A non-isolated bidirectional DC-DC converter

Abstract

The utility model provides a kind of non-isolated bidirectional DC-DC converter, belong to power electronics technical field.The utility model non-isolated bidirectional DC-DC converter includes input filter circuit, main power conversion circuit and output filter circuit.Input filter circuit includes input power supply, first inductance and third capacitor.Main power conversion circuit includes first switch tube, second switch tube, third switch tube, fourth switch tube, first capacitor, second capacitor and second inductance.Output filter circuit includes output power supply and third inductance.Compared with prior art, the utility model effectively solves the problem of high ripple content on high voltage side and large number of switching devices.

Description

Technical Field

[0001] This utility model belongs to the field of power electronics technology, specifically relating to a non-isolated bidirectional DC-DC converter. Background Technology

[0002] As renewable energy is increasingly integrated into the existing power grid, the application of power electronics technology in DC-DC conversion is steadily expanding. Renewable energy output voltage is typically low, therefore, in many practical applications (such as scenarios where renewable energy is coordinated with the power grid, energy storage systems, and high-voltage loads), it is necessary to significantly boost the low voltage output of renewable energy.

[0003] Meanwhile, the output power of renewable energy sources is unstable, leading to the increasingly widespread application of batteries in energy storage. DC-DC converters are commonly used in battery energy storage systems.

[0004] To achieve various voltage gains, most DC-DC converters adopt designs based on cascaded or non-cascaded structures.

[0005] Currently available DC-DC converters, while achieving low-side current ripple elimination, exhibit high ripple content on the high-side topology. This can negatively impact devices connected to the high-side, such as increasing additional losses, reducing stability, and shortening lifespan. Furthermore, a larger number of switching devices (typically 6-10 in a bidirectional DC-DC converter) not only increases converter cost but also complicates circuitry, increasing control difficulty and the probability of malfunctions, and may also affect overall converter efficiency. Utility Model Content

[0006] The purpose of this invention is to provide a non-isolated bidirectional DC-DC converter to solve the problems of high ripple content on the high voltage side and a large number of switching devices in the existing topology.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, this utility model provides a non-isolated bidirectional DC-DC converter, including an input filter circuit, a main power conversion circuit, and an output filter circuit;

[0009] The input filtering circuit includes an input power supply, a first inductor, and a third capacitor; the main power conversion circuit includes a first switch, a second switch, a third switch, a fourth switch, a first capacitor, a second capacitor, and a second inductor; the output filtering circuit includes an output power supply and a third inductor.

[0010] The positive terminal of the input power supply is connected to one end of the third capacitor, the negative terminal of the input power supply is connected to the other end of the third capacitor, one end of the third capacitor is connected to one end of the first inductor, the other end of the first inductor is connected to the source of the third switching transistor, the other end of the third capacitor is connected to the source of the first switching transistor, the source of the first switching transistor is connected to the other end of the first capacitor, and the drain of the first switching transistor is connected to the source of the third switching transistor.

[0011] One end of the first inductor is connected to one end of the second inductor, the other end of the second inductor is connected to one end of the second capacitor, the other end of the second capacitor is connected to the drain of the fourth switching transistor, one end of the second capacitor is connected to the source of the second switching transistor, the drain of the second switching transistor is connected to one end of the first capacitor, and the drain of the third switching transistor is connected to the source of the fourth switching transistor.

[0012] The drain of the fourth switching transistor is connected to one end of the third inductor, the other end of the third inductor is connected to the positive terminal of the output power supply, and the other end of the first capacitor is connected to the negative terminal of the output power supply.

[0013] A further improvement of this invention is that the first switch, the second switch, the third switch, and the fourth switch are all N-channel MOSFETs.

[0014] A further improvement of this invention is that the first inductor, the second inductor, and the third inductor are all ferrite core inductors.

[0015] A further improvement of this invention is that the first capacitor and the second capacitor are both polarized electrolytic capacitors, and the third capacitor is a filter capacitor.

[0016] A further improvement of this invention is that the size of the first inductor is 600μH-800μH, the size of the second inductor is 600μH-1000μH, and the size of the third inductor is 800μH-1200μH.

[0017] A further improvement of this invention is that the first capacitor, the second capacitor, and the third capacitor are all 100μF-400μF in size.

[0018] A further improvement of this invention is that the input power supply is a DC power supply.

