Partially isolated three-port resonant DC converter and control method thereof

Abstract

The invention provides a partially isolated three-port resonant direct-current converter and a control method thereof, which are applied to a photovoltaic energy storage system, a photovoltaic port is a two-phase interleaved boost circuit, and the first input end of the boost circuit is connected with the output end of a photovoltaic module in the photovoltaic energy storage system; the battery port is a second input end of the two-phase interleaved boost circuit and an input end of the resonance circuit, and is connected with a battery in the photovoltaic energy storage system; the load port is an output end of the resonance circuit and is connected with a load in the photovoltaic energy storage system; the two-phase interlaced boost circuit and the resonant circuit are integrated into a single-stage structure through multiplexing of a switch bridge arm, and magnetic integration is realized through a coupling inductor, so that the number of devices is reduced, and the power density of the device is improved; the maximum power of the photovoltaic module is tracked or charging and discharging of the battery are controlled by adjusting the duty ratio of the first switch bridge arm, the output voltage of the load is controlled by adjusting the duty ratio of the third switch bridge arm, and independent port control and wide voltage gain are achieved under the fixed switch frequency.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a partially isolated three-port resonant DC converter and a control method thereof. Background Art

[0002] In recent years, with the increasing prominence of energy and environmental issues, clean energy represented by solar energy has developed rapidly. However, solar energy is affected by the environment, and its output has disadvantages such as volatility and indirectness, which is not conducive to the stable operation of the power grid. Therefore, combining photovoltaic power generation with energy storage technology to build an integrated photovoltaic storage system is conducive to improving the flexibility and controllability of photovoltaic power generation. Under the traditional architecture, multiple two-port converters are used to connect photovoltaic modules, batteries and loads in the photovoltaic storage system, but this solution has the problems of a large number of devices and low energy conversion efficiency. The three-port converter can realize power transmission between three ports in a single-stage structure, which can effectively improve the energy conversion efficiency. However, many existing resonant three-port converters based on frequency modulation still have the problem that the voltage gain range is limited by the switching frequency range and the number of magnetic components is large. Summary of the invention

[0003] The present invention provides a partially isolated three-port resonant DC converter and a control method thereof, the purpose of which is to improve the power density of the converter and achieve efficient energy conversion under a wide voltage gain.

[0004] In order to achieve the above object, the present invention provides a partially isolated three-port resonant DC converter, which is applied to a photovoltaic energy storage system, comprising: A photovoltaic port, a battery port, a load port, a first coupled inductor, a second coupled inductor, a third switch bridge arm, a two-phase interleaved boost circuit and a resonant circuit; The two-phase interleaved boost circuit and the resonant circuit reuse the first switch bridge arm, the second switch bridge arm, and the second filter capacitor; The first end of the first switch bridge arm, the first end of the second switch bridge arm, and the positive electrode of the second filter capacitor are all connected to the positive electrode of the battery port, and the second end of the first switch bridge arm, the second end of the second switch bridge arm, the negative electrode of the second filter capacitor, the negative electrode of the photovoltaic port, the first end of the first coupled inductor, and the positive electrode of the photovoltaic port are all connected to the negative electrode of the battery port; The second end of the first coupled inductor is respectively connected to the third end of the first switch bridge arm and the first end of the second coupled inductor; The third end of the first coupled inductor is connected to the third end of the second switch bridge arm and the second end of the second coupled inductor respectively; The third end of the second coupled inductor is connected to the third end of the third switch bridge arm, and the first end of the third switch bridge arm is connected to the positive electrode of the load port; The fourth end of the second coupled inductor is connected to the second end of the third switch bridge arm and the negative electrode of the load port respectively; The photovoltaic port is connected to the output end of the photovoltaic module in the photovoltaic energy storage system as the first input end of the two-phase interleaved boost circuit; The battery port serves as the second input terminal of the two-phase interleaved boost circuit and the input terminal of the resonant circuit, and is connected to the output terminal of the battery in the photovoltaic energy storage system; The load port is connected to the input end of the load in the photovoltaic energy storage system as the output end of the resonant circuit.

[0005] Furthermore, the two-phase interleaved boost circuit also includes: A first filter capacitor; The positive electrode of the first filter capacitor is connected to the positive electrode of the photovoltaic port and the first end of the first coupling inductor respectively; The negative electrode of the first filter capacitor is connected to the negative electrode of the photovoltaic port.

