RU68808U1 - AUTONOMOUS AGREED INVERTER WITH RESONANT COMMUTATION - Google Patents

Abstract

The utility model relates to a conversion technique and can be used in power supplies for induction heaters. The utility model improves the reliability of a stand-alone matched inverter with resonant switching. The self-contained matched inverter with resonant switching contains a single-phase bridge connected to the input terminals of the inverter through the inductors of the filter 1, 2, one diagonal of which contains controlled valves 3, 4 with counter-parallel diodes 5, 6, and the second diagonal is capacitors 7, 8. The AC terminals of the single-phase bridge are connected via switching inductors 9, 10 to the output terminals of the inverter shunted by a compensating capacitor 11. An inductor 12 is connected to the output terminals of the inverter. 1 ill.

Description

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

A self-contained matched inverter with resonant switching is known, which contains a single-phase bridge connected to the input terminals of the inverter, one diagonal of which contains a controlled valve with an anti-parallel diode and a capacitor, and a second diagonal of a second capacitor and a second controlled valve with an anti-parallel diode, conclusions AC single-phase bridge through a switching inductor and a switching capacitor connected to the output terminals of the inverter (Thyristor converters frequency / A.K.Belkin, T.P.Kostyukova, L.E.Roginskaya etc. -. M .: Energoatomizdat, 2000 - P.37).

The disadvantage of a stand-alone matched inverter with resonant switching is the low reliability. This is due to high levels of currents through controlled gates and counter-parallel diodes in the inverter, made at a given power, which can lead to their failure due to overheating of semiconductor structures of controlled valves and anti-parallel diodes. The inverter does not provide a symmetrical limitation of the current of the power source during emergency closures of the output terminals to the load housing due to filter chokes.

A self-contained matched inverter with resonant switching is known, comprising a single-phase bridge connected through a filter inductor to the input terminals of the inverter with a DC output, one diagonal of which contains controlled valves,

and the second diagonal is capacitors, AC terminals of a single-phase bridge through a switching inductor are connected to the output terminals of the inverter (P. 2016488 RF, MKI N02M 7 \ 523. Two-cell resonant inverter \ E.M. Silkin, G.V. Mizin, A.I. Pakhalin et al. - Declaration 04.07.91, Publish 15.07.94, B.I. No. 13).

The disadvantage of a stand-alone matched inverter with resonant switching is the low reliability. This is due to high levels of currents through the controlled valves in the inverter, made at a given power, which can lead to their failure due to overheating of the semiconductor structures of the controlled valves. The inverter does not provide a symmetrical limitation of the current of the power source during emergency closures of the output terminals to the load housing due to filter chokes.

A self-contained matched inverter with resonant switching is known, which contains a single-phase bridge connected through a filter inductor to the input terminals of the inverter, one diagonal of which contains controlled valves with counter-parallel diodes, and a second diagonal switching inductors and capacitors, single-phase bridge AC terminals connected to output terminals of the inverter (A.S. 1742970 USSR, MKI N02M 7 \ 523. Two-cell resonant inverter \ E.M. Silkin, S.V. Dzliev, S.N. Tazikhin et al. - Declared 17.10.90, Opu Bl. 23.06.92, B.I. No. 23),

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 high levels of currents through controlled gates and counter-parallel diodes in the inverter, made at a given power, which can lead to their failure due to overheating of semiconductor

structures of controlled gates and anti-parallel diodes. The inverter does not provide a symmetrical limitation of the current of the power source during emergency closures of the output terminals to the load housing due to filter chokes.

The utility model is aimed at solving the problem of improving the reliability of a stand-alone coordinated inverter, which is the purpose of the utility model.

This goal is achieved by the fact that the self-contained matched inverter with resonant switching contains a single-phase bridge connected to the input terminals of the inverter via filter inductors, one diagonal of which contains controlled valves with on-parallel diodes, and the second diagonal is capacitors, alternating current outputs of a single-phase bridge through switching chokes are connected to the output terminals of the inverter shunted by a 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 lowering current levels through controlled gates and anti-parallel diodes, reducing switching losses, with the exception of overheating modes of the structure of controlled valves and anti-parallel diodes, ensuring symmetrical current limitation of the inverter power source in case of emergency circuits of the output terminals to the load casing due to inductors iltra.

Improving the reliability of an autonomous matched inverter with resonant switching is a technical result due to new elements in the circuit of an autonomous matched inverter, the order in which they are turned on, and new connections, 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 resonant inverter contains a single-phase bridge connected through the inductors of the filter 1, 2 to the input terminals of the inverter with a single-phase bridge, one diagonal of which contains controlled valves 3, 4 with counter-parallel diodes 5, 6, and the second diagonal is capacitors 7, 8. The findings are variable the current of a single-phase bridge through switching inductors 9, 10 are connected to the output terminals of the inverter, shunted by a compensating capacitor 11. An inductor 12 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, 4 are supplied alternately at the moments when the voltage across the compensating capacitor 11 passes through zero. The parameters of the commutating chokes 9, 10, the capacity of the compensating capacitor 11 and the capacitors 7, 8 are selected from the condition for ensuring the oscillatory nature of the current in the circuits: 8-3-9- (11, 12) -10-8 and 7-9- (11, 12 ) -10-4-7, formed when the controlled valves 3, 4 and counter-parallel diodes 5, 6 are turned on. The natural frequency of the circuits is approximately 2 times higher than the output frequency of the device. For the full cycle of operation of controlled valves 3, 4 and counter-parallel diodes 5, 6 in the load, we obtain two periods of output alternating voltage. The inductance values of the filter chokes 1, 2 are selected sufficient for high-quality filtering of the current at the input of a single-phase bridge containing controlled valves 3, 4 with counter-parallel diodes 5, 6 in one diagonal, and capacitors 7, 8 in the other diagonal. Compensating capacitor 11 provides parallel compensation of the reactive power of the induction heater (inductor or load) 12 and sequential compensation, together with capacitors 7, 8 (at the final value of their capacitance), of the reactive power of the switching throttle 9 th, 10 Commuting

