CN115694203A - Direct-current isolated converter capable of bidirectional conversion and control method thereof - Google Patents
Direct-current isolated converter capable of bidirectional conversion and control method thereof Download PDFInfo
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Abstract
The application relates to a direct current isolated converter capable of bidirectional conversion and a control method thereof, wherein the direct current isolated converter comprises an energy storage follow current unit, a high-frequency conversion unit, a high-frequency isolation and transformation unit and a rectification and filtering unit; the energy storage follow current unit comprises a second capacitor and a follow current inductor, and the high-frequency conversion unit comprises first to fifth switching tubes and an absorption filter capacitor; the energy storage follow current unit is connected with the first direct current source, the input end of the high-frequency conversion unit is connected with the energy storage follow current unit, the input end of the high-frequency isolation and transformation unit is connected with the output end of the high-frequency conversion unit, the output end of the high-frequency isolation and transformation unit is connected with the input end of the rectification and filtering unit, and the output end of the rectification and filtering unit is connected with the second direct current source. The invention can realize the high-efficiency conversion of the soft switch, can be relatively simple and can meet the bidirectional conversion of wide-range voltage so as to meet the wider range of a direct current end in a practical use scene, and is simple and high-efficiency to realize.
Description
Technical Field
The application relates to the technical field of power electronics and the field of battery equipment, in particular to a bidirectional-conversion direct-current isolated converter and a control method thereof.
Background
With the utilization of current renewable energy and the requirements of 'carbon peak reaching', 'carbon neutralization' and the like, the rapid development of energy storage products and related fields of battery equipment has brought about a plurality of application scenes related to battery energy storage, such as charging pile, household energy storage, commercial energy storage and the like, and the requirements of power supply products capable of performing bidirectional transformation are more and more. Because the natural wide voltage range characteristic of the battery and the compatibility of different products are considered, the corresponding voltage range is wider and wider, so that the conventional converter which adopts two sets of circuits, namely a set of charging circuit and a set of discharging circuit to realize bidirectional conversion does not have cost advantage, and meanwhile, the common single-stage circuit is insufficient in efficiency and charging or discharging meeting the wide voltage range.
As shown in fig. 1, the conversion circuit currently used as a low-voltage battery pack usually adopts two stages, which are usually implemented by a one-stage boosting or voltage-reducing scheme and a one-stage DC/DC voltage-stabilizing conversion, the two-stage scheme has high cost, and the efficiency is reduced due to the two-stage conversion. The principle seems to be simple and direct, but higher stress of a switching tube can be caused due to the change of the high turn ratio, the inductance and leakage inductance parameters of the original main transformer can be changed, new current loop interference is introduced, and another series of parameter changes in control can be brought by sudden change of the voltage, and the problem of oscillation and the like can be easily caused by step duty ratio adjustment. In addition, the realizability of the two converters under the soft switching coordination condition is relatively poor; because a conversion circuit and a transformer must be additionally added, the whole converter is complex and difficult to popularize and apply. In the prior art, a traditional one-stage voltage reduction method is adopted, and the defects that the duty ratio range is wide due to the requirement of wide-range voltage regulation, the circuit is difficult to realize soft switching, and the efficiency is low are caused.
Disclosure of Invention
The invention aims to provide a direct current isolated converter capable of bidirectional conversion and a control method thereof, which can realize the high-efficiency conversion of a soft switch, can be relatively simple and can meet the bidirectional conversion of wide-range voltage so as to meet the wide range of a direct current end in a practical use scene, and is simple and high-efficiency to realize; the technical problems that the direct current wide range cannot be met or the two-stage converter is required to perform boost-buck conversion for multiple times, so that the loss is large, the conversion is complex, and the direct current wide range converter is not suitable for being applied in places with limited size or relatively high cost requirements in the prior art are solved.
The invention adopts a technical scheme that: a direct current isolation type converter capable of bidirectional conversion is used between two direct current power supplies and comprises an energy storage follow current unit, a high-frequency conversion unit, a high-frequency isolation and transformation unit and a rectification filtering unit; the high-frequency conversion unit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube and an absorption filter capacitor; two ends of the second capacitor are connected with the first direct current source, one end of the follow current inductor is connected with the first direct current source, and the other end of the follow current inductor is connected with the input end of the high-frequency conversion unit; the drain electrode of the first switching tube is connected with the source electrode of the fifth switching tube, the source electrode of the first switching tube is connected with the drain electrode of the third switching tube, the drain electrode of the second switching tube is connected with the drain electrode of the fifth switching tube, the source electrode of the second switching tube is connected with the drain electrode of the fourth switching tube, the source electrode of the fourth switching tube is connected with the source electrode of the third switching tube, and the drain electrode of the first switching tube and the source electrode of the third switching tube form two input ends of the high-frequency conversion unit; the source electrode of the first switch tube and the source electrode of the second switch tube form two output ends of the high-frequency conversion unit, one end of the absorption filter capacitor is connected with the drain electrode of the second switch tube, and the other end of the absorption filter capacitor is connected with the source electrode of the fourth switch tube; the input end of the high-frequency isolation and transformation unit is connected with the output end of the high-frequency conversion unit, the output end of the high-frequency isolation and transformation unit is connected with the input end of the rectification filter unit, and the output end of the rectification filter unit is connected with the second direct current source.
Furthermore, the high-frequency isolation and transformation unit is a high-frequency isolation transformer directly connected with the output end of the high-frequency conversion unit or a high-frequency isolation transformer of which the original side is connected in series with a high-frequency isolation capacitor or connected in series with a resonance inductor and a resonance capacitor, and the secondary side of the high-frequency isolation transformer is a single winding or a plurality of windings.
Furthermore, the rectification filter unit comprises a high-frequency rectification circuit and a direct-current filter capacitor, the high-frequency rectification circuit is a full-bridge rectification circuit, a full-wave rectification circuit or a voltage doubling rectification circuit, and the input end of the high-frequency rectification circuit is directly connected with the secondary side of the high-frequency isolation transformer or is connected with the secondary side of the high-frequency isolation transformer after being connected with the high-frequency isolation capacitor or the resonance inductor and the resonance capacitor in series; the output end of the high-frequency rectification circuit is connected with a direct-current filter capacitor, and the direct-current filter capacitor is further connected with a second direct-current source.
Furthermore, the high-frequency conversion unit has a rectification mode and an inversion mode; in a rectification mode, the first switch tube and the third switch tube are used as a high-frequency conversion switch tube and a boosting tube, the two switch tubes form a composite functional bridge arm, the fifth switch tube is used as a boosting freewheeling diode and also used as a reverse voltage reduction conducting connecting wire, and the first switch tube to the fifth switch tube are made into different pulse conducting combinations according to drive control to realize boosting and high-frequency conversion; in an inversion mode, the first switching tube to the fourth switching tube play a role in high-frequency rectification, are equivalent to a high-frequency rectifier diode, the fifth switching tube is used as a voltage reduction switch and can be conducted in a pulse mode or a direct mode, and the first switching tube and the third switching tube are matched with the fifth switching tube to be used as a freewheeling diode, so that direct-current reverse voltage reduction output or direct output is realized; the third switch tube and the fourth switch tube are commonly used as boosting tubes and are in pulse conduction according to driving control, and direct-current reverse boosting energy storage output is achieved.
