A non-isolated multi-mode three-port DC-DC converter and control method

Abstract

A non-isolated multi-mode three-port DC-DC converter, comprising a photovoltaic voltage source V pv , a battery voltage source V bat , a first power switch S1, a second power switch S2, a third power switch S3, a first diode D1, a second diode D2, a first inductor L1, a second inductor L2, a first capacitor C1, a second capacitor C2, a third capacitor C3 and an output voltage V o ; the output voltage V o port is equivalent to connecting a load R and a DC voltage source V DC under different working modes; the application has seven different working modes, covering all possible power flow combinations among the three ports; various working modes can be seamlessly and smoothly switched to realize maximum power tracking, battery protection and output voltage regulation; the control of each power switch is realized through a DSP chip, and the application has the advantages of fewer components, high efficiency, low cost, small size, wide voltage range and application in DC micro-grid and regenerative braking.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronics, and particularly relates to a non-isolated multi-mode three-port DC-DC converter and a control method. BACKGROUND

[0002] The three-port converter (TPC) can realize the functions of multiple input and multiple output, improve the reliability of the converter, and is widely applied in the fields of photovoltaic power generation, hybrid power systems, electric vehicles and fuel cell systems. The TPC in the application of the photovoltaic cell can include a PV source of a unidirectional port, a battery and an output port as bidirectional ports, however, most of the researches are only directed to the TPC with a unidirectional output port, and the working mode is relatively single, the mode conversion time is long, and the discussion on other power flow modes and the bidirectional operation of the converter is less.

[0003] For the research on the TPC, some researchers propose a transformer-coupled dual-input converter, which has a balance control capability and can select between the maximum power point tracking and the battery voltage regulation of the unidirectional output port, however, due to the limitation of the topological structure, it is not allowed to work in the no-load mode, the mode conversion also has a delay, and is accompanied by a voltage overshoot of 50%. Some researchers propose a bidirectional output port TPC, which can realize all possible power flow combinations between the power supply and the load under different switching modes, but has the defect of an increased number of elements. For the integrated TPC, the periodic insertion of the switching mode in the controller is easy to cause response noise and delay. It can be seen that the TPC has the problems of single application mode, mode switching delay and structural load, which will restrict the application of the TPC in the field of photovoltaic power generation. SUMMARY

[0004] In order to overcome the defects of the prior art, the purpose of the present application is to provide a non-isolated multi-mode three-port DC-DC converter and a control method thereof, which covers all possible power flow combinations among the three ports, has a small number of elements, is high in efficiency, and can realize seamless and smooth switching of the working mode, maximum power tracking, battery protection and output voltage regulation.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is:

[0006] A non-isolated multi-mode three-port DC-DC converter, characterized in that it comprises a photovoltaic voltage source V pv , a battery voltage source V bat , a first power switch tube S1, a second power switch tube S2, a third power switch tube S3, a first diode D1, a second diode D2, a first inductor L1, a second inductor L2, a first capacitor C1, a second capacitor C2, a third capacitor C3 and an output voltage V o .

[0007] The drain of the first power switch is connected to the negative terminal of the first diode and the positive terminal of the first capacitor, and the source is connected to one end of the first inductor and the negative terminal of the second diode.

[0008] The drain of the second power switch is connected to the other end of the first inductor, the positive terminal of the battery voltage source, and the positive terminal of the third capacitor, while the source is connected to one end of the second inductor and the drain of the third power switch.

[0009] The source of the third power switch is connected to the negative terminal of the second capacitor, the negative terminal of the output voltage, and the negative terminal of the photovoltaic voltage source.

[0010] The other end of the second inductor is connected to the positive terminal of the second capacitor, the negative terminal of the third capacitor, the negative terminal of the battery voltage source, the negative terminal of the second diode, the negative terminal of the first capacitor, and the positive terminal of the output voltage.

[0011] The positive terminal of the first diode is connected to the positive terminal of the photovoltaic voltage source.

[0012] The output voltage V o The port is equivalent to connecting the load R and the DC voltage source V in different operating modes. DC ;

[0013] The first power switch, the second power switch, and the third power switch are all MOSFET switches of type IRFB5620.

[0014] The first power switch, the second power switch, and the third power switch are all equipped with diodes connected in parallel.

[0015] The first power switch, the second power switch, and the third power switch all operate at a frequency of 50kHz.

[0016] The photovoltaic voltage source is model EA-PSI9360-15;

[0017] The battery voltage source has a voltage of 25V and a current of 7.2A;

[0018] Both the first diode and the second diode are model MBR20100CT;

[0019] The first capacitor has a capacitance of 100μF, the second capacitor has a capacitance of 180μF, and the third capacitor has a capacitance of 120μF.

[0020] The inductance values ​​of both the first and second inductors are 184 μH.

