RU90275U1 - AUTONOMOUS AGREED INVERTER WITH RESONANT COMMUTATION - Google Patents

Abstract

A self-contained matched inverter with resonant switching, containing a single-phase bridge connected to the input terminals of the inverter through filter inductors on controlled valves with on-parallel diodes, a filter capacitor shunted, a single-phase bridge AC output terminal connected to the inverter output terminal through a switching inductor, the inverter output terminals are bridged compensating capacitor, characterized in that the filter chokes are made magnetically coupled and included according to the second yhodnoy output single-phase alternating current bridge is connected to the second output terminal of the inverter via the second commutating reactor, commutating reactors made magnitosvjazannymi and included under a single-phase bridge bypassed series circuit of the two snubber capacitors whose common connection point is connected to the zero output device housing.

Description

The utility model relates to a conversion technique and can be used in the design of power supplies for induction heaters and other high-frequency electrotechnological loads. The utility model improves the reliability of a stand-alone matched inverter with resonant switching.

A self-contained current inverter with quasi-resonant switching is known, comprising a single-phase bridge connected to the input terminals of the current inverter through filter inductors, shunted by a counter diode, single-phase bridge AC output terminals connected to the inverter output terminals through a switching inductor, the inverter output terminals are shunted by a compensating capacitor ( A.S. 1683150 USSR, MKI N02M 5/45. Frequency converter / Silkin EM - Application 03.03.89, Publish 07.10.91, B.I. No. 37).

The disadvantage of a stand-alone current inverter with quasi-resonant switching is its low reliability. This is due to high levels of overvoltage on the controlled valves, which can lead to failure, as well as high levels of electromagnetic interference that occur when the oncoming diode is turned off, which can cause malfunctions in the inverter control system.

A self-contained current inverter with quasi-resonant switching is known, which contains a single-phase bridge connected to the input terminals of the current inverter through a filter choke on controlled valves with counter-parallel diodes, the single-phase bridge AC output terminals are connected to the inverter output terminals through a switching inductor, the output terminals of the current inverter are shunt compensated capacitor (A.S. 1742961 USSR, MKI N02M 5/45. Frequency converter / Silkin EM - Declared 02.08.89, Publ. 23.06.92, B.I. No. 23).

The disadvantage of a stand-alone current inverter with quasi-resonant switching is its low reliability. This is due to high levels of overvoltage on the controlled valves, which can lead to their failure, as well as high levels of electromagnetic interference that occur when off-parallel diodes are turned off, which can cause malfunctions in the inverter control system.

A self-contained matched inverter with resonant switching is known, which contains a single-phase bridge connected to the input terminals of the inverter on controlled gates with counter-parallel diodes, shunted by a filter capacitor, and the output terminals of the single-phase bridge AC are connected to the output terminals of the inverter via a switching inductor and a switching capacitor (Patanov D. A. General problems of reducing switching losses in voltage inverters // Circuitry. - 2001. - No. 5. - P.48).

The disadvantage of a stand-alone matched inverter with resonant switching is the low reliability. This is due to high levels of controlled valve currents and high levels of electromagnetic interference, which can lead to failure of controlled valves due to overheating of the structure and malfunctions in the control system of the inverter, as well as high levels of switching overvoltage on controlled valves due to a sharp break in direct current when turned off, which can cause breakdown of controlled gates and anti-parallel diodes.

A self-contained matched inverter with resonant switching is known, comprising a single-phase bridge connected to the input terminals of the inverter through filter inductors on controlled gates with on-parallel diodes, shunted by a filter capacitor, AC output terminals of a single-phase bridge are connected to the output terminals of the inverter via a switching inductor, output terminals of the inverter shunted by a compensating capacitor (P. 0061964 RF, MKI N02M 7/00. Autonomous matched resonant inverter / Silkin EM - For App. 13.11.06, Publish. 10.03.07, B.I. No. 7).

The specified autonomous matched inverter with resonant switching is the closest in technical essence to a utility model and is selected as a prototype.

The disadvantage of the prototype is the low reliability of the stand-alone matched inverter with resonant switching. This is due to high levels of controlled valve currents and high levels of electromagnetic interference caused by incomplete compensation of load reactivity, which can lead to failure of controlled valves due to overheating of the structure and malfunctions in the inverter control system, as well as high levels of switching overvoltages on controlled valves from -for the interruption of direct current when turning off the anti-parallel diodes and electrical losses, which can cause breakdown of controlled valves and anti-parallel diodes.

The utility model is aimed at solving the problem of improving the reliability of an autonomous matched inverter with quasi-resonant switching, which is the purpose of the utility model.

