CN112910264B - Five-degree-of-freedom modulation method of double-active bridge type DC-DC converter - Google Patents
Five-degree-of-freedom modulation method of double-active bridge type DC-DC converter Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33584—Bidirectional converters
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- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
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Abstract
The invention discloses a five-degree-of-freedom modulation method of a double-active bridge type DC-DC converter, which is used for a DAB converter and comprises the following steps: s1, determining the working mode of the DAB converter based on the conducting sequence and the duration of the switches in the DAB converter; s3, with the minimum peak-to-peak value of the inductive current as an optimization target, solving the minimum peak current under each working mode under the KKT condition, and then comparing to obtain a global current peak-to-peak value minimum strategy, wherein the inductive current peak-to-peak value expression is simple and can be regarded as another form of root-mean-square current, so that the optimization complexity can be greatly simplified; the invention has smaller inductive current effective value, almost all switch tubes can realize soft switching, and the conduction loss of the DAB converter can be reduced to the maximum extent; in addition, the invention also reserves the simplicity of control and is easier to realize.
Description
Technical Field
The invention relates to the technical field of power electronic control, in particular to a five-degree-of-freedom modulation method of a double-active bridge type DC-DC converter.
Background
In recent years, with the rapid development of distributed power supplies and energy storage systems, the demand of bidirectional isolation converters (IBDC) is increasing; the double-active full-bridge bidirectional DC/DC (DAB) converter becomes a core topological structure in the bidirectional isolation converter due to the advantages of symmetrical structure, simple control, high power density, high efficiency, modularization and the like, and is widely applied to power electronic transformers, electric vehicles, battery energy storage grid-connected systems and the like.
The traditional DAB converter modulation mode is Phase Shift Modulation (PSM), which controls the direction and the magnitude of transmission power by adjusting a phase shift angle (external phase shift angle) between an original secondary side full bridge of the converter; despite the simplicity of the PSM approach, Zero Voltage Switching (ZVS) operation will be lost when the inputs and outputs do not match, increasing switching losses; in addition, a large amount of reactive power increases the root mean square value of the inductive current, resulting in higher conduction loss; therefore, its conversion efficiency is reduced, especially under light load.
Therefore, how to reduce the switching loss and the conduction loss of the DAB converter and improve the conversion efficiency becomes a problem which needs to be solved by those skilled in the art urgently.
Disclosure of Invention
The present invention is directed to a five-degree-of-freedom modulation method for a dual-active bridge DC-DC converter, so as to solve the problems mentioned in the background art.
In order to achieve the purpose, the invention provides the following technical scheme: five-degree-of-freedom modulation method of double-active bridge type DC-DC converter, which is used for DAB converter, wherein the DAB converter comprises a primary side part and a secondary side part, and the primary side part comprises an H bridge H1Switch S1To S4And a filter capacitor C1The secondary side part comprises an H bridge H2Switch Q1To Q4Filter capacitor C2The DAB converter further comprises a high-frequency transformer T and an equivalent inductor L;
the modulation method comprises the following steps:
s1, determining the working mode of the DAB converter based on the conducting sequence and the duration of the switches in the DAB converter;
s2, solving the steady-state characteristics of each working mode, including the root mean square current of the inductor, the peak current of the inductor and the transmission power;
s3, with the minimum peak-to-peak value of the inductive current as an optimization target, solving the minimum peak current under each working mode under the KKT condition, and then comparing to obtain a global current peak-to-peak value minimum strategy, wherein the inductive current peak-to-peak value expression is simple and can be regarded as another form of root-mean-square current, so that the optimization complexity can be greatly simplified;
s4, in order to further expand the soft switching operation range in the low power range, the inductive current peak-to-peak value and the soft switching range are selected as a common optimization target, and an optimal five-degree-of-freedom modulation scheme is provided by combining a global current peak-to-peak value minimum strategy.