Inductors 9, 10 can be made in the form of independent elements or represent inductance of the load (part of the load) and (or) connecting discharge buses (cables). The output signal period of a self-contained matched inverter with resonant switching consists of three time intervals corresponding to various combinations of on and off state of controlled valves 3, 4 and counter-parallel diodes 5, 6. As single-operation or two-operation valves with reverse conductivity (with anti-parallel diodes) or without reverse conductivity. In this case, the electromagnetic processes in the circuit of an autonomous matched inverter with resonant switching are qualitatively similar. Consider an embodiment of a circuit based on controlled two-operation gates (transistors) with counter-parallel diodes. The main (first) interval corresponds to the direct conductivity interval of the controlled valve 3 (4). When the controlled valve 3 is turned on, an oscillatory charge begins with the positive polarity of the compensating capacitor 11 along the circuit: 8-3-9- (11, 12) -10-8 from the capacitor 8 and the power source of an autonomous matched inverter. At the same time, the discharge of the compensating capacitor 11 occurs through the inductor 12 in the circuit: 11-12-11. After the oscillatory decrease in current in the circuit: 8-3-9- (11, 12) -10-8 to zero, the compensating capacitor 11 is charged to the maximum positive voltage that exceeds the voltage on the capacitor 8. The discharge (second interval) of the compensating capacitor 11 begins chains: (11, 12) -9-5-8-10- (11, 12). A reverse current flows through an anti-parallel diode 5 of the controlled valve 3, which is added to the constant charge current of the capacitor 8. The total current flows through the load circuit 11, 12 in the opposite direction. In the second interval, the control pulse is removed from the controlled valve 3. At the same time, the compensating capacitor 11 is also discharged through the inductor 12 in the circuit: 11-12-11. After the oscillatory current drop in the circuit: (11, 12) -9-5-8-10- (11, 12)

to zero, the anti-parallel diode 5 of the controlled valve 3 is turned off. In this case, the voltage across the compensating capacitor 11 becomes negative. At the third time interval of a pause, the compensating capacitor 11 continues to recharge in the circuit: 11-12-11 to a voltage of positive polarity (+ on the right-hand side according to the circuit diagram). The third interval in the operation of the self-contained matched inverter ends when the compensating capacitor P is completely discharged. At the moment the voltage across the compensating capacitor 11 passes through zero to the positive value range, the period in the autonomous matched inverter runs out, the next control pulse is applied, the controlled valve 4 is turned on and the next period begins in the work of an autonomous matched inverter. Electromagnetic processes during operation of the controlled valve 4 and the counter-parallel diode 6 are completely similar to those considered. When using dual-operation controlled valves 3, 4, it is advisable to set the second interval of short duration by choosing the parameters of the circuit elements, which ensures higher energy performance of the device. In the conduction intervals of counter-parallel diodes 5, 6, a small reverse (negative) voltage equal to the voltage drop across the counter-parallel diode 5, 6 is applied to the switched-off controlled valves 3, 4, and the controlled valves 3, 4 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 single-operation controlled valves 3, 4.

Controlled gates 3, 4 when implementing a self-contained matched inverter with resonant switching, as described above, can be performed as single-operation symmetrical or not having inverse blocking ability (thyristors of various types, reversibly-switched dynistors, gas-discharge valves), and two-operation, i.e. fully controllable symmetric or asymmetrical

(lockable thyristors, transistors of various types, combination keys).

In the circuit, the control of the output electrical parameters (power, current, voltage) can be ensured by changing the phase shift between the moments of turning on the controlled valves 3, 4 from 180 ° to 0. In this case, the output parameter increases and becomes maximum at a zero shift between the moments of turning on of the controlled valves 3, 4. Regulation is carried out by changing the wave impedance of the equivalent switching circuit when changing the phase shift between the moments of switching on the controlled valves 3, 4.

Compared with the prototype, the reliability of the autonomous coordinated inverter with resonant switching is significantly increased. This is achieved by reducing the magnitude of the currents through the controlled valves (more than twice) by changing the compensation scheme, 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, providing a symmetrical limitation 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.

Improving the reliability of a stand-alone coordinated inverter with resonant switching is estimated by the mean time between failures of the device. According to experimental studies and expert estimates, the mean time between failures of the claimed inverter can be increased by 20-30%.

Compared with the prototype, the inverter’s efficiency is further 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 anti-parallel diodes.

Additionally (in comparison with the prototype), the design of the energy (power) part of the inverter can be significantly simplified and the scope of application can be expanded by providing the possibility of using controlled valves and counter-parallel diodes with reduced requirements for their parameters and lower price, the ability to control the output electrical parameters in a wide range due to phase changes between the moments of the inclusion of controlled valves.

Claims (1)

A self-contained matched inverter with resonant switching, comprising a single-phase bridge connected through a filter choke to the input terminals of the inverter, one diagonal of which contains controlled valves with counter-parallel diodes, and the second diagonal contains capacitors, the single-phase bridge ac terminals are connected via commutating chokes to inverter output pins shunted by a compensating capacitor.