CN111884502A - DC-DC converter cascade linear active disturbance rejection voltage control method - Google Patents

DC-DC converter cascade linear active disturbance rejection voltage control method Download PDF

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CN111884502A
CN111884502A CN202010657566.7A CN202010657566A CN111884502A CN 111884502 A CN111884502 A CN 111884502A CN 202010657566 A CN202010657566 A CN 202010657566A CN 111884502 A CN111884502 A CN 111884502A
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voltage
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converter
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cascade
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杨苗
温新叶
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China Three Gorges University CTGU
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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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0038—Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A DC-DC converter cascade linear active disturbance rejection voltage control method includes steps 1: sampling DC-DC converter voltage VoBus voltage VdcInductor current IL(ii) a Step 2: will DC-DC converter output voltage VoAnd a DC-DC converter reference voltage value Vdc_refComparing to obtain a voltage error signal evThe error signal is processed by the outer loop LADRC controller to obtain the current inner loop command current IL_ref(ii) a And step 3: the inductive current I detected in the step 1 is measuredLAnd obtaining the current inner ring instruction current in the step 2IL_refComparing to obtain a current error signal eiThe error signal passes through an inner ring LADRC controller to obtain an output control quantity u; and 4, step 4: comparing the output control quantity u with a given carrier signal in the step 3 to generate a switching pulse signal PWM, controlling a power device, and stabilizing the bus voltage or adjusting the output power according to an instruction; the invention is directed to direct currentA DC-DC converter in a microgrid provides a method for controlling cascade linear active disturbance rejection voltage of the DC-DC converter, and the DC-DC converter can stably work under the conditions of large-range direct-current bus voltage fluctuation and load disturbance.

Description

DC-DC converter cascade linear active disturbance rejection voltage control method
Technical Field
The invention belongs to the field of direct-current micro-grid control, and particularly relates to a cascade linear active disturbance rejection voltage control method for a DC-DC converter.
Background
The DC-DC converter is used as a basic conversion unit of the direct-current microgrid, unidirectional and bidirectional energy transmission is completed in the direct-current microgrid system, the energy transmission is an important ring for energy regulation of the direct-current microgrid, and the energy dispatching of each module of the direct-current microgrid is completed by controlling the voltage of a direct-current bus in equipment-level control. The output characteristics of a DC-DC converter depend mainly on the control method of the voltage and the distributed power of the converter device employed. Earlier, the control strategy on the DC-DC converter is a voltage or current type peak value and peak valley control mode, and a PI compensation network is adopted to complete control. At present, the research on the types of the DC-DC converters is mature, although various novel DC-DC converters with high transformation ratio and high transformation rate appear, the basic DC-DC converter is still widely applied due to simple topology and control and high transformation efficiency, and the control strategy generally adopts a voltage outer loop and current inner loop double closed loop control mode. Most DC-DC converters adopt basic Buck, Boost, bidirectional Buck-Boost and combinations thereof and other conversion structures, and for this reason, the improvement of the conversion performance of the DC-DC converter mainly depends on the adopted control strategy.
Currently, the main control methods for the DC side voltage of the DC-DC converter are: the control method comprises the control methods of a traditional PI control algorithm, sliding mode control, prediction current control, self-adaptive control and the like. When the traditional PI controller is used for controlling the direct-current side voltage, although the direct-current voltage stability and the power distribution can be finally met, under the condition that larger interference exists or a model is inaccurate, the control precision and the performance are limited, and higher requirements cannot be met. The sliding mode controller is less dependent on a system, has stronger robustness and good dynamic performance, but has the influence of the inherent system buffeting on the control performance, high energy consumption loss and few practical applications. Compared with the traditional double-loop PI control, the predicted current control reduces loss and obtains better performance indexes, but the power switch of the predicted current control is frequently switched on and off, so that the control frequency cannot be well fixed, the output filtering design is difficult, and the possibility of actual use is reduced. The self-adaptive control method based on the voltage or the control parameters is complex to realize, occupies more resources in control calculation, and has unsatisfactory voltage dynamic performance on the direct current side. The control method for the current inner loop of the DC-DC converter comprises the control methods such as hysteresis control and the like besides the method, and parameters need to be adjusted to meet different dynamic response requirements of an inner loop and an outer loop, wherein the traditional PI control algorithm can realize good tracking of given current, but can not realize good non-static tracking of dynamic instruction signals containing a direct current bus which change at any moment; hysteresis control is a transient feedback control method, has the advantages of high precision, high response speed and the like, can obtain better control performance, but has larger switching frequency fluctuation and quite difficult output filtering design.
Disclosure of Invention
The invention aims to overcome the defects of the control method, and provides a DC-DC converter cascade linear active disturbance rejection voltage control method aiming at a DC-DC converter in a direct current micro-grid.
