CN112615544B - Full soft switch AC/DC input solid-state transformer circuit and modulation method thereof - Google Patents
Full soft switch AC/DC input solid-state transformer circuit and modulation method thereof Download PDFInfo
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- CN112615544B CN112615544B CN202011412376.5A CN202011412376A CN112615544B CN 112615544 B CN112615544 B CN 112615544B CN 202011412376 A CN202011412376 A CN 202011412376A CN 112615544 B CN112615544 B CN 112615544B
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Classifications
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
- H02J1/102—Parallel operation of dc sources being switching converters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
- Inverter Devices (AREA)
Abstract
The application discloses an all-soft switch alternating current-direct current input solid-state transformer circuit and a modulation method thereof. The circuit comprises input filter inductors, n front-stage soft switching circuits and n rear-stage isolated DC-DC converters, wherein the output end of each front-stage soft switching circuit is connected with the input end of each rear-stage isolated DC-DC converter to form a sub-module circuit, the n sub-module circuits are combined in a mode of input series connection and output parallel connection, the input end of each sub-module circuit is connected into a medium-voltage alternating-current or direct-current power grid through the input filter inductors, and the output end of each sub-module circuit is connected with a low-voltage direct-current power grid or load; the modulation method is that the front-stage soft switching circuit carries out SPWM-based soft switching modulation or PWM-based soft switching modulation according to the AC/DC characteristics of the input grid voltage, the rear-stage isolated DC-DC converter adopts PWM modulation, and when modulating, the carriers of the n front-stage soft switching circuits have certain phase shift, and the carriers of the n rear-stage isolated DC-DC converters also have certain phase shift.
Description
Technical Field
The application belongs to the technical field of power electronics, relates to a solid-state transformer and soft switching technology, and particularly relates to a full soft switching alternating current-direct current input solid-state transformer circuit and a modulation method thereof.
Background
With the development of power electronics technology, the solid-state transformer is widely concerned, and besides the traditional transformer isolation and voltage rising and falling functions, the solid-state transformer integrates the functions of reactive power regulation, power control, harmonic suppression, fault protection and the like of a power grid; in addition, the solid-state transformer can greatly reduce the volume and weight of the transformer and improve the power density; moreover, the voltage withstand level and the power capacity of the solid-state transformer can be greatly improved by adopting a modularized structure, and the circuit design flow is simplified.
However, at present, there are few researches about a general-purpose solid-state transformer for ac/dc power grid input, and most of two-stage solid-state transformers have their front stages operated under hard switching conditions, which does not utilize the improvement of efficiency and power density of the solid-state transformer, so it is necessary to provide a general-purpose solid-state transformer for ac/dc power grid input capable of realizing all soft switching.
Disclosure of Invention
Aiming at the problems in the prior art, the application aims to provide a solid-state transformer circuit which reduces the switching loss of a front-stage circuit and realizes full soft switching and is universal for AC/DC input and a modulation method thereof.
The application is realized by adopting the following technical scheme:
in one aspect of the application, an all-soft-switching AC/DC input solid-state transformer circuit is provided, which comprises an input filter inductor, n identical pre-stage soft-switching circuits and n identical post-stage isolated DC-DC converters.
The input ports are connected with the input filter inductance in series and then connected into a medium-voltage alternating current or direct current power grid; the direct current output ends of the n post-stage isolated DC-DC converters are connected in parallel to form an output port, and the output port is connected with a low-voltage direct current power grid or a load; the direct current output end of each front-stage soft switching circuit is respectively connected with the direct current input end of a rear-stage isolated DC-DC converter to jointly form a sub-module circuit, and n sub-module circuits are formed in a conformal manner.
In the above technical solution, further, the pre-stage soft switching circuit includes a first full-bridge circuit, a first auxiliary circuit, and a first output capacitor; the rear-stage isolation type DC-DC converter comprises a second full-bridge circuit, a first LC resonance circuit, a first transformer, a third full-bridge circuit and a second output capacitor; the first full-bridge circuit, the second full-bridge circuit and the third full-bridge circuit all comprise two groups of bridge arms, the two groups of bridge arms of the first full-bridge circuit are respectively composed of two series full-control switching tubes which comprise anti-parallel diodes and resonance capacitors, and the two groups of bridge arms of the second full-bridge circuit and the third full-bridge circuit are respectively composed of two series full-control switching tubes which comprise anti-parallel diodes; two upper switching tube drains of two groups of bridge arms of each full-bridge circuit are connected, and two lower switching tube sources are connected; the middle points of two bridge arms of the first full-bridge circuit form an alternating current-direct current input end of the front-stage soft switching circuit; a first auxiliary circuit is connected between the drain electrode of an upper switching tube of the first full-bridge circuit and the anode of the first output capacitor, and the source electrode of a lower switching tube of the first full-bridge circuit is connected with the cathode of the first output capacitor; the first auxiliary circuit is composed of a fully-controlled auxiliary switching tube comprising an anti-parallel diode and a resonant capacitor, a clamping capacitor and an auxiliary inductor; the auxiliary switching tube is connected with the clamping capacitor in series to form a series branch, and auxiliary inductors are connected in parallel at two ends of the series branch; the drain electrode of the upper switching tube and the source electrode of the lower switching tube of the second full-bridge circuit form a direct current input end of the rear-stage isolated DC-DC converter; the first LC resonance circuit is formed by connecting a resonance inductor and a resonance capacitor in series; the middle point of the bridge arm of the second full-bridge circuit is connected with the primary side of the first transformer after being connected with the first LC resonant circuit in series; the drain electrode of the upper switching tube of the third full-bridge circuit is connected with the positive electrode of the second output capacitor, and the source electrode of the lower switching tube of the third full-bridge circuit is connected with the negative electrode of the second output capacitor; the middle point of the bridge arm of the third full-bridge circuit is connected with the secondary side of the first transformer.
