CN114337249A - Three-port DC-DC converter based on quasi-Z source and switch capacitor and competition control method - Google Patents

Abstract

The invention discloses a three-port DC-DC converter based on a quasi-Z source and a switched capacitor and a competition control method. The converter adopts competition control to realize automatic switching of modes, can be flexibly matched with an upper-layer energy management and distribution system, and belongs to power electronic conversion device field. On the basis of the boost circuit, the converter combines a switched capacitor unit composed of a switch tube, a diode and a capacitor, and a charge and discharge unit composed of a switch tube, a diode and an inductance. By controlling the on and off of the three switch tubes, changing the The connection mode of the capacitor and the inductor in the circuit and the on-off condition of the diode can achieve the effect of improving the voltage gain and charging and discharging the second input source. The voltage gain of the present invention is higher, and the duty cycle D is within 0 to 0.5, which can avoid the limit duty cycle situation, and at the same time, the switched capacitor structure can reduce the voltage stress of the switching device, and is suitable for new energy sources such as fuel cells and photovoltaic cells. Hybrid power generation system.

Description

Three-Port DC-DC Converter Based on Quasi-Z Source and Switched Capacitor and Competitive Control Method

technical field

The invention belongs to the field of power electronic converters, and in particular relates to a three-port DC-DC converter based on a quasi-Z source and a switched capacitor and a competition control method.

Background technique

With the development of economy, the problems of energy shortage and environmental pollution are becoming more and more serious. At present, my country's solar and wind power generation technologies are mature and commercialized, but due to uneven distribution and high climate requirements, it is difficult to achieve large-scale popularization and utilization, and the development is gradually weak. Due to its advantages of high efficiency, zero pollution, and renewability, hydrogen energy has attracted the attention of all countries in the world and has become a hot spot in new energy research and application. Proton exchange membrane fuel cell is a new type of power generation device that directly converts hydrogen energy into electrical energy. The reaction process only generates water and heat. It has the advantages of high efficiency, no pollution and high reliability. It is widely used in new energy vehicles, distributed Power generation and other fields have great application prospects, so the PEMFC hybrid power supply system has become a research hotspot.

The output voltage of PEMFC has a very large variation range, and only boosting or bucking can not meet the needs of practical applications. Therefore, it is very important to select and design a suitable DC-DC converter. The existing PEMFC hybrid power supply system topology is mainly divided into two categories, one is to use a discrete power conversion unit to realize the energy transfer between each port, the other is to use an integrated multi-port DC-DC converter to realize the energy transfer between each port. The transfer of energy between ports. Multiport DC-DC converters can be classified into non-isolated, partially isolated and fully isolated types. The ports of the fully isolated and partially isolated converters are electrically isolated by transformers, the direct current is inverted into high-frequency alternating current, and the energy transmission between the ports is realized through magnetic coupling. Usually, there are many switching devices and the converter is relatively large. And the problem of complex control strategy.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a three-port DC-DC converter based on a quasi-Z source and a switched capacitor

