CN110868075A - Bidirectional DC/DC converter and working method thereof - Google Patents
Bidirectional DC/DC converter and working method thereof Download PDFInfo
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- CN110868075A CN110868075A CN201911018543.5A CN201911018543A CN110868075A CN 110868075 A CN110868075 A CN 110868075A CN 201911018543 A CN201911018543 A CN 201911018543A CN 110868075 A CN110868075 A CN 110868075A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33584—Bidirectional converters
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
The invention relates to a bidirectional DC/DC converter and a working method thereof, belongs to the technical field of control circuits, and solves the problems of complex control logic, high control difficulty and the like of the converter. The converter comprises a primary side circuit, an isolation transformer and a secondary side circuit; the primary side circuit and the secondary side circuit both comprise an inversion module branch and a capacitor branch, the inversion module branch comprises two inversion modules which are connected in series, and the capacitor branch comprises two capacitors which are connected in series; one end of the inversion module branch is connected with one end of the capacitor branch; the positive output end of the primary side circuit or the secondary side circuit is led out from the joint of the two inversion modules, and the negative output end of the primary side circuit or the secondary side circuit is led out from the joint of the two capacitors; the positive electrode of the low-voltage side power supply is connected with the positive output end of the primary side circuit, and the negative electrode of the low-voltage side power supply is connected with the other end of the inversion module branch in the primary side circuit and the other end of the capacitor branch; the positive pole of the high-voltage side power supply is connected with one end of the inversion module branch, and the negative pole of the high-voltage side power supply is connected with the other end of the inversion module branch and the other end of the capacitor branch in the primary side circuit.
Description
Technical Field
The invention relates to the technical field of DC/DC control circuits, in particular to a bidirectional DC/DC converter and a working method thereof.
Background
Bidirectional DC/DC converters are often used in photovoltaic energy storage systems as a path for energy flow. With the development of ICPT systems, bidirectional DC/DC converters are also gradually entering the ICPT field. The bidirectional DC-DC converter has become a research focus as an interface for bidirectional flow of energy in ICPT system.
In general, a bidirectional dc converter can be classified into two types, i.e., an isolated type and a non-isolated type, according to whether an electrical isolation link exists. The non-isolated bidirectional DC/DC converter has the advantages of simple structure, convenient control, small size and low cost, but the DC/DC conversion ratio is smaller, so that the non-isolated bidirectional DC/DC converter is not suitable for application occasions with more voltage grade difference between the direct current low-voltage side and the direct current high-voltage side. The isolated bidirectional DC/DC converter has the advantages of easy realization of soft switching, high system efficiency and high voltage transformation ratio, but the original secondary side of the existing bidirectional DC/DC converter comprises 4 switching tubes, the circuit structure is large in size and high in cost, the switching tube driving signals need to control the conduction condition of the 4 switching tubes simultaneously, the control logic is complex, and the control difficulty is high.
Disclosure of Invention
In view of the above analysis, the present invention is directed to provide a bidirectional DC/DC converter and a method for operating the same, so as to solve the problems of the existing bidirectional DC/DC converter, such as large circuit structure, high cost, complex control logic, and difficult control.
The purpose of the invention is mainly realized by the following technical scheme:
a bidirectional DC/DC converter comprises a primary side circuit, an isolation transformer and a secondary side circuit; the primary side circuit and the secondary side circuit respectively comprise an inversion module branch and a capacitor branch, the inversion module branch comprises two inversion modules which are connected in series, and the capacitor branch comprises two capacitors which are connected in series; one end of the inversion module branch is connected with one end of the capacitor branch; the positive output end of the primary side circuit or the secondary side circuit is led out from the connection position of the two inversion modules, and the negative output end of the primary side circuit or the secondary side circuit is led out from the connection position of the two capacitors;
the positive electrode of the low-voltage side power supply is connected with the positive output end of the primary side circuit, and the negative electrode of the low-voltage side power supply is connected with the other end of the inversion module branch circuit and the other end of the capacitor branch circuit in the primary side circuit;
and the anode of the high-voltage side power supply is connected with one end of the inversion module branch, and the cathode of the high-voltage side power supply is connected with the other end of the inversion module branch and the other end of the capacitor branch in the primary side circuit.
