CN113014098A - Fuzzy self-tuning PID control algorithm for staggered parallel bidirectional DC/DC converter - Google Patents

Fuzzy self-tuning PID control algorithm for staggered parallel bidirectional DC/DC converter Download PDF

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CN113014098A
CN113014098A CN202110381265.0A CN202110381265A CN113014098A CN 113014098 A CN113014098 A CN 113014098A CN 202110381265 A CN202110381265 A CN 202110381265A CN 113014098 A CN113014098 A CN 113014098A
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voltage
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CN113014098B (en
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孟凡刚
沈阳
高蕾
宫大东
张伟
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Weihai Tianfan Power Technology Co ltd
WEIHAI TONSLOAD POWER-TECH CO LTD
Harbin Institute of Technology Weihai
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Weihai Tianfan Power Technology Co ltd
WEIHAI TONSLOAD POWER-TECH CO LTD
Harbin Institute of Technology Weihai
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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
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1582—Buck-boost converters
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
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    • Y02T10/72—Electric energy management in electromobility

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Abstract

The invention discloses a fuzzy self-tuning PID control algorithm for a staggered parallel bidirectional DC/DC converter, belonging to the technical field of power electronics. The invention provides a fuzzy self-tuning PID control algorithm aiming at the characteristics that the dynamic response speed of a conventional PID control method is relatively slow and the normal working requirement of an actual power supply system is difficult to meet, and the introduction of fuzzy control enables the dynamic response speed of current and voltage to be fast, the overshoot to be reduced and the current tracking precision to be high; aiming at the problem that parameters of each element of an actual working system are difficult to measure accurately, the fuzzy control can ensure the control effect under the condition that the parameters of a controlled system are uncertain. The control process of the invention has the advantages of simple design, high response speed of the control system, good dynamic characteristic and static characteristic, strong stability and robustness, and can be applied to occasions requiring bidirectional transmission and conversion of electric energy.

Description

Fuzzy self-tuning PID control algorithm for staggered parallel bidirectional DC/DC converter
Technical Field
The invention designs a fuzzy self-tuning PID control algorithm for a staggered parallel bidirectional DC/DC converter, belonging to the technical field of power electronics.
Background
With the development of power electronic technology, power electronic converters are applied more and more widely. In the occasions of a vehicle-mounted double power supply system of a freight truck, a direct-current uninterrupted power supply system, an auxiliary power supply system in a hybrid electric vehicle, a mobile power generation system, a new energy grid connection and energy storage system and the like, a power electronic converter is required to be capable of realizing bidirectional transmission and conversion of electric energy. In these situations, the bidirectional DC/DC converter based on the synchronous four-switch Buck-Boost is widely used due to its advantages of small voltage-current stress, small output voltage-current ripple, low on-state loss, high power density, high reliability, etc.
The conventional PID control method is a control method commonly used by a bidirectional DC/DC converter based on a synchronous four-switch Buck-Boost. However, the interleaved parallel bidirectional DC/DC converter applied to the actual power system requires a fast response speed, and the control method has a relatively slow system dynamic response speed, and is difficult to meet the normal operation requirement of the actual power system. Meanwhile, if a conventional PID parameter setting rule is adopted, due to the uncertainty of parameters of each element of an actual working system, the accurate PID parameter is difficult to calculate through theory, so that the control effect is difficult to ensure.
Fuzzy self-tuning PID control algorithm is commonly used in complex control system, such as nonlinear and time-invariant control system of controlled object. Compared with the conventional PID control method, the control system adopting the fuzzy control converter has good dynamic characteristics and static characteristics, such as high dynamic response speed of current and voltage, small overshoot, high current tracking precision, good current equalizing effect of a current inner loop and the like. In addition, the system adopting fuzzy control can effectively improve the steady-state characteristic, the response speed and the robust performance of the system without knowing an accurate mathematical model of a controlled object. Therefore, the fuzzy self-tuning PID control algorithm is applied to the control system of the staggered parallel bidirectional DC/DC converter, the dynamic response time of the system can be shortened, the overshoot is further reduced, the current tracking precision is improved, the control effect can be ensured under the condition that the parameters of the controlled object are uncertain, and the working requirement of the actual power supply system is better met. Although fuzzy control has the advantages, the main problem in application is that the fuzzy rule and the scale factor are complicated to correct, and the effect of the fuzzy control is difficult to achieve if the fuzzy control is not adjusted properly.
Disclosure of Invention
In order to overcome the defect that the conventional PID control method is applied to the staggered parallel bidirectional DC/DC converter, the invention provides a fuzzy self-tuning PID control algorithm. The method firstly uses a conventional PID control method to realize a basic control effect, and then uses fuzzy control in a voltage controller and a current controller to improve the dynamic characteristic of the system, such as improving the dynamic response speed of the system and reducing overshoot when load parameters change, and simultaneously can also improve the steady-state characteristic of the system, such as improving the current tracking precision. The same inductance current reference value of the two-phase current loop can achieve the current sharing effect when the element parameters are not completely the same.