The technical solution to achieve the purpose of the present invention is: a three-port DC-DC converter based on a quasi-Z source and a switched capacitor, characterized in that it includes a first input source V _pe , a second input source V _b , a first inductance L ₁ , second inductance L ₂ , third inductance L ₃ , shunt diode D ₀ , first diode D ₁ , second diode D ₂ , third diode D ₃ , fourth diode D _4. The fifth diode D ₅ , the sixth diode D ₆ , the seventh diode D ₇ , the first power switch tube S ₁ , the second power switch tube S ₂ , the third power switch tube S ₃ , a first capacitor C ₁ , a second capacitor C ₂ , a third capacitor C ₃ , a fourth capacitor C ₄ , a fifth capacitor C ₅ , and a load R; wherein, the anode of the first input source V _pe is connected to the first diode D The anode of ₁ , the cathode of the first input source _Vpe is connected to the cathode of the second input source _Vb , the cathode of the _first diode D1 is connected to the source of the _second power switch tube S2, and the _second power switch tube S2 The drain of the first inductor L1 is connected to the positive electrode of the second input source _Vb , _one end of the first inductor L1 is connected to the source electrode of the _second power switch tube S2, and the other end of the _first inductor L1 is connected to the _second diode D2 and the shunt The anode of the diode _D0 is connected to the cathode of the _second capacitor C2 at the same time, the cathode of the _second diode D2 is connected to the anode of the first capacitor _C1 and one end of the _second inductor L2, and the _first power switch tube S1 The drain, the cathode of the shunt diode D ₀ and the anode of the second capacitor C ₂ are connected to the other end of the second inductor L ₂ , one end of the third inductor L ₃ is connected to the drain of the second power switch tube S ₂ , and the third inductor L The other end of ₃ is connected to the cathode of the third diode _D3 and the source of the _third power switch tube S3, the anode of the third diode _D3 is connected to the cathode of the second input source _Vb , and the third power switch tube _The drain of S3 is connected to the cathode of the _seventh diode D7, the anode of the _seventh diode D7 is connected to the drain of the _first power switch S1, the anode of the _fourth diode D4 is connected to the third capacitor _The cathode of C3 is connected to the drain of the _first power switch tube S1, the cathode of the _fourth diode D4 is connected to the anode of the _fifth diode D5, the cathode of the fourth capacitor _C4 and the cathode of the fifth capacitor _C5 The anode, the anode of the _third capacitor C3 and the cathode of the _fifth diode D5 are connected to the anode of the _sixth diode D6, and the cathode of the _sixth diode D6 is connected to the anode of the fourth capacitor _C4 and the load R one end of the fifth capacitor C ₅ and the other end of the load R are connected to the source of the first power switch tube S ₁ ; the first inductor L ₁ , the second inductor L ₂ , the first capacitor C ₁ , the second The capacitor C ₂ , the second diode D ₂ , the shunt diode D ₀ and the first power switch S ₁ form a quasi-Z source structure, and then the fourth diode D ₄ , the fifth diode D ₅ , the first power switch S 1 The six diodes D ₆ , the third capacitor C ₃ , the fourth capacitor C ₄ and the fifth capacitor C ₅ form a switched capacitor unit for boosting, and the third inductor L ₃ , the third diode D ₃ , the seventh diode D ₇ and the third power switch tube S ₃ form a second input source V _b charging loop with continuous output current.

Compared with the prior art, the present invention has the following significant advantages:

(1) The present invention changes the connection mode of the inductor and capacitor in the circuit and the on-off condition of the diode by controlling the on and off of the three switching tubes, thereby achieving the effect of improving the voltage gain and charging and discharging.

(2) The present invention realizes the energy flow of two power sources and one load through an integrated three-port DC-DC converter, thereby reducing the number of components used and the cost.

(3) The duty cycle range of the power switch tube of the present invention is between 0 and 0.5, which avoids the limit duty cycle situation.

(4) The present invention adopts competition control to eliminate the negative influence of parameters set by human experience in rule control.

Description of drawings

FIG. 1 is a circuit diagram of a three-port DC-DC converter based on a quasi-Z source and a switched capacitor according to the present invention.

FIG. 2 is an equivalent circuit diagram of the three-port DC-DC converter based on a quasi-Z source and a switched capacitor in a single-input single-output mode in different modes according to the present invention. FIG. 2(a) is an equivalent circuit diagram in which the _first power switch S1 is turned on and other power switches are turned off, and FIG. 2(b) is an equivalent circuit diagram in which all power switches are turned off.

FIG. 3 is an equivalent circuit diagram of a three-port DC-DC converter based on a quasi-Z source and a switched capacitor in different modes of single-input and double-output modes of the present invention. Figure 3(a) is an equivalent circuit diagram in which the _first power switch S1 is turned on and other power switches are turned off, and Figure 3(b) is the _third power switch S3 turned on and other power switches are turned off Figure 3(c) is an equivalent circuit diagram of the _first power switch S1 and the _third power switch S3 being turned off.

