High-efficiency partial power transfer DC-DC converter and working method thereof

Abstract

The invention discloses a high-efficiency partial power transmission DC-DC converter and a working method thereof. The DC-DC converter comprises a DC input power supply, a first inductor, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube, a first capacitor and a second capacitor. The positive electrode of the DC input power supply is connected with the drain electrode of the first switch tube and the drain electrode of the third switch tube, and the negative electrode is connected with the source electrode of the second switch tube, the drain electrode of the fifth switch tube and the positive electrode of the second capacitor. The source electrode of the first switch tube is connected with the drain electrode of the second switch tube and the positive electrode of the first capacitor; the source electrode of the third switch tube and the drain electrode of the fourth switch tube are connected with one end of the first inductor; the source electrode of the fourth switch tube is connected with the source electrode of the fifth switch tube; the other end of the first inductor is connected with the cathode of the second capacitor; the DC input power supply and the cathode of the second capacitor are connected with two ends of the load resistor. Only one part of the total power needs to be transmitted, and the overall loss can be reduced.

Description

Technical Field

[0001] This invention relates to the technical field of new energy power generation in power grid systems, and in particular to a high-efficiency partial power transmission DC-DC converter and its operating method. Background Art

[0002] With the continuous development of renewable energy, the proportion of distributed power distribution systems is increasing. To improve the utilization rate of new energy sources, efficient and reliable grid connection solutions have become the focus of current research and industrialization. Taking DC sources such as energy storage batteries, fuel cells, or photovoltaic panels as examples, existing mainstream grid connection solutions can be broadly divided into two technical routes: "full power conversion" and "partial power conversion."

[0003] 1. Full power conversion

[0004] The traditional two-stage architecture (pre-stage DC-DC + post-stage DC-AC) still dominates the market. Although this solution has a simple structure and mature control, all power needs to go through two stages of conversion. The accumulated voltage withstand, conduction and switching losses of the devices make it difficult for the overall efficiency to exceed 95%, and the system size and cost increase linearly with the power level.

[0005] 2. Partial Power Conversion

[0006] Partial Power Processing (PPP) topologies, which have emerged in recent years, process only a small fraction of the total power, theoretically reducing losses proportionally and thus significantly improving system efficiency. However, existing PPP solutions are mostly limited to the following two approaches, resulting in a narrow technical scope and difficulty in meeting the needs of diverse application scenarios:

[0007] (1) The derived structure based on the bidirectional Buck / Boost unipolar topology can only realize the boost or buck function, and the voltage regulation range is limited;

[0008] (2) To achieve positive and negative polarity output or wide-range voltage regulation, existing technologies often employ a "multi-mode switching" control strategy—that is, switching power flow direction or topology configuration in different operating ranges. While this method expands the output range, it inevitably introduces circuit transients during mode switching, leading to:

[0009] The maximum power point tracking (MPPT) process is interrupted or oscillates, resulting in a decrease in energy capture efficiency;

[0010] The control algorithm becomes more complex, leading to reduced reliability.

[0011] Under sudden load changes or environmental disturbances, the system is prone to entering an unexpected oscillation state, which seriously affects the grid connection quality.

[0012] In summary, existing partial power transmission DC-DC conversion technologies have significant limitations in terms of functional coverage, control robustness, and dynamic response. There is an urgent need for a new topology that can achieve wide-range, bipolar output while maintaining high efficiency and high reliability without mode switching, in order to adapt to various new energy grid-connected scenarios such as energy storage, photovoltaic DC buildings, and DC microgrids. Summary of the Invention

[0013] The purpose of this invention is to overcome the shortcomings of the prior art and provide a novel partial power transfer DC-DC converter with a new topology that can achieve wide-range, bipolar output while maintaining high efficiency and high reliability.

[0014] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0015] A high-efficiency partial power transfer DC-DC converter includes a DC input power supply Vin, a first inductor L1, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a first capacitor C1, and a second capacitor C2.

[0016] The positive terminal of the DC input power supply Vin is connected to the drain of the first switch S1 and the drain of the third switch S3, and the negative terminal is connected to the source of the second switch S2, the drain of the fifth switch S5, and the positive terminal of the second capacitor C2.

[0017] The source of the first switch S1 is connected to the drain of the second switch S2 and the positive terminal of the first capacitor C1.

