State Trajectory Control and Finite State Machine Implementation Method for Four-Switch Buck-Boost Converter

Abstract

The present invention proposes a four-switch Buck-Boost converter state trajectory control and finite state machine implementation method, which is characterized by comprising: the drain of the first switch tube s1 is connected to the converter input voltage V in The positive electrode, the source of the first switch tube s1 is connected to the drain of the second switch tube s2 and one end of the energy storage inductor L, and the source of the second switch tube s2 is connected to the input voltage V in The cathode of the four-switch Buck-Boost converter is connected to the source of the fourth switch S4, the cathode of the output capacitor C, and one end of the load R. The drain of the third switch is connected to the other end of the output capacitor and the other end of the load R. The source of the third switch is connected to the drain of the fourth switch S4 and the other end of the energy storage inductor L. This invention establishes a state plane for a four-switch Buck-Boost converter and derives its natural trajectory. Using a state trajectory control method, it optimizes the converter's fast dynamic response, significantly improving both the dynamic and steady-state performance of the output voltage.

Description

Technical Field

[0001] The present invention relates to the field of automation control, and in particular to a four-switch Buck-Boost converter state trajectory control and finite state machine implementation method. Background Art

[0002] Converting battery voltage to the DC voltage required by the load is essential in various power-related fields. To ensure stable power supply to devices across a wide range of battery voltage variations, thereby extending battery life and service life, four-switch Buck-Boost converters have become a research hotspot in areas such as renewable energy power generation systems, new energy vehicles, distributed power generation systems, and portable electronic devices. Furthermore, to meet the high-performance requirements of practical applications, in-depth research on four-switch Buck-Boost converter (FSBB) control technology is crucial.

[0003] For four-switch Buck-Boost converters, current control strategies mainly include single-mode control strategy and multi-mode control strategy. However, both single-mode control strategy and multi-mode control strategy have shortcomings:

[0004] (1) During the dynamic adjustment process of the single-mode control strategy, the converter's switching period and duty cycle cannot be flexibly adjusted, resulting in a long dynamic adjustment process. Furthermore, the single-mode control strategy uses a time-triggered approach to control the dynamic adjustment process, resulting in frequent switching operations, which also results in a long converter adjustment time.

[0005] (2) In multi-mode control strategies, the dynamic performance of four-switch Buck-Boost converters has rarely been studied, and the improvement of the converter's dynamic performance is limited. In addition, designing controllers for different modes in a multi-mode control strategy will greatly increase the design burden, and accurate mode detection is required to achieve switching between modes. If a unified controller is used for different modes, current research often uses model predictive control methods, which will lead to a heavy system computational burden. Summary of the Invention

[0006] The present invention aims to at least solve the technical problems existing in the prior art, and in particular innovatively proposes a four-switch Buck-Boost converter state trajectory control and finite state machine implementation method.

[0007] In order to achieve the above-mentioned object of the present invention, the present invention provides a four-switch Buck-Boost converter state trajectory control and finite state machine implementation method, the four-switch Buck-Boost converter includes four switch tubes: the drain of the first switch tube s1 is connected to the converter input voltage V inThe positive electrode of the first switch tube s1 is connected to the drain of the second switch tube s2 and one end of the inductor L, and the source of the second switch tube s2 is connected to the input voltage V in The negative electrode of the output capacitor C, the source of the fourth switch tube s4, one end of the capacitor C and one end of the load R, the drain of the third switch tube s3 is connected to the other end of the output capacitor C and the other end of the load R, and the source of the third switch tube s3 is connected to the drain of the fourth switch tube s4 and the other end of the inductor L;

[0008] The four-switch Buck-Boost converter state trajectory control and finite state machine implementation method includes the following steps:

[0009] When the input voltage V in , reference voltage v ref When one of the resistance values ​​of the load R or any combination thereof changes, the four-switch Buck-Boost converter will first perform a dynamic regulation process and then a steady-state regulation process, ultimately keeping the four-switch Buck-Boost converter in a steady state.

[0010] In the dynamic and steady-state regulation process, eight state drives of the four-switch Buck-Boost converter are involved, including:

[0011] Initial State: indicates the initialization state;

[0012] D-left 1: Mode 1: indicates the left half plane dynamic adjustment state 1;

[0013] D-left 2: Mode 2: indicates the left half plane dynamic adjustment state 2;

[0014] D-left 3: Mode 3: indicates the left half plane dynamic adjustment state three;

[0015] D-right / Steady 1: Mode 3: Indicates steady-state regulation state 1 or right half-plane dynamic regulation state 1;

[0016] D-right / Steady 2: Mode 4: Indicates steady-state regulation state 2 or right half-plane dynamic regulation state 2;

[0017] D-right / Steady 3: Mode 1: Indicates steady-state regulation state 3 or right half-plane dynamic regulation state 3;

[0018] Steady 4: Mode 2: Indicates steady-state regulation state four;

[0019] The left half plane refers to the normalized state plane vout -i L * Left half plane, that is, the output voltage is less than the reference voltage v out <v ref When; the right half plane refers to the normalized state plane v out -i L *Right half plane, that is, the output voltage is greater than the reference voltage v out >v ref hour;

[0020] State 1 refers to the state of Mode 1, State 2 refers to the state of Mode 2, State 3 refers to the state of Mode 3, and State 4 refers to the state of Mode 4.

[0021] The suffixes Mode 1, Mode 2, Mode 3, and Mode 4 of the eight state drives above represent the modes of the switch states of the four-switch Buck-Boost converter during each state drive process. The state trajectory design of the dynamic regulation process and the steady-state regulation process of the four-switch Buck-Boost converter is completed through the combination of the eight state drives above. During the state trajectory control process, the dynamic regulation process is performed first, and then the steady-state regulation process is performed, so that the four-switch Buck-Boost converter is kept in the steady state. When the input voltage V in Or reference voltage v ref Or when the resistance of the load R changes, the four-switch Buck-Boost converter will enter the dynamic regulation process again, and finally enter the steady-state regulation process to enter a new steady state.

[0022] Mode 1, Mode 2, Mode 3, and Mode 4, the switching states of the four-switch Buck-Boost converter equivalent circuit corresponding to these four modes are:

[0023] In mode 1, switches s1 and s4 are turned on, and switches s2 and s3 are turned off.

[0024] In Mode 2, switches s1 and s3 are turned on, and switches s2 and s4 are turned off.

[0025] In Mode 3, switches s2 and s3 are turned on, and switches s1 and s4 are turned off.

[0026] In mode 4, switches s2 and s4 are turned on, and switches s1 and s3 are turned off.

[0027] The dynamic adjustment is left-half-plane dynamic adjustment or right-half-plane dynamic adjustment;

[0028] The state trajectory of the left half plane dynamic adjustment is: out <v ref During the dynamic adjustment process, the left half plane dynamic adjustment state D-left 1:Mode 1 is used as the first activated state after the initialization state Initial State. Then the state trajectory is first driven in the order of D-left 1:Mode 1→D-left 2:Mode 2→D-left 3:Mode 3, and then driven in a loop according to D-left 1:Mode 1→D-left 3:Mode 3 until it enters the steady-state adjustment process through D-left 3:Mode3→D-right / Steady 1:Mode 3;

[0029] The state trajectory of the right half plane dynamic adjustment is: out >v ref During the dynamic adjustment process, the right half-plane dynamic adjustment state D-right / Steady 1:Mode 3 is used as the first activated state after the initialization state Initial State, and then the state trajectory is driven in the order of D-right / Steady 1:Mode 3→D-right / Steady 2:Mode4→D-right / Steady 3:Mode 1 until it enters the steady-state adjustment process through D-right / Steady 3:Mode 1→Steady 4:Mode 2.

