CN113111298A - Method for online identification of circuit parameters of buck-boost converter - Google Patents

Abstract

A method for online identification of circuit parameters of a buck-boost converter comprises the following steps: selecting a buck-boost converter, selecting a working circuit of the buck-boost converter, selecting an equivalent switch, establishing an equivalent circuit, selecting a state variable, establishing a circuit state equation, selecting a confounding variable, deriving a confounding model equation, selecting a variable forgetting factor least square estimation method, an observation matrix and a parameter matrix, establishing a circuit parameter calculation equation, calculating a parameter matrix estimation value from a current observation value of the observation matrix, and calculating a circuit parameter identification value from the parameter matrix estimation value. By adopting the method, the circuit parameters of the buck-boost converter can be identified on line, the full-range parameters and the switching state under the multi-scene composite working mode are adapted, the forgetting factor can be adjusted in an adaptive mode, the circuit parameter change can be tracked rapidly, and the stable value of the circuit parameters can be estimated accurately.

Description

Method for online identification of circuit parameters of buck-boost converter

Technical Field

The invention relates to a buck-boost converter, in particular to a method for identifying multiple parameters of a buck-boost converter circuit on line.

Background

The buck-boost converter is a power electronic device which performs direct-current voltage and current conversion and transmits energy, and is widely applied to the fields of power energy storage and energy supply in the industries of new energy, communication, electric power and the like; an intelligent and efficient energy storage and supply system is formed by matching with a power battery pack.

The buck-boost converter is a bidirectional buck-boost direct current converter, namely nBuckboost, in which four field effect switch tubes are adopted to form two half bridges, the two half bridges are respectively connected with capacitors in parallel, the midpoints of the two half bridges are connected with inductors in series to form a symmetrical double half bridge middle-mounted inductor H-shaped topological circuit, the positive end or the negative end is a common joint to form a non-isolated double-port three-joint mode, the input and output conversion phases are in the same direction, namely non-inverted polarity.

The buck-boost converter has the advantages of wide working range, high conversion efficiency, low stress of a power device, few elements and small volume; four-switch high-frequency pulse combined modulation is adopted to form a digital multi-mode combined control scheme. In the operation process, the power inductor and the capacitor are abnormal, degraded and aged, so that the performance index exceeds the limit, and the performance attenuation, soft failure, failure and even accidents of the converter are caused; when the equivalent series resistance of the inductor and the capacitor is monitored on line, the equivalent series resistance can be checked by using a parameter preset limit, and a disposal process is carried out when the equivalent series resistance is abnormal, so that the reliability is improved; in the operation process, the load size can be dynamically changed, the input voltage can be changed, the output voltage and the output current can also be changed and set, the stability and the dynamic performance of the converter are difficult to achieve optimal control depending on the conventional voltage and current mode pulse width modulation, when the circuit parameter value is identified on line and the circuit parameter change or disturbance is monitored on line, the control system can adjust according to the actual change parameter and the pulse mode of a nonlinear dynamic control scheme in time, the stability and the dynamic performance are greatly improved or optimized, and the overall performance of the converter is improved; at present, a buck-boost converter can be digitally controlled under complex multi-scene and complex multi-mode working conditions, such as bidirectional power transmission, two-tube pure boost modulation, two-tube pure buck modulation, double-half-period mixed buck-boost modulation, bridge arm synchronous control and asynchronous control, a CCM continuous conduction mode and a DCM discontinuous conduction mode in the control process, but a reasonable and practical parameter online identification technical scheme is lacked; therefore, the performance and the control level of the converter can be improved by identifying the circuit parameters of the buck-boost converter on line, and the practical significance and the use value are very strong.

Disclosure of Invention

The invention aims to provide a method for identifying circuit parameters of a buck-boost converter on line, which has strong universality, is suitable for complex and compound working modes under various working scenes, is suitable for full-range working parameters and switch control states, and is reasonable and practical.

The method for identifying the circuit parameters of the buck-boost converter on line comprises the following steps:

the method comprises the following steps: selecting a buck-boost converter, wherein the buck-boost converter comprises two half bridges formed by four switching tubes, the two half bridges are respectively connected with capacitors in parallel, inductors are connected in series between the middle points of the two half bridges, the buck-boost converter can transmit energy in a designated direction, and the buck-boost converter is a four-switching-tube bidirectional buck-boost direct current converter;

step two: the working circuit of the selected buck-boost converter comprises an input port and an output port which are determined according to the buck-boost converter, the energy transmission direction and the input and output form, a switching tube Q1, a switching tube Q2, a switching tube Q3, a switching tube Q4 and an inductor L_ZAn output capacitor C_ODetermining the input voltage V_IAn output voltage V_OOutput current I_OInductor current I_L；

Step three: according to the working circuit of the buck-boost converter and the state of a switch tube, selecting an equivalent switch, wherein the equivalent switch comprises: input side connection switch ES_IAnd an output side connection switch ES_OInput side freewheeling switch ES_DIOutput-side freewheeling switch ES_ROSelecting a freewheeling diode, the freewheeling diode comprising: input-side freewheeling diode D_IOutput-side freewheeling diode D_OEstablishing an equivalent circuit of the buck-boost converter;

step four: selecting a state variable according to a working circuit of the buck-boost converter and an equivalent circuit thereof, wherein the state variable comprises an inductive current I_LAnd an output voltage V_OEstablishing a circuit state equation of the buck-boost converter;

step five: selecting a state variable, a switch variable and a product according to a circuit state equation of the buck-boost converter, combining and reducing according to the correlation, selecting a confounding variable, and deriving a confounding model equation;

step six: selecting the switch control state of the working circuit of the buck-boost converter, acquiring the switch state values of a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4, and obtaining the switch state values according to the inductive current I_LDetermining an input side connection switch ES in the equivalent circuit_IAnd an output side connection switch ES_OInput side freewheeling switch ES_DIOutput-side freewheeling switch ES_ROThe switch state value of (a);

step seven: selecting a variable forgetting factor least square estimation method, selecting an observation matrix and a parameter matrix by a working circuit of a buck-boost converter according to a hybrid model equation, establishing a least square recursive update equation, selecting a recursive initial value and establishing a circuit parameter calculation equation;

step eight: obtaining an observed value of a buck-boost converter, wherein the observed value comprises: the current time of the inductor current I_LAn output voltage V_OThe current time of the switching state values of the switching tube Q1, the switching tube Q2, the switching tube Q3 and the switching tube Q4 are obtained, and the input side connection switch ES at the current time is obtained in the sixth step_IAnd an output side connection switch ES_OInput side freewheeling switch ES_DIOutput-side freewheeling switch ES_ROAnd (3) according to the seven-variable forgetting factor least square method in the steps, recursively updating the equation, calculating the estimation value of the parameter matrix according to the current observation value of the observation matrix, calculating the equation by the circuit parameters, and calculating to obtain the circuit parameter identification value.

Further, it is characterized byThe buck-boost converter comprises a switching tube VM1, a switching tube VM2, a switching tube VM3, a switching tube VM4, a diode VD1, a diode VD2, a diode VD3, a diode VD4, an inductor Lz, a capacitor Cp, a capacitor Cb, a load resistor R_OP-side port, B-side port; diode VD1, diode VD2, diode VD3, diode VD4, switch tube VM1, switch tube VM2, switch tube VM3 and switch tube VM4 are correspondingly connected in parallel, the positive end of the P-side port is P +, the negative end of the P-side port is P-, the voltage at two ends of the P-side port is Vp, switch tube VM1 is an upper tube, switch tube VM2 is a lower tube to form a P-side half bridge, the positive end of the half bridge is connected with P +, the negative end of the half bridge is connected with P-, the two ends of the half bridge are connected in parallel with a capacitor Cp, the half bridge midpoint is BZp, the positive end of the B-side port is B +, the negative end of the B-side port is B-, the voltage at two ends of the B-side port is Vb, switch tube VM4 is an upper tube, switch tube VM3 is a lower tube to form a B-side half bridge, the half bridge is connected with the positive end and B +, the negative end is connected with B-, the half bridge parallel with Cb-, the capacitor Cb-, the, selecting the positive end or the negative end of the P side port and the B side port as a common joint G to form a bilateral half-bridge H-shaped dual-port network; the switch tube comprises a field effect tube, and the diode VD1, the diode VD2, the diode VD3 and the diode VD4 are parasitic diodes or external diodes corresponding to the field effect tube.

