RU2449459C1 - Stand-alone matched inverter with resonant commutation - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: in the stand-alone matched inverter with resonant commutation containing connected to input pins of inverter via saturated-core reactors (1, 2) and magnetically coupled reactance coils (3, 4) of filter which are connected accordantly, one phase bridge on controlled gates (5-8) with opposite-parallel diodes (9-12), which gates are shunted by serial circuits consisting of capacitor (13-16) and resistor (17-20), direct current pins of bridge are shunted by filter capacitor (21) series circuit of two damping capacitors (22, 23) common point of which is connected to inverter body pin via damping resistor (24), alternating current pins of bridge are shunted by series circuit of protective capacitor (25) and protective resistor (26) and connected with output pins of inverter via series circuits of commutating inductors (27, 28) and limiting saturated-core reactors (29, 30), commutating inductors are magnetically coupled and connected accordantly, output pins of inverter are shunted by compensating capacitor (31). Load (3 2) is connected to output pins of inverter.

EFFECT: enlarging the application area of stand-alone matched inverter with resonant commutation.

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Description

The invention relates to a conversion technique and can be used in the design of a new generation of power supplies for induction heaters for various purposes and other electrotechnological loads. The invention extends the scope of a self-contained 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 outputs are bridged with a counter diode, the bridge AC pins are connected to the output terminals of the inverter via a switching inductor, the output terminals of the inverter are bridged by compensating capacitor (A.S. 1683150 USSR, MKI H02M 5/45. Frequency converter / Silkin EM - Application. 03.03.89. Publish. 07.10.91. BI No. 37).

The disadvantage of a stand-alone current inverter with quasi-resonant switching is its limited scope. This is due to the narrow range of regulation of the output electrical parameters, low reliability, high levels of overvoltage on the controlled valves and the counter diode and the rate of change of the currents of the controlled valves, which can lead to their failure, as well as high levels of electromagnetic interference that occur when the counter diode is turned off , which can cause malfunctions in the control system of the inverter and the failure of the entire device.

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 H02M 5/45. Frequency converter / Silkin EM - Declaration 02.08.89. Publish. 23.06.92. BI No. 23).

The disadvantage of a stand-alone current inverter with quasi-resonant switching is its limited scope. This is due to the narrow range of regulation of the output electrical parameters, low reliability, high levels of overvoltage on controlled valves and anti-parallel diodes, which can lead to failure, as well as high levels of electromagnetic interference that occur when the anti-parallel diodes are turned off, which may cause malfunctions in the control system of the inverter and the failure of the entire device.

A self-contained matched inverter with resonant switching is known, which contains a single-phase bridge connected to the input terminals of the inverter through filter inductors on controlled gates with counter-parallel diodes, the bridge DC outputs are shunted by the filter capacitor, the bridge AC terminals are connected to the output terminals of the inverter via a switching inductor, output the inverter leads are shunted by a compensating capacitor (Pat. 61964 RF, MKI H02M 7/00. Autonomous matched resonant inverter / Silkin EM - Application. 13.11.06. Publish. 03.10.07. BIPM No. 7).

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

The disadvantage of a self-contained matched inverter with resonant switching is the limited scope. This is due to the narrow range of control of the output electrical parameters, low reliability, design flaws of switching and filter chokes, high levels of switching overvoltages on controlled valves and counter-parallel diodes due to a sharp break in current during shutdown, which can cause an electrical breakdown of controlled valves and anti-parallel diodes, as well as high levels of electromagnetic interference, which can lead to the output of controlled gates and anti-parallel diodes fail due to overheating of the structure and malfunctions in the control system of the inverter, leading to a system failure, that is, failure of the entire device as a whole.

The invention is aimed at solving the problem of expanding the scope of an autonomous matched inverter with resonant switching, which is a necessary technical result and the purpose of the invention.

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 saturation chokes and magnetically coupled filter chokes, connected according to a single-phase bridge on controlled gates with counter-parallel diodes, shunted by series circuits from a capacitor and a resistor, the bridge DC outputs are bridged by the filter capacitor and a series circuit of two damping capacitors, the common connection point of which connected to the output of the inverter housing through a damping resistor, the bridge AC terminals are shunted by a serial circuit from a protective resistor and a protective capacitor and connected to the output terminals of the inverter via serial circuits from switching inductors and saturation limiting inductors, the switching inductors are magnetically connected and connected according to the inverter output terminals are bridged compensating capacitor.

A significant difference characterizing the invention is the expansion of the field of application of a self-contained matched inverter with resonant switching, which is achieved by expanding the range of effective control of the output electrical parameters, increasing the reliability of operation, optimizing the design of switching and filter chokes, comprehensively reducing the maximum current levels of elements by reducing the total electric losses and overvoltages on controlled gates and counter-parallel diodes, reducing the level of electromagnetic interference, with the exception of overheating modes of the structure of controlled gates and counter-parallel diodes and failures in the control system of the inverter. A new standalone matched inverter can be used for demanding applications.