This goal is achieved by the fact that in a self-contained matched inverter with resonant switching, containing a single-phase bridge connected to the input terminals of the inverter through filter inductors on controlled gates with counter-parallel diodes, shunted by the filter capacitor, the output terminal of the single-phase bridge AC current is connected to the output terminal of the inverter through switching inductor, inverter output terminals are shunted by compensating capacitor, filter inductors are magnetically coupled and included ccording to the second output terminal of the AC single-phase bridge is connected to the second output terminal of the inverter via the second commutating reactor, commutating reactors made magnitosvjazannymi and included under a single-phase bridge bypassed series circuit of the two snubber capacitors whose common connection point is connected to the zero output device housing.

A significant difference characterizing the utility model is an increase in the reliability of an autonomous matched inverter with resonant switching, which is achieved by lowering current levels, electrical switching and static losses and overvoltages on controlled valves and counter-parallel diodes, lowering levels of electromagnetic interference, with the exception of controlled mode overheating modes gates and faults in the inverter control system.

Improving the reliability of a stand-alone coordinated inverter with resonant switching is the technical result obtained due to new elements in the inverter circuit, the order of their inclusion and new connections, that is, the hallmarks of the utility model. Thus, the distinguishing features of the claimed autonomous matched inverter with quasi-resonant switching are essential. The inventive self-contained matched inverter acquires the properties of a new class of inverter with resonant switching.

The figure shows a diagram of an autonomous matched inverter with resonant switching.

A self-contained matched inverter with quasi-resonant switching contains, connected to the input terminals of the inverter via filter inductors 1, 2, a single-phase bridge on controlled valves 3-6 with counter-parallel diodes 7-10, shunted by the filter capacitor 11, the AC output of the single-phase bridge is connected to the output the output of the inverter through the switching inductor 12, the output terminals of the inverter are shunted by a compensating capacitor 13, the filter inductors are magnetically coupled and are turned on according to the second output The AC output terminal of the single-phase bridge is connected to the second output terminal of the inverter via the second switching inductor 14, the switching reactors are magnetically coupled and are connected according to the single-phase bridge is shunted by a series circuit of two snubber capacitors 15, 16, the common connection point of which is connected to the zero output of the device case. A load 17 is connected to the output terminals of the inverter.

Autonomous matched inverter with resonant switching in steady state operates as follows. The control pulses to the controlled valves 3, 6 and 4, 5 arrive alternately with a frequency equal to the frequency of the output signal of the inverter. The values of the inductances of the filter chokes 1, 2 are selected sufficiently large for high-quality filtering of current and voltage at the input of a single-phase bridge. Magnetic coupling and the consonant inclusion of filter chokes 1, 2 reduce the electrical losses in them due to the smaller required total number of turns when performed with the required inductances. Reducing losses reduces the total load of controlled valves 3-6 and anti-parallel diodes 7-10 in power. The compensating capacitor 13 provides parallel compensation of the reactive power of the induction heater (load) 17 and sequential compensation of the reactive power of the switching reactors 12, 14. The switching reactors 12, 14 are made in the form of independent nodes with magnetic coupling or can be fully or partially the inductance of the load (part load) and (or) connecting outlet busbars (cables). It is advisable that the switching chokes 12, 14 be made in the form of independent magnetically coupled elements connected according to, which allows to reduce the loss of electrical energy in them and, therefore, the total load of the controlled valves 3-6 and counter-parallel diodes 7-10 in power.