Furthermore, the working circuit of the buck-boost converter is a circuit of the buck-boost converter working according to the energy transmission direction and the input and output mode; when the energy direction flows from the P-side port to the B-side port, the P-side port is an input port, the B-side port is an output port, the P-side port is connected with an input power supply, and the voltage Vp is recorded as an input voltage V_IThe B side port is connected with a load R_OAnd the capacitor Cb of the port on the side B is recorded as an output capacitor C_OVoltage Vb is recorded as output voltage V_OThe current Ib is expressed as the output current I_OSwitching tube VM1 is marked as Q1, switching tube VM2 is marked as Q2, switching tube VM3 is marked as Q3, switching tube VM4 is marked as Q4, and P-side bridge arm is marked as input bridge arm BS_IB side bridge arm is recorded as output bridge arm BS_O(ii) a When the energy direction flows from the B-side port to the P-side port, the B-side port is an input port, the P-side port is an output port, and the B-side port is connected with an input power supply and voltageVb is expressed as the input voltage V_IP-side port access load R_OAnd the capacitance Cp of the P-side port is marked as an output capacitance C_OVoltage Vp is recorded as output voltage V_OThe current Ip is recorded as the output current I_OSwitching tube VM4 is marked as Q1, switching tube VM3 is marked as Q2, switching tube VM2 is marked as Q3, switching tube VM1 is marked as Q4, and a bridge arm at side B is marked as an input bridge arm BS_IAnd the P side bridge arm is recorded as an output bridge arm BS_O。

Further, establishing the equivalent circuit includes: determining a common joint G, wherein the common joint is the positive end of the input port and the positive end of the output port or the negative end of the input port and the negative end of the output port, and the other end point of the input port is an input connection point and is marked as TP relative to the common joint G_IThe other end point of the output port is the output connection point and is marked as TP_OSelecting equivalent circuit elements: input side connection switch ES_IAnd an output side connection switch ES_OInput side freewheeling switch ES_DIOutput-side freewheeling switch ES_ROAn input side freewheeling diode D_IOutput-side freewheeling diode D_O(ii) a The equivalent circuit is that the input connection point TP_IIs connected with a node Si.1, a node Si.0 is connected with a node Sdi.sc, and the node Sdi.1 is connected with a diode D in series_IA diode D connected to the common contact G_IThe polarity of (1) is that the conduction current maintains the follow current direction of the inductor Lz, the node Sdi.0 is connected with the common node G, and the inductor Lz and the resistor R are connected in series between the node Si.sc and the node so.sc_LOutput connection point TP_OConnected with node so.1, and output connection point TP_OAnd node Sro.1 through series diode D_OConnection, diode D_OThe polarity of (1) is that the conduction current maintains the follow current direction of the inductor Lz, the node so.0 is connected with the node Sro.sc, the node Sro.0 is connected with the common junction G, and the output capacitor C_OSeries resistor R_CRear and output connection point TP_OAnd a common contact G connected to an output load R_OBoth end points and the output connection point TP_OAnd a common contact G connection;

the resistor R_LIs the equivalent series resistance of the inductance Lz, the resistance R_CIs an output capacitor C_OAn equivalent series resistance ofNodes Si.sc, Si.1 and Si.0 are input side connection switches ES_IThe state nodes of gating, high value 1 and low value 0, and the node so.sc, the node so.1 and the node so.0 are output side connecting switches ES_OThe gated, high value 1, low value 0 state nodes of (1), the node sdi.sc, the node sdi.1, the node sdi.0 being the input side freewheeling switch ES_DIThe gating, high value 1 and low value 0 state nodes of (1), the nodes Sro.sc, Sro.1 and Sro.0 are output side freewheeling switches ES_RO High value 1, low value 0 state nodes.

Further, the inductive current I is selected according to the equivalent circuit of the buck-boost converter_LAnd an output voltage V_OAs state variable according to the output capacitance C_OAnd a differential equation of the inductance Lz, a connection relation among switch states and a voltage-current equation, and establishing a circuit state equation as follows:

L*dI_L/dt＝S_I*V_I-S_DI*V_DI-S_O*V_O-S_RO*(V_O+V_DO)-R_L*I_L，

C*dV_C/dt＝I_C，I_C＝(S_O+S_RO)*I_L-I_O，I_O＝V_O/R_O，V_O＝V_C+R_C*I_C，

wherein, V_IIs the input supply voltage, Io is the output current and is not 0, R_OIs the load resistance at the output terminal, L is the inductance of the inductor Lz, R_LIs the equivalent series resistance of the inductor Lz, and C is the output capacitor C_OCapacitance, R_CIs an output capacitor C_OEquivalent series resistance of, V_CIs an output capacitor C_OVoltage of, I_CIs an output capacitor C_OCurrent of (V)_DIIs an input-side freewheeling diode D_IConduction voltage drop, V_DOIs an output side freewheeling diode D_OConducting voltage drop; s_IIs an input side connection switch ES_ISwitch state value of, S_DIIs an input-side freewheeling switch ES_DISwitch state value of S_I、S_DITake value 0 or 1 and satisfy the constraint: s_I*S_DI＝0，S_OIs an output side connection switch ES_OSwitch state value of, S_ROIs an output side freewheel switch ES_ROSwitch state value of S_O、S_ROTake value 0 or 1 and satisfy the constraint: s_O*S_RO＝0。

Further, establishing a hybrid model equation of the buck-boost converter comprises:

selecting a confounding variable x_h：x_h1＝I_L，x_h2＝V_O，x_h3＝S_CO*I_L，x_h4＝S_CO*V_O，x_h5＝S_I，

x_h6＝S_DI，x_h7＝S_CO，x_h8＝S_RO，x_h9＝S_IC，x_h10＝S_DC，

Wherein: s_CO＝S_O+S_RO，S_IC＝S_I*S_CO，S_DC＝S_DI*S_CO；

Selected output y ═ x_h1,x_h2]And obtaining a hybrid model equation according to the circuit state equation:

dy₁/dt＝dx_h1/dt＝h_1-1*x_h1+h_1-2*x_h2+h_1-3*x_h3+...+h_1-8*x_h8+h_1-9*x_h9+h_1-10*x_h10

dy₂/dt＝dx_h2/dt＝h_2-1*x_h1+h_2-2*x_h2+h_2-3*x_h3+...+h_2-8*x_h8+h_2-9*x_h9+h_2-10*x_h10

discretizing at k and k-1 according to a sampling period T to obtain a difference equation:

y₁(k)＝(1+T*h_1-1)*x_h1(k-1)+T*h_1-2*x_h2(k-1)+...+T*h_1-10*x_h10(k-1)

y₂(k)＝(1+T*h_2-1)*x_h1(k-1)+T*h_2-2*x_h2(k-1)+...+T*h_2-10*x_h10(k-1)

wherein: h is_1-1＝-R_L/L，h_1-2＝h_1-3＝0，h_1-4＝-1/L，h_1-5＝V_I/L，h_1-6＝-V_DI/L，

h_1-7＝0，h_1-8＝-V_DO*(1+R_C/(1+R_C/R_O))/L，h_1-9＝0，h_1-10＝0，

h_2-1＝0，h_2-2＝-1/(R_O+R_C)/C，h_2-3＝(1/C-R_C*R_L/L)/(1+R_C/R_O)，

h_2-4＝-R_C/L/(1+R_C/R_O)，h_2-5＝0，h_2-6＝0，h_2-7＝0，h_2-8＝0，

h_2-9＝V_I*R_C/L/(1+R_C/R_O)，h_2-10＝-V_DI*R_C/L/(1+R_C/R_O)。

Further, the selected switch code Qsw ═ S_Q1S_Q2S_Q3S_Q4]The controllable subcodes of (1) comprise 0101, 1010, 1001, 0110, 0001, 1000, 0010, 0100 and 0000; selecting equivalent switch state value, the input side connection switch is S_I＝S_Q1The output side connection switch is S_O＝S_Q4Input side freewheeling switch S_DIAnd an output-side freewheeling switch S_ROWhen Qsw is one of 0001, 1000, 0010 and 0100 and the inductive current I is_LWhen greater than 0, S_DI＝S_Q4+S_Q3、S_RO＝S_Q1+S_Q2Otherwise, S_DI＝S _RO0; wherein S is_Q1Is the switching state value, S, of the switching tube Q1_Q2Is the switching state value, S, of the switching tube Q2_Q3Is the switching state value, S, of the switching tube Q3_Q4Is the on of the switching tube Q4An off state value.