The technical scheme adopted by the invention is as follows:
a DC-DC converter cascade linear active disturbance rejection voltage control method comprises the following steps:
step 1: sampling DC-DC converter voltage VoBus voltage VdcInductor current IL；
Step 2: will DC-DC converter output voltage VoAnd a DC-DC converter reference voltage value Vdc_refComparing to obtain a voltage error signal evThe error signal is processed by the outer loop LADRC controller to obtain the current inner loop command current IL_ref；
And step 3: the inductive current I detected in the step 1 is measuredLAnd obtaining the current inner ring instruction current I in the step 2L_refComparing to obtain a current error signal eiThe error signal passes through an inner ring LADRC controller to obtain an output control quantity u;
and 4, step 4: comparing the output control quantity u with a given carrier signal in the step 3 to generate a switching pulse signal PWM, controlling a power device, and stabilizing the bus voltage or adjusting the output power according to an instruction;
and 5: next duty cycle detection DC-DC converter VoAnd outputCurrent IoAnd (4) whether the instruction requirement and the power distribution requirement are met, if not, returning to the step 1, and repeating the steps 1-5.
In step 1, taking a dc load formed by a commonly used dc bus post-stage Buck converter in a dc microgrid as an example, VdcIs the voltage of the connected direct current bus; voOutputting voltage for the DC-DC converter; iL is an inductive current; r is a load resistor; l is an energy storage inductor; c is an output filter capacitor; reCAnd ReLIs the equivalent internal resistance of the inductor L and the capacitor C.
In order to simplify the design of the DC-DC converter, the switch is set in an ideal state, the influence of the switch parameter is ignored, and an average mathematical model is established as follows:
Figure BDA0002577292520000021
the active disturbance rejection control mechanism is to realize the compensation of the total disturbance f of the external disturbance and the internal disturbance through the observation of an Extended State Observer (ESO), so that the system becomes a linear integral system, the control requirement can be realized through the adoption of simple proportion P or PD control, for the system (1), a linear extended observer (LESO) can be respectively designed for the dynamic equations of the energy storage elements (L) and (C), and the cascade control of two first-order integral systems of the model is realized through the compensation.
In step 2, the second equation of the rewriting system (1) is as follows (2):
Figure BDA0002577292520000031
for a given DC-DC converter reference voltage value Vo_refComparing the voltage with the sampled output voltage of the DC-DC converter to obtain a voltage error signal evObtaining a desired current value I by LADRC controlL_ref。
For simplifying the derivation process, assuming that the inner loop current is well controlled, i.e. the gain of the closed loop transfer function of the inner loop is 1, the transfer function of the outer loop of the cascade voltage of the DC-DC converter is:
Figure BDA0002577292520000032
this is a typical first order system, and the closed loop transfer function after control can be obtained by simplifying pole-zero configuration to PI control as follows:
Figure BDA0002577292520000033
the traditional PI controller is simple to implement, when a load suddenly changes in a large range and the voltage of a direct current bus changes violently, the PI controller cannot meet the requirements of a DC-DC converter on the steady-state performance and the dynamic performance, the output voltage cannot be stably controlled in time, adverse effects can be caused on the load behind the DC-DC converter, the fluctuation can be caused on the direct current bus, and the stability of the whole direct current microgrid is influenced.
In order to overcome the defects, the invention adopts a cascade outer ring LADRC controller at the output voltage, and the control principle is as follows: according to the output voltage and the input control quantity of the cascade outer ring, a cascade outer ring extended state observer LESO is established, the observation of the total disturbance is completed through the cascade outer ring extended state observer LESO, the total disturbance is compensated when the controller is designed, if the observation error of the total disturbance is very small, the estimation value is considered to be equal to the actual value of the total disturbance under an ideal condition, a first-order outer ring system is changed into a first-order integral system after compensation, the controller parameters only need to adjust simple proportion P or PD control parameters, and the control can be completed, and the specific realization is as follows:
according to the formula (2), let Vo be y1,iL＝u1Is obtained by
Figure BDA0002577292520000034
Wherein y is1Is the outer loop output of the cascade voltage u1For voltage outer loop input control quantity, b 11/C as target gain, f1(y1,u1And w) is the total disturbance of the system. Continue to order x1＝y1,x2＝f1(y1,u1W) is a state variable, where x2To expandThe state space equation of the outer ring of the obtained cascade voltage is as follows:
Figure BDA0002577292520000041
wherein
Figure BDA0002577292520000042
C1＝[10],
Figure BDA0002577292520000043
Then the following linear extended state observer LESO can be established:
Figure BDA0002577292520000044
wherein L is1＝[β11β12]TBy proportional control, i.e.
