A Bipolar Self-Equalizing DC-DC Converter Based on Magnetic Integration and an Optimization Method for Soft Switching

Abstract

This invention relates to a bipolar self-equalizing DC-DC converter based on magnetic integration and a soft-switching optimization method. It includes two full-bridge circuits, a four-winding transformer, and a voltage-balanced coupling inductor. The first full-bridge circuit outputs two voltages, which are respectively input to the first and second primary windings of the four-winding transformer. One end of the first and second secondary windings of the four-winding transformer is connected to the midpoints of the first and second arms of the second full-bridge circuit, respectively. The other ends of the first and second secondary windings of the four-winding transformer are connected to one end of the primary and secondary windings of the voltage-balanced coupling inductor, respectively. The other ends of the primary and secondary windings of the voltage-balanced coupling inductor are also connected to one end of a first load and one end of a second load. This invention enables all power semiconductor devices to achieve zero-voltage switching characteristics.

Description

Technical Field

[0001] This invention belongs to the technical field of bipolar self-equalizing DC-DC converters, and more specifically, relates to a magnetically integrated bipolar self-equalizing DC-DC converter and a soft-switching optimization method. Background Technology

[0002] Photovoltaic (PV) power generation systems are deployed on a large scale. However, the excessive output current ripple of PV arrays significantly reduces their lifespan. Therefore, DC-DC converters with low input current ripple are essential in PV power generation systems. However, traditional zero-input-current-ripple converters require multiple sets of discrete inductors and filter capacitors, which greatly reduces the system's power density. It is worth noting that novel bipolar DC microgrids offer significant advantages over traditional unipolar architectures in terms of efficiency, reliability, transmission capacity, and security, enabling the application of PV power generation systems in bipolar DC distribution networks. However, unbalanced load connections can lead to voltage imbalance between the two poles. The literature (W. Wang, Y. Wang, Y. Guan, T. Yao, Y. Wang and D. Xu, "A Family of Impedance Source DC-DC Converters With Zero Input Current Ripple," in IEEE Transactions on Industrial Electronics, vol. 70, no. 9, pp. 8883-8894) proposes a series of impedance-source DC-DC converters with zero input current ripple. Ripple-free control is achieved by designing the number of turns of the coupling inductor and the input inductor; however, these converters have unipolar output and low reliability. Furthermore, the switching is hard-turn-off, resulting in high switching losses. The literature (D. Sha, Y. Xu, J. Zhang and Y. Yan, "Current-Fed Hybrid Dual Active Bridge DC–DC Converter for a Fuel Cell PowerConditioning System With Reduced Input Current Ripple," in IEEE Transactions on Industrial Electronics, vol. 64, no. 8, pp. 6628-6638) proposes a current-mode dual active bridge DC-DC converter that achieves zero input current ripple through two-phase interleaved inductors, but it contains two large inductors and has low power density. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a bipolar self-equalizing DC-DC converter based on magnetic integration and a soft-switching optimization method.

[0004] The present invention adopts the following technical solution.

[0005] The first aspect of this invention proposes a bipolar self-equalizing DC-DC converter based on magnetic integration, comprising two full-bridge circuits and a four-winding transformer. T r Voltage-balanced coupling inductor T c Specifically:

[0006] The input terminal of the first full-bridge circuit is connected to the input voltage. The first full-bridge circuit outputs two output voltages, which are respectively input to the four-winding transformer. T r The primary winding 1 and primary winding 2, a four-winding transformer T r One end of the first winding and one end of the second winding of the secondary side are connected to the midpoint of the first bridge arm and the midpoint of the second bridge arm of the second full-bridge circuit, respectively. (This is the structure of the four-winding transformer.) T r The other ends of the first and second secondary windings are respectively connected to the voltage-balanced coupling inductor. T c One end of the primary winding and one end of the secondary winding are connected together, forming a voltage-balanced coupled inductor. T c The other end of the primary winding and the other end of the secondary winding are connected to one end of the first load and one end of the second load, respectively. The other ends of the first load and the other ends of the second load are connected to the two parallel points of the two arms of the second full-bridge circuit.