In order to achieve the purpose, the fuzzy self-tuning PID control algorithm of the staggered parallel bidirectional DC/DC converter is realized according to the following steps:
step 1, establishing a small signal model of a staggered parallel bidirectional DC/DC converter;
step 2, solving a transfer function G according to the equivalent circuit of the small signal modelid(s)、Gvd(s)、Gvi(s)；
Step 3, establishing a control system block diagram;
step 4, designing PI parameters of a current loop and a voltage loop according to the principle of optimal shearing frequency and turning frequency;
step 5, selecting input variables of the fuzzy controller and establishing a fuzzification method;
step 6, designing fuzzy control rules of a voltage fuzzy PI controller and a current fuzzy PI controller;
step 7, establishing a defuzzification method and a working process after output of the fuzzy controller;
and 8, determining the quantization factor and the scale factor of the fuzzy controller.
The invention discloses a fuzzy self-tuning PID control algorithm for an interleaved parallel bidirectional DC/DC converter, which comprises the following steps of 1:
(1) VT when the bidirectional DC/DC converter is operated in the interleaving parallel Boost state1And VT5Remains on, VT2And VT6Remains off, VT3And VT7Operating at a certain duty cycle, VT4And VT8Working with a complementary duty ratio with dead time, and solving a state space average equation of the inductive voltage and the capacitive current according to a direct current converter small signal modeling method as follows:
Figure BDA0003013075990000021
Figure BDA0003013075990000022
Figure BDA0003013075990000031
wherein, V2To output a side terminal voltage, RESRFor output side equivalent load, L1、L2Is an energy storage inductor, C1、C2Is a filter capacitor, d1(t) is the duty ratio of the first path of Boost circuit, d1' (t) is the complementary duty ratio of the first way Boost circuit and d1’(t)＝1-d1(t)，
Figure BDA0003013075990000032
For the first path of Boost circuit duty ratio disturbance quantity, D1For the first Boost circuit steady duty ratio, D1' is the steady state value of the complementary duty ratio of the first path of Boost circuit, d2(t) is the duty ratio of the second path of Boost circuit, d2' (t) is the complementary duty ratio of the second way Boost circuit and d2’(t)＝1-d2(t)，
Figure BDA0003013075990000033
For the duty ratio disturbance quantity of the second path of Boost circuit, D2For the steady state duty ratio of the second Boost circuit, D2' is the steady state value of the complementary duty ratio of the second path Boost circuit, IL1The current of the first path of Boost circuit is the steady-state value of the inductive current,
Figure BDA0003013075990000034
for the first Boost circuit inductance current disturbance quantity, IL2For the second path Boost circuit inductance current steady state value,
Figure BDA0003013075990000035
for the inductor current disturbance amount of the second path of Boost circuit,
Figure BDA0003013075990000036
in order to input the amount of disturbance of the voltage,
Figure BDA0003013075990000037
is the output voltage disturbance quantity;
because the circuit structure adopts two phases which are connected in parallel in a staggered way, the parameters of two-phase elements are completely the same, the average values of two-phase inductive currents are also completely the same,
Figure BDA0003013075990000038
wherein ILIs the average value of the input current; assuming that the average value of the output current is IoThen, according to the basic Boost circuit relationship, there are:
Figure BDA0003013075990000039
in the formula, V20Is the output side supply voltage, D is the circuit steady state duty cycle, and D1＝D2＝D；
(2) VT when the bidirectional DC/DC converter is operated in the interleaved Buck state1And VT5Remains on, VT2And VT6Remains off, VT4And VT8The main switch tube as Buck circuit works at a certain duty ratio, VT3And VT7Working with a complementary duty ratio with dead time, and obtaining a state space average equation of the inductive voltage and the capacitive current according to a direct current converter small signal modeling method as follows:
Figure BDA00030130759900000310
Figure BDA00030130759900000311
Figure BDA0003013075990000041
the invention relates to a fuzzy self-tuning PID control algorithm for a staggered parallel bidirectional DC/DC converter, which comprises the following steps of 2:
(1) in the forward Boost mode, the input side V1Corresponding to the amount of disturbance on the input side
Figure BDA0003013075990000042
Laplace transformation is carried out on state space average equations (1) to (3) of inductive voltage and capacitive current in a forward Boost charging mode, and a transfer function G of a duty ratio and the inductive current can be obtained by combining the equation (4)id(s), duty cycle and voltage V2Transfer function G ofvd(s) and the inductor current and voltage V2Transfer function G ofvi(s) is:
Figure BDA0003013075990000043
Figure BDA0003013075990000044
Figure BDA0003013075990000045
(2) in the reverse Buck mode, the input side V2Corresponding to the amount of disturbance on the input side
Figure BDA0003013075990000046
Laplace transformation is carried out on state space average equations (5) to (7) of the inductive voltage and the capacitive current in the reverse Buck charging mode, and a transfer function G of the duty ratio and the inductive current can be obtainedid(s), duty cycle and voltage V1Transfer function G ofvd(s) and the inductor current and voltage V1Transfer function G ofvi(s) is:
Figure BDA0003013075990000047
Figure BDA0003013075990000048
Figure BDA0003013075990000051
the invention discloses a fuzzy self-tuning PID control algorithm for an interleaved parallel bidirectional DC/DC converter, which comprises the following steps of 3:
the basic control strategy is double closed-loop control of a voltage outer loop and a current inner loop, the inner loop is provided with two same branch circuits, and each branch circuit is provided with a current loop; set voltage reference value VrefWith the actual output voltage V acquired2Comparing to obtain a voltage error VeAnd the input voltage loop fuzzy PI controller outputs a total inductive current reference value ILref(ii) a Reference value I of total currentLrefThe average value is used as an inductive current reference value of two current inner rings and the acquired inductive current IL1、IL2Comparing to obtain the inductance current error ILe1、ILe2Inputting the current loop fuzzy PI controller to output a drive pulse duty ratio d1、d2And the on-off of the switch tube is controlled to realize the control of the bidirectional DC/DC converter.