Furthermore, the energy storage inductor is two follow current inductors in series connection or an equivalent inductor after the two follow current inductors are equivalent, and the inductance value of the equivalent inductor is the sum of the inductance values of the two follow current inductors; when the energy storage inductor is two follow current inductors which are in series connection, one end of the first follow current inductor is connected with the positive output end of the first direct current source, the other end of the first follow current inductor is connected with the drain electrode of the first switch tube and the source electrode of the fifth switch tube, one end of the second follow current inductor is connected with the negative output end of the first direct current source, and the other end of the second follow current inductor is connected with the source electrodes of the third switch tube and the fourth switch tube; when the energy storage inductor is an equivalent inductor formed by equivalence of two follow current inductors, one end of the equivalent inductor is connected with one output end of the first direct current source, the other end of the equivalent inductor is connected with one input end of the high-frequency conversion unit, and the other input end of the high-frequency conversion unit is connected with the other output end of the first direct current source through a lead.
Further, the first to fifth switching tubes are high-frequency switching tubes provided with anti-parallel diodes, or equivalent high-frequency switching tubes with the same function; the anti-parallel diode is an integrated diode, a parasitic diode or an additional diode; the absorption filter capacitor is a high-frequency non-polar capacitor or a high-frequency polar capacitor; when the absorption filter capacitor is a high-frequency polar capacitor, the anode of the absorption filter capacitor is connected with the drain electrode of the fifth switch tube, and the cathode of the absorption filter capacitor is connected with the source electrode of the fourth switch tube.
The other technical scheme adopted by the invention is as follows: a control method of a bidirectional-conversion DC isolated converter is used for controlling the bidirectional-conversion DC isolated converter in the technical scheme, and comprises the following steps:
s100: selecting a working mode, wherein the working mode comprises a rectification mode and an inversion mode, the rectification mode is input from a first direct current source end, the second direct current source end outputs, the inversion mode is input from a second direct current source end, and the first direct current source end outputs;
s200: according to the selected working mode, applying no driving signal or only a synchronous rectification driving signal to a switching tube which works as a diode or a follow current tube in the direct current isolation type converter, applying a high-level direct driving signal to the switching tube which needs to work in direct current, and applying no driving signal or a low-level non-conducting signal to the switching tube which does not need to be conducted;
s300: if the working mode is a rectification mode, converting the voltage instantaneous value of the current first direct current source, the output voltage setting and the transformation ratio to the primary side of the high-frequency isolation and transformation unit, judging whether the direct current isolation type converter needs to carry out voltage reduction or voltage boosting, determining whether to carry out voltage boosting PWM (pulse width modulation) drive control on a switching tube used as a voltage boosting tube in a composite bridge arm of the high-frequency conversion unit, and simultaneously determining whether to carry out PWM drive conduction on other switching tubes; if boosting is needed, common driving needs to be applied to the first switching tube and the third switching tube to form boosting, and the second switching tube and the fourth switching tube are matched to correspond to high-frequency conversion of the bridge pair tubes; if voltage reduction or voltage boosting is not needed, normal bridge type driving needs to be applied to the first switching tube to the fourth switching tube to carry out high-frequency conversion; the fifth switching tube is closed when the direct current isolated converter is boosted or closed in a non-conduction interval when the direct current isolated converter is reduced in voltage, and is opened when the bridge type high-frequency conversion is conducted;
s400: if the working mode is the inversion mode, converting the voltage instantaneous value of the current second direct current source and the transformation ratio to the first direct current source end, comparing the output voltage setting, judging whether the direct current isolated converter needs to carry out voltage reduction or voltage increase, and determining whether the voltage reduction PWM driving control is carried out on a fifth switching tube and a composite bridge arm of the high-frequency conversion unit; meanwhile, whether a switching tube of a high-frequency rectification circuit in the rectification filter unit is conducted in a PWM driving mode or not is determined; if boosting is needed, common driving needs to be applied to the third switching tube and the fourth switching tube to form boosting energy storage; if voltage reduction or voltage increase is not needed, normal bridge type driving is applied to a switching tube of a high-frequency rectifying circuit in the rectifying filter unit to carry out high-frequency conversion; the fifth switching tube is closed in a composite bridge arm follow current or voltage reduction rectification non-conduction interval and is conducted in a bridge rectification conduction or voltage boosting energy storage interval.
Further, in steps S300 to S400, in the rectification mode, a driving signal for short-circuiting a coil of the high-frequency isolation transformer is applied to a switching tube of the high-frequency rectification circuit in the rectification filtering unit, so that the dc isolation type converter enters a boost energy storage state; in an inversion mode, a drive signal with a variable duty ratio is applied to the high-frequency rectification circuit and the fifth switching tube, so that the direct-current isolation type converter can realize the voltage reduction regulation of the output voltage.
Further, in steps S300 to S400, when the fifth switching tube is in the PWM operating state, the PWM switching frequency of the fifth switching tube is identical to or doubled with the PWM switching frequency of the switching tube of the high frequency converting unit or the high frequency rectifying circuit.
Further, in steps S300 to S400, in the step-down rectification mode, a first switching tube and a fourth switching tube as a pair tube, and a second switching tube and a third switching tube in the high-frequency conversion unit are respectively applied with PWM driving signals that are centrosymmetric, and a fifth switching tube is applied with a PWM driving signal that is correspondingly integrated with a conduction interval of an oblique pair tube composed of the first switching tube and the fourth switching tube; under the voltage reduction inversion mode, centrosymmetric PWM driving signals are respectively applied to bridge type geminate transistors or single transistors which are inverted in the high-frequency rectifying circuit, and PWM driving signals which are correspondingly integrated with a conduction interval of an inclined geminate transistor formed by the first switching tube and the fourth switching tube are applied to a fifth switching tube in the high-frequency conversion unit.