Wherein, the switch S1And S3Are equal in turn-on time, switch S2And S4Are equal in turn-on time, S2And S4Is less than or equal to half a period, defined as D1Ts(ii) a Switch Q1And Q3Are equal in turn-on time, switch Q2And Q4Are equal in turn-on time, Q2And Q4Is less than or equal to half a period, defined as D2Ts(ii) a Switch S1And S4Is defined as D3Ts(ii) a Switch Q1And Q4Is defined as D4Ts(ii) a Switch S1And Q1Is defined as D5Ts；D1、D2、D3、D4And D5Are modulation variables, and satisfy the following relation between the modulation variables:
2D1+D3≤1,2D2+D4≤1
0≤D1,D3,D5≤0.5
wherein, TsRepresents the switching period of the DAB converter; the above five-degree-of-freedom scheme can unify all phase shift modulations.
Wherein the operating mode of the DAB converter comprises:
mode A, starting from one switching period to the end, is S in sequence1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D1-(D3+D4+D5))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode B, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D3-(D3+D4))Ts、((D3-D5)-D1)Ts、D1Ts；
The limiting conditions are as follows:
mode C, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、(D2-D5)Ts、(D4+D5-D2)Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D1-(D3+D4+D5))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode D, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、(D2-D5)Ts、(D4+D5-D2)Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D3-(D3+D4))Ts、((D3-D5)-D1)Ts、D1Ts；
The limiting conditions are as follows:
mode E, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、(D3+D4+D5-D2)Ts、(D1+D2-D3-D4-D5)Ts、(1-(D3-D5)-(D1+D2))Ts、((D3-D5)-D1)Ts、D1Ts；
The limiting conditions are as follows:
mode F, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S2/S3/Q1/Q4Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conduction stageA segment; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、(D1+D2-D4-D5)Ts、(1-2D1-D2)Ts、(D3+D4+D5-(1-D1))Ts、(1-D3-(D3+D4))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode G, S from the beginning to the end of a switching period1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、D3Ts、(D1+D2-(D3+D4+D5))Ts、(1-2D1-D2)Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode H, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、(D2-D5)Ts、(D4+D5-D2)Ts、D3Ts、(D1+D2-(D3+D4+D5))Ts、(1-2D1-D2)Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode I, S in sequence from the beginning to the end of a handover cycle1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、((D3+D4+D5)-D2)Ts、(D1+D2-(D3+D4+D5))Ts、(1-2D1-D2)Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode J, from the beginning to the end of a switching period, is S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、D1Ts、((D3+D4+D5)-(D1+D2))Ts、(1-D1-(D3+D4+D5))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode K, S from the beginning to the end of a switching period1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、D1Ts、((D3+D4+D5)-(D1+D2))Ts、(1-D3-(D3+D4))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
compared with the prior art, the invention has the beneficial effects that:
the invention has smaller inductive current effective value, almost all switch tubes can realize soft switching, and the conduction loss of the DAB converter can be reduced to the maximum extent; in addition, the invention also reserves the simplicity of control and is easier to realize.
Drawings
FIG. 1 is a flow chart of a five-degree-of-freedom modulation method of a dual-active bridge DC-DC converter according to the present invention
FIG. 2 is a topology structure diagram of a dual active full bridge bidirectional DC/DC converter;
FIG. 3 is a typical waveform diagram for a five degree of freedom modulation scheme;
FIG. 4 is a diagram of the relationship between a five degree of freedom modulation strategy and other phase shifting modulation strategies;
FIG. 5 is D1Ts，1-D1Ts，D2Ts+D3Ts，D3TsAnd D3Ts+1-D2TsA possible sequence diagram of;
fig. 6(a) to 6(k) are diagrams of modal classification in five-degree-of-freedom mode;
FIGS. 7(a) to 7(b) are comparative graphs of different power segments;
8(a) -8 (d) are graphs comparing the effective values of the global inductor current peak-to-peak minimum strategy with other modulation strategies;
9(a) -9 (d) are graphs comparing soft switching ranges of the global inductor current peak-to-peak minimum strategy with other modulation strategies;
10(a) to 10(d) are graphs comparing the optimal modulation strategy and the global inductor current peak-to-peak minimum strategy with the effective value obtained under multiple objectives;