[0030] The state trajectory of the steady-state regulation process is:

[0031] When the state trajectory of the left half plane dynamic adjustment enters the steady-state adjustment process from the dynamic adjustment process, the state trajectory of the steady-state adjustment process is driven in a cycle of D-right / Steady 1:Mode 3→D-right / Steady 2:Mode4→D-right / Steady 3:Mode 1→Steady 4:Mode 2;

[0032] When the state trajectory of the right half plane dynamic adjustment enters the steady-state adjustment process from the dynamic adjustment process, the state trajectory of the steady-state adjustment process is driven cyclically according to Steady 4: Mode 2 → D-right / Steady 1: Mode 3 → D-right / Steady2 → Mode 4D-right / Steady 3: Mode 1.

[0033] Preferably, the mode switching condition during the dynamic regulation of the four-switch Buck-Boost converter is:

[0034] The switching conditions from the left-half-plane dynamic adjustment state 1 D-left 1: Mode 1 to the left-half-plane dynamic adjustment state 2 D-left2: Mode 2 are as follows:

[0035] (v out -V in ) 2 +(i L *-i o *) 2 ≥r m2D 2 (18)

[0036] Among them, v out represents the output voltage of the four-switch Buck-Boost converter;

[0037] V in represents the input voltage of the four-switch Buck-Boost converter;

[0038] i L *Represents the normalized inductor current of the four-switch Buck-Boost converter;

[0039] i o *Represents the normalized output current of the four-switch Buck-Boost converter;

[0040] r m2D Indicates the radius of the Mode 2 state trajectory during the mode switching process of the left half plane switch;

[0041] The switching conditions from the left-half-plane dynamic adjustment state 2 D-left 2: Mode 2 to the left-half-plane dynamic adjustment state 3 D-left3: Mode 3 are as follows:

[0042] v out 2 +(i L *-i o *) 2 ≥r m3ref 2 +β (21)

[0043] Among them, β represents the compensation parameter;

[0044] r m3ref is the reference point (v ref ,i Lref *) The radius of Mode 3;

[0045] The compensation parameter β is described as:

[0046] β=r m3ref 2 -r m1initial2 (19)

[0047] where r m3ref 2 and r m1initial 2 Respectively expressed as:

[0048]

[0049] Among them, v outm10 and i Lm10 * respectively represent the normalized state plane v out -i L * Output voltage and normalized inductor current when the left half plane state trajectory enters Mode 1;

[0050] v ref Indicates the reference voltage;

[0051] i Lref *Represents the standardized reference current value of the four-switch Buck-Boost converter;

[0052] The switching conditions from the left-half-plane dynamic adjustment state 3 D-left 3: Mode 3 to the left-half-plane dynamic adjustment state 1 D-left1: Mode 1 are:

[0053] i L *≤i Lref * (twenty two)

[0054] Among them, i L * represents the normalized inductor current of the four-switch Buck-Boost converter;

[0055] i Lref *Represents the standardized reference current value of the four-switch Buck-Boost converter;

[0056] The switching condition from the left half plane dynamic adjustment state 1 D-left 1: Mode 1 to the left half plane dynamic adjustment state 3 D-left3: Mode 3 is the same as formula (21);

[0057] The switching conditions from right-half-plane dynamic adjustment state 1 D-right / Steady 1: Mode 3 to right-half-plane dynamic adjustment state 2 D-right / Steady 2: Mode 4 are as follows:

[0058] i L *≤i LK * (twenty four)

[0059] Among them, i L*Represents the normalized inductor current of the four-switch Buck-Boost converter;

[0060] i LK *Represents the normalized switching inductor current of the four-switch Buck-Boost converter;

[0061] The switching conditions from right-half-plane dynamic adjustment state 2 D-right / Steady 2: Mode 4 to right-half-plane dynamic adjustment state 3 D-right / Steady 3: Mode 1 are as follows:

[0062]

[0063] Among them, i Lref *Represents the normalized inductor current reference value of the four-switch Buck-Boost converter;

[0064] v ref Represents the tracking reference voltage of the four-switch Buck-Boost converter;

[0065] v out represents the output voltage of the four-switch Buck-Boost converter;

[0066] v in represents the input voltage of the four-switch Buck-Boost converter;

[0067] i o *Indicates the normalized output current of a four-switch Buck-Boost converter.

[0068] Preferably, the mode switching condition during the steady-state regulation of the four-switch Buck-Boost converter is:

[0069] The switching conditions from steady-state regulation state 1 D-right / Steady 1: Mode 3 to steady-state regulation state 2 D-right / Steady2: Mode 4 are:

[0070] i L *≤i LK * (twenty four)

[0071] Among them, i L *Represents the normalized inductor current of the four-switch Buck-Boost converter;

[0072] i LK *Represents the normalized switching inductor current of the four-switch Buck-Boost converter;

[0073] The switching conditions from steady-state adjustment state 2 D-right / Steady 2: Mode 4 to steady-state adjustment state 3 D-right / Steady3: Mode 1 are:

[0074]

[0075] Among them, i Lref *Represents the normalized inductor current reference value of the four-switch Buck-Boost converter;

[0076] v ref Represents the tracking reference voltage of the four-switch Buck-Boost converter;

[0077] v out represents the output voltage of the four-switch Buck-Boost converter;

[0078] v in represents the input voltage of the four-switch Buck-Boost converter;

[0079] i o *Represents the normalized output current of the four-switch Buck-Boost converter;

[0080] The state trajectory switching condition from steady-state regulation state three D-right / Steady 3: Mode 1 to steady-state regulation state four Steady 4: Mode 2 is expressed as:

[0081] (v out -V in ) 2 +(i L *-i o *) 2 ≥r m2ref 2 +δr 2 (28)

[0082] Among them, v out represents the output voltage of the four-switch Buck-Boost converter;

[0083] r m2ref Indicates the reference point (v ref ,i Lref *) The radius of Mode 2;

[0084] i L *Represents the normalized inductor current of the four-switch Buck-Boost converter;

[0085] i o *Represents the normalized output current of the four-switch Buck-Boost converter;

[0086] δr 2 represents the hysteresis parameter, which is used to limit the switching frequency and form a steady-state limit cycle;

[0087] During the steady-state regulation process, the state trajectory switching condition from the steady-state regulation state 4 Steady 4: Mode 2 to the steady-state regulation state 1 D-right / Steady 1: Mode 3 is expressed as:

[0088] v out 2 +(i L *-i o *) 2 ≥r m3ref 2 +δr 2 (30)

[0089] Among them, r m3ref Indicates the reference point (v ref ,i Lref *) is the radius of Mode 3.

[0090] Preferably, the four-switch Buck-Boost converter state trajectory control and finite state machine implementation method further includes:

[0091] S1, establish a dynamic mathematical model of the four-switch Buck-Boost converter in four modes, the four modes are Mode 1, Mode 2, Mode 3 and Mode 4; and use the output voltage v out The horizontal axis is the standardized inductor current i L * Establish a normalized state plane v for the vertical axis out -i L *; The natural trajectory of the converter in the standardized state plane is derived based on the dynamic mathematical model of the four modes;

[0092] S2, analyzing the natural trajectory of the converter in the standardized state plane, designing the state trajectory of the dynamic and steady-state regulation processes; then deriving the switching conditions of the modes during the dynamic and steady-state regulation processes of the four-switch Buck-Boost converter;

[0093] S3, these switching conditions are applied to the finite state machine controller of the four-switch Buck-Boost converter. The switching conditions can realize the mode conversion, that is, control the on and off of each switch tube, thereby realizing the control of the four-switch Buck-Boost converter. The design of the switching conditions can achieve precise adjustment of the converter output voltage, so that its output voltage v out Closely tracks the reference voltage v ref, and at the same time achieve the purpose of reducing the steady-state output voltage ripple and inductor current ripple.