In another aspect of the present application, a modulation method of the full soft switch ac/DC input solid-state transformer is provided, wherein each sub-module circuit driving signal is composed of a soft switch driving signal of a preceding soft switch circuit and a driving signal of a following isolated DC-DC converter; the front-stage soft switching circuit rectifies the input alternating-current voltage by adopting SPWM (sinusoidal pulse width modulation) modulation or converts the amplitude of the input direct-current voltage by adopting PWM (pulse width modulation) modulation according to the alternating-current and direct-current characteristics of the input voltage, certain phase shift exists among carriers of n front-stage soft switching circuits during modulation, and then soft switching modulation is carried out on the basis of SPWM driving or PWM driving, so that a soft switching driving signal of the front-stage soft switching circuit is generated; the post-stage isolated DC-DC converters adopt PWM modulation, and certain phase shift exists among carriers of the n post-stage isolated DC-DC converters during modulation, so that driving signals of the post-stage isolated DC-DC converters are generated.
The above method is implemented by the following modules: the device comprises an alternating current-direct current modulation wave selection module, a front-stage PWM generation module, n identical soft switch modulation modules, a front-stage carrier generation module, a front-stage carrier phase shifting module, a rear-stage carrier generation module, a rear-stage carrier phase shifting module, a rear-stage PWM generation module and a rear-stage modulation wave generation module.
In the above technical solution, further, the ac/dc modulation wave selection module selects the ac/dc modulation wave according to the input voltage v in Outputs a corresponding modulation signal m 1 And input the front-stage PWM generation module; the front carrier generating module generates a switching period of T s1 Saw tooth wave C of (2) 1 Generating n sawtooth carriers with phase shift alpha (alpha is more than or equal to 0 degree and less than or equal to 360 degrees) after the phase shift treatment of the preceding carrier phase shift module, and inputting the sawtooth carriers into the preceding PWM generation module; the front PWM generation module modulates the signal m 1 SPWM modulation or PWM modulation is respectively carried out on the n sawtooth carriers to generate n groups of front-stage original drivers, and each group of front-stage original drivers is driven by two paths of complementary driving signals V with dead zones 1k And V is equal to 2k (1 is less than or equal to k is less than or equal to n); k-th group of front stage original driving signals V 1k 、V 2k Input current i to solid state transformer in The kth soft switch modulation module is input together to generate a group of front-stage soft switch circuit driving signals, and the n soft switch modulation modules generate n groups of front-stage soft switch driving signals which are respectively used for driving the n front-stage soft switch circuits; the back-stage carrier wave generating module generates a switching period of T s2 Triangular wave C of (2) 2 After the phase shift treatment is carried out by the carrier phase shift module of the later stage, n triangular carriers with phase shift beta (beta is more than or equal to 0 degree and less than or equal to 360 degrees) are generated and input into the PWM generation module of the later stage; the post-stage modulation wave generating module generates a post-stage modulation wave m 2 And inputting the PWM generation module of the rear stage; the post PWM generation module modulates the signal m 2 PWM modulation is respectively carried out on the N triangular carriers, n groups of post-stage driving are generated and are respectively used for driving n post-stage isolation type DC-DC converters. The alternating current-direct current modulation wave selection module comprises an input voltage judgment module, an alternating current modulation wave generation module, a direct current modulation wave generation module and a first selection switch; the alternating current modulation wave generation module and the direct current modulation wave generation module respectively generate alternating current modulation waves and direct current modulation waves and input the alternating current modulation waves and the direct current modulation waves into the first selection switch; the input voltage judging module performs the AC/DC characteristic of the input voltageThe first selection switch is judged and controlled to select proper modulation signal output, namely, alternating current modulation wave is selected when the input voltage is alternating current, and direct current modulation wave is selected when the input voltage is direct current. The soft switch modulation module comprises a first comparator, a first inverter, an input current polarity judging module, a first delay module, a first AND gate, a second delay module, a second AND gate, a first OR gate, a second selection switch, a second OR gate, a third delay module, a fourth OR gate, a fifth OR gate and a third selection switch; solid state transformer input current i in The output signal is input to the positive terminal of the first comparator and compared with zero, and the output result is used as a driving signal V gs3 Drive signal V gs3 Is inverted by a first inverter and is used as a driving signal V gs4 ；V 1k The result delayed by the first delay module is compared with V 2k Common input first AND gate generates V 3 ；V 2k The result delayed by the second delay module is compared with V 1k Common input second AND gate generates V 4 ；V 3 And V is equal to 4 Input a first OR gate to generate a pass-through signal V 5 The method comprises the steps of carrying out a first treatment on the surface of the The second selector switch selects the voltage V under the control of the input current polarity judging module 5 Input to a second or third OR gate, i.e. when i in To positive V 5 Input the second OR gate, input zero into the third OR gate, and when i in Will V when negative 5 Inputting