A partially isolated three-port resonant DC converter and its control method

Abstract

The present invention provides a partially isolated three-port resonant DC converter and its control method, which is applied to a photovoltaic energy storage system. The photovoltaic port is the first input end of a two-phase interleaved boost circuit and is connected to the output end of the photovoltaic modules in the photovoltaic energy storage system; the battery port is the second input end of the two-phase interleaved boost circuit and the input end of the resonant circuit, and is connected to the battery in the photovoltaic energy storage system; the load port is the output end of the resonant circuit and is connected to the load in the photovoltaic energy storage system; the two-phase interleaved boost circuit and the resonant circuit are integrated into a single-stage structure through the multiplexing of switch bridge arms, and at the same time, magnetic integration is achieved through a coupled inductor, reducing the number of devices and increasing the power density of the device; by adjusting the duty cycle of the first switch bridge arm, the maximum power of the photovoltaic modules can be tracked or the charging and discharging of the battery can be controlled, and by adjusting the duty cycle of the third switch bridge arm, the output voltage of the load can be controlled, realizing independent control of ports and wide voltage gain at a fixed switching frequency.

Description

Technical Field

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

[0002] In recent years, with the increasingly prominent energy and environmental problems, clean energy represented by solar energy has developed rapidly. However, affected by the environment, the output of solar energy has disadvantages such as volatility and intermittency, 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 and energy storage system is beneficial to improving the flexibility and controllability of photovoltaic power generation. Under the traditional architecture, multiple two-port converters are used to connect the photovoltaic modules, storage batteries and loads in the photovoltaic and energy storage system, but this solution has 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 problems 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, and the purpose is to improve the power density of the converter and achieve efficient energy conversion under a wide voltage gain.

[0004] To achieve the above purpose, the present invention provides a partially isolated three-port resonant DC converter, which is applied to a photovoltaic energy storage system and includes:

[0005] 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;

[0006] The two-phase interleaved boost circuit and the resonant circuit share the first switch bridge arm, the second switch bridge arm and the second filter capacitor;

[0007] The first end of the first switch bridge arm, the first end of the second switch bridge arm, and the positive pole of the second filter capacitor are all connected to the positive pole 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 pole of the second filter capacitor, the negative pole of the photovoltaic port, the first end of the first coupled inductor, and the positive pole of the photovoltaic port are all connected to the negative pole of the battery port;

[0008] 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;

[0009] The third end of the first coupled inductor is respectively connected to the third end of the second switch bridge arm and the second end of the second coupled inductor;

[0010] The third terminal of the second coupled inductor is connected to the third terminal of the third switch arm, and the first terminal of the third switch arm is connected to the positive pole of the load port;

[0011] The fourth terminal of the second coupled inductor is respectively connected to the second terminal of the third switch arm and the negative pole of the load port;

[0012] The photovoltaic port is connected to the output terminal of the photovoltaic module in the photovoltaic energy storage system as the first input terminal of the two-phase interleaved boost circuit;

[0013] The battery port is connected to the output terminal of the battery in the photovoltaic energy storage system as the second input terminal of the two-phase interleaved boost circuit and the input terminal of the resonant circuit;

[0014] The load port is connected to the input terminal of the load in the photovoltaic energy storage system as the output terminal of the resonant circuit.

[0015] Furthermore, the two-phase interleaved boost circuit further includes:

[0016] A first filter capacitor;

[0017] The positive pole of the first filter capacitor is respectively connected to the positive pole of the photovoltaic port and the first terminal of the first coupled inductor;

[0018] The negative pole of the first filter capacitor is connected to the negative pole of the photovoltaic port.

[0019] Furthermore, the resonant circuit includes:

[0020] A third filter capacitor, a fourth filter capacitor, and a resonant capacitor;

[0021] The positive pole of the third filter capacitor is respectively connected to the first terminal of the third switch arm and the positive pole of the load port;

[0022] The negative pole of the third filter capacitor is respectively connected to the fourth terminal of the second coupled inductor and the positive pole of the fourth filter capacitor;

[0023] The negative pole of the fourth filter capacitor is respectively connected to the second terminal of the third switch arm and the negative pole of the load port;

[0024] The third terminal of the third switch arm is connected to the third terminal of the second coupled inductor;

[0025] The first terminal of the second coupled inductor is connected to the third terminal of the first switch arm through the resonant capacitor;

[0026] The second terminal of the second coupled inductor is connected to the third terminal of the second switch arm.