On the basis of the scheme, the invention is further improved as follows:
further, the inversion module structures in the primary side circuit and the secondary side circuit are the same, and both comprise: a switch tube, a diode and a capacitor; and a diode is reversely connected in parallel between the drain electrode and the source electrode of the switching tube, and the capacitor is connected in parallel.
Further, the grid electrode of the switch tube is used for receiving a driving signal.
Further, the primary side circuit further comprises an inductor L and a capacitor CL, the capacitor CL is connected in parallel to two sides of the low-voltage side power supply, and the inductor L is connected in series between the positive electrode of the low-voltage side power supply and the positive output end of the primary side circuit.
Further, the isolation transformer is a loosely coupled transformer.
Furthermore, the bidirectional DC/DC converter also comprises a primary side compensation circuit arranged between the primary side circuit and the primary side winding of the isolation transformer, and a secondary side compensation circuit arranged between the secondary side winding of the isolation transformer and the secondary side circuit; wherein the content of the first and second substances,
the primary side compensation circuit comprises an inductor Lp, a capacitor Cp1 and a capacitor Cp 2; the positive output end of the primary side circuit is sequentially connected with an inductor Lp, a capacitor Cp1 and the same-name end of the primary side winding of the isolation transformer, and the capacitor Cp2 is connected in parallel between the connection point of the inductor Lp and the capacitor Cp1 and the positive output end of the primary side circuit;
the secondary side compensation circuit comprises a capacitor Cs, and the capacitor Cs is connected in series between the homonymous end of the secondary side winding of the isolation transformer and the positive input end of the secondary side circuit.
Further, when the bidirectional DC/DC converter is used for boosting, a driving signal is sent to two inverter modules in the primary circuit to implement boost control.
Further, when the bidirectional DC/DC converter is used for voltage reduction, driving signals are sent to two inversion modules in the secondary side circuit to realize voltage reduction control.
The invention also provides a working method of the bidirectional DC/DC converter,
taking an inversion module between one end of the branch of the inversion module in the primary circuit and the positive output end of the primary circuit as a first inversion module, taking an inversion module between the negative electrode of a low-voltage side power supply and the positive output end of the primary circuit as a second inversion module, taking an inversion module between one end of the branch of the inversion module in the secondary circuit and the positive output end of the secondary circuit as a third inversion module, and taking an inversion module between the negative electrode of a high-voltage side power supply and the positive output end of the secondary circuit as a fourth inversion module;
when the converter is operating in boost mode, performing the steps of:
time t0-t 1: sending a conducting drive signal to a switch tube S1 in the first inverter module and a stopping drive signal to a switch tube S2 in the second inverter module, so that the switch tube S1 is conducted and the switch tube S2 is stopped, the low-voltage side current flows through the switch tube S1, the polarity of the dotted terminal of the primary winding of the isolation transformer is positive, the polarity of the unlike terminal is negative, the polarity of the dotted terminal of the secondary winding is positive, the polarity of the unlike terminal is negative, and the high-voltage side current is half-wave rectified by a diode Ds3 in the third inverter module to provide electric energy for a high-voltage load;
time t1-t 2: the switch tube S1 and the switch tube S2 are both cut off; the low-voltage side is provided with electric energy by two capacitors in a capacitor branch of the primary circuit, the voltage polarity of the winding of the isolation transformer is unchanged, the high-voltage side rectifier diode Ds3 works, and the high-voltage side electric energy is provided after Ds3 half-wave rectification;
time t2-t 3: the switch tube S2 is switched on, the switch tube S1 is switched off, the low-voltage side current flows through the switch tube S2, the polarity of the dotted terminal of the primary winding of the isolation transformer is negative, the polarity of the dotted terminal is positive, the polarity of the dotted terminal of the secondary winding is negative, the polarity of the dotted terminal of the secondary winding is positive, and the high-voltage side current provides electric energy for a high-voltage load after half-wave rectification through a diode Ds4 in the fourth inverse transformation module;
time t3-t 4: the switching tubes S1 and S2 are both cut off; the low-voltage side is provided with electric energy by two capacitors in a capacitor branch of the primary circuit, the voltage polarity of the isolation transformer winding is unchanged, the high-voltage side rectifier diode Ds4 works, and the high-voltage side electric energy is provided after Ds4 half-wave rectification.