Further, the variable forgetting factor least square estimation algorithm is selected, and comprises the following steps:

selecting an observation matrix

The method comprises the following steps:

the selected parameter matrix θ is [ θ ]₁,θ₂]^T，θ_i＝[θ_i1,θ_i2,θ_i3,θ_i4,θ_i5,θ_i6,θ_i7,θ_i8,θ_i9,θ_iA]，i＝1,2；

θ₁₁＝1-R_L*T/L，θ₁₂＝0，θ₁₃＝0，θ₁₄＝-T/L，θ₁₅＝V_I*T/L，θ₁₆＝-V_DI*T/L，

θ₁₇＝0，θ₁₈＝-V_DO*(1+Rc/Kr)*T/L，θ₁₉＝0，θ_1A＝0；θ₂₁＝0，θ₂₂＝1-T/C/R_O/Kr，

θ₂₃＝(1/C-R_C*R_L/L)*T/Kr，θ₂₄＝-R_C*T/L/Kr，θ₂₅＝0，θ₂₆＝0，θ₂₇＝0，θ₂₈＝0，

θ₂₉＝V_I*R_C*T/L/Kr，θ_2A＝-V_DI*R_CT/L/Kr; wherein: kr ═ 1+ R_C/R_O)；

Selecting observer output variablesy₁＝I_L，y₂＝V_OThe observer model equation is selected as follows:

wherein:

is that

According to the sampling period T, the observed value at the k moment;

selecting a variable forgetting factor least square estimation recursion algorithm to obtain an estimated value of a parameter matrix theta;

the least squares recursion update equation is:

y₁(k)、y₂(k) is based on the observed value I of the sampling period T at the time k_L(k)、V_O(k)；e_i(k) Is the prior error, K (k) is the gain matrix, P (k) is the covariance matrix, I is the identity matrix, λ (k) is the forgetting factor, λ (k) is the error_minIs the forgetting factor minimum, λ_maxIs the maximum value of the forgetting factor, a_i(k) Is the base value of the error, S_i(k) Is a regulation function, min (x) is a minimum function, SE (x) is an exponential line function, c_zIs a near zero low value constant, c_sIs the coefficient of sensitivity, c_aIs a base value weighting coefficient;

the initial values for the selected least squares recursive update equation are: λ (0) ═ λ_min，a₁(0)＝a₂(0)＝0，θ₁(0)＝θ₂(0)＝0，P(0)＝10⁴*I，IIs an identity matrix;

according to the current value of the observation matrix, a parameter matrix theta estimated value can be obtained by recursion updating equation and the initial value, and the circuit parameter calculation equation of the buck-boost converter is as follows:

and calculating to obtain a circuit parameter identification value according to the estimated value of the parameter matrix theta and a circuit parameter calculation equation.

Further, the near-zero low-value constant c_zThe value of (a) is 10^ (-6); the base value weighting coefficient c_aIs 0 ≦ c_a<1, when c is_a0, error base value a_i(k) Using the constant a of the initial set value_i(0) When c is_a>0. Error base value a_i(k) Is based on the absolute value of the prior error and on the weighting factor c of the base value_aAn iteratively calculated mean value; the coefficient of sensitivity c_sIs 0.2<c_s<5; said forgetting factor minimum value λ_minIs in the range of 0.75-0.85, the maximum value lambda of the forgetting factor_maxThe value range of (1) is 0.95-0.995; the exponential line function SE (x) is a reference natural number exponent y ═ e ^ (1/x), x>The straight line segment of 0-5 segments is fitted, and the fitting reference point is [ x ]₁＝0.4,y₁＝0.08]、[x₂＝5,y₂＝0.82]、[x₃＝20,y₃＝0.95]、[x₄＝50,y₄＝0.98]，y＝SE(x)：{SE(x)＝0,0≦x<x₁；SE(x)＝(y_j+1-y_j)/(x_j+1-x_j)*(x-x_j)+y_j,x_j≦x<x_j+1,_j＝1,2,3；SE(x)＝1,x₄≦x}。

The invention has the following beneficial effects: the method has the advantages that circuit parameters of the buck-boost converter can be identified on line, the method is practical, the method is suitable for multi-scene complex and composite working modes, full-range working parameters and switch control states, forgetting factors can be adjusted in a self-adaptive mode according to comparison of current errors and error base values, circuit parameter changes can be tracked rapidly, and stable values of the circuit parameters can be identified accurately.

Drawings

FIG. 1 is a flow chart of an implementation of a buck-boost converter circuit parameter online identification method;

FIG. 2 is a schematic diagram of a common negative buck-boost converter circuit;

FIG. 3 is a circuit schematic of a common positive side buck-boost converter;

FIG. 4 is a schematic diagram of the one-way control of the operating circuit of the common negative buck-boost converter;

FIG. 5 is a circuit diagram of a sub-block circuit of a bridge arm partition of a common-negative-end buck-boost converter;

FIG. 6 is a schematic diagram of synchronous and asynchronous control circuitry for common negative buck and boost conversion;

FIG. 7 is a schematic diagram of a common negative buck-boost converter switch control subcode mode circuit;

FIG. 8 is a schematic diagram of an equivalent circuit for the operation of the common negative buck-boost converter;

FIG. 9 is a schematic diagram of an equivalent circuit for operation of the common positive side buck-boost converter;

FIG. 10 is a timing diagram of the tri-mode pulses in the synchronous control buck-boost mode;

FIG. 11 is a timing diagram of a tri-mode pulse in the asynchronous control buck-boost mode;

FIG. 12 is a graph of a fit of a natural exponential function and an exponential line function S (x);

Detailed Description

The present invention will be further described with reference to the following examples.

Embodiment 1 is a dc converter in a power lithium battery energy storage and discharge device, which adopts a common negative terminal buck-boost converter and can complete charging and discharging according to set functions and parameters; rated charge and dischargeThe voltage is 48V, the working range is 40V-57V, the charging and discharging rated current is 15A, the switching control frequency is 200KHz, and the data sampling rate of the data converter and the comparator is 4M; the circuit parameter design ratings are: l10 uH, R_L＝3mΩ、Cp＝Cb＝20μF、R_C＝5mΩ。

Embodiment 1 a flow chart of an online identification method of a buck-boost converter parameter is shown in fig. 1, and the online identification method comprises the following steps:

s11: selecting a buck-boost converter, which consists of four field effect transistors, two capacitors and an inductor, and selecting a common negative terminal;

s12: selecting a working circuit of the buck-boost converter, which is defined according to the energy transmission direction and the input and output structure;

s13: selecting equivalent switches ES_I,ES_O,ES_DI,ES_ROEstablishing an equivalent circuit;

s14: selected state variable I_LAnd V_OEstablishing a circuit state equation;

s15: selecting a confounding variable x_hDeducing a hybrid model equation;

s16: selecting the switching tube state of the buck-boost converter and checking the inductive current I_LDetermining an equivalent switch state value;

s17: least square estimation method for selecting variable forgetting factor and observation matrix

Establishing a recursion updating equation and a selected initial value, and establishing a circuit parameter calculation equation;

s18: obtaining an observed value of a buck-boost converter, comprising_L,V_O,S_I,S_O,S_DI,S_ROCalculating a parameter matrix estimation value and a circuit parameter identification value by using a least square recursion updating equation and a circuit parameter calculation equation;

the parameter selection values in the estimation algorithm are: low value constant c close to zero_z10^ (-6), base value weighting coefficient c_a0.5, coefficient of sensitivity c_s1.0, minimum value of forgetting factor λ_min0.8, maximum value of forgetting factor lambda_max＝0.99。

In example 1, a buck-boost converter, in which a P-side is a power port, a B-side is a battery port, a P-side flows for charging to the B-side, and a B-side flows for discharging to the P-side, is digitally controlled by a multi-mode pulse train in a power transfer direction and an input/output voltage rise/fall relationship, includes: synchronous simple buck pbu.sr, PSJ11 ═ 11,01}, synchronous simple boost pbo.sr, PSJ12 ═ 10,11}, synchronous hybrid buck pbb.sr.down, PSJ13 ═ 11,10,11,01}, synchronous hybrid boost pbb.sr.up, PSJ14 ═ 11,01,11,10}, asynchronous simple buck pbu.dr, PSJ21 ═ 11, Z1}, asynchronous simple boost pbo.dr, PSJ22 ═ 1Z,11}, asynchronous hybrid buck pbb.dr.down, PSJ23 ═ 11,10,11, Z1}, asynchronous hybrid boost pbb.dr.up, PSJ24 ═ 1Z, Z1,1Z,10 }; wherein, in each switch state SYi, bridge arm state code BSio and switch code Qsw ═ S_Q1S_Q2S_Q3S_Q4]Corresponding, state SY 1: BSio 01, Qsw 0101, state SY 2: BSio 10, Qsw 1010, state SY 3: BSio 11, Qsw 1001, state SY 5: BSio-Z1, Qsw-0001, state SY 6: BSio 1Z, Qsw 1000.

