RU104400U1 - AUTONOMOUS AGREED INVERTER WITH RESONANT COMMUTATION - Google Patents

Abstract

The invention is aimed at improving the reliability of a stand-alone matched inverter with resonant switching. The specified technical result is achieved by the fact that in a self-contained matched inverter with resonant switching, containing connected to the input terminals of the inverter through magnetically connected inductors 1, 2 of the filter, connected according to, a single-phase bridge on controlled valves 3-6 with counter-parallel diodes 7-10, conclusions DC bridge are shunted by the filter capacitor 11, the AC terminal of the bridge is shunted by a serial circuit from the resistor 12 and the capacitor 13 and connected to the output terminals of the inverter after serial circuits from switching chokes 14, saturation chokes 15 and, respectively, 16, 17, switching chokes are magnetically connected and connected according to, the output terminals of the inverter are shunted by a compensating capacitor 18. The load 19 is connected to the output terminals of the inverter. 1 ill.

Description

The utility model relates to converting technology and can be used in the design of power sources for induction heaters for various purposes and other 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, which contains a single-phase bridge connected to the input terminals of the current inverter through filter inductors on controlled gates, the bridge DC terminals are bridged with a counter diode, the bridge AC terminals are connected to the output terminals of the inverter via a switching inductor, the output terminals of the inverter are bridged with compensating capacitor (A.S. 1683150 USSR, MKI N02M 5 \ 45. Frequency converter \ Silkin EM - Decl. 03.03.89, Publ. 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 and the oncoming diode, which can lead to their 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 and the entire device can fail.

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 bridge AC pins are connected to the output terminals of the inverter via a switching choke, the output terminals of the inverter are shunted by a compensating capacitor (A S. 1742961 USSR, MKI N02M 5 \ 45. Frequency converter \ Silkin EM - Announcement 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 controlled valves and on-parallel diodes, which can lead to their failure, as well as on high levels of electromagnetic interference that occurs when off-parallel diodes are turned off, which can cause malfunctions in the inverter control system and the output of the entire device out of service.

A self-contained matched inverter with resonant switching is known, comprising comprising a single-phase bridge connected to the input terminals of the inverter through filter inductors on controlled gates with counter-parallel diodes, DC bridge terminals are shunted by the filter capacitor, the bridge AC terminals are connected to the inverter output terminals through a switching inductor , the output terminals of the inverter are shunted by a compensating capacitor (P. 61964 RF, MKI N02M 7 \ 00. Autonomous matched resonant invert or \ Silkin E.M. - Declaration of 11/13/06, Publ. 10.03.07, BIMP. 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 a stand-alone matched inverter with resonant switching is the low reliability. This is due to deficiencies in the design of switching and filter chokes, high levels of switching overvoltages on controlled valves and on-parallel diodes due to a sharp break in the current when turned off, which can cause electrical breakdown of controlled valves and on-parallel diodes, as well as high levels of electromagnetic interference , which can lead to the output of controlled gates and counter-parallel diodes malfunctioning due to overheating of the structure and malfunctions in the control system of the inverter, leading to system failure, that is, failure of the entire device as a whole.

The utility model is aimed at solving the problem of improving the reliability of an autonomous matched inverter with 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 connected to the input terminals of the inverter through magnetically coupled filter chokes, connected in accordance with a single-phase bridge on controlled gates with counter-parallel diodes, the DC terminals of the bridge are shunted by the filter capacitor, AC terminals bridges are shunted by a serial circuit of a resistor and a capacitor and connected to the output terminals of the inverter through serial circuits from the commutator boiling chokes and chokes saturation, commutating reactors magnetically and included under, the inverter output terminals are shunted compensating capacitor.

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 optimizing the design of commuting and filter chokes, by comprehensively reducing the maximum current levels of elements by reducing the total electrical losses and overvoltages on controlled valves and counter-parallel diodes, reduced levels of electromagnetic interference, with the exception of overheating modes of the structure of controlled valves and oncoming pairs allelic diodes and faults in the inverter control system.

Improving the reliability of a matched inverter with resonant switching is the technical result due to new elements in the inverter circuit, the order of their inclusion, new connections and new design solutions, that is, the hallmarks of a utility model. Thus, the distinguishing features of the claimed autonomous matched inverter with resonant switching are essential.