The invention relates to a fuzzy self-tuning PID control algorithm for an interleaved parallel bidirectional DC/DC converter, which comprises the following steps of (4):
(1) considering the practical application of the bidirectional DC/DC converter, the PI parameter of the current loop is designed on the basis of the optimal shearing frequency and turning frequency, and the transfer function of the PI controller of the current loop is assumed to be
Figure BDA0003013075990000052
Comprises the following steps:
Figure BDA0003013075990000053
Figure BDA0003013075990000054
in the formula, Goi(s)＝GPWM(s)Gid(s)Hi(s) is the open loop transfer function before uncorrecting, GPWM(s) ═ 1 for the transfer function of the PWM generator, Hi(s) ═ 1 is inductance current sampling coefficient, fnIs a transition frequency, fcIs the shear frequency; therefore, the PI parameter K of the current loop can be calculatedP-I0And KI-I0The corrected current inner loop is simplified to a transfer function:
Figure BDA0003013075990000055
(2) voltage open loop transfer function Goi(s)＝Gi(s)Gvi(s)Hv(s) in which HvAnd(s) ═ 1 is an output voltage sampling coefficient, and the parameter K of the voltage loop PI controller can be determined by combining equations (14) to (16) similar to the design method of the current loop PI controllerP-V0And KI-V0。
The invention relates to a fuzzy self-tuning PID control algorithm for an interleaved parallel bidirectional DC/DC converter, which comprises the following steps of 5:
the input variables of the voltage fuzzy controller and the current fuzzy controller are error e and error change rate
Figure BDA0003013075990000061
Fuzzification method, i.e. inputting membership function to select triangular function, error e and error change rate
Figure BDA0003013075990000062
Has a discourse field of [ -3,3 [)]The error e and the error rate of change are calculated according to the input membership function
Figure BDA0003013075990000063
The exact quantities of (c) are converted into the ambiguity domain, i.e. the output ambiguity variables E and EC.
The invention relates to a fuzzy self-tuning PID control algorithm for an interleaved parallel bidirectional DC/DC converter, which comprises the following steps of 6:
establishing a fuzzy rule base, namely determining fuzzy variables of PI parameters output when any group of E and EC is input, wherein the establishment of the fuzzy rule can be determined only by debugging the PI parameters; the influence of the PI parameter change on the control system can be summarized as follows:
(1) increasing the proportionality coefficient KPThe response of the system is generally accelerated, and the static difference is favorably reduced under the condition of the static difference; however, an excessively large proportionality coefficient can cause a system to have a large overshoot and generate oscillation, so that the stability is deteriorated;
(2) increasing integration time
Figure BDA0003013075990000064
The overshoot is reduced, the oscillation is reduced, the system is more stable, and the elimination of the static error of the system is slowed down;
and determining an optimal fuzzy control rule according to the existing control rule and the actual system dynamic response condition.
The invention relates to a fuzzy self-tuning PID control algorithm for an interleaved parallel bidirectional DC/DC converter, which comprises the following steps of (7):
defuzzification processing is carried out on the output variable, the output fuzzy variable is the variable quantity of the PI parameter, the defuzzification processing is carried out by adopting a Mamdani inference model through the defuzzification method, and the accurate quantity of a group of PI parameters, namely delta K, can be obtainedP-I、ΔKI-I、ΔKP-VAnd Δ KI-VRespectively with the known PI parameter KP-I0、KI-I0、KP-V0、KI-V0And adding to obtain the final parameter value of the PI controller, wherein the specific implementation process comprises the following steps:
Figure BDA0003013075990000065
Figure BDA0003013075990000071
in the formula, ei(t) is the current error, evAnd (t) is a voltage error.
