Modeling and control method of current continuous type combined chopper switch

Abstract

The invention relates to a modeling and control method of a current continuous type combined chopper switch. The method comprises the following steps: establishing a closing key of the current continuous type combined chopper switch; establishing a BOOST circuit bonding graph model with a bond or a BUCK circuit bonding graph model with a bond; establishing a state equation of the circuit; and circuit control is realized through model predictive control. The method is suitable for BUCK type and BOOST type chopper switch combinations, unification of models in the on-state and the off-state is achieved, and an on-off keying graph under the condition of continuous current can be established; a model in which the external keys are not changed by the internal keys is finally formed by distinguishing the combination keys formed by the switch combination, carding the causal relationship in the combination keys and dividing the external keys and the internal keys, so that the problem that the model changes along with the switch state when the bonding graph is applied to a circuit at present is solved, the application range of the bonding graph is expanded, and the application range of the bonding graph is expanded. The period is not only not limited to fault diagnosis, but can control the circuit based on a model.

Description

Technical Field

[0001] The present invention relates to the technical field of bond graph models, and in particular to a modeling and control method of a current continuous type combined chopper switch. Background Art

[0002] The bond graph model can establish the state equation of the system and has a wide range of applications in system optimization, control, fault tolerance, etc. However, it is difficult to model switching devices using the bond graph model. For modern power electronic converters, the application of switching devices is extremely important, which makes it difficult to apply the bond graph model in power electronic converters, increasing the difficulty of system modeling. At present, there are also some technologies for bond graph modeling of switching devices, but there are problems such as the need for approximation and the inability to unify the models in the on and off states. Therefore, the overall circuit model established using these switching device models has limitations such as low accuracy and complex models.

[0003] At present, the application of bond graphs in circuits has the problem that the model changes with the switch state. The existing switch-key bond graph model can only be used for fault diagnosis and cannot be used for circuit control. The basis for circuit control is to establish an accurate model that is not affected by the switch state and is stable in the continuous time domain. The current bond graph model cannot achieve the unification of the model when the power switch tube is on and off, thus limiting the scope of application of the model.

[0004] For current continuous circuits, the current control methods are usually voltage closed-loop, current closed-loop or voltage-current dual closed-loop control. The design of the controller depends on the small signal model of the circuit, but the application of small signal models has limitations, which makes the controller unable to achieve the expected control effect. In addition, the parameter design also needs to consider the frequency domain response characteristics of the model. The controller has poor robustness and is easily affected by parameter deviations. Although model predictive control can solve these problems, the models established by existing small signal modeling and other methods cannot obtain the state equation of the system, which makes model predictive control unable to be applied to the above circuits. Summary of the invention

[0005] In order to solve the problem that the prior art requires approximation and the model cannot be unified in the on and off states, the purpose of the present invention is to provide a modeling and control method of a current continuous combined chopper switch that is applicable to both BUCK and BOOST type chopper switch combinations and realizes a unified model in the on and off states.

[0006] To achieve the above object, the present invention adopts the following technical solution: a modeling and control method of a current continuous type combined chopper switch, the method comprising the following steps in sequence:

[0007] (1) Establish the key of the current continuous type combined chopper switch;

[0008] (2) According to the bonding of the current continuous type combined chopper switch, a BOOST circuit bonding graph model with bonding or a BUCK circuit bonding graph model with bonding is established;

[0009] (3) Establishing the state equation of the circuit according to the bonding graph model of the BOOST circuit with bonding or the bonding graph model of the BUCK circuit with bonding;

[0010] (4) Based on the state equation, the circuit is controlled through model predictive control.

[0011] The step (1) specifically comprises the following steps in order:

[0012] (1a) Construct the actual circuit of BOOST type and BUCK type combination: For the combination of the continuous current type combined chopper switch, the switch S and the diode D are equivalent to switches that are alternately turned on. Let the driving signal of the switch S be sw. When sw=1, the switch S is turned on, the potential source Se=0, and the diode D is turned off at this time. The diode D is a current source, that is, the current source Sf=0; when sw=0, the switch S is turned off, the switch S is a current source, that is, Sf=0, and the diode D is turned on at this time. The diode D is a potential source, that is, Se=0; There are two forms of the combination of the continuous current type combined chopper switch, namely the BOOST type and the BUCK type;

[0013] (1b) Determination of causal relationships of BOOST and BUCK type combined keys: In either form, the sw of different switch states is different, the causal relationships of the internal keys are different, but the causal relationships of the edge keys are determined; the edge keys include the first key, the fifth key and the sixth key, and the internal keys include the second key, the third key, the fourth key and the seventh key;