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 distinguishing features of the invention. Thus, the distinguishing features of the claimed autonomous matched inverter with resonant switching are essential.

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

The self-contained matched inverter with resonant switching contains an inverter connected to the input terminals through saturation chokes 1, 2 and magnetically coupled chokes 3, 4 of the filter, connected in accordance with one-phase bridge on controlled valves 5-8 with counter-parallel diodes 9-12, shunted by serial circuits from capacitor 13-16 and resistor 17-20, the DC terminals of the bridge are shunted by the filter capacitor 21 and a series circuit of two damper capacitors 22, 23, the common connection point of which is connected to the pin at the inverter housing through the damper resistor 24, the bridge's AC terminals are shunted by a serial circuit from a protective capacitor 25 and a protective resistor 26 and connected to the inverter output terminals via serial circuits from switching inductors 27, 28 and saturation limiting inductors 29, 30, the switching inductors are magnetically connected and included according to, the output terminals of the inverter are shunted by a compensating capacitor 31. The load 32 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 5, 8 and 6, 7 arrive alternately with a frequency equal to the frequency of the output signal of the inverter. The inductance values of the chokes 3, 4 of the filter are selected sufficient for high-quality filtering of current and voltage at the input of a single-phase bridge. In light load conditions and when regulating the output electrical parameters, the inductance of saturation chokes 1, 2 increases, which improves their filtering properties and prevents possible interruption of the inverter input current. The implementation of the chokes 3, 4 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 3, 4 and the elements of the device as a whole. The compensating capacitor 31 provides parallel compensation of the reactive power of the induction heater (load) 32 and sequential compensation of the reactive power of the switching reactors 27, 28. The switching reactors 27, 28 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 commutating reactors 27, 28 magnetically coupled and their consonant inclusion (option of independent elements) similarly to filter reactors 3, 4 optimize designs, reduce the total number of turns, winding resistance and electrical losses in reactors 27, 28 and the elements of the device as a whole. The operation of saturation chokes 29, 30 limits the rate of rise and fall of currents through valves 5-8 and counter-parallel diodes 9-12 and reduces switching losses in them. Reducing switching losses and overvoltages is also carried out by a series circuit from a protective capacitor 25 and a protective resistor 26, which shunts the AC inverter bridge outputs. In addition, switching losses and overvoltages are limited by series circuits from a capacitor 13-16 and a resistor 17-20, connected in parallel to controlled valves 5-8 and counter-parallel diodes 9-12, and a series circuit from two damping capacitors 22, 23, a common point the connections of which are connected to the output of the inverter body through the damper resistor 24. The assembly of elements 22-24 effectively protects the inverter control system from electromagnetic interference, which increases the reliability of the device.

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 5-8 and anti-parallel diodes 9-12. 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 (5, 8 or 6, 7) of a single-phase bridge, two adjacent counter-parallel diodes (9, 12 or 10, 11), as well as pauses in the operation of controlled valves (5-8) and counter-parallel diodes (9-12). The main interval corresponds to the interval of simultaneous conductivity of two controlled valves of a single-phase bridge 5, 8 or 6, 7. It is advisable to set the other two intervals to short On the interval of simultaneous conductivity of two adjacent counter-parallel diodes (9, 12 or 10, 11), a small reverse (negative) is applied to the switched-off controlled valves (5, 8 or 6, 7) on the interval of simultaneous conductivity. voltage equal to the voltage drop across the anti-parallel diode (9-12), and controlled valves (5-8) can restore their control properties (when 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 5-8.