11(a) to 11(b) are graphs comparing the optimal modulation strategy and the global inductor current peak-to-peak minimum strategy obtained under multiple objectives with the soft switching range;
FIG. 12 is a modulation block diagram of an optimal five degree of freedom modulation strategy;
fig. 13(a) to 13(d) are steady state waveforms for optimal five degree of freedom modulation at different power levels;
14(a) -14 (d) are graphs comparing the efficiency of the optimal five degree of freedom strategy with other modulation strategies;
fig. 15(a) to 15(b) are dynamic switching waveform diagrams;
fig. 16 is a steady state waveform diagram for mode I.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, the present invention provides a technical solution: five-degree-of-freedom modulation method of double-active bridge type DC-DC converter, which is used for DAB converter, the DAB converter comprises a primary side part and a secondary side part, the primary side part comprises an H bridge H1Switch S1To S4And a filter capacitor C1The secondary side part comprises an H bridge H2Switch Q1To Q4Filter capacitor C2The DAB converter further comprises a high frequency transformer T, an equivalent inductor L;
the modulation method comprises the following steps:
s1, determining the working mode of the DAB converter based on the conduction sequence and the duration of the switches in the DAB converter;
s2, solving the steady-state characteristics of each working mode, including the root mean square current of the inductor, the peak current of the inductor and the transmission power;
s3, with the minimum peak-to-peak value of the inductive current as an optimization target, solving the minimum peak current under each working mode under the KKT condition, and then comparing to obtain a global current peak-to-peak value minimum strategy, wherein the inductive current peak-to-peak value expression is simple and can be regarded as another form of root-mean-square current, so that the optimization complexity can be greatly simplified;
s4, when the global current peak-peak value minimum strategy is in light load, only two switching tubes can realize soft switching operation in a low power range, and large switching loss is caused, so that in order to further expand the soft switching operation range in the low power range, the inductive current peak-peak value and the soft switching range are selected as a common optimization target, and an optimal five-degree-of-freedom modulation scheme is provided by combining the global current peak-peak value minimum strategy.
As shown in fig. 8(a) to 8(d), the five-degree-of-freedom modulation strategy of the dual-active full-bridge bidirectional DC/DC converter proposed by the present invention has certain advantages, relative to FDM and PSM; the effective value of the inductive current is almost consistent with the GOM performance in the whole load range.
As shown in fig. 9(a) to 9(d), the shaded area indicates the area where soft switching cannot be achieved, and it can be seen that the modulation strategy proposed by the present invention is wider than PSM but narrower than FDM at the soft switching level; and not much so with GOM. On the whole, the global minimum modulation strategy still only has two switching tubes to realize soft switching under light load, which brings great switching loss.
In order to further improve the range of soft switching under light load, the peak-to-peak value of the inductive current and the range of the soft switching are selected as a common optimization target, and a mode B and a mode K which can completely realize the soft switching potential are selected for optimization. Fig. 10(a) to 10(d) show the comparison between the optimization results and the global peak-to-peak minimum strategy under multiple objectives. It can be seen that the effective value of the inductor current in the selected mode B under light load is kept to be minimum basically as the global peak-to-peak value minimum strategy.
As shown in fig. 11(a) to 11(d), the mode B selected by the present invention can satisfy the requirement of full switching for almost all switching tubes under light load, and has the potential to realize soft switching, thereby improving the capability of the converter to realize soft switching operation to the maximum extent.
In summary, compared with some optimized schemes at present, the optimal five-degree-of-freedom modulation scheme has a smaller inductive current effective value, almost all switching tubes can realize soft switching, and the conduction loss of the DAB converter can be reduced to the greatest extent. In addition, the invention also reserves the simplicity of control and is easier to realize.