[0094] Preferably, the S1 comprises the following steps:

[0095] S1-1, according to Kirchhoff's law, the dynamic mathematical models of the equivalent circuits of the four-switch Buck-Boost converter in Mode 1, Mode 2, Mode 3, and Mode 4 are as follows:

[0096] Mode 1:

[0097]

[0098] Mode 2:

[0099]

[0100] Mode 3:

[0101]

[0102] Mode 4:

[0103]

[0104] Wherein, L represents the inductance of the inductor L;

[0105] i L represents the inductor current;

[0106] represents the first-order derivative of the inductance of the inductor L with respect to time, and “·” represents the first-order derivative with respect to time;

[0107] V in represents the input voltage of the four-switch Buck-Boost converter;

[0108] C represents the capacitance of capacitor C;

[0109] represents the first-order derivative of the output voltage of the four-switch Buck-Boost converter with respect to time;

[0110] v out represents the output voltage of the four-switch Buck-Boost converter;

[0111] R represents the resistance value of resistor R;

[0112] S1-2, with output voltage v out is the horizontal coordinate axis, the standardized inductor current i L*Establish a normalized state plane v for the vertical axis out -i L *, where the normalized inductor current i L * means:

[0113]

[0114] S1-3, based on the dynamic mathematical model of the equivalent circuit of the four-switch Buck-Boost converter Mode 1 Mode 1, Mode 2 Mode 2, Mode 3 Mode 3, Mode 4 Mode 4, derive Mode 1 Mode 1, Mode 2 Mode 2, Mode 3 Mode 3, Mode 4 on the standardized state plane v out -i L *Natural trajectory on the

[0115] Mode 1 is in the normalized state plane v out -i L The process of obtaining the natural trajectory on * is:

[0116] According to the mathematical model (1), the normalized inductor current i L * and output voltage v out The relationship is expressed as:

[0117]

[0118] At each step, the inductor current i L and the output voltage v out During sampling, considering the fast sampling rate, the inductor current i L and the output voltage v out They all change within a very small range, so formula (6) can be expressed as:

[0119]

[0120] Among them, Δi L * represents the change of the standardized inductor current iL* in each sampling interval;

[0121] Δv out Indicates the change in output voltage vout at each sampling interval;

[0122] Therefore, Mode 1 is on the normalized state plane v out -i L The natural trajectory on * is expressed as:

[0123]

[0124] Among them, i L0 *Indicates the initial value of the normalized inductor current;

[0125] v out0 Indicates the initial value of the output voltage;

[0126] i o0 *Indicates the initial value of the standardized output current;

[0127] From formula (8), we know that in the normalized state plane v out -i L In Figure 1, the natural trajectory of the four-switch Buck-Boost converter mode 1 is represented by a straight line with a negative slope, the slope of which is determined by the converter input voltage V in and the initial value i of the standardized output current when entering Mode 1 o0 * Joint decision making;

[0128] Mode 2 Mode 2 in the normalized state plane v out -i L The process of obtaining the natural trajectory on * is:

[0129] According to the mathematical model (2), the inductor current i can be obtained L The second derivative of is:

[0130]

[0131] Where “··” represents the second-order derivative with respect to time;

[0132] By transforming Equation (9) and combining it with mathematical model (2), we obtain the following dynamic equations:

[0133]

[0134] Perform equivalent transformation on equation (10) and calculate the inductor current i L Integrate to get Mode 2 on the normalized state plane v out -i L The natural trajectory on * is:

[0135] (v out -V in ) 2 +(i L *-i o *) 2 =r m2 2 (11)

[0136] Among them, i o *Indicates the standardized output current, r m2 is in the normalized state plane v out -i L*The initial position of the four-switch Buck-Boost converter when entering Mode 2 is at the reference point (v ref ,i Lref *) distance;

[0137] From formula (11), we know that in the normalized state plane v out -i L * In the four-switch Buck-Boost converter mode 2, the natural trajectory is (V in ,i o *) is a cluster of circular trajectories with the center of the circle;

[0138] Mode 3 Mode 3 in the normalized state plane v out -i L The process of obtaining the natural trajectory on * is:

[0139] According to mathematical model (3), formula (9) is transformed to obtain the following dynamic equations:

[0140]

[0141] in, Inductor current i L Second derivative with respect to time;

[0142] Inductor current i L First derivative with respect to time;

[0143] Perform equivalent transformation on equation (12) and calculate the inductor current i L Integrate to get Mode 3 on the normalized state plane v out -i L The natural trajectory on * is:

[0144]

[0145] Among them, r m3 is in the normalized state plane v out -i L *The initial position of the four-switch Buck-Boost converter when entering Mode 2 Mode 3 is the reference point (v ref ,i Lref *) distance;

[0146] From formula (13), we know that in the normalized state plane v out -i L *, the natural trajectory of Mode 3 is (0,i o *) is a cluster of circular trajectories with the center of the circle;

[0147] Mode 4 Mode 4 in the normalized state plane v out -i L The process of obtaining the natural trajectory on * is:

[0148] According to mathematical model (4), the time domain model of inductor current and output voltage is obtained:

[0149]

[0150] Where c is a constant, i.e., the inductor current iL of the four-switch Buck-Boost converter in Mode 4.

[0151] v out0 Indicates the initial value of the output voltage;

[0152] e is a natural constant;

[0153] t represents time;

[0154] From formula (14), we can get mode 4 on the normalized state plane v out -i L The natural trajectory on * is:

[0155]

[0156] From formula (15), we know that in the normalized state plane v out -i L *, the natural trajectory of Mode 4 is parallel to the normalized state plane v out -i L * Cluster of lines on the horizontal axis.

[0157] The above equations (8), (11), (13), and (15) are respectively the four-switch Buck-Boost converter mode 1, mode 2, mode 3, and mode 4 on the normalized state plane v out -i L *Natural trajectory on the skin.

[0158] Preferably, by analyzing the natural trajectory of the converter in the standardized state plane, it is known that the state trajectory control process of the four-switch Buck-Boost converter will go through dynamic and steady-state adjustment processes, and in the dynamic and steady-state adjustment processes, eight state drives of the four-switch Buck-Boost converter are involved.

[0159] Preferably, the mode switching condition during the dynamic regulation of the four-switch Buck-Boost converter is obtained by:

[0160] First, solve the dynamic mathematical equations of Mode 1 in Equation (1) and Mode 3 in Equation (3) respectively, and set the standardized reference inductor current i Lref *for:

[0161]

[0162] Among them, v ref Represents the tracking reference voltage of the four-switch Buck-Boost converter;

[0163] i o *Represents the normalized output current of the four-switch Buck-Boost converter;

[0164] v in represents the input voltage of the four-switch Buck-Boost converter;

[0165] The normalized state plane v out -i L *The reference point is expressed as (v ref ,i Lref *), the reference point is the target point that needs to be reached by the state trajectory control method;

[0166] The dynamic regulation process is divided into the standardized state plane v out -i L * Left half plane (i.e. output voltage is less than reference voltage v out <v ref Switching conditions of the switching mode) and the standardized state plane v out -i L *Right half plane (ie the output voltage is greater than the reference voltage v out >v ref There are two cases:

[0167] Normalized state plane v out -i L *The switching conditions of the left half plane switching mode are derived as follows:

[0168] Set the radius r of Mode 2 during the left half plane switching process m2D for:

[0169] r m2D =r m2min +m(r m2max -r m2min ) (17)

[0170] in, m is a constant between 0 and 1, and the constant m is used to represent Mode 2 in the normalized state plane v out-i L * The degree of participation in the left half plane switching mode switching process. The closer m is to 0, the greater the degree of participation of Mode 2. The closer m is to 1, the smaller the degree of participation of Mode 2.

