Isolated three-port conversion device

Abstract

The invention provides an isolation type three-port conversion device, and relates to the field of power supplies, and the isolation type three-port conversion device comprises a high-frequency isolation transformer which comprises a first winding, a second winding and a third winding; the first end of the first bridge type switch unit is connected with the first winding, and the second end of the first bridge type switch unit is connected with a first port; the first end of the second bridge type switch unit is connected with the second winding; the first end of the third bridge type switch unit is connected with the third winding; the first DC / DC converter is connected between the second end and the second port of the second bridge type switch unit; and the second DC / DC converter is connected between the second end and the third port of the third bridge type switch unit, the first port is used for connecting an energy storage battery, the second port is used for connecting a load, and the third port is used for connecting a photovoltaic battery. The power density and efficiency of the isolation type three-port conversion device can be improved, and the isolation type three-port conversion device is easy to control.

Description

Technical Field

[0001] The present application relates to the field of power supply, and in particular to an isolated three-port conversion device. Background Art

[0002] In recent years, in order to solve the energy crisis, green energy is being vigorously developed, such as solar energy as a green energy is being vigorously promoted. In addition, in order to meet the convenience of electricity use, energy storage technology is also being vigorously developed, such as energy storage batteries. Therefore, a power conversion device that can meet the energy conversion between photovoltaic cells, energy storage batteries, and loads has become a demand, which is called a three-port conversion device in the industry.

[0003] The three-port converter has become the core structure of the photovoltaic power generation system. It is obvious that it needs to process the DC power from the photovoltaic cell, the DC power from the energy storage battery and the power supply demand of the load at the same time. The three-port converter simplifies the power conversion architecture of the photovoltaic system, reduces the number of components, and reduces the complexity of system design and installation.

[0004] However, there are still many problems with the current three-port converter. For example, for non-isolated three-port converters, the power of each port is directly coupled together through the DC bus without electrical isolation, which limits its application to occasions where the voltage levels of each input port are close, such as household energy storage, that is, a combination of high-voltage energy storage battery packs, high-voltage photovoltaic cells, and high-voltage DC bus at the load end. In addition, it also requires a large-capacity DC capacitor to handle the power coupling of the three ports, resulting in space occupation and high cost. For example, for a three-port converter coupled with a low-voltage battery end, due to the low-voltage battery end having the characteristics of low voltage and high current, the low-voltage battery end needs to use additional copper or semiconductor devices to meet the application of high current.

[0005] In addition, the current three-port converter has problems such as complex control, large switching loss, and inability to achieve soft switching. Summary of the invention

[0006] According to one embodiment, the present application provides an isolated three-port conversion device, including: a high-frequency isolation transformer, including a first winding, a second winding, and a third winding; a first bridge switch unit, a first end of which is connected to the first winding, and a second end of which is connected to the first port; a second bridge switch unit, a first end of which is connected to the second winding; a third bridge switch unit, a first end of which is connected to the third winding; a first DC / DC converter, connected between the second end and the second port of the second bridge switch unit; a second DC / DC converter, connected between the second end and the third port of the third bridge switch unit, wherein the first port is used to connect to an energy storage battery, the second port is used to connect to a load, and the third port is used to connect to a photovoltaic cell.

[0007] Furthermore, the first DC / DC converter is a Buck / Boost converter, wherein the low voltage DC end of the Buck / Boost converter is connected to the second end of the second bridge switch unit, and the high voltage DC end of the Buck / Boost converter is connected to the second port.

[0008] Furthermore, the second DC / DC converter is a Boost converter, wherein the low-voltage DC end of the Boost converter is connected to the third port, and the high-voltage DC end of the Boost converter is connected to the second end of the third bridge switch unit.

[0009] Furthermore, the first bridge switch unit, the second bridge switch unit, and the third bridge switch unit may be full-bridge switch units or half-bridge switch units.

[0010] Furthermore, the first bridge switch unit, the second bridge switch unit, and the third bridge switch unit operate in an open-loop control mode.

[0011] Furthermore, the switch control signals of the switch tubes in the switch units working in the first bridge switch unit, the second bridge switch unit, and the third bridge switch unit have the same frequency, the same phase, and the same duty cycle.

[0012] Furthermore, the switch control signals of the switch tubes in the first bridge switch unit, the second bridge switch unit, and the third bridge switch unit are fixed frequency and fixed duty cycle.

[0013] Furthermore, the first DC / DC converter and the second DC / DC converter operate in a closed-loop control mode.

[0014] Furthermore, it also includes a controller, which obtains a first sampling signal, a second sampling signal, and a third sampling signal reflecting the states of the first port, the second port, and the third port, and controls the first DC / DC converter and the second DC / DC converter according to the first sampling signal, the second sampling signal, and the third sampling signal.

[0015] Furthermore, the controller controls the first DC / DC converter and the second DC / DC converter so that the isolated three-port conversion device operates in a two-port mode or a three-port mode. Wherein, in the two-port mode, energy flows between two of the first port, the second port, and the third port; in the three-port mode, energy flows between three of the first port, the second port, and the third port.