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

The self-contained matched inverter with resonant switching contains an inverter connected to the input terminals through magnetically coupled chokes 1, 2 of the filter, connected in accordance with one-phase bridge on controlled valves 3-6 with counter-parallel diodes 7-10, the bridge DC outputs are bridged by the filter capacitor 11, the conclusions AC bridge are shunted by a serial circuit from a resistor 12 and a capacitor 13 and connected to the output terminals of the inverter through serial circuits from switching inductors 14, inductors saturation and 15, respectively, 16, 17, commutating reactors magnetically and included under, the inverter output terminals are shunted compensating capacitor 18. The load 19 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 inductances of the chokes 1, 2 of the filter are selected sufficient for high-quality filtering of current and voltage at the input of a single-phase bridge. The implementation of the chokes 1, 2 of the filter magnetically coupled and their consonant inclusion optimize the design, reduce the total number of turns, winding resistance and electrical losses in the chokes 1, 2 and the elements of the device as a whole. The compensating capacitor 18 provides parallel compensation of the reactive power of the induction heater (load) 19 and sequential compensation of the reactive power of the switching reactors 14, 16. The switching reactors 14, 16 can be implemented as independent elements or represent the inductance of the load (part of the load) and (or) connecting discharge tires (cables). The implementation of the commutating chokes 14, 16 magnetically coupled and their consistent inclusion, similarly to the chokes 1, 2 of the filter, optimize the design, reduce the total number of turns, winding resistance and electrical losses in the chokes 14, 16 and the elements of the device as a whole. The operation of saturation chokes 15, 17 limits the rate of rise and fall of currents through gates and anti-parallel diodes and reduces switching losses in them. Reducing switching losses and overvoltages is also carried out by a series circuit of a resistor 12 and a capacitor 13, which shunts the AC inverter bridge outputs.

The full cycle (period) of the output signal of a self-contained matched inverter with resonant switching consists of two equal 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 half-period, in the general case, three different time intervals can be distinguished by the nature of electromagnetic processes (simultaneous operation of two controlled valves of a single-phase bridge, two adjacent counter-parallel diodes, as well as a pause in the operation of controlled valves and anti-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. It is advisable to set the other two intervals to short duration by selecting the parameters of the elements, which ensures high energy performance of the device. In the interval of simultaneous conductivity of two adjacent counter-parallel diodes, a small reverse (negative) voltage equal to the voltage drop across the counter-parallel diode is applied to the switched-off controlled valves, and the controlled valves can restore their control properties (using single-operation valves). In this case, the duration of the second interval is set based on the required shutdown time of the used controlled valves 3-6.

At the time of switching on (the beginning of the half-period), for example, of the controlled valves 3, 6, the voltage at the compensating capacitor 18 has a conditionally negative polarity (positive potential at the lower lining of the compensating capacitor 18). The voltage at the compensating capacitor 18 varies according to the oscillatory law. The voltage level at the compensating capacitor 18 at the moment of switching on the controlled valves 3, 6 is lower than the level of the amplitude value of this voltage. The inclusion of controlled valves 3, 6 is carried out ahead of time relative to the instant of transition of the instantaneous voltage value on the compensating capacitor 18 relative to the zero level. Current through a parallel load circuit formed by an induction heater 19 and a compensating capacitor 18 begins to flow from the filter capacitor 11 of an autonomous matched inverter with resonant switching in a circuit: 11-3-14-15- (18, 19) -17-16-6- eleven. The filter capacitor 11 has sufficient capacity for high-quality smoothing of the voltage at the input of a single-phase bridge. The filter capacitor 11 is charged from the power source of an autonomous matched inverter with resonant switching along the circuit: + -1-11-2--. The compensating capacitor 18 is discharged and vibrationally recharged to a voltage of conditionally positive polarity (positive potential on the upper lining according to the scheme). The parameters of the circuit 11-3-14-15- (18, 19) -17-16-6-11 and the lead angle 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 commutation chokes 14, 16 and the uncompensated part of the capacitance of the compensating capacitor 18. The current of the controlled valves 3, 6 first increases and then decreases according to a quasi-oscillatory law. At the moment of equal current control valves 3, 6 to zero, they turn off. At the moment of switching off the controlled gates 3, 6, the first half-period interval (simultaneous conduction of controlled gates of a single-phase bridge) ends. After turning off the controlled valves 3, 6, counter-parallel diodes 7, 10 are turned on. An oscillating discharge current of the compensating capacitor 18 occurs along the circuit: (18, 19) -15-14-7-11-10-16-17-17 - (18, 19). At the same time, the compensating capacitor 18 continues to recharge through the load 19. On the interval of simultaneous conductivity of two adjacent counter-parallel diodes 7, 10, a small reverse (negative) voltage equal to the voltage drop across the corresponding counter-parallel diode 7, 10 is applied to the switched-off controlled valves 3, 6 , and controlled valves 3, 6 can restore their control properties (when using single-operation valves). By the time the off-parallel diodes 7, 10 are turned off, the second half-period interval ends. Then, after a pause interval (the third half-period interval), leading relative to the moment when the instantaneous voltage value across the compensating capacitor 18 passes through zero, controlled valves 4, 5 are turned on. The compensating capacitor 18 is charged at a specified time with a conditionally positive voltage polarity and is recharged vibrationally to a voltage of opposite polarity (negative potential on the lower lining according to the scheme). From the moment the controlled valves 4, 5 are turned on, the first half period in the inverter operation ends. In the second half-cycle, during operation of controlled valves 4, 5 and counter-parallel diodes 8, 9, electromagnetic processes in a self-contained matched inverter with resonant switching proceed similarly, but currents through the load circuit (18, 19) with an induction heater 19 at time intervals of the second half-periods have the opposite direction. At the end of the second half-cycle, the controlled valves 3, 6 turn on again. Next, the electromagnetic processes in the inverter (a new period of the output signal) are completely repeated.