Figure BDA0002577292520000045
By compensating for the total disturbance, the final control quantity is:
Figure BDA0002577292520000046
where R is1＝[r10]TIs the output voltage reference, Kp1＝[kp11]/b1And (4) controlling the gain of the controller.
Substituting equation (7) into equation (5) can yield:
Figure BDA0002577292520000047
as can be seen from equation (8), the disturbance amount is observed by the extended state observer
Figure BDA0002577292520000048
After compensation is carried out in the control input quantity, the cascade voltage outer ring becomes a first-order integral system, and the input control quantity of the first-order integral system is only matched with the gain kp of the controller1It is related.
What needs to be designed next is the linear extended observer LESO parameter L1And a controller parameter kp1. According to the pole allocation method, the observation bandwidth of the linear extended observer LESO is allocated to be wo1So that its closed-loop characteristic equation is (s + w)o1)20; the control bandwidth of the same configuration controller is wc1So that its closed-loop characteristic equation is s + w c10, the LESO parameter L of the linear extended observer is obtained1And a controller parameter kp1Respectively as follows:
β11＝2wo1,β12＝wo1 2,kp1＝wc1(9)
the open-loop transfer function of the outer ring of the cascade voltage can be obtained by the following equations (5), (6), (7) and (9):
Gop_outer(s)＝HvGF1GC1(s)Gcl_inner(s)GP1(s) (10)
where Hv is the voltage feedback coefficient,
Figure BDA0002577292520000049
GF1(s) to the error signal evHaving a filter function, GC1And(s) realizing the control action on the outer ring of the cascade voltage.
Finally, adjusting LESO bandwidth w of the linear extended observero1And controller bandwidth wc1And a target gain b1Obtaining the amplitude margin and the phase angle margin of the system requirement; compared with the traditional double-loop PI control, the DC-DC converter controlled by the LADRC can well meet the requirements on the steady-state performance and the transient-state performance of the system when the load is subjected to large-range sudden change and the voltage of a direct-current bus is changed violently.
In step 3, the first equation of the formula (1) is rewritten as the following formula (12):
Figure BDA0002577292520000051
for the calculation in step 2The expected reference current value IL_refComparing with the sampled DC-DC converter inductive current to obtain a current error signal eiLObtaining a control input V through cascade current inner loop LADRC controlcon。
Before LADRC control is adopted, the transfer function of the cascade current inner ring of the DC-DC converter is as follows:
Figure BDA0002577292520000052
this is a typical first order system, and the closed loop transfer function after control can be obtained by simplifying pole-zero configuration to PI control as follows:
Figure BDA0002577292520000053
the traditional PI controller is simple to implement, when a load suddenly changes in a large range and the voltage of a direct current bus changes violently, the PI controller cannot meet the requirements of a DC-DC converter on the steady-state performance and the dynamic performance, the output voltage cannot be stably controlled in time, adverse effects can be caused on the load behind the DC-DC converter, the fluctuation can be caused on the direct current bus, and the stability of the whole direct current microgrid is influenced.
In order to overcome the defects, the invention adopts an LADRC controller in the inner loop of the cascade inductor current, and the control principle is as follows: according to the sampling inductive current and the cascade inner ring input control quantity, a cascade inner ring extended state observer LESO is established, the observation of the total disturbance is completed through the cascade inner ring extended state observer LESO, the total disturbance is compensated when the controller is designed, if the total disturbance observation error is small, the estimation value is considered to be equal to the actual value of the total disturbance under ideal conditions, a first-order inner ring system is changed into a first-order integral system after compensation, the controller parameters only need to adjust simple proportion P or PD control parameters, and the control can be completed, and the specific realization is as follows:
according to the formula (12), let iL be y2,d＝u2Is obtained by
Figure BDA0002577292520000054
Wherein y is2Is the output of the inner loop of the cascade inductor current u2Input of control quantities for the inner loop of the inductor current cascade, b2＝ViL is the target gain, f1(y2,u2And w) is the total disturbance of the system. Continue to order x1＝y2,x2＝f2(y2,u2W) is a state variable, where x2To expand the state variable, the state space equation of the cascade inductor current inner loop can be obtained as follows:
Figure BDA0002577292520000061
wherein
Figure BDA0002577292520000062
C2＝[10],
Figure BDA0002577292520000063
Then the following linear extended state observer LESO can be established:
Figure BDA0002577292520000064
wherein L is2＝[β21β22]TBy proportional control, i.e.
Figure BDA0002577292520000065
By compensating for the total disturbance, the final control quantity is:
Figure BDA0002577292520000066
where R is2＝[r20]TIs the output voltage reference, Kp2＝[kp21]/b2And (4) controlling the gain of the controller.