[0016] Furthermore, the two-port mode includes: a first two-port mode, wherein the controller controls the second DC / DC converter to work and the first DC / DC converter not to work, wherein the second DC / DC converter works to boost the DC power provided by the photovoltaic cell into a first DC power outputted from its output end, and the first DC power charges the energy storage battery via the third bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit; In the second two-port mode, the controller controls the second DC / DC converter and the first DC / DC converter to operate, wherein the second DC / DC converter operates to boost the DC power provided by the photovoltaic cell into a first DC power outputted from its output end, and the first DC power is converted by the third bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter to supply power to the load; In a third two-port mode, the controller controls the first DC / DC converter to operate and the second DC / DC converter not to operate, wherein the energy provided by the energy storage battery is converted by the first bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter to power the load; or the energy provided by the load connected to the second port is converted by the first DC / DC converter, the second bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit to charge the energy storage battery.

[0017] Furthermore, a first switch unit is connected between the first DC / DC converter and the second port, and in the first two-port mode, the first switch unit is controlled to be turned off.

[0018] Furthermore, the load includes a switch conversion unit, and in the first two-port mode, the switch conversion unit is controlled not to work.

[0019] Furthermore, in the second two-port mode, the second DC / DC converter is controlled so that the first DC voltage V outputted by the second DC / DC converter is pv-boost Satisfaction: V pv-boost / (Nt / NS) <V bat , where Nt / NS is the turns ratio between the third winding and the first winding, V bat is the voltage on the energy storage battery.

[0020] Furthermore, the three-port mode includes: In a first three-port mode, the controller controls the second DC / DC converter and the first DC / DC converter to operate, wherein the second DC / DC converter operates to boost the DC power provided by the photovoltaic cell into a first DC power outputted from its output end, the first DC power charges the energy storage battery via the third bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit, and the first DC power is converted by the third bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter to supply power to the load; The second three-port mode, the controller controls the second DC / DC converter and the first DC / DC converter to work, wherein the second DC / DC converter works to boost the DC power provided by the photovoltaic cell into the first DC power outputted from its output end, and the first DC power is used to charge the energy storage battery via the third bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit; wherein the energy provided by the energy storage battery is used to power the load via the first bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter, or the energy provided by the load connected to the second port is used to charge the energy storage battery via the first DC / DC converter, the second bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit; In a third three-port mode, the controller controls the second DC / DC converter and the first DC / DC converter to operate, wherein the second DC / DC converter operates to boost the DC power provided by the photovoltaic cell into the first DC power outputted from its output end, and the first DC power is converted by the third bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter to supply power to the load; wherein the energy provided by the energy storage battery is converted by the first bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter to supply power to the load, or the energy provided by the load connected to the second port is converted by the first DC / DC converter, the second bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit to charge the energy storage battery.

[0021] Furthermore, the voltage at the first port is between 1V and 9V, the voltage at the second port is between 280V and 420V, and the voltage at the third port is between 15V and 110V.

[0022] The features and technical advantages of the present disclosure have been summarized quite extensively above so that the detailed description disclosed below may be better understood. Additional features and advantages of the present disclosure will be described below, which constitute the subject matter of the claims of the present disclosure. It will be appreciated by those skilled in the art that the disclosed concepts and specific embodiments may be easily used as a basis for modifying or designing other structures or processes for achieving the same purpose of the present disclosure. It will also be appreciated by those skilled in the art that such equivalent structures do not depart from the spirit and scope of the present disclosure as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description in conjunction with the accompanying drawings, in which: Figure 1 A schematic diagram of an isolated three-port conversion device according to an embodiment of the present application is shown; Figure 2 A schematic diagram of an isolated three-port conversion device according to another embodiment of the present application is shown; Figure 3 A schematic diagram showing the energy flow direction when the isolated three-port conversion device according to an embodiment of the present application works in a two-port mode; Figure 4 A schematic diagram of an isolated three-port conversion device according to another embodiment of the present application is shown; Figure 5 A schematic diagram showing the energy flow direction of an isolated three-port conversion device according to an embodiment of the present application when operating in a three-port mode is shown.

[0024] Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated.The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION

[0025] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] In one embodiment of the present application, an isolated three-port conversion device is provided. Figure 1 The isolated three-port converter provided by the present application includes: A high frequency isolation transformer T1, comprising a first winding Ns, a second winding Np, and a third winding Nt; A first bridge switch unit 110, a first end of which is connected to the first winding Ns, and a second end of which is connected to the first port d1; A second bridge switch unit 120, a first end of which is connected to the second winding Np; A third bridge switch unit 130, a first end of which is connected to the third winding Nt; A first DC / DC converter 210 is connected between the second end of the second bridge switch unit 120 and the second port d2; The second DC / DC converter 220 is connected between the second end of the third bridge switch unit 130 and the third port d3. The first port d1 is used to connect to the energy storage battery, the second port d2 is used to connect to the load, and the third port d3 is used to connect to the photovoltaic cell.