[0019] A further improvement of this invention is that the output power supply is a DC power supply.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] Compared to existing non-isolated bidirectional DC-DC converters, this novel non-isolated bidirectional DC-DC converter utilizes a collaborative working mechanism of inductors, switches, and capacitors. By matching the parameters of the first and second inductors and combining this with a synchronous rectification strategy for the switches, it achieves high buck gain from the high-voltage side to the low-voltage side during charging and high boost gain from the low-voltage side to the high-voltage side during discharging within a single power conversion stage. This novel non-isolated bidirectional DC-DC converter utilizes the principle of reverse cancellation of inductor current (inductor current on the input side) to significantly reduce or even eliminate current ripple on the battery side (input side), improving system stability. Furthermore, this novel non-isolated bidirectional DC-DC converter uses relatively few switching devices (4 switches), effectively solving the problems of high high-voltage side ripple content and a large number of switching devices in existing topologies.

[0022] Furthermore, this utility model discloses that the first, second, third, and fourth switching transistors are all N-channel MOSFETs. N-channel MOSFETs not only have low losses and fast response, but also have high stress resistance and simple drive circuit design. Attached Figure Description

[0023] Figure 1 This is a topology diagram of the non-isolated bidirectional DC-DC converter of this utility model;

[0024] Figure 2 This is a schematic diagram of the first operating state of the non-isolated bidirectional DC-DC converter of this utility model;

[0025] Figure 3 This is a schematic diagram of the second operating state of the non-isolated bidirectional DC-DC converter of this utility model;

[0026] Figure 4 This is a schematic diagram of the third operating state of the non-isolated bidirectional DC-DC converter of this utility model;

[0027] Figure 5 This is a schematic diagram of the fourth operating state of the non-isolated bidirectional DC-DC converter of this utility model. Detailed Implementation

[0028] To further understand the content of this utility model, the following detailed description is provided in conjunction with the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the utility model.

[0029] Example 1:

[0030] This embodiment discloses a non-isolated bidirectional DC-DC converter. The topology of this non-isolated bidirectional DC-DC converter is shown below. Figure 1 As shown, the technical solution of this utility model is specifically described as follows:

[0031] This utility model of a non-isolated bidirectional DC-DC converter includes an input filter circuit, a main power conversion circuit, and an output filter circuit. The input filter circuit, main power conversion circuit, and output filter circuit are described in detail below:

[0032] The input filter circuit includes the input power supply (also called the low-voltage side power supply) V LV The main power conversion circuit includes a first inductor L1 and a third capacitor C3. The main power conversion circuit includes a first switch S1, a second switch S2, a third switch Q1, a fourth switch Q2, a first capacitor C1, a second capacitor C2, and a second inductor L2. The output filter circuit includes the output power supply V... HV And the third inductor L3.

[0033] Input power V LV The positive terminal is connected to one end of the third capacitor C3, and the input power supply V LV The negative terminal of the capacitor is connected to the other end of the third capacitor C3. One end of the third capacitor C3 is connected to one end of the first inductor L1. The other end of the first inductor L1 is connected to the source of the third switch Q1. The other end of the third capacitor C3 is connected to the source of the first switch S1. The source of the first switch S1 is connected to the other end of the first capacitor C1. The drain of the first switch S1 is connected to the source of the third switch Q1.

[0034] One end of the first inductor L1 is connected to one end of the second inductor L2, the other end of the second inductor L2 is connected to one end of the second capacitor C2, the other end of the second capacitor C2 is connected to the drain of the fourth switch Q2, one end of the second capacitor C2 is connected to the source of the second switch S2, the drain of the second switch S2 is connected to one end of the first capacitor C1, and the drain of the third switch Q1 is connected to the source of the fourth switch Q2.

[0035] The drain of the fourth switching transistor is connected to one end of the third inductor L3, and the other end of the third inductor L3 is connected to the output power supply (also called the high-voltage side power supply). HV The positive terminal of the capacitor is connected to the output power supply V. HV The negative electrode.

[0036] In this embodiment, the first switch S1, the second switch S2, the third switch Q1, and the fourth switch Q2 are all N-channel MOSFETs. Specifically, the N-channel MOSFET used in this embodiment is the IRFP250N, and the switching frequency of the N-channel MOSFET in this embodiment is 20kHz. N-channel MOSFETs not only have low losses and fast response, but also high stress resistance and simple drive circuit design.

[0037] The first switch S1, the second switch S2, the third switch Q1, and the fourth switch Q2 are all integrated body diodes. The anode of the body diode is connected to the source of the body diode, and the cathode of the body diode is connected to the drain of the body diode, which are used for freewheeling and synchronous rectification assistance.