Fig. 2 shows the five-degree-of-freedom gate signal, the transformer primary voltage vp and the secondary voltage vs during a switching cycle. For the main side switch S1-S4Switch S1And S3Are equal in turn-on time, switch S2And S4Are equal in turn-on time, S2And S4Is less than or equal to half a period, defined as D1Ts(ii) a Switch Q1And Q3Are equal in turn-on time, switch Q2And Q4Are equal in turn-on time, Q2And Q4Is less than or equal to half a period, defined as D2Ts(ii) a Switch S1And S4Is defined as D3Ts(ii) a Switch Q1And Q4Is defined as D4Ts(ii) a Switch S1And Q1Is defined as D5Ts；D1、D2、D3、D4And D5Are all the variable of the modulation, and are,they satisfy the following relationship: formula (1)
2D1+D3≤1,2D2+D4≤1
0≤D1,D3,D5≤0.5
Wherein, TsRepresents the switching period of the DAB converter; the above five-degree-of-freedom scheme can unify all phase shift modulations.
Thus, by modulating D1-D5The amplitude and phase of the inductor voltage can be controlled, and thus the amplitude and flow of power transmission can be controlled. As can be seen from fig. 3, the most significant feature of the high frequency alternating voltages vp and vs is that they contain two unequal zero voltage portions within one switching cycle. Compared with TPS and ADM, five degrees of freedom improve the flexibility of control by adding degrees of freedom. It is worth noting that in these five degrees of freedom, when D is1+D2＝0.5，D3+D4When the content is 0.5, TPS is obtained; when D is present2＝0，D4When being equal to 0, the compound is ADM; when D is present1＝0.5、D2＝0、D3+D40.5 or D3＝0.5、D4＝0、D1+D2When the value is 0.5, the compound is EPS; when D is present1+D2＝0.5，D3+D4＝0.5，D1＝D3When the value is DPS; when D is present1＝0.5、D2＝0、D3＝0.5、D4When 0, it is a conventional PSM, and its specific relationship is shown in fig. 4. Thus, the proposed 5-DOF may well unify these existing modulation schemes, i.e. EPS, DPS, TPS and ADM are all special cases of it.
The invention mainly adopts a time domain analysis method to discuss the modal division in a five-degree-of-freedom mode in detail and solve the steady-state characteristics. It can be seen from fig. 3 that the different patterns, which ultimately affect the tendency of iL, form different patterns.
The operating mode of the DAB converter can therefore be divided according to the relative position of vp and vs, and in particular, as can be seen from fig. 3, the three-level state waveform of vp is at D2Ts、(D1+D2) Ts and (1-D)1) At Ts timeThe moment changes. Likewise, vs D5Ts, (D) during the switching period4+D5)Ts、(D3+D4+D5) Ts and (1-D)3+D5) The time Ts also changes. The mode classification of the DAB converter in 5 degrees of freedom is therefore essentially determined by the sequence of the 7 switching moments.
Firstly, sequencing the moments of the vs states from small to large into D5Ts、(D4+D5)Ts、(D3+D4+D5) Ts and (1-D)3+D5) Ts, as shown in FIG. 5. It can be seen that there are five intervals between these four moments, indicated by "1", "2", "3", "4" and "5", respectively. Then, the switching moments of the state change of the vp are inserted into the five intervals to obtain different modes
(1) Assuming that only one switching moment of vp can be scheduled per interval, 10 combinations are formed. For example, D2Ts、(D1+D2) Ts and (1-D)1) Ts is inserted into the intervals "1", "2" and "3", respectively, to form a combination (1,2, 3). In these combinations, when (D)1+D2) Ts is less than (D)4+D5) At Ts, there is greater reactive power, and therefore such combinations are not considered herein, including (1,2,3) (1,2, 4), (1,2, 5); cannot simultaneously satisfy (D)3+D4+D5)Ts<；(D1+D2) Ts and (1-D)3+D5) In the combination of Ts (1,4,5) and (2,4,5), (1-D)1) Ts, therefore, five modes of (1, 3, 4), (1, 3, 5), (1,4,5), (2,3, 5), (3,4, 5) remain, corresponding to the modes a to E shown in fig. 5, respectively.