FIG. 4 is an equivalent circuit diagram of a three-port DC-DC converter in a dual-input single-output mode in different modes based on a quasi-Z source and a switched capacitor according to the present invention. FIG. 4(a) is an equivalent circuit diagram in which the _first power switch S1 and the _second power switch S2 are turned on, and the _third power switch S3 is turned off, and FIG. 4(b) is the second power switch S ₂ is turned on, and the equivalent circuit diagram of other power switch tubes is turned off. FIG. 4(c) is an equivalent circuit diagram of all power switch tubes turned off.

Fig. 5 is the main waveform diagram of the three-port DC-DC converter based on the quasi-Z source and switched capacitor of the present invention under three operating modes. Among them, Fig. 5(a) is a waveform diagram of working in single-input single-output mode; Fig. 5(b) is a waveform diagram of working in single-input dual-output mode; Fig. 5(c) is a waveform diagram of working in dual-input single-output mode Waveform diagram.

FIG. 6 is a schematic diagram of the competition control strategy of the present invention.

Detailed ways

The solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 1 , a three-port DC-DC converter based on a quasi-Z source and a switched capacitor includes a first input source V _pe , a second input source V _b , a first inductance L ₁ , and a second inductance L ₂ , a third inductor L ₃ , a shunt diode D ₀ , a first diode D ₁ , a second diode D ₂ , a third diode D ₃ , a fourth diode D ₄ , and a fifth diode D _5. The sixth diode D ₆ , the seventh diode D ₇ , the first power switch S ₁ , the second power switch S ₂ , the third power switch S ₃ , the first capacitor C ₁ , the second capacitor C ₂ , third capacitor C ₃ , fourth capacitor C ₄ , fifth capacitor C ₅ , load R; wherein, the anode of the first input source V _pe is connected to the anode of the first diode D ₁ , and the first input source The cathode of _Vpe is connected to the cathode of the second input source _Vb , the cathode of the _first diode D1 is connected to the source of the _second power switch S2, and the drain of the _second power switch S2 is connected to the second input source The anode of _Vb , _one end of the first inductor L1 is connected to the source of the _second power switch tube S2, the other end of the _first inductor L1 is connected to the anode of the _second diode D2 and the shunt diode _D0 , and is connected to the anode of the shunt diode D0 at the same time. The cathode of the _second capacitor C2, the cathode of the _second diode D2 is connected to the anode of the first capacitor _C1 and one end of the _second inductor L2, the drain of the _first power switch tube S1, the drain of the shunt diode _D0 The negative electrode and the positive electrode of the _second capacitor C2 are connected to the other end of the _second inductor L2, one end of the _third inductor L3 is connected to the drain of the _second power switch tube S2, and one end of the _third inductor L3 is connected to the third diode The cathode of the tube _D3 is connected to the source of the _third power switch tube S3, the anode of the third diode _D3 is connected to the negative pole of the second input source _Vb , and the drain of the _third power switch tube S3 is connected to the seventh and second The cathode of the diode _D7 , the anode of the _seventh diode D7 is connected to the drain of the _first power switch tube S1, the anode of the _fourth diode D4 and the cathode of the _third capacitor C3 are connected to the first power switch _The drain of the tube S1, the cathode of the _fourth diode D4 is connected to the anode of the _fifth diode D5, the cathode of the fourth capacitor _C4 and the anode of the fifth capacitor _C5 , and the anode of the _third capacitor C3 and the cathode of the _fifth diode D5 is connected to the anode of the _sixth diode D6, the cathode of the _sixth diode D6 is connected to the anode of the fourth capacitor _C4 and one end of the load R, and the cathode of the fifth capacitor _C5 The other end of the negative electrode and the load R is connected to the source of the first power switch tube S ₁ ; the first inductor L ₁ , the second inductor L ₂ , the first capacitor C ₁ , the second capacitor C ₂ , the second diode D ₂ , the shunt diode D ₀ and the first power switch tube S ₁ form a quasi-Z source structure, and then the fourth diode D ₄ , the fifth diode D ₅ , the sixth diode D ₆ , and the third capacitor C _3. The fourth capacitor C ₄ and the fifth capacitor C ₅ form the capacitor unit of the switch to boost the voltage, which is composed of the third inductor L ₃ , the third diode D ₃ , and the seventh diode D ₇ and the third power switch tube S ₃ to form a second input source V _b charging loop with continuous output current. PEMFC hybrid power supply system controller. In the single-input single-output mode, the first input source _Vpe or the second input source _Vb supplies power to the load through the quasi-Z source structure and the switched capacitor unit; in the dual-input single-output mode, the first input source _Vpe and The second input source V _b is combined to supply power, and also supplies power to the load through the quasi-Z source structure and the switched capacitor boosting unit; in the single-input dual-output mode, the first input source V _pe supplies power to the load, and at the same time passes through the quasi-Z source structure. The cascaded Buck structure charges the second input source V _b . There are two reasons for the cascaded Buck structure: one is that in the single-input dual-output mode, the first capacitor C ₁ , the second capacitor C ₂ and the second Influenced by the relationship between the input source V _b , when charging the second input source V _b , an inductor unit must be added to avoid output voltage clamping; the second is that the Buck structure including the inductor unit has the advantage of constant output current while reducing the voltage, just meet the charging requirements.