[0014] (1c) Construct a mathematical model of the key:

[0015] The 0 node is a common potential junction, which is used to connect variables with equal voltage in the circuit. For the 0 node, only one input is allowed to be potential, and the potentials of all keys are the same; the 1 node is a common current junction, which is used to connect variables with equal current in the circuit. For the 1 node, only one input is allowed to be current, and the currents of all keys are the same. Under the defined reference direction of energy flow, there are:

[0016]

[0017]

[0018] Where, u1 to u7 are the voltages from the first key to the seventh key, and i1 to i7 are the currents from the first key to the seventh key;

[0019] When sw=1,u7=0,i4=0,then:

[0020]

[0021] When sw=0,i7=0,u4=0,then:

[0022]

[0023] Then the potential-current relationship of the edge bond, i.e. the bond of the current continuous combined chopper switch, is uniformly expressed as:

[0024]

[0025] u1=swu6+(1-sw)u5.

[0026] In step (2), the step of establishing a bonding graph model of a BOOST circuit with bonding specifically refers to:

[0027] For the inductance L, we have:

[0028]

[0029] For the grounding point, there are:

[0030] u6=u8=0 (2)

[0031] For SD keys, there are:

[0032]

[0033] u1=(1-sw)u5=u2-u3 (4)

[0034] Transformed into:

[0035] u3=u2-u1=U in -(sw-1)u5 (5)

[0036] For output, we have:

[0037]

[0038] i4=i5-i7 (7)

[0039]

[0040] In the formula, u1 to u8 are the voltages from the first key to the eighth key, i1 to i7 are the currents from the first key to the seventh key; Uin is the input voltage of the BOOST circuit; R, C, and L are the equivalent load of the circuit, the output filter capacitor, and the boost inductor, respectively;

[0041] Equations (1) to (8) are the BOOST circuit bond graph model. Regardless of whether the driving signal sw of the switch S is a discrete PWM signal or a continuous variable representing the duty cycle, the input and output of the BOOST circuit bond graph model satisfy the BOOST circuit characteristics. Therefore, the switch signal is converted into a continuous signal and the discrete system is treated as a continuous system.

[0042] In step (2), the step of establishing a bonding graph model of a BUCK circuit with bonding specifically refers to:

[0043] For the inductance L, we have:

[0044]

[0045] For the grounding point, there are:

[0046] u5=u8=0(10)

[0047] For SD keys, there are:

[0048]

[0049] u1=swu6=u2-u3 (12)

[0050] Transform

[0051] u3=u2-u1=U in -swu6 (13)

[0052] For output, there are

[0053]

[0054] i4=-i2-i7 (15)

[0055]

[0056] In the formula, u1 to u8 are the voltages from the first key to the eighth key, i1 to i7 are the currents from the first key to the seventh key; Uin is the input voltage of the BOOST circuit; R, C, and L are the equivalent load of the circuit, the output filter capacitor, and the boost inductor, respectively;

[0057] Equations (9) to (16) are the bond graph models of the BUCK circuit. Similarly, no matter the driving signal sw of the switch S is a discrete PWM signal or a continuous variable representing the duty cycle, the input and output of the bond graph model of the BUCK circuit satisfy the characteristics of the BUCK circuit. Therefore, the switch signal is converted into a continuous signal and the discrete system is treated as a continuous system.

[0058] The step (3) specifically refers to: establishing a state equation according to the BOOST circuit bonding graph model, and the input variable u(t) is:

[0059] u(t)=U in (t)

[0060] Where U in (t) is the input voltage of the BOOST circuit at time t;

[0061] The state variable x(t) is:

[0062]

[0063] Where q4 is the charge of capacitor C, p3 is the inductor flux, Then the first differential of the state variable is:

[0064]

[0065] u4 and i3 are represented as:

[0066]

[0067] For i4, there are:

[0068]

[0069] For u3, there are

[0070]

[0071] Among them, u3, u4, u5, u7 are the voltages of the third, fourth, fifth, and seventh keys respectively, i1, i3, i4, i5, i7 are the currents of the first, third, fourth, fifth, and seventh keys respectively, Uin is the input voltage of the BOOST circuit; R, C, L are the equivalent load of the circuit, the output filter capacitor and the boost inductor respectively; sw is the drive signal of the switch S;

[0072] The state equation of the system is obtained as follows:

[0073]

[0074] Where A and B are coefficient matrices, and R is the equivalent load of the circuit.