(2) Assume that the two switching moments of vp are tied together and inserted into the same interval. Thus, there are two cases. One is D2Ts and (D)1+D2) Ts are bound together, two is (D)1+D2) Ts and (1-D)1) Ts are tied together. As described above, when (D)1+D2) Ts is less than (D)4+D5) At Ts, there is considerable reactive power. For the same reason, D2Ts must be less than (D)3+D4+D5)Ts,(D1+D2) Ts must be less than (1-D)3+D5)Ts，(D3+D4+D5) Ts must be less than (1-D)1) Ts. Therefore, when D2Ts and (D)1+D2) When Ts is bound together to satisfy the above requirement, there are 4 combinations of (1,4,4), (2,3,3), (2,4,4), (3,4,4) corresponding to I mode as shown in fig. 5. In addition, when D2Ts and (D)1+D2) Ts, when bound together, can only be inserted into interval 3, the rest (1-D)1) Ts may be inserted into interval 4 and interval 5. Thus, two modes are formed, corresponding to the F mode and the G mode, respectively.
(3) Suppose three switches of vp are together at a time. Obviously, there is no valid mode. From these 7 moments of variation of vp and vs, 11 possible modalities are derived. The method specifically comprises the following steps:
mode A, starting from one switching period to the end, is S in sequence1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D1-(D3+D4+D5))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode B, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D3-(D3+D4))Ts、((D3-D5)-D1)Ts、D1Ts；
The limiting conditions are as follows:
mode C, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; time sequence time division of each stageIs other than D5Ts、(D2-D5)Ts、(D4+D5-D2)Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D1-(D3+D4+D5))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode D, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、(D2-D5)Ts、(D4+D5-D2)Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D3-(D3+D4))Ts、((D3-D5)-D1)Ts、D1Ts；
The limiting conditions are as follows:
mode E, from one switching cycleFrom start to finish, in turn S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、(D3+D4+D5-D2)Ts、(D1+D2-D3-D4-D5)Ts、(1-(D3-D5)-(D1+D2))Ts、((D3-D5)-D1)Ts、D1Ts；
The limiting conditions are as follows:
mode F, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S2/S3/Q1/Q4Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、(D1+D2-D4-D5)Ts、(1-2D1-D2)Ts、(D3+D4+D5-(1-D1))Ts、(1-D3-(D3+D4))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode G, S from the beginning to the end of a switching period1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、D3Ts、(D1+D2-(D3+D4+D5))Ts、(1-2D1-D2)Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode H, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、(D2-D5)Ts、(D4+D5-D2)Ts、D3Ts、(D1+D2-(D3+D4+D5))Ts、(1-2D1-D2)Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode I, S in sequence from the beginning to the end of a handover cycle1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、((D3+D4+D5)-D2)Ts、(D1+D2-(D3+D4+D5))Ts、(1-2D1-D2)Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode J, from the beginning to the end of a switching period, is S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、D1Ts、((D3+D4+D5)-(D1+D2))Ts、(1-D1-(D3+D4+D5))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode K, S from the beginning to the end of a switching period1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、D1Ts、((D3+D4+D5)-(D1+D2))Ts、(1-D3-(D3+D4))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
and solving the inductive current of each interval by adopting a piecewise linear method. For ease of analysis, all parameters are reflected to the primary side of the transformer. Accordingly, with a 5 degree of freedom modulation scheme, the inductor current il (t) can be expressed as: formula (2)
As can be seen from fig. 15, there is a certain relationship between the period and the degree of freedom, which can be summarized as: t is t1-t0＝D2Ts，t2-t1＝(D5-D2)Ts，t3-t2＝D4Ts，t4-t3＝(D1+D2-D4-D5)Ts，t5-t4＝(D3+D4+D5-D1-D2)Ts，t6-t5＝(1-D1-D3-D4-D5)Ts，t7-t6＝(D1+D5-D3) Ts. In the formula (2), the current value of the inductor at the moment of switching can be derived as follows:
in this mode, the current is from t0Rises to t4From t4Down to t8. Therefore, the maximum value of the current occurs at t4At time t, the minimum value occurs0The time of day. Thus, the peak-to-peak current of the inductor can be:
the expression of the transmission power is:
fsexpressing the switching frequency, it can be seen that the inductor current peak-to-peak value is a very simple expression. In addition, it can be seen as another form of the effective value of the inductor current, the magnitude of which is directly related to the magnitude of the conduction loss. In order to obtain a simple steady-state algorithm, the invention selects an expression with the minimum peak-to-peak value of the inductive current as an optimization target. In order to simplify the expression in optimization, the reference values of the inductive current and the transmission power are respectively selected as Ibase＝V1/(2fsL) and Pbase＝V1 2/(2fsL)。
The method takes the minimum peak-to-peak value of the inductive current as an optimization target.