According to the number of input and output ports, the invention can be divided into three working modes: single input single output, double input single output and single input double output. Assume that the voltage across the first input source V _pe is V _pe , the voltage across the second input source V _b is V _b , the voltage across the load R is V _o , the current of the first inductor L ₁ is I _L1 , and the second inductor The current of L ₂ is I _L2 , the current of the third inductor L ₃ is I _L3 , the voltage across the first capacitor C ₁ is V _C1 , the voltage across the second capacitor C ₂ is V _C2 , and the voltage across the third capacitor C ₃ is V _C3 , the voltage across the fourth capacitor C ₄ is V _C4 , the voltage across the fifth capacitor is V _C5 , the duty cycle of the _{first power switch S1 is D 1 ,} and the duty of the _second power switch S2 The ratio is D ₂ , the duty cycle of the third power switch tube S ₃ is D ₃ , the equivalent series resistances of the capacitors are r, r ₁ , and the switching period is T _s . The three operating modes are introduced in detail:

The control waveform diagram of the single-input single-output mode is shown in Figure 5(a). In this mode, the converter has two operating modes. The equivalent circuit diagram in the stage t ₀ ~ t ₁ is shown in Figure 2(a). In this mode, the _first power switch tube S1 is turned on, the first input source _Vpe and the _second capacitor C2 charge the first inductor L1, and the _first capacitor _C1 charges the _second inductor L2 Charging, the fifth capacitor _C5 charges the _third capacitor C3, and at the same time, together with the fourth capacitor _C4 supplies power to the load R; the stage from _t1 to _t2 is the second mode, and the equivalent circuit diagram of this mode is shown in Figure 2 As shown in (b), the first power switch S ₁ is turned off, and the first input source V _pe is combined with the first inductor L ₁ , the second inductor L ₂ and the third capacitor C ₃ to form the first capacitor C ₁ , the second capacitor C 1 and the second capacitor C 3 . The capacitor C ₂ , the fourth capacitor C ₄ , and the fifth capacitor C ₅ are charged and supply power to the load R.

The following relations can be listed in this mode:

The output voltage is obtained by solving the equation (8)

Solving other DC quantities as shown in formula (9)

From this, the voltage stress of the power switch tube and diode device can be calculated, as shown in formula (10)

The device current stress is shown in equation (11)

