CN109962626B - Optimization control method of double-active full-bridge direct-current converter - Google Patents
Optimization control method of double-active full-bridge direct-current converter Download PDFInfo
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- CN109962626B CN109962626B CN201910410567.9A CN201910410567A CN109962626B CN 109962626 B CN109962626 B CN 109962626B CN 201910410567 A CN201910410567 A CN 201910410567A CN 109962626 B CN109962626 B CN 109962626B
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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
- H02M3/33592—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 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
Abstract
The invention discloses an optimization control method of a double-active full-bridge direct-current converter, which comprises the following steps: when the change of the transmission power caused by the change of the load is detected, the working state of the double-active full-bridge direct-current converter is fixed in a transient period; the voltage difference across the inductor is controlled to be at a maximum value. Based on the transient period operation mode of the fixed converter, the method is used for eliminating offset inductive current during transient response in the double-active full-bridge direct-current converter, greatly improves the operation efficiency of the double-active full-bridge converter, greatly simplifies the complexity of optimization algorithm analysis, and simultaneously realizes the fastest transient switching.
Description
Technical Field
The invention belongs to the technical field of isolated bidirectional active full-bridge direct-current converters, and particularly relates to an optimization control method for eliminating transient response time offset inductor current in a dual-active full-bridge direct-current converter based on a fixed converter transient period operation mode.
Background
As an important component of a high-voltage conversion system, an isolated Bi-directional active-full-bridge direct-current (DAB) converter has the advantages of easy implementation of soft switching, high power density, electrical isolation, bidirectional power transmission and the like, and is widely applied to the fields of distributed power generation systems, energy storage systems, microgrid systems, renewable energy combined power generation systems, electric vehicles and the like. FIG. 1 shows the topology of the DAB converter, in which the primary full bridge H1 is composed of four switching devices S1～S4The secondary side full bridge H2 is composed of another four switching devices S5～S8The primary side and the secondary side are electrically isolated by a transformer with the transformation ratio of n:1, L is a high-frequency inductor, and C is1And C2 is a DC filter capacitor, V1And V2The topology structure can perform reverse power transmission due to the symmetry of the structure of the topology structure corresponding to the direct current input end and the load end respectively.
In the dual-active full-bridge converter, in order to ensure the controllability of the voltage at the output end and the high efficiency of transmission, a triple phase-shift control strategy is mainly adopted in the control mode. FIG. 2 shows a typical waveform, V, of a bi-directional active full-bridge converter using two triple phase-shift control strategiesabAnd VcdCorresponding to the midpoint voltage of the primary bridge arm and the midpoint voltage of the secondary bridge arm respectively. The inductive current is represented byLIs shown in which D1、D2And D3 is the internal phase-shift duty ratio of the midpoint voltage of the primary side bridge arm, the internal phase-shift duty ratio of the midpoint voltage of the secondary side bridge arm, and the external phase-shift duty ratio of the rising edge of the midpoint voltage of the primary side bridge arm. In the operation process of the converter, due to the variability of the load condition, at the moment of switching between two stable operation states, the generation of direct current bias current is caused due to the non-abrupt change of the inductive current, and further the operation efficiency of the double-active full-bridge converter is reduced.
The existing optimization control strategy for transient inductance direct current bias is determined according to a specific phase-shifting control mode, then an optimization equation is listed by comparing the sizes of phase-shifting duty ratios in front and back steady states, and the size of each phase-shifting duty ratio in the transient process is calculated respectively, so that optimization for a transient period is performed. However, the optimization method has no universality, and when the phase-shifting control mode is changed, the optimization equation needs to be readjusted according to the change condition, so that the calculation amount of the optimization process is large. In addition, transient transition periods are long and the analysis process is complex.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide an optimal control method of a double-active full-bridge direct current converter. Based on the transient period operation mode of the fixed converter, the method is used for eliminating bias inductor current during transient response in the double-active full-bridge direct current converter, greatly simplifies the complexity of optimization algorithm analysis, and simultaneously realizes the fastest transient switching.
The technical scheme of the invention is as follows:
an optimization control method for a double-active full-bridge direct current converter comprises the following steps:
s01: when the change of the transmission power caused by the change of the load is detected, the working state of the double-active full-bridge direct-current converter is fixed in a transient period;
s02: the voltage difference across the inductor is controlled to be at a maximum value.