The invention has the beneficial effects that:
(1) From the structure and performance, the complexity of the traditional multi-stage circuit conversion is overcome, so that the loss of a direct current converter power device at the rear end is reduced, the limitation is reduced, and the design margin is larger;
(2) In terms of control, the voltage control mode that the traditional series resonance conversion needs wide-range frequency modulation is changed, the voltage regulation is realized by regulating the duty ratio of each switching tube, and the control mode is simpler;
(3) The direct-current isolated bidirectional conversion circuit can realize direct-current isolated bidirectional conversion, can reduce voltage and boost voltage, is simpler compared with the traditional bidirectional conversion circuit, and has wider applicable voltage range;
(4) The invention avoids the combination switching of a plurality of converters or transformer coils due to the structural normalization control, so that the performance is more stable and the comprehensive performance-price ratio is high.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a conventional dc bidirectional isolated converter;
FIG. 2 is a schematic structural diagram of an embodiment of the present invention;
FIG. 3 is a schematic circuit diagram of embodiment 1;
FIG. 4 is a schematic view showing a state of use of embodiment 1 in a rectification mode;
FIG. 5 is an equivalent diagram of the embodiment 1 in the step-down rectification mode;
FIG. 6 is an equivalent diagram of embodiment 1 in boost rectification mode;
FIG. 7 is a schematic view showing the driving of embodiment 1 in the boost rectifying mode;
FIG. 8 is a schematic view showing the operation state of embodiment 1 in the inverter mode;
FIG. 9 is an equivalent diagram of the inverter mode with boost in the embodiment 1;
FIG. 10 is an equivalent diagram of the inverter mode under step-down in accordance with embodiment 1;
fig. 11 is a driving diagram of embodiment 1 in the step-down inversion mode.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and thus the present invention is not limited to the specific embodiments disclosed below.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this application belongs. The use of "first," "second," and similar terms in the description and claims of this patent application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships are changed accordingly.
As shown in fig. 2, a bidirectional-conversion dc isolated converter used between two dc power supplies includes an energy storage freewheeling unit, a high-frequency converting unit, a high-frequency isolating and transforming unit, and a rectifying and filtering unit; the energy storage follow current unit comprises a second capacitor C2 and a follow current inductor, and the high-frequency conversion unit comprises a first switching tube Q101, a second switching tube Q102, a third switching tube Q103, a fourth switching tube Q104, a fifth switching tube Q105 and an absorption filter capacitor Cs1; two ends of the second capacitor C2 are connected with the first direct current source, one end of the follow current inductor is connected with the first direct current source, and the other end of the follow current inductor is connected with the input end of the high-frequency conversion unit; the drain electrode of the first switching tube Q101 is connected with the source electrode of the fifth switching tube Q105, the source electrode is connected with the drain electrode of the third switching tube Q103, the drain electrode of the second switching tube Q102 is connected with the drain electrode of the fifth switching tube Q105, the source electrode is connected with the drain electrode of the fourth switching tube Q104, the source electrode of the fourth switching tube Q104 is connected with the source electrode of the third switching tube Q103, and the drain electrode of the first switching tube Q101 and the source electrode of the third switching tube Q103 form two input ends of the high-frequency conversion unit; the source electrode of the first switching tube Q101 and the source electrode of the second switching tube Q102 form two output ends of the high-frequency conversion unit, one end of the absorption filter capacitor Cs1 is connected with the drain electrode of the second switching tube Q102, and the other end of the absorption filter capacitor Cs1 is connected with the source electrode of the fourth switching tube Q104; the input end of the high-frequency isolation and transformation unit is connected with the output end of the high-frequency conversion unit, the output end of the high-frequency isolation and transformation unit is connected with the input end of the rectification and filtering unit, and the output end of the rectification and filtering unit is connected with the second direct current source.
In the embodiment of the invention, the high-frequency isolation and transformation unit is a high-frequency isolation transformer Tra directly connected with the output end of the high-frequency conversion unit or a high-frequency isolation transformer Tra with a high-frequency isolation capacitor connected in series or a resonant inductor and a resonant capacitor connected in series on the original side edge, and when the high-frequency isolation capacitor connected in series or the resonant inductor and the resonant capacitor connected in series, the primary resonant soft switch transformation can be obtained; and the secondary side of the high-frequency isolation transformer Tra is a single winding or a plurality of windings.
The rectification filter unit comprises a high-frequency rectification circuit and a direct-current filter capacitor C1, the high-frequency rectification circuit is a full-bridge rectification circuit, a full-wave rectification circuit or a voltage doubling rectification circuit, and has a bidirectional conversion function; the input end of the high-frequency rectifying circuit is directly connected with the secondary side of the high-frequency isolation transformer Tra, or is connected with the secondary side of the high-frequency isolation transformer after being connected with the high-frequency isolation capacitor or the resonance inductor and the resonance capacitor in series, so that a resonance soft switch during reverse transformation can be obtained; the output end of the high-frequency rectification circuit is connected with a direct-current filter capacitor C1, and the direct-current filter capacitor C1 is also connected with a second direct-current source.
The high-frequency conversion unit is provided with a rectification mode and an inversion mode; in a rectification mode, the first switch tube Q101 and the third switch tube Q103 are used as a high-frequency conversion switch tube and a boosting tube, the two switch tubes form a composite functional bridge arm, the fifth switch tube Q105 is used as a boosting freewheeling diode and a reverse voltage-reducing conducting connecting line, and the first switch tube to the fifth switch tubes Q101-Q105 are used for different pulse conducting combinations according to driving control to realize boosting and high-frequency conversion; in an inversion mode, the first to fourth switching tubes Q101 to Q104 play a role of high-frequency rectification and can be equivalently used as high-frequency rectifier diodes, the fifth switching tube Q105 is used as a step-down switch and can be conducted in a pulse mode or a through mode, and the first switching tube Q101 and the third switching tube Q103 are matched with the fifth switching tube Q105 to be used as a fly-wheel diode, so that reverse step-down output or through output of direct current is realized; the third switching tube Q103 and the fourth switching tube Q104 are commonly used as boosting tubes and are conducted in a pulse mode according to driving control, and direct-current reverse boosting energy storage output is achieved.
The energy storage inductor is two follow current inductors in series connection or an equivalent inductor after the two follow current inductors are equivalent, and the inductance value of the equivalent inductor is the sum of the inductance values of the two follow current inductors; when the energy storage inductors are two follow current inductors which are in a series connection relationship, one end of a first follow current inductor L1 is connected with a positive output end DC1+ of a first direct current source, the other end of the first follow current inductor L1 is connected with a drain electrode of a first switching tube Q101 and a source electrode of a fifth switching tube Q102, one end of a second follow current inductor L2 is connected with a negative output end DC 1-of the first direct current source, and the other end of the second follow current inductor L2 is connected with a source electrode of a third switching tube Q103 and a fourth switching tube Q105; when the energy storage inductor is an equivalent inductor formed by equivalent two follow current inductors, one end of the equivalent inductor is connected with one output end of the first direct current source, the other end of the equivalent inductor is connected with one input end of the high-frequency conversion unit, and the other input end of the high-frequency conversion unit is connected with the other output end of the first direct current source through a wire.
The first to fifth switching tubes Q101 to Q105 are high-frequency switching tubes provided with anti-parallel diodes or equivalent high-frequency switching tubes with the same function; the anti-parallel diode is an integrated diode, a parasitic diode or an additional diode; the absorption filter capacitor Cs1 is a low-capacity high-frequency nonpolar capacitor or a high-frequency polar capacitor, the absorption filter capacitor Cs1 can absorb the bus peak voltage of a switching tube in the high-frequency conversion unit, and if the high-frequency isolation and transformation unit at the rear end is provided with a resonant circuit, the absorption filter capacitor Cs1 can also absorb and release the difference part between the inductive current and the resonant current of the first follow current inductor L1 and the second follow current inductor L2 so as to assist in realizing resonant soft switching conversion; when the absorption filter capacitor Cs1 is a high-frequency polar capacitor, the positive electrode of the absorption filter capacitor Cs1 is connected to the drain of the fifth switching tube Q105, and the negative electrode of the absorption filter capacitor Cs1 is connected to the source of the fourth switching tube Q104.
