A Wide-Range Input Non-Isolated Three-Port DC-DC Converter

Abstract

The present invention is a wide-range input non-isolated three-port DC-DC converter, characterized in that it is composed of a four-switch Buck-Boost converter, a photovoltaic cell, a storage battery, three ports of a DC bus, and a Boost converter. The four-switch Buck-Boost circuit is used to connect the photovoltaic cell, the storage battery, and the load, and the Boost circuit is used to connect the photovoltaic cell and the load; the positive electrode of the photovoltaic cell in the four-switch Buck-Boost circuit is connected to the anode of a diode VD1, the diode VD1 is connected to a diode VD2, the diode VD2 is connected to a switch tube S1, and three branches are led out of the source of the switch tube S1. The photovoltaic cell port and the battery port of the present invention are connected by a four-switch Buck-Boost, so that it can be applied to the scene where the photovoltaic cell voltage is greater than the battery voltage, and can also be applied to the scene where the photovoltaic cell voltage is less than the battery voltage.

Description

Technical Field

[0001] The invention relates to the technical field of power electronic converters, and in particular to a wide-range input non-isolated three-port DC-DC converter. Background Art

[0002] With the increasing depletion of fossil energy, renewable energy is gaining more and more attention. However, renewable energy is characterized by randomness, intermittency and slow dynamic response. In order to achieve stable energy supply and quickly respond to load energy needs, it is often necessary to add energy storage equipment. The traditional energy management solution for renewable energy ports, energy storage ports and load ports is to use multiple power electronic conversion devices, but this method has low component utilization, high volume cost and complex control.

[0003] The three-port converter is an integrated converter that can connect three ports at the same time. It has the advantages of compact structure, low volume and cost, and convenient centralized control. It has great application potential in small and medium power renewable energy systems that focus on cost and volume. Many three-port converter topologies have been proposed in many literatures, but these topologies usually have obvious size constraints on the voltage between ports and have difficulties such as narrow application range. For example, [1] Tomas-Manez, K., et al. "High Efficiency Non-isolated Three Port DC-DC Converter for PV-Battery Systems." ECCE-Aisa 2016 IEEE, 2016. The non-isolated three-port converter introduced can only be applied to the scenario where the photovoltaic cell voltage is greater than the battery voltage, [2] Zhang, B., et al. "Novel topology and control of a non-isolated three port DC-DC converter for PV-battery power system." 2017 20th International Conference on Electrical Machines and Systems (ICEMS) IEEE, 2017. The non-isolated three-port converter introduced can only be applied to the scenario where the photovoltaic cell voltage is less than the battery voltage. Summary of the invention

[0004] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to propose a wide-range input non-isolated three-port DC-DC converter, which has three ports and has the characteristics of high power density, wide input range and high reliability.

[0005] To achieve the above object, the technical solution of the present invention is: a wide-range input non-isolated three-port DC-DC converter, which consists of two parts: a four-switch Buck-Boost converter and a Boost converter. The four-switch Buck-Boost converter and the Boost converter are respectively provided with three ports of a photovoltaic cell, a battery, and a DC bus. The four-switch Buck-Boost circuit is used to connect the photovoltaic cell and the battery and the battery and the load, and the Boost circuit is used to connect the photovoltaic cell and the load; the positive electrode of the photovoltaic cell in the four-switch Buck-Boost circuit is connected to the anode of the diode VD1, and the series circuit of the diode VD2 and the switch tube S1 is connected to the cathode of the diode VD1. The source of the switch tube S1 leads to three branches, one branch is connected to one end of the series circuit of the switch tube S2 and VD3, one branch is connected to the drain of the switch tube S3, and the last branch is connected to one end of the inductor L2. The other end of the inductor L2 is connected to the drain of the switch tube S4 on one hand and to the drain of the switch tube S5 on the other hand. The source of the switch tube S5 is connected to one end of the capacitor Cb and the positive electrode of the battery Bat. One end of the parallel circuit of the output capacitor C0 and the load R is connected to the positive electrode of the series circuit of the switch tube S2 and the diode VD3. The other end; in the Boost circuit, the positive electrode of the photovoltaic cell is connected to the anode of the diode VD1, the cathode of VD1 is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the drain of the switch tube S6 on one hand, and to the anode of the diode VD4 on the other hand, the cathode of the diode VD4 is connected to one end of the output filter capacitor C0 and one end of the load R, the other end of the load R is connected to the other end of the output capacitor C0 and the capacitor Cb, the negative electrode of the battery and the photovoltaic cell, and the source of the switch tube S3, the switch tube S4 and the switch tube S6.