[0027] Furthermore, the voltage between the midpoints of the first switch arm and the second switch arm is the midpoint voltage of the switch arm on the photovoltaic port side;

[0028] The voltage between the midpoint of the third switch arm and the negative electrode of the third filter capacitor is the midpoint voltage of the switch arm on the output port side.

[0029] Furthermore, the first switch arm includes a first switch and a second switch;

[0030] The drain of the first switch 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 arm;

[0031] The source of the first switch 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;

[0032] The source of the second switch 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 arm.

[0033] Furthermore, the second switch arm includes a third switch and a fourth switch;

[0034] The drain of the third switch is connected to the drain of the first switch;

[0035] The source of the third switch is connected to the drain of the fourth switch, the third end of the first coupled inductor, and the second end of the second coupled inductor;

[0036] The source of the fourth switch is connected to the source of the second switch.

[0037] Furthermore, the third switch arm includes a fifth switch and a sixth switch;

[0038] The source of the fifth switch is respectively connected to the third end of the second coupled inductor and the drain of the sixth switch;

[0039] The drain of the fifth switch is respectively connected to the positive electrode of the third filter capacitor and the positive electrode of the load port;

[0040] The drain of the sixth switch is respectively connected to the negative electrode of the fourth filter capacitor and the negative electrode of the load port.

[0041] Furthermore, the duty cycle of the first switch is used to control the photovoltaic module to track the maximum power and the battery to charge and discharge;

[0042] The duty cycle of the fifth switch is used to control the voltage of the output port.

[0043] Furthermore, the partial isolation type three-port resonant DC converter includes three power transfer modes;

[0044] In the first power transfer mode, the power input by the photovoltaic module is greater than the power required by the load, and the excess photovoltaic energy is transferred to the battery to charge the battery;

[0045] In the second power transfer mode, the power input by the photovoltaic module is less than the power required by the load, and the control battery discharges to the load to supply power to the load.

[0046] In the third power transfer mode, the load is powered by the photovoltaic module or the battery alone.

[0047] 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:

[0048] By adjusting the duty cycle of the switching tubes on the first switch bridge arm to track the maximum power of the photovoltaic module in the photovoltaic energy storage system or control the charge and discharge of the battery in the photovoltaic energy storage system;

[0049] By adjusting the duty cycle of the switching tubes on the third switch bridge arm to control the output voltage of the load in the photovoltaic energy storage system;

[0050] By controlling the phase shift angle between the switching tubes on the first switch bridge arm and the switching tubes on the third switch bridge arm, the center of the waveform of the midpoint voltage of the bridge arm on the photovoltaic port side is symmetric with the center of the waveform of the midpoint voltage of the bridge arm on the load port side.

[0051] The above solution of the present invention has the following beneficial effects:

[0052] The present invention is applied to a photovoltaic energy storage system, which includes a photovoltaic port, a battery port, a load port, a first coupling inductor, a second coupling 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 multiplexing, and at the same time, magnetic integration is realized through the first coupling inductor and the second coupling inductor, reducing the number of devices and improving the power density of the device; by adjusting the duty cycle of the switching tubes on the first switch bridge arm to track the maximum power of the photovoltaic module or control the charge and discharge of the battery, and by adjusting the duty cycle of the switching tubes 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.

[0053] Other beneficial effects of the present invention will be described in detail in the subsequent specific implementation part. Description of the Drawings

[0054] Figure 1Topological structure diagram of an embodiment of the present invention;

[0055] Figure 2 Operating waveform diagram of the converter in an embodiment of the present invention. Detailed implementation manners

[0056] 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 some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0057] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is 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 thus cannot be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0058] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", "connected" 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 directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0059] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0060] The present invention provides a partially isolated three-port resonant DC converter and its control method for solving existing problems.

