CN-120825067-B - Bipolar self-equalizing DC converter based on magnetic integration and soft switch optimization method

CN120825067BCN 120825067 BCN120825067 BCN 120825067BCN-120825067-B

Abstract

The bipolar self-equalizing DC converter based on magnetic integration comprises two full-bridge circuits, a four-winding transformer and a voltage balance coupling inductor, wherein the first full-bridge circuit outputs two output voltages, the two output voltages are respectively input to a primary side first winding and a primary side second winding of the four-winding transformer, one end of a secondary side first winding and one end of a second winding of the four-winding transformer are respectively connected with the middle point of a first bridge arm and the middle point of a second bridge arm of the second full-bridge circuit, the other ends of the secondary side first winding and the secondary side second winding of the four-winding transformer are respectively connected with one end of the primary side winding and one end of the secondary side winding of the voltage balance coupling inductor, and the other end of the primary side winding and the other end of the secondary side winding of the voltage balance coupling inductor are respectively connected with one end of a first load and one end of a second load. The invention enables all power semiconductor devices to realize zero-voltage switching characteristics.

Inventors

ZHANG KE
ZHU QIONG
XU YIFENG
WANG YUYING
BAI XIAOFEI
CHEN JIAYU
NING GUANGFU
WANG JUN
YIN WEI
DONG XIAOFENG
TONG MING
CHEN ZHIJUN
DING MIN
LI JUNTING
CHEN YIJIA

Assignees

国网江苏省电力有限公司苏州供电分公司
中南大学

Dates

Publication Date: 20260505
Application Date: 20250917

Claims (6)

1. Bipolar self-equalizing DC converter based on magnetic integration, including two full-bridge circuit, four winding transformer T r , voltage balance coupling inductance T c , its characterized in that: The input end of the first full-bridge circuit is connected with input voltage, the first full-bridge circuit outputs two output voltages, the two output voltages are respectively input to a primary side first winding and a primary side second winding of a four-winding transformer T r , one end of a secondary side first winding and one end of a second winding of the four-winding transformer T r are respectively connected with the middle point of a first bridge arm and the middle point of a second bridge arm of the second full-bridge circuit, the other ends of the secondary side first winding and the secondary side second winding of the four-winding transformer T c are respectively connected with one end of a primary side winding and one end of a secondary side winding of a voltage balance coupling inductor T c , the other ends of the primary side winding and the secondary side winding are respectively connected with one end of a first load and one end of a second load, and the other ends of the first load and the second load are respectively connected with two parallel points of the second full-bridge circuit; the voltage balance coupling inductance T c comprises a primary winding and a secondary winding which are in orthogonal symmetry, wherein the primary winding and the secondary winding are integrated on a magnetic core center post through a twisted pair parallel winding process, the magnetic core adopts an EE magnetic core structure, a composite magnetic flux phi c generated by the primary winding and the secondary winding forms a closed loop along the magnetic core center post, the magnetic core of a four-winding transformer T r adopts an EE magnetic core structure, a primary first winding and a secondary winding are respectively and symmetrically arranged on two side posts of the magnetic core, a distributed air gap structure with set length is arranged in a magnetic circuit where each winding is positioned, the magnetic core center post keeps an air gap-free structure, the difference between the magnetic resistance value of the two side posts and the magnetic resistance value of the magnetic core center post exceeds a set magnetic resistance threshold, the secondary first winding and the secondary winding are intensively arranged on the magnetic core center post through the orthogonal winding process, the magnetic fluxes phi 1 and phi 2 generated by the primary side double windings show reverse superposition characteristics in a middle column magnetic circuit; The self-equalizing direct current converter further comprises a first bipolar output capacitor C o1 and a second bipolar output capacitor C o2 , wherein the first bipolar output capacitor C o1 is connected with the first load in parallel and the second bipolar output capacitor C o2 is connected with the second load in parallel; V o2 / V o1 satisfies: Wherein V o1 、V o2 is the voltage of the first load and the voltage of the second load, respectively; the inductance is the coupling coefficient of the voltage balance coupling inductance, and L 3k 、L 4k is the leakage inductance of the first winding and the second winding of the secondary side respectively.
2. The bipolar self-equalizing dc converter based on magnetic integration according to claim 1, wherein: the first full-bridge circuit and the first primary excitation inductance L m1 and the second primary excitation inductance L m2 of the four-winding transformer T r form a two-level staggered full-bridge circuit, a series structure formed by the first primary excitation inductance L m1 and the second primary excitation inductance L m2 is connected with two bridge arms of the first full-bridge circuit in parallel, the positive electrode of an input voltage is connected with a connecting point of the first primary excitation inductance L m1 and the second primary excitation inductance L m2 , and the negative electrode of the input voltage is connected with the middle point of the first bridge arm of the first full-bridge circuit.
3. The bipolar self-equalizing dc converter based on magnetic integration according to claim 2, wherein: The self-equalizing DC converter further comprises a clamping capacitor C c , and the clamping capacitor C c is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm of the first full-bridge circuit.
4. A bipolar self-equalizing dc converter based on magnetic integration according to claim 3, wherein: The voltage across the clamp capacitor C c is constant at 2 times the input voltage.
5. The bipolar self-equalizing dc converter based on magnetic integration according to claim 1, wherein: The turn ratio of the voltage balance coupling inductor T c is 1:1, the turn ratio of the primary side first winding and the secondary side second winding of the four-winding coupling inductor T r is n:1:1, and n is a set value.
6. A soft switching optimization method applied to the bipolar self-equalizing dc converter based on magnetic integration according to any one of claims 1-5, characterized by comprising: The self-equalizing DC converter adopts a phase shift control strategy with a switching period being a set value T s , switching tube driving signals of the same bridge arm of the first full-bridge circuit and the second full-bridge circuit are complementary, the driving signals are all of fixed duty ratio, the driving time of an upper switching tube of the first bridge arm of the first full-bridge circuit is advanced by D φ T s /2 of the driving time of a fifth switching tube Q 5 , D φ is the phase shift duty ratio, and D φ is controlled by a power closed loop.