On the basis of the scheme, the invention is further improved as follows:
further, when the converter operates in a buck mode, the following steps are performed:
time t0-t 1: sending a conducting drive signal to a switch tube S3 in the third inverter module and a stopping drive signal to a switch tube S4 in the fourth inverter module, so that the switch tube S3 is conducted and the switch tube S4 is stopped, the high-voltage side current flows through the switch tube S3, the polarity of the dotted terminal of the secondary winding of the isolation transformer is positive, the polarity of the unlike terminal is negative, the polarity of the dotted terminal of the primary winding is positive, the polarity of the unlike terminal is negative, and the low-voltage side current is half-wave rectified by a diode Ds1 in the first inverter module to provide electric energy for a low-voltage load;
time t1-t 2: the switch tube S3 and the switch tube S4 are both cut off; the high-voltage side is provided with electric energy by two capacitors in a capacitor branch circuit of the secondary side circuit, the voltage polarity of the winding of the isolation transformer is unchanged, the low-voltage side rectifier diode Ds1 works, and the electric energy of the low-voltage side is provided after the half-wave rectification of Ds 1;
time t2-t 3: the switch tube S4 is switched on, the switch tube S3 is switched off, the high-voltage side current flows through the switch tube S4, the polarity of the dotted terminal of the secondary winding of the isolation transformer is negative, the polarity of the dotted terminal is positive, the polarity of the dotted terminal of the primary winding is negative, the polarity of the dotted terminal of the primary winding is positive, and the low-voltage side current provides electric energy for a low-voltage load after half-wave rectification through a diode Ds2 in the second inverter module;
time t3-t 4: the switch tube S3 and the switch tube S4 are both cut off; the high-voltage side is provided with electric energy by two capacitors in a capacitor branch circuit of the secondary side circuit, the voltage polarity of the winding of the isolation transformer is unchanged, the low-voltage side rectifier diode Ds2 works, and the electric energy of the low-voltage side is provided after the half-wave rectification of the Ds 2.
The invention has the following beneficial effects:
the original secondary sides of the bidirectional DC/DC converter provided by the invention are only provided with two inversion modules, and the functions of the bidirectional DC/DC converter can be realized through the cooperation of the two inversion modules and the two capacitors. The circuit structure, the working principle and the driving signals required by the inverter circuit of the converter are obviously different from the converter with four inverter modules in the prior art on the primary side and the secondary side, and cannot be obtained by improving the converter in the prior art. The novel bidirectional DC/DC converter provided by the embodiment has the advantages of simple circuit structure, low switching loss and simple control circuit. Compared with an isolation type circuit applied in the conventional ICPT system, the circuit has the advantages of high working efficiency, less heat generation and larger advantages in volume and weight.
The leakage inductance compensation circuit is improved, compared with the traditional low-order compensation topology, the improved leakage inductance compensation circuit is insensitive to component parameter deviation, input and output gains can be adjusted by adjusting the compensation inductance, ZVS soft switching is easy to realize, and therefore high efficiency is achieved when constant voltage output is obtained. The compensation circuit can reduce the values of the compensation inductance LP and the capacitance CP2 by configuring the compensation capacitor CP1, thereby reducing the circuit volume, and in addition, the compensation circuit can also isolate direct current to prevent the magnetic core from being saturated. And the circuit gain can be adjusted by using the compensation inductor LP and is not influenced by the load. The defects that the traditional low-order compensation topology cannot adjust input and output gains, and a DC-DC conversion link is added at a later stage to obtain appointed output are overcome.
The invention also provides a working method of the bidirectional DC/DC converter, and the method can realize the bidirectional voltage conversion function of the bidirectional DC/DC converter. The control logic is simple, the realization is easy, and the working requirements of the bidirectional DC/DC converter can be met.