[0075] The step (4) specifically comprises the following steps in order:

[0076] (4a) Determination of output equation and cost function

[0077] The output equation is:

[0078]

[0079] Then the cost function J is set to:

[0080]

[0081] Where, Ts is the calculation period; u4 and u7 are the voltages of the fourth and seventh keys respectively, C is the output filter capacitor, and q4 is the charge of capacitor C;

[0082] (4b) Model predictive control based on state equation, output equation and cost function:

[0083] Sample u4 and the current i3 of the third key, calculate q4 and p3, and predict the state variables when sw is 0 and 1 respectively according to the following formula:

[0084]

[0085] Where p3 is the inductor flux, R and L are the equivalent load and boost inductance of the circuit respectively; Uin is the input voltage of the BOOST circuit; sw is the drive signal of the switch S; x(t) is the state variable, and u(t) is the input variable;

[0086] Thus, the predicted value of q4 is calculated and substituted into the following formula:

[0087]

[0088] Take the sw corresponding to the minimum J to realize the control of the BOOST circuit.

[0089] It can be seen from the above technical scheme that the beneficial effects of the present invention are: first, the present invention is applicable to both BUCK type and BOOST type chopper switch combinations, and realizes the unification of models in the on and off states, and can establish a switch key bonding diagram under the condition of continuous current; second, by distinguishing the "bond" formed by the switch combination, sorting out the cause and effect relationship within the bond, dividing the external bond and the internal bond, and finally forming a model in which the external bond is not affected by the change of the internal bond, the problem that the current bond diagram is applied in the circuit and the model changes with the switch state is solved, and the application scope of the bond diagram is expanded, and the period is not limited to fault diagnosis, but can control the circuit based on the model; third, the established model does not need to simplify or equate the switch device, and is applicable to both continuous switch signals and discrete switch signals, so the model has high accuracy and the control algorithm based on the model is simple, which helps to improve the control accuracy of the power electronic converter and reduce the burden on the operation processor. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Figure 1 There are two forms of bonding;

[0091] Figure 2 It is a key causal relationship;

[0092] Figure 3 It is a key model of combined chopper switch;

[0093] Figure 4 It is the BOOST circuit bonding diagram;

[0094] Figure 5 This is the BUCK circuit bonding diagram. DETAILED DESCRIPTION

[0095] A modeling method for a current continuous combined chopper switch, the method comprising the following steps in order:

[0096] (1) Establish the key of the current continuous type combined chopper switch;

[0097] (2) According to the bonding of the current continuous type combined chopper switch, a BOOST circuit bonding graph model with bonding or a BUCK circuit bonding graph model with bonding is established;

[0098] (3) Establishing the state equation of the circuit according to the bonding graph model of the BOOST circuit with bonding or the bonding graph model of the BUCK circuit with bonding;

[0099] (4) Based on the state equation, the circuit is controlled through model predictive control.

[0100] The step (1) specifically comprises the following steps in order:

[0101] (1a) Construct the actual circuit of BOOST type and BUCK type combination: For the combination of the continuous current type combined chopper switch, the switch S and the diode D are equivalent to switches that are alternately turned on. Let the driving signal of the switch S be sw. When sw=1, the switch S is turned on, the potential source Se=0, and the diode D is cut off at this time. The diode D is a current source, that is, the current source Sf=0; when sw=0, the switch S is cut off, the switch S is a current source, that is, Sf=0, and the diode D is turned on at this time. The diode D is a potential source, that is, Se=0; There are two forms of the combination of the continuous current type combined chopper switch, namely the BOOST type and the BUCK type, as shown in Figure 1 As shown, no matter which form, the direction of the dotted arrow in the figure is defined as the positive direction of energy flow. Figure 1 The form of (a) is the same as the actual energy flow direction; Figure 1 The form of (b) is opposite to the actual energy flow direction. At this time, the two forms can be unified.

