RU68806U1 - AGREED FREQUENCY CONVERTER WITH INDIRECTLY EXPRESSED DC LINK AND RESONANT COMMUNICATION - Google Patents

Abstract

The utility model relates to a conversion technique and can be used in power supplies for induction heaters and other electrotechnological loads. The utility model extends the scope of a consistent frequency converter with an implicit DC link and resonant switching. The matched frequency converter with an implicit DC link and resonant switching contains a serial circuit connected through the inductors of the filter 1, 2 to the input terminals of the frequency converter, including a filter capacitor 3, a switching inductor 4, the output terminals of the frequency converter, shunted by a compensating capacitor 5, a second switching inductor 6 and a second filter capacitor 7, shunted by a second series circuit including two controllable valves connected counterclockwise I am 8, 9 with counter-parallel diodes 10, 11. Load 12 is connected to the output terminals of the frequency converter. 1 ill.

Description

The utility model relates to a conversion technique and can be used in power supplies for induction heaters and other electrotechnological loads. The utility model extends the scope of a consistent frequency converter with an implicit DC link and resonant switching.

A known frequency converter with a pronounced DC link and resonant switching is known, comprising a direct current source and connected through a filter inductor to the output terminals of the direct current source, a series circuit including a filter capacitor, a switching inductor, output terminals of the frequency converter, shunted by a compensating capacitor, shunted controlled valve with an anti-parallel diode (Electromagnetic processes and parametric synthesis are the same high-voltage inverters with a reverse diode for electrothermy / L.E. Roginskaya, A.V. Ivanov, M.M.Mulmenko and others // Electricity. - 2003. - No. 12. - P. 42).

The disadvantage of a consistent frequency converter is its narrow scope. This is due to the high levels of electrical losses associated with double energy conversion, as well as the low reliability of the matched frequency converter due to high voltage levels across the filter capacitor. This limitation does not allow, for example, the use of a well-known consistent frequency converter for supplying critical consumers with high requirements for reliability and cost-effectiveness.

A known frequency converter with a pronounced DC link and resonant switching is known, comprising a direct current source and connected to the output terminals of the direct current source of the frequency converter, a series circuit including a compensating capacitor and output terminals of the frequency converter, shunted by a controllable valve with an anti-parallel diode , the output terminals of the DC source are shunted by the filter capacitor (A.S. 1830641 USSR, MKI N05V 6 \ 06. Device for induction heating \ S.V.Dzliev, E.M. Silkin, S.N. Tazikhin, etc. - Declaration 01.10.90, Publ. 30.07.93, B.I. No. 28).

The disadvantage of a consistent frequency converter is its narrow scope. This is due to the high levels of electrical losses associated with the double conversion of energy, as well as the low reliability of the matched frequency converter due to the high voltage levels on the controlled valve, on-parallel diode and switching capacitor. These limitations do not allow, for example, the use of a well-known consistent frequency converter for supplying critical consumers with high requirements for reliability and cost-effectiveness.

A known frequency converter with a pronounced DC link and resonant switching is known, comprising a direct current source and connected to the output terminals of the direct current source of the frequency converter, a series circuit including a compensating capacitor and output terminals of the frequency converter, shunted by a controllable valve with an anti-parallel diode (A.S. 1821945 USSR, MKI N05V 6 \ 06. Device for induction heating \ E.M. Silkin, S.V. Dzliev, S.N. Tazikhin, etc. - Declared 15.10.90, Publ. 1 5.06.93, B.I. No. 22).

The specified harmonized frequency converter is the closest in technical essence to a utility model and is selected as a prototype.

The disadvantage of the prototype is a narrow scope. This is due to the high levels of electrical losses associated with the double conversion of energy, as well as the low reliability of the matched frequency converter due to the high levels of currents and voltages on the controlled valve, anti-parallel diode and compensating capacitor. These restrictions do not allow, for example, the use of a well-known harmonized frequency converter for supplying critical consumers with high requirements for reliability and cost-effectiveness

The utility model is aimed at solving the problem of expanding the scope of a consistent frequency converter, which is the purpose of the utility model.

This goal is achieved by the fact that a consistent frequency converter with an implicit DC link and resonant switching contains a serial circuit connected to the input terminals of the frequency converter through the filter inductors, including a filter capacitor, a switching inductor, the output terminals of the frequency converter, shunted by a compensating capacitor, and a second switching a choke and a second filter capacitor, shunted by a second series circuit, including connected echno two controlled valve with anti-parallel diodes.