[0027] As mentioned above, by using a high-frequency isolation transformer T1 including three windings, electrical isolation of the three ports is achieved, that is, a fully isolated three-port conversion device, which can make the control method more flexible. Due to the characteristics of complete isolation of the three ports, the three-port voltage can be arbitrarily configured by adjusting the transformer ratio, and the combination of the three-port voltage levels is also more flexible. In addition, by connecting a DC / DC converter to the second port d2 and the third port d3, further voltage conversion and voltage stabilization can be achieved to meet the control requirements for power transmission between different ports.

[0028] In an actual implementation, the first DC / DC converter 210 is a non-isolated DC / DC converter, such as Figure 1 The figure shows a Buck / Boost converter, wherein the low voltage DC end of the Buck / Boost converter is connected to the second end of the second bridge switch unit 120, and the high voltage DC end of the Buck / Boost converter is connected to the second port d2. Figure 1 As shown, the first DC / DC converter 210 is a Buck / Boost converter formed by an inductor Lbuck, a switch tube Q9 and a switch tube Q10.

[0029] In an actual implementation, the second DC / DC converter 220 is a non-isolated DC / DC converter, such as Figure 1 The Boost converter is shown in FIG. 1 , wherein the low voltage DC end of the Boost converter is connected to the third port d3, and the high voltage DC end of the Boost converter is connected to the second end of the third bridge switch unit 130. Figure 1 As shown, the second DC / DC converter 220 is a Boost converter formed by an inductor Lboost, a switch tube Q11 and a switch tube Q12.

[0030] In one embodiment, the first bridge switch unit 110, the second bridge switch unit 120, and the third bridge switch unit 130 may be full-bridge switch units, half-bridge switch units, or multi-level switch units. The present application does not limit the specific structure of the bridge switch unit. Figure 1 As shown, the first bridge switch unit 110 is a full-bridge switch unit formed by switch tubes Q1 to Q4, the second bridge switch unit 120 is a half-bridge switch unit formed by capacitor Crp1, capacitor Crp2, switch tube Q5 and switch tube Q6, and the third bridge switch unit 130 is a half-bridge switch unit formed by capacitor Crp3, capacitor Crp4, switch tube Q7 and switch tube Q8.

[0031] In a specific embodiment, if Figure 1 As shown, the switch tube Q1 and the switch tube Q2 are connected in series to form the first bridge arm of the first bridge switch unit 110, the switch tube Q3 and the switch tube Q4 are connected in series to form the second bridge arm of the first bridge switch unit 110, the first bridge arm and the second bridge arm are connected in parallel, and the two ends of the parallel first bridge arm and the second bridge arm form the second end of the first bridge switch unit 110, and the common node of the first bridge arm and the common node of the second bridge arm form the first end of the first bridge switch unit 110. Figure 1 As shown, capacitor Crp1 and capacitor Crp2 are connected in series to form a capacitor bridge arm of the second bridge switch unit 120, switch tube Q5 and switch tube Q6 are connected in series to form a switch bridge arm of the second bridge switch unit 120, the capacitor bridge arm and the switch bridge arm are connected in parallel, the parallel capacitor bridge arm and the two ends of the switch bridge arm form the second end of the second bridge switch unit 120, and the common node of the capacitor bridge arm and the common node of the switch bridge arm form the first end of the second bridge switch unit 120. Figure 1 As shown, the first end of the inductor Lbuck in the Buck / Boost converter is connected to the terminal with a higher voltage among the second ends of the second bridge switch unit 120, the switch tube Q9 and the switch tube Q10 are connected in series, the second end of the inductor Lbuck is connected to the common node of the switch tube Q9 and the switch tube Q10, and the two ends of the branch formed by the series connection of the switch tube Q9 and the switch tube Q10 are connected to the second port d2. Figure 1 As shown, capacitor Crp3 and capacitor Crp4 are connected in series to form a capacitor bridge arm of the second bridge switch unit 120, switch tube Q7 and switch tube Q8 are connected in series to form a switch bridge arm of the third bridge switch unit 130, the capacitor bridge arm and the switch bridge arm are connected in parallel, the parallel capacitor bridge arm and the two ends of the switch bridge arm form the second end of the third bridge switch unit 130, and the common node of the capacitor bridge arm and the common node of the switch bridge arm form the first end of the third bridge switch unit 130. Figure 1As shown, the switch tube Q11 and the switch tube Q12 in the Boost converter are connected in series and then connected in parallel to the second end of the third bridge switch unit 130, the first end of the inductor Lboost is connected to the common node of the switch tube Q11 and the switch tube Q12, and the second end of the inductor Lboost and the terminal with a lower voltage in the second end of the third bridge switch unit 130 are connected to the third port d3.