[0102] (1b) Determination of BOOST and BUCK type causal relationships: In either form, the sw of different switch states is different, such as Figure 2As shown, the causal relationship of the internal keys is different, but the causal relationship of the edge keys is determined; the edge keys include the first key, the fifth key and the sixth key, and the internal keys include the second key, the third key, the fourth key and the seventh key;

[0103] (1c) Construct a mathematical model of the key:

[0104] The 0 node is a common potential junction, which is used to connect variables with equal voltage in the circuit. For the 0 node, only one input is allowed to be potential, and the potentials of all keys are the same; the 1 node is a common current junction, which is used to connect variables with equal current in the circuit. For the 1 node, only one input is allowed to be current, and the currents of all keys are the same. Under the defined reference direction of energy flow, there are:

[0105]

[0106] Where, u1 to u7 are the voltages from the first key to the seventh key, and i1 to i7 are the currents from the first key to the seventh key;

[0107] for Figure 2 In Figure (a), when sw=1,u7=0,i4=0,then:

[0108]

[0109] for Figure 2 In Figure (b), when sw=0, i7=0, u4=0, then:

[0110]

[0111] like Figure 3 As shown, the potential-flow relationship of the edge key, that is, the closing key of the current continuous combined chopper switch, is uniformly expressed as:

[0112]

[0113] u1=swu6+(1-sw)u5.

[0114] In step (2), the step of establishing a bonding graph model of a BOOST circuit with bonding specifically refers to:

[0115] For the BOOST circuit, the bonding diagram is as follows Figure 4 As shown:

[0116] For the inductance L, we have:

[0117]

[0118] For the grounding point, there are:

[0119] u6=u8=0 (2)

[0120] S is a switch, D is a diode, and the switch S and the diode D are connected as Figure 1 , and converted into Figure 2 The bond graph model is the SD bond. For the SD bond, we have:

[0121]

[0122] u1=(1-sw)u5=u2-u3 (4)

[0123] Transformed into:

[0124] u3=u2-u1=U in -(sw-1)u5 (5)

[0125] For output, we have:

[0126]

[0127] i4=i5-i7 (7)

[0128]

[0129] In the formula, u1 to u8 are the voltages from the first key to the eighth key, i1 to i7 are the currents from the first key to the seventh key; Uin is the input voltage of the BOOST circuit; R, C, and L are the equivalent load of the circuit, the output filter capacitor, and the boost inductor, respectively;

[0130] Equations (1) to (8) are the BOOST circuit bond graph model. Regardless of whether the driving signal sw of the switch S is a discrete PWM signal or a continuous variable representing the duty cycle, the input and output of the BOOST circuit bond graph model satisfy the BOOST circuit characteristics. Therefore, the switch signal is converted into a continuous signal and the discrete system is treated as a continuous system.

[0131] In step (2), the step of establishing a bonding graph model of a BUCK circuit with bonding specifically refers to:

[0132] For the BUCK circuit, its bonding diagram is as follows Figure 5 As shown:

[0133] For the inductance L, we have:

[0134]

[0135] For the grounding point, there are:

[0136] u5=u8=0 (10)

[0137] For SD keys, there are:

[0138]

[0139] u1=swu6=u2-u3 (12)

[0140] Transform

[0141] u3=u2-u1=U in -swu6 (13)

[0142] For output, there are

[0143]

[0144] i4=-i2-i7 (15)

[0145]

[0146] In the formula, u1 to u8 are the voltages from the first key to the eighth key, i1 to i7 are the currents from the first key to the seventh key; Uin is the input voltage of the BOOST circuit; R, C, and L are the equivalent load of the circuit, the output filter capacitor, and the boost inductor, respectively;

[0147] Equations (9) to (16) are the bond graph models of the BUCK circuit. Similarly, no matter the driving signal sw of the switch S is a discrete PWM signal or a continuous variable representing the duty cycle, the input and output of the bond graph model of the BUCK circuit satisfy the characteristics of the BUCK circuit. Therefore, the switch signal is converted into a continuous signal and the discrete system is treated as a continuous system.

[0148] The step (3) specifically refers to: establishing a state equation according to the BOOST circuit bonding graph model, and the input variable u(t) is:

[0149] u(t)=U in (t)

[0150] Where U in (t) is the input voltage of the BOOST circuit at time t;

[0151] The state variable x(t) is:

[0152]

[0153] Where q4 is the charge of capacitor C, p3 is the inductor flux, Then the first differential of the state variable is:

[0154]

[0155] u4 and i3 are represented as:

[0156]

[0157] For i4, there are:

[0158]

[0159] For u3, there are

[0160]

[0161] Among them, u3, u4, u5, u7 are the voltages of the third, fourth, fifth, and seventh keys respectively, i1, i3, i4, i5, i7 are the currents of the first, third, fourth, fifth, and seventh keys respectively, Uin is the input voltage of the BOOST circuit; R, C, L are the equivalent load of the circuit, the output filter capacitor and the boost inductor respectively; sw is the drive signal of the switch S;

[0162] The state equation of the system is obtained as follows:

[0163]

[0164] Where A and B are coefficient matrices, and R is the equivalent load of the circuit.