[0171] The switching conditions from the left-half-plane dynamic adjustment state 1 D-left 1: Mode 1 to the left-half-plane dynamic adjustment state 2 D-left2: Mode 2 are as follows:

[0172] (v out -V in ) 2 +(i L *-i o *) 2 ≥r m2D 2 (18)

[0173] Among them, v out represents the output voltage of the four-switch Buck-Boost converter;

[0174] V in represents the input voltage of the four-switch Buck-Boost converter;

[0175] i L represents the inductor current of the four-switch Buck-Boost converter;

[0176] i o *Represents the normalized output current of the four-switch Buck-Boost converter;

[0177] r m2D Indicates the radius of the Mode 2 state trajectory during the mode switching process of the left half plane switch;

[0178] Considering the power loss in the four-switch Buck-Boost converter, which is mainly caused by the existence of parasitic parameters such as capacitor equivalent series resistance, inductor DC resistance and switch on-resistance, when the converter operates in Mode 2 and Mode 3, the natural trajectory decreases faster than in the ideal state, resulting in the normalized state plane v out -i L *The state trajectory in the dynamic adjustment process of the left half plane cannot directly reach the reference point through Mode 3; therefore, in the standardized state plane v out -i L * The compensation parameter β is introduced in the left half plane, thereby delaying the switch of other modes to Mode 3, and the compensation parameter β is updated in Mode 3. The updated compensation parameter β when the state trajectory is in the left plane is described as:

[0179] β=r m3ref 2 -r m1initial 2 (19)

[0180] where r m3ref is the reference point (v ref ,i Lref *) The radius of Mode 3, r m3ref 2 and r m1initial 2 Respectively expressed as:

[0181]

[0182] Among them, v outm10 and i Lm10 * respectively represent the normalized state plane v out -i L * Output voltage and normalized inductor current when the left half plane state trajectory enters Mode 1;

[0183] The switching conditions from the left-half-plane dynamic adjustment state 2 D-left 2: Mode 2 to the left-half-plane dynamic adjustment state 3 D-left3: Mode 3 are as follows:

[0184] v out 2 +(i L *-i o *) 2 ≥r m3ref 2 +β (21)

[0185] The existence of parasitic parameters makes it impossible for the state trajectory to reach the reference point (v) in one go after the state trajectory is driven sequentially from D-left 1: Mode 1 → D-left 2: Mode 2 → D-left 3: Mode 3. ref ,i Lref *); when moving along the state trajectory of Mode 3, the output voltage v out <v ref , and the normalized inductor current i L *=i Lref *, the four-switch Buck-Boost converter needs to operate in mode 1 again. After that, it is driven in a cycle from D-left 1: Mode 1 to D-left 3: Mode 3. The switching condition from the left-half-plane dynamic adjustment state 3 D-left 3: Mode 3 to the left-half-plane dynamic adjustment state 1 D-left1: Mode 1 is as follows:

[0186] iL *≤i Lref * (twenty two)

[0187] Among them, i L * represents the normalized inductor current of the four-switch Buck-Boost converter;

[0188] i Lref *Represents the standardized reference current value of the four-switch Buck-Boost converter;

[0189] The switching condition from the left half plane dynamic adjustment state 1 D-left 1: Mode 1 to the left half plane dynamic adjustment state 3 D-left3: Mode 3 is the same as formula (21);

[0190] S2-2, normalized state plane v out -i L *The switching conditions of the right half plane switching mode are derived as follows:

[0191] Set the normalized switching inductor current i LK *for:

[0192] i LK *=i Lref * / K (23)

[0193] Where K is a gain parameter greater than 1, which is used to set the modal four trajectories and i L *=i Lref * The distance between the horizontal lines, the larger K is, the closer the modal four trajectories are to i L *=i Lref *The larger the distance between the horizontal lines, the smaller K is. The modal four trajectories and i L *=i Lref *The smaller the distance between the horizontal lines;

[0194] The switching conditions from right-half-plane dynamic adjustment state 1 D-right / Steady 1: Mode 3 to right-half-plane dynamic adjustment state 2 D-right / Steady 2: Mode 4 are as follows:

[0195] i L *≤i LK * (twenty four)

[0196] Among them, i L *Represents the normalized inductor current of the four-switch Buck-Boost converter;

[0197] i LK *Represents the normalized switching inductor current of the four-switch Buck-Boost converter;

[0198] The switching conditions from right-half-plane dynamic adjustment state 2 D-right / Steady 2: Mode 4 to right-half-plane dynamic adjustment state 3 D-right / Steady 3: Mode 1 are as follows:

[0199]

[0200] Among them, i Lref *Represents the normalized inductor current reference value of the four-switch Buck-Boost converter;

[0201] v ref Represents the tracking reference voltage of the four-switch Buck-Boost converter;

[0202] v out represents the output voltage of the four-switch Buck-Boost converter;

[0203] v in represents the input voltage of the four-switch Buck-Boost converter;

[0204] i o *Indicates the normalized output current of a four-switch Buck-Boost converter.

[0205] In summary, due to the adoption of the above-mentioned technical solution, the state trajectory control method of the four-switch Buck-Boost converter designed in the present invention plans the motion trajectory of the converter in the state plane and adopts an event-triggered control method, so that the output voltage and inductor current in the dynamic process change according to the designed state trajectory, achieving rapid dynamic response, ensuring rapid overshoot-free startup of the output voltage, eliminating the inductor current impact when the reference voltage drops stepwise, and ensuring that the output voltage has a shorter adjustment time when the load changes stepwise; and achieving lower steady-state output voltage ripple and inductor current ripple. At the same time, the output voltage remains stable when the input voltage changes rapidly, making the converter more adaptable. The specific advantages are as follows:

[0206] 1. Compared to model predictive control methods, this invention plans the converter's motion trajectory on the state plane and adopts an event-triggered control approach. This allows the output voltage and inductor current to change according to the designed state trajectory during the dynamic process, thus reducing the design burden.

[0207] 2. Compared with traditional control strategies, the present invention can achieve a fast dynamic response of the output voltage of the four-switch Buck-Boost converter, ensure a fast startup of the output voltage without overshoot, eliminate the inductor current surge when the reference voltage drops stepwise, and ensure that the output voltage has a short regulation time when the load changes stepwise;

[0208] 3. Multi-mode control: Designing multiple controllers for multiple modes requires precise mode detection to determine which controller to use. However, the state trajectory control of the present invention requires only a single controller, eliminating the need for controller switching. Furthermore, compared to model predictive control methods that use a single controller for multiple modes, the control algorithm required for the state trajectory control of the present invention is more complex.

[0209] 4. Achieve lower steady-state output voltage ripple and inductor current ripple through steady-state control strategy design;

[0210] 5. The present invention can ensure that the output voltage remains stable when the input voltage changes rapidly, making the converter more adaptable.

[0211] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by consideration of the present invention.

[0212] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0213] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0214] Figure 1 Schematic diagram of the four-switch Buck-Boost converter of the present invention.

[0215] Figure 2 1 is a circuit diagram of four modes of the four-switch Buck-Boost converter of the present invention.

[0216] Figure 3 It is a finite state machine controller of the novel state trajectory control method of the present invention.

[0217] Figure 4 The converter in the present invention is in the standardized state plane v out -i L *The state trajectory of the dynamic adjustment process.

[0218] Figure 5 The converter in the present invention is in the standardized state plane v out -i L *State trajectory of the steady-state regulation process.

[0219] Figure 6 The converter in the present invention is in the standardized state plane v out -i L *v out <vref State trajectory motion diagram when .

[0220] Figure 7 The converter in the present invention is in the standardized state plane v out -i L *v out >v ref State trajectory motion diagram when .

[0221] Figure 8 are the standardized inductor current ripple and output voltage ripple of the converter in the present invention. DETAILED DESCRIPTION

[0222] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0223] Figure 1 The circuit structure of the four-switch Buck-Boost converter of the present invention includes four switch tubes. The drain of the first switch tube s1 is connected to the converter input voltage V in The positive electrode of the first switch tube s1 is connected to the drain of the second switch tube s2 and one end of the inductor L, and the source of the second switch tube s2 is connected to the input voltage V in The negative electrode of the output capacitor C, the source of the fourth switch tube s4, one end of the capacitor C and one end of the load R, the drain of the third switch tube s3 is connected to the other end of the output capacitor C and the other end of the load R, and the source of the third switch tube s3 is connected to the drain of the fourth switch tube s4 and the other end of the inductor L. Figure 1 The positive direction of the inductor current is specified in , and the value is positive if it is in the same direction as the specified current, and negative if it is opposite to the specified current direction.