[0032] In actual implementation, the first bridge switch unit 110, the second bridge switch unit 120, and the third bridge switch unit 130 work in an open-loop control mode, that is, the control signal of the switch tube therein is not affected by any feedback signal. Then the voltage of the second end of the first bridge switch unit 110, the second end of the second bridge switch unit 120, and the second end of the third bridge switch unit 130 only changes according to the turn ratio of the high-frequency isolation transformer T1, that is, when the voltage of any one of them is known, the voltage of the other two ends can be calculated only according to the turn ratio of the high-frequency isolation transformer T1. In this way, the power coupling of the three ports adopts the transformer high-frequency coupling method and the open-loop coupling method, which can greatly improve its response speed.

[0033] Furthermore, the switch control signals of the switch tubes in the switch units working in the first bridge switch unit 110, the second bridge switch unit 120, and the third bridge switch unit 130 have the same frequency, phase, and duty cycle. The open loop, same frequency, phase, and duty cycle are adopted, and the drive control is further performed in a fixed frequency and duty cycle manner, which improves the stability of software control, greatly simplifies the control difficulty of the software, and can also ensure that the isolated three-port converter can be in ZVS regardless of the working voltage, reduce switching losses, and further improve conversion efficiency.

[0034] Furthermore, the first DC / DC converter 210 and the second DC / DC converter 220 operate in a closed-loop control mode. Thus, although the first bridge switch unit 110, the second bridge switch unit 120, and the third bridge switch unit 130 operate in an open-loop control mode, the voltage of the second end of the second bridge switch unit 120 and the second port d2 can be stably controlled by the closed-loop control of the first DC / DC converter 210, and the voltage of the second end of the third bridge switch unit 130 (or the high-voltage DC end of the second DC / DC converter 220) can be stably controlled by the closed-loop control of the second DC / DC converter 220, so that the entire isolated three-port conversion device still operates in a closed-loop control mode. And it can be realized by only controlling the first DC / DC converter 210 and the second DC / DC converter 220, without involving complex three-port phase shift / phase-offset control, which greatly simplifies the control and greatly reduces the difficulty of software design and maintenance.

[0035] For actual implementation, see Figure 2 Schematic diagram of an isolated three-port converter according to another embodiment of the present application is shown, the isolated three-port converter further includes a controller 300, the controller 300 obtains a first sampling signal Sd1, a second sampling signal Sd2, and a third sampling signal Sd3 reflecting the states of the first port d1, the second port d2, and the third port d3, and controls the first DC / DC converter 210 and the second DC / DC converter 220 according to the first sampling signal Sd1, the second sampling signal Sd2, and the third sampling signal Sd3. Figure 2 As described above, the control signal Dr1 for controlling the first DC / DC converter 210 and the control signal Dr2 for controlling the second DC / DC converter 220 are outputted, so that the closed-loop control of the first DC / DC converter 210 and the second DC / DC converter 220 is realized.

[0036] Specifically, the controller 300 performs closed-loop control on the first DC / DC converter 210 and the second DC / DC converter 220 according to the first sampling signal Sd1, the second sampling signal Sd2, and the third sampling signal Sd3 to adjust their input and output voltages, so as to control the energy flow between the three ports of the isolated three-port conversion device. Specifically, the controller 300 controls the first DC / DC converter 210 and the second DC / DC converter 220 to enable the isolated three-port conversion device to operate in a two-port mode or a three-port mode. In the two-port mode, energy flows between two of the first port d1, the second port d2, and the third port d3; in the three-port mode, energy flows between three of the first port d1, the second port d2, and the third port d3.

[0037] See also Figure 3The schematic diagram of the energy flow direction of the isolated three-port conversion device of one embodiment of the present application when working in the two-port mode is shown. In actual implementation, the first port d1 is used to connect the energy storage battery, which can be marked as BAT-DC. The third port d3 is used to connect the photovoltaic cell, which can be marked as PV-DC. The second port d2 is used to connect the load, such as the power grid. For the present application, the second port d2 is a high-voltage DC bus terminal, which can be marked as HVBUS-DC. In actual implementation, a switch conversion unit (such as an inverter) can be connected after the second port d2 to feed power to the power grid, or to take power from the power grid. The circuit after the second port d2 is collectively referred to as a load for the present application. (a) is the first two-port mode, and the photovoltaic cell PV-DC connected to the third port d3 charges the energy storage battery BAT-DC connected to the first port d1. (b) is the second two-port mode, and the photovoltaic cell PV-DC connected to the third port d3 supplies power to the load HVBUS-DC connected to the second port d2. (c) is the third two-port mode, the energy storage battery BAT-DC connected to the first port d1 supplies power to the load HVBUS-DC connected to the second port d2, or the load HVBUS-DC connected to the second port d2 charges the energy storage battery BAT-DC connected to the first port d1.