[0007] Preferably, the first full-bridge circuit and the four-winding transformer T r First primary magnetizing inductor L m1 With the second primary excitation inductor L m2 To form a two-level interleaved full-bridge circuit, the first primary-side magnetizing inductor L m1 With the second primary excitation inductor L m2 The series structure is connected in parallel with the two arms of the first full-bridge circuit, and the positive terminal of the input voltage is connected to the first primary magnetizing inductor. L m1 With the second primary excitation inductor L m2 The connection point is connected, and the negative terminal of the input voltage is connected to the midpoint of the first bridge arm of the first full-bridge circuit.

[0008] Preferably, the self-equalizing DC-DC converter further includes a clamping capacitor. C c Clamping capacitor C c It connects between the midpoint of the first bridge arm and the midpoint of the second bridge arm of the first full-bridge circuit.

[0009] Preferably, the clamping capacitor C c The voltage across the terminals is constant at twice the input voltage.

[0010] Preferably, the self-equalizing DC-DC converter further includes a first bipolar output capacitor. C o1 Second bipolar output capacitor C o2 First bipolar output capacitor C o1 The second bipolar output capacitor C is connected in parallel with the first load. o2 It is connected in parallel with the second load.

[0011] Preferably, the voltage-balanced coupling inductor T c The turns ratio is 1:1; the four-winding transformer T r The turns ratio of the primary winding, the second winding, and the secondary winding is: n : n :1, n This is the set value.

[0012] Preferably, the voltage-balanced coupling inductor T c Its primary and secondary windings adopt an orthogonal symmetrical layout. The primary and secondary windings are integrated into the core column through a twisted-pair winding process. The core adopts an EE-type core structure. The combined magnetic flux generated by the primary and secondary windings... Φ c A closed loop is formed along the central column of the magnetic core.

[0013] Preferably, a four-winding transformer T r The magnetic core adopts an EE-type magnetic core structure. The first and second primary windings are symmetrically arranged on the double-sided columns of the magnetic core. A distributed air gap structure of a set length is set in the magnetic circuit where each winding is located. The central column of the magnetic core maintains a gapless structure. The difference between the magnetic reluctance value of the double-sided columns and the magnetic reluctance value of the central column of the magnetic core exceeds the set magnetic reluctance threshold. The first and second secondary windings are arranged in the central column of the magnetic core using an orthogonal winding process.

[0014] A second aspect of the present invention proposes a soft-switching optimization method for the magnetically integrated bipolar self-equalizing DC-DC converter described in the first aspect of the present invention, comprising:

[0015] The self-equalizing DC-DC converter uses a switching cycle as a set value. T s The phase-shift control strategy involves complementary drive signals for the switching transistors on the same bridge arm of the first and second full-bridge circuits, with both signals using a fixed duty cycle. Furthermore, the drive timing of the upper switching transistor on the first bridge arm of the first full-bridge circuit leads the drive timing of the upper switching transistor on the first bridge arm of the second full-bridge circuit by a certain time. ,in D φ To determine the phase shift duty cycle, power closed-loop control is used. D φ .

[0016] The beneficial effects of this invention are compared with those of the prior art:

[0017] 1. This converter integrates the interleaved inductance in the traditional topology into a four-winding transformer through magnetic integration technology. This design not only improves power density but also significantly reduces the size of the device.

[0018] 2. The primary side of the converter adopts a two-phase interleaved full-bridge structure, and zero input current ripple is achieved by using pulse drive with a fixed duty cycle of 0.5.

[0019] 3. The secondary side of this converter uses a tightly coupled voltage-balancing inductor to achieve bipolar voltage balancing under any load conditions;

[0020] 4. This converter can achieve high voltage gain while enabling all power semiconductor devices to achieve zero-voltage switching (ZVS) characteristics, thereby significantly reducing switching losses and improving system efficiency. Attached Figure Description

[0021] Figure 1 This is a circuit diagram of a bipolar self-equalizing DC-DC converter based on magnetic integration.

[0022] Figure 2 The current path diagram is shown when the second and third switches begin to turn off.