The main waveform diagram of the single-input dual-output mode is shown in Figure 5(b). In one switching cycle, this mode has three operating modes. The equivalent circuit in stages t ₀ to t ₁ is shown in Figure 3(a). In the first mode, the _first power switch S1 is turned on, and the _third power switch S3 is turned off. At this time, the first input The source V _pe and the second capacitor C ₂ charge the first inductor L ₁ , the first capacitor C ₁ charges the second inductor L ₂ , the fifth capacitor C ₅ charges the third capacitor C ₃ , and the fourth capacitor C ₄ Commonly supply power to the load R, and the third inductor L ₃ charges the second input source V _b ; the equivalent circuit in stages t ₁ to t ₂ is shown in Figure 3(b), in the second mode, the first power switch tube S ₁ is turned off, and the _third power switch S3 is turned on. At this time, the first input source V _pe is combined with the first inductor L ₁ , the second inductor L ₂ and the third capacitor C ₃ to form the third inductor L ₃ , the third inductor L 3 , and the third capacitor C 3 . A capacitor C ₁ , a second capacitor C ₂ , a fourth capacitor C ₄ , and a fifth capacitor C ₅ are charged, and supply power for the second input source V _b and the load R; the equivalent circuit in stages t ₂ to t ₃ is shown in Figure 3 ( As shown in c), in the third mode, the first power switch S ₁ and the third power switch S ₃ are turned off, and the first input source V _pe is combined with the first inductor L ₁ , the second inductor L ₂ and the third power switch S 3 . The three capacitors C ₃ jointly charge the first capacitor C ₁ , the second capacitor C ₂ , the fourth capacitor C ₄ , and the fifth capacitor C ₅ , and supply power to the load R, and the third inductor L ₃ charges the second input source V _b . This model satisfies the relational formulae (1) to (11) and formulae (12) and (13):

It can be known that the expression of the output voltage V _o is the same as the formula (8). At this time, the voltage stress and current stress of the power switch tube S ₃ , diodes D ₃ and D ₇ are:

The main waveform diagram of the dual-input single-output mode is shown in Figure 5(c). In one switching cycle, this mode has three operating modes. The equivalent circuit in the stage from t ₀ to t ₁ is shown in FIG. 4( a ). In this stage, the _first power switch S1 and the _second power switch S2 are both turned on, the second input source V _b and the second capacitor C ₂ Charge the first inductor L1, the _first capacitor _C1 charges the _second inductor L2, the fifth capacitor _C5 charges the _third capacitor C3, and together with the fourth capacitor _C4 supplies power to the load R; _t1 The equivalent circuit of ~t ₂ stage is shown in Figure 4(b). In the second mode, the _first power switch S1 is turned off, the _second power switch S2 is turned on, and the second input source _Vb is combined The first inductor L ₁ , the second inductor L ₂ and the third capacitor C ₃ jointly charge the first capacitor C ₁ , the second capacitor C ₂ , the fourth capacitor C ₄ , and the fifth capacitor C ₅ , and supply power to the load R; The equivalent circuit in stages t ₂ to t ₃ is shown in Figure 4(c). In the third mode, the _first power switch S1 and the _second power switch S2 are turned off, and the first input source _Vpe is combined The first inductor L ₁ , the second inductor L ₂ and the third capacitor C ₃ jointly charge the first capacitor C ₁ , the second capacitor C ₂ , the fourth capacitor C ₄ , and the fifth capacitor C ₅ , and supply power to the load R. The relationships that can be listed in this mode are:

The output voltage can be solved as shown in equation (23)

Other DC quantities in this mode are as follows:

In this mode, the voltage stress of the power switch tube and diode is as follows:

The current stress of the power switch tube and diode is as follows:

After obtaining the variable transfer functions that need to be controlled in each of the above modes, the controller can be designed. After completion, the mode switching is realized by using the competition control. The competition control is based on the _first power switch S1 and the _third power switch S3 The duty ratio signal, the SOC of the second input source V _b and the load voltage are used as the judgment basis. The advantage of this method compared with the regular control method is that it removes the problem of inconsistent parameter drift caused by artificially set parameters and battery aging, so that at any time, the converter judges whether it needs to switch modes according to the current maximum output power of the fuel cell, thereby Avoid overloading caused by parameter drift after battery aging and other damage to the battery.