[0165] The step (4) specifically comprises the following steps in order:

[0166] (4a) Determination of output equation and cost function

[0167] The output equation is:

[0168]

[0169] Then the cost function J is set to:

[0170]

[0171] Where, Ts is the calculation period; u4 and u7 are the voltages of the fourth and seventh keys respectively, C is the output filter capacitor, and q4 is the charge of capacitor C;

[0172] (4b) Model predictive control based on state equation, output equation and cost function:

[0173] Sample u4 and the current i3 of the third key, calculate q4 and p3, and predict the state variables when sw is 0 and 1 respectively according to the following formula:

[0174]

[0175] Where p3 is the inductor flux, R and L are the equivalent load and boost inductance of the circuit respectively; Uin is the input voltage of the BOOST circuit; sw is the drive signal of the switch S; x(t) is the state variable, and u(t) is the input variable;

[0176] Thus, the predicted value of q4 is calculated and substituted into the following formula:

[0177]

[0178] Take the sw corresponding to the minimum J to realize the control of the BOOST circuit.

[0179] The control method of the corresponding BUCK circuit is the same as that of the BOOST circuit, that is, the state equation of the circuit is established according to the bond graph model of the BUCK circuit with a bond; based on the state equation, the circuit is controlled by model predictive control.

[0180] In summary, the present invention is applicable to both BUCK-type and BOOST-type chopper switch combinations, and realizes the unification of models in the on and off states, and can establish a switch key bonding diagram under the condition of continuous current; by distinguishing the "bonds" formed by the switch combination, sorting out the cause-effect relationship within the bond, dividing the external bonds and the internal bonds, and finally forming a model in which the external bonds are not affected by the changes of the internal bonds, the problem that the current bond diagram is applied in the circuit and the model changes with the switch state is solved, and the application scope of the bond diagram is expanded, and the period is not limited to fault diagnosis, but the circuit can be controlled based on the model; the established model does not need to simplify or equate the switch device, and is applicable to both continuous switch signals and discrete switch signals, so the model has high accuracy and the control algorithm based on the model is simple, which helps to improve the control accuracy of the power electronic converter and reduce the burden on the operation processor.

Claims

1. A modeling and control method for a current continuous combined chopper switch, characterized in that: The method comprises the following steps in order: (1) Establish the key of the current continuous type combined chopper switch; (2) According to the bonding of the current continuous type combined chopper switch, a BOOST circuit bonding graph model with bonding or a BUCK circuit bonding graph model with bonding is established; (3) Establishing the state equation of the circuit according to the bonding graph model of the BOOST circuit with bonding or the bonding graph model of the BUCK circuit with bonding; (4) Based on the state equation, the circuit is controlled through model predictive control.

2. The modeling and control method of the current continuous combined chopper switch according to claim 1, characterized in that: The step (1) specifically comprises the following steps in order: (1a) Construct the actual circuit of BOOST type and BUCK type combination: For the combination of the continuous current type combined chopper switch, the switch S and the diode D are equivalent to switches that are alternately turned on. Let the driving signal of the switch S be sw. When sw=1, the switch S is turned on, the potential source Se=0, and the diode D is turned off at this time. The diode D is a current source, that is, the current source Sf=0; when sw=0, the switch S is turned off, the switch S is a current source, that is, Sf=0, and the diode D is turned on at this time. The diode D is a potential source, that is, Se=0; There are two forms of the combination of the continuous current type combined chopper switch, namely the BOOST type and the BUCK type; (1b) Determination of causal relationships of BOOST and BUCK type combined keys: In either form, the sw of different switch states is different, the causal relationships of the internal keys are different, but the causal relationships of the edge keys are determined; the edge keys include the first key, the fifth key and the sixth key, and the internal keys include the second key, the third key, the fourth key and the seventh key; (1c) Construct a mathematical model of the key: The 0 node is a common potential junction, which is used to connect variables with equal voltage in the circuit. For the 0 node, only one input is allowed to be potential, and the potentials of all keys are the same; the 1 node is a common current junction, which is used to connect variables with equal current in the circuit. For the 1 node, only one input is allowed to be current, and the currents of all keys are the same. Under the defined reference direction of energy flow, there are: Where, u1 to u7 are the voltages from the first key to the seventh key, and i1 to i7 are the currents from the first key to the seventh key; When sw=1,u7=0,i4=0,then: When sw=0,i7=0,u4=0,then: Then the potential-current relationship of the edge bond, i.e. the bond of the current continuous combined chopper switch, is uniformly expressed as: u1=swu6+(1-sw)u5.