a third OR gate, and inputting zero into the second OR gate; v (V) 1k And V is equal to 2k Respectively inputting a second or gate and a third or gate, wherein the output signals of the second or gate and the third or gate are respectively a driving signal V gs1 And V is equal to gs2 ；V gs1 、V gs2 、V gs3 、V gs4 Switching tube driving of a full-bridge circuit in a front-stage soft switching circuit of the kth sub-module circuit respectively; v (V) 2k The result delayed by the third delay module is compared with V 1k Common input fourth OR gate generates V 6 ，V 1k The result delayed by the fourth delay module is compared with V 2k Common input fifth OR gate generates V 7 The method comprises the steps of carrying out a first treatment on the surface of the The third selector switch selects V according to the control of the current polarity judging module 6 Or V 7 Front stage as kth sub-module circuitDrive signal V of auxiliary switching tube in soft switching circuit gsa I.e. when i in Selecting V for positive 6 ，i in Selecting V when negative 7 The method comprises the steps of carrying out a first treatment on the surface of the The delay time of the first delay module, the second delay module, the third delay module and the fourth delay module is respectively as follows: t (T) d1 、T d2 、T d3 And T is d4 Satisfy T d1 ＝T d2 ，T d3 ＝T d4 ，T d1 <T d3 。
The beneficial effects of the application are as follows:
by adopting the full soft switch AC/DC input solid-state transformer circuit and the modulation method thereof, the same solid-state transformer circuit can be used for AC power grid input or DC power grid input occasions; zero-voltage switching on of a front-stage circuit of the solid-state transformer can be realized, switching-on loss and reverse recovery loss of a switching tube are reduced, and the efficiency and the power density of the solid-state transformer are improved; the voltage withstand grade and the power capacity of the solid-state transformer can be improved by using a modularized design thought, and the design flow is simplified.
Drawings
FIG. 1 is a schematic diagram of the overall circuit of a full soft switching AC/DC input solid state transformer;
FIG. 2 is a circuit diagram of a pre-stage soft switching circuit in an all-soft switching AC/DC input solid-state transformer;
FIG. 3 is a circuit diagram of a post-stage isolated DC-DC converter in an all-soft-switch AC-DC input solid-state transformer;
FIG. 4 is a block diagram of a modulation method implementation of a full soft switching AC/DC input solid state transformer;
FIG. 5 is a specific implementation block diagram of an AC/DC modulation wave selection module in a modulation method implementation block diagram of an all-soft-switch AC/DC input solid-state transformer;
FIG. 6 is a block diagram of a specific implementation of a soft switch modulation module in a modulation method implementation block diagram of an all soft switch AC/DC input solid-state transformer;
FIG. 7 is a circuit diagram of a fully soft switching AC/DC input solid-state transformer when the number n of sub-modules is equal to 3;
FIG. 8 shows the number of sub-modulesNumber n is equal to 3 and input current i in Schematic diagram of driving signals of each switching tube in one switching period;
FIG. 9 shows the input current i when the number n of sub-modules is equal to 3 in A driving signal diagram of each switching tube in one switching period when the driving signal diagram is negative;
FIG. 10 shows the current i when input in Schematic of key waveforms for sub-module circuit 1 for positive in one switching cycle;
FIGS. 11 to 24 show the input current i in The equivalent circuit diagram of each stage of the submodule circuit 1 in one switching cycle is timed.
Detailed Description
The present application will be described in detail with reference to the accompanying drawings.
Referring to fig. 1, an all-soft-switching ac/DC input solid-state transformer circuit includes an input filter inductance 100, n identical pre-stage soft-switching circuits 200, and n identical post-stage isolated DC-DC converters 300; the ac/dc input ends of the n preceding soft switch circuits 200 are connected in series to form an input port, and the input port is connected in series with the input filter inductor 100 and then connected to a medium-voltage ac or dc power grid; the direct current output ends of the n post-stage isolated DC-DC converters 300 are connected in parallel to form an output port, and the output port is connected with a low-voltage direct current power grid or a load; the DC output end of each front-stage soft switching circuit 200 is connected to the DC input end of a rear-stage isolated DC-DC converter 300, respectively, to form a sub-module circuit together, and n sub-module circuits are formed together.
Referring to fig. 2, the pre-stage soft switching circuit 200 includes a first full-bridge circuit 201, a first auxiliary circuit 202, and a first output capacitor 203; two groups of bridge arms of the first full-bridge circuit 201 are composed of two series full-control switching tubes which comprise anti-parallel diodes and resonance capacitors, two upper switching tube drains of the two groups of bridge arms are connected, and two lower switching tube sources are connected; the middle points of two bridge arms of the first full-bridge circuit 201 form an alternating current/direct current input end of the front-stage soft switching circuit 200; the first auxiliary circuit 202 is connected between the drain electrode of the upper switching tube of the first full-bridge circuit 201 and the positive electrode of the first output capacitor 203, and the source electrode of the lower switching tube of the first full-bridge circuit 201 is connected with the negative electrode of the first output capacitor 203; the first auxiliary circuit 202 is composed of an auxiliary switching tube 208, a clamping capacitor 209 and an auxiliary inductor 210, wherein the auxiliary switching tube 208 comprises an antiparallel diode and a resonant capacitor; the auxiliary switching tube 208 is connected in series with the clamp capacitor 209 to form a series branch, and an auxiliary inductor 210 is connected in parallel across the series branch.