The invention relates to a fuzzy self-tuning PID control algorithm for a staggered parallel bidirectional DC/DC converter, which comprises the following steps of 8:
due to error e and error rate of change
Figure BDA0003013075990000072
Has a discourse field of [ -3,3 [)]Therefore, in order to adapt to the actual working condition, the discourse domain needs to be corrected, and a proportional link called as a quantization factor is respectively connected in series at the input sides of the voltage fuzzy controller and the current fuzzy controller; a proportion link is respectively connected in series at the output sides of the voltage fuzzy controller and the current fuzzy controller, and the proportion link is calledA scale factor; and determining an optimal value by continuously adjusting the quantization factor and the scale factor and observing the change rule of the output characteristic curve and the difference between the change rule and the conventional PID control output characteristic curve.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1) the dynamic performance of the system can be improved by fuzzy control, the dynamic response speed of current and voltage is high, and the overshoot is small;
2) the fuzzy control can improve the static performance of the system, the current tracking precision is high, and the current equalizing effect of the current inner ring is good;
3) the fuzzy control can ensure the control effect under the condition that the parameters of the controlled system are uncertain, and better adapts to the working requirements of the actual power supply system.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing the present invention with reference to the accompanying drawings, in which:
FIG. 1 is a schematic diagram of the circuit structure of the present invention;
FIG. 2 is a simplified equivalent circuit diagram of the forward Boost mode of the present invention;
FIG. 3 is a block diagram of the forward Boost mode fuzzy self-tuning PID control algorithm of the invention;
FIG. 4 is a system diagram of a forward Boost mode fuzzy self-tuning PID control algorithm of the invention;
FIG. 5 is a specific implementation process of the forward Boost mode fuzzy self-tuning PID control algorithm of the invention;
FIG. 6 is a comparison graph of the control effects of the normal PID and the fuzzy PID in the forward Boost mode.
Because the structural block diagram and the system diagram of the fuzzy self-tuning PID control algorithm of the forward Boost mode and the reverse Buck mode are similar to the specific implementation process, only the forward Boost mode is illustrated in the attached drawings.
Detailed Description
The following describes in further detail embodiments of the present invention with reference to the accompanying drawings. The following examples or figures are illustrative of the present invention and are not intended to limit the scope of the present invention.
The first embodiment is as follows: the process of establishing a small-signal model of an interleaved parallel bidirectional DC/DC converter is described below with reference to fig. 1 and 2, where the bidirectional DC/DC converter is obtained by connecting two sets of synchronous four-switch Buck-Boost converters in parallel, and the converters can respectively operate in a Buck mode and a Boost mode according to the difference of the energy flow directions at the two sides of the converter.
(1) VT when the bidirectional DC/DC converter is operated in the interleaving parallel Boost state1And VT5Remains on, VT2And VT6Remains off, VT3And VT7Operating at a certain duty cycle, VT4And VT8Working with a complementary duty ratio with dead time, and solving a state space average equation of the inductive voltage and the capacitive current according to a direct current converter small signal modeling method as follows:
Figure BDA0003013075990000081
Figure BDA0003013075990000082
Figure BDA0003013075990000083
wherein, V2To output a side terminal voltage, RESRFor output side equivalent load, L1、L2Is an energy storage inductor, C1、C2Is a filter capacitor, d1(t) is the duty ratio of the first path of Boost circuit, d1' (t) is the complementary duty ratio of the first path of Boost circuit, d1’(t)＝1-d1(t)，
Figure BDA0003013075990000084
For the first path of Boost circuit duty ratio disturbance quantity, D1For the first Boost circuit steady duty ratio, D1' is the first way BoostSteady state value of circuit complementary duty cycle, d2(t) is the duty ratio of the second path of Boost circuit, d2' (t) is the complementary duty ratio of the second path of Boost circuit, d2’(t)＝1-d2(t)，
Figure BDA0003013075990000085
For the duty ratio disturbance quantity of the second path of Boost circuit, D2For the steady state duty ratio of the second Boost circuit, D2' is the steady state value of the complementary duty ratio of the second path Boost circuit, IL1The current of the first path of Boost circuit is the steady-state value of the inductive current,
Figure BDA0003013075990000086
for the first Boost circuit inductance current disturbance quantity, IL2For the second path Boost circuit inductance current steady state value,
Figure BDA0003013075990000087
for the inductor current disturbance amount of the second path of Boost circuit,
Figure BDA0003013075990000088
in order to input the amount of disturbance of the voltage,
Figure BDA0003013075990000091
is the output voltage disturbance quantity.