Substituting equation (17) into equation (15) can yield:
Figure BDA0002577292520000067
as can be seen from equation (18), the disturbance amount is observed by the extended state observer
Figure BDA0002577292520000068
After compensation is carried out in the control input quantity, the cascade inductor current inner loop becomes a first-order integral system, and the input control quantity of the first-order integral system is only equal to the gain kp of the controller2It is related.
What needs to be designed next is the linear extended observer LESO parameter L2And a controller parameter kp2. According to the pole allocation method, the observation bandwidth of the linear extended observer LESO is allocated to be wo2So that its closed-loop characteristic equation is (s + w)o2)20; the control bandwidth of the same configuration controller is wc2So that its closed-loop characteristic equation is s + w c20, the LESO parameter L of the linear extended observer is obtained2And a controller parameter kp2Respectively as follows:
β21＝2wo2,β22＝wo2 2,kp2＝wc2(19)
the open loop transfer function of the inner loop of the cascade inductor current can be obtained by the equations (15), (16), (17) and (19) as follows:
Gop_outer(s)＝HsGF2GC21(s)GP2(s) (20)
wherein Hs is a voltage feedback coefficient,
Figure BDA0002577292520000071
GF2(s) to the error signal eiLHaving a filter function, GC2And(s) realizing the control function of the cascade inductor current inner loop.
Finally, adjusting LESO bandwidth w of the linear extended observero2And controller bandwidth wc2And a target gain b2Combining the parameters adjusted in the step 2 to obtain an amplitude margin and a phase angle margin required by the system; by cascaded LADRC control, as compared to conventional dual-loop PI controlThe manufactured DC-DC converter can well meet the requirements on the steady-state and transient-state performances of the system when the load is suddenly changed in a large range and the voltage of the direct-current bus is changed violently.
In step 4, the actual input control quantity V obtained by using the cascade LADRC control in step 2 and step 3conAnd comparing the PWM with a given triangular carrier to obtain an actual control pulse PWM, and controlling the on and off of a power switch device in the DC-DC converter after passing through a driving circuit to achieve the final control effect.
In the step 5, the output voltage Vo, the inductive current iL and performance indexes of other DC-DC converters are measured through an oscilloscope or a virtual instrument, whether the performance indexes meet the design requirements or not is judged, if the performance indexes do not meet the design requirements, the step 1 is returned, and the steps 1 to 5 are repeated.
The invention discloses a DC-DC converter cascade linear active disturbance rejection voltage control method, which has the following technical effects:
1: aiming at a DC-DC converter in a direct current micro-grid, through the design of a cascade linear active disturbance rejection controller, the steady-state performance and the transient response speed of a system when the load changes suddenly in a large range and the voltage of a direct current bus changes violently are improved, the adverse effect of the DC-DC converter on load equipment and the influence on the bus voltage stability of the direct current micro-grid are reduced, and the running stability of the direct current micro-grid is improved.
2: the DC-DC converter cascade linear active disturbance rejection voltage control method effectively avoids overvoltage and overcurrent impact when a system is started.
3: the DC-DC converter cascade linear active disturbance rejection voltage control method can realize smaller transient voltage drop and shorter transient tracking time and tracking precision in the transient process of a voltage signal.
Drawings
Fig. 1 is a flow chart of a method for controlling cascade linear active disturbance rejection voltage of a DC-DC converter.
Fig. 2 is a topological diagram of a DC-DC converter cascade linear active disturbance rejection voltage control main circuit.
Fig. 3 is a control structure diagram of a cascade linear active disturbance rejection voltage control method of a DC-DC converter.
Fig. 4 is a voltage control block diagram of the cascaded linear active disturbance rejection.
Fig. 5(a) is a waveform diagram of a dynamic process experiment when the DC-DC converter is in light load (10% rated power).
Fig. 5(b) is a waveform diagram of a dynamic process experiment at half load (50% rated power) of the DC-DC converter.
Fig. 5(c) is a waveform diagram of a dynamic process experiment when the DC-DC converter is fully loaded (100% rated power).
FIG. 5(d) is a waveform diagram of a dynamic process experiment when the DC bus voltage of the DC-DC converter fluctuates by + -20%.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited to these examples.
FIG. 1 is a flow chart of a method for controlling cascade linear active disturbance rejection voltage of a DC-DC converter.