Referring to fig. 3, the rear-stage isolated DC-DC converter 300 includes a second full-bridge circuit 301, a first LC resonant circuit 302, a first transformer 303, a third full-bridge circuit 304, and a second output capacitor 305. The two groups of bridge arms of the second full-bridge circuit 301 and the third full-bridge circuit 304 are respectively composed of two series full-control switching tubes which comprise anti-parallel diodes, the drains of the two upper switching tubes of the two groups of bridge arms of each full-bridge circuit are connected, and the sources of the two lower switching tubes are connected. The drain electrode of the upper switching tube and the source electrode of the lower switching tube of the second full-bridge circuit 301 form a direct current input end of the rear-stage isolated DC-DC converter 300; the first LC resonant circuit 302 is formed by connecting a resonant inductor 310 and a resonant capacitor 311 in series; the bridge arm midpoint of the second full-bridge circuit 301 is connected in series with the first LC resonant circuit 302 and then connected to the primary side of the first transformer 303; the drain electrode of the upper switching tube of the third full-bridge circuit 304 is connected with the positive electrode of the second output capacitor 305, and the source electrode of the lower switching tube of the third full-bridge circuit 304 is connected with the negative electrode of the second output capacitor 305; the bridge arm midpoint of the third full bridge circuit 304 is connected to the secondary side of the first transformer 303.
Referring to fig. 4, a modulation method of an all-soft-switching ac/dc input solid-state transformer includes an ac/dc modulation wave selection module 400, a front PWM generation module 500, n identical soft-switching modulation modules 600, a front carrier generation module 700, a front carrier phase shift module 800, a rear carrier generation module 900, a rear carrier phase shift module 1000, a rear PWM generation module 1100 and a rear modulation wave generation module 1200; the AC/DC modulation wave selection module 400 selects the modulation wave according to the input voltage v in Outputs a corresponding modulation signal m 1 And input to the pre-stage PWM generation module 500; the pre-carrier generation module 700 generates a switching period T s1 Saw tooth wave C of (2) 1 And generates n sawtooth carriers with phase shift alpha (alpha is more than or equal to 0 degree and less than or equal to 360 degrees) after the phase shift treatment of the preceding carrier phase shift module 800The wave is input into the pre-stage PWM generation module 500; the front PWM generation module 500 modulates the signal m 1 SPWM modulation or PWM modulation is respectively carried out on the n sawtooth carriers to generate n groups of front-stage original drivers, and each group of front-stage original drivers is driven by two paths of complementary driving signals V with dead zones 1k And V is equal to 2k (1 is less than or equal to k is less than or equal to n); k-th group of front stage original driving signals V 1k 、V 2k Input current i to solid state transformer in The kth soft switch modulation module 600 is input together to generate a group of front-stage soft switch circuit driving signals, and the n soft switch modulation modules 600 generate n groups of front-stage soft switch driving signals which are respectively used for driving the n front-stage soft switch circuits 200; the back-end carrier generation module 900 generates a switching period T s2 Triangular wave C of (2) 2 And after the phase shift treatment by the carrier phase shift module 1000 of the later stage, n triangular carriers with phase shift beta (beta is more than or equal to 0 degree and less than or equal to 360 degrees) are generated and input into the PWM generation module 1100 of the later stage; the post-stage modulated wave generation module 1200 generates a post-stage modulated wave m 2 And input to the post PWM generation module 1100; the post-stage PWM generation module 1100 modulates the signal m 2 PWM modulation is performed with n triangular carriers respectively, generating n sets of back stage driving for driving n back stage isolated DC-DC converters 300 respectively.
Referring to fig. 5, the ac/dc modulated wave selecting module 400 includes an input voltage judging module 401, an ac modulated wave generating module 402, a dc modulated wave generating module 403, and a first selecting switch 404; the ac modulated wave generating module 402 and the dc modulated wave generating module 403 respectively generate an ac modulated wave and a dc modulated wave and input the ac modulated wave and the dc modulated wave to the first selection switch 404; the input voltage determining module 401 determines the ac/dc characteristics of the input voltage and controls the first selecting switch 404 to select a suitable modulation signal for outputting, that is, to select an ac modulation wave when the input voltage is ac and to select a dc modulation wave when the input voltage is dc.