[0006] The ports of the photovoltaic cell and the battery are connected by four switches Buck-Boost, which can realize the operation when the photovoltaic cell voltage is greater than the battery voltage and when the photovoltaic cell voltage is less than the battery voltage, thus improving the power density and reliability.

[0007] The beneficial effects of the present invention are as follows: the photovoltaic cell port and the battery port of the present invention are connected by four switches Buck-Boost, which can be applied to the scenario where the photovoltaic cell voltage is greater than the battery voltage, and can also be applied to the scenario where the photovoltaic cell voltage is less than the battery voltage.

[0008] The ports of the photovoltaic cell and the battery are connected by four switches Buck-Boost, which can realize the operation when the photovoltaic cell voltage is greater than the battery voltage and when the photovoltaic cell voltage is less than the battery voltage, thus improving the power density and reliability.

[0009] In the present invention, the power of the photovoltaic cell, the storage battery and the load are respectively controlled by different switch tubes such as switch tubes S1-S4. The voltage and power of the port can be controlled by adjusting the duty cycle of the switch tube, and single-stage power conversion is performed between any two ports, which can realize centralized control. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The overall structure circuit diagram of the wide-range input non-isolated three-port DC-DC converter of the present invention;

[0011] Figure 2 The equivalent circuit diagram of the wide-range input non-isolated three-port DC-DC converter of the present invention is that the photovoltaic cell alone supplies power to the load.

[0012] Figure 3 This is a working waveform diagram of the photovoltaic cell of the present invention supplying power to the load R alone;

[0013] Figure 4 The invention is an equivalent circuit diagram of a wide-range input non-isolated three-port DC-DC converter working in a state where the battery alone supplies power to the load.

[0014] Figure 5 This is a working waveform diagram of the battery of the present invention supplying power to the load R alone;

[0015] Figure 6 The invention is an equivalent circuit diagram of a wide-range input non-isolated three-port DC-DC converter working with a photovoltaic cell and a storage battery to supply power to a load at the same time.

[0016] Figure 7 The equivalent circuit diagram of the wide-range input non-isolated three-port DC-DC converter of the present invention working on the photovoltaic cell and supplying power to the storage battery and the load at the same time. DETAILED DESCRIPTION

[0017] Example 1

[0018] The overall structure circuit diagram of the wide range input non-isolated three-port DC-DC converter of the present invention is as follows: Figure 1As shown, the converter is provided with three ports of photovoltaic cell, storage battery and DC bus, and consists of two parts: a four-switch Buck-Boost converter and a Boost converter. The four-switch Buck-Boost circuit is used to connect the photovoltaic cell and the storage battery as well as the storage battery and the load, and the Boost circuit is used to connect the photovoltaic cell and the load; in the four-switch Buck-Boost circuit, the positive electrode of the photovoltaic cell is connected to the anode of the diode VD1, and the series circuit of the diode VD2 and the switch tube S1 is connected to the cathode of the diode VD1. The source of the switch tube S1 leads to three branches, one branch is connected to one end of the series circuit of the switch tube S2 and VD3, one branch is connected to the drain of the switch tube S3, and the last branch is connected to one end of the inductor L2. The other end of the inductor L2 is connected to the drain of the switch tube S4 on one hand and to the drain of the switch tube S5 on the other hand. The source of the switch tube S5 is connected to one end of the capacitor Cb and the positive electrode of the battery Bat. One end of the parallel circuit of the output capacitor C0 and the load R is connected to the positive electrode of the series circuit of the switch tube S2 and the diode VD3. The other end; in the Boost circuit, the positive electrode of the photovoltaic cell is connected to the anode of the diode VD1, the cathode of VD1 is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the drain of the switch tube S6 on one hand, and to the anode of the diode VD4 on the other hand, the cathode of the diode VD4 is connected to one end of the output filter capacitor C0 and one end of the load R, the other end of the load R is connected to the other end of the output capacitor C0 and the capacitor Cb, the negative electrode of the battery and the photovoltaic cell, and the source of the switch tube S3, the switch tube S4 and the switch tube S6.

