weight and dimensions are reduced by reducing the number of series-connected thyristors in high-voltage installations.

Claims (1)

Invention Formula A device for controlling an autonomous voltage inverter according to the MacMurray circuit, containing a command block of outputs connected to a control pulse generation unit, the outputs of which are connected to amplifiers of switching pulses, and working pulse amplifiers that differ from In order to increase reliability by reducing overvoltages, it is equipped with two OR elements, two one-oscillators, two pulse drivers, two zero-organs, and a current sensor in the reverse diode circuit, current sensor outputs through the chains, each of which contains a serially connected null-organ, a pulse shaper and a one-shot, are connected to the first inputs of the NL elements, the outputs of which are connected to the working pulse amplifiers, and the second inputs are connected to the control pulse generation unit. Fie.2 Editor AoLezhnina Compiled by V.Maltsev Tehred L. Serdyukova Proofreader Oo Tsipl Order 5908/54 Circulation 608 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Production and Publishing Combine Patent, Uzhgorod, st. Gagarin, 101 Subscription