[0018] The source of the third switch S3 and the drain of the fourth switch S4 are connected to one end of the first inductor L1.

[0019] The source of the fourth switch S4 is connected to the source of the fifth switch S5; the other end of the first inductor L1 is connected to the negative terminal of the second capacitor C2.

[0020] The DC input power supply Vin is connected to the two ends of the load resistor via the negative terminal of the second capacitor C2.

[0021] Furthermore, the present invention also provides a method for operating the above-mentioned high-efficiency partial power transfer DC-DC converter, comprising:

[0022] During stage t0 to t1, the first, third, and fifth switching transistors S1, S3, and S5 begin to conduct under the action of the drive signal; the DC input power supply Vin charges the first inductor L1 and the first capacitor C1; the current iL1 increases linearly, and VC1 is charged until it is equal to the voltage of Vin; the DC input power supply Vin and the second capacitor C2 together discharge to the load R.

[0023] During stages t1 to TS, the first, third, and fifth switching transistors S1, S3, S5 are turned off, and the second and fourth switching transistors S2, S4 start to conduct under the action of the driving signals; the first capacitor C1 discharges to the first inductor L1, the current iL1 decreases linearly, and VC1 decreases; the DC input power supply Vin and the second capacitor C2 together discharge to the load R; when the driving signals for the first, third, and fifth switching transistors S1, S3, S5 arrive in the next cycle, this stage ends.

[0024] Furthermore, the above-mentioned high-efficiency partial power transfer DC-DC converter only requires a set of complementary driving signals and is easy to control.

[0025] Furthermore, the second capacitor of the above-mentioned high-efficiency partial power transfer DC-DC converter realizes positive and negative polarity output by adjusting the duty cycle of the driving signal, without changing the working logic of the switching transistors.

[0026] Compared with the prior art, the principles and advantages of the present technical solution are as follows:

[0027] 1. The converter adopts the concept of partial power transfer and only needs to transfer a part of the total power, which can reduce the overall loss.

[0028] 2. The converter can realize the positive and negative polarity output of the second capacitor only by adjusting the duty cycle of the driving signal, without changing the working logic of the switching transistors, avoiding the influence brought by transient disturbances.

[0029] 3. The converter is a non-isolated structure and only uses one magnetic device, which can further reduce the loss.

[0030] 4. In the same duty cycle range of 0 < d < 1, the present converter can continuously output positive and negative bidirectional voltages without any working logic or topology reconstruction, and both step-up and step-down can be covered; experimental verification shows that it can stably operate under multiple extreme working conditions such as 30V → ±40V, 45V → ±5V, etc., truly breaking through the narrow range bottleneck caused by "step-up / step-down segmentation" or "positive / negative switching" of the existing PPP scheme.

[0031] 5. Due to the absence of mode switching, the system does not need to re-optimize MPPT during load mutation, input step or energy storage module switching, the dynamic response time < 200μs, and there will be no "self-locking" or "oscillation" phenomena common in the prior art (comparison Figure 8 、 Figure 9 ), further ensuring high efficiency and high reliability under wide range operation. Description of the Drawings

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the services required in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a circuit diagram of the high-efficiency partial power transfer DC-DC converter of the present invention;

[0034] Figure 2 The voltage and current waveforms of the main components in the high-efficiency partial power transfer DC-DC converter of this invention are shown in the diagram.

[0035] Figure 3 One of the circuit mode diagrams during one switching cycle of the circuit;

[0036] Figure 4 The second circuit mode diagram within one switching cycle of the circuit;

[0037] Figure 5 The voltage gain curve of the high-efficiency partial power transfer DC-DC converter of this invention is shown.

[0038] Figure 6 This is a waveform diagram of the high-efficiency partial power transfer DC-DC converter of the present invention under positive polarity output;

[0039] Figure 7 The experimental waveform diagram of the high-efficiency partial power transfer DC-DC converter of the present invention under negative polarity output is shown.

[0040] Figure 8 This is the transient waveform of the high-efficiency partial power transfer DC-DC converter of the present invention under environmental changes;

[0041] Figure 9 This represents the transient waveform of an existing converter under environmental changes. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments:

[0043] like Figure 1 As shown, the high-efficiency partial power transfer DC-DC converter described in this embodiment includes a DC input power supply Vin, a first inductor L1, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a first capacitor C1, and a second capacitor C2.