[0021] A control method for a non-isolated multi-mode three-port DC-DC converter includes the following steps:

[0022] Step one, sampling the voltage and current of the photovoltaic side of the three-port DC-DC converter; sampling the voltage of the battery and the bus side;

[0023] Step two, sending the digitized voltage and current values to the DSP controller after processing, and the DSP controller outputs the duty cycle to control the three-port DC-DC converter;

[0024] Step three, by controlling the conduction and turn-off of the three power switches, seven working modes can be realized;

[0025] Mode one: in this mode, the power flow direction is from the photovoltaic voltage source V pv to the battery voltage source V bat and the DC bus; the output voltage V o port is equivalent to connecting the load R; the second power switch S2 and the third power switch S3 are always turned off; this mode includes two working stages; in the first stage, the first power switch S1 is turned on, the first diode D1 is forward biased and in the conduction state, the second diode D2 is reverse biased and in the cut-off state, the photovoltaic voltage source V pv charges the first inductor L1, in the second stage, the first power switch S1 is turned off, the first diode D1 and the second diode D2 are both forward biased and in the conduction state, the first inductor L1 discharges to the battery voltage source V bat through the second diode D2;

[0026] Mode two: in this mode, the power flow direction is from the battery voltage source V bat to the DC bus; the output voltage V o port is equivalent to connecting the load R; the first power switch S1 is always turned off, and the first diode D1 and the second diode D2 are both reverse biased and in the cut-off state; this mode includes two working stages; in the first stage, the second power switch S2 is turned on, the third power switch S3 is turned off, the battery voltage source V bat and the third capacitor C3 charge the second inductor, the voltage across the second inductor charges to the second capacitor discharges to the DC bus; in the second stage, the second power switch S2 is turned off, the third power switch S3 is turned on, the second inductor L2 discharges to the DC bus until

[0027] Mode three: in this mode, the power flow direction is from the DC bus to the battery voltage source V bat ; the output voltage V o port is equivalent to connecting the DC voltage source V DC; the first power switch S1 is always off, the first diode D1 and the second diode D2 are both reverse-biased and in cut-off state; this mode includes two working stages; in the first stage, the second power switch S2 is off, the third power switch S3 is on, and the third capacitor C3 charges the second inductor L2; in the second stage, the second power switch S2 is on, the third power switch S3 is off, and the second inductor L2 discharges to the battery voltage source V bat and the third capacitor C3;

[0028] Mode four: in this mode, the power flow direction is from the photovoltaic voltage source V pv and the battery voltage source V bat to the DC bus; the output voltage V o port is equivalent to connecting the load R; the first diode D1 is always forward-biased and in on state; this mode includes four working stages; in the first stage, the first power switch S1 and the second power switch S2 are on, the third power switch S3 is off, the second diode D2 is reverse-biased and in cut-off state, the photovoltaic voltage source V pv charges the first inductor L1, the battery voltage source V bat charges the second inductor L2 through the second power switch S2; in the second stage, the first power switch S1 and the third power switch S3 are on, the second power switch S2 is off, the second diode D2 is reverse-biased and in cut-off state, the photovoltaic voltage source V pv continues to charge the first inductor L1, and the second inductor L2 discharges to the DC bus and the second capacitor C2; in the third stage, the third power switch S3 is on, the first power switch S1 and the second power switch S2 are off, the second diode D2 is forward-biased and in on state, the first inductor L1 discharges to the battery voltage source V bat , and the second inductor L2 continues to discharge to the DC bus; in the fourth stage, the second power switch S2 is on, the first power switch S1 and the third power switch S3 are off, the second diode D2 is forward-biased and in on state, the battery voltage source V bat and the first inductor L1 charge the second inductor L2;

[0029] Mode five: in this mode, the power flow direction is from the photovoltaic voltage source V pv and the DC bus to the battery voltage source V bat ; the output voltage V o port is equivalent to connecting the DC voltage source V DC ; the first diode D1 is always forward-biased and in on state; this mode includes four working stages; in the first stage, the first power switch S1 and the third power switch S3 are on, the second power switch S2 is off, the second diode D2 is reverse-biased and in cut-off state, the photovoltaic voltage source V pvcharging the first inductor L1, The DC bus charges the second inductor L2 through the third power switch S3, In the second stage, the first power switch S1 and the second power switch S2 are turned on, the third power switch S3 is turned off, the second diode D2 is reverse-biased and in the off state, the photovoltaic voltage source V pv The first inductor L1 continues to be charged, and the second inductor L2 discharges to the battery voltage source V bat discharge; in the third stage, the second power switch S2 is turned on, the first power switch S1 and the third power switch S3 are turned off, the second diode D2 is forward-biased and in the on state, and the first inductor L1 discharges to the battery voltage source V bat discharge, and the second inductor L2 continues to discharge to the battery voltage source V bat discharge; in the fourth stage, the third power switch S3 is turned on, the first power switch S1 and the second power switch S2 are turned off, the second diode D2 is forward-biased and in the on state, and the first inductor L1 continues to discharge to the battery voltage source V bat discharge, and the DC bus charges the second inductor L2;