In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
Fig. 1 is a structural view of a bidirectional DC/DC converter in embodiment 1 of the present invention;
FIG. 2 is a diagram of four classical low-order compensation structures in the prior art;
fig. 3 is a schematic structural diagram of a bidirectional DC/DC converter including a leakage inductance compensation circuit in embodiment 1 of the present invention;
fig. 4 is a structural diagram of a bidirectional DC/DC converter including a leakage inductance compensation circuit according to embodiment 1 of the present invention;
fig. 5 shows the driving signal of the low-voltage side switching tube in the boost mode of the bidirectional DC/DC converter in embodiment 2 of the present invention;
fig. 6 shows the driving signal of the high-side switching tube in the buck mode of the bidirectional DC/DC converter in embodiment 2 of the present invention;
FIG. 7 is an equivalent circuit diagram of the primitive compensation circuit in embodiment 3 of the present invention;
fig. 8 is a graph showing the variation trend of the impedance angle theta in embodiment 3 of the present invention, wherein fig. 8a) is a graph showing the variation of theta with the parameters α and β, and fig. 8b) is an enlarged detail view of fig. 8a) centered at 0;
fig. 9 is an impedance angle determined in example 3 of the present invention.
Detailed Description
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.
Example 1
The invention discloses a specific embodiment, which discloses a bidirectional DC/DC converter, the structure diagram is shown in figure 1, and the converter comprises a primary side circuit, an isolation transformer and a secondary side circuit; the primary side circuit and the secondary side circuit respectively comprise an inversion module branch and a capacitor branch, the inversion module branch comprises two inversion modules which are connected in series, and the capacitor branch comprises two capacitors which are connected in series; one end of the inversion module branch is connected with one end of the capacitor branch; the positive output end of the primary side circuit or the secondary side circuit is led out from the connection position of the two inversion modules, and the negative output end of the primary side circuit or the secondary side circuit is led out from the connection position of the two capacitors; the low-voltage side power supply VLPositive output of the positive electrode and the primary side circuitThe output end is connected, and the negative electrode is connected with the other end of the inversion module branch and the other end of the capacitor branch in the primary circuit; the high-voltage side power supply VHThe positive pole is connected with one end of the inversion module branch, and the negative pole is connected with the other end of the inversion module branch and the other end of the capacitor branch in the primary circuit.
In implementation, the positive output end and the negative output end of the primary side circuit are respectively connected with the homonymous end and the synonym end of the primary side winding of the isolation transformer, and the positive output end and the negative output end of the secondary side circuit are respectively connected with the homonymous end and the synonym end of the secondary side winding of the isolation transformer. When the bidirectional DC/DC converter is used for boosting, driving signals are sent to two inversion modules in the primary side circuit to realize boosting control; when the bidirectional DC/DC converter is used for voltage reduction, driving signals are sent to two inversion modules in the secondary side circuit to realize voltage reduction control.
Compared with the prior art, the bidirectional DC/DC converter provided by the embodiment has the advantages that the original secondary side is only provided with the two inversion modules, and the functions of the bidirectional DC/DC converter can be realized through the cooperation of the two inversion modules and the two capacitors. The circuit structure, the working principle and the driving signals required by the inverter circuit of the converter are obviously different from the converter with four inverter modules in the prior art on the primary side and the secondary side, and cannot be obtained by improving the converter in the prior art. The novel bidirectional DC/DC converter provided by the embodiment has the advantages of simple circuit structure, low switching loss and simple control circuit. Compared with an isolation type circuit applied in the conventional ICPT system, the circuit has the advantages of high working efficiency, less heat generation and larger advantages in volume and weight.
Preferably, the inversion modules in the primary side circuit and the secondary side circuit have the same structure, and both comprise: a switch tube (namely a field effect tube), a diode and a capacitor; and a diode is reversely connected in parallel between the drain electrode and the source electrode of the switching tube, and the capacitor is connected in parallel. The grid electrode of the switching tube is used for receiving the driving signal.
Preferably, the primary side circuit further includes an inductor L and a capacitor CL, the capacitor CL is connected in parallel to two sides of the low-voltage side power supply, and the inductor L is connected in series between the positive electrode of the low-voltage side power supply and the positive output end of the primary side circuit.
Preferably, the isolation transformer is a loosely coupled transformer.