[0061] As Figure 1 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 and includes:

[0062] Photovoltaic port U pv 、Battery port U B 、Load port U o, the second coupling inductor, the third switch arm, the two-phase interleaved boost circuit, the resonant circuit, and the first coupling inductor for storing energy for the two-phase interleaved boost circuit;

[0063] The two-phase interleaved boost circuit and the resonant circuit share the first switch arm, the second switch arm, and the second filter capacitor C2;

[0064] The first end of the first switch arm, the first end of the second switch arm, and the positive electrode of the second filter capacitor C2 are all connected to the positive electrode of the battery port U B The second end of the first switch arm, the second end of the second switch arm, the negative electrode of the second filter capacitor C2, the negative electrode of the photovoltaic port U pv The first end of the first coupling inductor, the positive electrode of the photovoltaic port U pv Are all connected to the negative electrode of the battery port U B ;

[0065] The second end of the first coupling inductor is respectively connected to the third end of the first switch arm and the first end of the second coupling inductor;

[0066] The third end of the first coupling inductor is respectively connected to the third end of the second switch arm and the second end of the second coupling inductor;

[0067] The third end of the second coupling inductor is connected to the third end of the third switch arm, and the first end of the third switch arm is connected to the positive electrode of the load port U o ;

[0068] The fourth end of the second coupling inductor is respectively connected to the second end of the third switch arm and the negative electrode of the load port U o ;

[0069] The photovoltaic port U pv 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;

[0070] The battery port U B 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;

[0071] 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.

[0072] 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 sharing the first switch arm, the second switch arm, and the second filter capacitor C2.

[0073] In the embodiment of the present invention, the first coupled inductor is a coupled inductor with negative coupling integrated by two DC inductors, which is beneficial to reducing the current ripple of the photovoltaic port.

[0074] Most preferably, the two-phase interleaved boost circuit further includes:

[0075] A first filter capacitor C1;

[0076] The positive electrode of the first filter capacitor C1 is respectively connected to the positive electrode of the photovoltaic port U pv and the first end of the first coupled inductor;

[0077] The negative electrode of the first filter capacitor C1 is connected to the negative electrode of the photovoltaic port U pv ;

[0078] Most preferably, the resonant circuit includes:

[0079] A third filter capacitor C3, a fourth filter capacitor C4, and a resonant capacitor C r ;

[0080] The positive electrode of the third filter capacitor C3 is respectively connected to the first end of the third switch leg and the positive electrode of the load port U o ;

[0081] The negative electrode of the third filter capacitor C3 is respectively connected to the fourth end of the second coupled inductor and the positive electrode of the fourth filter capacitor C4;

[0082] The negative electrode of the fourth filter capacitor C4 is respectively connected to the second end of the third switch leg and the negative electrode of the load port U o ;

[0083] The third end of the third switch leg is connected to the third end of the second coupled inductor;

[0084] The first end of the second coupled inductor is connected to the third end of the first switch leg through the resonant capacitor C r ;

[0085] The second end of the second coupled inductor is connected to the third end of the second switch leg.

[0086] In the embodiment of the present invention, the second coupled inductor and the resonant capacitor C r constitute a resonant network for transferring energy, and the second coupled inductor is used to realize the connection between the load port U o and the photovoltaic port U pv , the battery port U BElectrical isolation between; realizing the integrated reuse of the DC inductance of the two-phase interleaved Boost circuit by using the first coupling inductor, and realizing the integrated reuse of the resonant inductor and the transformer in the resonant circuit by using the second coupling inductor, reducing the number of components in the converter while achieving low current ripple on the battery side, which is beneficial to improving the power density of the device.

[0087] 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 midpoint voltage U of the switch bridge arm on the photovoltaic port U pv side AB , A is the midpoint potential of the first switch bridge arm, and B is the midpoint potential of the second switch bridge arm;

[0088] The voltage between the midpoint of the third switch bridge arm and the negative electrode of the third filter capacitor C3 is the midpoint voltage U of the switch bridge arm on the load port U o side 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.

[0089] In the embodiment of the present invention, the switching frequency of the partial isolation type three-port resonant DC converter is equal to the resonant frequency, and the switching tubes on the same bridge arm conduct complementarily.

[0090] Most preferably, the first switch bridge arm includes a first switching tube Q1 and a second switching tube Q2;

[0091] The drain of the first switching tube Q1 is respectively connected to the positive electrode of the second filter capacitor C2, the positive electrode of the battery port U B , and the first end of the second switch bridge arm;

[0092] The source of the first switching 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 switching tube Q2;

[0093] The source of the second switching tube Q2 is respectively connected to the negative electrode of the second filter capacitor C2, the negative electrode of the first filter capacitor C1, and the second end of the second switch bridge arm.