[0006] More specifically, the resonant circuit includes: A third filter capacitor, a fourth filter capacitor, and a resonant capacitor; The positive electrode of the third filter capacitor is connected to the first end of the third switch bridge arm and the positive electrode of the load port respectively; The negative electrode of the third filter capacitor is connected to the fourth end of the second coupling inductor and the positive electrode of the fourth filter capacitor respectively; The negative electrode of the fourth filter capacitor is connected to the second end of the third switch bridge arm and the negative electrode of the load port respectively; The third end of the third switch bridge arm is connected to the third end of the second coupled inductor; The first end of the second coupled inductor is connected to the third end of the first switch bridge arm through the resonant capacitor; The second end of the second coupled inductor is connected to the third end of the second switch bridge arm.

[0007] Further, the voltage between the midpoint of the first switch bridge arm and the midpoint of the second switch bridge arm is the midpoint voltage of the switch bridge arm on the photovoltaic port side; The voltage between the midpoint of the third switch bridge arm and the negative electrode of the third filter capacitor is the midpoint voltage of the switch bridge arm on the output port side.

[0008] Further, the first switch bridge arm includes a first switch tube and a second switch tube; The drain of the first switch tube is respectively connected to the positive electrode of the second filter capacitor, the positive electrode of the battery port, and the first end of the second switch bridge arm; The source of the first switch tube is respectively connected to the second end of the first coupling inductor, the first end of the resonant inductor, and the drain of the second switch tube; The source of the second switch tube is respectively connected to the negative electrode of the second filter capacitor, the negative electrode of the first filter capacitor, and the second end of the second switch bridge arm.

[0009] Furthermore, the second switch bridge arm includes a third switch tube and a fourth switch tube; The drain of the third switch tube is connected to the drain of the first switch tube; The source of the third switch tube is connected to the drain of the fourth switch tube, the third end of the first coupling inductor, and the second end of the second coupling inductor; The source of the fourth switch tube is connected to the source of the second switch tube.

[0010] Further, the third switch bridge arm includes a fifth switch tube and a sixth switch tube; The source of the fifth switch tube is connected to the third end of the second coupled inductor and the drain of the sixth switch tube respectively; The drain of the fifth switch tube is connected to the positive electrode of the third filter capacitor and the positive electrode of the load port respectively; The drain of the sixth switch tube is connected to the negative electrode of the fourth filter capacitor and the negative electrode of the load port respectively.

[0011] Further, the duty cycle of the first switch tube is used to control the photovoltaic module to track the maximum power and the battery to charge and discharge; The duty cycle of the fifth switch tube is used to control the voltage of the output port.

[0012] Further, the partially isolated three-port resonant DC converter includes three power transmission modes; In the first power transmission mode, the power input by the PV panel is greater than the power required by the load, and the excess PV energy is transmitted to the battery to charge the battery; In the second power transmission mode, the power input by the photovoltaic module is less than the power required by the load, and the battery is controlled to discharge to the load to power the load; In the third power transmission mode, the load is powered solely by PV panels or batteries.

[0013] The present invention also includes a control method for a partially isolated three-port resonant DC converter, which is applied to the partially isolated three-port resonant DC converter. The control method includes: By adjusting the duty cycle of the switch tube on the first switch bridge arm, the maximum power of the photovoltaic module in the photovoltaic energy storage system is tracked or the charging and discharging of the battery in the photovoltaic energy storage system is controlled; The output voltage of the load in the photovoltaic energy storage system is controlled by adjusting the duty cycle of the switch tube on the third switch bridge arm; By controlling the phase shift angle between the switch tube on the first switch bridge arm and the switch tube on the third switch bridge arm, the bridge arm midpoint voltage waveform on the photovoltaic port side and the bridge arm midpoint voltage waveform on the load port side are made symmetrical.