3. The modeling and control method of the current continuous combined chopper switch according to claim 1, characterized in that: In step (2), the step of establishing a bonding graph model of a BOOST circuit with bonding specifically refers to: For the inductance L, we have: For the grounding point, there are: u6=u8=0 (2) For SD keys, there are: u1=(1-sw)u5=u2-u3 (4) Transformed into: u3=u2-u1=U in -(sw-1)u5 (5) For output, we have: i4=i5-i7 (7) In the formula, u1 to u8 are the voltages from the first key to the eighth key, i1 to i7 are the currents from the first key to the seventh key; Uin is the input voltage of the BOOST circuit; R, C, and L are the equivalent load of the circuit, the output filter capacitor, and the boost inductor, respectively; Equations (1) to (8) are the BOOST circuit bond graph model. Regardless of whether the driving signal sw of the switch S is a discrete PWM signal or a continuous variable representing the duty cycle, the input and output of the BOOST circuit bond graph model satisfy the BOOST circuit characteristics. Therefore, the switch signal is converted into a continuous signal and the discrete system is treated as a continuous system.

4. The modeling and control method of the current continuous combined chopper switch according to claim 1, characterized in that: In step (2), the step of establishing a bonding graph model of a BUCK circuit with bonding specifically refers to: For the inductance L, we have: For the grounding point, there are: u5=u8=0 (10) For SD keys, there are: u1=swu6=u2-u3 (12) Transform u3=u2-u1=U in -swu6 (13) For output, we have i4=-i2-i7 (15) In the formula, u1 to u8 are the voltages from the first key to the eighth key, i1 to i7 are the currents from the first key to the seventh key; Uin is the input voltage of the BOOST circuit; R, C, and L are the equivalent load of the circuit, the output filter capacitor, and the boost inductor, respectively; Equations (9) to (16) are the bond graph models of the BUCK circuit. Similarly, no matter the driving signal sw of the switch S is a discrete PWM signal or a continuous variable representing the duty cycle, the input and output of the bond graph model of the BUCK circuit satisfy the characteristics of the BUCK circuit. Therefore, the switch signal is converted into a continuous signal and the discrete system is treated as a continuous system.

5. The modeling and control method of the current continuous combined chopper switch according to claim 1, characterized in that: The step (3) specifically refers to: establishing a state equation according to the BOOST circuit bonding graph model, and the input variable u(t) is: u(t)=U in (t) Where U in (t) is the input voltage of the BOOST circuit at time t; The state variable x(t) is: Where q4 is the charge of capacitor C, p3 is the inductor flux, Then the first differential of the state variable is: u4 and i3 are represented as: For i4, there are: For u3, there are Among them, u3, u4, u5, u7 are the voltages of the third, fourth, fifth, and seventh keys respectively, i1, i3, i4, i5, i7 are the currents of the first, third, fourth, fifth, and seventh keys respectively, Uin is the input voltage of the BOOST circuit; R, C, L are the equivalent load of the circuit, the output filter capacitor and the boost inductor respectively; sw is the drive signal of the switch S; The state equation of the system is obtained as follows: Where A and B are coefficient matrices, and R is the equivalent load of the circuit.

6. The modeling and control method of the current continuous combined chopper switch according to claim 1, characterized in that: The step (4) specifically comprises the following steps in order: (4a) Determination of output equation and cost function The output equation is: Then the cost function J is set to: Where, Ts is the calculation period; u4 and u7 are the voltages of the fourth and seventh keys respectively, C is the output filter capacitor, and q4 is the charge of capacitor C; (4b) Model predictive control based on state equation, output equation and cost function: Sample u4 and the current i3 of the third key, calculate q4 and p3, and predict the state variables when sw is 0 and 1 respectively according to the following formula: Where p3 is the inductor flux, R and L are the equivalent load and boost inductance of the circuit respectively; Uin is the input voltage of the BOOST circuit; sw is the drive signal of the switch S; x(t) is the state variable, and u(t) is the input variable; Thus, the predicted value of q4 is calculated and substituted into the following formula: Take the sw corresponding to the minimum J to realize the control of the BOOST circuit.

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