The full cycle (period) T of the output signal of a self-contained matched inverter with resonant switching consists of two identical time intervals (half-periods) corresponding to various combinations of on and off state of controlled gates 3-6 and counter-parallel diodes 7-10. In each T / 2 half-cycle, in the general case, two different time intervals in the electromagnetic processes can be distinguished (simultaneous operation of two controlled valves of a single-phase bridge and simultaneous conductivity of two adjacent counter-parallel diodes). The main interval corresponds to the simultaneous conduction interval of two controlled valves of a single-phase bridge 3, 6 or 4, 5. The second time interval should be set to a short duration by choosing the parameters of elements 12, 14 and 13, 17, which ensures high energy performance of the device. In the interval of simultaneous conductivity of two adjacent counter-parallel diodes 7, 10 or 8, 9, a small reverse (negative) voltage equal to the voltage drop across the corresponding counter-parallel diode (7-10) and controlled valves (3- 6) can be switched on with minimal switching losses (when using dual-operation valves). At the moment of switching on (the beginning of the half-period T / 2), for example, of the controlled valves 3, 6, the voltage at the compensating capacitor 13 has a conditionally negative polarity (positive potential on the right-side circuit of the compensating capacitor 13). The voltage at the compensating capacitor 13 varies according to the oscillatory law. The voltage level at the compensating capacitor 13 at the moment of switching on the controlled valves 3, 6 is lower than the level of the voltage amplitude value. Snabber capacitors 15, 16 are infected to half the voltage across the filter capacitor 11 (positive potential on the top according to the circuit diagram of the snubber capacitors 15, 16). The controlled valves 3, 6 are turned on ahead of the instants of the instantaneous voltage value across the compensating capacitor 13 relative to the zero level (capacitive detuning of the parallel load circuit 13, 17) and the instantaneous current in the diagonal of the alternating current single-phase bridge of the inverter (inductive detuning of the series oscillatory circuit formed switching chokes 12, 14 and the equivalent capacity of the parallel load circuit 13, 17). As you can see, the valves 3, 6 are turned on at a zero voltage level on them in the conductivity interval of adjacent counter-parallel diodes 7, 10, which leads to minimal electrical losses when turned on. The instantaneous current of valves 3, 6 (4, 5) has a quasi-sinusoidal shape (matched inverter mode). The current through the parallel load circuit formed by the induction heater 17 and the compensating capacitor 13, when the valves 3, 6 are turned on, starts flowing from the filter capacitor 11 of an autonomous matched inverter with resonant switching along the circuit: 11-3-12- (13, 17) -14- 6-11. The filter capacitor 11 has a sufficiently large capacity for high-quality smoothing of the voltage at the input of a single-phase bridge. The filter capacitor 11 is charged from a power source of an autonomous matched inverter with quasi-resonant switching along the circuit: “+” - 1-11-2 - “-”. The compensating capacitor 13 is discharged to zero and, further, oscillatory recharges to a voltage of conditionally positive polarity (positive potential on the left lining according to the scheme). Circuit parameters: 11-3-12- (13, 17) -14-6-11 and advance angles are chosen so that the electromagnetic processes in it also have an oscillatory character. That is, this circuit is a sequential oscillatory circuit formed by commutating chokes 12, 14 and the uncompensated part of the capacitance of the compensating capacitor 13. The current of the controlled valves 3, 6 initially increases and then decreases according to a quasi-oscillatory law. At the moment of equal current control valves 3, 6 to a certain minimum level, they turn off. That is, the shutdown of the controlled valves 3, 6 also occurs ahead of a certain angle relative to the moments of the oscillatory decay of the current through them to zero (inductive detuning of the equivalent sequential oscillatory circuit). The controlled valves 3, 6 are turned off with practically zero switching losses, since the current level through them when turned off is much lower than the maximum current level. At the moment of switching off the controlled valves 3, 6, the first interval of the half-period T / 2 of simultaneous conduction of the controlled valves (3, 6) of the single-phase bridge ends. After turning off the controlled valves 3, 6 in the second interval (pause) due to the electromagnetic energy accumulated in the electromagnetic field of the switching reactors 13, 14, the current in the diagonal of the alternating current flows in the same direction and closes through counter-parallel diodes 8, 9 through the circuit: 12- (13, 17) -14-9-11-8-12. A relatively rapid decrease in the current of diodes 8, 9 to zero occurs. Thus, we have a mode of resonant switching or switching valves. In the second interval of the T / 2 half-cycle, when counter-parallel diodes 8, 9 are turned on, the current of the further discharge of the compensating capacitor 13 occurs along the circuit: 13-14-9-11-8-12-13. At the same time, the compensating capacitor 13 continues to recharge through the load 17 along the circuit: 13-17-13. In the interval of simultaneous conductivity of two adjacent counter-parallel diodes 8, 9, a small reverse (negative) voltage equal to the voltage drop on the corresponding counter-parallel diode 8, 9 and controlled valves are applied to the controlled valves 4, 5 included in the next half-period T / 2 4, 5 can turn on at low switching losses. By the time the anti-parallel diodes 8, 9 are turned off, the second interval of the considered T / 2 half-cycle ends. Next, the controlled valves 4, 5 are turned on. The compensating capacitor 13 at a specified time is charged with a conditionally positive voltage polarity and is vibrationally recharged to a voltage of opposite polarity (negative potential on the left-hand side wiring diagram). From the moment the controlled gates 4, 5 are turned on, the first T / 2 half-cycle in the operation of an autonomous matched inverter with resonant switching ends. In the second half-cycle T / 2, during operation of controlled valves 4, 5 and counter-parallel diodes 7, 10, electromagnetic processes in a self-contained matched inverter with resonant switching proceed similarly, but currents through a parallel load circuit (13, 17) with an induction heater 17 at time intervals of the second half-cycle T / 2 have the opposite direction. At the end of the second half-cycle T / 2, the controlled valves 3, 6 turn on again. Next, the electromagnetic processes in the inverter (new period T of the output signal) are completely repeated. Snubber capacitors 15, 16 reduce the level of electromagnetic interference and overvoltage at the DC terminals of a single-phase inverter bridge. During their operation, the pulse voltage of electromagnetic interference is effectively shunted to the zero output of the device case.