[0038] Specifically, when the controller 300 determines that there is no electric signal at the second port d2 according to the first sampling signal Sd1, the second sampling signal Sd2, and the third sampling signal Sd3, that is, it cannot be used as a power source or a power-consuming load, the third port d3 is connected to a photovoltaic cell, and the energy storage battery at the first port d1 is in a power-deficient state, the controller 300 controls the second DC / DC converter 220 to work and the first DC / DC converter 210 not to work, wherein the second DC / DC converter 220 works to boost the DC power provided by the photovoltaic cell into the first DC power outputted from its output end, and the first DC power charges the energy storage battery via the third bridge switch unit 130, the high-frequency isolation transformer T1, and the first bridge switch unit 110, that is, it works in the first two-port mode. The photovoltaic cell connected to the third port d3 charges the energy storage battery connected to the first port d1. At this time, the switch tube in the second bridge switch unit 120 has no driving signal, so the second bridge switch unit 120 does not work, and the first bridge switch unit 110 and the third bridge switch unit 130 are working switch units.

[0039] Similarly, in the second two-port mode, the controller 300 controls the second DC / DC converter 220 and the first DC / DC converter 210 to work, wherein the second DC / DC converter 220 works to boost the DC power provided by the photovoltaic cell into the first DC power outputted from its output end, and the first DC power is converted to power the load through the third bridge switch unit 130, the high-frequency isolation transformer T1, the second bridge switch unit 120, and the first DC / DC converter 210. The photovoltaic cell connected to the third port d3 supplies power to the load connected to the second port d2. At this time, if there is no driving signal for the switch tube in the first bridge switch unit 110, the first bridge switch unit 110 does not work, and the second bridge switch unit 120 and the third bridge switch unit 130 are working switch units.

[0040] Similarly, in the third two-port mode, the controller 300 controls the first DC / DC converter 210 to work, and the second DC / DC converter 220 not to work, wherein the energy provided by the energy storage battery is converted by the first bridge switch unit 110, the high-frequency isolation transformer T1, the second bridge switch unit 120, and the first DC / DC converter 210 to supply power to the load; or the energy provided by the load connected to the second port d2 is converted by the first DC / DC converter 210, the second bridge switch unit 120, the high-frequency isolation transformer T1, and the first bridge switch unit 110 to charge the energy storage battery. That is, the energy storage battery connected to the first port d1 supplies power to the load connected to the second port d2, or the load connected to the second port d2 charges the energy storage battery connected to the first port d1. At this time, there is no driving signal for the switch tube in the third bridge switch unit 130, so the third bridge switch unit 130 does not work, and the first bridge switch unit 110 and the second bridge switch unit 120 are working switch units.

[0041] As described above, for the two-port mode, the circuits connected to two ports in the isolated three-port converter are started at the same time to achieve energy flow between the two ports.

[0042] In practical applications, for the two-port mode, it is not desirable for the port that does not participate in the energy flow to be energized, otherwise it will cause unnecessary power loss. Specifically, for the first two-port mode, it is desirable that the second port d2 is not energized. However, as described above, since the first bridge switch unit 110, the second bridge switch unit 120, and the third bridge switch unit 130 are all bridge switch units, when the third port d3 and the first port d1 are energized, due to the body diode of the bridge switch unit, the second end of the second bridge switch unit 120 that does not participate in the energy flow will also be energized. And as Figure 1 and Figure 2As shown, when the first DC / DC converter 210 is a Buck / Boost converter, since the end of the body diode of the switch tube Q9 connected to the inductor Lbuck is the anode and the end connected to the second port d2 is the cathode, the body diode of the switch tube Q9 must be turned on to make the second port d2.

[0043] To resolve this issue, see Figure 4 The schematic diagram of an isolated three-port converter according to another embodiment of the present invention is shown in FIG. Figure 2 On the basis of the isolated three-port conversion device shown, a first switch unit S1 is connected between the first DC / DC converter 210 and the second port d2, and the controller 300 also outputs a control signal Drs1 for controlling the first switch unit S1. In the first two-port mode, the first switch unit S1 is controlled to be turned off so that the second port d2 is not energized. Of course, when the second port d2 participates in the energy flow, the controller 300 controls the first switch unit S1 to be turned on.

[0044] As described above, in an actual application scenario, the load connected to the second port d2 also includes a switch conversion unit (such as an inverter). In the first two-port mode, the switch conversion unit can also be controlled not to work so that the second port d2 is not powered.

[0045] Similarly, for the second two-port mode, it is hoped that the first port d1 is not charged. However, since the port is directly connected to the energy storage battery, the port is always charged. To solve this problem, the body diode of the switch tube in the first bridge switch unit 110 can be controlled to be in a reverse cut-off state while not giving the switch tube driving signal in the first bridge switch unit 110, so that no energy flows through the first port d1. To this end, in an embodiment of the present application, in the second two-port mode, the second DC / DC converter 220 is controlled so that the first direct current V pv-boost Satisfaction: V pv-boost / (Nt / N S ) <V bat , where Nt / N S is the turns ratio between the third winding Nt and the first winding Ns, V bat is the voltage on the energy storage battery. That is, the voltage V on the energy storage battery obtained by sampling bat , the voltage on the photovoltaic panel, controls the second DC / DC converter 220 so that the first direct current V pv-boost The voltage V converted to the first port d1 according to the turns ratio of the high-frequency isolation transformer T1 pv-boost / (Nt / N S ) is less than the voltage V on the low voltage energy storage battery bat , the body diode of the switch tube in the first bridge switch unit 110 can be in a reverse cut-off state due to the reverse voltage, so that no energy flows through the first port d1.