Because the circuit structure adopts two phases which are connected in parallel in a staggered way, the parameters of two-phase elements are completely the same, the average values of two-phase inductive currents are also completely the same,
Figure BDA0003013075990000092
wherein ILIs the input current average. Assuming that the average value of the output current is IoThen, according to the basic Boost circuit relationship, there are:
Figure BDA0003013075990000093
in the formula, V20Is the output side supply voltage, D is the circuit steady state duty cycle, and D1＝D2＝D。
(3) VT when the bidirectional DC/DC converter is operated in the interleaved Buck state1And VT5Remains on, VT2And VT6Remains off, VT4And VT8The main switch tube as Buck circuit works at a certain duty ratio, VT3And VT7Working with a complementary duty ratio with dead time, and obtaining a state space average equation of the inductive voltage and the capacitive current according to a direct current converter small signal modeling method as follows:
Figure BDA0003013075990000094
Figure BDA0003013075990000095
Figure BDA0003013075990000096
the second embodiment is as follows: solving a transfer function G according to a small signal model equivalent circuitid(s)、Gvd(s)、Gvi(s)。
(3) In the forward Boost mode, the input side V1Corresponding to the amount of disturbance on the input side
Figure BDA0003013075990000097
Laplace transformation is carried out on state space average equations (1) to (3) of inductive voltage and capacitive current in a forward Boost charging mode, and a transfer function G of a duty ratio and the inductive current can be obtained by combining the equation (4)id(s), duty cycle and voltage V2Transfer function G ofvd(s) and the inductor current and voltage V2Transfer function G ofvi(s) is:
Figure BDA0003013075990000098
Figure BDA0003013075990000101
Figure BDA0003013075990000102
(4) in the reverse Buck mode, the input side V2Corresponding to the amount of disturbance on the input side
Figure BDA0003013075990000103
Laplace transformation is carried out on state space average equations (5) to (7) of the inductive voltage and the capacitive current in the reverse Buck charging mode, and a transfer function G of the duty ratio and the inductive current can be obtainedid(s), duty cycle and voltage V1Transfer function G ofvd(s) and the inductor current and voltage V1Transfer function G ofvi(s) is:
Figure BDA0003013075990000104
Figure BDA0003013075990000105
Figure BDA0003013075990000106
the third concrete implementation mode: the working principle of the block diagram of the forward Boost mode control system is described below with reference to fig. 3 and 4. The basic control strategy is double closed-loop control of a voltage outer loop and a current inner loop, the inner loop is provided with two same branch circuits, and each branch circuit is provided with a current loop; set voltage reference value VrefWith the actual output voltage V acquired2Comparing to obtain a voltage error VeAnd the input voltage loop fuzzy PI controller outputs a total inductive current reference value ILref(ii) a Reference value I of total currentLrefThe average value is used as an inductive current reference value of two current inner rings and the acquired inductive current IL1、IL2Comparing to obtain the inductance current error ILe1、ILe2Inputting the current loop fuzzy PI controller to output a drive pulse duty ratio d1、d2And the on-off of the switch tube is controlled to realize the control of the bidirectional DC/DC converter.
The fourth concrete implementation mode: and designing PI parameters of a current loop and a voltage loop according to the principle of optimal shearing frequency and turning frequency.
(1) Considering the practical application of the bidirectional DC/DC converter, the PI parameter of the current loop is designed on the basis of the optimal shearing frequency and turning frequency, and the transfer function of the PI controller of the current loop is assumed to be
Figure BDA0003013075990000111
Comprises the following steps:
Figure BDA0003013075990000112
Figure BDA0003013075990000113
in the formula, Goi(s)＝GPWM(s)Gid(s)Hi(s) is the open loop transfer function before uncorrecting, GPWM(s) ═ 1 for the transfer function of the PWM generator, Hi(s) ═ 1 is inductance current sampling coefficient, fnIs a transition frequency, fcIs the shear frequency; therefore, the PI parameter K of the current loop can be calculatedP-I0And KI-I0The corrected current inner loop is simplified to a transfer function:
Figure BDA0003013075990000114
(2) voltage open loop transfer function Goi(s)＝Gi(s)Gvi(s)Hv(s) in which HvAnd(s) ═ 1 is an output voltage sampling coefficient, and the parameter K of the voltage loop PI controller can be determined by combining equations (14) to (16) similar to the design method of the current loop PI controllerP-V0And KI-V0。
The fifth concrete implementation mode: the input variables of the fuzzy controller are selected to establish the fuzzification method. The input variables of the voltage fuzzy controller and the current fuzzy controller are error e and error change rate
Figure BDA0003013075990000115
Fuzzification method, i.e. inputting membership function to select triangular function, error e and error change rate
Figure BDA0003013075990000116
Has a discourse field of [ -3,3 [)]The error e and the error rate of change are calculated according to the input membership function
Figure BDA0003013075990000117
The exact quantities of (c) are converted into the ambiguity domain, i.e. the output ambiguity variables E and EC.