[0030] Mode six: in this mode, the power flow direction is from the photovoltaic voltage source V pv to the DC bus; the output voltage V o the port is equivalent to connecting a load R; the first power switch S1 is always kept on; the first diode D1 is always forward-biased and in the on state, and the second diode D2 is always reverse-biased and in the off state; this mode includes two working stages; in the first stage, the first power switch S1 and the second power switch S2 are turned on, the third power switch S3 is turned off, the photovoltaic voltage source V pv charges the first inductor L1 and the second inductor L2, In the second stage, the first power switch S1 and the third power switch S3 are turned on, the second power switch S2 is turned off, and the photovoltaic voltage source V pv continues to charge the first inductor L1, and the second inductor L2 discharges to the DC bus;

[0031] Mode seven: in this mode, the power flow direction is from the photovoltaic voltage source V pv to the battery voltage source V bat ; the output voltage V o the port is equivalent to connecting a load R; the first diode D1 is always forward-biased and in the on state; this mode includes four working stages; in the first stage, the first power switch S1 and the third power switch S3 are turned on, the second power switch S2 is turned off, the second diode D2 is reverse-biased and in the off state, and the photovoltaic voltage source V pv charges the first inductor L1, the second capacitor C2 charges the second inductor L2, In the second stage, the first power switch S1 and the second power switch S2 are turned on, the third power switch S3 is turned off, the second diode D2 is in reverse bias and in the off state, the photovoltaic voltage source V pv The first inductor L1 continues to be charged, and the second inductor L2 discharges to the battery voltage source V bat Discharge; in the third stage, the second power switch S2 is turned on, the first power switch S1 and the third power switch S3 are turned off, the second diode D2 is in forward bias and in the on state, and the first inductor L1 discharges to the battery voltage source V bat Discharge, the second inductor L2 continues to discharge to the battery voltage source V bat Discharge; in the fourth stage, the third power switch S3 is turned on, the first power switch S1 and the second power switch S2 are turned off, the second diode D2 is in forward bias and in the on state, and the first inductor L1 continues to discharge to the battery voltage source V bat Discharge, the second capacitor C2 charges the second inductor L2.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] The present application provides a non-isolated multi-mode three-port DC-DC converter, which adopts a non-isolated structure, is more compact in structure, lower in cost and smaller in size compared with an isolated three-port converter; has seven working modes, can realize all possible power flow combinations among the source, the storage and the load in different switching modes, and achieve the control targets of maximum power point tracking, battery protection and output voltage regulation; only one power processing stage between any two ports is needed to realize high efficiency and complete control over the ports; smooth switching of each mode can be realized by applying a simple switching control scheme; compared with existing integrated three-port converters, there is no delay in mode switching, the voltage overshoot is small, and the recovery time is short; in addition, the circuit topology can provide a voltage lower or higher than the DC bus, has a wide voltage range, has a small number of components, can maintain high working efficiency in all working modes, and is suitable for independent and grid-connected applications. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The present application provides a non-isolated multi-mode three-port DC-DC converter, which adopts a non-isolated structure, is more compact in structure, lower in cost and smaller in size compared with an isolated three-port converter; has seven working modes, can realize all possible power flow combinations among the source, the storage and the load in different switching modes, and achieve the control targets of maximum power point tracking, battery protection and output voltage regulation; only one power processing stage between any two ports is needed to realize high efficiency and complete control over the ports; smooth switching of each mode can be realized by applying a simple switching control scheme; compared with existing integrated three-port converters, there is no delay in mode switching, the voltage overshoot is small, and the recovery time is short; in addition, the circuit topology can provide a voltage lower or higher than the DC bus, has a wide voltage range, has a small number of components, can maintain high working efficiency in all working modes, and is suitable for independent and grid-connected applications.

[0035] Figure 2 The present application provides a non-isolated multi-mode three-port DC-DC converter, which adopts a non-isolated structure, is more compact in structure, lower in cost and smaller in size compared with an isolated three-port converter; has seven working modes, can realize all possible power flow combinations among the source, the storage and the load in different switching modes, and achieve the control targets of maximum power point tracking, battery protection and output voltage regulation; only one power processing stage between any two ports is needed to realize high efficiency and complete control over the ports; smooth switching of each mode can be realized by applying a simple switching control scheme; compared with existing integrated three-port converters, there is no delay in mode switching, the voltage overshoot is small, and the recovery time is short; in addition, the circuit topology can provide a voltage lower or higher than the DC bus, has a wide voltage range, has a small number of components, can maintain high working efficiency in all working modes, and is suitable for independent and grid-connected applications.

[0036] Figure 3 The present application provides a non-isolated multi-mode three-port DC-DC converter, which adopts a non-isolated structure, is more compact in structure, lower in cost and smaller in size compared with an isolated three-port converter; has seven working modes, can realize all possible power flow combinations among the source, the storage and the load in different switching modes, and achieve the control targets of maximum power point tracking, battery protection and output voltage regulation; only one power processing stage between any two ports is needed to realize high efficiency and complete control over the ports; smooth switching of each mode can be realized by applying a simple switching control scheme; compared with existing integrated three-port converters, there is no delay in mode switching, the voltage overshoot is small, and the recovery time is short; in addition, the circuit topology can provide a voltage lower or higher than the DC bus, has a wide voltage range, has a small number of components, can maintain high working efficiency in all working modes, and is suitable for independent and grid-connected applications.

