CN110798072B - Modulation method and system of ANPC active bridge applied to DAB structure - Google Patents

Modulation method and system of ANPC active bridge applied to DAB structure Download PDF

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CN110798072B
CN110798072B CN201911001317.6A CN201911001317A CN110798072B CN 110798072 B CN110798072 B CN 110798072B CN 201911001317 A CN201911001317 A CN 201911001317A CN 110798072 B CN110798072 B CN 110798072B
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switching tube
switching
active bridge
anpc
level
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CN110798072A (en
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张宇
关清心
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Huazhong University of Science and Technology
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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
    • H02M3/3353—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 at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/487—Neutral point clamped inverters
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • 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

Abstract

The invention discloses a modulation method and a system of an Active Neutral Point Clamped (ANPC) active bridge applied to a double-active bridge (DAB) DC/DC converter, wherein the ANPC active bridge is applied to at least one side of a DAB topology and comprises the following steps: the output level of the ANPC active bridge is circularly switched among a positive level, a zero level and a negative level by controlling the turn-on and turn-off time sequence of a switching tube contained in the ANPC active bridge; when the output of the ANPC active bridge is switched in a circulating mode among a positive level, a zero level and a negative level, the two switching tubes closest to the output end of the ANPC active bridge are controlled to be switched in a switching state under the condition that no voltage is borne by the two switching tubes, so that the switching loss of the two switching tubes closest to the output end of the ANPC active bridge is zero, and the total loss of the two switching tubes closest to the output end of the ANPC active bridge is reduced. The invention ensures that hard switching loss is not generated on the two switching tubes with the highest on-state loss, can effectively improve the loss distribution of power devices of the system and reduce the cost of the system.

Description

Modulation method and system of ANPC active bridge applied to DAB structure
Technical Field
The invention relates to the field of entity search, in particular to a modulation method and a system of an Active Neutral Point Clamped (ANPC) Active Bridge applied to a Double Active Bridge (DAB) DC/DC converter structure.
Background
The DC/DC converter with the current isolation and the bidirectional power transmission capability can realize power transmission and voltage transmission between grids with different voltage levels. The Dual Active Bridge (DAB) DC/DC converter has the advantages of electrical isolation, high power density, bidirectional energy flow, easy realization of soft switching, and the like, and has been widely researched and applied in the fields of renewable energy, electric vehicles, energy storage systems, direct current power distribution, and the like. A common DAB topology is dual H-bridge DAB, in which the voltage stress experienced by the switching devices is the dc bus voltage. Because the voltage-resistant grade of the full-control power device is far smaller than the voltage grade of a medium-high voltage direct current power grid, in order to meet the DC/DC conversion requirement of high voltage and high power, the improvement of the voltage grade of the single-module DAB can effectively reduce the number of transformers required in the whole system of a medium-high voltage power grid interface, thereby reducing the cost of the whole system, improving the power density and the reliability, and being very important for direct current power distribution systems of various voltage grades.
By adopting a multi-level circuit topology, a conversion circuit with a higher direct-current voltage grade can be realized by using a switching device with a lower voltage grade, and the multi-level circuit topology is suitable for application occasions with high direct-current bus voltage. Among the multi-level topologies, the three-level topology is most widely used. Compared with a two-level circuit, the three-level circuit topology has the advantages of low voltage stress of a power device, small voltage change rate dv/dt, high equivalent switching frequency and the like. In the DC/DC domain, there is less research on DAB based on three-level conversion circuit topology. Currently, there are 4 main types of three-level circuits adopted in DAB, which are: a hybrid NPC of a Flying Capacitor (FC) three-level Type, a T-Type (T-Type) three-level Type, a Diode Neutral Point Clamped (DNPC) three-level Type, and a Diode and Capacitor mixed Clamped Type. The DNPC has the advantages of small voltage stress of devices, low overall cost of a circuit and low switching loss.
However, the DNPC switch tube needs to select a device with a higher withstand voltage level, and the switching loss and the on-state loss increase accordingly. Considering the higher cost of high withstand voltage class devices, the cost gap between ANPC and DNPC is smaller. Therefore, based on the ANPC circuit, DAB with high direct-current bus voltage can be constructed by using the switching devices with lower voltage-withstanding grade and better performance. Meanwhile, in DAB, the output current and the action time are necessarily different when the active bridge outputs different levels, so the circuit has the problem of unbalanced power device loss distribution. The more unbalanced the distribution of power device losses, the higher the circuit cost at the same output power. The DNPC circuit has no redundant switch state, so the problem of unbalanced loss of power devices cannot be solved, while the ANPC circuit has a large number of redundant switch states, the loss distribution of the switch devices can be balanced through the design of a modulation method and a control algorithm, and the cost performance of the circuit is improved. Therefore, compared with DAB based on DNPC, DAB based on ANPC can adjust the loss distribution of the power device of DAB by designing a corresponding modulation method and a corresponding control algorithm, thereby realizing higher power density and reducing cost.