[0046] For the third two-port mode, when the second DC / DC converter 220 is a Boost converter, since the end of the switch tube Q11 connected to the second bridge switch unit 120 is the cathode, and the end connected to the inductor Lboost is the anode, when the third port d3 is not connected to the photovoltaic cell, the Boost converter does not work, and its diode does not conduct due to reverse voltage, which naturally avoids the third port d3 from being energized.

[0047] See also Figure 5 The schematic diagram of energy flow direction when the isolated three-port converter of one embodiment of the present application works in the three-port mode is shown, wherein (a) is the first three-port mode, the photovoltaic cell PV-DC connected to the third port d3 charges the energy storage battery BAT-DC connected to the first port d1, and supplies power to the load HVBUS-DC connected to the second port d2. (b) is the second three-port mode, the photovoltaic cell PV-DC connected to the third port d3 charges the energy storage battery BAT-DC connected to the first port d1, the energy storage battery BAT-DC connected to the first port d1 supplies power to the load HVBUS-DC connected to the second port d2, or the load HVBUS-DC connected to the second port d2 charges the energy storage battery BAT-DC connected to the first port d1. Among them, (c) is the third three-port mode, the photovoltaic cell PV-DC connected to the third port d3 supplies power to the load HVBUS-DC connected to the second port d2, and the energy storage battery BAT-DC connected to the first port d1 supplies power to the load HVBUS-DC connected to the second port d2 or the load HVBUS-DC connected to the second port d2 charges the energy storage battery BAT-DC connected to the first port d1.

[0048] Specifically, when the controller 300 determines that the third port d3 is connected to a photovoltaic cell according to the first sampling signal Sd1, the second sampling signal Sd2, and the third sampling signal Sd3, the load at the second end needs to be powered, and the power provided by the photovoltaic cell is surplus after meeting the load demand and can also charge the energy storage battery at the first port d1, the controller 300 controls the second DC / DC converter 220 and the first DC / DC converter 210 to operate, wherein the second DC / DC converter 220 operates to boost the DC power provided by the photovoltaic cell into the first DC power outputted from its output end, the first DC power charges the energy storage battery via the third bridge switch unit 130, the high-frequency isolation transformer T1, and the first bridge switch unit 110, and the first DC power is converted by the third bridge switch unit 130, the high-frequency isolation transformer T1, the second bridge switch unit 120, and the first DC / DC converter 210 to power the load, that is, it operates in the first three-port mode. The photovoltaic cell connected to the third port d3 charges the energy storage battery connected to the first port d1 and supplies power to the load connected to the second port d2. At this time, the first bridge switch unit 110, the second bridge switch unit 120 and the third bridge switch unit 130 are all working switch units.

[0049] Similarly, for the second three-port mode, the controller 300 controls the second DC / DC converter 220 and the first DC / DC converter 210 to operate, wherein the second DC / DC converter 220 operates to boost the DC power provided by the photovoltaic cell into the first DC power outputted from its output end, and the first DC power is charged for the energy storage battery via the third bridge switch unit 130, the high-frequency isolation transformer T1, and the first bridge switch unit 110; the energy provided by the energy storage battery is converted by the first bridge switch unit 110, the high-frequency isolation transformer T1, the second bridge switch unit 120, and the first DC / DC converter 210 to supply power to the load, or the energy provided by the load connected to the second port d2 is converted by the first DC / DC converter 210, the second bridge switch unit 120, the high-frequency isolation transformer T1, and the first bridge switch unit 110 to charge the low-voltage energy storage battery. The photovoltaic cell connected to the third port d3 charges the energy storage battery connected to the first port d1, the energy storage battery connected to the first port d1 supplies power to the load connected to the second port d2, or the load connected to the second port d2 charges the energy storage battery connected to the first port d1. At this time, the first bridge switch unit 110, the second bridge switch unit 120 and the third bridge switch unit 130 are all working switch units.

[0050] Similarly, for the third three-port mode, the controller 300 controls the second DC / DC converter 220 and the first DC / DC converter 210 to operate, wherein the second DC / DC converter 220 operates to boost the DC power provided by the photovoltaic cell into the first DC power outputted from its output end, and the first DC power is converted by the third bridge switch unit 130, the high-frequency isolation transformer T1, the second bridge switch unit 120, and the first DC / DC converter 210 to supply power to the load; the energy provided by the energy storage battery is converted by the first bridge switch unit 110, the high-frequency isolation transformer T1, the second bridge switch unit 120, and the first DC / DC converter 210 to supply power to the load, or the energy provided by the load connected to the second port d2 is converted by the first DC / DC converter 210, the second bridge switch unit 120, the high-frequency isolation transformer T1, and the first bridge switch unit 110 to charge the energy storage battery. The photovoltaic cell connected to the third port d3 supplies power to the load connected to the second port d2, and the energy storage battery connected to the first port d1 supplies power to the load connected to the second port d2, or the load connected to the second port d2 charges the energy storage battery connected to the first port d1. At this time, the first bridge switch unit 110, the second bridge switch unit 120 and the third bridge switch unit 130 are all working switch units.