[0037] Figure 4The first working stage of the second mode in the embodiment of the present application is shown in the figure.

[0038] Figure 5 The second working stage of the second mode in the embodiment of the present application is shown in the figure.

[0039] Figure 6 The first working stage of the third mode in the embodiment of the present application is shown in the figure.

[0040] Figure 7 The second working stage of the third mode in the embodiment of the present application is shown in the figure.

[0041] Figure 8 The first working stage of the fourth mode in the embodiment of the present application is shown in the figure.

[0042] Figure 9 The second working stage of the fourth mode in the embodiment of the present application is shown in the figure.

[0043] Figure 10 The third working stage of the fourth mode in the embodiment of the present application is shown in the figure.

[0044] Figure 11 The fourth working stage of the fourth mode in the embodiment of the present application is shown in the figure.

[0045] Figure 12 The first working stage of the fifth mode in the embodiment of the present application is shown in the figure.

[0046] Figure 13 The second working stage of the fifth mode in the embodiment of the present application is shown in the figure.

[0047] Figure 14 The third working stage of the fifth mode in the embodiment of the present application is shown in the figure.

[0048] Figure 15 The fourth working stage of the fifth mode in the embodiment of the present application is shown in the figure.

[0049] Figure 16 The first working stage of the sixth mode in the embodiment of the present application is shown in the figure.

[0050] Figure 17 The second working stage of the sixth mode in the embodiment of the present application is shown in the figure.

[0051] Figure 18 The first working stage of the seventh mode in the embodiment of the present application is shown in the figure.

[0052] Figure 19 The second working stage of the seventh mode in the embodiment of the present application is shown in the figure.

[0053] Figure 20 Fig. 7 is a schematic diagram of the third working stage of the seventh mode of the embodiment of the present application.

[0054] Figure 21 Fig. 8 is a schematic diagram of the fourth working stage of the seventh mode of the embodiment of the present application.

[0055] Figure 22 Fig. 9 is a control structure block diagram of the embodiment of the present application.

[0056] Figure 23 Fig. 10 is a flow chart of the seven working modes of the embodiment of the present application.

[0057] Fig. 1 is a schematic diagram of the embodiment of the present application. pv Fig. 2 is a schematic diagram of the embodiment of the present application. bat Fig. 3 is a schematic diagram of the embodiment of the present application. o Fig. 4 is a schematic diagram of the embodiment of the present application. DETAILED DESCRIPTION

[0058] The technical solutions of the present application will be described clearly and completely below in combination with the drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.

[0059] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0060] The present application will be described in further detail below in combination with the drawings:

[0061] Referring to Figure 1 , the non-isolated multi-mode three-port DC-DC converter of the present application includes a photovoltaic voltage source V pv , a battery voltage source Vbat , a first power switch S1, a second power switch S2, a third power switch S3, a first diode D1, a second diode D2, a first inductor L1, a second inductor L2, a first capacitor C1, a second capacitor C2, a third capacitor C3 and an output voltage V o ;

[0062] The drain of the first power switch is connected to the negative pole of the first diode and the positive pole of the first capacitor, and the source is connected to one end of the first inductor and the negative pole of the second diode;

[0063] The drain of the second power switch is connected to the other end of the first inductor, the positive pole of the battery voltage source and the positive pole of the third capacitor, and the source is connected to one end of the second inductor and the drain of the third power switch;

[0064] The source of the third power switch is connected to the negative pole of the second capacitor, the negative pole of the output voltage and the negative pole of the photovoltaic voltage source;

[0065] The other end of the second inductor is connected to the positive pole of the second capacitor, the negative pole of the third capacitor, the negative pole of the battery voltage source, the negative pole of the second diode, the negative pole of the first capacitor and the positive pole of the output voltage;

[0066] The positive pole of the first diode is connected to the positive pole of the photovoltaic voltage source.

[0067] A preferred example of the present application is that the output voltage V o port is equivalent to connecting the load R and the DC voltage source V DC ;

[0068] Another preferred example of the present application is that the first power switch, the second power switch, the third power switch are all MOSFET switches with model IRFB5620.

[0069] Another preferred example of the present application is that the first power switch, the second power switch, the third power switch are all provided with diodes connected in parallel.

[0070] Another preferred example of the present application is that the first power switch, the second power switch, the third power switch all have a working frequency of 50KHz.

[0071] Another preferred example of the present application is that the photovoltaic voltage source is of model EA-PSI9360-15;

[0072] Another preferred example of the present application is that the battery voltage source has a voltage of 25V and a current of 7.2A;

[0073] In another preferred embodiment of the present invention, both the first diode and the second diode are of model MBR20100CT;

[0074] Another preferred embodiment of the present invention is that the first capacitor has a capacitance of 100μF, the second capacitor has a capacitance of 180μF, and the third capacitor has a capacitance of 120μF.