Referring to fig. 6, the soft switch modulation module 600 includes a first comparator 601, a first inverter 602, an input current polarity determination module 603, a first delay module 604, a first and gate 605, a second delay module 606, a second and gate 607, a first or gate 608, a second selection switch 609, a second or gate 610, a third or gate 611, and a third delayA module 612, a fourth delay module 613, a fourth or gate 614, a fifth or gate 615, and a third select switch 616; solid state transformer input current i in The positive terminal of the first comparator 601 is input and compared with zero, and the output result is used as a driving signal V gs3 Drive signal V gs3 Is inverted by the first inverter 602 and is used as a driving signal V gs4 ；V 1k The result delayed by the first delay module 604 is compared with V 2k Common input first AND gate 605 generates V 3 ；V 2k The result delayed by the second delay module 606 is compared with V 1k Common input to the second AND gate 607 generates V 4 ；V 3 And V is equal to 4 Input first OR gate 608 generates pass-through signal V 5 The method comprises the steps of carrying out a first treatment on the surface of the The second selection switch 609 selects V under the control of the input current polarity determination module 603 5 Input to the second OR gate 610 or the third OR gate 611, i.e. when i in To positive V 5 Input to the second OR gate 610, zero is input to the third OR gate 611, and when i in Will V when negative 5 A third or gate 611 is input, and zero is input to the second or gate 610; v (V) 1k And V is equal to 2k The second or gate 610 and the third or gate 611 are respectively inputted, and the output signals of the second or gate 610 and the third or gate 611 are respectively the driving signal V gs1 And V is equal to gs2 ；V gs1 、V gs2 、V gs3 、V gs4 The driving signals are respectively the driving signals of the full-bridge circuit switching tubes of the front-stage soft switching circuits in the kth sub-module circuit; v (V) 2k The result delayed by the third delay module 612 is then compared with V 1k Common input fourth OR gate 614 generates V 6 ，V 1k The result delayed by the fourth delay module 613 is then compared with V 2k Common input fifth OR gate 615 generates V 7 The method comprises the steps of carrying out a first treatment on the surface of the The third selection switch 616 selects V according to the control of the current polarity determination module 603 6 Or V 7 Drive signal V for auxiliary switching tube of front stage soft switching circuit in kth sub-module circuit gsa I.e. when i in Selecting V for positive 6 ，i in Selecting V when negative 7 The method comprises the steps of carrying out a first treatment on the surface of the The delay time of the first delay module 604, the second delay module 606, the third delay module 612 and the fourth delay module 613 is respectively: t (T) d1 、T d2 、T d3 And T is d4 Satisfy T d1 ＝T d2 ，T d3 ＝T d4 ，T d1 <T d3 。
Referring to fig. 7, a circuit diagram of the full soft switching ac/dc input solid-state transformer when the number n of sub-modules is equal to 3 is shown in fig. 7, each sub-module circuit has the same structure, and the sub-module circuits are combined in a mode of input series connection and output parallel connection.
When the number n of sub-modules is equal to 3, the input currents i are shown in fig. 8 and 9 respectively in Is positive and input current i in A schematic diagram of driving signals of each switching tube in a switching period when the driving signals are negative, wherein the input grid voltage is in a direct current or in a positive half cycle of alternating current in the case of fig. 8, and in the case of fig. 9, the input grid voltage is in a negative half cycle of alternating current; for each sub-module circuit, the driving of the front-stage soft switching circuit is composed of 4 full-bridge circuit driving and one auxiliary tube driving, the primary full-bridge circuit of the rear-stage isolated DC-DC converter is driven by PWM, and the secondary full-bridge circuit is rectified in an uncontrolled manner; there is a phase shift in the drive between the different sub-module circuits.
The operation of the different sub-module circuits is substantially the same, for example sub-module circuit 1, when current i is input in In order to be positive, 14 working states are shared in one switching period, main wave diagrams of different working states are shown in fig. 10, and equivalent circuits of different working states respectively correspond to fig. 11-24. Other submodules operate similarly when a current i is input in The working process of the negative-time circuit can be obtained by similar analysis.
Assume that during a switching period, capacitor C dc_1 And C c_1 Voltage V of (2) dc_1 And V is equal to Cc_1 Remaining unchanged, then the specific phase analysis during one switching cycle is as follows:
stage 1: t is t 0 ～t 1
As shown in fig. 11, the pre-stage circuit S i1_1 、S i3_1 And S is equal to a_1 Conduction and input of current i in Through S i1_1 、S i3_1 Freewheel, voltage across clamping capacitor is V Cc_1 At V Cc_1 Under the action of (a) the auxiliary inductor current i La_1 Linear decrease; post-stage isolated DC-DC converter S o1_1 、S o3_1 Conduction, voltage V between bridge arm midpoints p_1 Greater than zero, resonant current i p_1 For the positive and the secondary sides pass through D o5_1 、D o7_1 Rectifying. This stage up to t 1 Time S i1_1 、S o1_1 、S o3_1 And (5) ending the turn-off.
Stage 2: t is t 1 ～t 2
As shown in fig. 12, t 1 Time S i1_1 Turn off, input current through D i1_1 Freewheel, i La_1 At V Cc_1 Is linearly decreased by the action of (2); at the same time S o1_1 、S o3_1 Shut off, i p_1 Commutating to D o2_1 、D o4_1 On, this is S o2_1 、S o4_1 Provides a condition for zero voltage on. This stage up to t 2 Time S a_1 And (5) ending the turn-off.
Stage 3: t is t 2 ～t 3
As shown in fig. 13, t 2 Time S a_1 Turn-off auxiliary inductor L a_1 And capacitor C i2_1 、C i4_1 、C a_1 Resonance occurs at current i La_1 Under the action of (C) i2_1 、C i4_1 Discharging, capacitance C a_1 Charging, bus voltage V bus_1 Drop, capacitance C a_t The voltage at the two ends rises; the working state of the later-stage isolation type DC-DC converter is the same as that of the stage 2. This stage up to t 3 Time bus voltage V bus_1 The drop to zero ends.