A significant difference characterizing the utility model is the expansion of the scope of the matched frequency converter, which is achieved by the possibility of using the matched frequency converter to power responsible consumers by reducing losses associated with double energy conversion, transferring the matched frequency converter to the direct frequency conversion mode, increasing the reliability of operation, the ability to effectively power loads remote from the power source.

Expanding the scope of a matched frequency converter with an implicit DC link and resonant switching is the obtained technical result due to new elements in the matched frequency converter circuit, the order of their inclusion and new connections, that is, the hallmarks of the utility model. Thus, the distinguishing features of the inventive consistent frequency converter with an implicit DC link and resonant switching are essential.

The figure shows a diagram of a matched frequency converter with an implicit DC link and resonant switching.

The matched frequency converter with an implicit DC link and resonant switching contains a serial circuit connected through the inductors of the filter I, 2 to the input terminals of the frequency converter, including the filter capacitor 3, the switching inductor 4, the output terminals of the frequency converter, shunted by the compensating capacitor 5, the second switching a choke 6 and a second filter capacitor 7, shunted by a second series circuit, including two controllable valves connected counterclockwise I 8, 9 with anti-parallel diodes 10, 11. The load 12 is connected to the output terminals of the frequency converter.

A matched frequency converter with an implicit DC link and resonant switching in steady state operates as follows. An alternating supply voltage of the mains frequency (linear or phase voltage of the supply network) is applied to the input terminals of the matched frequency converter. The output frequency of the matched frequency converter exceeds the line frequency. The control pulses to the controlled valve 8 are applied at the moments when the voltage across the compensating capacitor 5 passes through zero to the positive range of values (+ on the upper lining of the compensating capacitor 5) and when

the positive half wave of the AC supply voltage (+ at the top input terminal according to the scheme), and to the controlled valve 9, at the moments when the voltage across the compensating capacitor 5 passes through zero to the negative range of values (+ on the lower circuit of the compensating capacitor 4) with a negative half wave AC supply voltage (+ at the lower input output circuit). The parameters of the commutating chokes 4, 6, the capacity of the compensating capacitor 5 and the filter capacitors 3, 7 are selected from the condition for ensuring the oscillatory nature of the current in the circuit: 8 (9) - 3 - 4 - (5, 12) - 6 - 7 - 11 (10) - 8, formed when the controlled valves 1 or 9 are turned on. The natural frequency of this circuit is approximately 4 times higher than the output frequency of the device. The compensating capacitor 5 provides parallel compensation of the reactive power of the induction heater (inductor or load) 12 and sequential compensation, together with the filter capacitors 3, 7 (at the final value of their capacitance), of the reactive power of the switching reactors 4, 6. The output frequency of the device can be higher than the natural frequencies of the parallel load circuit (5, 12), if a higher output voltage of the matched frequency converter is required. Switching chokes 4, 6 can be made in the form of independent elements or represent the inductance of the load (part of the load) and (or) the connecting output busbars (cables) of the coordinated frequency converter. The full cycle (period) of the output signal of a matched frequency converter with resonant switching consists of three time intervals corresponding to various combinations of on and off state of controlled valves 8, 9 and counter-parallel diodes 10, 11. As controlled valves, they can be used as single-operation, so two-operation valves without reverse or reverse conductivity (i.e. with an anti-parallel diode). In the case of using controlled valves without reverse

the conductivity scheme of the device changes (controlled 8, 9 gates are turned on in parallel). In this case, the electromagnetic processes in the matched frequency converter circuit are qualitatively similar. The chokes of the filter 1, 2 have a sufficiently large inductance and provide a reduction in the effect of a matched frequency converter on the mains. The shape of the current consumed from the network is close to sinusoidal. Consider an embodiment of a circuit based on controlled two-operation gates (transistors) with counter-parallel diodes. Consider the operation of a consistent frequency converter with a positive half-wave of the input AC voltage. The main (first) interval corresponds to the direct conductivity interval of the controlled valve 8. When the controlled valve 8 is turned on, an oscillatory charge begins with a conditionally positive polarity (+ on the lower lining of the circuit) of the compensating capacitor 5 along the circuit: 3 - 8 - 11 - 7 - 6 - ( 5, 12) - 4 - 3, from the filter capacitors 3, 7 and the power source of the matched frequency converter. At the same time, the compensating capacitor 5 is discharged through the inductor 12 in the circuit: 5 - 12 - 5. After the oscillatory current drop in the circuit: 3 - 8 - 11 - 7 - 6 - (5, 12) - 4 - 3, to zero the compensating capacitor 5 charged to the maximum positive voltage, which exceeds the total voltage across the filter capacitors 3, 7. The discharge (second interval) of the compensating capacitor 5 begins along the circuit: (5, 12) - 6 - 7 - 9 - 10 - 3 - 4 - (5, 12). A reverse current flows through an anti-parallel diode 10 of the controlled valve 8 and the controlled valve 9. In the second interval, the control pulse is removed from the controlled valve 8. At the same time, the compensating capacitor 5 also discharges through the inductor 12 in the circuit: 5 - 12 - 5. After the oscillatory current drop in the circuit: (5, 12) - 6 - 7 - 9 - 10 - 3 - 4 - (5, 12) to zero the counter-parallel diode 10 of the controlled valve 8 and the controlled valve 9 are turned off. In this case, the voltage at the compensating capacitor 5 remains positive and its value is less than the total voltage across the filter capacitors 3, 7.