It should be noted that the frequency of the PWM output voltage of the circuit in the AC/DC conversion domain is much higher than the fundamental frequency, while the switching frequency of the devices of the ANPC in ANPC-DAB is close to the frequency of the PWM output voltage. Therefore, the ANPC modulation optimization method in the AC/DC field is not suitable for ANPC-DAB. Meanwhile, in order to ensure effective voltage clamping, when the ANPC circuit outputs a positive level and a negative level, the corresponding clamping switch tube must be switched on. Therefore, the half-cycle switch state switching (positive level → zero level → negative level) in the ANPC-DAB must be performed at least 6 times, which inevitably results in a large amount of switching loss and reduces the circuit efficiency if the design is not optimized. Meanwhile, in order to ensure stable and efficient operation of DAB based on ANPC, 6 active switching devices are required to bear the same withstand voltage; and since the switching sequence of the output level of the ANPC between its three levels (positive level "+ 1", zero level "0", negative level "-1") is "+ 1" → "0" → "-1" → "0" → +1 ", the modulation method for realizing soft switching in the conventional ANPC for the inversion function is not applicable. The ANPC-DAB has more switching devices and more switching times. If the modulation method cannot be used to expand the soft switching range, the switching loss is large and the system efficiency is low.
Disclosure of Invention
Aiming at the defects of the prior art, such as the special problem when the ANPC is applied to the DAB, the invention aims to solve the technical problems of more hard switches and low efficiency when the ANPC modulation method in the existing AC/DC field is directly applied to the DAB based on the ANPC circuit.
To achieve the above object, in a first aspect, the present invention provides a modulation method of an Active Neutral Point Clamped (ANPC) active bridge applied in a dual active bridge type DC/DC converter (DAB) structure, the ANPC active bridge being applied to at least one side in a DAB topology, comprising the steps of:
the output level of the ANPC active bridge is circularly switched among a positive level, a zero level and a negative level by controlling the on-off time sequence of a switching tube contained in the ANPC active bridge.
When the output of the ANPC active bridge is switched in a circulating mode among a positive level, a zero level and a negative level, controlling two switching tubes nearest to the output end of the ANPC active bridge to carry out switching state switching under the condition of not bearing voltage so as to enable the switching loss of the two switching tubes nearest to the output end of the ANPC active bridge to be zero, and further reducing the total loss of the two switching tubes nearest to the output end of the ANPC active bridge, wherein the total loss comprises switching loss and on-state loss; and the on-state losses of the two switching tubes closest to the output end of the ANPC active bridge are higher than those of other switching tubes of the ANPC active bridge.
Optionally, when the ANPC active bridge is a half-bridge circuit, the ANPC active bridge includes a dc first voltage-dividing capacitor, a dc second voltage-dividing capacitor, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube, and a sixth switching tube;
one end of the first switch tube is connected with the anode of the first voltage-dividing capacitor, the other end of the first switch tube is connected with one end of the second switch tube, the other end of the second switch tube is connected with one end of the third switch tube, the other end of the third switch tube is connected with one end of the fourth switch tube, the other end of the fourth switch tube is connected with the cathode of the second voltage-dividing capacitor, and the anode end of the second voltage-dividing capacitor and the cathode end of the first voltage-dividing capacitor are connected to a first endpoint; the other end of the fifth switching tube and one end of the sixth switching tube are connected and are connected to the first end point in common, one end of the fifth switching tube is connected with the other end of the first switching tube, and the other end of the sixth switching tube is connected with the other end of the third switching tube; the connection point of the other end of the second switching tube and one end of the third switching tube is the output end of the ANPC active bridge, and the connection point of the other end of the fifth switching tube and one end of the sixth switching tube is the direct-current neutral end point of the ANPC active bridge; the voltage between the output end of the ANPC active bridge and the direct-current neutral line end point is the output voltage of the ANPC active bridge; the first voltage division capacitor is used for providing a positive level, and the second voltage division capacitor is used for providing a negative level;
the switch tube can be any fully-controlled switch device such as an IGBT (insulated gate bipolar transistor), an MOSFET (metal-oxide-semiconductor field effect transistor) and the like. When the switch tube is an IGBT, one end of the switch tube is a collector, and the other end of the switch tube is an emitter. When the switch tube is an MOSFET, one end of the switch tube is a source electrode, and the other end is a drain electrode.