[0023] Figure 3 The current path diagram is shown when the first and fourth switching transistors are turned on.

[0024] Figure 4 The current path diagram is shown when the sixth and seventh switches begin to turn off.

[0025] Figure 5 The current path diagram is shown when the fifth and eighth switches are turned on.

[0026] Figure 6 The main waveform diagram of the converter;

[0027] Figure 7 The equivalent circuit diagram of the converter;

[0028] Figure 8 The voltage deviation diagram shows the voltages with different coupling coefficients and leakage inductance ratios.

[0029] Figure 9 This is a graph showing the relationship between per-unit power and phase shift duty cycle.

[0030] Figure 10 This is a waveform diagram of the transformer current under unbalanced load conditions.

[0031] Figure 11 For different coefficients and wide voltage gain M Schematic diagram of the zero-voltage switching region;

[0032] Figure 12 This is a diagram of a voltage-balanced coupled inductor structure.

[0033] Figure 13 This is a structural diagram of a four-winding transformer. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0035] like Figure 1 As shown, Embodiment 1 of the present invention proposes a bipolar self-equalizing DC-DC converter based on magnetic integration, including two full-bridge circuits and a four-winding transformer. T r Voltage-balanced coupling inductor T c Specifically:

[0036] The input terminals and input voltage of the first full-bridge circuit V in Connected, the first full-bridge circuit outputs two voltages, which are then input to the four-winding transformer. T r The primary winding 1 and primary winding 2, a four-winding transformer T r One end of the first winding and one end of the second winding of the secondary side are connected to the midpoint of the first bridge arm and the midpoint of the second bridge arm of the second full-bridge circuit, respectively. (This is the structure of the four-winding transformer.) T r The other ends of the first and second secondary windings are respectively connected to the voltage-balanced coupling inductor.T c One end of the primary winding and one end of the secondary winding are connected together, forming a voltage-balanced coupled inductor. T c The other end of the primary winding, the other end of the secondary winding, and the first load R o1 One end, the second load R o2 One end of each load is connected, the first load R o1 The other end, the second load R o2 The other end is connected to the two parallel points of the two arms of the second full-bridge circuit.

[0037] Specifically, in this embodiment, the first full-bridge circuit is the first switching transistor. Q 1. Second switching transistor Q 2. Third switching transistor Q 3. Fourth switching transistor Q The bridge structure consists of 4 components;

[0038] The second full-bridge circuit uses the fifth switching transistor. Q 5. Sixth switching transistor Q 6. Seventh switching transistor Q 7. Eighth switching transistor Q The full-bridge structure consists of 8 windings; preferably in this embodiment, the first full-bridge circuit and the four-winding transformer... T r First primary magnetizing inductor L m1 With the second primary excitation inductor L m2 To form a two-level interleaved full-bridge circuit, the first primary-side magnetizing inductor L m1 With the second primary excitation inductor L m2 The series structure is connected in parallel with the two arms of the first full-bridge circuit, and the positive terminal of the input voltage is connected to the first primary magnetizing inductor. L m1 With the second primary excitation inductor L m2 The connection point is connected, and the negative terminal of the input voltage is connected to the midpoint of the first bridge arm of the first full-bridge circuit.

[0039] In this preferred embodiment, the self-equalizing DC-DC converter further includes a clamping capacitor. C c Clamping capacitor C c It connects between the midpoint of the first bridge arm and the midpoint of the second bridge arm of the first full-bridge circuit.

[0040] In this preferred embodiment, the clamping capacitor C c The voltage across the terminals is constant at twice the input voltage.

[0041] In a preferred embodiment, the self-equalizing DC-DC converter further includes a first bipolar output capacitor. C o1 Second bipolar output capacitor C o2 First bipolar output capacitor C o1 The second bipolar output capacitor C is connected in parallel with the first load. o2 It is connected in parallel with the second load.

[0042] In this preferred embodiment, the voltage-balanced coupling inductor T c The turns ratio is 1:1; the four-winding transformer T r The turns ratio of the primary winding, the second winding, and the secondary winding is: n : n :1, n This is the set value.