Controlled valves 3-6, when implementing an autonomous matched resonant inverter, can be either single-operation symmetrical or without reverse blocking ability (thyristors of various types, reversibly-switched dynistors, gas-discharge valves), or two-operation, that is, fully controlled symmetric or asymmetric (lockable thyristors, transistors of various types, combination keys). Two-operation valves can also be included in only two arms or in one of the groups (anode or cathode) of a single-phase inverter bridge. Moreover, in the other two shoulders or another group of the single-phase bridge, single-operation valves can be used.

The chokes 1, 2 of the filter may not be magnetically coupled, or one choke (1 or 2) of the filter may be used. Similarly, switching chokes 14, 16 may also not be magnetically coupled, and one switching choke (14 or 16) and one saturation choke (15 or 17) can be used. In the general case, the switching choke (14, 16) can have a combined design with a saturation choke (15, 17). The principle of the inverter does not change. The inventive symmetrical circuit provides increased reliability of the device. Saturation chokes 15, 17 are made, for example, in the form of closed cores of ferromagnetic material with a rectangular hysteresis loop, covering parts of the connecting (outlet) busbars or cables of the device.

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), reduction of electric losses, levels of overvoltage on controlled valves and counter-parallel diodes arising from their switching, levels of electromagnetic interference arising when turning off controlled gates and counter-parallel diodes, due to the operation of saturation chokes and a series circuit from the resistor and the capacitor, by providing a symmetrical limitation of the current of the inverter power source in the event of emergency circuits of the inverter output terminals to the load casing due to filter chokes and switching chokes. The stability of the autonomous coordinated inverter with resonant switching is increased and the likelihood of inversion failures when working on a widely varying electrotechnological load (induction heater), as well as failures in the inverter control system, is reduced.

Improving the reliability of a stand-alone matched inverter with resonant switching is estimated by the time between which the device fails. According to experimental studies and expert estimates, the MTBF of the inventive inverter can be increased by 20-25%.

Compared with the prototype, the inverter’s efficiency is also increased by reducing switching energy losses in controlled gates and counter-parallel diodes (lowering levels of switching overvoltages, initial rise and fall rates of currents when turning on and off controlled gates and counter-parallel diodes , recovery of part of the energy of overvoltages into the load) and reduction of losses in magnetically coupled chokes.

Additionally (in comparison with the prototype), the design of the energy (power) part of the inverter can be significantly simplified and the price of the device can be reduced due to the possibility of using controlled valves and counter-parallel diodes with reduced requirements for their parameters and lower price.

Claims (1)

A self-contained matched inverter with resonant switching, containing connected to the input terminals of the inverter through magnetically coupled filter chokes that are connected according to a single-phase bridge on controlled valves with counter-parallel diodes, the bridge DC outputs are bridged by the filter capacitor, the bridge AC pins are bridged by a series circuit from the resistor and capacitor and connected to the output terminals of the inverter through serial circuits from switching chokes and saturation chokes, to mutating chokes are magnetically coupled and switched on according to the inverter output terminals are shunted by a compensating capacitor.