[0014] The above scheme of the present invention has the following beneficial effects: The present invention is applied to a photovoltaic energy storage system, comprising a photovoltaic port, a battery port, a load port, a first coupled inductor, a second coupled inductor, a third switch bridge arm, a two-phase interleaved boost circuit and a resonant circuit; the photovoltaic port is connected to the output end of a photovoltaic module in the photovoltaic energy storage system as the first input end of the two-phase interleaved boost circuit; the battery port is connected to the output end of a battery in the photovoltaic energy storage system as the second input end of the two-phase interleaved boost circuit and the input end of the resonant circuit; the load port is connected to the input end of a load in the photovoltaic energy storage system as the output end of the resonant circuit; compared with the prior art, the two-phase interleaved boost circuit and the resonant circuit in the present invention are integrated into a single-stage structure through switch bridge arm reuse, and magnetic integration is achieved through the first coupled inductor and the second coupled inductor, thereby reducing the number of devices and improving the power density of the device; by adjusting the duty cycle of the switch tube on the first switch bridge arm to track the maximum power of the photovoltaic module or control the charging and discharging of the battery, and by adjusting the duty cycle of the switch tube on the third switch bridge arm to control the output voltage of the load, port independent control and wide voltage gain can be achieved at a fixed switching frequency.

[0015] Other beneficial effects of the present invention will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A topological structure diagram of an embodiment of the present invention; Figure 2 2 is a working waveform diagram of the converter in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0019] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a locking connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0020] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] In view of the existing problems, the present invention provides a partially isolated three-port resonant DC converter and a control method thereof.

[0022] like Figure 1 As shown, an embodiment of the present invention provides a partially isolated three-port resonant DC converter, which is applied to a photovoltaic energy storage system, including: Photovoltaic port U pv 、Battery port U B 、Load port U o , a second coupled inductor, a third switch bridge arm, a two-phase interleaved boost circuit, a resonant circuit, and a first coupled inductor for storing energy for the two-phase interleaved boost circuit; The two-phase interleaved boost circuit and the resonant circuit reuse the first switch bridge arm, the second switch bridge arm, and the second filter capacitor C2; The first end of the first switch bridge arm, the first end of the second switch bridge arm, and the positive electrode of the second filter capacitor C2 are all connected to the battery port U B The positive electrode of the first switch bridge arm, the second end of the second switch bridge arm, the negative electrode of the second filter capacitor C2, and the photovoltaic port U pv The negative electrode, the first end of the first coupled inductor, the photovoltaic port U pv The positive pole of the battery is connected to the U B The negative connection of The second end of the first coupled inductor is respectively connected to the third end of the first switch bridge arm and the first end of the second coupled inductor; The third end of the first coupled inductor is connected to the third end of the second switch bridge arm and the second end of the second coupled inductor respectively; The third end of the second coupled inductor is connected to the third end of the third switch bridge arm, and the first end of the third switch bridge arm is connected to the load port U o The positive connection of The fourth end of the second coupled inductor is respectively connected to the second end of the third switch bridge arm and the load port U o The negative connection of Photovoltaic port U pv As a first input terminal of a two-phase interleaved boost circuit connected to an output terminal of a photovoltaic module in a photovoltaic energy storage system; Battery port U B As the second input terminal of the two-phase interleaved boost circuit and the input terminal of the resonant circuit, connected to the output terminal of the battery in the photovoltaic energy storage system; The load port Uo is connected to the input end of the load in the photovoltaic energy storage system as the output end of the resonant circuit.

[0023] It should be noted that the two-phase interleaved Boost circuit and the resonant circuit are integrated into a single-stage partially isolated three-port resonant DC converter by reusing the first switch bridge arm and the second switch bridge arm and the second filter capacitor C2.

[0024] In the embodiment of the present invention, the first coupled inductor is a negatively coupled coupled inductor integrated with two DC inductors, which is helpful to reduce the current ripple of the photovoltaic port.

[0025] Most preferably, the two-phase interleaved boost circuit further comprises: A first filter capacitor C1; The positive electrode of the first filter capacitor C1 is connected to the photovoltaic port U pv The positive electrode and the first end of the first coupled inductor are connected; The negative electrode of the first filter capacitor C1 is connected to the photovoltaic port U pv negative connection.