At the third time interval, the compensating capacitor 5 continues to be recharged in the circuit: 5 - 12 - 5 to a voltage of negative polarity (+ on the upper lining of the compensating capacitor 5) due to the energy stored in the electromagnetic fields of the compensating capacitor 5 and inductor 12. At the maximum negative voltage on the compensating capacitor 5 on the controlled valve 8 there is a maximum positive voltage equal to the sum of the voltages on the filter capacitors 3, 7 and the compensating condensate e 5 (about twice the supply voltage peak). The third interval in the operation of the coordinated frequency converter ends when the compensating capacitor 5 is completely discharged. When the voltage across the compensating capacitor 5 passes through zero to the positive value range, the period in the operation of the matched frequency converter ends, the next control pulse is sent again to the controlled valve 8 (if the alternating voltage mains remains positive), the controlled valve 8 is turned on and the next period begins in the operation of the matched converter pilots at. When using a two-operation controlled valve 8, the third interval is advisable to set a short duration by selecting the parameters of the circuit elements, which ensures higher energy performance of the device. On the conduction interval of the counter-parallel diode 10, a small reverse (negative) voltage equal to the voltage drop across the counter-parallel diode 10 is applied to the turned-off controlled valve 8, and the controlled valve 8 can restore its 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 single-operation controlled valve 8. When the supply voltage is negative, the electromagnetic processes in the circuit proceed similarly, but the operating order of the controlled valves 8, 9 and

counter-parallel diodes 10, 11 (the main operation interval is formed when the controlled valve 9 is turned on).

Controlled gates 8, 9 when implementing a coordinated frequency converter with an implicit DC link and resonant switching, as described above, can be performed as single-operation symmetrical or without reverse blocking ability (thyristors of various types, reversibly-switched dinistors, gas-discharge valves), and dual-operation, that is, fully controlled symmetric or asymmetric (lockable thyristors, transistors of various types, combination keys).

Compared with the prototype, the scope of application of a matched frequency converter with an implicit DC link and resonant switching is significantly expanded. This is achieved by the possibility of using a coordinated frequency converter for supplying critical consumers with increased requirements for energy performance and reliability, remote loads, by eliminating double conversion, increasing operational reliability by reducing the values of currents and voltages on controlled valves (more than twice), levels of overvoltage on controlled valves arising when they are turned off, levels of electromagnetic interference arising when turned off valves and RIVER-parallel diodes nonrigid switched controlled valves, providing a symmetric power supply the current limiting circuit of the inverter during emergency output terminals of the inverter to the load due to the throttle body of the filter. The stability of the operation of a matched frequency converter with an implicitly expressed DC link and resonant switching is increased and the likelihood of inversion failures (when performing a matched frequency converter on single-operation controlled valves) when operating over a wide range is reduced

electrotechnological load (induction heater), as well as failures in the control system of a consistent frequency converter.

Additionally (compared with the prototype), the design of the energy (power) part of the matched frequency converter can be significantly simplified and the scope 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 possibility of using single-operation gates. The matched frequency converter uses directly the AC source. A coordinated frequency converter can be used in systems with increased requirements for the influence of the valve load on the supply network.

Compared with the prototype, the efficiency of a matched frequency converter is further increased by reducing switching energy losses in controlled valves and counter-parallel diodes (lowering levels of switching overvoltages, initial slew rates and current decay rates when turning on and off controlled valves and counter-parallel diodes , recovery of part of the energy of overvoltages in the load).

Claims (1)

A matched frequency converter with an implicit DC link and resonant switching, comprising a series circuit connected through the filter inductors to the input terminals of the frequency converter, including a filter capacitor, a switching choke, output terminals of a frequency converter shunted by a compensating capacitor, a second switching choke and a second filter capacitor, shunted by a second series circuit, including two counter-actuated valves connected with track-parallel diodes.