Stage 4: t is t 3 ～t 4
As shown in fig. 14, t 3 Time bus voltage V bus_1 Drop to zero, auxiliary tube capacitance C a_1 Charged to V dc_1 +V Cc_1 ，i La_1 Warp D i1_1 、D i2_1 、D i4_1 、S i3_1 Freewheel, this is S i1_1 、S i2_1 、S i4_1 Creates conditions of zero voltage on, i La_1 At V dc_1 Under the action of (2)Linear rise; the working state of the later-stage isolation type DC-DC converter is the same as that of the stage 2. This stage up to t 4 Time S i1_1 、S i2_1 、S i4_1 、S o2_1 、S o4_1 And (5) ending the opening.
Stage 5: t is t 4 ～t 5
As shown in fig. 15, t 4 Time S i1_1 、S i2_1 、S i4_1 Zero voltage on, i La_1 From D i1_1 、D i2_1 、D i4_1 Commutation to S i1_1 、S i2_1 、S i4_1 Input current i in Warp S i2_1 And S is equal to i3_1 Freewheel, i La_1 At V dc_1 Is linearly increased under the action of the (a); at the same time t 4 Time S o2_1 、S o4_1 Zero voltage on, i p_1 From D o2_1 、D o4_1 Commutation to S o2_1 、S o4_1 . This stage up to t 5 Time i p_1 The drop to zero ends.
Stage 6: t is t 5 ～t 6
As shown in fig. 16, t 6 Time i p_1 Drop to zero, at i p_1 Under the action of the (D), the secondary side of the later-stage isolated DC-DC converter is formed by D o5_1 、D o7_1 Commutating to D o6_1 、D o8_1 The method comprises the steps of carrying out a first treatment on the surface of the The working state of the front-stage soft switching circuit is the same as that of the stage 5. This stage up to t 6 Time of day, S i1_1 、S i4_1 And (5) ending the turn-off.
Stage 7: t is t 6 ～t 7
As shown in fig. 17, t 6 Time of day, S i1_1 、S i4_1 Turn-off auxiliary inductor L a_1 And capacitor C i1_1 、C i4_1 、C a_1 Resonance occurs at current i La_1 Under the action of (C) i1_1 、C i4_1 Charging, capacitor C a_1 Discharging, bus voltage V bus_1 Rise, capacitance C a_1 The voltage across the terminals drops. The working state of the later-stage isolated DC-DC converter is the same as that of the stage 6. This stage up to t 7 Time capacitor C a_1 Two-terminal electricThe depression ends down to zero.
Stage 8: t is t 7 ～t 8
As shown in fig. 18, t 7 Time capacitor C a_1 The voltage at both ends drops to zero, capacitance C i1_1 、C i4_1 Charged to V dc_1 +V Cc_1 Input current i in Warp S i2_1 And S is equal to i3_1 Freewheel, auxiliary diode D a_1 Freewheel on, this is the auxiliary pipe S a_1 Creates conditions of zero voltage on, i La_1 At V Cc_1 Is linearly decreased by the action of (2); the working state of the later-stage isolated DC-DC converter is the same as that of the stage 6. This stage up to t 8 Time S a_1 And (5) ending the opening.
Stage 9: t is t 8 ～t 9
As shown in fig. 19, t 8 Time S a_1 Zero voltage on end, i La_1 From D a_1 Commutation to S a_1 ，i La_1 At V Cc_1 Is linearly decreased by the action of (2); the working state of the later-stage isolated DC-DC converter is the same as that of the stage 6. This stage up to t 9 Time S i2_1 And (5) ending the turn-off.
Stage 10: t is t 9 ～t 10
As shown in fig. 20, t 9 Time S i2_1 Turn off at input current i in Under the action of (C) i1_1 Discharging C i2_1 Charging, i La_1 At V Cc_1 Is linearly decreased by the action of (2); the working state of the later-stage isolated DC-DC converter is the same as that of the stage 6. This stage up to t 10 Time s o2_1 、S o4_1 And (5) ending the turn-off.
Stage 11: t is t 10 ～t 11
As shown in fig. 21, t 10 Time S o2_1 、S o4_1 Turn off at current i p_1 Under the action of (D) diode o1_1 、D o3_1 On, this is S o1_1 、S o3_1 Creating conditions for zero voltage turn-on; c (C) i1_1 Discharging to zero, C i2_1 Charged to V dc_1 +V Cc_1 Input ofCurrent i in Through D i1_1 、S i3_1 Freewheel, this is S i1_1 Creates conditions of zero voltage on, i La_1 At V Cc_1 Is linearly decreased by the action of (a). This stage up to t 11 Time S i1_1 And (5) ending the opening.
Stage 12: t is t 11 ～t 12
As shown in fig. 22, t 11 Time S i1_1 Zero voltage on, i in Through S i1_1 、S i3_1 Freewheel, i La_1 At V Cc_1 Is linearly decreased by the action of (2); the working state of the later-stage isolated DC-DC converter is the same as that of the stage 11. This stage up to t 12 Time S o1_1 、S o3_1 And (5) ending the opening.
Stage 13: t is t 12 ～t 13
As shown in fig. 23, t 12 Time S o1_1 、S o3_1 Zero voltage on, i p_1 From D o1_1 、D o3_1 Commutation to S o1_1 、S o3_1 The method comprises the steps of carrying out a first treatment on the surface of the The pre-stage soft switching circuit operates in the same state as stage 12. This stage up to t 13 Time i p_1 The rising to zero ends.