The sixth specific implementation mode: and designing fuzzy control rules of the voltage fuzzy PI controller and the current fuzzy PI controller. Establishing a fuzzy rule base, namely determining fuzzy variables of PI parameters output when any group of E and EC is input, wherein the establishment of the fuzzy rule can be determined only by debugging the PI parameters; the influence of the PI parameter change on the control system can be summarized as follows:
(3) increasing the proportionality coefficient KPThe response of the system is generally accelerated, and the static difference is favorably reduced under the condition of the static difference; however, an excessively large proportionality coefficient can cause a system to have a large overshoot and generate oscillation, so that the stability is deteriorated;
(4) increasing integration time
Figure BDA0003013075990000121
The overshoot is reduced, the oscillation is reduced, the system is more stable, and the elimination of the static error of the system is slowed down;
and determining an optimal fuzzy control rule according to the existing control rule and the actual system dynamic response condition.
The seventh embodiment: the operation of the defuzzification method and the fuzzy controller output after it is established is described below with reference to fig. 5. Defuzzification processing is carried out on the output variable, the output fuzzy variable is the variable quantity of the PI parameter, the defuzzification processing is carried out by adopting a Mamdani inference model through the defuzzification method, and the accurate quantity of a group of PI parameters, namely delta K, can be obtainedP-I、ΔKI-I、ΔKP-VAnd Δ KI-VRespectively with the known PI parameter KP-I0、KI-I0、KP-V0、KI-V0And adding to obtain the final parameter value of the PI controller, wherein the specific implementation process comprises the following steps:
Figure BDA0003013075990000122
Figure BDA0003013075990000123
in the formula, ei(t) is the current error, evAnd (t) is a voltage error.
The specific implementation mode is eight: a quantization factor and a scale factor of the fuzzy controller are determined. Due to error e and error rate of change
Figure BDA0003013075990000124
Has a discourse field of [ -3,3 [)]Therefore, in order to adapt to the actual working condition, the discourse domain needs to be corrected, and a proportional link called as a quantization factor is respectively connected in series at the input sides of the voltage fuzzy controller and the current fuzzy controller; respectively connecting a proportional link in series at the output sides of the voltage fuzzy controller and the current fuzzy controller, and the proportional links are called as proportional factors; and determining an optimal value by continuously adjusting the quantization factor and the scale factor and observing the change rule of the output characteristic curve and the difference between the change rule and the conventional PID control output characteristic curve.
The specific implementation method nine: the calculation process of the above steps is illustrated by taking the current inner loop as an example and combining with fig. 6. Known as V2＝32V，V20＝31.9156V，C2＝100μF，L＝80μH，RESR2m Ω, D' 0.8438, the current transfer function can be determined by substituting equation (8)
Figure BDA0003013075990000125
Designing a current loop PI controller to enable the compensated system to pass through a frequency fc1kHz, PI controller turning frequency fnWhen the formula (14) and the formula (15) are substituted at 200Hz, K is obtainedP-I0＝0.016、KI-I019.68. Assuming a current error eiRate of change of current error eciAre respectively keiAnd keci，ΔKP-IAnd Δ KI-IAre respectively kpi、kiiAnd let k beei＝keci＝kpi＝k ii1. By controlling the variable method, i.e. only one factor is adjusted and the performance indexes of the output curve, including the rise time, overshoot, adjustment time, oscillation times and steady-state error, are observed, the following conclusions can be obtained:
1) when the quantization factor k is increasedeiThe rise time of the control system becomes longer, and the quantization factor k is reducedeiThe overshoot of the time control system is increased, and the adjusting time is prolonged;
2) when the quantization factor k is increasedeciThe control effect of the time control system is equivalent to that of the conventional PID control, and when the quantization factor k is reducedeciThe adjustment time of the time control system is shortened, and the oscillation frequency is increased;
3) when increasing the scale factor kpiWhen the rising time of the control system is shortened, the overshoot is increased, the oscillation frequency is increased, the adjusting time is shortened, and when the scale factor k is reducedpiThe control effect of the time control system is equivalent to the control effect of the conventional PID;
4) when increasing the scale factor kiiThe control system has shorter rise time and shorter regulation time, and the scale factor k is reducediiThe overshoot of the control system becomes small.
After continuous debugging, k is finally selectedei＝0.08、keci＝0.00001、kpi＝0.39、kiiCompared with the conventional PID control effect, the control system has the advantages that the rising time is shortened, the overshoot is reduced, the adjusting time is shortened, the steady-state error is zero, and the dynamic characteristic and the steady-state characteristic are both improved.

Claims (9)

1. A fuzzy self-tuning PID control algorithm for an interleaved parallel bidirectional DC/DC converter, comprising:
step 1, establishing a small signal model of a staggered parallel bidirectional DC/DC converter;
step 2, solving a transfer function G according to the equivalent circuit of the small signal modelid(s)、Gvd(s) and Gvi(s)；
Step 3, establishing a control system block diagram;
step 4, designing PI parameters of a current loop and a voltage loop according to the principle of optimal shearing frequency and turning frequency;
step 5, selecting input variables of the fuzzy controller and establishing a fuzzification method;
step 6, designing fuzzy control rules of a voltage fuzzy PI controller and a current fuzzy PI controller;
step 7, establishing a defuzzification method and a working process after output of the fuzzy controller;
and 8, determining the quantization factor and the scale factor of the fuzzy controller.