[0075] In another preferred embodiment of the present invention, the inductance values ​​of the first inductor and the second inductor are both 184 μH.

[0076] This invention discloses a non-isolated multi-mode three-port DC-DC converter, comprising the following steps:

[0077] Step 1: Sample the voltage and current on the photovoltaic side of the three-port DC-DC converter; sample the voltage on the battery side and the bus side.

[0078] Step 2: The collected voltage and current values ​​are digitized and then sent to the DSP controller. The DSP controller outputs the duty cycle to control the three-port DC-DC converter.

[0079] Step 3: By controlling the on and off of the three power switching transistors, seven operating modes can be achieved.

[0080] Mode 1: In this mode, the power flow direction is from the photovoltaic voltage source V. pv Flow to battery voltage source V bat and DC bus; output voltage V o The port is equivalent to a connected load R; the second power switch S2 and the third power switch S3 are always kept off; this mode includes two operating phases; in the first phase, such as Figure 2 As shown, the first power switch S1 is turned on, the first diode D1 is forward biased and in the conducting state, the second diode D2 is reverse biased and in the cutoff state, and the photovoltaic voltage source V... pv Charge the first inductor L1. In the second stage, such as Figure 3 As shown, the first power switch S1 is turned off, and both the first diode D1 and the second diode D2 are forward biased and in the conducting state. The first inductor L1 supplies power to the battery voltage source V through the second diode D2. bat Discharge;

[0081] Mode 2: In this mode, the power flow direction is from the battery voltage source V. bat Flows to the DC bus; Output voltage V o The port is equivalent to a connected load R; the first power switch S1 is always off, and the first diode D1 and the second diode D2 are both reverse biased and in the off state; this mode includes two operating phases; in the first phase, such as Figure 4As shown, the second power switch S2 is turned on, the third power switch S3 is turned off, and the battery voltage source V... bat The third capacitor C3 charges the second inductor, and the voltage across the second inductor is charged to... The second capacitor discharges to the DC bus; in the second stage, such as Figure 5 As shown, the second power switch S2 is turned off, the third power switch S3 is turned on, and the second inductor L2 discharges to the DC bus until...

[0082] Mode 3: In this mode, the power flow direction is from the DC bus to the battery voltage source V. bat Output voltage V o The port is equivalent to a connection to a DC voltage source V. DC The first power switch S1 remains off at all times, and both the first diode D1 and the second diode D2 are reverse biased and in the off state. This mode includes two operating phases. In the first phase, such as... Figure 6 As shown, the second power switch S2 is turned off, the third power switch S3 is turned on, and the third capacitor C3 charges the second inductor L2; in the second stage, as... Figure 7 As shown, the second power switch S2 is turned on, the third power switch S3 is turned off, and the second inductor L2 supplies voltage to the battery voltage source V. bat Discharge with the third capacitor C3;

[0083] Mode 4: In this mode, the power flow direction is from the photovoltaic voltage source V. pv and battery voltage source V bat Flows to the DC bus; Output voltage V o The port is equivalent to a connected load R; the first diode D1 is always forward biased and in the conducting state; this mode includes four operating phases; in the first phase, such as Figure 8 As shown, the first power switch S1 and the second power switch S2 are turned on, the third power switch S3 is turned off, the second diode D2 is reverse biased and in the off state, and the photovoltaic voltage source V... pv Charging the first inductor L1, the battery voltage source V bat The second inductor L2 is charged through the second power switch S2; in the second stage, such as Figure 9 As shown, the first power switch S1 and the third power switch S3 are turned on, the second power switch S2 is turned off, and the second diode D2 is reverse biased and in the off state. The photovoltaic voltage source V pv Continue charging the first inductor L1, while the second inductor L2 discharges to the DC bus and the second capacitor C2; in the third stage, as... Figure 10 As shown, the third power switch S3 is turned on, the first power switch S1 and the second power switch S2 are turned off, the second diode D2 is forward biased and in the conducting state, and the first inductor L1 supplies voltage to the battery voltage source V.bat Discharge continues, with the second inductor L2 continuing to discharge to the DC bus; in the fourth stage, such as Figure 11 As shown, the second power switch S2 is turned on, the first power switch S1 and the third power switch S3 are turned off, the second diode D2 is forward biased and in the conducting state, and the battery voltage source V bat The first inductor L1 charges the second inductor L2;