A DC-DC converter cascade linear active disturbance rejection voltage control method comprises the following specific steps:
step 1: sampling DC-DC converter voltage VoBus voltage VdcInductor current IL；
Step 2: will DC-DC converter output voltage VoAnd a DC-DC converter reference voltage value Vdc_refComparing to obtain a voltage error signal evThe error signal is processed by the outer loop LADRC controller to obtain the current inner loop command current IL_ref；
And step 3: the inductive current I detected in the step 1 is measuredLAnd obtaining the current inner ring instruction current I in the step 2L_refComparing to obtain a current error signal eiLThe error signal passes through an inner ring LADRC controller to obtain an output control quantity u;
and 4, step 4: comparing the output control quantity u with a given carrier signal in the step 3 to generate a switching pulse signal PWM, controlling a power device, and stabilizing the bus voltage or adjusting the output power according to an instruction;
and 5: next duty cycle detection DC-DC converter VoAnd an output current IoWhether the instruction requirement and the power distribution requirement are met, if not, thenAnd returning to the step 1, and repeating the steps 1-5.
Fig. 2 is a topological diagram of a DC-DC converter cascade linear active disturbance rejection voltage control main circuit.
Taking the dc load formed by the commonly used dc bus post-stage Buck converter in the dc micro-grid as an example, VdcIs the voltage of the connected direct current bus; voOutputting voltage for the DC-DC converter; iL is an inductive current; r is a load resistor; l is stored energy
An inductance; c is an output filter capacitor; reCAnd ReLIs the equivalent internal resistance of the inductor L and the capacitor C.
In order to simplify the design of the DC-DC converter, the switch is set in an ideal state, the influence of the switch parameter is ignored, and an average mathematical model is established as follows:
Figure BDA0002577292520000081
the active disturbance rejection control mechanism is to realize the compensation of the total disturbance f of the external disturbance and the internal disturbance through the observation of an Extended State Observer (ESO), so that the system becomes a linear integral system, the control requirement can be realized through the adoption of simple proportion P or PD control, for the system (1), a linear extended observer (LESO) can be respectively designed for the dynamic equations of the energy storage elements (L) and (C), and the cascade control of two first-order integral systems of the model is realized through the compensation.
Fig. 3 is a control structure diagram of a cascade linear active disturbance rejection voltage control method of a DC-DC converter.
As shown in fig. 3, the DC-DC converter cascade linear active disturbance rejection voltage control proposed by the present invention is a cascade larcd control method, and can form a multi-stage cascade control according to the number of energy storage elements or the number of control nodes in the main circuit. The energy storage elements of the main circuit shown in the figure are an inductor L and an output filter capacitor C, and 2-stage cascade control is adopted. The control principle of the cascade voltage outer ring is as follows: establishing a cascade outer ring extended state observer LESO according to the output voltage and the cascade voltage outer ring input control quantity, finishing the observation of the total disturbance through the cascade outer ring extended state observer LESO, and designing the controllerThe total disturbance is compensated, if the observation error of the total disturbance is very small, the estimated value is considered to be equal to the actual value of the total disturbance under an ideal condition, so that the first-order outer ring system is changed into a first-order integral system after compensation, and the controller parameters can be controlled only by adjusting simple proportion P or PD control parameters. The output quantity of the cascade voltage outer ring is used as the current reference value I of the cascade inductance current inner ringL_refThe inner loop of the current adopts LADRC control, and the control principle is as follows: the method comprises the steps of establishing a cascade inner ring extended state observer LESO according to sampling inductive current and cascade inner ring input control quantity, finishing observation of total disturbance through the cascade inner ring extended state observer LESO, compensating the total disturbance in the design of a controller, and if the total disturbance observation error is small, considering that the estimated value is equal to a total disturbance actual value under an ideal condition, enabling a first-order inner ring system to become a first-order integral system after compensation, wherein the controller parameters can be finished only by adjusting simple proportion P or PD control parameters. By detecting the bus voltage of the direct-current microgrid, the inductive current of the DC-DC converter and the output voltage of the DC-DC converter, the steady-state performance and the transient response speed of the system of the DC-DC converter can be improved when the load is suddenly changed in a large range and the voltage of the direct-current bus is severely changed by adopting the cascade linear active disturbance rejection voltage control method provided by the invention, and the stability of the direct-current microgrid is further enhanced.
Fig. 4 is a voltage control block diagram of a cascaded linear active disturbance rejection.
According to a dynamic balance equation of the C end of the output filter capacitor, obtaining a transfer function of a cascade voltage outer ring as follows:
Figure BDA0002577292520000091
according to the dynamic balance equation of the inductor current L, the transfer function of the cascade inductor current inner loop can be obtained as follows:
Figure BDA0002577292520000092
in the formula, VdcIs the voltage of a direct current micro-grid bus; r is negativeA load resistor; l is an energy storage inductor; c is an output filter capacitor; reCAnd ReLIs the equivalent internal resistance of the inductor L and the capacitor C.