It can be seen from the analysis of the three operating modes that the present invention realizes the charging and discharging of the second input source V _b through an integrated three-port DC-DC converter, reduces the number of devices used, and reduces the cost, and at the same time, the duty cycle is 0. Between ~0.5, the limit duty cycle can be avoided, and the reliability is improved. The converter adopts competitive control, and a total of 3 PI controllers are used, that is, a BDCR (Battery discharge current controller) for controlling the discharge current of the second input source, and a BCR (Battery charge current controller) for controlling the charging current of the second input source. ) and OVR (Output voltage controller) for controlling the output voltage. The inputs of the three controllers are the discharge current ib _,dis of the second input source, the charging current ib _,cha of the second input source, and the output voltage v _o and their reference values _ib ,disref _{, ib,charef} , v _o respectively _{, the difference between ref} , the outputs of the three PI controllers are _db,dis , db _,cha and _dv respectively, where _db,cha , _dv plus the second input source SOC and the reference value SOC _ref The difference value is used as the input signal of competition control, and then the judgment condition of mode switching is obtained. _The working state _of the switch S2 or the switch S3 is determined by _db,dis and db _{,cha , db,dis} is the duty cycle _d2 of the _second power switch S2 _{, db,cha} is the third The duty ratio d ₃ of the power switch tube S ₃ , that is, the output duty ratio is d ₂ /d ₃ , the output voltage is controlled by the switch tube S ₁ , and the duty ratio d ₁ is d _v . , the final result is: in the single-input single-output mode, the _first power switch S1 works; in the single-input dual-output mode, the _first power switch S1 and the _third power switch S3 work; dual-input single-output In the mode, the _first power switch S1 and the _second power switch S2 work.

To sum up, a competitive control method for a three-port DC-DC converter based on a quasi-Z source and a switched capacitor adopts a competitive control strategy to achieve automatic switching between the various modes of the converter, as follows:

If it is currently in the single-input single-output mode, the basis for switching to the dual-input single-output mode is whether the duty cycle of the _first power switch S1 reaches the upper limit value, and the basis for switching to the single-input double-output mode is the second input source. Whether V _b state of charge (SOC) is less than the lower limit;

If it is currently in the single-input double-output mode, the basis for switching to the single-input single-output mode is whether the SOC of the second input source _Vb reaches the maximum value, and the basis for switching to the double-input single-output mode is the output of the _third power switch S3. Whether the duty cycle reaches the upper limit;

If it is currently in the dual-input single-output mode, the basis for switching to the single-input single-output mode is whether the SOC of the second input source is in a given range, and the basis for switching to the single-input dual-output mode is whether the SOC of the second input source V _b is less than lower limit.

Compared with the rule-based control strategy, the competitive control eliminates the negative impact of parameter setting based on human experience, and has stronger adaptability. Even if the output characteristics of the battery change, the competition control can normally realize the mode switching, which improves the reliability of the converter during operation.

The invention adopts a non-isolated three-port DC-DC converter combined with a quasi-Z source circuit and a switched capacitor boosting unit and a competition control method thereof. By controlling the turn-on and turn-off of the three switches, the connection mode of the inductor and capacitor in the circuit and the on-off condition of the diode are changed, so as to achieve the effect of improving the voltage gain and charging and discharging.

The present invention designs a three-port DC-DC converter based on a quasi-Z source and a switched capacitor, and designs a competitive control strategy for the converter. Compared with the traditional non-isolated DC-DC converter, the present invention has higher voltage gain, and reduce the voltage stress of the device, reducing the cost of the converter. Secondly, the Buck structure is introduced into the energy storage port, which solves the problem of output voltage clamping. In addition, the duty ratio of the converter is 0 to 0.5, and there is no limit duty ratio. The present invention sorts out the on-off state of the power switch tube and the topological power flow direction in each mode, and derives performance indicators such as the voltage gain of the converter and the voltage/current stress of the switching device in each mode. The invention designs a competitive control strategy to make the converter automatically switch modes under different load powers. This strategy is based on the duty cycle of the power switch and the SOC of the second input source. Compared with the rule-based control strategy, the competitive control eliminates the negative impact of parameter setting based on human experience. The competitive control strategy based on the duty cycle and the second input source SOC can adapt to the current state of the battery. Even if the battery output characteristics change due to battery aging or external factors, the competitive control can normally achieve mode switching.