[0026] Most preferably, the resonant circuit comprises: The third filter capacitor C3, the fourth filter capacitor C4, the resonant capacitor C r ; The positive electrode of the third filter capacitor C3 is connected to the first end of the third switch bridge arm and the load port U o The positive connection of The negative electrode of the third filter capacitor C3 is connected to the fourth end of the second coupling inductor and the positive electrode of the fourth filter capacitor C4 respectively; The negative electrode of the fourth filter capacitor C4 is connected to the second end of the third switch bridge arm and the load port U o The negative connection of The third end of the third switch bridge arm is connected to the third end of the second coupled inductor; The first end of the second coupled inductor is connected through the resonant capacitor C r connected to the third end of the first switch bridge arm; The second end of the second coupled inductor is connected to the third end of the second switch bridge arm.

[0027] In the embodiment of the present invention, the second coupling inductor and the resonant capacitor C r The resonant network is used to transfer power, and the second coupled inductor is used to realize the load port U in the resonant circuit. o With PV port U pv 、Battery port U B The first coupled inductor is used to realize the integrated reuse of the DC inductor of the two-phase interleaved Boost circuit, and the second coupled inductor is used to realize the integrated reuse of the resonant inductor and the transformer in the resonant circuit, which reduces the number of components in the converter while realizing low current ripple on the battery side, and is beneficial to improving the power density of the device.

[0028] In the embodiment of the present invention, the voltage between the midpoint of the first switch bridge arm and the midpoint of the second switch bridge arm is the photovoltaic port U pv The midpoint voltage of the switch bridge arm on the side is U AB , A is the midpoint potential of the first switch bridge arm, and B is the midpoint potential of the second switch bridge arm; The voltage between the middle point of the third switch bridge arm and the negative electrode of the third filter capacitor C3 is the load port U o The midpoint voltage of the switch bridge arm on the side is U CD , C is the midpoint potential of the third switch bridge arm, and C is the midpoint potential between the third filter capacitor and the fourth filter capacitor.

[0029] In the embodiment of the present invention, the switching frequency of the partially isolated three-port resonant DC converter is equal to the resonant frequency, and the switch tubes on the same bridge arm are complementary to each other.

[0030] Most preferably, the first switch bridge arm includes a first switch tube Q1 and a second switch tube Q2; The drain of the first switch tube Q1 is connected to the positive electrode of the second filter capacitor C2 and the battery port U B The positive electrode and the first end of the second switch bridge arm are connected; The source of the first switch tube Q1 is respectively connected to the second end of the first coupling inductor, the first end of the resonant inductor, and the drain of the second switch tube Q2; The source of the second switch tube Q2 is connected to the cathode of the second filter capacitor C2, the cathode of the first filter capacitor C1, and the second end of the second switch bridge arm respectively.

[0031] Most preferably, the second switch bridge arm includes a third switch tube Q3 and a fourth switch tube Q4; The drain of the third switch tube Q3 is connected to the drain of the first switch tube Q1; The source of the third switch tube Q3 is connected to the drain of the fourth switch tube Q4, the third end of the first coupling inductor, and the second end of the second coupling inductor; The source of the fourth switch tube Q4 is connected to the source of the second switch tube Q2.

[0032] In the embodiment of the present invention, the duty cycle of the first switch tube Q1 is the same as the duty cycle of the third switch tube Q3, and the ratio of the difference between the turn-on time of the first switch tube Q1 and the turn-on time of the third switch tube Q3 to the switching period is 0.5.

[0033] Most preferably, the third switch bridge arm includes a fifth switch tube Q5 and a sixth switch tube Q6; The source of the fifth switch tube Q5 is connected to the third end of the second coupled inductor and the drain of the sixth switch tube Q6 respectively; The drain of the fifth switch tube Q5 is connected to the positive electrode of the third filter capacitor C3 and the load port U o The positive connection of The drain of the sixth switch tube Q6 is connected to the negative electrode of the fourth filter capacitor C4 and the negative electrode of the load port Uo respectively.

[0034] It should be noted that the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4, the fifth switch tube Q5, and the sixth switch tube Q6 are all power transistors MOQFETs with anti-parallel diodes and drain-source parasitic capacitances.

[0035] In the embodiment of the present invention, two switch tubes in the same switch bridge arm are complementarily turned on; the duty cycle of the first switch tube Q1 is the same as the duty cycle of the third switch tube Q3, and the difference between the turn-on time of the first switch tube and the third switch tube accounts for 0.5 of the switching period.