In a preferred technical solution, the method for controlling the voltage difference between the two ends of the inductor to be the maximum value in step S02 includes:
when the transmission power rises due to the change of the load, the switch tube S is switched2，S3，S5And S8Conducting the switch tube S1，S4，S6And S7Turning off;
when the transmission power is reduced due to the change of the load, the switch tube S is switched1，S4，S6And S7Conducting the switch tube S2，S3，S5And S8And (6) turning off.
Compared with the prior art, the invention has the advantages that:
the fixed converter transient period operation mode is used for eliminating transient response time offset inductor current in the double-active full-bridge direct-current converter, the transient response time offset inductor current in the double-active full-bridge direct-current converter can be eliminated by utilizing the working state-transient period operation mode of the fixed converter, the complexity of optimization algorithm analysis can be greatly simplified, the operation efficiency of the double-active full-bridge converter is greatly improved, the fastest transient switching is realized simultaneously, and the universality of almost all phase-shift control modes is realized.
Drawings
The invention is further described with reference to the following figures and examples:
FIG. 1 is a topology of an isolated bidirectional active full-bridge DC converter;
FIG. 2a is a waveform diagram of an isolated bidirectional active full-bridge converter under a light load condition by using a multiple phase-shift control strategy;
FIG. 2b is a waveform diagram of the isolated bidirectional active full-bridge converter under a heavy load condition by using a multiple phase-shift control strategy;
FIG. 3 is a flow chart of an optimization control method of the dual-active full-bridge DC converter;
FIG. 4a is a graph of biasing inductor current during transient response using a conventional optimization algorithm;
FIG. 4b is a graph of biasing inductor current in transient response as power is increased using the optimal control algorithm of the present invention;
FIG. 4c is a graph of the biased inductor current in transient response as power is reduced using the optimal control algorithm of the present invention;
FIG. 5a shows the results of the test without the optimization control;
fig. 5b is an experimental test result using the optimization control method of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
Example (b):
the topology structure of the isolated double-active full-bridge converter adopted in the embodiment is shown in fig. 1, and the converter is composed of a high-frequency inductor L and a transformer, eight switching tubes S1-S8Form an original secondary side full-bridge structure and input power supply V1Through a filter capacitor C1Connected with a full bridge on the primary side and having an output V2Through a DC filter capacitor C2Connected with the secondary side full bridge.
The phase-shift control mode adopted by the bidirectional full-bridge converter in the embodiment is triple phase-shift control. Eight switching tubes S1-S8The gate drive signals of (a) are all square waves with the same frequency and the duty ratio of 0.5, wherein S is1And S3，S2And S4，S5And S7，S6And S8The drive signals of (a) are all complementary signals with a fixed dead zone. Switch tube S3And S4With a drive pulse in-between phase-shifting duty cycle of D1，S7And S8With a drive pulse in-between phase-shifting duty cycle of D2，S4And S8The duty ratio of the external phase shift of the driving pulse is D3. Wherein D1，D2，D3All values of (1) are [0,1 ]]。
As shown in fig. 3, an optimal control method for a dual active full-bridge dc converter includes the following steps:
s01: when the change of the transmission power caused by the change of the load is detected, the working state of the double-active full-bridge direct-current converter is fixed in a transient period;
s02: the voltage difference across the inductor is controlled to be at a maximum value. When the transmission power rises due to the change of the load, the switch tube S is switched2，S3，S5And S8Conducting the switch tube S1，S4，S6And S7Turning off;
when the transmission power is reduced due to the change of the load, the switch tube S is switched1，S4，S6And S7Conducting the switch tube S2，S3，S5And S8And (6) turning off.
The isolated bidirectional active full-bridge converter adopts the normal operation waveform diagram of the triple phase shift control strategy, as shown in fig. 2a and 2 b. The method comprises two working states, wherein fig. 2a is a light load state, fig. 2b is a heavy load state, an expression formula of the minimum value of the inductive current in the two modes can be deduced through a volt-second balance principle of the inductive current, and a current expression formula in fig. 2a is as follows:
the current expression of fig. 2b is as follows:
in the formula (f)sThe switching frequency is represented, the inductance of the isolated bidirectional active full-bridge converter is represented by L, and the voltage conversion ratio is represented by n.