The working principle of the invention is explained below with reference to specific embodiments:
example 1
As shown in fig. 3, in embodiment 1, the freewheeling inductor of the energy storage freewheeling unit is two freewheeling inductors in a series relationship, one end of the first freewheeling inductor L1 is connected to the positive output terminal DC1+ of the first DC source, the other end is connected to the drain of the first switching tube Q101 and the source of the fifth switching tube Q102, one end of the second freewheeling inductor L2 is connected to the negative output terminal DC 1-of the first DC source, and the other end is connected to the sources of the third switching tube Q103 and the fourth switching tube Q105. The high-frequency isolation and transformation unit is a high-frequency isolation transformer Tra with an original side connected with a resonant inductor Lr and a resonant capacitor Cr in series, and the secondary side of the high-frequency isolation transformer Tra is provided with a single winding. The high-frequency rectifying circuit is a full-bridge rectifying circuit, and the full-bridge rectifying circuit comprises a seventh switching tube Q107, an eighth switching tube Q108, a ninth switching tube Q109 and a tenth switching tube Q110; the drain electrode of the seventh switching tube Q107 is connected with the drain electrode of the eighth switching tube Q108 to form the positive output end of the full-bridge rectification circuit, and the source electrode of the ninth switching tube Q109 is connected with the source electrode of the tenth switching tube Q110 to form the negative output end of the full-bridge rectification circuit; the source of the seventh switching tube Q107 is connected to the drain of the ninth switching tube Q108 to form one input terminal of a full-bridge rectifier circuit, the source of the eighth switching tube Q108 is connected to the drain of the tenth switching tube Q110 to form the other input terminal of the full-bridge rectifier circuit, and the two input terminals are connected to the secondary side of the high-frequency isolation transformer Tra. The positive output end and the negative output end of the full-bridge rectification circuit are connected with a direct current filter capacitor C1, and the direct current filter capacitor C1 is also connected with a positive output end DC2+ of a second direct current source and a negative output end DC 2-of the second direct current source.
The control method of embodiment 1 includes the steps of:
s100: and selecting a working mode, wherein the working mode comprises a rectification mode and an inversion mode, the rectification mode is input from the first direct current source end and output from the second direct current source end, and the inversion mode is input from the second direct current source end and output from the first direct current source end.
S200: according to the selected working mode, no driving signal or only synchronous rectification driving signal is applied to the switching tube which works as a diode or a follow current tube in the direct current isolation type converter, a high-level direct driving signal is applied to the switching tube which needs to work in a direct current mode, and no driving signal or a low-level non-conducting signal is applied to the switching tube which does not need to be conducted.
S300: if the working mode is a rectification mode, converting the voltage instantaneous value of the current first direct current source, the output voltage setting and the transformation ratio to the primary side of the high-frequency isolation and transformation unit, judging whether the direct current isolation type converter needs to carry out voltage reduction or voltage boosting, determining whether to carry out voltage boosting PWM (pulse width modulation) drive control on a switching tube used as a voltage boosting tube in a composite bridge arm of the high-frequency conversion unit, and simultaneously determining whether to carry out PWM drive conduction on other switching tubes; if boosting is needed, common driving needs to be applied to the first switching tube Q101 and the third switching tube Q103 to form boosting, and the second switching tube Q102 and the fourth switching tube Q104 are matched with high-frequency conversion corresponding to bridge-type pair tubes; if voltage reduction or voltage boosting is not needed, normal bridge driving is applied to the first switch tube to the fourth switch tubes Q101-Q104 to perform high-frequency conversion; the fifth switching tube Q105 is turned off when the dc isolated converter is boosted or turned off in a non-conducting region when the dc isolated converter is stepped down, and is turned on when the bridge high frequency conversion is conducted.
S400: if the working mode is the inversion mode, converting the voltage instantaneous value of the current second direct current source and the transformation ratio to the first direct current source end, comparing the output voltage setting, judging whether the direct current isolated converter needs to carry out voltage reduction or voltage increase, and determining whether the voltage reduction PWM driving control is carried out on the fifth switching tube Q105 and the composite bridge arm of the high-frequency conversion unit; meanwhile, whether a switching tube of a high-frequency rectification circuit in the rectification filter unit is conducted in a PWM driving mode or not is determined; if boosting is needed, common driving needs to be applied to the third switching tube Q103 and the fourth switching tube Q104 to form boosting energy storage; if voltage reduction or voltage increase is not needed, normal bridge type driving is applied to a switching tube of a high-frequency rectifying circuit in the rectifying filter unit to carry out high-frequency conversion; the fifth switching tube Q105 is turned off in the composite bridge arm freewheeling or buck rectification non-conduction interval and is turned on in the bridge rectification conduction interval or boost energy storage interval.
In steps S300 to S400, in the rectification mode, a driving signal for short-circuiting a coil of the high-frequency isolation transformer is applied to a switching tube of a high-frequency rectification circuit in the rectification filter unit, so that the dc isolation type converter enters a boost energy storage state; in the inversion mode, a drive signal with a variable duty ratio is applied to the high-frequency rectification circuit and the fifth switching tube Q105, so that the direct-current isolated converter can realize the voltage reduction regulation of the output voltage. When the fifth switching tube Q105 is in the PWM operating state, the PWM switching frequency of the fifth switching tube Q105 is the same as or doubled as the PWM switching frequency of the switching tube of the high frequency conversion unit or the high frequency rectification circuit. In a step-down rectification mode, first and fourth switching tubes Q101 and Q104 and second and third switching tubes Q102 and Q103 which are used as geminate transistors in the high-frequency conversion unit are respectively applied with centrosymmetric PWM driving signals, and a fifth switching tube Q105 is applied with PWM driving signals which are correspondingly integrated with a conduction interval of an inclined geminate transistor formed by the first switching tube Q101 and the fourth switching tube Q104; under the voltage reduction inversion mode, centrosymmetric PWM driving signals are respectively applied to bridge type geminate transistors or single transistors which are inverted in the high-frequency rectifying circuit, and PWM driving signals which are correspondingly integrated with a conduction interval of an inclined geminate transistor formed by the first switching tube Q101 and the fourth switching tube Q104 are applied to a fifth switching tube Q105 in the high-frequency conversion unit.
The working principle of example 1 is as follows:
in the rectification mode, the first direct current source is connected with an input power supply, and a load or a circuit which can be equivalent to the load can be connected between the positive output end and the negative output end of the second direct current source. According to the basic principle of circuit voltage reduction, when the output voltage is set and converted according to the transformation ratio until the voltage Ve at the first direct current source side is lower than the input voltage, voltage reduction is formed; when Ve is set to be greater than the input voltage, the output operating state of embodiment 1 is a boosted state. When the input voltage is stepped, the rectified power supply or the voltage of the load at the output end varies in a wide range, the operation state of embodiment 1 may be both step-up and step-down.