[0044] In this circuit, the positive terminal of the DC input power supply Vin is connected to the drain of the first switch S1 and the drain of the third switch S3, while the negative terminal is connected to the source of the second switch S2, the drain of the fifth switch S5, and the positive terminal of the second capacitor C2. The source of the first switch S1 is connected to the drain of the second switch S2 and the positive terminal of the first capacitor C1. The source of the third switch S3 and the drain of the fourth switch S4 are connected to one end of the first inductor L1. The source of the fourth switch S4 is connected to the source of the fifth switch S5. The other end of the first inductor L1 is connected to the negative terminal of the second capacitor C2. The DC input power supply Vin and the negative terminal of the second capacitor C2 are connected across the load resistor. The converter can output both positive and negative polarity voltages from the second capacitor by changing the duty cycle of the switch drive signal.

[0045] The steady-state analysis of the high-efficiency partial power transfer DC-DC converter described in this embodiment operating in complementary conduction mode is as follows:

[0046] 1) Modal analysis

[0047] Figure 2 Draw the waveforms of the main components of the circuit under stable operation in complementary conduction mode. VGS1,3,5 represent the drive signals for the first, third, and fifth switches S1, S3, and S5; VGS2 represents the drive signals for the second and fourth switches S2 and S4; iL1 represents the current flowing through the first inductor L1; and VC1 and VC2 represent the voltages across the first capacitor C1 and the second capacitor C2, respectively.

[0048] The following will combine Figure 3 A detailed analysis of the circuit's operating state is conducted:

[0049] a. Stages t0~t1 are as follows Figure 3 During this stage, the first, third, and fifth switching transistors S1, S3, and S5 begin to conduct under the influence of the drive signal. The DC input power supply Vin charges the first inductor L1 and the first capacitor C1. Therefore, the current iL1 increases linearly, and VC1 charges until it equals the voltage of Vin. The DC input power supply Vin and the second capacitor C2 together discharge to the load R.

[0050] b. Stages t1 to TS, as follows Figure 4 During this phase, the first, third, and fifth switches S1, S3, and S5 are turned off, while the second and fourth switches S2 and S4 begin to conduct under the influence of the drive signal. The first capacitor C1 discharges through the first inductor L1, thus the current iL1 decreases linearly, and VC1 decreases. The DC input power supply Vin and the second capacitor C2 together discharge through the load R. This phase ends when the drive signal for the first, third, and fifth switches S1, S3, and S5 arrives for the next cycle.

[0051] 2) Voltage gain analysis

[0052] To simplify the analysis of converter voltage gain, we first define (a) and make assumptions (b, c):

[0053] a. Duty cycle Where TS is the circuit's operating cycle, and Ton is the conduction time of the first switch S1, that is, the time during which the drive signal of the first switch S1 is at a high level.

[0054] b. All devices are ideal devices;

[0055] c. The capacitance is large enough that the voltage across the capacitor remains constant during the switching cycle.

[0056] For the period t0~dTS, Kirchhoff's Voltage Law (KVL) can be used to obtain:

[0057] v L1(on) =V in +V C2 (1)

[0058] V C1 =V in (2)

[0059] Where v L1(on) This is the voltage across the first inductor L1 when the first switch S1 is turned on.

[0060] The phase dTS~TS can be obtained from Kirchhoff's Voltage Law (KVL):

[0061] v L1(off) =-V C1 +V C2 (3)

[0062] Where v L1(off) This is the voltage across the first inductor L1 when the first switch S1 is turned off.

[0063] Under steady-state conditions, the volt-second balance condition can be used to obtain the following for the first inductor L1:

[0064]

[0065] By combining several formulas, the voltage across the second capacitor C2 can be obtained:

[0066] V C2 = (1-2d)·V in (5)

[0067] According to formula (5), by adjusting the value of d, the positive and negative bipolar output of the second capacitor can be achieved (d<0.5 is positive output, d>0.5 is negative output).

[0068] Furthermore, the expression for the output voltage gain can be obtained, and the specific curve is as follows: Figure 5 As shown:

[0069] M = V O / V in =2·(1-d)·V in (6)

[0070] Overall, it can be seen that by changing the duty cycle, the output voltage can be raised or lowered without changing the switching logic of the converter. Therefore, no unpredictable operating states will occur when the system is disturbed.