[0084] Mode 5: In this mode, the power flow direction is from the photovoltaic voltage source V. pv And the DC bus flows to the battery voltage source V bat Output voltage V o The port is equivalent to a connection to a DC voltage source V. DC The first diode D1 is always forward biased and in the conducting state; this mode includes four operating stages; in the first stage, such as... Figure 12 As shown, the first power switch S1 and the third power switch S3 are turned on, the second power switch S2 is turned off, and the second diode D2 is reverse biased and in the off state. The photovoltaic voltage source V pv Charge the first inductor L1. The DC bus charges the second inductor L2 through the third power switch S3. In the second stage, such as Figure 13 As shown, the first power switch S1 and the second power switch S2 are turned on, the third power switch S3 is turned off, the second diode D2 is reverse biased and in the off state, and the photovoltaic voltage source V... pv The first inductor L1 continues to charge, while the second inductor L2 supplies power to the battery voltage source V. bat Discharge; in the third stage, such as Figure 14 As shown, the second power switch S2 is turned on, the first power switch S1 and the third power switch S3 are turned off, the second diode D2 is forward biased and in the conducting state, and the first inductor L1 supplies voltage to the battery voltage source V. bat During discharge, the second inductor L2 continues to supply voltage to the battery voltage source V. bat Discharge; in the fourth stage, such as Figure 15 As shown, the third power switch S3 is turned on, the first power switch S1 and the second power switch S2 are turned off, the second diode D2 is forward biased and in the conducting state, and the first inductor L1 continues to supply voltage to the battery voltage source V. bat Discharge occurs, and the DC bus charges the second inductor L2.

[0085] Mode 6: In this mode, the power flow direction is from the photovoltaic voltage source V. pv Flows to the DC bus; Output voltage V oThe port is equivalent to connecting the load R; the first power switch S1 is always kept open; the first diode D1 is always forward biased to be in the on state, and the second diode D2 is always reverse biased to be in the off state; the mode includes two working stages; in the first stage, as shown in Figure 16 the first power switch S1, the second power switch S2 are open, and the third power switch S3 is off; the photovoltaic voltage source V pv charges the first inductor L1 and the second inductor L2, in the second stage, as shown in Figure 17 the first power switch S1 and the third power switch S3 are open, and the second power switch S2 is off; the photovoltaic voltage source V pv continues to charge the first inductor L1, and the second inductor L2 discharges to the DC bus;

[0086] Mode seven: in this mode, the power flow direction is from the photovoltaic voltage source V pv to the battery voltage source V bat ; the output voltage V o is equivalent to connecting the load R; the first diode D1 is always forward biased to be in the on state; the mode includes four working stages; in the first stage, as shown in Figure 18 the first power switch S1 and the third power switch S3 are open, and the second power switch S2 is off; the second diode D2 is reverse biased to be in the off state, and the photovoltaic voltage source V pv charges the first inductor L1, the second capacitor C2 charges the second inductor L2, in the second stage, as shown in Figure 19 the first power switch S1 and the second power switch S2 are open, and the third power switch S3 is off; the second diode D2 is reverse biased to be in the off state, and the photovoltaic voltage source V pv continues to charge the first inductor L1, and the second inductor L2 discharges to the battery voltage source V bat ; in the third stage, as shown in Figure 20 the second power switch S2 is open, the first power switch S1 and the third power switch S3 are off, and the second diode D2 is forward biased to be in the on state; the first inductor L1 discharges to the battery voltage source V bat , and the second inductor L2 continues to discharge to the battery voltage source V bat ; in the fourth stage, as shown in Figure 21 the third power switch S3 is open, the first power switch S1 and the second power switch S2 are off, and the second diode D2 is forward biased to be in the on state; the first inductor L1 continues to discharge to the battery voltage source V bat , and the second capacitor C2 charges the second inductor L2;

[0087] Referring toFigure 22 , the control structure block diagram of the converter; the second power switch S2 and the third power switch S3 are complementary on in different modes, and the control target includes maximum power tracking, battery protection and output voltage regulation; the maximum power tracking is realized by the first power switch S1, and the second power switch S2 and the third power switch S3 are responsible for battery protection and output voltage regulation at the same time; a DSP controller with model TMS32F28397D is used to control the converter;

[0088] Referring to Figure 23 , the flow chart of seven working modes;

[0089] When the system is only without photovoltaic voltage source, if the battery voltage source can provide the required power for the DC bus, the power flow is from the battery voltage source to the DC bus; if the battery voltage source cannot provide the required power for the DC bus, the power flow is from the DC bus to the battery voltage source; if the battery reaches the charging limit and the DC bus cannot charge it any more, the system is shut down;

[0090] When the system is only without load, if the power of the photovoltaic voltage source is less than the maximum allowable absorption power of the battery voltage source, the photovoltaic voltage source will work in the MPPT mode if the power of the photovoltaic voltage source is greater than the maximum allowable absorption power of the battery voltage source, the MPPT mode is not used; if the battery reaches the charging limit, the system is shut down;

[0091] When the power of the photovoltaic voltage source is greater than the power of the battery voltage source, if P pv -P DC <P bat.max , the MPPT mode is used; if P pv -P DC >P bat.max , the MPPT mode is not used;

[0092] When the power of the photovoltaic voltage source is less than the power of the battery voltage source, if P DC -P pv <P bat.max and the battery voltage source can be discharged, the power flow is from the photovoltaic voltage source and the battery voltage source to the DC bus; if P DC -P pv <P bat.max and the battery voltage source cannot continue to be discharged, the power flow is from the photovoltaic voltage source and the DC bus to the battery voltage source;

[0093] When P DC -P pv >P bat.max , if the battery voltage source can continue to be charged, the power flow is from the photovoltaic voltage source to the battery voltage source, if the charging limit is reached and the charging cannot continue, the system is shut down.