[0043] In this preferred embodiment, the voltage-balanced coupling inductor T c Its primary and secondary windings adopt an orthogonal symmetrical layout. The primary and secondary windings are integrated into the core column through a twisted-pair winding process. The core adopts an EE-type core structure. The combined magnetic flux generated by the primary and secondary windings... Φ c A closed loop is formed along the central column of the magnetic core.

[0044] In this preferred embodiment, a four-winding transformer is used. T r The magnetic core adopts an EE-type magnetic core structure. The first and second primary windings are symmetrically arranged on the double-sided columns of the magnetic core. A distributed air gap structure of a set length is set in the magnetic circuit where each winding is located. The central column of the magnetic core maintains a gapless structure. The difference between the magnetic reluctance value of the double-sided columns and the magnetic reluctance value of the central column of the magnetic core exceeds the set magnetic reluctance threshold. The first and second secondary windings are arranged in the central column of the magnetic core using an orthogonal winding process.

[0045] Embodiment 2 of the present invention proposes a soft-switching optimization method for the magnetically integrated bipolar self-equalizing DC-DC converter described in Embodiment 1 of the present invention, comprising:

[0046] The self-equalizing DC-DC converter uses a switching cycle as a set value. T sThe phase-shift control strategy involves complementary drive signals for the switching transistors on the same bridge arm of the first and second full-bridge circuits, with both signals using a fixed duty cycle. Furthermore, the drive timing of the upper switching transistor on the first bridge arm of the first full-bridge circuit leads the drive timing of the upper switching transistor on the first bridge arm of the second full-bridge circuit by a certain time. ,in D φ To determine the phase shift duty cycle, power closed-loop control is used. D φ .

[0047] The self-equalizing DC-DC converter in one switching cycle T s It can be divided into 4 switching modes, and its main waveforms are as follows: Figure 6 As shown below, the four switching modes are explained in detail.

[0048] Mode 1 ( t 0 ~t 1): The current path for this mode is as follows Figure 2 As shown. In t At time 0, the second switching transistor Q 2 and the third switching transistor Q 3. Turn off. Current i t1 and i t2 For the second switching transistor respectively Q 2 and the third switching transistor Q The junction capacitance of transistor 3 is charged, and the first switching transistor is charged accordingly. Q 1 and the fourth switching transistor Q The junction capacitance of transistor 4 is discharged until the first switching transistor... Q 1 and the fourth switching transistor Q The drain-source voltage of transistor 4 decays to zero. Subsequently, the first switching transistor... Q 1 and the fourth switching transistor Q The body diode of transistor 4 will conduct to meet the soft-switching conditions for the next stage. In this stage, the sixth switching transistor... Q 6 and 7 switch transistors Q 7 is in the on state, node C and O voltage between v CO and nodes O and Voltage between D v OD The negative second output voltages are respectively –V o2 and negative first output voltage –V o1 , V o1 , V o2These are the first and second output voltages, i.e., the voltage of the first load and the voltage of the second load.

[0049] Mode 2 ( t 1~ t 2): The current path for this mode is as follows Figure 3 As shown. In t At time 1, the first switching transistor Q 1 and the fourth switching transistor Q 4. Activated, node in the diagram AK Two-point voltage v AK = V in –V Cc = – V in ,in V in Input voltage, V Cc This is the clamping capacitor voltage; KB Two-point voltage v KB equal V in In this mode, the four-winding transformer T r Current on the first and second primary magnetizing inductors i Lm1 , i Lm2 For linear decreases and increases, the formulas are:

[0050]

[0051]

[0052] In the formula, and They are respectively t Time and t The current in the first primary magnetizing inductor at time 1; , They are respectively t Time and t The current in the second primary magnetizing inductor at time 1.

[0053] At this time, the four-winding transformer T r Secondary winding voltages of the first and second windings v s1 and v s2 for- V in / n Due to the sixth switchQ 6 and 7 Q 7 is still open. v CO and v OD Keep each –V o2 and –V o1 According to KVL, voltage-balanced coupled inductors T c The self-inductance of the primary and secondary windings L 1 and L Voltage across 2 v L1 and v L2 Represented as:

[0054]

[0055]

[0056] Therefore, voltage-balanced coupled inductors T c Secondary winding first and second winding current i s1 and i s2 The expressions for the rapid linear rise and fall are as follows:

[0057]

[0058]

[0059] In the formula, , They are respectively t Time and t The current in the first winding of the secondary side at time 1; , They are respectively t Time and t The secondary winding current at time 1.