In addition, the steady-state expressions of each working mode are solved, the steady-state characteristics comprise transmission power, inductive current effective value, inductive current peak-to-peak value and the like, and the steady-state expressions are per unit for optimization.
The per unit result of the transmission power of each working mode is as follows:
wherein M is voltage conversion ratio, and M is KV2/V1，V1For the converter input voltage, V2Is the converter output voltage, k is the transformer transformation ratio, P 'is the per unit value of the transmission power, I'p-pIs the per unit value of the peak value of the inductive current.
The method selects the minimum peak-to-peak value of the inductive current as an optimization target, and obtains the optimal path for each mode. Then, by comparing these paths, a global optimal solution is obtained. First, this optimization can be expressed as:
object Ip′-p(D1,D2,D3)
Constraint P' (D)1,D2,D3)-P*≤0
hi(D1,D2,D3)＝0(i＝1,2，...,n)
In the formula, P*For a given transmission power value, hi (D)1,D2,D3) Is a boundary condition for the control variable. For solving such a problem, the KKT condition may be used to solve, and finally, an optimal solution for each modality (operation mode) is obtained, and then the solutions of the modalities are compared, as shown in fig. 6(a) to 6 (d). And finally, obtaining an optimized solution of the whole load range. The load range is divided into two segments, which are defined as low power segment and high power segment, respectively, and the boundary is pi M2 (1-M)/2.
Thus, the global optimal solution is as follows:
when the transmission power is in the range of (pi M (3M +1) (1-M)/8, pi M/4), the global optimal solution is as follows:
in the formula, D1,opt、D2,opt、D3,opt、D4,optAnd D5,optIs the optimal modulation variable.
Then, in order to reduce the switching loss during light load, the invention selects an inductance current effective value and a soft switching range as optimization targets, selects a mode B and a mode K which have all soft switching potentials to realize optimization, and finally obtains an optimized solution as follows:
fig. 14(a) to 14(d) show the efficiency comparison between the present invention and other modulation strategies, and it can be seen that the effect of the present invention in improving efficiency is more obvious.
Fig. 15(a) and (b) show the jump of the load and the output voltage, and it can be seen that the jump from the low power to the high power or the jump from the high power to the low power of the present invention does not have obvious overvoltage and overcurrent, and the switching is completed in one cycle, and the seamless transition can be achieved.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (2)
1. Five-degree-of-freedom modulation method for a dual-active bridge DC-DC converter, characterized in that the modulation method is used for a DAB converter, the DAB converter comprises a primary side part and a secondary side part, the primary side part comprises an H bridge H1Switch S1To S4And a filter capacitor C1The secondary side part comprises an H bridge H2Switch Q1To Q4Filter capacitor C2The DAB converter further comprises a high-frequency transformer T and an equivalent inductor L;
the modulation method comprises the following steps:
s1, determining the working mode of the DAB converter based on the conducting sequence and the duration of the switches in the DAB converter;
s2, solving the steady-state characteristics of each working mode, including the root mean square current of the inductor, the peak current of the inductor and the transmission power;
s3, with the minimum peak-to-peak value of the inductive current as an optimization target, solving the minimum peak current under each working mode under the KKT condition, and then comparing to obtain a global current peak-to-peak value minimum strategy, wherein the inductive current peak-to-peak value expression is simple and can be regarded as another form of root-mean-square current, so that the optimization complexity can be greatly simplified;
s4, in order to further expand the soft switching operation range in the low power range, the peak-to-peak value of the inductive current and the soft switching range are selected as a common optimization target, and an optimal five-degree-of-freedom modulation scheme is provided by combining the minimum strategy of the peak-to-peak value of the global current;