At the time of switching on (the beginning of the half-cycle), for example, of the controlled valves 5, 8, the voltage at the compensating capacitor 31 has a conditionally negative polarity (positive potential at the lower lining of the compensating capacitor 31). The voltage at the compensating capacitor 31 varies according to the oscillatory law. The voltage level at the compensating capacitor 31 at the moment of switching on the controlled valves 5, 8 is lower than the level of the amplitude value of this voltage. The inclusion of controlled valves 5, 8 is carried out ahead of time relative to the instant of transition of the instantaneous voltage value at the compensating capacitor 31 relative to the zero level. Current through a parallel load circuit formed by an induction heater 32 and a compensating capacitor 31 begins to flow from the filter capacitor 21 of a self-contained matched inverter with resonant switching in a circuit: 21-5-27-29- (31, 32) -30-28-8- 21. The filter capacitor 21 has sufficient capacity for high-quality smoothing of the voltage at the input of a single-phase bridge. The filter capacitor 21 is charged from the power supply of an autonomous matched inverter with resonant switching along the circuit: “+” - 1-3-21-4-2 - “-”. The compensating capacitor 31 is discharged and vibrationally recharged to a voltage of conditionally positive polarity (positive potential on the top plate according to the circuit). Circuit parameters: 21-5-27-29- (31, 32) -30-28-8-21 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 commutating chokes 27, 28 and the uncompensated part of the capacitance of the compensating capacitor 31. The current of the controlled valves 5, 8 first increases and then decreases according to a quasi-oscillatory law. At the moment of equal current control valves 5, 8 to zero, they turn off. At the moment of switching off the controlled valves 5, 8, the first half-period interval (simultaneous conductivity of the controlled valves of a single-phase bridge) ends. After turning off the controlled valves 5, 8, counter-parallel diodes 9, 12 are turned on. An oscillating discharge current of the compensating capacitor 31 occurs along the circuit: (31, 32) -29-27-9-21-12-28-30- (31, 32 ) At the same time, the compensating capacitor 31 continues to recharge through the load 32. In the interval of simultaneous conductivity of two adjacent counter-parallel diodes 9, 12, a small reverse (negative) voltage equal to the voltage drop across the corresponding counter-parallel diode 9, 12 is applied to the switched-off controlled valves 5, 8 , and controlled valves 5, 8 can restore their control properties (when using single-operation valves). By the time the anti-parallel diodes 9, 12 are turned off, the second half-period interval ends. Then, after a pause interval (the third half-period interval), leading relative to the moment the instantaneous voltage value across the compensating capacitor 31 passes through zero, the controlled valves 6, 7 are turned on. The compensating capacitor 31 is charged at a specified time with a conditionally positive polarity (positive potential on the lower circuit capacitor 31) voltage and vibrationally recharges to a voltage of opposite polarity (negative potential at the bottom of the circuit of the capacitor 31). From the moment the controlled valves 6, 7 are turned on, the first half-cycle in the operation of the inverter ends. In the second half-cycle, when controlled gates 6, 7 and counter-parallel diodes 10, 11 work, electromagnetic processes in a self-contained matched inverter with resonant switching proceed similarly, but the currents through the load circuit (31, 32) with induction heater 32 at time intervals of the second half-cycle have opposite direction. At the end of the second half-cycle, the controlled valves 5, 8 turn on again. Next, the electromagnetic processes in the inverter (a new period of the output signal) are completely repeated.

When controlled by an autonomous matched resonant inverter, controlled valves 5–8 can be implemented as either single-operation symmetrical or without reverse blocking ability (thyristors of various types, reversibly-switched dynistors, gas-discharge valves), and 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 3, 4 of the filter may not have magnetic coupling, or one choke (3 or 4) of the filter and one saturation choke (1 or 2) can be used. Similarly, switching chokes 27, 28 may also not be magnetically coupled, and one switching choke (27 or 28) and one saturation limit choke (29 or 30) can be used. In the general case, the switching reactor (27, 28) can have a combined design with a saturation restriction reactor (29, 30). The chokes 3, 4 of the filter and saturation 1, 2 can have a similar design. The principle of the inverter does not change. The inventive symmetrical circuit provides increased reliability of the device. The saturation restriction chokes 29, 30 are performed, 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. Saturation chokes 1, 2 are implemented by performing the core (s) of filter chokes 3, 4 with a variable cross section or by using magnetic materials in the core (s) with different saturation induction.

Compared with the prototype, the scope of application of an autonomous matched inverter with resonant switching is significantly expanded. The inverter can be effectively used in critical electrical technology. This is achieved by a comprehensive reduction in the values of the currents of controlled gates and counter-parallel diodes due to the use of parallel compensation of the reactivity of the induction heater (load), reduction of electric losses, surge levels on controlled valves and counter-parallel diodes arising from their switching, levels of electromagnetic interference arising when turning off the controlled valves and counter-parallel diodes, due to the operation of saturation chokes and series circuits from the resistor and capacitor, providing a symmetrical limitation of the current of the inverter power source in case of emergency circuits of the inverter output terminals to the load casing due to filter chokes and commuting 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. The range of regulation of the inverter and the range of possible loads are expanding. Significantly increases the noise immunity of the inverter control system. The reliability of the new autonomous matched inverter with resonant switching increases.

Improving the reliability of a stand-alone matched inverter with resonant switching is estimated by the time between which the device fails. In accordance with experimental studies and expert estimates, the MTBF of the inventive inverter can be increased by 25-30%. Improving the reliability of operation, as noted, expands the scope of the inverter and allows you to use it in critical applications.

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. It also expands the scope of the inverter.

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

Claims (1)

A self-contained matched inverter with resonant switching, containing connected to the input terminals of the inverter through saturation chokes and magnetically coupled filter chokes, connected in accordance with a single-phase bridge on controlled gates with counter-parallel diodes, shunted by series circuits from a capacitor and a resistor, the bridge DC outputs are shunted by the filter capacitor and a series circuit of two damping capacitors, the common connection point of which is connected to the output of the inverter housing through resistor damper, AC terminals of the bridge are shunted series circuit of a resistor and a protective guard and a capacitor connected to the output terminals of the inverter through the series circuit of switch chokes and chokes restrictive saturation, commutating reactors magnetically and included under, the inverter output terminals are shunted compensating capacitor.