[0060] like Figure 6 As shown, based on the turns ratio of a four-winding transformer, the currents in its primary winding (first and second windings) can be determined. i p1 and i p2 The expressions are as follows:

[0061]

[0062] In the formula, , They are respectivelyt The current in the primary winding and the second winding at any given moment.

[0063] Voltage-balanced coupled inductor T c Self-equalizing pressure control was implemented, i.e. V o1 = V o2 Because the formula for input current is:

[0064]

[0065] Based on the above formula and the symmetry of the inductor current waveform, the input current can be determined. I in It is a constant value, and the current ripple is zero.

[0066] Modal 3 ( t 2~ t 3): The current path for this mode is as follows Figure 4 As shown. In t At time 2, the sixth switch transistor Q 6 and 7 switch transistors Q 7. Turn off. i s1 and i s2 To each Q 6 and Q Charge the junction capacitance of 7, and respectively... Q 5 and Q The junction capacitance of 8 is discharged until... Q 6 and Q The drain-source voltage of 7 decays to zero. Then, Q 6 and Q The body diode of 7 will conduct to satisfy the soft-switching conditions for the next stage. In this stage, v CO from- V o2 Growth to V o1 , v OD from- V o1 Growth to V o2 , v AK and v KB Still remain – V in and V in .

[0067] Modal 4 ( t 3~t 4): The current path for this mode is as follows Figure 5 As shown. In t At time 1, the fifth switch transistor Q 5 and the eighth switch Q 8 open, nodes CO Two-point voltage v CO for V o1 , OD Two-point voltage v OD for V o2 At this stage, due to the first switching transistor Q 1 and the fourth switching transistor Q 4 is still open. v AK and v KB Consistent with mode two, therefore, the four-winding transformer at this time... T r Current on the first and second primary magnetizing inductors i Lm1 , i Lm2 The formula is:

[0068]

[0069]

[0070] In the formula, , respectively t The currents on the first and second primary magnetizing inductors at time 3.

[0071] Self-awareness L 1. L 2. Voltage at both ends v L1 and v L2 They are represented as follows:

[0072]

[0073]

[0074] Therefore, four-winding transformer T r Current of the first and second secondary windings i s1 and i s2 They begin to rise and fall slowly and linearly, respectively, and their expressions are as follows:

[0075]

[0076]

[0077] In the formula, , respectively t The current of the first secondary winding and the current of the second secondary winding at time 3.

[0078] Similarly, based on the turns ratio of a four-winding transformer, the currents in its primary winding (first and second windings) can be determined. i p1 and i p2 The expressions are as follows:

[0079]

[0080] In the formula, , They are respectively t The current in the primary winding and the second winding at any given moment.

[0081] Voltage-balanced coupled inductor T c Self-equalizing pressure control was implemented, i.e. V o1 = V o2 Because the formula for input current is:

[0082]

[0083] Based on the above formula and the symmetry of the inductor current waveform, the input current can be determined. I in It is a constant value, and the current ripple is zero.

[0084] Voltage imbalance is mainly caused by load current mismatch, especially when one side is unloaded while the other is fully loaded, the imbalance will be further aggravated. In addition, four-winding transformers... T r Differences in leakage inductance on the secondary side can also lead to deterioration of voltage balance performance. This is when considering the leakage inductance of the first and second secondary windings. L 3k , L 4k In this case, the equivalent circuit of the self-equalizing DC-DC converter is as follows: Figure 7 As shown. Voltage-balanced coupled inductor. T c Mutual induction is M According to Faraday's law of electromagnetic induction, v L1 , v L2The expression is:

[0085]

[0086] In practice, voltage-balanced coupling inductors are not ideal, therefore the coupling coefficient... k The coupling coefficient may be less than 1. ,when L 1 = L At 2 o'clock, We can conclude that:

[0087]

[0088] according to Figure 7 The equivalent circuit of the self-equalizing DC-DC converter can be obtained as follows:

[0089]

[0090] Derivation V o2 / V o1 The expression is:

[0091]

[0092] Therefore, when the voltage balances the coupling inductor T c Fully coupled ( k =1), and the leakage inductance on the secondary side is equal ( L 3k = L 4k When the output load is constant, the bipolar output voltage is always automatically balanced. Figure 8 Demonstrates DC-DC converters with different coupling coefficients k Compared to leakage inductance L 4k / L 3k voltage deviation V o2 / V o1 When leakage inductance is relatively small, a higher coupling coefficient can achieve better voltage balance. However, as the difference in leakage inductance increases, even with a very high coupling coefficient, the voltage balancing effect decreases rapidly. For example, when... L 4k / L 3k When = 4, even k The voltage imbalance is as high as 0.995, and the voltage unbalance is as high as 39.8%.

[0093] Depend on Figure 6 As shown, based on the current of the first winding on the secondary side of the four-winding transformer...i s1 The symmetry gives us:

[0094]

[0095]

[0096] in, t 0 is the second switching transistor Q 2 and the third switching transistor Q 3. The moment of shutdown; for t Second switching transistor after time 0 Q 2 and the third switching transistor Q 3. The moment when it is shut down again;

[0097] Combining the above equations, we get:

[0098]

[0099]

[0100] The converter's transmission power expression can be obtained. for:

[0101]

[0102] in, The fifth switching transistor Q 5 and the eighth switch Q 8. The moment of shutdown; for Figure 1 The voltage between the C and E terminals; f s This refers to the switching frequency. Therefore, once the input and output voltages, turns ratio, voltage balance coupling inductor self-inductance, and switching frequency of the topology are determined, its power transmission is solely determined by the phase-shift duty cycle. Related. To better illustrate their relationship, a reference power is defined. for:

[0103]

[0104] Define parameters k 1= V in / nV o1 The per-unit power P ∗ The expression is:

[0105]

[0106] The per-unit power is the current power divided by the rated power value.

[0107] Figure 9 For different k 1-value subscript unit power P ∗ With phase shift duty cycle The graph shows a one-to-one correspondence between transmission power and phase shift duty cycle. Furthermore, under the same load conditions, a higher voltage gain results in lower transmission power for the same phase shift duty cycle. Based on these relationships, this invention can achieve linear adjustment of output power by employing a single-phase shift control strategy, thereby meeting the power control requirements of different application scenarios.

[0108] Before the drive signal arrives, the drain-source voltage of the switching transistor decays to zero, and its body diode begins to conduct. Subsequently, the switch can achieve zero-voltage turn-on (ZVS). Therefore, if the dead time is ignored, whether the switch can achieve ZVS depends only on the polarity of the switching transistor current at the moment of turn-on. For the ZVS range of the primary-side switching transistor, due to the isolation effect of the four-winding transformer, unbalanced loads do not affect the primary-side current and the ZVS range of the primary-side switching transistor. This is achieved by adjusting the magnetizing inductance... L m1 , L m2 With proper design, soft switching of the primary-side switching transistor can be easily achieved. In contrast, the ZVS characteristic of the secondary-side switching transistor faces a more complex operating environment. The DC bias current caused by load asymmetry will significantly change its ZVS realization boundary conditions. Figure 10 For load imbalance ( R o1 > R o2 The waveform diagram of the current of a four-winding transformer is shown. The DC components of the secondary and tertiary currents of the four-winding transformer are respectively... εI bias and –(1– ε ) I bias ,in ε This indicates the DC current on the secondary side of a four-winding transformer relative to the total bias current. I bias The proportion, whose value ranges from -1 to 1. When ε When >0, it means R o1 > R o2 ;when ε When <0, it means R o1 < R o2 .

[0109] Based on the analysis of the operating modes, the ZVS conditions of the multi-side switch are shown in Table 1.