The direct current input power supply of the ANPC active bridge can be a single direct current power supply with two ports or a positive direct current power supply with three ports, when the single direct current power supply with two ports is adopted, the positive electrode of the direct current input power supply is connected with the positive electrode of the first voltage-dividing capacitor, and the negative electrode of the direct current input power supply is connected with the negative electrode of the second voltage-dividing capacitor; when a three-port positive and negative direct current power supply is adopted, the anode of the three-port positive and negative direct current power supply is connected with the anode of the first voltage-dividing capacitor, the cathode of the three-port positive and negative direct current power supply is connected with the cathode of the second voltage-dividing capacitor, and the anode of the three-port positive and negative direct current power supply is connected with the first end point;
when the ANPC active bridge outputs a positive voltage, the first switch tube, the second switch tube and the sixth switch tube are conducted; when the ANPC active bridge outputs zero level, the second switching tube, the third switching tube, the fifth switching tube and the sixth switching tube are conducted; when the output negative level of the ANPC active bridge is normal, the third switching tube, the fourth switching tube and the fifth switching tube are conducted; the two switching tubes closest to the output end of the ANPC active bridge are a second switching tube and a third switching tube;
when the positive voltage level of the ANPC active bridge is switched to zero level, the first switching tube is turned off, then the fifth switching tube is turned on, and then the third switching tube is turned on;
when the zero level of the ANPC active bridge is switched to the negative level, the second switching tube is turned off first, then the sixth switching tube is turned off, and then the fourth switching tube is turned on.
Optionally, the method further comprises the steps of:
when the negative voltage level of the ANPC active bridge is switched to zero level, the fourth switching tube is turned off, then the sixth switching tube is turned on, and then the second switching tube is turned on;
when the zero level of the ANPC active bridge is switched to the positive level, the third switching tube is turned off, the fifth switching tube is turned off, and then the first switching tube is turned on.
Optionally, the modulation method takes a zero-level switching state of simultaneously turning on two current branches as a switching state of outputting a zero level; the two current branches refer to a branch formed by the second switching tube and the fifth switching tube and a branch formed by the third switching tube and the sixth switching tube.
Optionally, the second switching tube and the third switching tube generate on-state loss when outputting zero level, positive level or negative level;
the first switching tube and the fourth switching tube generate on-state loss when outputting non-zero level;
the fifth switching tube and the sixth switching tube generate on-state loss when outputting zero level;
the second switching tube and the third switching tube are both switched on or switched off under zero voltage.
Optionally, the ANPC active bridge may also be a full bridge circuit, and the switching tube may be other fully-controlled switching devices such as an IGBT and a MOSFET.
In a second aspect, the present invention provides a modulation system for an Active Neutral Point Clamped (ANPC) active bridge for use in a DAB architecture, the ANPC active bridge for use on at least one side of the DAB topology, comprising:
the control unit controls the on and off time sequence of a switching tube included in the ANPC active bridge to enable the output level of the ANPC active bridge to be switched among a positive level, a zero level and a negative level in a circulating mode; when the output of the ANPC active bridge is switched in a circulating mode among a positive level, a zero level and a negative level, controlling two switching tubes nearest to the output end of the ANPC active bridge to carry out switching state switching under the condition of not bearing voltage so as to enable the switching loss of the two switching tubes nearest to the output end of the ANPC active bridge to be zero, and further reducing the total loss of the two switching tubes nearest to the output end of the ANPC active bridge, wherein the total loss comprises switching loss and on-state loss; and the on-state losses of the two switching tubes closest to the output end of the ANPC active bridge are higher than those of other switching tubes of the ANPC active bridge.
Optionally, when the ANPC active bridge is a half-bridge circuit, the ANPC active bridge includes a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube, and a sixth switching tube; one end of the first switch tube is connected with the anode of a first power supply, the other end of the first switch tube is connected with one end of a second switch tube, the other end of the second switch tube is connected with one end of a third switch tube, the other end of the third switch tube is connected with one end of a fourth switch tube, the other end of the fourth switch tube is connected with the cathode of the second power supply, and the anode end of the second power supply and the cathode end of the first power supply are connected to a first endpoint; the other end of the fifth switching tube and one end of the sixth switching tube are connected and are connected to the first end point in common, one end of the fifth switching tube is connected with the other end of the first switching tube, and the other end of the sixth switching tube is connected with the other end of the third switching tube; the connection point of the other end of the second switching tube and one end of the third switching tube is the output end of the ANPC active bridge, and the connection point of the other end of the fifth switching tube and one end of the sixth switching tube is the direct-current neutral end point of the ANPC active bridge; the voltage between the output end of the ANPC active bridge and the direct-current neutral line end point is the output voltage of the ANPC active bridge; the first power supply is used for providing a positive level, and the second power supply is used for providing a negative level;
when the ANPC active bridge outputs a positive voltage, the control unit controls the first switch tube, the second switch tube and the sixth switch tube to be conducted;
when the ANPC active bridge outputs zero level, the control unit controls the second switching tube, the third switching tube, the fifth switching tube and the sixth switching tube to be conducted;
when the output negative level of the ANPC active bridge is normal, the control unit controls the third switching tube, the fourth switching tube and the fifth switching tube to be conducted; the two switching tubes closest to the output end of the ANPC active bridge are a second switching tube and a third switching tube;
when the positive voltage level of the ANPC active bridge is switched to zero level, the control unit firstly controls the first switching tube to be turned off, then controls the fifth switching tube to be turned on, and then controls the third switching tube to be turned on;
when the zero level of the ANPC active bridge is switched to the negative level, the control unit firstly controls the second switch tube to be switched off, then controls the sixth switch tube to be switched off, and then controls the fourth switch tube to be switched on.