[0094] The above merely illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application, on the basis of the technical scheme, falls within the protection scope of the present application.

Claims

1. A non-isolated multi-mode three-port DC-DC converter, characterized in that, A photovoltaic voltage source V pv , a battery voltage source V bat , a first power switch S1, a second power switch S2, a third power switch S3, a first diode D1, a second diode D2, a first inductor L1, a second inductor L2, a first capacitor C1, a second capacitor C2, a third capacitor C3, and an output voltage V o ; The drain of the first power switch S1 is connected with the negative pole of the first diode D1 and the positive pole of the first capacitor C1, and the source is connected with one end of the first inductor L1 and the negative pole of the second diode D2; The drain of the second power switch tube S2 is connected with the other end of the first inductor L1, the positive pole of the battery voltage source V bat and the positive pole of the third capacitor C3, and the source is connected with one end of the second inductor L2 and the drain of the third power switch tube S3. The source of the third power switch tube S3 is connected with the negative pole of the second capacitor C2, the output voltage V o and the negative pole of the photovoltaic voltage source V pv ; The other end of the second inductor L2 is connected to the positive pole of the second capacitor C2, the negative pole of the third capacitor C3, the negative pole of the battery voltage source V bat , the positive pole of the second diode D2, the negative pole of the first capacitor C1 and the positive pole of the output voltage V o . The anode of the first diode D1 is connected to the anode of the photovoltaic voltage source V pv The anode of the first diode D1 is connected to the anode of the photovoltaic voltage source V 2. The non-isolated multi-mode three-port DC-DC converter of claim 1, wherein, The output voltage V o The port is equivalent to connecting a load R and a DC voltage source V DC .

3. The non-isolated multi-mode three-port DC-DC converter of claim 1, wherein, The first power switch S1, the second power switch S2 and the third power switch S3 are MOSFET switches with the model of IRFB5620.

4. The non-isolated multi-mode three-port DC-DC converter of claim 1, wherein, The first power switch S1, the second power switch S2 and the third power switch S3 are all provided with parallelly connected diodes.

5. The non-isolated multi-mode three-port DC-DC converter of claim 1, wherein, The working frequency of the first power switch S1, the second power switch S2 and the third power switch S3 is all 50KHz.

6. The non-isolated multi-mode three-port DC-DC converter of claim 1, wherein, The photovoltaic voltage source V pv Model EA-PSI9360-15.

7. The non-isolated multi-mode three-port DC-DC converter of claim 1, wherein, The battery voltage source V bat The voltage was 25 V and the current was 7.2 A.

8. The non-isolated multi-mode three-port DC-DC converter of claim 1, wherein, The first diode D1 and the second diode D2 are both with the model of MBR20100CT.

9. The non-isolated multi-mode three-port DC-DC converter of claim 1, wherein, The capacitance of the first capacitor C1 is 100μF, the capacitance of the second capacitor C2 is 180μF, and the capacitance of the third capacitor C3 is 120μF; the inductance of the first inductor L1 and the second inductor L2 is all 184μH.