[0036] Specifically, the partially isolated three-port resonant DC converter includes three power transmission modes; In the first power transmission mode, the power input by the PV panel is greater than the power required by the load, and the excess PV energy is transmitted to the battery to charge the battery; In the second power transmission mode, the power input by the photovoltaic module is less than the power required by the load, and the battery is controlled to discharge to the load to power the load; In the third power transmission mode, the load is powered by PV panels or batteries.

[0037] It should be noted that, in the embodiment of the present invention, the driving logic of the partially isolated three-port resonant DC converter in the three power transmission modes is consistent, so the working principle is the same in the three modes; by controlling the photovoltaic port U pv The switch tube on the first switch bridge arm and the load port U o The duty cycle of the switch tube on the third switch tube bridge arm on the side can realize system energy management under a wide voltage range, and the driving logic is consistent in all power transmission modes, which can achieve smooth switching between modes. The voltage gain of the converter is only related to the duty cycle and is not affected by the transmission power, which is conducive to achieving low control complexity.

[0038] The embodiment of the present invention further provides a control method for a partially isolated three-port resonant DC converter, which is applied to the partially isolated three-port resonant DC converter. The control method includes: By adjusting the duty cycle of the switch tube on the first switch bridge arm, the maximum power of the photovoltaic module in the photovoltaic energy storage system is tracked and the charging and discharging of the battery in the photovoltaic energy storage system is controlled; The output voltage of the load in the photovoltaic energy storage system is controlled by adjusting the duty cycle of the switch tube on the third switch bridge arm; By controlling the phase shift angle between the switch tube on the first switch bridge arm and the switch tube on the third switch bridge arm, the bridge arm midpoint voltage waveform on the photovoltaic port side and the bridge arm midpoint voltage waveform on the load port side are made symmetrical.

[0039] It should be noted that, under normal working conditions, the duty cycle of the first switch tube Q1 is adjusted d 1 Used to track the maximum power of the photovoltaic module; when the battery voltage or current exceeds the preset safety value, the duty cycle of the first switch tube Q1 d 1 Used to control the charging and discharging of the battery to prevent the battery from overcharging.

[0040] In the embodiment of the present invention, by controlling the phase shift angle between the switch tube on the first switch bridge arm and the switch tube on the third switch bridge arm, the photovoltaic port U pv The midpoint voltage of the side switch bridge arm and the load port U o The waveform of the midpoint voltage of the side switch bridge arm is symmetrical, so the waveform of the partially isolated three-port resonant DC converter in the first half switching cycle and the second half switching cycle is symmetrical, such as Figure 2 As shown, the working principle is similar, so the working process within half a switching cycle can be divided into 6 modes, as follows: Mode 1: At time t0, the sixth switch tube Q6 is turned off, and the junction capacitance of the fifth switch tube Q5 and the sixth switch tube Q6 is charged and discharged in the dead zone; Mode 2: At time t1, the fifth switch tube Q5 is turned on with zero voltage. In this mode, the second switch tube Q2 and the fourth switch tube Q4 remain turned on, and the photovoltaic port U pv The midpoint voltage of the switch bridge arm on the side is equal to 0, and the load port U o The waveform of the midpoint voltage of the switch bridge arm on the side is equal to , the primary current i of the first coupled inductor L1 and the secondary current i of the first coupled inductor L2 Linearly increase, the second coupling inductor and the first resonant capacitor C r resonance; Mode 3: At time t2, the second switch tube Q2 is turned off, and the junction capacitances of the two switch tubes in the first switch bridge arm are charged and discharged in the dead zone; Mode 4: At t3, the first switch tube Q1 is turned on with zero voltage, and the photovoltaic port U pv The midpoint voltage of the switch bridge arm on the side changes from 0 to equal the battery terminal voltage U B , the primary current i of the first coupled inductor L1 Linearly decrease, the resonant current i r Sinusoidal variation; Mode 5: At time t4, the first switch tube Q1 is turned off, and the junction capacitance of the first switch tube Q1 and the second switch tube Q2 in the dead zone is charged and discharged; Mode 6: At t5, the second switch tube Q2 is turned on with zero voltage, and the photovoltaic port U pv The midpoint voltage of the switch bridge arm on the side becomes 0, and the primary current i L1 Linear increase, the resonant current i r Sinusoidal variation.