Optionally, when the negative voltage level of the ANPC active bridge is switched to a zero level, the control unit controls the fourth switching tube to be turned off, then controls the sixth switching tube to be turned on, and then controls the second switching tube to be turned on;
when the zero level of the ANPC active bridge is switched to a positive level, the control unit firstly controls the third switching tube to be turned off, then controls the fifth switching tube to be turned off, and then controls the first switching tube to be turned on.
Optionally, the second switching tube and the third switching tube generate on-state loss when outputting a zero level and a non-zero level; the first switching tube and the fourth switching tube generate on-state loss when outputting non-zero level; the fifth switching tube and the sixth switching tube generate on-state loss when outputting zero level; the control unit controls the second switching tube and the third switching tube to be switched on or switched off under zero voltage.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
the invention provides a modulation method and a system of an active neutral point clamped ANPC active bridge applied to a DAB structure, wherein two mutually redundant zero-state branches (respectively composed of a second switching tube, a fifth switching tube, a third switching tube and a sixth switching tube) in the ANPC are utilized, the zero state of the two zero-state branches working in parallel is used as the main zero state of the modulation method, and the corresponding zero state of a single branch is selected as the middle zero state, so that at least two switching tubes can be ensured to work in a zero-voltage switching state all the time, and the efficiency of a converter is improved; the invention adopts the zero state of the parallel work of the double current branches of the ANPC as the main zero state of the modulation method, and can reduce the on-state loss when the ANPC circuit outputs the zero state by utilizing the parallel operation of the two current branches, thereby further improving the efficiency of the converter.
The modulation method and the system of the active neutral point clamped ANPC active bridge applied to the DAB structure enable all hard switching losses in an ANPC circuit to be dispersed in 4 switching tubes, enable the two switching tubes with the highest on-state loss not to generate hard switching losses, effectively improve the power device loss distribution of the system and reduce the system cost; by utilizing the multiple modulation control strategy of DAB, partial devices in the circuit far away from the output of the bridge arm can further work in a soft switching state of zero voltage switching-on, and the efficiency of the converter is effectively improved. The invention can be excellently adapted to DAB based on the ANPC three-level circuit, and effectively improves the efficiency of the converter.
Drawings
FIG. 1 is a flow chart of a modulation method of an ANPC active bridge applied to a DAB structure according to the present invention;
FIG. 2 is a schematic diagram of an application structure of the modulation method provided by the present invention in dual half-bridge ANPC-DAB;
FIG. 3 is a single bridge arm ANPC three-level circuit topology employed by the present invention;
FIG. 4(a) is an equivalent circuit of the ANPC switch state corresponding to state P in the embodiment of the present invention;
FIG. 4(b) is an equivalent circuit of the ANPC switch state corresponding to state N in the embodiment of the present invention;
FIG. 4(c) is an equivalent circuit of the ANPC switch state corresponding to the state O in the embodiment of the present invention;
FIG. 4(d) is an equivalent circuit of the ANPC switch state corresponding to the state L in the embodiment of the present invention;
FIG. 4(e) is an equivalent circuit of the ANPC switch state corresponding to the state U in the embodiment of the present invention;
FIG. 5 shows waveforms of voltage, switching state and driving signal output during a single switching cycle according to an embodiment of the present invention;
fig. 6(a) is an equivalent circuit of state O in the commutation process when I >0 according to the embodiment of the present invention, where state O is switched to state P;
fig. 6(b) is an equivalent circuit of state U in the commutation process when I >0 according to the embodiment of the present invention, in which state O is switched to state P;
fig. 6(c) is an equivalent circuit of dead time in the commutation process when I >0, where the state O is switched to the state P;
fig. 6(d) is an equivalent circuit of state P in the commutation process when I >0 according to the embodiment of the present invention, where state O is switched to state P;
fig. 7(a) is an equivalent circuit of state O in the commutation process when I >0 according to the embodiment of the present invention, where state O is switched to state N;
fig. 7(b) is an equivalent circuit of state L in the commutation process when I >0 according to the embodiment of the present invention, in which state O is switched to state N;
fig. 7(c) is an equivalent circuit of the dead zone interval in the commutation process when the state O is switched to the state N when I >0 according to the embodiment of the present invention;
fig. 7(d) is an equivalent circuit of state N in the commutation process when I >0 according to the embodiment of the present invention, where state O is switched to state N.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a high-efficiency ANPC-DAB modulation method based on an ANPC double-current branch circuit, which can be applied to any DAB containing an ANPC circuit, including but not limited to DAB of a double-half-bridge ANPC circuit, DAB of a double-full-bridge ANPC circuit, DAB of a half-bridge ANPC-H bridge and DAB of a full-bridge ANPC-H bridge.