10. The method of claim 1-9, wherein the non-isolated multi-mode three-port DC-DC converter control method is characterized by, The method comprises the following steps: Step one, sampling the voltage and current of the photovoltaic side of the three-port DC-DC converter, and sampling the voltage of the battery and the bus side; Step two, sending the digitized voltage and current values into the DSP controller after processing, and outputting the duty cycle of the DSP controller to control the three-port DC-DC converter; Step three, controlling the conduction and shutdown of the three power switches to realize seven working modes. Mode one: in this mode, the power flow direction is from the photovoltaic voltage source V pv to the battery voltage source V bat and the DC bus; the output voltage V o port is equivalent to connecting the load R; the second power switch S2 and the third power switch S3 are always kept off; this mode includes two working stages; in the first stage, the first power switch S1 is turned on, the first diode D1 is forward biased and in the conducting state, the second diode D2 is reverse biased and in the cut-off state, the photovoltaic voltage source V pv charges the first inductor L1, In the second stage, the first power switch S1 is turned off, the first diode D1 and the second diode D2 are both forward biased and in the conducting state, the first inductor L1 discharges to the battery voltage source V bat through the second diode D2. Mode two: in this mode, the power flow direction is from the battery voltage source V bat to the DC bus; the output voltage V o is equivalent to connecting the load R; the first power switch S1 is always kept off, the first diode D1 and the second diode D2 are both reverse biased and in the off state; this mode includes two working stages; in the first stage, the second power switch S2 is on, the third power switch S3 is off, the battery voltage source V bat and the third capacitor C3 charge the second inductor L2, and the voltage across the second inductor L2 is charged to the second capacitor discharges to the DC bus; in the second stage, the second power switch S2 is off, the third power switch S3 is on, the second inductor L2 discharges to the DC bus until Mode three: in this mode, the power flow direction is from the DC bus to the battery voltage source V bat ; the output voltage V o port is equivalent to connecting the DC voltage source V DC ; the first power switch S1 is always kept off, and the first diode D1 and the second diode D2 are both reverse biased and in the off state; this mode includes two working stages; in the first stage, the second power switch S2 is off, the third power switch S3 is on, and the third capacitor C3 charges the second inductor L2; in the second stage, the second power switch S2 is on, the third power switch S3 is off, and the second inductor L2 discharges to the battery voltage source V bat and the third capacitor C3. Mode four: in this mode, the power flow direction is from the photovoltaic voltage source V pv and the battery voltage source V bat to the DC bus; the output voltage V o port is equivalent to connecting the load R; the first diode D1 is always forward biased and in the on state; this mode includes four working stages; in the first stage, the first power switch S1, the second power switch S2 are turned on, the third power switch S3 is turned off, the second diode D2 is reverse biased and in the off state, the photovoltaic voltage source V pv charges the first inductor L1, the battery voltage source V bat charges the second inductor L2 through the second power switch S2; in the second stage, the first power switch S1, the third power switch S3 are turned on, the second power switch S2 is turned off, the second diode D2 is reverse biased and in the off state, the photovoltaic voltage source V pv continues to charge the first inductor L1, the second inductor L2 discharges to the DC bus and the second capacitor C2; in the third stage, the third power switch S3 is turned on, the first power switch S1, the second power switch S2 are turned off, the second diode D2 is forward biased and in the on state, the first inductor L1 discharges to the battery voltage source V bat , the second inductor L2 continues to discharge to the DC bus; in the fourth stage, the second power switch S2 is turned on, the first power switch S1, the third power switch S3 are turned off, the second diode D2 is forward biased and in the on state, the battery voltage source V bat and the first inductor L1 charge the second inductor L2; Mode five: in this mode the power flow direction is from the photovoltaic voltage source V pv and the DC bus to the battery voltage source V bat ; the output voltage V o port is equivalent to connecting the DC voltage source V DC ; the first diode D1 is always forward biased and in the on state; this mode includes four operating stages; in the first stage, the first power switch S1, the third power switch S3 are on, the second power switch S2 is off, the second diode D2 is reverse biased and in the off state, the photovoltaic voltage source V pv charges the first inductor L1, the DC bus charges the second inductor L2 through the third power switch S3, in the second stage, the first power switch S1, the second power switch S2 are on, the third power switch S3 is off, the second diode D2 is reverse biased and in the off state, the photovoltaic voltage source V pv continues to charge the first inductor L1, the second inductor L2 discharges to the battery voltage source V bat ; in the third stage, the second power switch S2 is on, the first power switch S1, the third power switch S3 are off, the second diode D2 is forward biased and in the on state, the first inductor L1 discharges to the battery voltage source V bat , the second inductor L2 continues to discharge to the battery voltage source V bat ; In the fourth stage, the third power switch S3 is turned on, the first power switch S1 and the second power switch S2 are turned off, the second diode D2 is forward biased and in the conducting state, the first inductor L1 continues to charge the battery voltage source V bat discharge, the DC bus charges the second inductor L2; Mode six: in this mode, the power flow direction is from the photovoltaic voltage source V pv to the DC bus; the output voltage V o port is equivalent to connecting the load R; the first power switch S1 is always kept open; the first diode D1 is always forward biased to be in the conducting state, and the second diode D2 is always reverse biased to be in the cut-off state; this mode includes two working stages; in the first stage, the first power switch S1 and the second power switch S2 are turned on, the third power switch S3 is turned off, the photovoltaic voltage source V pv charges the first inductor L1 and the second inductor L2, in the second stage, the first power switch S1 and the third power switch S3 are turned on, the second power switch S2 is turned off, the photovoltaic voltage source V pv continues to charge the first inductor L1, and the second inductor L2 discharges to the DC bus; Mode seven: in this mode the power flow direction is from the photovoltaic voltage source V pv to the battery voltage source V bat ; the output voltage V o port is equivalent to connecting the load R; the first diode D1 is always forward biased and in the on state; this mode includes four operating stages; in the first stage, the first power switch S1, the third power switch S3 are turned on, the second power switch S2 is turned off, the second diode D2 is reverse biased and in the off state, the photovoltaic voltage source V pv charges the first inductor L1, the second capacitor C2 charges the second inductor L2, in the second stage, the first power switch S1, the second power switch S2 are turned on, the third power switch S3 is turned off, the second diode D2 is reverse biased and in the off state, the photovoltaic voltage source V pv continues to charge the first inductor L1, the second inductor L2 discharges to the battery voltage source V bat ; in the third stage, the second power switch S2 is turned on, the first power switch S1, the third power switch S3 are turned off, the second diode D2 is forward biased and in the on state, the first inductor L1 discharges to the battery voltage source V bat , the second inductor L2 continues to discharge to the battery voltage source V bat ; In the fourth stage, the third power switch S3 is turned on, the first power switch S1 and the second power switch S2 are turned off, the second diode D2 is forward biased and in the conducting state, the first inductor L1 continues to charge the battery voltage source V bat discharge, the second capacitor C2 charges the second inductor L2.

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