[0224] Figure 2 This is a circuit diagram of the four modes of the four-switch Buck-Boost converter of the present invention, where the solid line indicates conduction and the dashed line indicates shutdown. The four-switch Buck-Boost converter has four modes: Mode 1, Mode 2, Mode 3, and Mode 4. In Mode 1, switches s1 and s4 are on, and switches s2 and s3 are off; in Mode 2, switches s1 and s3 are on, and switches s2 and s4 are off; in Mode 3, switches s2 and s3 are on, and switches s1 and s4 are off; in Mode 4, switches s2 and s4 are on, and switches s1 and s3 are off.

[0225] According to Kirchhoff's law, the dynamic mathematical models of the equivalent circuits of the four-switch Buck-Boost converter in Mode 1, Mode 2, Mode 3, and Mode 4 are as follows:

[0226] Mode 1:

[0227]

[0228] Mode 2:

[0229]

[0230] Mode 3:

[0231]

[0232] Mode 4:

[0233]

[0234] With output voltage v out is the horizontal coordinate axis, the standardized inductor current i L *Establish a normalized state plane v for the vertical axis out -i L *, where the normalized inductor current i L * means:

[0235]

[0236] According to formulas (1), (2), (3), and (4), Mode 1, Mode 2, Mode 3, and Mode 4 are derived on the standardized state plane v out -i L *, we get the natural trajectories of the four modes:

[0237] Mode 1 is in the normalized state plane v out -i L The natural trajectory on * is expressed as:

[0238]

[0239] From formula (8), we know that in the normalized state plane v out -i L In Figure 1, the natural trajectory of the four-switch Buck-Boost converter mode 1 is represented by a straight line with a negative slope, the slope of which is determined by the converter input voltage V in and the initial value i of the standardized output current when entering Mode 1o0 * Joint decision making;

[0240] Mode 2 Mode 2 in the normalized state plane v out -i L *Natural trajectory on:

[0241] (v out -V in ) 2 +(i L *-i o *) 2 =r m2 2 (11)

[0242] From formula (11), we know that in the normalized state plane v out -i L * In the four-switch Buck-Boost converter mode 2, the natural trajectory is (V in ,i o *) is a cluster of circular trajectories with the center of the circle;

[0243] Mode 3 Mode 3 in the normalized state plane v out -i L *Natural trajectory on:

[0244] v out 2 +(i L *-i o *) 2 =r m3 2 (13)

[0245] From formula (13), we know that in the normalized state plane v out -i L *, the natural trajectory of Mode 3 is (0,i o *) is a cluster of circular trajectories with the center of the circle;

[0246] Mode 4 Mode 4 in the normalized state plane v out -i L *Natural trajectory on:

[0247]

[0248] From formula (15), we know that in the normalized state plane v out -i L *, the natural trajectory of Mode 4 is parallel to the normalized state plane v out -i L * Cluster of lines on the horizontal axis;

[0249] Figure 3 It is a finite state machine controller of the novel state trajectory control method of the present invention: the state trajectory control process of the four-switch Buck-Boost converter includes eight state drives, namely the initialization state Initial State, the left half-plane dynamic adjustment state one D-left 1: Mode 1, the left half-plane dynamic adjustment state two D-left 2: Mode 2, the left half-plane dynamic adjustment state three D-left 3: Mode 3, the steady-state adjustment and right half-plane dynamic adjustment state one D-right / Steady1: Mode 3, the steady-state adjustment and right half-plane dynamic adjustment state two D-right / Steady 2: Mode 4, the steady-state adjustment and right half-plane dynamic adjustment state three D-right / Steady 3: Mode 1, and the steady-state adjustment state four Steady 4: Mode 2.

[0250] During the dynamic adjustment process, according to the converter output voltage v out and reference voltage v ref The size relationship of the state trajectory control is divided into v out <v ref and v out >v ref Two control processes. out <v ref During the control process, the left half plane dynamic adjustment state D-left 1: Mode 1 is used as the first activated state after the initialization state Initial State. Then the state trajectory is first driven in the order of D-left 1: Mode 1 → D-left 2: Mode 2 → D-left 3: Mode 3, and then it is driven in a loop according to D-left 1: Mode 1 → D-left 3: Mode 3. out >v ref During the control process, the right half-plane dynamic adjustment state D-right / Steady 1:Mode 3 is used as the first activated state after the initialization state Initial State, and then the state trajectory is driven in the order of D-right / Steady 1:Mode 3→D-right / Steady 2:Mode4→D-right / Steady3:Mode 1.

[0251] The natural trajectory of the four modes of the converter is analyzed by equations (8), (11), (13), and (15). By designing the state trajectory of the dynamic and steady-state regulation processes, the switching conditions of the switching modes in the dynamic regulation process of the four-switch Buck-Boost converter and the switching conditions of the switching modes in the steady-state regulation process of the four-switch Buck-Boost converter are derived:

[0252] The switching conditions of the switching mode during the dynamic regulation of the four-switch Buck-Boost converter include:

[0253] Normalized state plane v out -i L * Left half plane, that is, the output voltage is less than the reference voltage v out <v ref Switching conditions and normalized state plane v of the switching mode out -i L *Right half plane, that is, the output voltage is greater than the reference voltage v out >v ref The switching condition of the switch mode.

[0254] Solve the dynamic mathematical equations of Mode 1 in Equation (1) and Mode 3 in Equation (3) respectively, and set the standardized reference inductor current i Lref *for:

[0255]

[0256] The normalized state plane v out -i L *The reference point is expressed as (v ref ,i Lref *), the reference point is the target point that needs to be reached by the state trajectory control method.

[0257] Normalized state plane v out -i L *The switching conditions of the left half plane switching mode are as follows:

[0258] The switching conditions from the left-half-plane dynamic adjustment state 1 D-left 1: Mode 1 to the left-half-plane dynamic adjustment state 2 D-left2: Mode 2 are as follows:

[0259] (v out -V in ) 2 +(i L *-i o *) 2 ≥r m2D 2 (18)

[0260] Considering the power loss in the four-switch Buck-Boost converter, which is mainly caused by the existence of parasitic parameters such as capacitor equivalent series resistance, inductor DC resistance and switch on-resistance, when the converter operates in Mode 2 and Mode 3, the natural trajectory decreases faster than in the ideal state, resulting in the normalized state plane v out -i L *The state trajectory in the dynamic adjustment process of the left half plane cannot directly reach the reference point through Mode 3; therefore, in the standardized state plane v out -i L * The compensation parameter β is introduced in the left half plane, thereby delaying the switch of other modes to Mode 3, and the compensation parameter β is updated in Mode 3. The updated compensation parameter β when the state trajectory is in the left plane is described as:

[0261] β=r m3ref 2 -r m1initial 2 (19)

[0262] The switching conditions from the left-half-plane dynamic adjustment state 2 D-left 2: Mode 2 to the left-half-plane dynamic adjustment state 3 D-left3: Mode 3 are as follows:

[0263] v out 2 +(i L *-i o *) 2 ≥r m3ref 2 +β (21)

[0264] The existence of parasitic parameters makes it impossible for the state trajectory to reach the reference point (v) in one go after the state trajectory is driven sequentially from D-left 1: Mode 1 → D-left 2: Mode 2 → D-left 3: Mode 3. ref ,i Lref *); when moving along the state trajectory of Mode 3, the output voltage v out <v ref , and the normalized inductor current i L *=i Lref *, the four-switch Buck-Boost converter needs to operate in mode 1 again. After that, it is driven in a cycle from D-left 1: Mode 1 to D-left 3: Mode 3. The switching condition from the left-half-plane dynamic adjustment state 3 D-left 3: Mode 3 to the left-half-plane dynamic adjustment state 1 D-left1: Mode 1 is as follows:

[0265] iL *≤i Lref * (twenty two)

[0266] The switching condition from the left half plane dynamic adjustment state 1 D-left 1: Mode 1 to the left half plane dynamic adjustment state 3 D-left3: Mode 3 is the same as formula (21);

[0267] Normalized state plane v out -i L *The switching conditions of the right half plane switching mode are as follows:

[0268] Set the normalized switching inductor current i LK *for:

[0269] i LK *=i Lref * / K (23)

[0270] The switching conditions from right-half-plane dynamic adjustment state 1 D-right / Steady 1: Mode 3 to right-half-plane dynamic adjustment state 2 D-right / Steady 2: Mode 4 are as follows:

[0271] i L *≤i LK * (twenty four)

[0272] The switching conditions from right-half-plane dynamic adjustment state 2 D-right / Steady 2: Mode 4 to right-half-plane dynamic adjustment state 3 D-right / Steady 3: Mode 1 are as follows:

[0273]

[0274] The switching conditions of the switching mode during the steady-state regulation of the four-switch Buck-Boost converter include:

[0275] During the steady-state regulation process, the switching condition from the steady-state regulation state 1 D-right / Steady 1: Mode 3 to the steady-state regulation state 2 D-right / Steady 2: Mode 4 is the same as formula (24);

[0276] During the steady-state regulation process, the switching condition from the steady-state regulation state 2 D-right / Steady 2: Mode 4 to the steady-state regulation state 3 D-right / Steady 3: Mode 1 is the same as formula (25);

[0277] The hysteresis parameter δr is introduced in Mode 2 and Mode 3 of the steady-state regulation process. 2 , to limit the switching frequency and form a steady-state limit cycle;

[0278] The natural trajectory of Mode 2 during steady-state regulation is defined as:

[0279] (v out -V in ) 2 +(i L *-i o *) 2 =r m2ref 2 +δr 2 (26)

[0280] During the steady-state regulation process, the state trajectory switching condition from the steady-state regulation state three D-right / Steady 3: Mode 1 to the steady-state regulation state four Steady 4: Mode 2 is expressed as:

[0281] (v out -V in ) 2 +(i L *-i o *) 2 ≥r m2ref 2 +δr 2 (28)

[0282] The natural trajectory of Mode 3 during steady-state regulation is defined as:

[0283] v out 2 +(i L *-i o *) 2 =r m3ref 2 +δr 2 (29)

[0284] During the steady-state regulation process, the state trajectory switching condition from the steady-state regulation state 4 Steady 4: Mode 2 to the steady-state regulation state 1 D-right / Steady 1: Mode 3 is expressed as:

[0285] v out 2 +(i L *-i o *) 2 ≥r m3ref 2 +δr 2 (30)

[0286] Combining the above switching conditional equations (18), (21), (22), (24), (25), (28), and (30) with the eight states of the finite state machine controller of the four-switch Buck-Boost converter: Initial State, left half-plane dynamic adjustment state 1 D-left 1: Mode 1, left half-plane dynamic adjustment state 2 D-left 2: Mode 2, left half-plane dynamic adjustment state 3 D-left 3: Mode 3, steady-state adjustment and right half-plane dynamic adjustment state 1 D-right / Steady 1: Mode 3, steady-state adjustment and right half-plane dynamic adjustment state 2 D-right / Steady 2: Mode 4, steady-state adjustment and right half-plane dynamic adjustment state 3 D-right / Steady 3: Mode 1, steady-state adjustment state 4 Steady 4: Mode 2, the following is constructed. Figure 3 The finite state machine controller of the state trajectory control method is shown.

[0287] Combining the above switching conditions (18), (21), (22), (24), (25), (28), (30) and the four modes of the four-switch Buck-Boost converter on the standardized state plane v out -i L The natural trajectory formulas (8), (11), (13), and (15) on * are as follows: Figure 4 The converter shown is in the normalized state plane v out -i L *The state trajectory of the dynamic adjustment process.

[0288] Combining the above switching conditions (24), (25), (28), (30) and the four modes of the four-switch Buck-Boost converter on the standardized state plane v out -i L The natural trajectory formulas (8), (11), (13), and (15) on * are as follows: Figure 5 The converter shown is in the normalized state plane v out -i L *The state trajectory of the steady-state regulation process. It should be noted that the natural trajectory shape of Mode 2 is similar to the input voltage V in related, Figure 5 (a) indicates v ref <V in situation; Figure 5 (b) indicates v ref =V in situation; Figure 5 (c) represents v ref >V in situation.

[0289] The four-switch Buck-Boost converter circuit parameters involved are adjusted at the input voltage V in =9V, reference voltage v ref =15V, output capacitor C = 100μF, negative energy storage inductor L = 100μH, load R = 10Ω, hysteresis parameter δr 2 =0.04, gain parameter K=1.05, m=0.1, we get Figure 6 Shown in the normalized state plane v out -i L *v out <v ref The state trajectory of the output voltage and inductor current during the converter startup process. The output voltage v out After stabilizing at 15V, reduce the reference voltage v ref to 9V to get Figure 7 Shown in the normalized state plane v out -i L *v out >v ref The state trajectory of the converter's output voltage and inductor current. Figure 7 The steady-state limit cycle formed in the converter is the normalized state plane v out -i L *State trajectory of the steady-state regulation process. Figure 8 It is the standardized inductor current ripple and output voltage ripple formed by state trajectory control in the four-switch Buck-Boost converter circuit. Figure 8 (a) indicates v ref <V in situation; Figure 8 (b) indicates v ref =V in situation; Figure 8 (c) represents v ref >V in situation.

[0290] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A four-switch Buck-Boost converter state trajectory control and finite state machine implementation method, the four-switch Buck-Boost converter includes four switches: the drain of the first switch s1 is connected to the converter input voltage v in The positive electrode of the first switch tube s1 is connected to the drain of the second switch tube s2 and one end of the inductor L, and the source of the second switch tube s2 is connected to the input voltage v in The negative electrode of the output capacitor C, the source of the fourth switch tube s4, one end of the capacitor C and one end of the load R, the drain of the third switch tube s3 is connected to the other end of the output capacitor C and the other end of the load R, and the source of the third switch tube s3 is connected to the drain of the fourth switch tube s4 and the other end of the inductor L; It is characterized in that The four-switch Buck-Boost converter state trajectory control and finite state machine implementation method includes the following steps: When the input voltage v in , reference voltage v ref When one of the resistance values ​​of the load R or any combination thereof changes, the four-switch Buck-Boost converter will first perform a dynamic regulation process and then a steady-state regulation process, ultimately keeping the four-switch Buck-Boost converter in a steady state. In the dynamic and steady-state regulation process, eight state drives of the four-switch Buck-Boost converter are involved, including: Initial State: indicates the initialization state; D-left 1: Mode 1: indicates the left half plane dynamic adjustment state 1; D-left 2: Mode 2: indicates the left half plane dynamic adjustment state 2; D-left 3: Mode 3: indicates the left half plane dynamic adjustment state three; D-right / Steady 1: Mode 3: Indicates steady-state regulation state 1 or right half-plane dynamic regulation state 1; D-right / Steady 2: Mode 4: Indicates steady-state regulation state 2 or right half-plane dynamic regulation state 2; D-right / Steady 3: Mode 1: Indicates steady-state regulation state 3 or right half-plane dynamic regulation state 3; Steady 4: Mode 2: Indicates steady-state regulation state four; The left half plane refers to the output voltage being less than the reference voltage v out <v ref When the right half plane is when the output voltage is greater than the reference voltage v out >v ref hour; State 1 refers to the state of Mode 1, State 2 refers to the state of Mode 2, State 3 refers to the state of Mode 3, and State 4 refers to the state of Mode 4. Mode 1, Mode 2, Mode 3, and Mode 4, the switching states of the four-switch Buck-Boost converter equivalent circuit corresponding to these four modes are: In Mode 1, switches s1 and s4 are turned on, and switches s2 and s3 are turned off. In Mode 2, switches s1 and s3 are turned on, and switches s2 and s4 are turned off. In Mode 3, switches s2 and s3 are turned on, and switches s1 and s4 are turned off. In mode 4, switches s2 and s4 are turned on, and switches s1 and s3 are turned off. The dynamic adjustment is left-half-plane dynamic adjustment or right-half-plane dynamic adjustment; The state trajectory of the left half plane dynamic adjustment is: out <v ref During the dynamic adjustment process, the left half plane dynamic adjustment state D-left 1:Mode 1 is used as the first activated state after the initialization state Initial State, and then the state trajectory is first driven in the order of D-left 1:Mode 1→D-left 2:Mode 2→D-left 3:Mode 3, and then driven in a loop according to D-left 1:Mode 1→D-left 3:Mode 3; The state trajectory of the right half plane dynamic adjustment is: out >v ref During the dynamic adjustment process, the right half plane dynamic adjustment state D-right / Steady 1:Mode 3 is used as the first activated state after the initialization state Initial State, and then the state trajectory is driven in the order of D-right / Steady 1:Mode 3→D-right / Steady 2:Mode4→D-right / Steady3:Mode 1; The state trajectory of the steady-state regulation process is: When the state trajectory of the left half plane dynamic adjustment enters the steady-state adjustment process from the dynamic adjustment process, the state trajectory of the steady-state adjustment process is driven in a cycle of D-right / Steady 1:Mode 3→D-right / Steady 2:Mode4→D-right / Steady3:Mode 1→Steady 4:Mode 2; When the state trajectory of the right half plane dynamic adjustment enters the steady-state adjustment process from the dynamic adjustment process, the state trajectory of the steady-state adjustment process is driven cyclically according to Steady 4: Mode 2 → D-right / Steady 1: Mode 3 → D-right / Steady 2: Mode 4 → D-right / Steady 3: Mode 1.