According to the design idea of a cascade active disturbance rejection controller of a DC-DC converter, a current closed loop transfer function is Gcl_inner(s) if the inductor current inner loop output can completely track a given input, and the cascade inductor current inner loop gain can be replaced by a constant, then the voltage outer loop open loop transfer function is obtained as:
Gop_outer(s)＝HvGC1(s)Gcl_inner(s)GP1(s)
in the figure, Hv is a voltage feedback coefficient,
Figure BDA0002577292520000101
Figure BDA0002577292520000102
wherein G isF1(s) to the error signal evHaving a filter function, GC1(s) effecting control of the outer ring of the cascade voltage, beta11、β12Is the LESO parameter, kp, of a linear extended state observer of a cascade outer loop1Is a controller parameter.
According to the pole allocation method, the observation bandwidth of the cascade outer ring linear expansion observer LESO is allocated to be wo1So that its closed-loop characteristic equation is (s + w)o1)20; configuring the control bandwidth of the controller to be wc1So that its closed-loop characteristic equation is s + w c10, so as to obtain the LESO parameter beta of the cascade outer loop linear extended observer11、β12And a controller parameter kp1Are each beta11＝2wo1,β12＝wo1 2,kp1＝wc1。
The LADRC control open-loop transfer function of the inner loop of the cascade inductor current is as follows:
Gop_inner(s)＝HsGC2(s)GP2(s)/Vtrm
wherein Hs is the feedback coefficient of the inductive current,
Figure BDA0002577292520000103
Figure BDA0002577292520000104
wherein G isF2(s) to the error signal eiLHaving a filter function, GC2(s) effecting control of the inner loop of the inductor current in cascade, beta21、β22Is the LESO parameter, kp, of a linear extended state observer of a cascade inner loop2Is a controller parameter
According to the pole allocation method, the observation bandwidth of the LESO of the cascade inner-loop linear expansion observer is allocated to be wo2So that its closed-loop characteristic equation is (s + w)o2)20; configuring the control bandwidth of the cascade inner ring controller to be wc2So that its closed-loop characteristic equation is s + w c20, the LESO parameter L of the cascade inner ring linear expansion observer can be obtained2And a controller parameter kp2Respectively as follows: beta is a21＝2wo2,β22＝wo2 2,kp2＝wc2
Gwd1(s)、Gwd2(s) are output voltage disturbance and inductive current disturbance respectively, and after cascade linear active disturbance rejection control, a disturbance transfer function is as follows:
Figure BDA0002577292520000111
Figure BDA0002577292520000112
from the analysis of the experimental results, it can be seen from fig. 5(a), 5(b) and 5(c) that at light load (10% of rated power), half load (50% of rated power) and full load, the tandem LADRC control can rapidly control the voltage to a desired value at the starting time without overshoot, with a regulation time of about 2 ms; meanwhile, when the load resistance value is halved and the disturbance occurs, the transient voltage drop and transient adjusting time effects of the cascade LADRC are good, no overshoot exists, and the transient voltage drop and transient adjusting time effects are superior to PI double-loop control. Fig. 5(d) shows that the transient droop and settling time of the cascade LADRC control is less than 0.1V, the settling time is about 1ms, and the transient droop and settling time is better than the dual loop PI control when the bus voltage fluctuates ± 20%. It is obvious from fig. 5 that, under the condition of wide-range load disturbance and wide-range fluctuation of the DC bus voltage, the tandem linear active disturbance rejection voltage control of the DC-DC converter provided by the present invention is practically effective and feasible.
TABLE 1 Main Circuit and controller parameters
Figure BDA0002577292520000113
TABLE 1
Parameters of the main circuit and the cascade LADRC controller are given by taking a direct current load formed by a direct current bus post-stage Buck converter commonly used in a direct current micro-grid as an example according to FIG. 2. The voltage of a direct-current micro-grid bus is 400V, the output voltage of a DC-DC converter is 96V, the rated output power is 4kW, namely the load rated resistance R is 2.3 omega, and the inductance L of the energy storage element and the output filter capacitor are respectively 0.6mH and 470 uF; the working frequency of the DC-DC converter is 100kHz, and the sampling coefficients of the output voltage and the inductive current are 0.025 and 0.2 respectively; linear extended observer LESO observation bandwidth w of cascade LADRC inductive current inner loopo1Controller bandwidth wc1And a target gain b16280, 37.68 and 1021.28, respectively, Linear extended observer LESO Observation Bandwidth w of the outer Ring of the Cascade LADRC Voltageo2Controller bandwidth wc2And a target gain b22512, 5.652 and 25.532, respectively.