2. The fuzzy self-tuning PID control algorithm for the interleaved parallel bidirectional DC/DC converter according to claim 1, wherein the step 1 is specifically:
(1) VT when the bidirectional DC/DC converter is operated in the interleaving parallel Boost state1And VT5Remains on, VT2And VT6Remains off, VT3And VT7Operating at a certain duty cycle, VT4And VT8Working with a complementary duty ratio with dead time, and solving a state space average equation of the inductive voltage and the capacitive current according to a direct current converter small signal modeling method as follows:
Figure FDA0003013075980000011
Figure FDA0003013075980000012
Figure FDA0003013075980000013
wherein, V2To output a side terminal voltage, RESRFor output side equivalent load, L1、L2Is an energy storage inductor, C1、C2Is a filter capacitor, d1(t) is the duty ratio of the first path of Boost circuit, d1' (t) is the complementary duty ratio of the first way Boost circuit and d1’(t)＝1-d1(t)，
Figure FDA0003013075980000014
For the first path of Boost circuit duty ratio disturbance quantity, D1For the first Boost circuit steady duty ratio, D1' is the steady state value of the complementary duty ratio of the first path of Boost circuit, d2(t) is the duty ratio of the second path of Boost circuit, d2' (t) is the complementary duty ratio of the second way Boost circuit and d2’(t)＝1-d2(t)，
Figure FDA0003013075980000015
For the duty ratio disturbance quantity of the second path of Boost circuit, D2For the steady state duty ratio of the second Boost circuit, D2' is the steady state value of the complementary duty ratio of the second path Boost circuit, IL1The current of the first path of Boost circuit is the steady-state value of the inductive current,
Figure FDA0003013075980000021
for the first Boost circuit inductance current disturbance quantity, IL2For the second path Boost circuit inductance current steady stateThe value of the one or more of,
Figure FDA0003013075980000022
for the inductor current disturbance amount of the second path of Boost circuit,
Figure FDA0003013075980000023
in order to input the amount of disturbance of the voltage,
Figure FDA0003013075980000024
is the output voltage disturbance quantity;
because the circuit structure adopts two phases which are connected in parallel in a staggered way, the parameters of two-phase elements are completely the same, the average values of two-phase inductive currents are also completely the same,
Figure FDA0003013075980000025
wherein ILIs the average value of the input current; assuming that the average value of the output current is IoThen, according to the basic Boost circuit relationship, there are:
Figure FDA0003013075980000026
in the formula, V20Is the output side supply voltage, D is the circuit steady state duty cycle, and D1＝D2＝D；
(2) VT when the bidirectional DC/DC converter is operated in the interleaved Buck state1And VT5Remains on, VT2And VT6Remains off, VT4And VT8The main switch tube as Buck circuit works at a certain duty ratio, VT3And VT7Working with a complementary duty ratio with dead time, and obtaining a state space average equation of the inductive voltage and the capacitive current according to a direct current converter small signal modeling method as follows:
Figure FDA0003013075980000027
Figure FDA0003013075980000028
Figure FDA0003013075980000029
3. the fuzzy self-tuning PID control algorithm for the interleaved parallel bidirectional DC/DC converter according to claim 2, wherein the step 2 is specifically:
(1) in the forward Boost mode, the input side V1Corresponding to the amount of disturbance on the input side
Figure FDA00030130759800000210
Laplace transformation is carried out on state space average equations (1) to (3) of inductive voltage and capacitive current in a forward Boost charging mode, and a transfer function G of a duty ratio and the inductive current can be obtained by combining the equation (4)id(s), duty cycle and voltage V2Transfer function G ofvd(s) and the inductor current and voltage V2Transfer function G ofvi(s) is:
Figure FDA0003013075980000031
Figure FDA0003013075980000032
Figure FDA0003013075980000033
(2) in the reverse Buck mode, the input side V2Corresponding to the amount of disturbance on the input side
Figure FDA0003013075980000034
Laplace transformation is carried out on state space average equations (5) to (7) of the inductive voltage and the capacitive current in the reverse Buck charging mode, and a transfer function G of the duty ratio and the inductive current can be obtainedid(s), duty cycle and voltage V1Transfer function G ofvd(s) and the inductor current and voltage V1Transfer function G ofvi(s) is:
Figure FDA0003013075980000035
Figure FDA0003013075980000036
Figure FDA0003013075980000037
4. the fuzzy self-tuning PID control algorithm for the interleaved parallel bidirectional DC/DC converter according to claim 3, wherein the step 3 is specifically:
the basic control strategy is double closed-loop control of a voltage outer loop and a current inner loop, the inner loop is provided with two same branch circuits, and each branch circuit is provided with a current loop; set voltage reference value VrefWith the actual output voltage V acquired2Comparing to obtain a voltage error VeAnd the input voltage loop fuzzy PI controller outputs a total inductive current reference value ILref(ii) a Reference value I of total currentLrefThe average value is used as an inductive current reference value of two current inner rings and the acquired inductive current IL1、IL2Comparing to obtain the inductance current error ILe1、ILe2Inputting the current loop fuzzy PI controller to output a drive pulse duty ratio d1、d2And controls the on-off of the switch tubeAnd (4) cutting off the circuit to realize the control of the bidirectional DC/DC converter.