[0071] The high-efficiency partial power transfer DC-DC converter of this invention is now experimentally verified. The parameters of each component are shown in Table 1.

[0072] Table 1. Parameters of the converter

[0073] project Parameter value DC input power supply Vin voltage / V 30-50 DC output voltage VO voltage / V 40 Operating frequency of all switching transistors / kHz 50 First inductor L1 / H 150 First capacitor C1, second capacitor C2 / F 50 Load power PO / W 0～500W

[0074] like Figure 6 As shown, with the duty cycle d of the first switch S1 set to approximately 0.33, the input voltage 30V, and the output voltage VO 40V, the converter operates stably as expected. At this time, the second capacitor C2 outputs positive voltage (10V, consistent with the analysis); the waveform flowing through the first inductor L1 shows linear rise and fall in each mode, as analyzed above. Figure 7 As shown, with the duty cycle d of the first switch S1 set to approximately 0.55, the input voltage 45V, and the output voltage VO 40V, the converter operates stably as expected. At this time, the second capacitor C2 outputs negative voltage (-5V, consistent with the analysis). The waveform flowing through the first inductor L1 shows linear rise and fall in each mode, as analyzed above. Therefore, the bipolar output capability of the converter under the same operating logic is verified.

[0075] like Figure 8 The figure shows the transient waveforms of the converter during the switching of some energy storage modules. It can be seen that after switching, the system can smoothly switch to the new MPP without significant unexpected disturbances. For comparison, Figure 9 The transient waveforms of the existing multi-state bipolar output power converter under the same conditions are shown. It can be seen that after switching, the system will enter an unexpected and unfade-attenuated disturbance state. The system cycles between the two operating states, and the input voltage will "lock" itself near the set output voltage and will not be able to track the new MPP again.

[0076] In summary, the theoretical analysis and simulation results consistently verify the circuit's bipolar output function and robustness against disturbances. Therefore, the DC-DC converter of this invention can be used in various new energy grid-connected applications to achieve high efficiency and high robustness. The embodiments described above are merely preferred embodiments of this invention and are not intended to limit the scope of the invention. Therefore, all variations made according to the shape and principle of this invention should be covered within the protection scope of this invention.

Claims

1. A high-efficiency partial power transfer DC-DC converter, characterized in that, It includes a DC input power supply Vin, a first inductor L1, a first switching transistor S1, a second switching transistor S2, a third switching transistor S3, a fourth switching transistor S4, a fifth switching transistor S5, a first capacitor C1, and a second capacitor C2; The positive terminal of the DC input power supply Vin is connected to the drain of the first switch S1 and the drain of the third switch S3, and the negative terminal is connected to the source of the second switch S2, the drain of the fifth switch S5, and the positive terminal of the second capacitor C2. The source of the first switch S1 is connected to the drain of the second switch S2 and the positive terminal of the first capacitor C1. The source of the third switch S3 and the drain of the fourth switch S4 are connected to one end of the first inductor L1. The source of the fourth switch S4 is connected to the source of the fifth switch S5; the other end of the first inductor L1 is connected to the negative terminal of the second capacitor C2. The DC input power supply Vin is connected to the two ends of the load resistor via the negative terminal of the second capacitor C2.

2. A method for operating the high-efficiency partial power transfer DC-DC converter as described in claim 1, characterized in that, include: During stage t0 to t1, the first, third, and fifth switching transistors S1, S3, and S5 begin to conduct under the action of the drive signal; the DC input power supply Vin charges the first inductor L1 and the first capacitor C1; the current iL1 increases linearly, and VC1 is charged until it is equal to the voltage of Vin; the DC input power supply Vin and the second capacitor C2 together discharge to the load R. During phases t1 to TS, the first, third, and fifth switches S1, S3, and S5 are turned off, while the second and fourth switches S2 and S4 begin to conduct under the action of the drive signal; the first capacitor C1 discharges to the first inductor L1, and the current iL1 decreases linearly, thus decreasing VC1; the DC input power supply Vin and the second capacitor C2 together discharge to the load R; this phase ends when the drive signal for the first, third, and fifth switches S1, S3, and S5 of the next cycle arrives.

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