[0038] In this embodiment, the first inductor L1, the second inductor L2, and the third inductor L3 are all ferrite core inductors.

[0039] In this embodiment, the first capacitor C1 and the second capacitor C2 are both polarized electrolytic capacitors, and the third capacitor C3 is a filter capacitor.

[0040] In this embodiment, the value of the first inductor L1 is 600μH-800μH, and the optimal value of the first inductor L1 in this embodiment is 750μH.

[0041] In this embodiment, the value of the second inductor L2 is 600μH-1000μH, and the optimal value of the second inductor L2 in this embodiment is 810μH.

[0042] In this embodiment, the value of the third inductor L3 is 800μH-1200μH, and the optimal value of the third inductor L3 in this embodiment is 984μH.

[0043] In this embodiment, the values ​​of the first capacitor C1, the second capacitor C2, and the third capacitor C3 are all between 100μF and 400μF. The optimal value for the first capacitor C1, the second capacitor C2, and the third capacitor C3 in this embodiment is 220μF.

[0044] In this embodiment, the models of the first inductor L1, the second inductor L2, and the third inductor L3 are not limited.

[0045] In this embodiment, the types of the first capacitor C1, the second capacitor C2, and the third capacitor C3 are not limited.

[0046] In this embodiment, the input power supply V LV It is a DC power supply (36V DC power supply).

[0047] The output power supply V in this embodiment HV It is a DC power supply (110V DC power supply).

[0048] To highlight the topology, Figure 1 In the topology diagram, the output filter circuit is simplified as the output power supply V. HV Along with the third inductor L3, the output filter circuit also includes an output filter capacitor C. HV and high-voltage side load R HV .

[0049] In this embodiment, the first inductor L1 and the second inductor L2 are used to cancel the current ripple on the low-voltage side. The third inductor L3 is used to maintain the continuous current on the high-voltage side.

[0050] The following section provides a detailed explanation of the four operating models of the non-isolated bidirectional DC-DC converter. Figure 2 , Figure 3 , Figure 4 and Figure 5 The solid black lines represent the components required in the current operating state, the dashed black lines represent the current path in the current operating state, and the solid gray lines represent components not included in the current operating state.

[0051] First operating mode (boost):

[0052] like Figure 2 As shown, in this operating mode, the first switch S1 and the second switch S2 maintain a high level, while the third switch Q1 and the fourth switch Q2 (which are synchronous rectifiers at this time) maintain a low level. The low-voltage side input power supply V... LV Power is supplied to the first inductor L1 through the conducting first switch S1, and the first inductor L1 begins to store energy. Simultaneously, the energy in the first capacitor C1 is transferred to the second inductor L2, realizing energy transfer in the intermediate stage. Furthermore, the third inductor L3 on the output side and the high-voltage load R... HV The required energy is obtained through the second capacitor C2 to maintain the stability of the high-voltage side power supply.

[0053] The second operating mode (boost):

[0054] like Figure 3 As shown, in this operating mode, the first switch S1 and the second switch S2 remain at a low level, while the complementary switches of the third switch Q1 and the fourth switch Q2 remain at a high level. During this period, each inductor releases its previously stored energy, transferring it to the capacitor and the high-voltage side R, respectively. HV The load provides power, enabling the transfer of energy from the intermediate stage to the output stage.

[0055] The third working mode (voltage reduction):

[0056] like Figure 4 As shown, in this operating mode, the third switch Q1 and the fourth switch Q2 remain at a high level, while the first switch S1 and the second switch S2 (which are synchronous rectifiers at this time) remain at a low level. During this period, each inductor obtains energy from the high-voltage power supply and the capacitor in the circuit, and stores the energy in the magnetic field, preparing for energy release in subsequent operating stages.

[0057] The fourth operating mode (step-down):

[0058] like Figure 5As shown, in this operating mode, the third switch Q1 and the fourth switch Q2 remain at a low level, while the complementary switches of the first switch S1 and the second switch S2 remain at a high level. During this period, each inductor releases its stored energy to the capacitor in the circuit and the high-voltage side load R. HV This enables the output and transfer of energy.

[0059] The rated output power of this non-isolated bidirectional DC-DC converter is 150W. The rated output power refers to the maximum power value that the non-isolated bidirectional DC-DC converter can stably output under the standard operating conditions (36V low voltage side, 110V high voltage side and 20kHz N-channel MOSFET switching frequency), whether in boost mode (low voltage → high voltage) or buck mode (high voltage → low voltage).