5. The fuzzy self-tuning PID control algorithm for the interleaved parallel bidirectional DC/DC converter according to claim 4, wherein the step 4 is specifically:
(1) considering the practical application of the bidirectional DC/DC converter, the PI parameter of the current loop is designed on the basis of the optimal shearing frequency and turning frequency, and the transfer function of the PI controller of the current loop is assumed to be
Figure FDA0003013075980000041
Comprises the following steps:
Figure FDA0003013075980000042
Figure FDA0003013075980000043
in the formula, Goi(s)＝GPWM(s)Gid(s)Hi(s) is the open loop transfer function before uncorrecting, GPWM(s) ═ 1 for the transfer function of the PWM generator, Hi(s) ═ 1 is inductance current sampling coefficient, fnIs a transition frequency, fcIs the shear frequency; therefore, the PI parameter K of the current loop can be calculatedP-I0And KI-I0The corrected current inner loop is simplified to a transfer function:
Figure FDA0003013075980000044
(2) voltage open loop transfer function Goi(s)＝Gi(s)Gvi(s)Hv(s) in which HvAnd(s) ═ 1 is an output voltage sampling coefficient, and the parameter K of the voltage loop PI controller can be determined by combining equations (14) to (16) similar to the design method of the current loop PI controllerP-V0And KI-V0。
6. The fuzzy self-tuning PID control algorithm for the interleaved parallel bidirectional DC/DC converter according to claim 5, wherein the step 5 is specifically:
the input variables of the voltage fuzzy controller and the current fuzzy controller are error e and error change rate
Figure FDA0003013075980000045
Fuzzification method, i.e. inputting membership function to select triangular function, error e and error change rate
Figure FDA0003013075980000046
Has a discourse field of [ -3,3 [)]The error e and the error rate of change are calculated according to the input membership function
Figure FDA0003013075980000047
The exact quantities of (c) are converted into the ambiguity domain, i.e. the output ambiguity variables E and EC.
7. The fuzzy self-tuning PID control algorithm for the interleaved parallel bidirectional DC/DC converter according to claim 6, wherein the step 6 is specifically:
establishing a fuzzy rule base, namely determining fuzzy variables of PI parameters output when any group of E and EC is input, wherein the establishment of the fuzzy rule can be determined only by debugging the PI parameters; the influence of the PI parameter change on the control system can be summarized as follows:
(1) increasing the proportionality coefficient KPThe response of the system is generally accelerated, and the static difference is favorably reduced under the condition of the static difference; however, an excessively large proportionality coefficient can cause a system to have a large overshoot and generate oscillation, so that the stability is deteriorated;
(2) increasing integration time
Figure FDA0003013075980000051
Is beneficial to reducing overshoot and oscillation, and makes the system more stable, but the elimination of the static error of the system is realizedThen the speed is reduced;
and determining an optimal fuzzy control rule according to the existing control rule and the actual system dynamic response condition.
8. The fuzzy self-tuning PID control algorithm for the interleaved parallel bidirectional DC/DC converter according to claim 7, wherein the step 7 is specifically:
defuzzification processing is carried out on the output variable, the output fuzzy variable is the variable quantity of the PI parameter, the defuzzification processing is carried out by adopting a Mamdani inference model through the defuzzification method, and the accurate quantity of a group of PI parameters, namely delta K, can be obtainedP-I、ΔKI-I、ΔKP-VAnd Δ KI-VRespectively with the known PI parameter KP-I0、KI-I0、KP-V0、KI-V0And adding to obtain the final parameter value of the PI controller, wherein the specific implementation process comprises the following steps:
Figure FDA0003013075980000052
Figure FDA0003013075980000053
in the formula, ei(t) is the current error, evAnd (t) is a voltage error.
9. The fuzzy self-tuning PID control algorithm for the interleaved parallel bidirectional DC/DC converter according to claim 8, wherein the step 8 is specifically:
due to error e and error rate of change
Figure FDA0003013075980000054
Has a discourse field of [ -3,3 [)]Therefore, in order to adapt to the actual working condition, the discourse domain needs to be corrected, and a proportional link called as a quantization factor is respectively connected in series at the input sides of the voltage fuzzy controller and the current fuzzy controller; fuzzy control at voltageThe output sides of the controller and the current fuzzy controller are respectively connected in series into a proportional link which is called as a proportional factor; and determining an optimal value by continuously adjusting the quantization factor and the scale factor and observing the change rule of the output characteristic curve and the difference between the change rule and the conventional PID control output characteristic curve.
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