As further described below.

Fig. 2 shows a circuit of a common negative buck-boost converter, comprising: four NMOS field effect switching tubes VM1, VM2, VM3 and VM4, a power inductor Lz and capacitors Cp and Cb; the drain D of the switch tube VM1 is connected with the positive end P + of the P-side port to form a P-side half-bridge positive end, the source S of the switch tube VM2 is connected with the negative end P-of the P-side port to form a P-side half-bridge negative end, the drain D of the switch tube VM2 is connected with the source S of the switch tube VM1 to form a P-side half-bridge midpoint BZp, namely the switch tube VM1 and the VM2 form a P-side half-bridge and a parallel capacitor Cp, the drain D of the switch tube VM4 is connected with the positive end B + of the B-side port to form a B-side half-bridge positive end, the source S of the switch tube VM3 is connected with the negative end B-of the B-side port to form a B-side half-bridge negative end, the drain D of the switch tube VM3 is connected with the source S of the switch tube VM4 to form a B-side half-bridge midpoint BZb, namely the switch tubes VM4 and 82; the diodes VD1, VD2, VD3 and VD4 are parasitic diodes of the field effect switch tube or external diodes; the positive end connection points on the two sides are P + and B +, a negative end common connection point G is formed by P-and B-, and the topological structure is a double-side half-bridge H-shaped double-port network; fig. 3 shows the circuit composition of the common positive side buck-boost converter.

The buck-boost converter can transmit energy in a designated direction, fig. 4 shows a one-way control schematic diagram of the common-negative-end buck-boost converter, and correspondingly describes control signs of input and output, as shown in a sub-diagram a in fig. 4, when the energy is P side flowing to B side, P + is an input connection point TP_IB + is the output connection point TP_OVoltage Vp ═ V_IVoltage Vb is Vo, current Ib is Io, and capacitor Cb is Co; the switching tubes are VM 1-Q1, VM 2-Q2, VM 3-Q3 and VM 4-Q4; as shown in the diagram B of FIG. 4, when the energy flow direction is B-side flow direction P-side, B + is the input connection point TP_IP + is the output connection point TP_OVoltage Vb ═ V_IThe voltage Vp is Vo, the current Ip is Io, the capacitance Cp is Co, and the switching tubes are VM 1Q 4, VM 2Q 3, VM 3Q 2, and VM 4Q 1.

FIG. 5 is a schematic diagram of a local sub-block of the common-negative-end buck-boost converter, which is divided into three sub-blocks, wherein the left side of the sub-block is provided with an input bridge arm BSi, the input bridge arm BSi comprises Q1, D1, Q2, D2 and Ci, the right side of the sub-block is provided with an output bridge arm BSo, the output bridge arm BSo comprises Q4, D4, Q3 and D3 and Co, the middle points of the two half bridges are connected with an inductor Lz_ISwitch state value S of_IThe expression and output bridge arm BSo is connected with the switch ES from the output side_OSwitch state value S of_OExpression of S_I＝S_Q1、S_O＝S_Q4The freewheeling state of the diode D2 is controlled by the input-side freewheeling switch ES_DIExpressing the freewheeling state of the diode D4 by the output-side freewheeling switch ES_ROExpressing; when the inductive energy storage is generated at BSio 1x, namely when the input is switched on, the inductive freewheeling is generated when the inductive current flows to the output and is conducted by a field effect tube or a diode, the diode freewheeling is only generated at the positions D2 and D4, and the corresponding conduction voltage drop is marked as V_DI、V_DOConstant value is taken and 0.8-1.0V is satisfied, and the follow current state is recorded as follow current switch value S according to the input and output sides_DI、S_ROThe value range of which is subject to the corresponding bridge arm connection switch state value S_I、S_OIs constrained to be full ofFoot S_I*S_DI＝0、S_O*S_RO0, i.e. 0 ≦ S_I+S_DI≦1、0≦S_O+S_RO≦ 1; when adopting synchronous control field effect transistor conduction sense afterflow, the subcode includes: BSio {01,10,11,00}, Qbs ═ 2, when S is present_DI＝S_ROWhen a non-synchronous controlled diode is used to conduct inductor freewheeling, the subcode includes: BSio (Z1, 1Z, Z0, 0Z), Qbs (1), wherein the energy release subcode is a subsequent subcode of the energy storage subcode, the inductance voltage is a negative value and the diode freewheels in the pulse time period of the energy release subcode, and the monitoring inductance current I is monitored at the moment_LAnd judging the positive and negative or zero crossing to obtain the state value S of the follow current switch_DI、S_ROIn subcode Z1 and Z0 modes, when I is_L>0. State value S_DI＝S_Q4+S_Q3＝1、S_RO＝S_Q1+S _Q20 in subcode 1Z and 0Z modes, when I_L>0. State value S_DI＝S_Q4+S_Q3＝0、S_RO＝S_Q1+S_Q2When 1 is equal to_L＝0，S_DI＝S _RO0; fig. 6 shows a synchronous and asynchronous buck-boost control circuit, where sub-graph a in fig. 6 is synchronous buck, sub-graph b in fig. 6 is synchronous boost, sub-graph c in fig. 6 is asynchronous buck, and sub-graph d in fig. 6 is asynchronous boost; FIG. 7 is a state diagram of each subcode mode, and a state of each switch and an equivalent description of the equivalent switch are shown; FIG. 8 shows an equivalent circuit of a common negative buck-boost converter; fig. 9 shows an equivalent circuit of the common positive side buck-boost converter.

The buck-boost converter is a bidirectional buck-boost converter, adopts a digital control algorithm, and can complete regulation by pulse control according to a specified power direction and voltage boost-buck amplitude at a steady state of a certain time; therefore, hardware calibration alignment is completed according to the input-output relationship of the working circuit and the software, and the switch code is recorded as Qsw ═ S_Q1S_Q2S_Q3S_Q4]The switching value satisfies S_Q1+S_Q2≦1、S_Q3+S_Q4≦ 1, Qbs ═ S_Q1+S_Q2+S_Q3+S_Q4Bridge arm with 11xx and xx11 disabled in QswThe upper and lower switching tubes can not be short-circuited, the control and driving of the upper and lower switching tubes of the bridge arm adopt complementary logic, a dead zone is configured between time points of state conversion to prevent common-state conduction, and the field effect tube is internally provided with a diode which can limit conduction after the instruction is turned off; the single bridge arm has three switch states, wherein the instruction 1 is an upper-on lower-off connecting bridge arm, the instruction 0 is an upper-off lower-on connecting common joint, and the instruction Z is a high-resistance state of upper and lower turnoff; the two bridge arm switch state codes are recorded as BSio ═ bi, bo according to the input and output sequence]Bi, bo is 0,1, Z, and the input side is bi is 0,1, Z; s_Q1S_Q2＝[01,10,00]The output side is bo is 0,1 and Z; s_Q3S_Q4＝[10,01,00]The controllable subcodes are 9 in total, namely 01,10,11,00,1Z, Z1,0Z, Z0 and ZZ respectively, and a single period is formed by adopting partial controllable subcodes according to a pulse sequence form, namely PSJ (PSj, j is 1, 2.) to realize multi-mode pulse digital control; the single-period steady-state control mechanism is that energy transmission flows from input to output and voltage regulation is performed when Vo is<When Vi is adopted, a single-cycle StepDown voltage reduction pulse set is adopted, and when Vo is adopted>When Vi is achieved, a single-cycle StepUP boosting pulse set is adopted, and single-cycle control pulses are designed according to the law, so that invalid modulation can be avoided, and uncontrolled energy backflow and voltage backflow can be prevented; the energy transmission of the converter comprises conduction, energy storage and transfer, corresponding to input and output currents, inductive energy comprises conduction, energy storage and energy release, inductive current transmits energy from input to output direction, when the voltage drop of a diode is ignored, the inductive voltage is Vi-Vo, Vi-Vo under different subcodes, the positive and negative of the inductive voltage determine the increase and decrease of the inductive current, when the current increases, the inductive energy storage and the current decreases, when the BSio is 10, the inductive follow current releases energy, and when the BSio is 10, the V is_L＝Vi>0. Inductive energy storage, V at BSio 01/Z1_L＝-Vo<0. Inductive energy release, when BSio is 11, V_LVi-Vo, when Vo<Vi time V_L>0. Inductive energy storage when Vo>Vi time V_L<0. When the inductance releases energy, when BSio is 1Z, Vo is>Vi time V_L＝Vi-Vo<0 electrical energy is released.

