RU2115994C1 - Converter of direct voltage to alternating voltage using smooth regulation of output characteristics - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: device has input filter, which is connected to inverter, which has first and second thyristor gates, transformer, which primary winding is connected to outputs of said gates, generator of commutation pulses, which has thyristor gate with opposing diodes, pulse transformer with low-voltage secondary winding, resonance circuit. In addition device has additional thyristors which are connected between terminal of secondary winding of pulse transformer and output of second thyristor gate of inverter. Device control unit provides synchronous arrival of control current pulses to circuits of control junctions of thyristors of inverter, generator of commutation pulses and additional thyristors. EFFECT: increased dynamic range of output characteristics, decreased power consumption, increased efficiency. 3 dwg

Description

 The invention relates to the field of semiconductor converters and is intended for use in transport and for powering various technological devices.

 Known converters containing autonomous inverters with artificial switching current, in which the switching pulse is supplied to the thyristors through a pulse transformer and diode isolation [1] (prototype).

 The disadvantage of such inverters is the need to perform artificial switching elements at the full voltage of the power source and the pulse transformer at full load power, which increases the mass of the converter and the cost of its equipment. In addition, in order to ensure stable operation of the inverter, the unlocking of the next group of thyristors of the inverter bridge must be carried out with a delay relative to the moment of the end of the switching pulse for a time longer than the turn-off time of the controlled valves. This circumstance limits the output power of the converter, reduces its efficiency and reduces the range of regulation of the output voltage.

 The aim of the invention is to remedy these disadvantages.

 This goal is achieved by the fact that the converter contains an input filter, a control unit and an inverter cell, including two power thyristor switches, the first of which contains counter diodes, a transformer and a switching voltage pulse generator connected to the plus and minus input terminals by the input and consisting of a thyristor key with counter diodes, between the output of which and the output of the first power thyristor switch of the indicated cell, the primary winding of the switching transformer is connected and vibrate flax circuit, and said inverter cell is provided with two additional thyristors through which to input of the second thyristor switch is connected with the secondary winding of said transformer pulse generator. The control unit is designed to provide a synchronous supply of current pulses to the control transition circuits of the corresponding main thyristors and thyristor switch gates of the switching voltage pulse generator, as well as to supply current pulses to the control transition circuits of additional thyristors with an adjustable delay relative to the moment of supply of current pulses for unlocking the thyristor valves .

 This goal in terms of expanding the range of regulation of the output voltage is provided by supplying current pulses to the control transition circuit of additional thyristors with an adjustable delay relative to the moment the thyristor key valves are unlocked, and in terms of reducing the installed power of the equipment and increasing the efficiency, the converter is equipped with additional thyristors and the switching transformer is made with low voltage a secondary winding connected to the terminals of the thyristor key of the switching pulse generator and the output of the thyristor key through these additional thyristors.

 In FIG. 1 shows a schematic diagram of the proposed Converter; in FIG. 2 and 3 are timing diagrams illustrating its operation at different values of the output voltage pulse durations.

 The proposed Converter contains the first and second keys of the inverter, including thyristors 1-4, counter diodes 5.6, transformer 7, a switching voltage pulse generator, including a key on thyristors 8.9 with counter diodes 10.11, an oscillating circuit containing a reactor 12 and a capacitor 13, a pulse transformer 14 with a secondary winding 15, the terminals of the primary winding of which are connected to the output terminals of the first key of the inverter and the key of the specified generator, and the secondary winding 15 is connected in series to the circuit between the outputs of the pointer keys through additional thyristors 16, 17. In addition, the converter includes an L-shaped filter containing a reactor 18 and a capacitor 19, and a control unit 20, which generates control current pulses in a given time sequence.

 The load 21 is connected to the secondary winding of the transformer 7.

 The outputs of the control unit 20 are connected through a galvanic isolation unit 22 with control transitions of thyristors 1-4, block 23 - thyristors 8, 9, block 24 - thyristors 16, 17.

 In the initial time interval of the converter operation at a low voltage at the output, current pulses from the outputs of the control unit arrive only in the control transition circuits of the successive thyristors 1,2 and 8,9 and with some delay relative to the switching voltage pulses in the control transition circuits of the additional thyristors 16, 17 .

 With a further increase in the voltage at the output, the control unit 20 provides the simultaneous unlocking of the thyristors 8, 16, and 9, 17, respectively. In this case, with some advance with respect to the switching voltage pulses, determined by the voltage value at the output, current pulses from the control unit outputs in the control circuit thyristor transitions 1.4 and 2, 3.

 The action of the converter is as follows. In the initial control interval, thyristors 3, 4 are locked and the DC voltage conversion is carried out by thyristors 1, 2 of the first switch, 8, 9 of the switching voltage pulse generator and additional thyristors 16, 17.