wherein the operating mode of the DAB converter comprises:
mode A, starting from one switching period to the end, is S in sequence1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D1-(D3+D4+D5))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode B, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D3-(D3+D4))Ts、((D3-D5)-D1)Ts、D1Ts；
The limiting conditions are as follows:
mode C, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、(D2-D5)Ts、(D4+D5-D2)Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D1-(D3+D4+D5))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode D, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase，S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、(D2-D5)Ts、(D4+D5-D2)Ts、(D1+D2-D4-D5)Ts、(D3+D4+D5-D1-D2)Ts、(1-D3-(D3+D4))Ts、((D3-D5)-D1)Ts、D1Ts；
The limiting conditions are as follows:
mode E, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、(D3+D4+D5-D2)Ts、(D1+D2-D3-D4-D5)Ts、(1-(D3-D5)-(D1+D2))Ts、((D3-D5)-D1)Ts、D1Ts；
The limiting conditions are as follows:
mode F, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S2/S3/Q1/Q4Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、(D1+D2-D4-D5)Ts、(1-2D1-D2)Ts、(D3+D4+D5-(1-D1))Ts、(1-D3-(D3+D4))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode G, S from the beginning to the end of a switching period1/S3/Q2/Q3Conducting phase, S1/S4/Q2/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D2Ts、(D5-D2)Ts、D4Ts、D3Ts、(D1+D2-(D3+D4+D5))Ts、(1-2D1-D2)Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode H, starting from one switching period to the end, sequentially S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、(D2-D5)Ts、(D4+D5-D2)Ts、D3Ts、(D1+D2-(D3+D4+D5))Ts、(1-2D1-D2)Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode I, S in sequence from the beginning to the end of a handover cycle1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S4/Q1/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、((D3+D4+D5)-D2)Ts、(D1+D2-(D3+D4+D5))Ts、(1-2D1-D2)Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode J, from the beginning to the end of a switching period, is S1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S2/S3/Q1/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、D1Ts、((D3+D4+D5)-(D1+D2))Ts、(1-D1-(D3+D4+D5))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
mode K, S from the beginning to the end of a switching period1/S3/Q2/Q3Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S4/Q1/Q4Conducting phase, S1/S3/Q1/Q4Conducting phase, S1/S3/Q1/Q3Conducting phase, S1/S3/Q2/Q3Conducting phase, S2/S3/Q2/Q3Conducting; the time sequence duration of each stage is D5Ts、D4Ts、(D2-(D4+D5))Ts、D1Ts、((D3+D4+D5)-(D1+D2))Ts、(1-D3-(D3+D4))Ts、(D1-(D3-D5))Ts、(D3-D5)Ts；
The limiting conditions are as follows:
2. the five degree of freedom modulation method of a dual active bridge DC-DC converter of claim 1, comprising: switch S1And S3Are equal in turn-on time, switch S2And S4Are equal in turn-on time, S2And S4Is less than or equal to half a period, defined as D1Ts(ii) a Switch Q1And Q3Are equal in turn-on time, switch Q2And Q4Are equal in turn-on time, Q2And Q4Is less than or equal to half a period, defined as D2Ts(ii) a Switch S1And S4Is defined as D3Ts(ii) a Switch Q1And Q4Is defined as D4Ts(ii) a Switch S1And Q1Is defined as D5Ts；D1、D2、D3、D4And D5Are modulation variables, and satisfy the following relation between the modulation variables:
2D1+D3≤1,2D2+D4≤1
0≤D1,D3,D5≤0.5
wherein, TsRepresents the switching period of the DAB converter; the above five-degree-of-freedom scheme can unify all phase shift modulations.
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| CN114006541B (en) * | 2021-11-30 | 2023-06-06 | 国网四川省电力公司电力科学研究院 | Efficiency optimization control method for double-active half-bridge direct-current converter |
| CN115441749B (en) * | 2022-11-07 | 2023-03-24 | 西南交通大学 | Hybrid three-level double-active-bridge optimal duty ratio modulation method for improving light load efficiency |
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| CN110350793A (en) * | 2019-06-11 | 2019-10-18 | 华中科技大学 | A kind of pair of active bridge DC-DC converter and its current stress optimization method |
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