(1) Determining a buck state based on input-output voltage requirements
At this time, the seventh to tenth switching tubes Q107 to Q110 do not need to be applied with PWM driving conduction, the seventh to tenth switching tubes Q107 to Q110 may be equivalent to diodes, and natural rectification or freewheeling conduction may be performed, and the circuit diagram of fig. 3 is equivalent to the state shown in fig. 4, if the seventh to tenth switching tubes Q107 to Q110 are high frequency switching tubes provided with anti-parallel diodes, the PWM driving may be applied for synchronous rectification when the anti-parallel or equivalent diodes are conducted, and meanwhile, the fifth switching tube Q105 is applied with a through driving signal, so that it may be equivalent to one conducting wire, and fig. 4 may be further equivalent to fig. 5.
In the high-frequency conversion unit, when a through driving signal is applied to the fifth switching tube Q105 and the fifth switching tube Q105 is equivalent to a single conducting wire, the output ports of the absorption filter capacitor Cs1, the first freewheeling inductor L1 and the second freewheeling inductor L2 are directly connected in parallel, the first to fourth switching tubes Q101 to Q104 operate in a full-bridge operating mode, and the duty ratio of each switching tube can be approximately considered to be 50% when the dead zone is ignored, that is, as shown in fig. 7 a. Therefore, the part of the first freewheeling inductor L1 and the second freewheeling inductor L2 where the inductive current exceeds the resonant current is absorbed by the absorption filter capacitor Cs1, and the part of the first freewheeling inductor L1 and the second freewheeling inductor L2 where the inductive current is less than the resonant current is released and supplemented by the absorption filter capacitor Cs1 as the high-frequency conversion proceeds. Without the absorption filter capacitor Cs1, the resonant current of the full-bridge resonant transformation will clamp and interfere with the input inductor current. If the converter operating frequency is higher or lower than the natural resonant frequency of the full-bridge resonant conversion
Wherein Lr is an inductance of the resonant inductor Lr, cr is a capacitance of the resonant capacitor Cr, and the high frequency conversion unit generates a step-down voltage or a step-up voltage due to the resonant conversion characteristic. When the first to fourth switching tubes Q101 to Q104 operate in the full-bridge conversion operation mode, the seventh to tenth switching tubes Q107 to Q110 may be regarded as a typical full-bridge rectifier, and the current is output to the dc filter capacitor C1 and the dc output load. The relevant working principle is the prior art, and the description is not repeated herein.
Besides the frequency modulation mentioned above, an inductor is connected in series between the secondary side of the high-frequency isolation transformer Tra and the high-frequency rectification circuit, and a conventional duty ratio adjustment can be applied to the high-frequency conversion circuit to adjust the output voltage, the PWM driving square wave of each pair of paired tubes may be a conventional square wave signal spaced by half a switching period or a square wave signal with a reduced duty ratio directly on the basis of fig. 7 (a), or may be a square wave signal as shown in fig. 11 (b), and a PWM driving signal is sent to another pair of paired tubes immediately after the PWM driving square wave of the previous pair of paired tubes is turned off, that is, a PWM driving signal with central symmetry is applied to the first switching tube Q101 and the fourth switching tube Q104, and the second switching tube Q102 and the third switching tube Q103 in the high-frequency conversion unit, respectively. Under such a condition, the fifth switching tube Q105 may no longer be applied with a signal of complete conduction, or the fifth switching tube Q105 may no longer be considered as a conducting wire, but a PWM drive corresponding to the conduction interval of the pair transistors is applied to the fifth switching tube Q105, and when the pair transistors are turned off, the fifth switching tube Q105 is also turned off. Therefore, the PWM switching frequency of the fifth switching tube Q105 should be doubled or consistent with the PWM switching frequency of the switching tube of the high frequency conversion unit.
(2) Determining a boost condition based on input-output voltage requirements
Different from the voltage reduction state, in the voltage increase state, the fifth switching tube Q105 cannot be directly conducted, and at this time, the fifth switching tube Q105 is equivalent to a voltage increase freewheeling diode, and must be matched with a complex function bridge arm formed by the first switching tube Q101 and the third switching tube Q103 to perform voltage increase conversion, and at this time, fig. 4 may be equivalent to fig. 6. Because boost is needed, an alternating current input loop forms a short-circuit channel so that the first follow current inductor L1 and the second follow current inductor L2 can store energy and boost, and DC/DC conversion at the rear end cannot be affected, a composite functional bridge arm consisting of the fifth switching tube Q105, the first switching tube Q101 and the third switching tube Q103 must be reasonably utilized to perform boost conversion at a specific driving time sequence. When the third switch tube Q103 and the second switch tube Q102 form a pair tube for high-frequency conversion, if the first switch tube Q101 is not yet turned on, the inductor current of the first follow current inductor L1 and the second follow current inductor L2 and the absorption filter capacitor Cs1 can both supply power to the pair tube path formed by the third switch tube Q103 and the second switch tube Q102, if the first switch tube Q101 is turned on soon after the third switch tube Q103 and the second switch tube Q102 are turned on or during the turn-on period, that is, the driving of the first switch tube Q101 is turned on in advance on the basis of fig. 7 (a), and the driving signal at this time is as shown in fig. 7 (b), the first switch tube Q101 and the third switch tube Q103 are simultaneously driven to be turned on, so that the short circuit of the first follow current inductor L1 and the second follow current inductor L2 can be realized and energy storage can be realized, at this time, the fifth switch tube Q105 is not driven by PWM and can be regarded as a diode, and the absorption filter capacitor Cs1 is isolated, the capacitance function of the absorption filter capacitor Cs1 is not affected, and the high-frequency conversion is continuously supplied power. When the first switch tube Q101 is turned off, because of the existence of the first follow current inductor L1 and the second follow current inductor L2, the current cannot be reversed, the original direction is continuously maintained, the inductor electromotive force can generate reverse energy-releasing follow current, the inductor electromotive force and the input voltage form series connection, the inductor electromotive force and the first direct current source together supply power to the high-frequency conversion unit, and at the moment, the fifth switch tube is conducted, and the PWM drive can be applied to perform synchronous rectification. When the pair transistor circuit formed by the third switching transistor Q103 and the second switching transistor Q102 finishes working, the pair transistor circuit formed by the first switching transistor Q101 and the fourth switching transistor Q104 is alternately worked, at this time, the power supply circuit at the alternating current end can directly supply power to the first switching transistor Q101 and the fourth switching transistor Q104, and at the same time, in order to avoid the influence of the inductive current and the difference value part of the resonant conversion current, the fifth switching transistor Q105 should be switched on. Regarding the moment when the first switch tube Q101 is turned on and the moment when the first freewheeling inductor L1 and the second freewheeling inductor L2 start to release energy and boost power, the oblique pair tube composed of the first switch tube Q101 and the fourth switch tube Q104 should be alternately changed in high frequency, because the current of the pair tube composed of the third switch tube Q103 and the second switch tube Q102 should be in a falling interval before, the influence caused by the superposition of the inductive energy storage currents of the first freewheeling inductor L1 and the second freewheeling inductor L2 can be relatively reduced, meanwhile, the first switch tube Q101 does not need to be turned off, the natural turning off of the third switch tube Q103 can end the energy storage and boost, and the soft turning off can be realized. At this time, if the first switching tube Q101 is continuously turned on, it can be used as an inductive freewheeling channel and a next-stage alternate channel of high-frequency conversion, so that the loss of once-on switching in the middle of turning off can be reduced. Therefore, the boosting timing of the first switching tube Q101 is preferably in a section before the completion of the operation of the tube-to-tube path formed by the third switching tube Q103 and the second switching tube Q102, that is, before the completion of the boosting composite operation for the first switching tube Q101.