Stage 14: t is t 13 ～t 14
As shown in fig. 24, t 13 Time i p_1 Rising to zero, and the secondary side of the later-stage isolated DC-DC converter is formed by D o6_1 、D o8_1 Commutating to D o5_1 、D o7_1 The method comprises the steps of carrying out a first treatment on the surface of the The operation state of the front-stage soft switching circuit is the same as that of stage 12, and the stage is the same as stage 1.
The embodiments of the present application described above do not limit the scope of the present application.
Claims (3)
1. A modulation method of an all-soft switch AC/DC input solid-state transformer is characterized in that:
the full soft switching AC/DC input solid-state transformer comprises an input filter inductor (100), n identical pre-stage soft switching circuits (200) and n identical post-stage isolation DC-DC converters (300); the alternating current and direct current input ends of the n pre-stage soft switching circuits (200) are connected in series to form an input port, and the input port is connected in series with the input filter inductor (100) and then connected into a medium-voltage alternating current or direct current power grid; the direct current output ends of the n rear-stage isolated DC-DC converters (300) are connected in parallel to form an output port, and the output port is connected with a low-voltage direct current power grid or a load; the direct current output end of each front-stage soft switching circuit (200) is respectively connected with the direct current input end of one rear-stage isolated DC-DC converter (300) to jointly form a sub-module circuit, and n sub-module circuits are formed in a conformal manner;
the front-stage soft switching circuit (200) comprises a first full-bridge circuit (201), a first auxiliary circuit (202) and a first output capacitor (203); the rear-stage isolation type DC-DC converter (300) comprises a second full-bridge circuit (301), a first LC resonance circuit (302), a first transformer (303), a third full-bridge circuit (304) and a second output capacitor (305);
the first full-bridge circuit (201), the second full-bridge circuit (301) and the third full-bridge circuit (304) comprise two groups of bridge arms, the two groups of bridge arms of the first full-bridge circuit (201) are respectively composed of two series full-control switching tubes which comprise anti-parallel diodes and resonance capacitors, and the two groups of bridge arms of the second full-bridge circuit (301) and the third full-bridge circuit (304) are respectively composed of two series full-control switching tubes which comprise anti-parallel diodes; two upper switching tube drains of two groups of bridge arms of each full-bridge circuit are connected, and two lower switching tube sources are connected;
the middle points of two bridge arms of the first full-bridge circuit (201) form an alternating current-direct current input end of the front-stage soft switching circuit (200); the first auxiliary circuit (202) is connected between the drain electrode of the upper switching tube of the first full-bridge circuit (201) and the positive electrode of the first output capacitor (203), and the source electrode of the lower switching tube of the first full-bridge circuit (201) is connected with the negative electrode of the first output capacitor (203); the first auxiliary circuit (202) is composed of a fully-controlled auxiliary switching tube (208) comprising an anti-parallel diode and a resonant capacitor, a clamping capacitor (209) and an auxiliary inductor (210); the auxiliary switching tube (208) is connected in series with the clamping capacitor (209) to form a series branch, and the two ends of the series branch are connected with the auxiliary inductor (210) in parallel;
the drain electrode of the upper switching tube and the source electrode of the lower switching tube of the second full-bridge circuit (301) form a direct current input end of the rear-stage isolated DC-DC converter (300); the first LC resonant circuit (302) is formed by connecting a resonant inductor (310) and a resonant capacitor (311) in series; the bridge arm midpoint of the second full-bridge circuit (301) is connected with the primary side of the first transformer (303) after being connected with the first LC resonant circuit (302) in series; the drain electrode of the upper switching tube of the third full-bridge circuit (304) is connected with the positive electrode of the second output capacitor (305), and the source electrode of the lower switching tube of the third full-bridge circuit (304) is connected with the negative electrode of the second output capacitor (305); the middle point of the bridge arm of the third full-bridge circuit (304) is connected with the secondary side of the first transformer (303);
the driving signal of each sub-module circuit consists of a soft switch driving signal of the front-stage soft switch circuit (200) and a driving signal of the rear-stage isolated DC-DC converter (300); the front-stage soft switching circuit (200) rectifies an input alternating current voltage by adopting SPWM (sinusoidal pulse width modulation) or converts the amplitude of the input direct current voltage by adopting PWM (pulse width modulation) according to the alternating current-direct current characteristics of the input voltage, certain phase shift exists among carriers of n front-stage soft switching circuits during modulation, and then soft switching modulation is carried out on the basis of SPWM driving or PWM driving, so that a soft switching driving signal of the front-stage soft switching circuit (200) is generated; the rear-stage isolated DC-DC converter (300) adopts PWM modulation, and certain phase shift exists among carriers of n rear-stage isolated DC-DC converters during modulation, so that a driving signal of the rear-stage isolated DC-DC converter (300) is generated;
the method is implemented by means of the following modules: an alternating current-direct current modulation wave selection module (400), a front-stage PWM generation module (500), n identical soft switch modulation modules (600), a front-stage carrier generation module (700), a front-stage carrier phase shift module (800), a rear-stage carrier generation module (900), a rear-stage carrier phase shift module (1000), a rear-stage PWM generation module (1100) and a rear-stage modulation wave generation module (1200);