As shown in fig. 4a, 4b, 4c, in order to make the fastest transition from the steady-state period 1 to the steady-state period 2 when the transmission power rises due to a change in the load, the invention proposes to fix the operating state of the converter during the transient period, switching tube S2，S3，S5And S8Conduction, S1，S4，S6And S7And (4) switching off, further controlling the voltage difference between two ends of the inductor to be the maximum value, and enabling the absolute value of the change rate of the inductor current to be the maximum value in the state, wherein the absolute value can be represented by an expression (3).
Therefore, since the rate of change of the inductor current is fixed, the time of the transient transition period will be determined only by the difference between the minimum values of the inductor current before and after the steady state, and the time of the transient transition state of the transient period reaches the theoretical minimum in this state, and can be represented by equation (4).
When the transmission power is reduced due to the change of the load, the operation state of the converter in the transient period is also fixed, and the switch tube S is used for the operation state1，S4，S6And S7Conduction, S2，S3，S5And S8And (4) switching off, and adopting a similar analysis process, wherein the transient period transition state time reaches the theoretical minimum in the state and can be represented by an equation (5).
Fig. 4a and 4b are comparisons of the optimization method for eliminating the offset inductor current during transient response in the dual-active full-bridge dc converter proposed by the present invention and the optimization method without the optimization method in the transient process under triple phase shifting, where it can be found that the dc offset inductor current is reduced to 0 after a plurality of cycles without the optimization algorithm, and after the optimization algorithm proposed by the present invention is adopted, the dc offset inductor current does not appear, thereby verifying the feasibility of the optimization algorithm.
Because the switching is carried out between two stable states and the converter state in the transient period is fixed, the transient period is only determined by the difference value of the minimum value of the two stable inductor currents and the inductor size, and is compared with the phase-shifting duty ratio D before and after work1，D2，D3Therefore, the scheme is not only suitable for triple phase shift control, but also has the same optimization effect on double phase shift control or single phase shift control, thereby improving the wide applicability and flexibility of the invention.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.
Claims (1)
1. The optimization control method of the double-active full-bridge direct current converter is characterized by comprising the following steps of:
s01: when the change of the transmission power caused by the change of the load is detected, the working state of the double-active full-bridge direct-current converter is fixed in a transient period; the double-active full-bridge direct-current converter comprises a primary full-bridge H1 and a secondary full-bridge H2, wherein the primary full-bridge H1 is composed of four switching devices S1~S4Wherein S1, S2 are upper bridges, S3, S4 are lower bridges, and the secondary side full bridge H2 is composed of another four switching devices S5~S8The system comprises a primary side full bridge and a secondary side full bridge, wherein S5 and S6 are upper bridges, S7 and S8 are lower bridges, and the primary side full bridge and the secondary side full bridge are electrically isolated through a transformer with the transformation ratio of n: 1;
s02: controlling the voltage difference across the inductor to be a maximum value, comprising:
when the transmission power rises due to a change in the load, the switching device S is turned on2，S3，S5And S8Is turned on to turn on the switching device S1，S4，S6And S7Turning off;
when the transmission power is reduced due to the variation of the load, the switching device S is turned on1，S4，S6And S7Is turned on to turn on the switching device S2，S3，S5And S8And (6) turning off.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106208718A (en) * | 2016-08-30 | 2016-12-07 | 华南理工大学 | A kind of bidirectional DC/DC system and method based on state transfer |
| CN108039822A (en) * | 2017-12-12 | 2018-05-15 | 西安交通大学 | A kind of transient current control method of double active full-bridge direct current converters |
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|---|---|---|---|---|
| CN106208718A (en) * | 2016-08-30 | 2016-12-07 | 华南理工大学 | A kind of bidirectional DC/DC system and method based on state transfer |
| CN108039822A (en) * | 2017-12-12 | 2018-05-15 | 西安交通大学 | A kind of transient current control method of double active full-bridge direct current converters |
Non-Patent Citations (1)
| Title |
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| Improved Step Load Response of a Dual-Active-Bridge DC-DC Converter;Yifan Zhang等;《electronics》;20180930;第1-15页 * |
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