Claims (6)

1. A three-port DC-DC converter based on a quasi-Z source and a switched capacitor, characterized in that it comprises a first input source V _pe , a second input source V _b , a first inductance L ₁ , a second inductance L ₂ , a third inductor L ₃ , a shunt diode D ₀ , a first diode D ₁ , a second diode D ₂ , a third diode D ₃ , a fourth diode D ₄ , and a fifth diode D _5. The sixth diode D ₆ , the seventh diode D ₇ , the first power switch S ₁ , the second power switch S ₂ , the third power switch S ₃ , the first capacitor C ₁ , the second capacitor C ₂ , third capacitor C ₃ , fourth capacitor C ₄ , fifth capacitor C ₅ , load R; wherein, the anode of the first input source V _pe is connected to the anode of the first diode D ₁ , and the first input source The cathode of _Vpe is connected to the cathode of the second input source _Vb , the cathode of the _first diode D1 is connected to the source of the _second power switch S2, and the drain of the _second power switch S2 is connected to the second input source The anode of _Vb , _one end of the first inductor L1 is connected to the source of the _second power switch tube S2, the other end of the _first inductor L1 is connected to the anode of the _second diode D2 and the shunt diode _D0 , and at the same time is connected to the anode of the second diode D2 and the shunt diode D0. The cathode of the _second capacitor C2, the cathode of the _second diode D2 is connected to the anode of the first capacitor _C1 and one end of the _second inductor L2, the drain of the _first power switch tube S1, the drain of the shunt diode _D0 The negative electrode and the positive electrode of the _second capacitor C2 are connected to the other end of the _second inductor L2, one end of the _third inductor L3 is connected to the drain of the _second power switch tube S2, and the other end of the _third inductor L3 is connected to the third second The cathode of the diode _D3 is connected to the source of the _third power switch S3, the anode of the third diode _D3 is connected to the cathode of the second input source _Vb , and the drain of the _third power switch S3 is connected to the seventh The cathode of the diode _D7 , the anode of the _seventh diode D7 is connected to the drain of the _first power switch tube S1, the anode of the _fourth diode D4 and the cathode of the _third capacitor C3 are connected to the first power _The drain of the switch tube S1, the cathode of the _fourth diode D4 is connected to the anode of the _fifth diode D5, the cathode of the fourth capacitor _C4 and the anode of the fifth capacitor _C5 , the _third capacitor C3 The anode and the cathode of the _fifth diode D5 are connected to the anode of the _sixth diode D6, the cathode of the _sixth diode D6 is connected to the anode of the fourth capacitor _C4 and one end of the load R, and the fifth capacitor _C5 The negative electrode of the load R and the other end of the load R are connected to the source of the first power switch tube S ₁ ; the first inductor L ₁ , the second inductor L ₂ , the first capacitor C ₁ , the second capacitor C ₂ , the second diode The transistor D ₂ , the shunt diode D ₀ and the first power switch transistor S ₁ form a quasi-Z source structure, and then the fourth diode D 4 , the fifth diode D 5 , the sixth diode D 6 , the fourth diode D ₄ , the fifth diode D ₅ , the sixth diode D ₆ , The three capacitors C ₃ , the fourth capacitor C ₄ and the fifth capacitor C ₅ form the capacitor unit of the switch to boost the voltage. The third inductor L ₃ , the third diode D ₃ , and the seventh diode D ₇ and the _third power switch tube S3 form a second input source _Vb charging loop with continuous output current. 2. the three-port DC-DC converter based on quasi-Z source and switched capacitor according to claim 1, is characterized in that, comprises three kinds of modes, respectively are single-input single-output, single-input double-output mode, double-input single-output In the output mode, in the single-input single-output mode, the _first power switch S1 works; in the single-input dual-output mode, the _first power switch S1 and the _third power switch S3 work; in the dual-input single-output mode, The _first power switch S1 and the _second power switch S2 work. 3. The three-port DC-DC converter based on quasi-Z source and switched capacitor according to claim 2, is characterized in that, in one switching cycle, under single-input single-output mode, the converter has two operating modes , in the first mode, the _first power switch S1 is turned on, the first input source _Vpe and the _second capacitor C2 charge the first inductor L1, and the _first capacitor _C1 charges the _second inductor L2 , the fifth capacitor _C5 charges the _third capacitor C3, and at the same time supplies power to the load R together with the fourth capacitor _C4 . In the second mode, the _first power switch S1 is turned off, and the first input source _Vpe Combined with the first inductor L ₁ , the second inductor L ₂ and the third capacitor C ₃ to jointly charge the first capacitor C ₁ , the second capacitor C ₂ , the fourth capacitor C ₄ , and the fifth capacitor C ₅ , and supply power to the load R . 