When synchronous control is adopted, the upper and lower arms of the bridge arm are complementary switch pairs, no instruction Z is used, and the switch code Qsw meets Qbs which is 2; the bridge arm is corresponding to input and output, and the connection switch state values are respectively S_I、S_OBridge arm upper pipe guideThe on duty ratio is recorded as the on rate Y_I、Y_OThe equation for the inductor neglecting the internal resistance is: LdI_L/dt＝S_IV_I-S_OV_O(ii) a In a single cycle, each subcode BSio, each state SYj, and each total time Tyj are: [ BSio ═ 01, Sy1, Ty1]、[BSio＝10,Sy2,Ty2]、[BSio＝11,Sy3,Ty3,]、[BSio＝00,Sy4,Ty4](ii) a Total time Tc of a single cycle is Ty1+ Ty2+ Ty3+ Ty 4; the input opening time is Tyi-Ty 2+ Ty3, the output opening time is Tyo-Ty 1+ Ty3, the opening ratio Yi is Tyi/Tc, and the opening ratio Yo is Tyo/Tc; balanced voltage-second product of inductance at steady state, dI_L0/dt, Vo/Vi Yi/Yo (Ty2+ Ty3)/(Ty1+ Ty 3); the voltage transmission ratio is independent of Ty4, and the voltage rise and fall are dependent on Ty2-Ty 1; when using tri-modal control { Sy1, Sy2, Sy3}, i.e. subcode [01,10,11]When Ty4 is equal to 0, the inductor average current is small and the efficiency is high.

When the voltage transfer ratio is larger than the near voltage threshold Gth, such as | G-1| > Gth > 2%, the buck-boost control can be performed in a two-tube switching mode, which satisfies Ty2 × Ty1 ═ 0, one side of the bridge arm is controlled by a pure boost or buck pulse, the other side adopts a bypass, the switching tube is in a static on-off state, no switching loss occurs, the efficiency is improved, and the full-cycle pure buck or pure boost mode is realized.

In the buck-boost control, the single-period control may be composed of two independent half-period boost and buck timing sequences, which are denoted as PBB, and is a double-half-period control, which can implement mixed-mode boost or buck, and the right-side subgraphs of fig. 10 and 11 show corresponding pulse control sequences, which is suitable for when the voltage transfer ratio is smaller than the near-voltage threshold Gth, such as | G-1| < Gth < 2%.

Under the low-power conversion condition, when the average current of the inductor is less than the critical current value I_LCIf synchronous control is adopted, the inductor generates reverse follow current, namely the current is less than zero, if asynchronous control is adopted, the current is zero when the inductor energy release is converted from diode follow current to cutoff, and the average current of the inductor is small, so that the efficiency of the converter can be improved.

In embodiment 1, a multimode pulse control in three modes is adopted, synchronous control is adopted when the load current is large, asynchronous control is adopted when the load current is small, mixed boosting and voltage reduction is adopted when the input-output differential pressure is small, and pure boosting and voltage reduction is adopted when the input-output differential pressure is large.

In the left-side diagram of fig. 10, the synchronous simple voltage reduction pbu.sr is performed, when the inductive voltage is greater than zero in the sub-code 11, that is, in the state SY3, the energy storage mode is performed, and when the inductive voltage is less than zero in the sub-code 01, that is, in the state SY1, the freewheeling mode is performed; the middle subgraph of fig. 10 is a synchronous pure boost pbo.sr, the mode in which the inductive voltage is greater than zero when the sub-code 10 is state SY2 is an energy storage mode, the mode in which the inductive voltage is less than zero when the sub-code 11 is state SY3 is a freewheeling mode, and the right subgraph of fig. 10 is a synchronous mixed boost pbb.sr; the left subgraph of fig. 11 is non-synchronous pure buck pbu.dr, the middle subgraph of fig. 11 is non-synchronous pure boost pbo.dr, and the right subgraph of fig. 11 is non-synchronous hybrid boost-buck pbb.dr.

Selecting a load resistor R according to the equivalent circuit of the buck-boost converter_ONot equal to 0, the equivalent circuit equation can be obtained as:

LdI_L/dt＝V_L，V_L+R_LI_L＝V_BZI-V_BZO，V_BZI＝S_I*V_I-S_DI*V_DI，V_BZO＝S_O*V_O+S_RO*(V_O+V_DO)

CdV_C/dt＝I_C，I_C＝(S_O+S_RO)*I_L-I_O，V_O＝V_C+R_C*I_C，I_O＝V_O/R_O

the state differential equation of the equivalent circuit is: dx/dt ═ A_S*x+B_S*u，x＝[I_L,V_O]Is a state variable, u is an input quantity;

dI_L/dt＝a₁₁*I_L+a₁₂*V_O+b₁₁*V_I+b₁₂*V_DI+b₁₃*V_DO

dV_O/dt＝a₂₁*I_L+a₂₂*V_O+b₂₁*V_I+b₂₂*V_DI+b₂₃*V_DO

a₁₁＝-R_L/L，a₁₂＝-S_CO/L，b₁₁＝S_I/L，b₁₂＝-S_DI/L，b₁₃＝-S_RO/L，

a₂₁＝(S_CO*(1/C-R_L*R_C/L)/(1+R_C/R_O)，a₂₂＝-(S_CO*S_CO*R_C/L+1/R_O/C)/(1+R_C/R_O)，

b₂₁＝S_IC*R_C/L/(1+R_C/R_O)，b₂₂＝-S_DC*R_C/L/(1+R_C/R_O)，b₂₃＝-S_RC*R_C/L/(1+R_C/R_O)；

wherein: s_CO＝S_O+S_RO，S_IC＝S_I*S_CO，S_DC＝S_DI*S_CO，S_RC＝S_RO*S_CO；

Decoupling the switching values according to an equation to remove correlation, and the coefficient correlation merging term is S_CO＝S_O+S_RODue to S_O*S_ROThe reduction term associated with a state is S_RC＝S_RO*(S_O+S_RO)＝S_RO，S_CO*S_CO＝S_CO。

The buck-boost converter is a typical hybrid system, the working state of the buck-boost converter has switching and continuous hybrid characteristics, discrete typing is formed according to control quantity and a specific state, and variables in each typing continuously run; from a continuous vector v_hA switching vector s_hOutput vector y_hThe system expression is: dy_h/dt＝A_hv_h+B_h*s_h+C_h+s_hD_hv_h(ii) a Can be composed of a continuous vector v_hA switching vector s_hAnd correlation D_hProduct vector s of_hv_hDefining a confounding variable x_hThe hybrid model equation is: dx (x)_h/dt＝H_hx_h. Defining the confounding variable x_h：x_h1＝I_L，x_h2＝V_O，x_h3＝S_CO I_L，x_h4＝S_COV_O，x_h5＝S_I，x_h6＝S_DI，x_h7＝S_CO，x_h8＝S_RO，x_h9＝S_IC，x_h10＝S_DC，