[0019] When the wide-range input non-isolated three-port DC-DC converter operates in the photovoltaic cell power supply mode, only the switch tube S6 works, and the other switches are kept off. Figure 2 As shown, the working waveform is as follows Figure 3 When the switch tube S6 is turned on, the photovoltaic cell charges the inductor L1, and the inductor current iL1 rises linearly; when the switch tube S6 is turned off, the photovoltaic cell and the inductor L1 supply power to the load at the same time, and the inductor current iL1 decreases linearly.

[0020] When the wide-range input non-isolated three-port DC-DC converter operates in the mode where the battery alone supplies power to the load, the switches S1, S4, and S6 are turned off, S5 is always turned on, and S3 and S2 are turned on complementary. Figure 4 As shown, the working waveform is as follows Figure 5 shown.

[0021] When the switch tube S3 is turned on and the switch tube S2 is turned off, the photovoltaic cell charges the inductor L2, and the inductor current iL2 rises linearly. When the switch tube S2 is turned on and the switch tube S3 is turned off, the battery and the inductor L2 supply power to the load R at the same time, and the inductor current iL2 drops linearly.

[0022] When the non-isolated three-port converter with wide-range input operates in the mode where the photovoltaic cell and the battery supply power to the load simultaneously, the equivalent circuit is as Figure 6 shown. When the voltage of the photovoltaic cell is greater than the voltage of the battery: At this time, the switch tube S1 remains off, DS6 < DS3, DS3 and DS2 conduct complementarily, S5 is always on, and the working waveform is as Figure 7 shown. When the switch tubes S3 and S5 are turned on and the switch tubes S6 and S2 are turned off, the photovoltaic cell and the inductor L1 supply power to the load at the same time, and the inductor current iL1 drops linearly; the battery charges the inductor L2, and the inductor current iL2 rises linearly. When the switch tubes S3 and S5 continue to be on, the switch tube S6 is on, and the switch tube S2 is off, the photovoltaic cell charges the inductor L1, and the inductor current iL1 rises linearly; the battery continues to charge the inductor L2, and the inductor current iL2 rises linearly. When the switch tubes S2 and S5 are turned on and the switch tubes S3 and S6 are turned off, the photovoltaic cell and the inductor L1 supply power to the load together, and the inductor current iL1 drops linearly; the battery and the inductor L2 supply power to the load together, and the inductor current iL2 drops linearly.

[0023] When the voltage of the photovoltaic cell is less than the voltage of the battery: At this time, the switch tubes S1 and S4 do not work, DS6 > DS2. When the switch tube S6 is turned on and the switch tubes S2 and S5 are turned off, the battery does not participate in the work, and the photovoltaic cell PV charges the inductor L1, and the inductor current iL1 rises linearly. When the switch tubes S2, S5, and S6 are all turned on, the photovoltaic cell continues to charge the inductor L1, and the inductor current iL1 continues to rise linearly; the battery charges the inductor L2, and the inductor current iL2 rises linearly;

[0024] When the switch tubes S2 and S5 continue to be on and the switch tube S6 is turned off, the photovoltaic cell, the inductor L1, the battery, and the inductor L2 charge the load at the same time, and both the inductor current iL1 and the inductor current iL2 drop linearly.

[0025] The non-isolated three-port converter with wide-range input operates when the photovoltaic cell supplies power to the battery and the load at the same time, and when the photovoltaic cell voltage is greater than the battery voltage: at this time, the switch tube S2 and the switch tube S4 remain turned off, the switch tube S5 is always turned on, the body diode of the switch tube S3 serves as the freewheeling channel of the inductor L2, S1 and S6 are alternately turned on, when the switch tubes S1 and S5 are turned on, and the switch S6 is turned off, the photovoltaic cell charges the inductor L2 and the battery, and the inductor current iL2 rises linearly; at the same time, the photovoltaic cell and the inductor L1 jointly supply power to the load R, and the inductor current iL1 decreases linearly. When the switch tubes S1 and S5 continue to be turned on, and the switch S6 is turned on, the photovoltaic cell continues to charge the inductor L2 and the battery, and the inductor current iL2 rises linearly; at the same time, the photovoltaic cell charges the inductor L1, and the inductor current iL1 rises linearly. When the switch tubes S1 and S6 are turned off and the switch S5 continues to be turned on, the body diode of the switch tube S3 serves as a freewheeling channel for the inductor L2. At this time, the inductor L2 continues to charge the battery through the body diode of the switch tube S3, and the inductor current iL2 decreases linearly; at the same time, the photovoltaic cell and the inductor L1 jointly supply power to the load R, and the inductor current iL1 decreases linearly.