[0110] Table 1 Instantaneous current conditions for ZVS of the fifth and sixth switches

[0111]

[0112] The analytical expressions for the ZVS conditions of the fifth and sixth switches can be obtained, as shown in Table 2. I dc This indicates the degree of load balancing, with a maximum value of 4. L 1 / T s R o1 .

[0113] Table 2 Analytical Expressions for the ZVS Conditions of the Fifth and Sixth Switches

[0114]

[0115] Figure 11 It shows the different coefficients ε Below, wide voltage gain M (= nV o1 / V in Zero-voltage switching (ZVS) region under ) where different dashed lines represent different ε The ZVS boundary of the secondary-side switch under the given conditions. It can be seen that, with... ε The increase in value, Q 6 and Q The ZVS range of 8 is reduced because of the DC bias current. I bias This provides additional energy for the charging and discharging of the switch's junction capacitance, while for Q 5 and Q The opposite is true for 8. Meanwhile, the gain curve at voltage gain (M>1) always lies within the ZVS region during actual operation. This indicates that at high voltage gain, ZVS can be achieved for all secondary-side switches regardless of the load. This characteristic significantly reduces switching losses and improves system efficiency while meeting the high boost ratio requirements of photovoltaic systems.

[0116] The voltage-balanced coupled inductor proposed in this invention T c Adopting an innovative magnetic integrated structure, such as Figure 12 As shown, its core feature lies in achieving strong magnetic coupling through the synergistic optimization of twisted-pair winding technology and EE-type magnetic core. Specifically, the primary winding... N L1 With secondary winding NL2 It adopts an orthogonal symmetrical layout and is integrated into the core column through a twisted-pair winding process, which enables the two windings to achieve a fully coupled working mode.

[0117] The voltage-balanced coupled inductor proposed in this invention T c To ensure it has a high coupling coefficient k This design uses a twisted-pair parallel winding structure to fabricate the coupled inductor winding, combined with an EE-type magnetic core structure (such as...). Figure 12 (As shown). The primary and secondary windings of the coupled inductor... N L1 , N L2 It adopts an orthogonal symmetrical layout and is integrated into the core column through a twisted-pair winding process. The resultant magnetic flux generated by the windings... Φ c A closed loop is formed along the central column, which has the characteristics of symmetrical magnetic circuit and low magnetic leakage. To prevent core saturation, an appropriate air gap is added to the central magnetic column.

[0118] The four-winding transformer proposed in this invention T r like Figure 13 As shown. Primary winding N p1 , N p2 Symmetrically arranged on both sides of the magnetic core, with each winding having a... l g The distributed air-gap structure of the length effectively improves the magnetic reluctance of the magnetic circuit and suppresses core saturation. Regarding magnetic circuit characteristics, the central column maintains a complete, air-gap-free magnetic circuit, and its reluctance is much lower than that of the two side columns, resulting in… N p1 and N p2 Magnetic flux generated by the winding Φ 1. Φ 2. It can form an independent closed loop through the central column. Based on this asymmetric magnetic circuit design, the two primary windings exhibit magnetic decoupling characteristics, successfully achieving synergistic optimization of magnetic circuit integration and electrical decoupling. Secondary winding N s1 and N s2 The windings are arranged centrally in the core using an orthogonal winding process. This arrangement ensures efficient magnetic coupling between the secondary and primary windings. Simultaneously, the magnetic flux generated by the dual primary windings... Φ 1 and Φ 2. It exhibits anti-superposition characteristics in the central column magnetic circuit. This magnetic flux phase compensation mechanism can effectively reduce the magnetic flux density amplitude in the central column region, thereby greatly reducing core loss.