Hybrid model equation dx for buck-boost converter_h/dt＝H_hx_hComprises the following steps:

dx_h1/dt＝h_1-1*x_h1+h_1-2*x_h2+h_1-3*x_h3+...+b_1-8*x_h8+b_1-9*x_h9+h_1-10*x_h10

dx_h2/dt＝h_2-1*x_h1+h_2-2*x_h2+h_2-3*x_h3+...+b_2-8*x_h8+b_2-9*x_h9+h_2-10*x_h10

wherein: h is_1-1＝-R_L/L，h_1-2＝h_1-3＝0，h_1-4＝-1/L，h_1-5＝V_I/L，h_1-6＝-V_DI/L，h_1-7＝0，

h_1-8＝-V_DO/L(1+R_C/(1+R_C/R_O))，h_1-9＝h_1-10＝0，h_2-1＝0，h_2-2＝-/(R_O+R_C)/C，

h_2-3＝(1/C-R_C*R_L/L)/(1+R_C/R_O)，h_2-4＝-R_C/L/(1+R_C/R_O)，h_2-5＝h_2-6＝h_2-7＝h_2-8＝0，

h_2-9＝V_I*R_C/L/(1+R_C/R_O)，h_2-10＝-V_DI*R_C/L/(1+R_C/R_O)；

According to sampling period T, y ═ x_h1,x_h2]Equation separation for the mixture modelScattering to obtain the difference equation y (k) ═ Hx_h(k-1), namely:

y₁(k)＝x_h1(k)＝(1+T*h_1-1)*x_h1(k-1)+T*h_1-2*x_h2(k-1)+...+T*h_1-10*x_h10(k-1)

y₂(k)＝x_h2(k)＝(1+T*h_2-1)*x_h1(k-1)+T*h_2-2*x_h2(k-1)+...+T*h_2-10*x_h10(k-1)

the buck-boost converter can cause the performance attenuation and even the failure of the converter when the inductor and the capacitor are abnormal in the operation process; when the equivalent series resistance of the inductor and the capacitor is monitored on line, the abnormal handling process can be entered by using parameter limit check, so that the reliability is improved; in the operation process, the input voltage can change, the load resistance and the output current can dynamically change, the output voltage can also change and be set, and when the change or the disturbance of the sensitive parameters are monitored on line and the control system can be adjusted according to a nonlinear dynamic control scheme, the stability and the dynamic performance of the converter are greatly improved or optimized.

The parameter estimation is a method for estimating values according to the optimization of an index function by a known system model equation, the mathematical estimation of model parameters is determined by an observed value of an acquired running state, a least square recursion algorithm is commonly used, the memory length of the algorithm to data is infinite in characteristic, the algorithm can generate a saturated reference phenomenon to old data, the recursion result can not well reflect new data, a forgetting factor is introduced, the algorithm is an algorithm for configuring an attenuation fading memory index function in the recursion process, a weighting coefficient and a progressive attenuation historical data recursion weight are defined according to the exponential power of the forgetting factor, the high value of the forgetting factor can obtain accurate parameter estimation but has poor dynamic tracking performance, the low value of the forgetting factor can quickly track the parameter change but the estimation precision can become poor, therefore, with a fixed forgetting factor, it is difficult to simultaneously satisfy fast tracking changes and accurately estimate the steady state value.

According to the least square estimation algorithm, defining a parameter matrix theta and an observation matrix

The system model equation is

From the acquired data y (k),

An estimate of the parameter θ is obtained; the error of the parameter estimation is the difference between the actual true value and the calculated estimation value, and generally consists of three types of characteristic errors, including variability error, periodicity error and randomness error, wherein the variability error refers to the estimation error caused by the parameter change due to some reasons, such as software initialization stage, hardware reset startup, element short-time abnormity or soft fault, input voltage variation, load variation, output voltage adjustment and the like, in the non-variability error, the randomness error accords with statistical distribution, and the periodicity error accords with the time integral law; in the variability error, when the parameter changes, that is, the current state of the parameter restarts, and a stable estimation needs to be completed by subsequent observation and calculation for a period of time, when the parameter changes, the estimation error is large, and the error e of the model output quantity y is larger than the expected error threshold e_dThe forgetting factor can be reduced at the moment, and the parameter change can be quickly tracked; when the system is in a stable parameter state, the data are observed for a period of time to obtain a relatively stable parameter estimation value, and the error e of the output quantity y is smaller than the expected error threshold e_dAnd the forgetting factor can be increased, the parameter estimation precision is improved, and the parameter stable value is accurately estimated.

Defining an output quantity y₁＝x_h1，y₂＝x_h2Setting a sampling period T, and setting a mixed variable x at the moment of k-1_hObserving;

defining an observation matrix

Defining a parameter matrix θ:

θ₁＝[1-R_L*T/L,0,0,-T/L,V_I*T/L,-V_DI*T/L,0,-V_DO*T/L*(1+Rc/Kr),0,0]

θ₂＝[0,1-T/C/R_O/Kr,(1/C-R_C*R_L/L)T/Kr,-R_CT/L/Kr,0,0,0,0,V_I*R_CT/L/Kr,-V_DI*R_CT/L/Kr]

namely: theta_i＝[θ_i1,θ_i2,θ_i3,θ_i4,θ_i5,θ_i6,θ_i7,θ_i8,θ_i9,θ_iA]I is 1, 2; wherein: kr ═ 1+ R_C/R_O)

According to the confounding variable x_hObservation value observation matrix current value

The output quantity is as follows according to an observer model equation:

the least squares recursion update equation is:

a_i(k)＝(1-c_a)a_i(k-1)+c_a|e_i(k)|，i＝1_,2

S_i(k)＝1-SE(c_sa_i(k)/(|e_i(k)|+c_z))，i＝1,2

S(k)＝min(S_i(k))，i＝1_,2

λ(k)＝λ_min+(λ_max-λ_min)S(k)

the circuit parameter calculation equation is as follows:

thus, the buck-boost converter acquires the observation matrix at the current k and k-1 times in the time period T

The observed value is obtained by updating the equation by least square recursion to obtain the estimated value of the parameter matrix theta, the equation is calculated by the circuit parameters, and the circuit parameter identification value is calculated, wherein the circuit parameter identification value comprises the inductance L of the inductance Lz and the equivalent series resistance R of the inductance Lz_LInput power supply voltage V_ILoad resistance R_OAn output capacitor C_OEquivalent series resistance R of_CAn output capacitor C_OC.

Fig. 12 is a graph fitted with a natural number exponential function y ═ e ^ (-1/x) and an exponential line function se (x), which is a monotonic transition between values 0-1 at an exponential rate of change, and the computational complexity is simplified by using a piecewise linear function se (x).

In the least square recursion updating equation, an error base value a is calculated_i(k) Error e of output quantity y and error expected threshold e_dPush-buttonResidual ratio e_d/e＝c_s*a_i(k)/(|e_i(k)|+c_z) The form of the method comprises the steps of adjusting a forgetting factor through a function SE (x), selecting a lower forgetting factor and quickly tracking observation data when an output quantity error is larger than an expected error threshold, selecting a higher forgetting factor and improving estimation accuracy when the output quantity error is smaller than the expected error threshold, adjusting the forgetting factor in a real-time self-adaptive manner, realizing accurate estimation when parameters are stable, and quickly tracking when the parameters change; error base value a_i(k) When c is_aWhen the value is 0, a fixed initial parameter value a is adopted_i(0) The calculation is simple; when 1 is>c_a>At 0, the absolute value of the prior error | e is adopted_i(k) The weighted average value and the adaptability of the | are better; constant c_zIs to avoid a non-zero small value constant, coefficient c, with a divisor of 0_sIs the sensitivity rate, the sensitivity rate that adjusts the variable forgetting factor between the maximum and minimum.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (9)

1. A method for online identification of circuit parameters of a buck-boost converter is characterized by comprising the following steps:

the method comprises the following steps: selecting a buck-boost converter, wherein the buck-boost converter comprises two half bridges formed by four switching tubes, the two half bridges are respectively connected with capacitors in parallel, inductors are connected in series between the middle points of the two half bridges, the buck-boost converter can transmit energy in a designated direction, and the buck-boost converter is a four-switching-tube bidirectional buck-boost direct current converter;

step two: selecting the working circuit of the buck-boost converter, including determining the output according to the buck-boost converter, the energy transmission direction and the input/output formAn input port and an output port, a switch tube Q1, a switch tube Q2, a switch tube Q3, a switch tube Q4 and an inductor L are determined_ZAn output capacitor C_ODetermining the input voltage V_IAn output voltage V_OOutput current I_OInductor current I_L；