Claims (5)

1. A DC-DC converter cascade linear active disturbance rejection voltage control method is characterized by comprising the following steps:
step 1: sampling DC-DC converter voltage VoBus voltage VdcInductor current IL；
Step 2: will DC-DC converter output voltage VoAnd a DC-DC converter reference voltage value Vdc_refComparing to obtain a voltage error signal evThe error signal is processed by the outer loop LADRC controller to obtain the current inner loop command current IL_ref；
And step 3: the inductive current I detected in the step 1 is measuredLAnd obtaining the current inner ring instruction current I in the step 2L_refComparing to obtain a current error signal eiThe error signal passes through an inner ring LADRC controller to obtain an output control quantity u;
and 4, step 4: comparing the output control quantity u with a given carrier signal in the step 3 to generate a switching pulse signal PWM, controlling a power device, and stabilizing the bus voltage or adjusting the output power according to an instruction;
and 5: next duty cycle detection DC-DC converter VoAnd an output current IoAnd (4) whether the instruction requirement and the power distribution requirement are met, if not, returning to the step 1, and repeating the steps 1-5.
2. The method for controlling the cascaded linear active disturbance rejection voltage of the DC-DC converter according to claim 1, wherein: in step 1, a DC bus post-stage Buck converter forms a DC load VdcIs the voltage of the connected direct current bus; voOutputting voltage for the DC-DC converter; iL is an inductive current; r is a load resistor; l is an energy storage inductor; c is an output filter capacitor; reCAnd ReLIs the equivalent internal resistance of the inductor L and the capacitor C;
in order to simplify the design of the DC-DC converter, the switch is set in an ideal state, the influence of the switch parameter is ignored, and an average mathematical model is established as follows:
Figure FDA0002577292510000011
the active disturbance rejection control mechanism is to realize the compensation of the total disturbance f of the external disturbance and the internal disturbance through the observation of an Extended State Observer (ESO), so that the system becomes a linear integral system.
3. The method for controlling the cascaded linear active disturbance rejection voltage of the DC-DC converter according to claim 2, wherein: the step 2 comprises the following steps: ,
the second equation in the rewrite formula (1) is as follows (2):
Figure FDA0002577292510000012
for a given DC-DC converter reference voltage value Vo_refComparing the voltage with the sampled output voltage of the DC-DC converter to obtain a voltage error signal evObtaining a desired current value I by LADRC controlL_ref；
For simplifying the derivation process, assuming that the inner loop current is well controlled, i.e. the gain of the closed loop transfer function of the inner loop is 1, the transfer function of the outer loop of the cascade voltage of the DC-DC converter is:
Figure FDA0002577292510000021
this is a typical first order system, and the closed loop transfer function after control can be obtained by simplifying pole-zero configuration to PI control as follows:
Figure FDA0002577292510000022
the controller parameters can be controlled only by adjusting simple proportion P or PD control parameters, and the method is specifically realized as follows: :
according to the formula (2), let Vo be y1,iL＝u1Is obtained by
Figure FDA0002577292510000023
Wherein y is1Is the outer loop output of the cascade voltage u1For voltage outer loop input control quantity, b11/C as target gain, f1(y1,u1W) is the total disturbance of the system; continue to order x1＝y1,x2＝f1(y1,u1And w) is a state variable,wherein x2To expand the state variables, the state space equation of the cascade voltage outer loop is obtained as follows:
Figure FDA0002577292510000024
wherein
Figure FDA0002577292510000025
C1＝[1 0],
Figure FDA0002577292510000026
Then the following linear extended state observer LESO can be established:
Figure FDA0002577292510000027
wherein L is1＝[β11β12]TBy proportional control, i.e.
Figure FDA0002577292510000028
By compensating for the total disturbance, the final control quantity is:
Figure FDA0002577292510000029
where R is1＝[r10]TIs the output voltage reference, Kp1＝[kp11]/b1And (4) controlling the gain of the controller.
Substituting equation (7) into equation (5) can yield:
Figure FDA00025772925100000210
as can be seen from equation (8), the disturbance amount is observed by the extended state observer
Figure FDA0002577292510000031
Compensating for control inputThen, the cascade voltage outer loop becomes a first-order integral system, and the input control quantity of the first-order integral system is only equal to the gain kp of the controller1(ii) related;
linear extended observer LESO parameter L1And a controller parameter kp1According to the pole allocation method, the observation bandwidth of the linear expansion observer LESO is allocated to be wo1So that its closed-loop characteristic equation is (s + w)o1)20; the control bandwidth of the same configuration controller is wc1So that its closed-loop characteristic equation is s + wc10, the LESO parameter L of the linear extended observer is obtained1And a controller parameter kp1Respectively as follows:
β11＝2wo1,β12＝wo1 2,kp1＝wc1(9)
the open-loop transfer function of the outer ring of the cascade voltage can be obtained by the following equations (5), (6), (7) and (9):
Gop_outer(s)＝HvGF1GC1(s)Gcl_inner(s)GP1(s) (10)
where Hv is the voltage feedback coefficient,
Figure FDA0002577292510000032
GF1(s) to the error signal evHaving a filter function, GC1(s) realizing the control function of the cascade voltage outer ring;
finally, adjusting LESO bandwidth w of the linear extended observero1And controller bandwidth wc1And a target gain b1And obtaining the amplitude margin and the phase angle margin of the system requirement.