[0041] Among them, the duration of mode 2 and mode 6 is equal, and the photovoltaic port U pv To battery port U B The voltage gain is: ; Photovoltaic port U pv To load port U o The gain is: ; in, It represents the duty cycle of the switch tube on the switch bridge arm at the photovoltaic port, that is, the duty cycle of the first switch tube Q1. It represents the duty cycle of the switch tube on the switch bridge arm at the output port, that is, the duty cycle of the fifth switch tube Q5.

[0042] In the embodiment of the present invention, the photovoltaic port U pv The voltage at the battery port is 30V~50V, B The voltage at the load port is 80V and the load port Uo When the voltage at the input voltage is 400V, a 600W converter prototype is built. The switch tubes of all switch networks use power transistors MOQFETs with anti-parallel diodes and drain-source parasitic capacitances. The driving signal of the main circuit is generated by TI digital signal processor TMQ320F28335. Under this experimental condition, the partially isolated three-port resonant DC converter provided in the embodiment of the present invention can operate normally under different working conditions.

[0043] The embodiment of the present invention is applied to a photovoltaic energy storage system, including a photovoltaic port, a battery port, a load port, a first coupled inductor, a second coupled inductor, a third switch bridge arm, a two-phase interleaved boost circuit and a resonant circuit; the photovoltaic port is connected to the output end of the photovoltaic module in the photovoltaic energy storage system as the first input end of the two-phase interleaved boost circuit; the battery port is connected to the output end of the battery in the photovoltaic energy storage system as the second input end of the two-phase interleaved boost circuit and the input end of the resonant circuit; the load port is connected to the input end of the load in the photovoltaic energy storage system as the output end of the resonant circuit; compared with the prior art, the two-phase interleaved boost circuit and the resonant circuit in the present invention are integrated into a single-stage structure through switch bridge arm reuse, and magnetic integration is achieved through the first coupled inductor and the second coupled inductor, thereby reducing the number of devices and improving the power density of the device; by adjusting the duty cycle of the switch tube on the first switch bridge arm to track the maximum power of the photovoltaic module or control the charging and discharging of the battery, and by adjusting the duty cycle of the switch tube on the third switch bridge arm to control the output voltage of the load, port independent control and wide voltage gain can be achieved at a fixed switching frequency.

[0044] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A partially isolated three-port resonant DC converter, characterized in that: Applied to photovoltaic energy storage systems, including: A photovoltaic port, a battery port, a load port, a first coupled inductor, a second coupled inductor, a third switch bridge arm, a two-phase interleaved boost circuit and a resonant circuit; The two-phase interleaved boost circuit and the resonant circuit reuse the first switch bridge arm, the second switch bridge arm, and the second filter capacitor; The first end of the first switch bridge arm, the first end of the second switch bridge arm, and the positive electrode of the second filter capacitor are all connected to the positive electrode of the battery port, and the second end of the first switch bridge arm, the second end of the second switch bridge arm, the negative electrode of the second filter capacitor, the negative electrode of the photovoltaic port, the first end of the first coupled inductor, and the positive electrode of the photovoltaic port are all connected to the negative electrode of the battery port; The second end of the first coupled inductor is connected to the third end of the first switch bridge arm and the first end of the second coupled inductor respectively; The third end of the first coupled inductor is connected to the third end of the second switch bridge arm and the second end of the second coupled inductor respectively; The third end of the second coupled inductor is connected to the third end of the third switch bridge arm, and the first end of the third switch bridge arm is connected to the positive electrode of the load port; The fourth end of the second coupled inductor is connected to the second end of the third switch bridge arm and the negative electrode of the load port respectively; The photovoltaic port is connected to the output end of the photovoltaic module in the photovoltaic energy storage system as the first input end of the two-phase interleaved boost circuit; The battery port serves as the second input terminal of the two-phase interleaved boost circuit and the input terminal of the resonant circuit, and is connected to the output terminal of the battery in the photovoltaic energy storage system; The load port serves as the output end of the resonant circuit and is connected to the input end of the load in the photovoltaic energy storage system.