Step three: according to the working circuit of the buck-boost converter and the state of a switch tube, selecting an equivalent switch, wherein the equivalent switch comprises: input side connection switch ES_IAnd an output side connection switch ES_OInput side freewheeling switch ES_DIOutput-side freewheeling switch ES_ROSelecting a freewheeling diode, the freewheeling diode comprising: input-side freewheeling diode D_IOutput-side freewheeling diode D_OEstablishing an equivalent circuit of the buck-boost converter;

step four: selecting a state variable according to a working circuit of the buck-boost converter and an equivalent circuit thereof, wherein the state variable comprises an inductive current I_LAnd an output voltage V_OEstablishing a circuit state equation of the buck-boost converter;

step five: selecting a state variable, a switch variable and a product according to a circuit state equation of the buck-boost converter, combining and reducing according to the correlation, selecting a confounding variable, and deriving a confounding model equation;

step six: selecting the switch control state of the working circuit of the buck-boost converter, acquiring the switch state values of a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4, and obtaining the switch state values according to the inductive current I_LDetermining an input side connection switch ES in the equivalent circuit_IAnd an output side connection switch ES_OInput side freewheeling switch ES_DIOutput-side freewheeling switch ES_ROThe switch state value of (a);

step seven: selecting a variable forgetting factor least square estimation method, selecting an observation matrix and a parameter matrix by a working circuit of a buck-boost converter according to a hybrid model equation, establishing a least square recursive update equation, selecting a recursive initial value and establishing a circuit parameter calculation equation;

step eight: obtaining an observed value of a buck-boost converter, wherein the observed value comprises: at the present momentInductive current I_LAn output voltage V_OThe current time of the switching state values of the switching tube Q1, the switching tube Q2, the switching tube Q3 and the switching tube Q4 are obtained, and the input side connection switch ES at the current time is obtained in the sixth step_IAnd an output side connection switch ES_OInput side freewheeling switch ES_DIOutput-side freewheeling switch ES_ROAnd (3) according to the seven-variable forgetting factor least square method in the steps, recursively updating the equation, calculating the estimation value of the parameter matrix according to the current observation value of the observation matrix, calculating the equation by the circuit parameters, and calculating to obtain the circuit parameter identification value.

2. The method of claim 1, wherein the step of identifying the circuit parameters of the buck-boost converter on-line comprises: the buck-boost converter comprises a switch tube VM1, a switch tube VM2, a switch tube VM3, a switch tube VM4, a diode VD1, a diode VD2, a diode VD3, a diode VD4, an inductor Lz, a capacitor Cp, a capacitor Cb, a load resistor R_OP-side port, B-side port; diode VD1, diode VD2, diode VD3, diode VD4, switch tube VM1, switch tube VM2, switch tube VM3 and switch tube VM4 are correspondingly connected in parallel, the positive end of the P-side port is P +, the negative end of the P-side port is P-, the voltage at two ends of the P-side port is Vp, switch tube VM1 is an upper tube, switch tube VM2 is a lower tube to form a P-side half bridge, the positive end of the half bridge is connected with P +, the negative end of the half bridge is connected with P-, the two ends of the half bridge are connected in parallel with a capacitor Cp, the half bridge midpoint is BZp, the positive end of the B-side port is B +, the negative end of the B-side port is B-, the voltage at two ends of the B-side port is Vb, switch tube VM4 is an upper tube, switch tube VM3 is a lower tube to form a B-side half bridge, the half bridge is connected with the positive end and B +, the negative end is connected with B-, the half bridge parallel with Cb-, the capacitor Cb-, the, selecting the positive end or the negative end of the P side port and the B side port as a common joint G to form a bilateral half-bridge H-shaped dual-port network; the switch tube comprises a field effect tube, and the diode VD1, the diode VD2, the diode VD3 and the diode VD4 are parasitic diodes or external diodes corresponding to the field effect tube.

3. The method of claim 2, wherein the step of identifying the circuit parameters of the buck-boost converter on-line comprises: the working circuit of the buck-boost converter is a circuit which works according to the energy transmission direction and the input and output modes of the buck-boost converter; when the energy direction flows from the P-side port to the B-side port, the P-side port is an input port, the B-side port is an output port, the P-side port is connected with an input power supply, and the voltage Vp is recorded as an input voltage V_IThe B side port is connected with a load R_OAnd the capacitor Cb of the port on the side B is recorded as an output capacitor C_OVoltage Vb is recorded as output voltage V_OThe current Ib is expressed as the output current I_OSwitching tube VM1 is marked as Q1, switching tube VM2 is marked as Q2, switching tube VM3 is marked as Q3, switching tube VM4 is marked as Q4, and P-side bridge arm is marked as input bridge arm BS_IB side bridge arm is recorded as output bridge arm BS_O(ii) a When the energy direction flows from the B-side port to the P-side port, the B-side port is an input port, the P-side port is an output port, the B-side port is connected with an input power supply, and the voltage Vb is recorded as an input voltage V_IP-side port access load R_OAnd the capacitance Cp of the P-side port is marked as an output capacitance C_OVoltage Vp is recorded as output voltage V_OThe current Ip is recorded as the output current I_OSwitching tube VM4 is marked as Q1, switching tube VM3 is marked as Q2, switching tube VM2 is marked as Q3, switching tube VM1 is marked as Q4, and a bridge arm at side B is marked as an input bridge arm BS_IAnd the P side bridge arm is recorded as an output bridge arm BS_O。

4. The method of claim 2, wherein the step of identifying the circuit parameters of the buck-boost converter on-line comprises: establishing an equivalent circuit comprises the following steps: determining a common joint G, wherein the common joint is the positive end of the input port and the positive end of the output port or the negative end of the input port and the negative end of the output port, and the other end point of the input port is an input connection point and is marked as TP relative to the common joint G_IThe other end point of the output port is the output connection point and is marked as TP_OSelecting equivalent circuit elements: input side connection switch ES_IAnd an output side connection switch ES_OInput side freewheeling switch ES_DIOutput-side freewheeling switch ES_ROAn input side freewheeling diode D_IOutput-side freewheeling diode D_O(ii) a The equivalent circuit is that the input connection point TP_IIs connected with a node Si.1, a node Si.0 is connected with a node Sdi.sc, and the node Sdi.1 is connected with a diode D in series_IA diode D connected to the common contact G_IThe polarity of (1) is that the conduction current maintains the follow current direction of the inductor Lz, the node Sdi.0 is connected with the common node G, and the inductor Lz and the resistor R are connected in series between the node Si.sc and the node so.sc_LOutput connection point TP_OConnected with node so.1, and output connection point TP_OAnd node Sro.1 through series diode D_OConnection, diode D_OThe polarity of (1) is that the conduction current maintains the follow current direction of the inductor Lz, the node so.0 is connected with the node Sro.sc, the node Sro.0 is connected with the common junction G, and the output capacitor C_OSeries resistor R_CRear and output connection point TP_OAnd a common contact G connected to an output load R_OBoth end points and the output connection point TP_OAnd a common contact G connection;

the resistor R_LIs the equivalent series resistance of the inductance Lz, the resistance R_CIs an output capacitor C_OThe node si.sc, the node si.1, and the node si.0 are input side connection switches ES_IThe state nodes of gating, high value 1 and low value 0, and the node so.sc, the node so.1 and the node so.0 are output side connecting switches ES_OThe gated, high value 1, low value 0 state nodes of (1), the node sdi.sc, the node sdi.1, the node sdi.0 being the input side freewheeling switch ES_DIThe gating, high value 1 and low value 0 state nodes of (1), the nodes Sro.sc, Sro.1 and Sro.0 are output side freewheeling switches ES_ROHigh value 1, low value 0 state nodes.