[0051] Thus, in the three-port mode, the circuits connected to the three ports of the isolated three-port converter are simultaneously started, so that energy flows between the first port d1 , the second port d2 , and the third port d3 .

[0052] Because the energy transfer of the three ports is all through the high-frequency isolation transformer T1, the isolated three-port conversion device provided by the present application is more advantageous under the condition that the voltage difference of the three ports is relatively large. In one embodiment, the energy storage battery connected to the first port d1 is a low-voltage energy storage battery, such as the voltage at the first port d1 is between 1V and 9V; the second port d2 is connected to the high-voltage DC bus as described above, such as the voltage at the second port d2 is between 280V and 420V; the third port d3 is connected to the photovoltaic cell, such as the voltage at the third port d3 is between 15V and 110V.

[0053] If the energy storage battery connected to the first port d1 is a low-voltage energy storage battery, a single / double string of cells can be selected to meet the demand, which can complete all the work in a very simple way, greatly improving the economy of the system design. Because in practical applications, for the currently widely used lithium batteries, due to the characteristics of lithium batteries, string battery packs need to use a dedicated BMS board for the voltage, current, and temperature collection of the battery cells, as well as to provide battery balancing to ensure that the battery cells work in a safe and stable area; the more battery strings there are, the more chips, MOS, collection wires and other materials are needed. However, this application can meet the demand by selecting a single / double string of cells, so all the work can be completed in a very simple way, greatly improving the economy of the system design.

[0054] In addition, the isolated three-port converter is used in low-voltage scenarios such as single / dual cells. Since there is no need for power coupling at the low-voltage end, a large amount of busbar materials, semiconductor materials and heat dissipation materials are saved, which greatly improves the economy of the converter design and significantly improves the power density.

[0055] In practical applications, the third port d3 connected to the photovoltaic cell is only used as an input source. From the above description, it can be seen that the isolated three-port conversion device provided by the present application takes into account the comprehensive conversion efficiency of photovoltaic-battery and photovoltaic-grid, effectively reduces the use of heat dissipation components, and improves the utilization rate of photovoltaic power.

[0056] In addition, the third port d3 is only used as an input source, and the first port d1 and the second port d2 can be used as both an input source and a load. When the above-mentioned isolated three-port conversion device is applied to a portable power supply, the energy storage battery connected to the first port d1 is the internal battery of the portable power supply, and the third port d3 is only used as an input source. For the user, the portable power supply has only one energy input / output port, that is, the second port d2. For the user, the portable power supply is only a power source, and its power can be freely adjusted whether it is used as an input source or an output source.

[0057] In addition, the isolated three-port converter has the characteristic of complete isolation of the three ports, which can reduce the crosstalk of each port and is safer in the low-voltage power environment.

[0058] Furthermore, if Figure 1 , Figure 2 and Figure 4 As shown, capacitors are connected to the first port d1, the second port d2, the third port d3, the output end of the second DC / DC converter 220 (i.e., the end connected to the third bridge switch unit 130), and the end of the first DC / DC converter 210 connected to the second bridge switch unit 120 to achieve voltage stabilization and filtering.

[0059] Although the embodiments of the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims.

[0060] In addition, the scope of the present application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, material compositions, devices, methods, and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of this disclosure, processes, machines, manufactures, material compositions, means, methods, or steps that perform substantially the same functions currently exist or will later be developed or achieve substantially the same results as the corresponding embodiments described herein that can be used according to this disclosure. Therefore, the appended claims are intended to include such processes, machines, manufactures, material compositions, devices, methods, or steps within their scope.

Claims

1. An isolated three-port conversion device, characterized in that: include: A high frequency isolation transformer, comprising a first winding, a second winding, and a third winding; A first bridge switch unit, a first end of which is connected to the first winding, and a second end of which is connected to the first port; A second bridge switch unit, a first end of which is connected to the second winding; A third bridge switch unit, a first end of which is connected to the third winding; A first DC / DC converter connected between the second end and the second port of the second bridge switch unit; A second DC / DC converter is connected between the second end and the third port of the third bridge switch unit. The first port is used to connect to an energy storage battery, the second port is used to connect to a load, and the third port is used to connect to a photovoltaic cell.

2. The isolated three-port converter according to claim 1, characterized in that: The first DC / DC converter is a Buck / Boost converter, wherein a low-voltage DC end of the Buck / Boost converter is connected to the second end of the second bridge switch unit, and a high-voltage DC end of the Buck / Boost converter is connected to the second port.