As is clear from the above operation principle, the boosting operation is mainly performed in the pair-pipe passage section formed by the third switching pipe Q103 and the second switching pipe Q102 and is common to the first switching pipe Q101, and in addition, a driving method shown in fig. 7 (c) or fig. 7 (d) may be adopted, that is, in addition to the driving shown in fig. 7 (a), the composite arm first switching pipe Q101 and the third switching pipe Q103 are common to boost in the conduction section where the pair-pipes of the third switching pipe Q103 and the second switching pipe Q102 and the pair-pipes of the first switching pipe Q101 and the fourth switching pipe Q104 are adjacent to each other, and at this time, the fifth switching pipe Q105 must be turned off. Therefore, compared with the boost driving method shown in fig. 7 (a) or fig. 7 (b), the boost driving method can achieve boost expansion, but has the disadvantage that the dc conversion is interrupted when the boost is performed, so that the PWM switching frequency of the fifth switching tube Q105 still coincides with the PWM switching frequency of the switching tube of the high frequency converting unit or is twice the PWM switching frequency of the switching tube of the high frequency converting unit, which needs to be selected specifically according to the situation in use.
In addition, a drive signal for short-circuiting the coil of the high-frequency isolation transformer Tra is applied to the switching tube of the high-frequency rectification circuit in the rectification filter unit, and the high-frequency isolation transformer Tra can also enter a boost energy storage mode, for example, a short-circuit conducting signal is applied to the seventh switching tube Q107 and the eighth switching tube Q108 (or the ninth switching tube Q109 and the tenth switching tube Q110) when the resonance is about to cross zero, so that the secondary side of the high-frequency isolation transformer Tra is short-circuited, at this time, boost energy storage is performed on the leakage inductance of the high-frequency isolation transformer Tra and the resonant inductance Lr in series connection with the coil of the high-frequency isolation transformer Tra, then the PWM drive signal is turned off, the short-circuit condition of the secondary side of the high-frequency isolation transformer Tra is interrupted, the leakage inductance Lr or the high-frequency isolation transformer Tra is equivalently connected in series to the output rectification circuit, and the inductance electromotive force is reversed and connected in series with the same direction as the output rectification at this time, so that boost is formed.
From the above analysis, in the above boosting state, embodiment 1 avoids unnecessary boosting or voltage dropping and intermediate capacitor energy storage processes in the conventional two-stage converter shown in fig. 1, thereby realizing multiplexing of the boost switching tube, reducing the loss of the conventional boost switching tube, and improving the system efficiency.
In an inversion mode, the second direct current source end is connected with a direct current power supply and is connected with the direct current filter capacitor C1 in parallel, the first direct current source end is connected with an equivalent load, and the equivalent load can be a power supply or a load for absorbing energy. According to the basic principle of dc voltage reduction, when the voltage Ve at the second dc source side is converted to a voltage Ve at the first dc source side that is higher than the output voltage at the first dc source side, voltage reduction is performed, otherwise voltage boosting may be required. Therefore, as shown in fig. 8, in the embodiment 1, when operating in the inverter state, the first to fourth switching tubes Q101 to Q104 perform rectification, and thus can be equivalent to diodes.
(1) It is assumed that the determination of the boost state is based on the input/output voltage conversion requirement
Firstly, a fifth switch tube Q105 is completely conducted, meanwhile, a full-bridge rectification circuit in a rectification filter unit on the secondary side direct current side conducts full-bridge inversion work, a seventh switch tube to a tenth switch tube Q107-Q110 form a typical H bridge, when the seventh switch tube Q107 and the tenth switch tube Q110 are subjected to PWM driving as shown in fig. 11 (a) or a eighth switch tube Q108 and a ninth switch tube Q109 are subjected to PWM driving, the voltage on the direct current side is directly transmitted to the primary side through coupling of a high-frequency transformer Tra, then the voltage is automatically rectified to form direct current voltage through full-bridge connection of a first switch tube to a fourth switch tube Q101-Q104 through the high-frequency transformer Tra, the direct current voltage is charged to an absorption filter capacitor Cs1, the voltage can be regarded as an equivalent direct current source, the positive electrode of the absorption filter capacitor Cs1 and the source electrode of a fourth switch tube Q104 are connected with a first follow current inductor L1, the equivalent positive electrode is connected with a negative electrode of the absorption filter capacitor Cs1, and the source of the fourth switch tube Q104 are connected with a second follow current inductor L2, and the equivalent positive electrode is connected with a high-frequency conversion inductor L2 port equivalent to the first follow current inductor L2; meanwhile, the fifth switching tube Q105 of the energy storage freewheeling unit is driven by PWM, so that fig. 8 can be equivalent to fig. 9, and since the fifth switching tube Q105 is always in a conducting state and can be regarded as a conducting wire, embodiment 1 can be changed into a soft-switching full-bridge dc converter with secondary side series resonance. The resonant inductor Lr and the resonant capacitor Cr are connected in series in the circuit, so that the boosting or voltage reducing function brought by the frequency change of the high-frequency isolation and voltage transformation unit can be fully utilized in use, under the condition of the same load, the higher the switching frequency is, the more the boosting is, the specific working principle is the prior art, and the detailed description is not repeated herein.
In addition, a driving signal for short-circuiting the coil of the high-frequency isolation transformer Tra is applied to the switching tube of the high-frequency rectifying part in the rectifying and filtering unit, and the high-frequency isolation transformer Tra can also enter a boosting and energy storage mode, for example, a short-circuit conducting signal is applied to the third switching tube Q103 and the fourth switching tube Q104 when the rectifying current is about to pass zero or before the next rectification starts, so that the output side coil of the high-frequency isolation transformer Tra is short-circuited, the boosting and energy storage is performed on the leakage inductance of the high-frequency isolation transformer Tra and the resonant inductance Lr in series connection with the coil of the high-frequency isolation transformer Tra at the moment, then the PWM driving signal is turned off, the working condition of the secondary side short circuit of the high-frequency isolation transformer Tra is interrupted, the leakage inductance Lr in the original circuit or the leakage inductance of the high-frequency isolation transformer Tra can be equivalently connected in series to the output rectifying circuit, the electromotive force of the inductance is reversed and is connected in series with the output rectifying circuit in the same direction at the moment, thereby boosting and the full-bridge automatic rectifying output from the first switching tube Q101 to the fourth switching tube Q104.