4. The method for controlling the cascaded linear active disturbance rejection voltage of the DC-DC converter according to claim 2, wherein: the step 3 comprises the following steps of,
the first equation in the rewrite equation (1) is the following equation (12):
Figure FDA0002577292510000033
for the desired reference current value I calculated in step 2L_refComparing with the sampled DC-DC converter inductive current to obtain a current error signal eiLObtaining a control input V through cascade current inner loop LADRC controlcon；
Before LADRC control is adopted, the transfer function of the cascade current inner ring of the DC-DC converter is as follows:
Figure FDA0002577292510000034
this is a typical first order system, and the closed loop transfer function after control can be obtained by simplifying pole-zero configuration to PI control as follows:
Figure FDA0002577292510000041
the controller parameters can be controlled only by adjusting simple proportion P or PD control parameters, and the method is specifically realized as follows:
according to the formula (12), let iL be y2,d＝u2Is obtained by
Figure FDA0002577292510000042
Wherein y is2Is the output of the inner loop of the cascade inductor current u2Input of control quantities for the inner loop of the inductor current cascade, b2＝ViL is the target gain, f1(y2,u2W) is the total disturbance of the system, continue to let x1＝y2,x2＝f2(y2,u2W) is a state variable, where x2To expand the state variable, the state space equation of the cascade inductor current inner loop can be obtained as follows:
Figure FDA0002577292510000043
wherein
Figure FDA0002577292510000044
C2＝[1 0],
Figure FDA0002577292510000045
Then the following linear extended state observer LESO can be established:
Figure FDA0002577292510000046
wherein L is2＝[β21β22]TBy proportional control, i.e.
Figure FDA0002577292510000047
By compensating for the total disturbance, the final control quantity is:
Figure FDA0002577292510000048
where R is2＝[r20]TIs the output voltage reference, Kp2＝[kp21]/b2A controller gain;
substituting equation (17) into equation (15) can yield:
Figure FDA0002577292510000049
as can be seen from equation (18), the disturbance amount is observed by the extended state observer
Figure FDA00025772925100000410
After compensation is carried out in the control input quantity, the cascade inductor current inner loop becomes a first-order integral system, and the input control quantity of the first-order integral system is only equal to the gain kp of the controller2(ii) related;
linear extended observer LESO parameter L2And a controller parameter kp2According to the pole allocation method, the observation bandwidth of the linear expansion observer LESO is allocated to be wo2So that its closed-loop characteristic equation is (s + w)o2)20; the control bandwidth of the same configuration controller is wc2So that its closed-loop characteristic equation is s + wc20, the LESO parameter L of the linear extended observer is obtained2And a controller parameter kp2Respectively as follows:
β21＝2wo2,β22＝wo2 2,kp2＝wc2(19)
the open loop transfer function of the inner loop of the cascade inductor current can be obtained by the equations (15), (16), (17) and (19) as follows:
Gop_outer(s)＝HsGF2GC21(s)GP2(s) (20)
wherein Hs is a voltage feedback coefficient,
Figure FDA0002577292510000051
GF2(s) to the error signal eiLHaving a filter function, GC2(s) realizing control of inner loop of series inductor current, and adjusting LESO bandwidth w of linear expansion observero2And controller bandwidth wc2And a target gain b2And combining the parameters adjusted in the step 2 to obtain the amplitude margin and the phase angle margin required by the system.
5. The method for controlling the cascaded linear active disturbance rejection voltage of the DC-DC converter according to claim 1, wherein: in the step 4, the process of the method,
actual input control quantity V obtained by using cascade LADRC control in step 2 and step 3conAnd comparing the PWM with a given triangular carrier to obtain an actual control pulse PWM, and controlling the on and off of a power switch device in the DC-DC converter after passing through a driving circuit to achieve the final control effect.
CN202010657566.7A 2020-07-09 2020-07-09 DC-DC converter cascade linear active disturbance rejection voltage control method Pending CN111884502A (en)

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CN112600286A (en) * 2020-12-15 2021-04-02 大连海事大学 LADRC-based charge and discharge control method and device
CN113364288A (en) * 2021-06-23 2021-09-07 安徽工业大学 Boost type DC-DC converter double closed loop control method and circuit based on LADRC
CN113364288B (en) * 2021-06-23 2024-03-22 安徽工业大学 Boost type DC-DC converter double closed-loop control method and circuit based on LADRC
CN113937818A (en) * 2021-11-11 2022-01-14 国网江苏省电力有限公司宿迁供电分公司 Bus voltage stabilization control method for photovoltaic power generation system
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