3. The isolated three-port converter according to claim 2, characterized in that: The second DC / DC converter is a Boost converter, wherein a low-voltage DC end of the Boost converter is connected to the third port, and a high-voltage DC end of the Boost converter is connected to the second end of the third bridge switch unit.

4. The isolated three-port converter according to any one of claims 1 to 3, characterized in that: The first bridge switch unit, the second bridge switch unit, and the third bridge switch unit operate in an open-loop control mode.

5. The isolated three-port converter according to claim 4, characterized in that: The switch control signals of the switch tubes in the switch units working in the first bridge switch unit, the second bridge switch unit, and the third bridge switch unit have the same frequency, the same phase, and the same duty cycle.

6. The isolated three-port converter according to claim 4, characterized in that: The first DC / DC converter and the second DC / DC converter operate in a closed-loop control mode.

7. The isolated three-port converter according to claim 6, characterized in that: It also includes a controller, which obtains a first sampling signal, a second sampling signal, and a third sampling signal reflecting the states of the first port, the second port, and the third port, and controls the first DC / DC converter and the second DC / DC converter according to the first sampling signal, the second sampling signal, and the third sampling signal.

8. The isolated three-port converter according to claim 7, characterized in that: The controller controls the first DC / DC converter and the second DC / DC converter so that the isolated three-port conversion device operates in a two-port mode or a three-port mode. Wherein, in the two-port mode, energy flows between two of the first port, the second port, and the third port; in the three-port mode, energy flows between three of the first port, the second port, and the third port.

9. The isolated three-port converter according to claim 8, characterized in that: The two-port mode includes: a first two-port mode, wherein the controller controls the second DC / DC converter to work and the first DC / DC converter not to work, wherein the second DC / DC converter works to boost the DC power provided by the photovoltaic cell into a first DC power outputted from its output end, and the first DC power charges the energy storage battery via the third bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit; In the second two-port mode, the controller controls the second DC / DC converter and the first DC / DC converter to operate, wherein the second DC / DC converter operates to boost the DC power provided by the photovoltaic cell into a first DC power outputted from its output end, and the first DC power is converted by the third bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter to supply power to the load; In a third two-port mode, the controller controls the first DC / DC converter to operate and the second DC / DC converter not to operate, wherein the energy provided by the energy storage battery is converted by the first bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter to power the load; or the energy provided by the load connected to the second port is converted by the first DC / DC converter, the second bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit to charge the energy storage battery.

10. The isolated three-port converter according to claim 9, characterized in that: A first switch unit is connected between the first DC / DC converter and the second port. In the first two-port mode, the first switch unit is controlled to be turned off.

11. The isolated three-port converter according to claim 9, characterized in that: The load includes a switch conversion unit, and in the first two-port mode, the switch conversion unit is controlled not to work.

12. The isolated three-port converter according to claim 9, characterized in that: In the second two-port mode, the second DC / DC converter is controlled so that the first DC voltage V outputted by the second DC / DC converter is pv-boost Satisfaction: V pv-boost / (Nt / NS) <V bat , where Nt / NS is the turns ratio between the third winding and the first winding, V bat is the voltage on the energy storage battery.

13. The isolated three-port converter according to claim 8, characterized in that: The three-port mode includes: In a first three-port mode, the controller controls the second DC / DC converter and the first DC / DC converter to operate, wherein the second DC / DC converter operates to boost the DC power provided by the photovoltaic cell into a first DC power outputted from its output end, the first DC power charges the energy storage battery via the third bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit, and the first DC power is converted by the third bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter to supply power to the load; The second three-port mode, the controller controls the second DC / DC converter and the first DC / DC converter to work, wherein the second DC / DC converter works to boost the DC power provided by the photovoltaic cell into the first DC power outputted from its output end, and the first DC power is used to charge the energy storage battery via the third bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit; wherein the energy provided by the energy storage battery is used to power the load via the first bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter, or the energy provided by the load connected to the second port is used to charge the energy storage battery via the first DC / DC converter, the second bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit; In a third three-port mode, the controller controls the second DC / DC converter and the first DC / DC converter to operate, wherein the second DC / DC converter operates to boost the DC power provided by the photovoltaic cell into the first DC power outputted from its output end, and the first DC power is converted by the third bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter to supply power to the load; wherein the energy provided by the energy storage battery is converted by the first bridge switch unit, the high-frequency isolation transformer, the second bridge switch unit, and the first DC / DC converter to supply power to the load, or the energy provided by the load connected to the second port is converted by the first DC / DC converter, the second bridge switch unit, the high-frequency isolation transformer, and the first bridge switch unit to charge the energy storage battery.

14. The isolated three-port converter according to claim 1, characterized in that: The voltage at the first port is between 1V and 9V, the voltage at the second port is between 280V and 420V, and the voltage at the third port is between 15V and 110V.

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