At time t _1, a current pulse i _y1 enters the control transition circuits of thyristors 1, 9. At the same time, a rectangular voltage pulse U _{k of} negative polarity is formed at the output of the switching voltage pulse generator and on the primary winding of transformer 14 (Fig. 2). The amplitude of this pulse by the transformer 14 increases by 10-15%. The duration of this pulse is determined by the parameters of the reactor 12 and the capacitor 13 of the oscillatory circuit.

на первичной обмотке трансформатора 7. Через тиристоры 1, 9 протекает результирующий ток нагрузки и контура коммутации. Поскольку амплитуда импульса тока i_k превышает максимальное значение тока нагрузки более чем в 2 раза, то в момент времени t₃ ток через вентили 1,9 меняет свое направление и его обратная полуволна протекает через диоды 5, 11. С этого момента времени начинается процесс восстановления запирающих свойств тиристоров 1,9. Для обеспечения устойчивой работы преобразователей необходимо выполнение условия, при котором длительность импульса обратной полуволны тока через диоды 5,11 была больше времени выключения тиристоров 1,2 и 8,9, а амплитуда тока через колебательный контур превышала максимальное значение тока нагрузки в 2 раза.At time t _{2, the} current pulse i _y3 enters the control transition circuit of the thyristor 17, the unlocking of which provides the appearance of a voltage pulse

on the primary winding of the transformer 7. The resulting load current and the switching circuit flows through the thyristors 1, 9. Since the amplitude of the current pulse i _k exceeds the maximum value of the load current by more than 2 times, then at time t _{3 the} current through the valves 1.9 changes its direction and its inverse half-wave flows through the diodes 5, 11. From this moment in time, the recovery process begins locking properties of thyristors 1.9. To ensure the stable operation of the converters, it is necessary to fulfill the condition under which the duration of the reverse half-wave current through the 5.11 diodes was longer than the turn-off times of the thyristors 1.2 and 8.9, and the amplitude of the current through the oscillating circuit exceeded the maximum value of the load current by 2 times.

At time t _{4, the} current through the diodes 5, 11 becomes equal to 0 and the voltage U _{V is} restored on the valves 1, 5 and 9, 11. At the same time, thyristors 1.9 remain in a locked state. After turning off the diodes 5.11, the load current flows along the circuit, which includes the primary winding of the transformer 7, thyristor 17, the winding 15 of the pulse transformer, reactor 12 and capacitor 13.

положительной полярности.At time t _{5, the} current pulse i _y2 enters the control transition circuits of thyristors 2, 8, the unlocking of which leads to the appearance of a voltage pulse U _{k of} positive polarity at the output of the switching pulse generator. Further, when a current pulse i _{i4 appears} in the control transition circuit of the thyristor 16 and a pulse is formed on the primary winding of the transformer 7

positive polarity.

After reducing the delay time for unlocking thyristors 16, 17 to zero, sequential thyristors 3, 4 are introduced into operation, which are unlocked alternately by current pulses i _y5 , i _y6 simultaneously with thyristors 1, 2.

At time t _1, a current pulse i _y1 (Fig. 3) enters the control transition circuits of thyristors 1, 4, the unlocking of which causes a voltage to appear on the primary winding of transformer 7. From this moment on, the voltage on the primary winding of transformer 7 is equal to the voltage at the inverter input .

поступает в цепь управляющих переходов тиристоров 9, 17, отпирание которых приводит к увеличению напряжения U_T1 на первичной обмотке трансформатора 7 на величину напряжения на вторичной обмотке 15 трансформатора 14. В результате этого напряжение на аноде тиристора 4 становится отрицательным относительно потенциала его катода и он выключается. С этого момента начинается процесс восстановления его запирающих свойств, а ток нагрузки протекает по контуру, образованному конденсатором 19, тиристором 1, первичной обмоткой трансформатора 7, тиристором 17, вторичной обмоткой трансформатора 14, и тиристором 9. В момент времени t₃ ток i_V1 через вентили 1, 9 меняет свое направление и переходит в цепь диодов 5, 11. При этом процесс коммутации тока тиристоров происходит аналогично описанному выше. В момент t₄ ток через диоды 5, 11 становится равным 0. С этого момента напряжение на первичной обмотке трансформатора U_T1 резко снижается до величины, близкой 0.At time t _{2, the} current pulse

enters the control transition circuit of the thyristors 9, 17, the unlocking of which leads to an increase in voltage U _T1 on the primary winding of the transformer 7 by the voltage on the secondary winding 15 of the transformer 14. As a result, the voltage at the anode of the thyristor 4 becomes negative relative to the potential of its cathode and it turns off . From this moment, the process of restoring its locking properties begins, and the load current flows along the circuit formed by the capacitor 19, the thyristor 1, the primary winding of the transformer 7, the thyristor 17, the secondary winding of the transformer 14, and the thyristor 9. At time t _{3, the} current i _V1 through valves 1, 9 change their direction and go into the circuit of diodes 5, 11. In this case, the process of switching the thyristor current occurs as described above. At time t _{4, the} current through the diodes 5, 11 becomes equal to 0. From this moment, the voltage on the primary winding of the transformer U _T1 drops sharply to a value close to 0.