Preferably, the bidirectional DC/DC converter further includes a primary side compensation circuit disposed between the primary side circuit and the primary side winding of the isolation transformer, and a secondary side compensation circuit disposed between the secondary side winding of the isolation transformer and the secondary side circuit. The existing leakage inductance compensation circuit comprises a primary side and a secondary side, and the leakage inductance of the primary side and the secondary side of the isolation transformer is compensated respectively. Four compensation topologies that are currently in common use are shown in fig. 2. Although the four classical low-order compensation topologies have simple forms, the four classical low-order compensation topologies have the defects that the circuit sensitivity of the resonant element is too high and the input and output gains are not adjustable, and particularly the leakage inductance compensation voltage type S/S topology has low circuit efficiency due to the fact that the inductance zone is too deep and large reactive power exists. In order to solve the above problem, the present embodiment further improves the existing leakage inductance compensation circuit, specifically:
the primary side compensation circuit comprises an inductor Lp, a capacitor Cp1 and a capacitor Cp 2; the positive output end of the primary side circuit is sequentially connected with an inductor Lp, a capacitor Cp1 and the same-name end of the primary side winding of the isolation transformer, and the capacitor Cp2 is connected in parallel between the connection point of the inductor Lp and the capacitor Cp1 and the positive output end of the primary side circuit; the secondary side compensation circuit comprises a capacitor Cs, and the capacitor Cs is connected in series between the homonymous end of the secondary side winding of the isolation transformer and the positive input end of the secondary side circuit. Fig. 3 shows a schematic diagram of a bidirectional DC/DC converter including a leakage inductance compensation circuit, and fig. 4 shows a schematic diagram of a bidirectional DC/DC converter including a leakage inductance compensation circuit.
Compared with the traditional low-order compensation topology, the leakage inductance compensation circuit has the advantages that the compensation topology is insensitive to parameter deviation of components, input and output gains can be adjusted by adjusting the compensation inductance, ZVS soft switching is easy to realize, and therefore high efficiency is achieved when constant voltage output is obtained. The compensation circuit can reduce the values of the compensation inductance LP and the capacitance CP2 by configuring the compensation capacitor CP1, thereby reducing the circuit volume, and in addition, the compensation circuit can also isolate direct current to prevent the magnetic core from being saturated. And the circuit gain can be adjusted by using the compensation inductor LP and is not influenced by the load. The defects that the traditional low-order compensation topology cannot adjust input and output gains, and a DC-DC conversion link is added at a later stage to obtain appointed output are overcome.
Example 2
In another embodiment of the invention, an operating method of the bidirectional DC/DC converter is also provided. The method comprises the steps of taking an inversion module between one end of an inversion module branch in a primary side circuit and a positive output end of the primary side circuit as a first inversion module, taking an inversion module between a negative electrode of a low-voltage side power supply and the positive output end of the primary side circuit as a second inversion module, taking an inversion module between one end of the inversion module branch in a secondary side circuit and the positive output end of the secondary side circuit as a third inversion module, and taking an inversion module between the negative electrode of a high-voltage side power supply and the positive output end of the secondary side circuit as a fourth inversion module.
When the transformer works in a boosting mode, the following steps are executed:
time t0-t 1: a switch tube S1 in a first inversion module in a primary side circuit is switched on, a switch tube S2 in a second inversion module is switched off, low-voltage side current flows through the switch tube S1, the polarity of the dotted terminal of a primary side winding of the isolation transformer is positive, the polarity of the unlike terminal is negative, the polarity of the dotted terminal of a secondary side winding is positive, the polarity of the unlike terminal is negative, and high-voltage side current is half-wave rectified by a diode Ds3 in the third inversion module to provide electric energy for a high-voltage load; at the same time, the charging of the two capacitors (C1, C2) in the capacitive branch of the primary circuit is achieved.
time t1-t 2: switching tubes S1 and S2 enter a control dead zone; the low-voltage side is provided with electric energy by half-bridge capacitors C1 and C2, the voltage polarity of an isolation transformer winding is unchanged, a high-voltage side rectifier diode Ds3 works, and the high-voltage side electric energy is provided after Ds3 half-wave rectification;
time t2-t 3: the switching tube S2 is switched on, the switching tube S1 is switched off, the low-voltage side current flows through the switching tube S2, the polarity of the dotted terminal of the primary winding of the isolation transformer is negative, the polarity of the dotted terminal is positive, the polarity of the dotted terminal of the secondary winding is negative, the polarity of the dotted terminal of the secondary winding is positive, and the high-voltage side current provides electric energy for a high-voltage load after half-wave rectification through a diode Ds4 in the fourth inverse transformer module;
time t3-t 4: switching tubes S1 and S2 enter a control dead zone; the low-voltage side is provided with electric energy by half-bridge capacitors C1 and C2, the voltage polarity of the winding of the isolation transformer is unchanged, and the high-voltage side rectifier diode Ds4 works and provides high-voltage side electric energy after Ds4 half-wave rectification.