[0094] Most preferably, the second switch bridge arm includes a third switching tube Q3 and a fourth switching tube Q4;

[0095] The drain of the third switching tube Q3 is connected to the drain of the first switching tube Q1;

[0096] The source of the third switching tube Q3 is connected to the drain of the fourth switching tube Q4, the third end of the first coupling inductor, and the second end of the second coupling inductor;

[0097] The source of the fourth switching tube Q4 is connected to the source of the second switching tube Q2.

[0098] In the embodiment of the present invention, the duty cycle of the first switching transistor Q1 is the same as that of the third switching transistor Q3, and the ratio of the difference in the on-time between the first switching transistor Q1 and the third switching transistor Q3 to the switching period is 0.5.

[0099] Most preferably, the third switching bridge arm includes a fifth switching transistor Q5 and a sixth switching transistor Q6;

[0100] The source of the fifth switching transistor Q5 is respectively connected to the third terminal of the second coupling inductor and the drain of the sixth switching transistor Q6;

[0101] The drain of the fifth switching transistor Q5 is respectively connected to the positive electrode of the third filter capacitor C3 and the positive electrode of the load port U o of the positive electrode connection;

[0102] The drain of the sixth switching transistor Q6 is respectively connected to the negative electrode of the fourth filter capacitor C4 and the negative electrode of the load port Uo.

[0103] It should be noted that the first switching transistor Q1, the second switching transistor Q2, the third switching transistor Q3, the fourth switching transistor Q4, the fifth switching transistor Q5, and the sixth switching transistor Q6 all use power transistors MOQFETs with anti-parallel diodes and drain-source parasitic capacitances.

[0104] In the embodiment of the present invention, two switching transistors in the same switching bridge arm conduct complementarily; the duty cycle of the first switching transistor Q1 is the same as that of the third switching transistor Q3, and the ratio of the difference in the on-time between the first switching transistor and the third switching transistor to the switching period is 0.5.

[0105] Specifically, the partially isolated three-port resonant DC converter includes three power transfer modes;

[0106] In the first power transfer mode, the power input by the photovoltaic module is greater than the power required by the load, and the excess photovoltaic energy is transferred to the battery for charging the battery;

[0107] In the second power transfer 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 for powering the load;

[0108] In the third power transfer mode, the load is powered by the photovoltaic module or the battery.

[0109] It should be noted that in the embodiment of the present invention, the driving logics of the partially isolated three-port resonant DC converter in the three power transfer modes are the same, so the working principles in the three modes are the same; by controlling the switching transistors on the first switching bridge arm on the photovoltaic port U pv side and the load port U oThe duty cycle of the upper switch tube on the side third switch tube bridge arm is adjusted to achieve system energy management under a wide voltage range. Moreover, the drive logic is consistent in all power transmission modes, enabling smooth switching between modes. The voltage gain of the converter is only related to the duty cycle and is not affected by the transmitted power, which is conducive to achieving low control complexity.

[0110] The embodiment of the present invention also 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:

[0111] By adjusting the duty cycle of the switch tube on the first switch bridge arm to track the maximum power of the photovoltaic module in the photovoltaic energy storage system and control the charge and discharge of the battery in the photovoltaic energy storage system;

[0112] By adjusting the duty cycle of the switch tube on the third switch bridge arm to control the output voltage of the load in the photovoltaic energy storage system;

[0113] 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 midpoint voltage waveforms of the bridge arms on the photovoltaic port side and the load port side are centrosymmetric.

[0114] It should be noted that under normal operating conditions, adjusting the duty cycle of the first switch tube Q1 d 1 is 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 is used to control the charge and discharge of the battery to prevent overcharging of the battery.

[0115] 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 midpoint voltage of the switch bridge arm on the photovoltaic port U pv side and the midpoint voltage of the switch bridge arm on the load port U o side can be centrosymmetric in waveform. Therefore, the waveforms of the partially isolated three-port resonant DC converter in the first half and the second half of the switching cycle are symmetric. As Figure 2 shown, the working principles are similar, so the working process within half of the switching cycle can be divided into 6 modes, specifically as follows:

[0116] Mode 1: At time t0, the sixth switch tube Q6 is turned off, and the junction capacitors of the fifth switch tube Q5 and the sixth switch tube Q6 are charged and discharged within the dead zone;