2. The four-switch Buck-Boost converter state trajectory control and finite state machine implementation method according to claim 1, characterized in that: The mode switching conditions during the dynamic regulation of the four-switch Buck-Boost converter are: The switching conditions from the left-half-plane dynamic adjustment state 1 D-left 1: Mode 1 to the left-half-plane dynamic adjustment state 2 D-left 2: Mode 2 are as follows: (v out -v in ) 2 +(i L *-i o *) 2 ≥r m2D 2 (18) Among them, v out represents the output voltage of the four-switch Buck-Boost converter; v in represents the input voltage of the four-switch Buck-Boost converter; i L *Represents the normalized inductor current of the four-switch Buck-Boost converter; r m2D Indicates the radius of the Mode 2 state trajectory during the mode switching process of the left half plane switch; i o *Represents the normalized output current of a four-switch Buck-Boost converter; The switching conditions from the left-half-plane dynamic adjustment state 2 D-left 2: Mode 2 to the left-half-plane dynamic adjustment state 3 D-left 3: Mode 3 are as follows: v out 2 +(i L *-i o *) 2 ≥r m3ref 2 +β (21) Among them, β represents the compensation parameter; r m3ref is the reference point (v ref ,i Lref *) The radius of Mode 3; The compensation parameter β is described as: β＝r m3ref 2 -r m1initial 2 (19) where r m3ref 2 and r m1initial 2 Respectively expressed as: Among them, v outm10 and i Lm10 * respectively represent the normalized state plane v out -i L * Output voltage and normalized inductor current when the left half plane state trajectory enters Mode 1; v ref Represents the tracking reference voltage of the four-switch Buck-Boost converter; i Lref *Represents the standardized reference current value of the four-switch Buck-Boost converter; The switching conditions from the left-half-plane dynamic adjustment state 3 D-left 3: Mode 3 to the left-half-plane dynamic adjustment state 1 D-left 1: Mode 1 are: i L *≤i Lref * (22) Among them, i L *Represents the normalized inductor current of the four-switch Buck-Boost converter; The switching condition from the left half plane dynamic adjustment state 1 D-left 1: Mode 1 to the left half plane dynamic adjustment state 3 D-left 3: Mode 3 is the same as formula (21); The switching conditions from right-half-plane dynamic adjustment state 1 D-right / Steady 1: Mode 3 to right-half-plane dynamic adjustment state 2 D-right / Steady 2: Mode 4 are as follows: i L *≤i LK * (24) Among them, i LK *Represents the normalized switching inductor current of the four-switch Buck-Boost converter; The switching conditions from right-half-plane dynamic adjustment state 2 D-right / Steady 2: Mode 4 to right-half-plane dynamic adjustment state 3 D-right / Steady 3: Mode 1 are as follows:

3. The four-switch Buck-Boost converter state trajectory control and finite state machine implementation method according to claim 1, characterized in that: The mode switching conditions during the steady-state regulation of the four-switch Buck-Boost converter are: The switching conditions from steady-state adjustment state 1 D-right / Steady 1: Mode 3 to steady-state adjustment state 2 D-right / Steady 2: Mode 4 are: i L *≤i LK * (24) Among them, i L *Represents the normalized inductor current of the four-switch Buck-Boost converter; i LK *Represents the normalized switching inductor current of the four-switch Buck-Boost converter; The switching conditions from steady-state adjustment state 2 D-right / Steady 2: Mode 4 to steady-state adjustment state 3 D-right / Steady 3: Mode 1 are: Among them, i Lref *Represents the normalized inductor current reference value of the four-switch Buck-Boost converter; v ref Represents the tracking reference voltage of the four-switch Buck-Boost converter; v out represents the output voltage of the four-switch Buck-Boost converter; v in represents the input voltage of the four-switch Buck-Boost converter; i o *Represents the normalized output current of a four-switch Buck-Boost converter; The state trajectory switching condition from steady-state regulation state three D-right / Steady 3: Mode 1 to steady-state regulation state four Steady 4: Mode 2 is expressed as: (in out -in in ) 2 +(i L *-and o *) 2 ≥r m2ref 2 +δr 2 (28) Among them, r m2ref Indicates the reference point (v ref ,i Lref *) The radius of Mode 2; δr 2 represents the hysteresis parameter; During the steady-state regulation process, the state trajectory switching condition from the steady-state regulation state 4 Steady 4: Mode 2 to the steady-state regulation state 1 D-right / Steady 1: Mode 3 is expressed as: in out 2 +(i L *-and o *) 2 ≥r m3ref 2 +δr 2 (30) Among them, r m3ref Indicates the reference point (v ref ,i Lref *) is the radius of Mode 3.

4. The four-switch Buck-Boost converter state trajectory control and finite state machine implementation method according to claim 1, characterized in that: The state trajectory control and finite state machine implementation method of the four-switch Buck-Boost converter also includes: S1, establish a dynamic mathematical model of the four-switch Buck-Boost converter in four modes, the four modes are Mode 1, Mode 2, Mode 3 and Mode 4; and use the output voltage v out The horizontal axis is the standardized inductor current i L * Establish a normalized state plane v for the vertical axis out -i L *; The natural trajectory of the converter in the standardized state plane is derived based on the dynamic mathematical model of the four modes; S2, analyzing the natural trajectory of the converter in the standardized state plane, designing the state trajectory of the dynamic and steady-state regulation processes; then deriving the switching conditions of the modes during the dynamic and steady-state regulation processes of the four-switch Buck-Boost converter; S3, these switching conditions are applied to the finite state machine controller of the four-switch Buck-Boost converter. The switching conditions can realize mode conversion, that is, control the on and off of each switch tube, thereby realizing the control of the four-switch Buck-Boost converter.