At time t _5, a current pulse i _y2 enters the control transition circuit of thyristors 2, 3. Their unlocking ensures that the load current i _t1 flows along the circuit: capacitor 19, thyristor 2, primary winding of transformer 7 and thyristor 3. From this moment, the voltage at the primary the winding again becomes equal to the voltage across the capacitor 19, reversing the sign.

поступает в цепь управляющих переходов тиристоров 8, 16, отпирание которых приводит к увеличению напряжения U_T1 первичной обмотки трансформатора 7 на величину напряжения вторичной обмотки трансформатора 14 и происходит запирание тиристора 3. С этого момента ток нагрузки протекает по контуру: конденсатор 19, тиристор 2, первичная обмотка трансформатора 7, тиристор 16, вторичная обмотка трансформатора 14 и тиристор 8. В момент времени t₇ ток через вентили 2,8 становится равным 0 и переходит в цепь диодов 6, 10. С этого момента начинается процесс восстановления запирающих свойств тиристоров 2, 8. В момент времени t₈ ток через диоды 6, 8 уменьшается до 0, происходит их выключение и напряжение на первичной обмотке трансформатора U_T1 резко снижается до 0. В дальнейшем электромагнитные процессы в преобразователе периодически повторяются.At time t _{6, the} current pulse

enters the control transition circuit of the thyristors 8, 16, unlocking which leads to an increase in the voltage U _{T1 of the} primary winding of the transformer 7 by the voltage of the secondary winding of the transformer 14 and locking the thyristor 3. From this moment, the load current flows along the circuit: capacitor 19, thyristor 2, the primary winding of the transformer 7, the thyristor 16, the secondary winding of the transformer 14 and the thyristor 8. At time t _{7 the} current through the valves 2.8 becomes equal to 0 and goes into the circuit of the diodes 6, 10. From this moment, the process starts the blocking properties of thyristors 2, 8 occur. At time t _{8, the} current through diodes 6, 8 decreases to 0, they turn off and the voltage on the primary winding of transformer U _T1 drops sharply to 0. Further, electromagnetic processes in the converter are periodically repeated.

 The voltage on the primary winding of the transformer 7 and the load has a rectangular shape with steps caused by switching voltage pulses on the secondary winding of the transformer.

 The presence of the transformer 7 in the converter limits the possibility of its operation in the low frequency range. In order to eliminate this drawback, the load should be connected directly to the output terminals of the converter.

Claims (1)

 A DC / AC converter with stepless control of output parameters, containing an input filter connected to an inverter cell including the first and second thyristor switches, each in the form of a pair of series-connected thyristors, each connected by an anode with a positive input terminal, and a cathode with a negative input terminal , a transformer, the primary winding of which is connected to common points of the thyristors of the indicated keys, a switching voltage pulse generator containing a thyristor switch of two of thyristors connected in series, shunted in the opposite direction by diodes and connected by a free anode and cathode with negative and positive input terminals, respectively, a pulse transformer and a resonant circuit shunting its primary winding connected between common points of the thyristors of the first thyristor switch and the thyristor switch of the switching voltage pulse generator , as well as a control unit, characterized in that two additional diodes are inserted into it, connected in parallel the corresponding thyristors of the first thyristor switch, and two additional thyristors connected in parallel with each other and connected between the output of the secondary winding of the pulse transformer and the common point of the thyristors of the second thyristor switch, while the other output of the secondary winding of the pulse transformer is connected to the output of the thyristor switch of the pulse generator, and the unit The control is made providing at the first stage of regulation a synchronous supply of control current pulses in the circuit controlling the transition in the first thyristor key and thyristor key of the pulse generator and the supply with an adjustable delay relative to the moment of unlocking the said keys of the unlocking pulses in the control circuit of the additional thyristors, and in the second stage of regulation - the synchronous supply of control current pulses in the control circuit of the first and second thyristor keys and with adjustable time delay relative to the moment of unlocking the said keys of the unlocking pulses in the control transition circuit of the thyristor key gene pulse generator and additional thyristors.

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