the AC/DC modulation wave selection module (400) is used for selecting the modulation wave according to the input voltage v in Corresponding modulation signal m is output by AC/DC characteristic of (a) 1 And input the pre-stage PWM generation module (500); the front partThe stage carrier generating module (700) generates a switching period T s1 Saw tooth wave C of (2) 1 Generating n sawtooth carriers with phase shift alpha after the phase shift treatment of the preceding carrier phase shift module (800) and inputting the n sawtooth carriers into the preceding PWM generation module (500), wherein alpha is more than or equal to 0 degree and less than or equal to 360 degrees; the front-stage PWM generation module (500) modulates the signal m 1 SPWM modulation or PWM modulation is respectively carried out on the n sawtooth carriers to generate n groups of front-stage original drivers, and each group of front-stage original drivers is driven by two paths of complementary driving signals V with dead zones 1k And V is equal to 2k The composition is that k is more than or equal to 1 and less than or equal to n; k-th group of front stage original driving signals V 1k 、V 2k Input current i to solid state transformer in The kth soft switch modulation module (600) is input together to generate a group of front-stage soft switch circuit driving signals, and the n soft switch modulation modules (600) generate n groups of front-stage soft switch driving signals which are respectively used for driving the n front-stage soft switch circuits (200); the back-end carrier generating module (900) generates a switching period of T s2 Triangular wave C of (2) 2 Generating n triangular carriers with phase shift beta after phase shift treatment by the rear carrier phase shift module (1000) and inputting the n triangular carriers into the rear PWM generation module (1100), wherein beta is more than or equal to 0 degree and less than or equal to 360 degrees; the post-stage modulation wave generation module (1200) generates a post-stage modulation wave m 2 And input the post-stage PWM generation module (1100); the post PWM generation module (1100) modulates the signal m 2 PWM modulation is performed with n triangular carriers respectively, generating n groups of post-stage driving, and the n groups of post-stage driving are respectively used for driving the n post-stage isolated DC-DC converters (300).
2. The modulation method of the full soft switching ac/dc input solid-state transformer according to claim 1, wherein the method comprises the following steps:
the alternating current-direct current modulation wave selection module (400) comprises an input voltage judgment module (401), an alternating current modulation wave generation module (402), a direct current modulation wave generation module (403) and a first selection switch (404); the alternating current modulation wave generation module (402) and the direct current modulation wave generation module (403) respectively generate alternating current modulation waves and direct current modulation waves and input the alternating current modulation waves and the direct current modulation waves into the first selection switch (404); the input voltage judging module (401) judges the alternating current-direct current characteristics of the input voltage and controls the first selecting switch (404) to select proper modulation signals for output, namely, alternating current modulation waves are selected when the input voltage is alternating current, and direct current modulation waves are selected when the input voltage is direct current.
3. The modulation method of the full soft switching ac/dc input solid-state transformer according to claim 1, wherein the method comprises the following steps:
the soft switch modulation module (600) comprises a first comparator (601), a first inverter (602), an input current polarity judging module (603), a first delay module (604), a first AND gate (605), a second delay module (606), a second AND gate (607), a first OR gate (608), a second selection switch (609), a second OR gate (610), a third OR gate (611), a third delay module (612), a fourth delay module (613), a fourth OR gate (614), a fifth OR gate (615) and a third selection switch (616); solid state transformer input current i in The positive end of the first comparator (601) is input and compared with zero, and the output result is used as a driving signal V gs3 Drive signal V gs3 Is inverted by the first inverter (602) and is used as a driving signal V gs4 ； 1k The result delayed by the first delay module (604) is compared with V 2k Commonly input to the first AND gate (605) to generate V 3 ；V 2k The result delayed by the second delay module (606) is compared with V 1k Commonly input to the second AND gate (607) to generate V 4 ；V 3 And V is equal to 4 Inputting the first OR gate (608) to generate a pass signal V 5 The method comprises the steps of carrying out a first treatment on the surface of the The second selection switch (609) selects the voltage V under the control of the input current polarity judgment module (603) 5 Inputting the second OR gate (610) or the third OR gate (611), i.e. when i in To positive V 5 Inputting said second or gate (610), inputting zero into said third or gate (611), when i in Will V when negative 5 -inputting said third or gate (611), -inputting zero into said second or gate (610); v (V) 1k And V is equal to 2k The second or gate (610) and the third or gate (611) are respectively input, and the output signals of the second or gate (610) and the third or gate (611) are respectively the driving signals V gs1 And V is equal to gs2 ；V gs1 、V gs2 、V gs3 、V gs4 The driving signals are respectively driving signals of the full-bridge circuit switching tubes of the front-stage soft switching circuit in the kth sub-module circuit; v (V) 2k The result delayed by the third delay module (612) is compared with V 1k The common input of the fourth OR gate (614) generates V 6 ，V 1k The result delayed by the fourth delay module (613) is compared with V 2k Common input of the fifth OR gate (615) generates V 7 The method comprises the steps of carrying out a first treatment on the surface of the The third selection switch (616) selects V according to the control of the current polarity judgment module (603) 6 Or V 7 Drive signal V for auxiliary switching tube of the preceding stage soft switching circuit in kth submodule circuit gsa I.e. when i in Selecting V for positive 6 ，i in Selecting V when negative 7 ；
The delay time of the first delay module (604), the second delay module (606), the third delay module (612) and the fourth delay module (613) is respectively as follows: t (T) d1 、T d2 、T d3 And T is d4 Satisfy T d1 ＝T d2 ，T d3 ＝T d4 ，T d1 ＜T d3 。
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