Fig. 5 shows driving signals of the low-voltage side switching tube in the boost mode of the bidirectional DC/DC converter during the boost mode operation.
When the circuit works in a voltage reduction mode, the following steps are executed:
time t0-t 1: a switching tube S3 in a third inversion module in the secondary side circuit is switched on, a switching tube S4 in a fourth inversion module is switched off, high-voltage side current flows through the switching tube S3, the polarity of the dotted terminal of a secondary side winding of the isolation transformer is positive, the polarity of the unlike terminal is negative, the polarity of the dotted terminal of a primary side winding is positive, the polarity of the unlike terminal is negative, and low-voltage side current is half-wave rectified by a diode Ds1 in the first inversion module to provide electric energy for a low-voltage load; at the same time, the charging of the two capacitors (C3, C4) in the capacitive branch of the secondary circuit is achieved.
time t1-t 2: switching tubes S3 and S4 enter a control dead zone; the high-voltage side is provided with electric energy by half-bridge capacitors C3 and C4, the voltage polarity of an isolation transformer winding is unchanged, a low-voltage side rectifier diode Ds1 works, and the electric energy of the low-voltage side is provided after half-wave rectification of Ds 1;
time t2-t 3: the switch tube S4 is switched on, the switch tube S3 is switched off, the high-voltage side current flows through the switch tube S4, the polarity of the dotted terminal of the secondary winding of the isolation transformer is negative, the polarity of the dotted terminal is positive, the polarity of the dotted terminal of the primary winding is negative, the polarity of the dotted terminal of the primary winding is positive, and the low-voltage side current provides electric energy for a low-voltage load after half-wave rectification through a diode Ds2 in the second inverter module;
time t3-t 4: switching tubes S3 and S4 enter a control dead zone; the high-voltage side is provided with electric energy by capacitors C3 and C4, the voltage polarity of the winding of the isolation transformer is unchanged, the low-voltage side rectifier diode Ds2 works, and the electric energy of the low-voltage side is provided after half-wave rectification of Ds 2.
Fig. 6 shows driving signals of the high-voltage side switching tube in the boost mode of the bidirectional DC/DC converter during the buck mode operation.
The working process can realize the bidirectional voltage conversion function of the bidirectional DC/DC converter. The control logic is simple, the realization is easy, and the working requirements of the bidirectional DC/DC converter can be met.
Example 3
Before the selection of the compensation circuit parameters, the equivalent processing is firstly performed on the primary side compensation circuit of the circuit diagram shown in fig. 2, and the equivalent circuit diagram of the primary side compensation circuit is shown in fig. 7. Wherein L1 is the primary inductance of the loosely coupled transformer, and the load R is the equivalent load. According to FIG. 7, the load side current I1 and the input impedance of the circuit can be calculated as
According to equation (1), the circuit amplitude | I1| and the impedance angle θ at the load side of the circuit can be calculated, and the result is shown in equation (2). Wherein ZL is 8 RL/pi 2, and UAB is the fundamental wave of two Boost inverter circuit output interchange square wave.
By substituting the calculated circuit parameters into equation (2), the impedance angle of the circuit can be calculated.
In order to operate the circuit in the soft switching state (the soft switching state is beneficial to improving the working efficiency of the circuit and reducing the switching loss), the circuit needs to be operated in the weak inductance state, namely, the impedance angle theta is larger than 0. To simplify the selection of circuit parameters, Matlab-assisted parameter selection is used here, taking RL ═ 160 Ω and VH ═ 400V as examples.
The graph of the variation of theta with the parameters α and β according to the rated conditions is shown in fig. 8a), the theta is taken as 0 as the center, the detailed enlargement of fig. 8a) is made, and the detail is shown in fig. 8b), according to fig. 8, the proper impedance angle theta can be selected from the graph to determine the parameters α and β, and finally the unbalance parameter of the circuit is determined.