2. The partially isolated three-port resonant DC converter according to claim 1, characterized in that: The two-phase interleaved boost circuit further includes: A first filter capacitor; The positive electrode of the first filter capacitor is connected to the positive electrode of the photovoltaic port and the first end of the first coupling inductor respectively; The negative electrode of the first filter capacitor is connected to the negative electrode of the photovoltaic port.

3. The partially isolated three-port resonant DC converter according to claim 2, characterized in that: The resonant circuit comprises: A third filter capacitor, a fourth filter capacitor, and a resonant capacitor; The positive electrode of the third filter capacitor is connected to the first end of the third switch bridge arm and the positive electrode of the load port respectively; The negative electrode of the third filter capacitor is connected to the fourth end of the second coupling inductor and the positive electrode of the fourth filter capacitor respectively; The negative electrode of the fourth filter capacitor is connected to the second end of the third switch bridge arm and the negative electrode of the load port respectively; The third end of the third switch bridge arm is connected to the third end of the second coupled inductor; The first end of the second coupled inductor is connected to the third end of the first switch bridge arm through the resonant capacitor; The second end of the second coupled inductor is connected to the third end of the second switch bridge arm.

4. The partially isolated three-port resonant DC converter according to claim 3, characterized in that: The voltage between the midpoint of the first switch bridge arm and the midpoint of the second switch bridge arm is the midpoint voltage of the switch bridge arm on the photovoltaic port side; The voltage between the midpoint of the third switch bridge arm and the negative electrode of the third filter capacitor is the midpoint voltage of the switch bridge arm on the output port side.

5. The partially isolated three-port resonant DC converter according to claim 4, characterized in that: The first switch bridge arm includes a first switch tube and a second switch tube; The drain of the first switch tube is respectively connected to the positive electrode of the second filter capacitor, the positive electrode of the battery port, and the first end of the second switch bridge arm; The source of the first switch tube is respectively connected to the second end of the first coupled inductor, the first end of the resonant inductor, and the drain of the second switch tube; The source of the second switch tube is respectively connected to the negative electrode of the second filter capacitor, the negative electrode of the first filter capacitor, and the second end of the second switch bridge arm.

6. The partially isolated three-port resonant DC converter according to claim 5, characterized in that: The second switch bridge arm includes a third switch tube and a fourth switch tube; The drain of the third switch tube is connected to the drain of the first switch tube; The source of the third switch tube is connected to the drain of the fourth switch tube, the third end of the first coupled inductor, and the second end of the second coupled inductor; The source of the fourth switch tube is connected to the source of the second switch tube.

7. The partially isolated three-port resonant DC converter according to claim 6, characterized in that: The third switch bridge arm includes a fifth switch tube and a sixth switch tube; The source of the fifth switch tube is connected to the third end of the second coupled inductor and the drain of the sixth switch tube respectively; The drain of the fifth switch tube is connected to the positive electrode of the third filter capacitor and the positive electrode of the load port respectively; The drain of the sixth switch tube is connected to the negative electrode of the fourth filter capacitor and the negative electrode of the load port respectively.

8. The partially isolated three-port resonant DC converter according to claim 7, characterized in that: The partially isolated three-port resonant DC converter includes three power transmission modes; In the first power transmission mode, the power input by the photovoltaic module is greater than the power required by the load, and the excess photovoltaic energy is transmitted to the battery to charge the battery; In the second power transmission mode, the power input by the photovoltaic assembly is less than the power required by the load, and the battery is controlled to discharge to the load to supply power to the load; In the third power transmission mode, the load is powered solely by the photovoltaic assembly or the battery.

9. A control method for a partially isolated three-port resonant DC converter, characterized in that: Applied to the partially isolated three-port resonant DC converter according to any one of claims 1 to 8, the control method comprises: By adjusting the duty cycle of the switch tube on the first switch bridge arm, the maximum power of the photovoltaic module in the photovoltaic energy storage system is tracked or the charging and discharging of the battery in the photovoltaic energy storage system is controlled; By adjusting the duty cycle of the switch tube on the third switch bridge arm, the output voltage of the load in the photovoltaic energy storage system is controlled; By controlling the phase shift angle between the switch tube on the first switch bridge arm and the switch tube on the third switch bridge arm, the bridge arm midpoint voltage on the photovoltaic port side and the bridge arm midpoint voltage on the load port side are made centrally symmetrical.

Images