The modulation method fully and effectively utilizes the characteristics of ANPC circuit topology, exerts high control freedom degree brought by various redundant zero states, is matched with a DAB phase-shifting modulation method, and can maximize the soft switching range of DAB, reduce the overall switching loss and balance the loss distribution of power devices.
Fig. 1 is a flow chart of a modulation method of an ANPC active bridge applied in a DAB structure, the ANPC active bridge is applied to at least one side of a DAB topology, as shown in fig. 1, and the method includes the following steps:
s101, the output level of the ANPC active bridge is circularly switched among a positive level, a zero level and a negative level by controlling the turn-on and turn-off time sequence of a switching tube contained in the ANPC active bridge;
s102, when the output of the ANPC active bridge is switched in a circulating mode among a positive level, a zero level and a negative level, controlling two switching tubes nearest to the output end of the ANPC active bridge to carry out switching state switching under the condition of not bearing voltage, so that the switching loss of the two switching tubes nearest to the output end of the ANPC active bridge is zero, and therefore the total loss of the two switching tubes nearest to the output end of the ANPC active bridge is reduced, and the total loss comprises the switching loss and the on-state loss; and the on-state losses of the two switching tubes closest to the output end of the ANPC active bridge are higher than those of other switching tubes of the ANPC active bridge.
In the high-efficiency ANPC-DAB modulation method based on the ANPC double-current branch circuit, 5 switching states are adopted for any half-bridge ANPC three-level circuit in DAB, wherein the switching states comprise 2 non-zero level switching states, a double-current branch circuit zero level state and two intermediate zero level states.
The application structure of the present invention in this circuit is shown in fig. 2, taking DAB of the double half-bridge ANPC as an example. The high-efficiency ANPC-DAB modulation method based on the ANPC double-current branch circuit provides driving signals of 6 switching tubes in the corresponding single-bridge-arm ANPC circuit according to the output level of any single-phase half-bridge ANPC circuit in DAB under the control of the multi-modulation method. In the following drawings, the switching tube is exemplified as an IGBT, and it will be understood by those skilled in the art that the switching tube is not limited to an IGBT, and other fully-controlled switching devices may be used.
The topology of the single-bridge arm ANPC circuit is shown in fig. 3, and the proposed DAB high-efficiency modulation method based on the ANPC circuit is implemented by using 5 switch states as shown in table 1, wherein "1" represents on and "0" represents off. In the switching process, the states P, N and O are the main switching states when a positive level, a negative level, and a zero level are output, and their equivalent circuits are shown in fig. 4(a), 4(b), and 4 (c). While states L and U are intermediate zero states as shown in fig. 4(d) and 4(e), only for the transition switch states.
TABLE 1 on-off states of ANPC three-level circuit for DAB
Figure BDA0002241415620000101
In ANPC-DAB, the switching sequence of the single ANPC bridge arm is P->U->O->L->N->L->O->U->P, the voltage waveform and the modulation waveform of the corresponding output are shown in fig. 5. Wherein, G in FIG. 51-G6Respectively represent Q1-Q6Drive signal of VacRepresenting the AC voltage output by the ANPC bridge arm, delta T representing the duration of the intermediate zero state L or U, D representing the duty ratio of the time of the non-zero level output by the ANPC bridge arm in the whole switching period, and TsIndicating the switching period of the ANPC.
1. Switching between zero states
As shown in FIG. 3, Q2、Q3、Q5And Q6Can be used to output a zero level. When the switch state is O, the 4 switch tubes are all conducted, and when the switch state is U and L, 3 switch tubes are conducted. Thus, in switching states L and U, Q is off2Or Q3The voltage at the two ends is always 0 and is not influenced by the direction of current. Thus, the switching process between state O and state U, L is always a zero voltage switch.