Controlled valves 3-6 when implementing an autonomous matched inverter with quasi-resonant switching can be performed as single-operation symmetrical or without reverse blocking ability (thyristors of various types, reversibly-switched dinistors, gas-discharge valves) with artificial switching, or two-operation, that is, completely controlled by symmetric or asymmetric (lockable thyristors, transistors of various types, combination keys).

When using single-operation valves, a mode of operation with capacitive detuning of both a parallel load and an equivalent series circuit is necessary. In this case, after the next pair of gates 3, 6 or 4, 5 is naturally turned off, counter-parallel diodes 7, 10 or 8, 9 are switched on by shunting them. As you can see, the electromagnetic processes in a stand-alone matched inverter made on single-operation gates are somewhat different. In the conduction interval of the anti-parallel diodes (7-10), a small negative voltage is applied to the controlled valves (3-6), equal to the voltage drop across the anti-parallel diodes, and they restore their control properties.

A self-contained matched inverter with resonant switching using two-operation valves can also work in the capacitive detuning mode of both a parallel load and equivalent series circuit. Electromagnetic processes in a stand-alone inverter with two-stage valves in this case will be similar to electromagnetic processes in inverters made on single-stage valves.

In a self-contained matched inverter with resonant switching, it is possible to implement a dual-frequency (multi-frequency) operating mode. In the dual-frequency mode, the periodic switching of pairs of valves 3, 6 and 4, 5 is performed at a low output frequency. The load parallel oscillatory circuit (13, 17) is tuned to a high output frequency. In each half-cycle T / 2 in the dual-frequency mode, the pairs of gates 3, 6 and 4, 5 turn on repeatedly and conduct current for intervals close to half the period of the high output frequency. Two-frequency operation is required for some technological processes, such as induction surface hardening or melting of ultrapure metals.

Compared with the prototype, the reliability of the autonomous coordinated inverter with resonant switching is significantly increased. This is achieved by a comprehensive reduction in the values of the currents of controlled valves and counter-parallel diodes due to the use of parallel compensation of the reactivity of the induction heater (load), the levels of overvoltage on the controlled valves that occur when they are turned off, the levels of electromagnetic interference that occur when the controlled valves and counter-parallel diodes are turned off switching electrical losses in circuit elements due to “soft” switching of controlled gates and counter-parallel diodes and deys tv snubber capacitors, providing a symmetric limitation of the current of the inverter power source in the event of an emergency circuit of the inverter output terminals to the load housing due to filter chokes, electrical losses in the filter chokes and switching chokes. The stability and, therefore, the reliability of an autonomous matched inverter with resonant switching is increased and the likelihood of inversion failures when working on a widely varying electrotechnological load (induction heater, plasma-chemical or lighting installation), as well as failures in the inverter control system, are reduced.

The increase in the reliability of an autonomous matched resonant inverter is estimated by the time between which the device operates on failure. According to experimental studies and expert estimates, the time between failures of the claimed inverter can be increased by 50 ÷ 60%.

Compared with the prototype, in addition, the efficiency is increased (by 4-5%) of an autonomous matched inverter with resonant switching due to a decrease in switching energy losses in controlled valves and counter-parallel diodes (lowering levels of switching overvoltages, initial slew rates and slope rates current when turning on and off controlled gates and counter-parallel diodes, recovering part of the energy of the overvoltage in the load, effective compensation of reactivity load) and electrical losses in filter chokes and commutating chokes.

Additionally (in comparison with the prototype), the design of the energy (power) part of an autonomous matched inverter with resonant switching can be significantly simplified by providing the possibility of using controlled valves and anti-parallel diodes with reduced requirements for their parameters and lower price.

Additionally (compared with the prototype) can be reduced weight and size (up to 30%) of the autonomous inverter due to the implementation of filter chokes and commutating chokes with magnetic coupling and a general reduction in electrical losses.

Claims (1)

A self-contained matched inverter with resonant switching, containing a single-phase bridge connected to the input terminals of the inverter through filter inductors on controlled valves with on-parallel diodes, a filter capacitor shunted, a single-phase bridge AC output terminal connected to the inverter output terminal through a switching inductor, the inverter output terminals are bridged compensating capacitor, characterized in that the filter chokes are made magnetically coupled and included according to the second yhodnoy output single-phase alternating current bridge is connected to the second output terminal of the inverter via the second commutating reactor, commutating reactors made magnitosvjazannymi and included under a single-phase bridge bypassed series circuit of the two snubber capacitors whose common connection point is connected to the zero output device housing.