When the circuit works in a Boost mode and a Buck mode, the input voltage of a T-type resonant link of the circuit is 400V according to the analysis of the foregoing, so that the expression of the equivalent direct current resistance of the circuit α and β under the full-load condition is shown in formula (3), wherein ω s is the switching angular frequency of the resonant link, and the magnitude of ω s is related to the switching frequency fs of the circuit, namely ω s is 2 π fs.
The corresponding impedance angle is found (α) in fig. 8, here (1,0.875) and (0.875,1) for example, and the results are shown in fig. 9.
As can be seen from fig. 9, in the two choices (α), the impedance angle θ is 56.27 ° and θ is 15.29 °, so that the circuit operates in the inductive condition, and the input current lags behind the voltage, so that the circuit can reach the ZVS condition.
Those skilled in the art will appreciate that all or part of the flow of the method implementing the above embodiments may be implemented by a computer program, which is stored in a computer readable storage medium, to instruct related hardware. The computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (10)
1. A bidirectional DC/DC converter is characterized by comprising a primary side circuit, an isolation transformer and a secondary side circuit; wherein the content of the first and second substances,
the primary side circuit and the secondary side circuit both comprise an inversion module branch and a capacitor branch, the inversion module branch comprises two inversion modules which are connected in series, and the capacitor branch comprises two capacitors which are connected in series; one end of the inversion module branch is connected with one end of the capacitor branch; the positive output end of the primary side circuit or the secondary side circuit is led out from the connection position of the two inversion modules, and the negative output end of the primary side circuit or the secondary side circuit is led out from the connection position of the two capacitors;
the positive electrode of the low-voltage side power supply is connected with the positive output end of the primary side circuit, and the negative electrode of the low-voltage side power supply is connected with the other end of the inversion module branch circuit and the other end of the capacitor branch circuit in the primary side circuit;
and the anode of the high-voltage side power supply is connected with one end of the inversion module branch, and the cathode of the high-voltage side power supply is connected with the other end of the inversion module branch and the other end of the capacitor branch in the primary side circuit.
2. The bi-directional DC/DC converter of claim 1, wherein the inverting modules in the primary circuit and the secondary circuit are identical in structure and each comprise: a switch tube, a diode and a capacitor; and a diode is reversely connected in parallel between the drain electrode and the source electrode of the switching tube, and the capacitor is connected in parallel.
3. The bi-directional DC/DC converter of claim 2, wherein the gate of the switching tube is configured to receive a driving signal.
4. The bi-directional DC/DC converter of claim 1, wherein the primary circuit further comprises an inductor L and a capacitor CL, the capacitor CL being connected in parallel to both sides of the low-voltage side power supply, the inductor L being connected in series between the positive terminal of the low-voltage side power supply and the positive output terminal of the primary circuit.
5. The bi-directional DC/DC converter according to claim 1, wherein the isolation transformer is a loosely coupled transformer.
6. The bi-directional DC/DC converter of claim 1,
the bidirectional DC/DC converter also comprises a primary side compensation circuit arranged between the primary side circuit and the primary side winding of the isolation transformer and a secondary side compensation circuit arranged between the secondary side winding of the isolation transformer and the secondary side circuit; wherein the content of the first and second substances,
the primary side compensation circuit comprises an inductor Lp, a capacitor Cp1 and a capacitor Cp 2; the positive output end of the primary side circuit is sequentially connected with an inductor Lp, a capacitor Cp1 and the same-name end of the primary side winding of the isolation transformer, and the capacitor Cp2 is connected in parallel between the connection point of the inductor Lp and the capacitor Cp1 and the positive output end of the primary side circuit;
the secondary side compensation circuit comprises a capacitor Cs, and the capacitor Cs is connected in series between the homonymous end of the secondary side winding of the isolation transformer and the positive input end of the secondary side circuit.
7. A bidirectional DC/DC converter as recited in any of claims 1-6, characterized in that when the bidirectional DC/DC converter is used for boosting, driving signals are sent to two inverter modules in the primary circuit for implementing boosting control.
8. The bidirectional DC/DC converter according to any of claims 1-6, wherein when the bidirectional DC/DC converter is used for buck, a driving signal is sent to two inverting modules in the secondary side circuit for implementing buck control.