2. Switching between zero and non-zero states
Taking an output current I >0 of a certain bridge arm as an example, a commutation process in switching of a switch is analyzed as follows.
a)O-P
In the process of switching from state O to state U, Q3Is turned off for zero voltage. When the state is switched from U to P, Q needs to be turned off first5As shown in fig. 6(a) to 6 (d). At this time, due to I>0, current is still flowing through Q2、D5Thus Q5Turn-off of (1) is zero voltage turn-off. After a certain dead time, Q is turned on1，Q1Will produce an on-loss, D5Resulting in reverse recovery losses.
b)P-O
When the switch state is P, Q1、Q2And conducting. To switch the switch state to U, Q is first turned off1. Due to I>0, current will pass through Q2、D5And Q6、D3And then follow current. After a certain dead time, Q is switched on5Due to D5Has been turned on, so Q5Is zero voltage in the turn-on processAnd (4) opening. Thus, when the switch state is switched from P to U, only Q is provided1Resulting in hard turn-off losses. After the switch state U lasts for a certain time, the state is switched to a state O, and the zero voltage turns on Q3。
c)O-N
As shown in fig. 7(a) to 7(d), when the switching state is switched from O to L, Q is first turned off at zero voltage2。I>At 0, current flows through Q6、D3. Switching the switch state to N requires Q to be turned off first6At this time Q6For hard turn-off, the current flows through D3、D4And then follow current. After a dead time, Q4Is on due to D4Has been turned on, therefore, Q4Turning on for zero voltage.
d)N-O
Switch state N, I>At 0, current flows through D3、D4. To switch the switch state to L requires turning off Q4And is turned off at zero voltage. After a certain dead time, Q is turned on6At this time Q6Is hard on and at D4Resulting in reverse recovery losses. At this time, the circuit switch state is switched to L, and a zero level is output. Switching state L to state O requires zero voltage to turn on Q2。
Likewise, for I<The switch switching state at 0 was analyzed, and I is given in tables 2 and 3, respectively>0 and I<0, distribution of switching losses during state switching. It can be seen that during all switching, Q is measured regardless of the current direction2、Q3There is no hard switching action. Due to the characteristics of the circuit, Q1、Q4Producing on-state losses only when the output is non-zero, and Q5、Q6Generating on-state losses only when outputting zero state, only Q2And Q3On-state losses occur when either a zero or non-zero state is output. Therefore, the modulation method provided by the invention can concentrate all switching losses on Q1、Q4、Q5And Q6Therefore, the loss distribution of the power device of the circuit can be effectively improved.
TABLE 2 distribution of switching losses during state switching when I >0
Figure BDA0002241415620000121
TABLE 3 distribution of switching losses during state switching at I <0
Figure BDA0002241415620000122
ZVS indicates that the corresponding switching tube is switched on or switched off under zero voltage and does not generate switching loss, hard switching-on or hard switching-off indicates that the corresponding switching tube generates switching loss in the switching process, and I indicates the alternating current output current of the ANPC circuit when the corresponding diode generates a reverse recovery process. Based on tables 2 and 3, it can be seen that as long as the multiple modulation control of DAB can ensure that the corresponding ANPC circuit satisfies the following conditions during state switching, zero-voltage soft turn-on of all switching devices can be realized, and the converter efficiency is effectively improved.
TABLE 4 zero Voltage Soft-on Condition
Figure BDA0002241415620000131
The high-efficiency ANPC-DAB modulation method based on the ANPC double current branches ensures the minimum hard switching times of a single bridge arm in DAB adopting an ANPC circuit by reasonably selecting the switching state, has better power loss distribution performance, can realize zero voltage switching-on of all devices by matching with multiple phase-shift modulation of DAB, further reduces the system loss, improves the system efficiency and reduces the cost.
Accordingly, the present invention provides a modulation system for an Active Neutral Point Clamped (ANPC) active bridge for use in a DAB architecture, the ANPC active bridge being for use on at least one side of the DAB topology, the system comprising:
the control unit controls the on and off time sequence of a switching tube included in the ANPC active bridge to enable the output level of the ANPC active bridge to be switched among a positive level, a zero level and a negative level in a circulating mode; when the output of the ANPC active bridge is switched in a circulating mode among a positive level, a zero level and a negative level, controlling two switching tubes nearest to the output end of the ANPC active bridge to be switched on or off under the condition of not bearing voltage so as to enable the switching loss of the two switching tubes nearest to the output end of the ANPC active bridge to be zero, and further reducing the total loss of the two switching tubes nearest to the output end of the ANPC active bridge, wherein the total loss comprises the switching loss and the on-state loss; and the on-state losses of the two switching tubes closest to the output end of the ANPC active bridge are higher than those of other switching tubes of the ANPC active bridge.