4. The three-port DC-DC converter based on quasi-Z source and switched capacitor according to claim 2, is characterized in that, in one switching cycle, the converter has three operating modes under the single-input dual-output mode, and In the first mode, the _first power switch S1 is turned on, and the _third power switch S3 is turned off. At this time, the first input source _Vpe and the _second capacitor C2 charge the _first inductor L1, and the first power switch S3 is turned off. The capacitor C ₁ charges the second inductor L ₂ , the fifth capacitor C ₅ charges the third capacitor C ₃ , and together with the fourth capacitor C ₄ supplies power to the load R, and the third inductor L ₃ charges the second input source V _b , in the second mode, the _first power switch S1 is turned off, and the third power switch S3 is turned on. At this time, the first input source V _pe is combined with the first inductor L ₁ , the second inductor L ₂ and the third power switch S ₃ . The three capacitors C ₃ jointly charge the third inductor L ₃ , the first capacitor C ₁ , the second capacitor C ₂ , the fourth capacitor C ₄ , and the fifth capacitor C ₅ , and supply power for the second input source V _b and the load R, In the third mode, the first power switch S ₁ and the third power switch S ₃ are turned off, and the first input source V _pe is combined with the first inductor L ₁ , the second inductor L ₂ and the third capacitor C ₃ . It charges the first capacitor C ₁ , the second capacitor C ₂ , the fourth capacitor C ₄ , and the fifth capacitor C ₅ , and supplies power to the load R, and the third inductor L ₃ charges the second input source V _b . 5. The three-port DC-DC converter based on quasi-Z source and switched capacitor according to claim 2, is characterized in that, in one switching cycle, the converter has three operating modes under the dual-input single-output mode, and In the first mode, the _first power switch S1 and the _second power switch S2 are turned on, the second input source _Vb and the _second capacitor C2 charge the _first inductor L1, and the first capacitor _C1 provides The _second inductor L2 charges, the fifth capacitor _C5 charges the _third capacitor C3, and together with the fourth capacitor _C4 supplies power to the load R, in the second mode, the _first power switch S1 is turned off, The second power switch S ₂ is turned on, and the second input source V _b is combined with the first inductor L ₁ , the second inductor L ₂ and the third capacitor C ₃ to form the first capacitor C ₁ , the second capacitor C ₂ , and the fourth capacitor C 2 . The capacitor C ₄ and the fifth capacitor C ₅ are charged and supply power to the load R. In the third mode, the _first power switch S1 and the _second power switch S2 are turned off, and the first input source _Vpe is combined with the first power switch S1 and the second power switch S2. An inductor L ₁ , a second inductor L ₂ and a third capacitor C ₃ jointly charge the first capacitor C ₁ , the second capacitor C ₂ , the fourth capacitor C ₄ , and the fifth capacitor C ₅ , and supply power to the load R. 6. a kind of competition control method based on the described three-port DC-DC converter of claim 1, is characterized in that, is specifically as follows: If it is currently in the single-input single-output mode, when the duty cycle of the _first power switch S1 reaches the upper limit, it switches to the dual-input single-output mode; when the state of charge SOC of the second input source _Vb is less than the lower limit, Switch to single input dual output mode; If it is currently in the single-input dual-output mode, when the SOC of the second input source _Vb reaches the maximum value, it switches to the single-input single-output mode; when the duty cycle of the _third power switch S3 reaches the upper limit value, it switches to the dual-input single-output mode mode switch; If it is currently in the dual-input single-output mode, when the SOC of the second input source V _b is in a given range, it switches to the single-input single-output mode; when the SOC of the second input source V _b is less than the lower limit, it switches to the single-input dual-output mode. Output mode switch.

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