[0060] This novel non-isolated bidirectional DC-DC converter utilizes a collaborative working mechanism of inductors (first inductor L1, second inductor L2, and third inductor L3), switching transistors (first switch S1, second switch S2, third switch Q1, and fourth switch Q2), and capacitors (first capacitor C1, second capacitor C2, and second capacitor C3). By matching the parameters of the first inductor L1 and the second inductor L2, and combining a synchronous rectification strategy of the switching transistors (first switch S1, second switch S2, third switch Q1, and fourth switch Q2), it achieves high step-down gain from the high-voltage side to the low-voltage side during charging and high step-up gain from the low-voltage side to the high-voltage side during discharging within a single power conversion stage. This novel non-isolated bidirectional DC-DC converter utilizes the principle of reverse cancellation of inductor current (inductor current on the low-voltage side) to significantly reduce or even eliminate current ripple on the battery side (low-voltage side), improving system stability. Moreover, this novel non-isolated bidirectional DC-DC converter uses relatively few switching devices (4 switching transistors).

[0061] This novel non-isolated bidirectional DC-DC converter topology not only optimizes device voltage stress but also reduces inductor losses, adapts to renewable energy voltage fluctuations and battery energy storage charging and discharging requirements, improves overall power conversion efficiency, and helps the stable operation and flexible energy regulation of high-proportion renewable energy grids.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of this utility model. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this utility model should be covered within the protection scope of the claims of this utility model.

Claims

1. A non-isolated bidirectional DC-DC converter, characterized in that, It includes an input filter circuit, a main power conversion circuit, and an output filter circuit; The input filtering circuit includes an input power supply, a first inductor, and a third capacitor; the main power conversion circuit includes a first switch, a second switch, a third switch, a fourth switch, a first capacitor, a second capacitor, and a second inductor; the output filtering circuit includes an output power supply and a third inductor. The positive terminal of the input power supply is connected to one end of the third capacitor, the negative terminal of the input power supply is connected to the other end of the third capacitor, one end of the third capacitor is connected to one end of the first inductor, the other end of the first inductor is connected to the source of the third switching transistor, the other end of the third capacitor is connected to the source of the first switching transistor, the source of the first switching transistor is connected to the other end of the first capacitor, and the drain of the first switching transistor is connected to the source of the third switching transistor. One end of the first inductor is connected to one end of the second inductor, the other end of the second inductor is connected to one end of the second capacitor, the other end of the second capacitor is connected to the drain of the fourth switching transistor, one end of the second capacitor is connected to the source of the second switching transistor, the drain of the second switching transistor is connected to one end of the first capacitor, and the drain of the third switching transistor is connected to the source of the fourth switching transistor. The drain of the fourth switching transistor is connected to one end of the third inductor, the other end of the third inductor is connected to the positive terminal of the output power supply, and the other end of the first capacitor is connected to the negative terminal of the output power supply.

2. The non-isolated bidirectional DC-DC converter according to claim 1, characterized in that, The first, second, third, and fourth switching transistors are all N-channel MOSFETs.

3. The non-isolated bidirectional DC-DC converter according to claim 1, characterized in that, The first inductor, the second inductor, and the third inductor are all ferrite core inductors.

4. The non-isolated bidirectional DC-DC converter according to claim 1, characterized in that, The first and second capacitors are both polarized electrolytic capacitors, and the third capacitor is a filter capacitor.

5. The non-isolated bidirectional DC-DC converter according to claim 1, characterized in that, The first inductor has a size of 600μH-800μH, the second inductor has a size of 600μH-1000μH, and the third inductor has a size of 800μH-1200μH.

6. The non-isolated bidirectional DC-DC converter according to claim 1, characterized in that, The first capacitor, the second capacitor, and the third capacitor all have a value of 100μF-400μF.

7. The non-isolated bidirectional DC-DC converter according to claim 1, characterized in that, The models of the first, second, and third inductors are not restricted.

8. The non-isolated bidirectional DC-DC converter according to claim 1, characterized in that, The models of the first capacitor, the second capacitor, and the third capacitor are not restricted.

9. The non-isolated bidirectional DC-DC converter according to claim 1, characterized in that, The input power supply is a DC power supply.

10. The non-isolated bidirectional DC-DC converter according to claim 1, characterized in that, The output power supply is a DC power supply.

Images