[0117] 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 conducting, and the midpoint voltage of the switch bridge arm on the photovoltaic port U pv side is equal to 0, and the load port Uo The waveform of the midpoint voltage of the switching bridge arm on the side is equal to L1 the primary current i of the first coupled inductor L2 and the secondary current i of the first coupled inductor r increase linearly, and the second coupled inductor resonates with the first resonant capacitor C

[0118] Mode 3: At time t2, the second switch Q2 is turned off, and the junction capacitors of the two switches in the first switching bridge arm charge and discharge in the dead zone;

[0119] Mode 4: At time t3, the first switch Q1 is turned on with zero voltage, and the midpoint voltage of the switching bridge arm on the photovoltaic port U pv side changes from 0 to equal to the battery terminal voltage U B the primary current i of the first coupled inductor L1 decreases linearly, and the resonant current i r varies sinusoidally;

[0120] Mode 5: At time t4, the first switch Q1 is turned off, and the junction capacitors of the first switch Q1 and the second switch Q2 charge and discharge in the dead zone;

[0121] Mode 6: At time t5, the second switch Q2 is turned on with zero voltage, and the midpoint voltage of the switching bridge arm on the photovoltaic port U pv side becomes 0, the primary current i of the first coupled inductor L1 increases linearly, and the resonant current i r varies sinusoidally.

[0122] Among them, the durations of Mode 2 and Mode 6 are equal, and the voltage gain from the photovoltaic port U pv to the battery port U B is:

[0123] ;

[0124] The gain from the photovoltaic port U pv to the load port U o is:

[0125] ;

[0126] Among them, represents the duty cycle of the switch on the switching bridge arm at the photovoltaic port, that is, the duty cycle of the first switch Q1, represents the duty cycle of the switch on the switching bridge arm at the output port, that is, the duty cycle of the fifth switch Q5.

[0127] In the embodiment of the present invention, the voltage at the photovoltaic port U pv is 30V to 50V, and the battery port U BThe voltage at [location] is 80V, load port U o When the voltage at [location] is 400V, a 600W converter prototype is built. All the switching transistors in the switching network adopt power transistors MOQFETs with anti-parallel diodes and drain-source parasitic capacitances. The driving signals of the main circuit are generated by the TI digital signal processor TMQ320F28335. Under this experimental condition, the partially isolated three-port resonant DC converter provided by the embodiment of the present invention can operate normally under different working conditions.

[0128] The embodiment of the present invention is applied to a photovoltaic energy storage system, which includes a photovoltaic port, a battery port, a load port, a first coupling inductor, a second coupling inductor, a third switching 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 the multiplexing of the switching bridge arm, and at the same time, magnetic integration is realized through the first coupling inductor and the second coupling inductor, reducing the number of devices and improving the power density of the device. By adjusting the duty cycle of the switching transistor on the first switching bridge arm, the maximum power of the photovoltaic module can be tracked or the charge and discharge of the battery can be controlled. By adjusting the duty cycle of the switching transistor on the third switching bridge arm, the output voltage of the load can be controlled, and port independent control and wide voltage gain can be realized at a fixed switching frequency.

[0129] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A partially isolated three-port resonant DC converter, characterized in that: Applied to photovoltaic energy storage system, some isolated three-port resonant DC converters include: 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 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 respectively connected to the negative electrode of the photovoltaic port, the negative electrode of the second filter capacitor, and the negative electrode of the battery port; The resonant circuit comprises a third filter capacitor, a fourth filter capacitor, and a resonant capacitor; The first switch bridge arm includes a first switch tube and a second switch tube; The second switch bridge arm includes a third switch tube and a fourth switch tube; The third switch bridge arm includes a fifth switch tube and a sixth 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 drain of the third switch tube; 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 capacitor, and the drain of the second switch tube, and the second end of the resonant capacitor is connected to the first end of the second coupling inductor; The source electrode 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 source electrode of the fourth 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 fifth switch tube is respectively connected to the third end of the second coupling inductor and the drain of the sixth switch tube, and the fourth end of the second coupling inductor is respectively connected to the negative electrode of the third filter capacitor and the positive electrode of the fourth filter capacitor; 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 source electrode 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; The first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are all power transistors MOSFETs having anti-parallel diodes and drain-source parasitic capacitances; 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 turned on; The control method of the partially isolated three-port resonant DC converter 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 symmetrical in waveform; 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.

2. The partially isolated three-port resonant DC converter according to claim 1, 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.

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