5. The method for state trajectory control and finite state machine implementation of a four-switch Buck-Boost converter according to claim 4, characterized in that: Said S1 comprises the following steps: S1-1, according to Kirchhoff's law, the dynamic mathematical models of the equivalent circuits of the four-switch Buck-Boost converter in Mode 1, Mode 2, Mode 3, and Mode 4 are as follows: Mode 1: Mode 2: Mode 3: Mode 4: Wherein, L represents the inductance of the inductor L; i L represents the inductor current; It represents the first-order derivative of the inductance of the inductor L with respect to time; V in represents the input voltage of the four-switch Buck-Boost converter; C represents the capacitance of capacitor C; represents the first-order derivative of the output voltage of the four-switch Buck-Boost converter with respect to time; v out represents the output voltage of the four-switch Buck-Boost converter; R represents the resistance value of resistor R; S1-2, with output voltage v out is the horizontal coordinate axis, the standardized inductor current i L *Establish a normalized state plane v for the vertical axis out -i L *, where the normalized inductor current i L * means: S1-3, based on the dynamic mathematical model of the equivalent circuit of the four-switch Buck-Boost converter Mode 1 Mode 1, Mode 2 Mode 2, Mode 3 Mode 3, Mode 4, derive Mode 1 Mode 1, Mode 2 Mode 2, Mode 3 Mode 3, Mode 4 on the standardized state plane v out -i L *Natural trajectory on the Mode 1 is in the normalized state plane v out -i L The natural trajectory on * is expressed as: Among them, i L0 *Indicates the initial value of the normalized inductor current; v out0 Indicates the initial value of the output voltage; i o0 *Indicates the initial value of the standardized output current; Mode 2 Mode 2 in the normalized state plane v out -i L The natural trajectory on * is: (v out -V in ) 2 +(i L *-i o *) 2 =r m2 2 (11) Among them, i o *Indicates the standardized output current, r m2 is in the normalized state plane v out -i L *The initial position of the four-switch Buck-Boost converter when entering Mode 2 is at the reference point (v ref ,i Lref *) distance; From formula (11), we know that in the normalized state plane v out -i L * In the four-switch Buck-Boost converter mode 2, the natural trajectory is (V in ,i o *) is a cluster of circular trajectories with the center of the circle; Mode 3 Mode 3 in the normalized state plane v out -i L The natural trajectory on * is: v out 2 +(i L *-i o *) 2 =r m3 2 (13) Among them, r m3 is in the normalized state plane v out -i L *The initial position of the four-switch Buck-Boost converter when entering Mode 2 Mode 3 is the reference point (v ref ,i Lref *) distance; Mode 4 Mode 4 in the normalized state plane v out -i L The natural trajectory on * is: From formula (15), we know that in the normalized state plane v out -i L *, the natural trajectory of Mode 4 is parallel to the normalized state plane v out -i L * Cluster of lines on the horizontal axis.

6. The method for state trajectory control and finite state machine implementation of a four-switch Buck-Boost converter according to claim 4, wherein: By analyzing the natural trajectory of the converter in the standardized state plane, it is found that the state trajectory control process of the four-switch Buck-Boost converter will go through dynamic and steady-state adjustment processes. In the dynamic and steady-state adjustment processes, eight state drives of the four-switch Buck-Boost converter are involved.

7. The method for state trajectory control and finite state machine implementation of a four-switch Buck-Boost converter according to claim 4, wherein: The switching conditions of the modes during the dynamic regulation of the four-switch Buck-Boost converter are obtained as follows: First, solve the dynamic mathematical equations of Mode 1 and Mode 3 respectively, and set the standardized reference inductor current i Lref *for: Among them, v ref Represents the tracking reference voltage of the four-switch Buck-Boost converter; The normalized state plane v out -i L *The reference point is expressed as (v ref ,i Lref *), the reference point is the target point that needs to be reached by the state trajectory control method; The dynamic regulation process is divided into the standardized state plane v out -i L * Left half plane and normalized state plane v out -i L *Two cases in the right half plane; Normalized state plane v out -i L *The switching conditions of the left half plane switching mode are derived as follows: Set the radius r of Mode 2 during the left half plane switching process m2D for: r m2D ＝r m2min +m(r m2max -r m2min ) (17) in, m is a constant from 0 to 1, and the constant m is used to represent Mode 2 in the normalized state plane v out -i L *Degree of participation in the left half plane switching mode switching process; The switching conditions from the left-half-plane dynamic adjustment state 1 D-left 1: Mode 1 to the left-half-plane dynamic adjustment state 2 D-left 2: Mode 2 are as follows: (v out -v in ) 2 +(i L *-i o *) 2 ≥r m2D 2 (18) Among them, v out represents the output voltage of the four-switch Buck-Boost converter; v in represents the input voltage of the four-switch Buck-Boost converter; i L represents the inductor current of the four-switch Buck-Boost converter; i o *Represents the normalized output current of a four-switch Buck-Boost converter; r m2D Indicates the radius of the Mode 2 state trajectory during the mode switching process of the left half plane switch; When the converter operates in Mode 2 and Mode 3, the normalized state plane v out -i L *The state trajectory in the dynamic adjustment process of the left half plane cannot directly reach the reference point through Mode 3; therefore, in the standardized state plane v out -i L * The compensation parameter β is introduced in the left half plane, thereby delaying the switch of other modes to Mode 3, and the compensation parameter β is updated in Mode 3. The updated compensation parameter β when the state trajectory is in the left plane is described as: β＝r m3ref 2 -r m1initial 2 (19) where r m3ref is the reference point (v ref ,i Lref *) The radius of Mode 3, r m3ref 2 and r m1initial 2 Respectively expressed as: Among them, v outm10 and i Lm10 * respectively represent the normalized state plane v out -i L * Output voltage and normalized inductor current when the left half plane state trajectory enters Mode 1; The switching conditions from the left-half-plane dynamic adjustment state 2 D-left 2: Mode 2 to the left-half-plane dynamic adjustment state 3 D-left 3: Mode 3 are as follows: v out 2 +(i L *-i o *) 2 ≥r m3ref 2 +β (21) The existence of parasitic parameters makes the state trajectory unable to reach the reference point (v) in one go after the state trajectory is driven sequentially from D-left 1: Mode 1 → D-left 2: Mode 2 → D-left 3: Mode 3. ref ,i Lref *); when moving along the state trajectory of Mode 3, the output voltage v out <v ref , and the normalized inductor current i L *=i Lref *, the four-switch Buck-Boost converter needs to operate in mode 1 again. After that, it is driven in a cycle from D-left 1: Mode 1 to D-left 3: Mode 3. The switching condition from the left-half-plane dynamic adjustment state 3 D-left 3: Mode 3 to the left-half-plane dynamic adjustment state 1 D-left1: Mode 1 is as follows: i L *≤i Lref * (22) Among them, i L *Represents the normalized inductor current of the four-switch Buck-Boost converter; The switching condition from the left half plane dynamic adjustment state 1 D-left 1: Mode 1 to the left half plane dynamic adjustment state 3 D-left 3: Mode 3 is the same as formula (21); S2-2, normalized state plane v out -i L *The switching conditions of the right half plane switching mode are derived as follows: Set the normalized switching inductor current i LK *for: i LK *=i Lref * / K (23) Where K is a gain parameter greater than 1, which is used to set the modal four trajectories and i L *=i Lref * The distance between the horizontal lines, the larger K is, the closer the modal four trajectories are to i L *=i Lref *The larger the distance between the horizontal lines, the smaller K is. The modal four trajectories and i L *=i Lref *The smaller the distance between the horizontal lines; The switching conditions from right-half-plane dynamic adjustment state 1 D-right / Steady 1: Mode 3 to right-half-plane dynamic adjustment state 2 D-right / Steady 2: Mode 4 are as follows: i L *≤i LK * (24) Among them, i LK *Represents the normalized switching inductor current of the four-switch Buck-Boost converter; The switching conditions from right-half-plane dynamic adjustment state 2 D-right / Steady 2: Mode 4 to right-half-plane dynamic adjustment state 3 D-right / Steady 3: Mode 1 are as follows:

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