The detailed control steps of the control unit can be referred to the foregoing method embodiments, and are not described herein.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (6)

1. A modulation method for an Active Neutral Point Clamped (ANPC) active bridge for application in a DAB architecture, said ANPC active bridge being applied to at least one side in a DAB topology, characterized in that said modulation method is applied to a dual active bridge DC/DC converter architecture, comprising the steps of:
the output level of the ANPC active bridge is circularly switched among a positive level, a zero level, a negative level and a zero level by controlling the turn-on and turn-off time sequence of a switching tube contained in the ANPC active bridge;
when the output level of the ANPC active bridge is switched in a circulating mode among a positive level, a zero level, a negative level and a zero level, controlling two switching tubes nearest to the output end of the ANPC active bridge to carry out switching state switching under the condition of not bearing voltage so as to enable the switching loss of the two switching tubes nearest to the output end of the ANPC active bridge to be zero, and therefore reducing the total loss of the two switching tubes nearest to the output end of the ANPC active bridge, wherein the total loss comprises switching loss and on-state loss; the on-state losses of the two switching tubes closest to the output end of the ANPC active bridge are higher than those of other switching tubes of the ANPC active bridge;
the ANPC active bridge is a half-bridge circuit and comprises a direct-current first voltage-dividing capacitor, a direct-current second voltage-dividing capacitor, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube and a sixth switching tube;
one end of the first switch tube is connected with the anode of the first direct-current voltage-dividing capacitor, the other end of the first switch tube is connected with one end of the second switch tube, the other end of the second switch tube is connected with one end of the third switch tube, the other end of the third switch tube is connected with one end of the fourth switch tube, the other end of the fourth switch tube is connected with the cathode of the second direct-current voltage-dividing capacitor, and the anode end of the second direct-current voltage-dividing capacitor and the cathode end of the first direct-current voltage-dividing capacitor are connected to a first end point; the other end of the fifth switching tube and one end of the sixth switching tube are connected and are connected to the first end point in common, one end of the fifth switching tube is connected with the other end of the first switching tube, and the other end of the sixth switching tube is connected with the other end of the third switching tube; the connection point of the other end of the second switching tube and one end of the third switching tube is the output end of the ANPC active bridge, and the connection point of the other end of the fifth switching tube and one end of the sixth switching tube is the direct-current neutral end point of the ANPC active bridge; the voltage between the output end of the ANPC active bridge and the direct-current neutral line end point is the output voltage of the ANPC active bridge; the direct current first voltage division capacitor is used for providing a positive level, and the direct current second voltage division capacitor is used for providing a negative level;
the direct-current input power supply of the ANPC active bridge is a single direct-current power supply with two ports or a positive direct-current power supply with three ports, when the single direct-current power supply with two ports is adopted, the positive electrode of the direct-current input power supply is connected with the positive electrode of the direct-current first voltage-dividing capacitor, and the negative electrode of the direct-current input power supply is connected with the negative electrode of the direct-current second voltage-dividing capacitor; when a three-port positive and negative direct current power supply is adopted, the anode of the three-port positive and negative direct current power supply is connected with the anode of a direct current first voltage division capacitor, the cathode of the three-port positive and negative direct current power supply is connected with the cathode of a direct current second voltage division capacitor, and the anode of the three-port positive and negative direct current power supply is connected with a first end point;
when the ANPC active bridge outputs a positive voltage, the first switch tube, the second switch tube and the sixth switch tube are conducted; when the ANPC active bridge outputs zero level, the second switching tube, the third switching tube, the fifth switching tube and the sixth switching tube are conducted; when the output negative level of the ANPC active bridge is normal, the third switching tube, the fourth switching tube and the fifth switching tube are conducted; the two switching tubes closest to the output end of the ANPC active bridge are a second switching tube and a third switching tube;
when the positive voltage level of the ANPC active bridge is switched to zero level, the first switching tube is turned off, then the fifth switching tube is turned on, and then the third switching tube is turned on;
when the zero level of the ANPC active bridge is switched to the negative level, the second switching tube is turned off, the sixth switching tube is turned off, and then the fourth switching tube is turned on;
when the negative voltage level of the ANPC active bridge is switched to zero level, the fourth switching tube is turned off, then the sixth switching tube is turned on, and then the second switching tube is turned on; when the zero level of the ANPC active bridge is switched to the positive level, the third switching tube is turned off, the fifth switching tube is turned off, and then the first switching tube is turned on.
2. A modulation method of an Active Neutral Point Clamped (ANPC) active bridge for application in a DAB structure according to claim 1, characterized in that the modulation method takes a zero level switching state that simultaneously turns on two current branches as a switching state of an output zero level; the two current branches refer to a branch formed by the second switching tube and the fifth switching tube and a branch formed by the third switching tube and the sixth switching tube.