(2) The voltage Ve demand converted from the voltage of the second direct current source to the voltage Ve of the first direct current source side is judged as a voltage reduction state
In this case, fig. 8 is equivalent to fig. 10, which is equivalent to adding a dc input step-down circuit to the rectified output loop of the full-bridge inverter.
Therefore, the equivalent dc source voltage to be applied to the first and second freewheeling inductors L1 and L2 must be reduced or changed to the PWM regulation mode because the first and second freewheeling inductors L1 and L2 exist, and if the equivalent dc source is applied in accordance with the duty ratio calculated by the control like a Buck circuit, the voltage will be reduced in accordance with the duty ratio. If the time for connecting the equivalent direct current source formed by full-bridge rectification to the first follow current inductor L1 and the second follow current inductor L2 is reduced, a step-down is formed, so that a PWM driving signal for reducing the duty ratio on the basis of a PWM driving signal with a duty ratio of 50% shown in fig. 11 (a) is applied to the typical H-bridge formed by the seventh to tenth switching tubes Q107 to Q110, the PWM driving signal is applied to the fifth switching tube Q105 to conduct, and the connection of the absorption filter capacitor Cs1, the pair of the second switching tube Q102 and the third switching tube Q103, and the pair of the first switching tube Q101 and the fourth switching tube Q104 to the first follow current inductor L1 and the second follow current inductor L2 is reduced, so that Buck application of the equivalent direct current source is formed, that after the second switching tube Q102 and the third switching tube Q103 form rectification, the fifth switching tube Q105 is turned off according to the duty ratio requirement, and at this time, the first follow current inductor L1 and the second follow current inductor L2 continue to absorb the filter capacitor Q1 and the second follow current inductor Q103 through the first switching tube Q103 and the second switching tube Q103.
In addition, there is another mode in which the aforementioned equivalent direct current source PWM pattern is applied to the first freewheeling inductor L1 and the second freewheeling inductor L2, that is, the duty ratio of the full-bridge inversion of the rectification filter unit on the second direct current source side is changed from approximately 50% by 2 to the PWM driving duty ratio D2 required for the converter operation control, and the PWM conductive driving of the full-bridge inversion is tightly connected on the center side and is non-conductive driven on both sides, if the pair of the seventh switching tube Q107 and the tenth switching tube Q110 is denoted by a, the pair of the eighth switching tube Q108 and the ninth switching tube Q109 is denoted by B, as shown in fig. 11 (B), the rectification on the primary side is a pair of full-bridge rectification, that is, the first switching tube Q101 and the fourth switching tube Q104, and the second switching tube Q102 and the third switching tube Q103D are also pulse voltage rectification with central symmetric 2d × T time conduction, where T is a switching period; meanwhile, when the rectification is conducted, the fifth switching tube Q105 is applied with PWM driving, and the voltage of the absorption filter capacitor Cs1 and the rectified voltage, that is, the equivalent dc source is applied to the ports of the first freewheeling inductor L1 and the second freewheeling inductor L2 according to the PWM mode of 2*D, thereby achieving the aforementioned voltage reduction purpose.
According to the above working principle, when the fifth switching tube Q105 is in the PWM working state, the PWM switching frequency of the fifth switching tube Q105 is the same as or is in a double frequency relationship with the PWM switching frequency of the switching tube of the high frequency rectification circuit. In addition, on some occasions with relatively high output voltage, the mode of improving the withstand voltage by connecting the switching tube and the filter capacitor in series or in similar series can be adopted in consideration of the selection of the switching tube and the back-end filter voltage.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A DC isolation type converter capable of bidirectional conversion is used between two DC power supplies and is characterized by comprising an energy storage follow current unit, a high-frequency conversion unit, a high-frequency isolation and transformation unit and a rectification and filtering unit; the high-frequency conversion unit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube and an absorption filter capacitor; two ends of the second capacitor are connected with the first direct current source, one end of the follow current inductor is connected with the first direct current source, and the other end of the follow current inductor is connected with the input end of the high-frequency conversion unit; the drain electrode of the first switching tube is connected with the source electrode of the fifth switching tube, the source electrode of the first switching tube is connected with the drain electrode of the third switching tube, the drain electrode of the second switching tube is connected with the drain electrode of the fifth switching tube, the source electrode of the second switching tube is connected with the drain electrode of the fourth switching tube, the source electrode of the fourth switching tube is connected with the source electrode of the third switching tube, and the drain electrode of the first switching tube and the source electrode of the third switching tube form two input ends of the high-frequency conversion unit; the source electrode of the first switch tube and the source electrode of the second switch tube form two output ends of the high-frequency conversion unit, one end of the absorption filter capacitor is connected with the drain electrode of the second switch tube, and the other end of the absorption filter capacitor is connected with the source electrode of the fourth switch tube; the input end of the high-frequency isolation and transformation unit is connected with the output end of the high-frequency conversion unit, the output end of the high-frequency isolation and transformation unit is connected with the input end of the rectification and filtering unit, and the output end of the rectification and filtering unit is connected with the second direct current source.
2. The bi-directional convertible dc isolation type converter according to claim 1, wherein the high frequency isolation and transformation unit is a high frequency isolation transformer directly connected to the output terminal of the high frequency conversion unit or a high frequency isolation transformer having a high frequency isolation capacitor connected in series to its primary side or a resonant inductor and a resonant capacitor connected in series to its primary side, and the secondary side of the high frequency isolation transformer is a single winding or multiple windings.
3. The converter according to claim 2, wherein the rectifying and filtering unit comprises a high frequency rectifying circuit and a dc filtering capacitor, the high frequency rectifying circuit is a full bridge rectifying circuit, a full wave rectifying circuit or a voltage doubling rectifying circuit, and an input end of the high frequency rectifying circuit is directly connected to the secondary side of the high frequency isolation transformer or is connected in series with the high frequency isolation capacitor or the resonant inductor and the resonant capacitor and then connected to the secondary side of the high frequency isolation transformer; the output end of the high-frequency rectifying circuit is connected with a direct-current filter capacitor, and the direct-current filter capacitor is also connected with a second direct-current source.
4. The isolated DC converter according to claim 1, wherein the high frequency converting unit has a rectifying mode and an inverting mode; in a rectification mode, the first switch tube and the third switch tube are used as a high-frequency conversion switch tube and a boosting tube, the two switch tubes form a composite functional bridge arm, the fifth switch tube is used as a boosting freewheeling diode and also used as a reverse voltage-reduction conducting connecting wire, and the first switch tube to the fifth switch tube are made into different pulse conducting combinations according to drive control to realize boosting and high-frequency conversion; in an inversion mode, the first switching tube to the fourth switching tube play a role in high-frequency rectification, are equivalent to a high-frequency rectifier diode, the fifth switching tube is used as a voltage reduction switch and can be conducted in a pulse mode or a direct mode, and the first switching tube and the third switching tube are matched with the fifth switching tube to be used as a freewheeling diode, so that direct-current reverse voltage reduction output or direct output is realized; the third switching tube and the fourth switching tube are commonly used as boosting tubes and are in pulse conduction according to driving control, and direct-current reverse boosting energy storage output is achieved.