[0119] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention 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 the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A bipolar self-equalizing DC-DC converter based on magnetic integration, comprising two full-bridge circuits and a four-winding transformer. T r Voltage-balanced coupling inductor T c Its features are: The input terminal of the first full-bridge circuit is connected to the input voltage. The first full-bridge circuit outputs two output voltages, which are respectively input to the four-winding transformer. T r The primary winding 1 and primary winding 2, a four-winding transformer T r One end of the first winding and one end of the second winding of the secondary side are connected to the midpoint of the first bridge arm and the midpoint of the second bridge arm of the second full-bridge circuit, respectively. (This is the structure of the four-winding transformer.) T r The other ends of the first and second secondary windings are respectively connected to the voltage-balanced coupling inductor. T c One end of the primary winding and one end of the secondary winding are connected together, forming a voltage-balanced coupled inductor. T c The other end of the primary winding and the other end of the secondary winding are connected to one end of the first load and one end of the second load, respectively. The other ends of the first load and the second load are connected to the two parallel points of the two arms of the second full-bridge circuit; the voltage balancing coupling inductor T c Its primary and secondary windings adopt an orthogonal symmetrical layout. The primary and secondary windings are integrated into the core column through a twisted-pair winding process. The core adopts an EE-type core structure. The combined magnetic flux generated by the primary and secondary windings... Φ c A closed loop is formed along the central column of the magnetic core; a four-winding transformer T r The magnetic core adopts an EE-type core structure. The first and second primary windings are symmetrically arranged on the two columns of the core. A distributed air gap structure of a set length is set in the magnetic circuit of each winding. The central column of the core maintains a gapless structure. The difference between the reluctance of the two columns and the reluctance of the central column of the core exceeds a set reluctance threshold. The first and second secondary windings are arranged in the central column of the core using an orthogonal winding process. The magnetic flux generated by the two primary windings... Φ 1 and Φ 2. It exhibits reverse superposition characteristics in the central column magnetic circuit; The self-equalizing DC-DC converter also includes a first bipolar output capacitor. C o1 Second bipolar output capacitor C o2 First bipolar output capacitor C o1 The second bipolar output capacitor C is connected in parallel with the first load. o2 Connected in parallel with the second load; V o2 / V o1 satisfy: in, V o1 , V o2 These are the voltages of the first load and the second load, respectively. The coupling coefficient of the voltage-balanced coupled inductor; L 3k , L 4k These are the leakage inductances of the first and second windings on the secondary side, respectively.

2. The bipolar self-equalizing DC-DC converter based on magnetic integration according to claim 1, characterized in that: The first full-bridge circuit and the four-winding transformer T r First primary magnetizing inductor L m1 With the second primary excitation inductor L m2 To form a two-level interleaved full-bridge circuit, the first primary-side magnetizing inductor L m1 With the second primary excitation inductor L m2 The series structure is connected in parallel with the two arms of the first full-bridge circuit, and the positive terminal of the input voltage is connected to the first primary magnetizing inductor. L m1 With the second primary excitation inductor L m2 The connection point is connected, and the negative terminal of the input voltage is connected to the midpoint of the first bridge arm of the first full-bridge circuit.

3. The bipolar self-equalizing DC-DC converter based on magnetic integration according to claim 2, characterized in that: The self-equalizing DC-DC converter also includes a clamping capacitor. C c Clamping capacitor C c It connects between the midpoint of the first bridge arm and the midpoint of the second bridge arm of the first full-bridge circuit.

4. The bipolar self-equalizing DC-DC converter based on magnetic integration according to claim 3, characterized in that: The clamping capacitor C c The voltage across the terminals is constant at twice the input voltage.

5. The bipolar self-equalizing DC-DC converter based on magnetic integration according to claim 1, characterized in that: The voltage-balanced coupling inductor T c The turns ratio is 1:1; the four-winding coupled inductor T r The turns ratio of the primary winding, the second winding, and the secondary winding is: n : n :1:1, n This is the set value.

6. A soft-switching optimization method applied to the magnetically integrated bipolar self-equalizing DC-DC converter according to any one of claims 1-5, characterized in that, include: The self-equalizing DC-DC converter uses a switching cycle as a set value. T s The phase-shift control strategy involves complementary drive signals for the switching transistors on the same bridge arm of the first and second full-bridge circuits, with both drive signals using a fixed duty cycle; and the drive timing of the upper switch transistor on the first bridge arm of the first full-bridge circuit leads the fifth switch transistor. Q The time of the 5th drive moment is D φ T s / 2, of which D φ To determine the phase shift duty cycle, power closed-loop control is used. D φ .

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