5. The method of claim 2, wherein the step of identifying the circuit parameters of the buck-boost converter on-line comprises: selecting the inductive current I according to the equivalent circuit of the buck-boost converter_LAnd an output voltage V_OAs state variable according to the output capacitance C_OAnd a differential equation of the inductance Lz, a connection relation among switch states and a voltage-current equation, and establishing a circuit state equation as follows:

L*dI_L/dt＝S_I*V_I-S_DI*V_DI-S_O*V_O-S_RO*(V_O+V_DO)-R_L*I_L，

C*dV_C/dt＝I_C，I_C＝(S_O+S_RO)*I_L-I_O，I_O＝V_O/R_O，V_O＝V_C+R_C*I_C，

wherein, V_IIs the input supply voltage, Io is the output current and is not 0, R_OIs the load resistance at the output terminal, L is the inductance of the inductor Lz, R_LIs the equivalent series resistance of the inductor Lz, and C is the output capacitor C_OCapacitance, R_CIs an output capacitor C_OEquivalent series resistance of, V_CIs an output capacitor C_OVoltage of, I_CIs an output capacitor C_OCurrent of (V)_DIIs an input-side freewheeling diode D_IConduction voltage drop, V_DOIs an output side freewheeling diode D_OConducting voltage drop; s_IIs an input side connection switch ES_ISwitch state value of, S_DIIs an input-side freewheeling switch ES_DISwitch state value of S_I、S_DITake value 0 or 1 and satisfy the constraint: s_I*S_DI＝0，S_OIs an output side connection switch ES_OSwitch state value of, S_ROIs an output side freewheel switch ES_ROSwitch state value of S_O、S_ROTake value 0 or 1 and satisfy the constraint: s_O*S_RO＝0。

6. The method of claim 5, wherein the step of identifying the circuit parameters of the buck-boost converter on-line comprises: establishing a hybrid model equation of the buck-boost converter, comprising:

selecting a confounding variable x_h：x_h1＝I_L，x_h2＝V_O，x_h3＝S_CO*I_L，x_h4＝S_CO*V_O，x_h5＝S_I，x_h6＝S_DI，x_h7＝S_CO，x_h8＝S_RO，x_h9＝S_IC，x_h10＝S_DC，

Wherein: s_CO＝S_O+S_RO，S_IC＝S_I*S_CO，S_DC＝S_DI*S_CO；

Selected output y ═ x_h1,x_h2]And obtaining a hybrid model equation according to the circuit state equation:

dy₁/dt＝dx_h1/dt＝h_1-1*x_h1+h_1-2*x_h2+h_1-3*x_h3+...+h_1-8*x_h8+h_1-9*x_h9+h_1-10*x_h10

dy₂/dt＝dx_h2/dt＝h_2-1*x_h1+h_2-2*x_h2+h_2-3*x_h3+...+h_2-8*x_h8+h_2-9*x_h9+h_2-10*x_h10

discretizing at k and k-1 according to a sampling period T to obtain a difference equation:

y₁(k)＝(1+T*h_1-1)*x_h1(k-1)+T*h_1-2*x_h2(k-1)+...+T*h_1-10*x_h10(k-1)

y₂(k)＝(1+T*h_2-1)*x_h1(k-1)+T*h_2-2*x_h2(k-1)+...+T*h_2-10*x_h10(k-1)

wherein: h is_1-1＝-R_L/L，h_1-2＝h_1-3＝0，h_1-4＝-1/L，h_1-5＝V_I/L，h_1-6＝-V_DI/L，

h_1-7＝0，h_1-8＝-V_DO*(1+R_C/(1+R_C/R_O))/L，h_1-9＝0，h_1-10＝0，

h_2-1＝0，h_2-2＝-1/(R_O+R_C)/C，h_2-3＝(1/C-R_C*R_L/L)/(1+R_C/R_O)，

h_2-4＝-R_C/L/(1+R_C/R_O)，h_2-5＝0，h_2-6＝0，h_2-7＝0，h_2-8＝0，

h_2-9＝V_I*R_C/L/(1+R_C/R_O)，h_2-10＝-V_DI*R_C/L/(1+R_C/R_O)。

7. The method of claim 2, wherein the step of identifying the circuit parameters of the buck-boost converter on-line comprises: selecting a switch code Qsw ═ S_Q1 S_Q2 S_Q3 S_Q4]The controllable subcodes of (1) comprise 0101, 1010, 1001, 0110, 0001, 1000, 0010, 0100 and 0000; selecting equivalent switch state value, the input side connection switch is S_I＝S_Q1The output side connection switch is S_O＝S_Q4Input side freewheeling switch S_DIAnd an output-side freewheeling switch S_ROWhen Qsw is one of 0001, 1000, 0010 and 0100 and the inductive current I is_LWhen greater than 0, S_DI＝S_Q4+S_Q3、S_RO＝S_Q1+S_Q2Otherwise, S_DI＝S_RO0; wherein S is_Q1Is the switching state value, S, of the switching tube Q1_Q2Is the switching state value, S, of the switching tube Q2_Q3Is the switching state value, S, of the switching tube Q3_Q4Is the switch state value of the switching tube Q4.

8. The method of claim 6, wherein the step of identifying the circuit parameters of the buck-boost converter on-line comprises: the least square estimation algorithm for the selected variable forgetting factor comprises the following steps:

selecting an observation matrix

The method comprises the following steps:

the selected parameter matrix θ is [ θ ]₁,θ₂]^T，θ_i＝[θ_i1,θ_i2,θ_i3,θ_i4,θ_i5,θ_i6,θ_i7,θ_i8,θ_i9,θ_iA]，i＝1,2；

θ₁₁＝1-R_L*T/L，θ₁₂＝0，θ₁₃＝0，θ₁₄＝-T/L，θ₁₅＝V_I*T/L，θ₁₆＝-V_DI*T/L，

θ₁₇＝0，θ₁₈＝-V_DO*(1+Rc/Kr)*T/L，θ₁₉＝0，θ_1A＝0；θ₂₁＝0，θ₂₂＝1-T/C/R_O/Kr，

θ₂₃＝(1/C-R_C*R_L/L)*T/Kr，θ₂₄＝-R_C*T/L/Kr，θ₂₅＝0，θ₂₆＝0，θ₂₇＝0，θ₂₈＝0，

θ₂₉＝V_I*R_C*T/L/Kr，θ_2A＝-V_DI*R_CT/L/Kr; wherein: kr ═ 1+ R_C/R_O)；

Selecting observer output variable y₁＝I_L，y₂＝V_OThe observer model equation is selected as follows:

wherein:

is that

According to the sampling period T, the observed value at the k moment;

selecting a variable forgetting factor least square estimation recursion algorithm to obtain an estimated value of a parameter matrix theta;

the least squares recursion update equation is:

a_i(k)＝(1-c_a)a_i(k-1)+c_a|e_i(k)|，i＝1,2

S_i(k)＝1-SE(c_sa_i(k)/(|e_i(k)|+c_z))，i＝1,2

S(k)＝min(S_i(k))，i＝1,2

λ(k)＝λ_min+(λ_max-λ_min)S(k)

y₁(k)、y₂(k) is based on the observed value I of the sampling period T at the time k_L(k)、V_O(k)；e_i(k) Is the prior error, K (k) is the gain matrix, P (k) is the covariance matrix, I is the identity matrix, λ (k) is the forgetting factor, λ (k) is the error_minIs the forgetting factor minimum, λ_maxIs the maximum value of the forgetting factor, a_i(k) Is the base value of the error, S_i(k) Is a regulation function, min (x) is a minimum function, SE (x) is an exponential line function, c_zIs a near zero low value constant, c_sIs the coefficient of sensitivity, c_aIs a base value weighting coefficient;

the initial values for the selected least squares recursive update equation are: λ (0) ═ λ_min，a₁(0)＝a₂(0)＝0，θ₁(0)＝θ₂(0)＝0，P(0)＝10⁴I, I is the identity matrix;

according to the current value of the observation matrix, a parameter matrix theta estimated value can be obtained by recursion updating equation and the initial value, and the circuit parameter calculation equation of the buck-boost converter is as follows:

and calculating to obtain a circuit parameter identification value according to the estimated value of the parameter matrix theta and a circuit parameter calculation equation.

9. The method of claim 8, wherein the step of identifying the buck-boost converter circuit parameters comprises: the near-zero low value constant c_zThe value of (a) is 10^ (-6); the base value weighting coefficient c_aIs 0 ≦ c_a<1, when c is_a0, error base value a_i(k) Using the constant a of the initial set value_i(0) When c is_a>0. Error base value a_i(k) Is based on the absolute value of the prior error and on the weighting factor c of the base value_aAn iteratively calculated mean value; the coefficient of sensitivity c_sIs 0.2<c_s<5; said forgetting factor minimum value λ_minIs in the range of 0.75-0.85, the maximum value lambda of the forgetting factor_maxThe value range of (1) is 0.95-0.995; the exponential line function SE (x) is a reference natural number exponent y ═ e ^ (1/x), x>The straight line segment of 0-5 segments is fitted, and the fitting reference point is [ x ]₁＝0.4,y₁＝0.08]、[x₂＝5,y₂＝0.82]、[x₃＝20,y₃＝0.95]、[x₄＝50,y₄＝0.98]，y＝SE(x)：{SE(x)＝0,0≦x<x₁；SE(x)＝(y_j+1-y_j)/(x_j+1-x_j)*(x-x_j)+y_j,x_j≦x<x_{j+1,j＝1,2,3}；SE(x)＝1,x₄≦x}。

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