5. The isolated DC converter according to claim 1, wherein the energy storage inductor is two freewheeling inductors connected in series or an equivalent inductor formed by two equivalent freewheeling inductors, and the inductance of the equivalent inductor is the sum of the inductances of the two freewheeling inductors; when the energy storage inductor is two follow current inductors which are in series connection, one end of the first follow current inductor is connected with the positive output end of the first direct current source, the other end of the first follow current inductor is connected with the drain electrode of the first switch tube and the source electrode of the fifth switch tube, one end of the second follow current inductor is connected with the negative output end of the first direct current source, and the other end of the second follow current inductor is connected with the source electrodes of the third switch tube and the fourth switch tube; when the energy storage inductor is an equivalent inductor formed by equivalence of two follow current inductors, one end of the equivalent inductor is connected with one output end of the first direct current source, the other end of the equivalent inductor is connected with one input end of the high-frequency conversion unit, and the other input end of the high-frequency conversion unit is connected with the other output end of the first direct current source through a lead.
6. The bidirectional-convertible direct-current isolated converter according to claim 1, wherein the first to fifth switching tubes are high-frequency switching tubes provided with antiparallel diodes, or equivalently high-frequency switching tubes with the same function; the anti-parallel diode is an integrated diode, a parasitic diode or an additional diode; the absorption filter capacitor is a high-frequency non-polar capacitor or a high-frequency polar capacitor; when the absorption filter capacitor is a high-frequency polar capacitor, the anode of the absorption filter capacitor is connected with the drain electrode of the fifth switch tube, and the cathode of the absorption filter capacitor is connected with the source electrode of the fourth switch tube.
7. A method for controlling a bidirectionally-switchable dc isolated converter according to any of claims 1~6, comprising the steps of:
s100: selecting a working mode, wherein the working mode comprises a rectification mode and an inversion mode, the rectification mode is input from a first direct current source end, the second direct current source end outputs, the inversion mode is input from a second direct current source end, and the first direct current source end outputs;
s200: according to the selected working mode, applying no driving signal or only a synchronous rectification driving signal to a switching tube which works as a diode or a follow current tube in the direct current isolation type converter, applying a high-level direct driving signal to the switching tube which needs to work in direct current, and applying no driving signal or a low-level non-conducting signal to the switching tube which does not need to be conducted;
s300: if the working mode is a rectification mode, converting the voltage instantaneous value of the current first direct current source, the output voltage setting and the transformation ratio to the primary side of the high-frequency isolation and transformation unit, judging whether the direct current isolation type converter needs to carry out voltage reduction or voltage boosting, determining whether to carry out voltage boosting PWM (pulse width modulation) drive control on a switching tube used as a voltage boosting tube in a composite bridge arm of the high-frequency conversion unit, and simultaneously determining whether to carry out PWM drive conduction on other switching tubes; if boosting is needed, common driving needs to be applied to the first switching tube and the third switching tube to form boosting, and the second switching tube and the fourth switching tube are matched to correspond to high-frequency conversion of the bridge pair tubes; if voltage reduction or voltage boosting is not needed, normal bridge driving is applied to the first switching tube to the fourth switching tube to perform high-frequency conversion; the fifth switching tube is closed when the direct current isolated converter is boosted or closed in a non-conducting area when the direct current isolated converter is stepped down, and is opened when the bridge type high-frequency conversion is conducted;
s400: if the working mode is the inversion mode, converting the voltage instantaneous value of the current second direct current source and the transformation ratio to the first direct current source end, comparing the output voltage setting, judging whether the direct current isolated converter needs to carry out voltage reduction or voltage increase, and determining whether the voltage reduction PWM driving control is carried out on a fifth switching tube and a composite bridge arm of the high-frequency conversion unit; meanwhile, whether a switching tube of a high-frequency rectifying circuit in the rectifying filter unit is conducted in a PWM driving mode or not is determined; if boosting is needed, common driving needs to be applied to the third switching tube and the fourth switching tube to form boosting energy storage; if voltage reduction or voltage boosting is not needed, normal bridge type driving is applied to a switching tube of a high-frequency rectification circuit in the rectification filter unit to carry out high-frequency conversion; the fifth switching tube is closed in a composite bridge arm follow current or voltage reduction rectification non-conduction interval and is conducted in a bridge rectification conduction or voltage boosting energy storage interval.
8. The method for controlling a bidirectional-switchable DC isolated converter according to claim 7, wherein in steps S300-S400, the DC isolated converter enters a boost energy storage state by applying a driving signal for short-circuiting a coil of the high-frequency isolation transformer to a switching tube of a high-frequency rectification circuit in the rectification filter unit in a rectification mode; in an inversion mode, a drive signal with a variable duty ratio is applied to the high-frequency rectification circuit and the fifth switching tube, so that the direct-current isolation type converter can realize the voltage reduction regulation of the output voltage.
9. The method for controlling a bidirectional-switchable DC isolated converter according to claim 7, wherein in steps S300 to S400, when the fifth switching tube is in a PWM operating state, the PWM switching frequency of the fifth switching tube is the same as or doubled as the PWM switching frequency of the switching tube of the high-frequency switching unit or the high-frequency rectifying circuit.
10. The control method of the bidirectional-conversion direct-current isolated converter according to claim 7, wherein in steps S300 to S400, in a step-down rectification mode, a first switching tube and a fourth switching tube as a pair tube and a second switching tube and a third switching tube in a high-frequency conversion unit are respectively applied with center-symmetric PWM driving signals, and a fifth switching tube is applied with a PWM driving signal corresponding to a conduction interval of an oblique pair tube formed by the first switching tube and the fourth switching tube; under the voltage reduction inversion mode, centrosymmetric PWM driving signals are respectively applied to bridge type geminate transistors or single transistors which are inverted in the high-frequency rectifying circuit, and PWM driving signals which are correspondingly integrated with a conduction interval of an inclined geminate transistor formed by the first switching tube and the fourth switching tube are applied to a fifth switching tube in the high-frequency conversion unit.
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| CN202211460949.0A CN115694203B (en) | 2022-11-17 | 2022-11-17 | DC isolated converter capable of bidirectional conversion and control method thereof |
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| CN116223869A (en) * | 2023-05-06 | 2023-06-06 | 合肥航太电物理技术有限公司 | C wave generating device for aircraft lightning test |
| CN116633160A (en) * | 2023-07-26 | 2023-08-22 | 南京航空航天大学 | Single-stage isolated bidirectional/unidirectional DC-DC converter and control method |
| CN117595649A (en) * | 2023-11-27 | 2024-02-23 | 深圳市迪威电气有限公司 | Multiport input non-isolated direct current converter and control method thereof |
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