[0026] When the photovoltaic cell voltage is lower than the battery voltage: at this time, the switch tube S2 and the switch tube S3 do not participate in the work, DS6>DS4, the switch tube S1 is always turned on, when the switch tube S1, the switch tube S4 and the switch tube S6 are turned on, the photovoltaic cell charges the inductor L1 and the inductor L2, and the inductor current iL1 and the inductor current iL2 rise linearly. When the switch tubes S5 and the switch tube S6 are turned on and the switch tube S4 is turned off, the photovoltaic cell continues to charge the inductor L1, and the inductor current iL1 decreases linearly. At the same time, the photovoltaic cell and the inductor L2 charge the battery together, and the inductor current iL2 decreases linearly. When the switch tubes S1 and the switch tube S5 are turned on and the switch tubes S4 and the switch tube S6 are turned off, the photovoltaic cell and the inductor L1 jointly supply power to the load, and the inductor current iL1 decreases linearly. At the same time, the photovoltaic cell and the inductor L2 continue to charge the battery together, and the inductor current iL2 continues to decrease linearly.

[0027] The specific embodiments of the present invention are described in detail in conjunction with the above drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in this field without departing from the purpose of the present invention.

[0028] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. The various components mentioned in the present invention are common technologies in the existing field. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A wide range input non-isolated three-port DC-DC converter, characterized in that: The invention is composed of a four-switch Buck-Boost converter and a Boost converter. The four-switch Buck-Boost converter and the Boost converter are respectively provided with three ports of a photovoltaic cell, a storage battery and a DC bus. The four-switch Buck-Boost circuit is used to connect the photovoltaic cell and the storage battery as well as the storage battery and the load, and the Boost circuit is used to connect the photovoltaic cell and the load. The positive electrode of the photovoltaic cell in the four-switch Buck-Boost circuit is connected to the anode of the diode VD1, the diode VD1 is connected to the diode VD2, the diode VD2 is connected to the switch tube S1, In the four-switch Buck-Boost circuit, the positive electrode of the photovoltaic cell is connected to the anode of the diode VD1, and the series circuit of the diode VD2 and the switch tube S1 is connected to the cathode of the diode VD1; In the Boost circuit, the positive electrode of the photovoltaic cell is connected to the anode of the diode VD1, the cathode of VD1 is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the drain of the switch tube S6 on one hand, and to the anode of the diode VD4 on the other hand, and the cathode of the diode VD4 is connected to one end of the output filter capacitor C0 and one end of the load R; The source of the switch tube S1 leads to three branches, one branch is connected to one end of the series circuit of the switch tube S2 and VD3, one branch is connected to the drain of the switch tube S3, and the last branch is connected to one end of the inductor L2. The other end of the inductor L2 is respectively connected to the drain of the switch tube S4 and the drain of the switch tube S5. The source of the switch tube S5 is connected to one end of the capacitor Cb and the positive electrode of the battery Bat. One end of the parallel circuit of the output capacitor CO and the load R is connected to the other end of the series circuit of the switch tube S2 and the diode VD3. In the Boost circuit, the positive electrode of the photovoltaic cell is connected to the anode of the diode VD1, the cathode of VD1 is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the drain of the switch tube S6 on one hand, and to the anode of the diode VD4 on the other hand, the cathode of the diode VD4 is connected to one end of the output filter capacitor CO and one end of the load R, the other end of the load R is connected to the other end of the output capacitor CO and the capacitor Cb, the negative electrode of the battery and the photovoltaic cell, and the source of the switch tubes S3, S4 and S6.

2. A wide-range input non-isolated three-port DC-DC converter according to claim 1, characterized in that: The ports of the photovoltaic cell and the ports of the storage battery are connected via four switches Buck-Boost.

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