9. A method for operating a bidirectional DC/DC converter according to any one of claims 1 to 8, wherein an inverter module between one end of a branch of the inverter module in a primary circuit and a positive output terminal of the primary circuit is used as a first inverter module, an inverter module between a negative electrode of a low-voltage side power supply and the positive output terminal of the primary circuit is used as a second inverter module, an inverter module between one end of a branch of the inverter module in a secondary circuit and the positive output terminal of the secondary circuit is used as a third inverter module, and an inverter module between a negative electrode of a high-voltage side power supply and the positive output terminal of the secondary circuit is used as a fourth inverter module;
when the converter is operating in boost mode, performing the steps of:
time t0-t 1: sending a conducting drive signal to a switch tube S1 in the first inverter module and a stopping drive signal to a switch tube S2 in the second inverter module, so that the switch tube S1 is conducted and the switch tube S2 is stopped, the low-voltage side current flows through the switch tube S1, the polarity of the dotted terminal of the primary winding of the isolation transformer is positive, the polarity of the unlike terminal is negative, the polarity of the dotted terminal of the secondary winding is positive, the polarity of the unlike terminal is negative, and the high-voltage side current is half-wave rectified by a diode Ds3 in the third inverter module to provide electric energy for a high-voltage load;
time t1-t 2: the switch tube S1 and the switch tube S2 are both cut off; the low-voltage side is provided with electric energy by two capacitors in a capacitor branch of the primary circuit, the voltage polarity of the winding of the isolation transformer is unchanged, the high-voltage side rectifier diode Ds3 works, and the high-voltage side electric energy is provided after Ds3 half-wave rectification;
time t2-t 3: the switch tube S2 is switched on, the switch tube S1 is switched off, the low-voltage side current flows through the switch tube S2, the polarity of the dotted terminal of the primary winding of the isolation transformer is negative, the polarity of the dotted terminal is positive, the polarity of the dotted terminal of the secondary winding is negative, the polarity of the dotted terminal of the secondary winding is positive, and the high-voltage side current provides electric energy for a high-voltage load after half-wave rectification through a diode Ds4 in the fourth inverse transformation module;
time t3-t 4: the switching tubes S1 and S2 are both cut off; the low-voltage side is provided with electric energy by two capacitors in a capacitor branch of the primary circuit, the voltage polarity of the isolation transformer winding is unchanged, the high-voltage side rectifier diode Ds4 works, and the high-voltage side electric energy is provided after Ds4 half-wave rectification.
10. Method of operating a bidirectional DC/DC converter according to claim 9, characterized in that when the converter is operating in buck mode, the following steps are performed:
time t0-t 1: sending a conducting drive signal to a switch tube S3 in the third inverter module and a stopping drive signal to a switch tube S4 in the fourth inverter module, so that the switch tube S3 is conducted and the switch tube S4 is stopped, the high-voltage side current flows through the switch tube S3, the polarity of the dotted terminal of the secondary winding of the isolation transformer is positive, the polarity of the unlike terminal is negative, the polarity of the dotted terminal of the primary winding is positive, the polarity of the unlike terminal is negative, and the low-voltage side current is half-wave rectified by a diode Ds1 in the first inverter module to provide electric energy for a low-voltage load;
time t1-t 2: the switch tube S3 and the switch tube S4 are both cut off; the high-voltage side is provided with electric energy by two capacitors in a capacitor branch circuit of the secondary side circuit, the voltage polarity of the winding of the isolation transformer is unchanged, the low-voltage side rectifier diode Ds1 works, and the electric energy of the low-voltage side is provided after the half-wave rectification of Ds 1;
time t2-t 3: the switch tube S4 is switched on, the switch tube S3 is switched off, the high-voltage side current flows through the switch tube S4, the polarity of the dotted terminal of the secondary winding of the isolation transformer is negative, the polarity of the dotted terminal is positive, the polarity of the dotted terminal of the primary winding is negative, the polarity of the dotted terminal of the primary winding is positive, and the low-voltage side current provides electric energy for a low-voltage load after half-wave rectification through a diode Ds2 in the second inverter module;
time t3-t 4: the switch tube S3 and the switch tube S4 are both cut off; the high-voltage side is provided with electric energy by two capacitors in a capacitor branch circuit of the secondary side circuit, the voltage polarity of the winding of the isolation transformer is unchanged, the low-voltage side rectifier diode Ds2 works, and the electric energy of the low-voltage side is provided after the half-wave rectification of the Ds 2.
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