3. A modulation method for an Active Neutral Point Clamped (ANPC) active bridge for use in a DAB structure according to claim 1 or 2, wherein the second switching transistor and the third switching transistor generate on-state loss at output of zero, positive or negative level;
the first switching tube and the fourth switching tube generate on-state loss when outputting non-zero level;
the fifth switching tube and the sixth switching tube generate on-state loss when outputting zero level;
the second switching tube and the third switching tube are both switched on or switched off under zero voltage.
4. Method for modulating an active ANPC active bridge for application in a DAB architecture according to claim 1 or 2, characterized in that the ANPC active bridge is a full bridge circuit and the switching tubes are IGBTs, MOSFETs or other fully controlled switching devices.
5. A modulation system for an Active Neutral Point Clamped (ANPC) active bridge for use in a DAB architecture, said ANPC active bridge being for use on at least one side in a DAB topology, wherein said modulation system is for use in a dual active bridge DC/DC converter architecture, comprising:
the control unit controls the on and off time sequences of a switching tube included in the ANPC active bridge to enable the output level of the ANPC active bridge to be switched among a positive level, a zero level, a negative level and a zero level in a circulating mode; when the output level of the ANPC active bridge is switched in a circulating mode among a positive level, a zero level, a negative level and a zero level, controlling two switching tubes nearest to the output end of the ANPC active bridge to carry out switching state switching under the condition of not bearing voltage so as to enable the switching loss of the two switching tubes nearest to the output end of the ANPC active bridge to be zero, and therefore reducing the total loss of the two switching tubes nearest to the output end of the ANPC active bridge, wherein the total loss comprises switching loss and on-state loss; the on-state losses of the two switching tubes closest to the output end of the ANPC active bridge are higher than those of other switching tubes of the ANPC active bridge;
the ANPC active bridge is a half-bridge circuit and comprises a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube and a sixth switching tube; one end of the first switch tube is connected with the anode of a first power supply, the other end of the first switch tube is connected with one end of a second switch tube, the other end of the second switch tube is connected with one end of a third switch tube, the other end of the third switch tube is connected with one end of a fourth switch tube, the other end of the fourth switch tube is connected with the cathode of the second power supply, and the anode end of the second power supply and the cathode end of the first power supply are connected to a first endpoint; the other end of the fifth switching tube and one end of the sixth switching tube are connected and are connected to the first end point in common, one end of the fifth switching tube is connected with the other end of the first switching tube, and the other end of the sixth switching tube is connected with the other end of the third switching tube; the connection point of the other end of the second switching tube and one end of the third switching tube is the output end of the ANPC active bridge, and the connection point of the other end of the fifth switching tube and one end of the sixth switching tube is the direct-current neutral end point of the ANPC active bridge; the voltage between the output end of the ANPC active bridge and the direct-current neutral line end point is the output voltage of the ANPC active bridge; the first power supply is used for providing a positive level, and the second power supply is used for providing a negative level;
when the ANPC active bridge outputs a positive voltage, the control unit controls the first switch tube, the second switch tube and the sixth switch tube to be conducted;
when the ANPC active bridge outputs zero level, the control unit controls the second switching tube, the third switching tube, the fifth switching tube and the sixth switching tube to be conducted;
when the output negative level of the ANPC active bridge is normal, the control unit controls the third switching tube, the fourth switching tube and the fifth switching tube to be conducted; the two switching tubes closest to the output end of the ANPC active bridge are a second switching tube and a third switching tube;
when the positive voltage level of the ANPC active bridge is switched to zero level, the control unit firstly controls the first switching tube to be turned off, then controls the fifth switching tube to be turned on, and then controls the third switching tube to be turned on;
when the zero level of the ANPC active bridge is switched to the negative level, the control unit controls the second switching tube to be turned off, then controls the sixth switching tube to be turned off, and then controls the fourth switching tube to be turned on;
when the negative voltage level of the ANPC active bridge is switched to zero level, the control unit controls the fourth switching tube to be turned off, then controls the sixth switching tube to be turned on, and then controls the second switching tube to be turned on; when the zero level of the ANPC active bridge is switched to a positive level, the control unit firstly controls the third switching tube to be turned off, then controls the fifth switching tube to be turned off, and then controls the first switching tube to be turned on.
6. The modulation system of the Active Neutral Point Clamped (ANPC) active bridge applied in a DAB structure as claimed in claim 5, wherein the second switching tube and the third switching tube generate on-state loss when outputting zero level and non-zero level; the first switching tube and the fourth switching tube generate on-state loss when outputting non-zero level; the fifth switching tube and the sixth switching tube generate on-state loss when outputting zero level; the control unit controls the second switching tube and the third switching tube to be switched on or switched off under zero voltage.
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