Description

Bipolar self-equalizing DC converter based on magnetic integration and soft switch optimization method Technical Field The invention belongs to the technical field of bipolar self-equalizing direct current converters, and particularly relates to a bipolar self-equalizing direct current converter based on magnetic integration and a soft switch optimization method. Background Photovoltaic power generation systems exist in large scale deployments. However, the lifetime of the photovoltaic array is greatly reduced due to the excessive ripple of the output current of the photovoltaic array. Therefore, a dc converter having a low input current ripple is indispensable in a photovoltaic power generation system. However, the traditional zero-input current ripple converter needs to be provided with a plurality of groups of discrete inductors and filter capacitors, which greatly reduces the power density of the system. It is worth noting that the novel bipolar direct current micro-grid has remarkable advantages in the aspects of efficiency, reliability, transmission capacity, safety and the like compared with the traditional unipolar architecture, and the photovoltaic power generation system can be used for the bipolar direct current distribution grid. However, when the load is connected in an unbalanced manner, a voltage imbalance between the two poles is caused. Document （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 zero input current ripple impedance source-shaped dc converters that achieve ripple-free control by designing the number of turns of the coupling inductor and the input inductor, but that are unipolar outputs with low reliability. Meanwhile, the switch is hard to turn off, and the switching loss is high. Document （D. Sha, Y. Xu, J. Zhang and Y. Yan, "Current-Fed Hybrid Dual Active Bridge DC–DC Converter for a Fuel Cell Power Conditioning System With Reduced Input Current Ripple," in IEEE Transactions on Industrial Electronics, vol. 64, no. 8, pp. 6628-6638） proposes a current-mode double-active bridge dc converter, which achieves zero ripple of the input current by means of two-phase interleaved inductors, but which comprises two large inductors with low power density. Disclosure of Invention In order to solve the defects in the prior art, the invention provides a bipolar self-equalizing DC converter based on magnetic integration and a soft switch optimization method. The invention adopts the following technical scheme. The first aspect of the invention provides a bipolar self-equalizing direct current converter based on magnetic integration, which comprises two full-bridge circuits, a four-winding transformer T r and a voltage balance coupling inductance T c, and specifically comprises the following components: the input end of the first full-bridge circuit is connected with input voltage, the first full-bridge circuit outputs two output voltages, the two output voltages are respectively input to a primary side first winding and a primary side second winding of a four-winding transformer T r, one end of a secondary side first winding and one end of a second winding of the four-winding transformer T r are respectively connected with the middle point of a first bridge arm and the middle point of a second bridge arm of the second full-bridge circuit, the other ends of the secondary side first winding and the secondary side second winding of the four-winding transformer T r are respectively connected with one end of a primary side winding and one end of a secondary side winding of a voltage balance coupling inductor T c, the other ends of the primary side winding and the secondary side winding of the voltage balance coupling inductor T c are respectively connected with one end of a first load and one end of a second load, and the other ends of the first load and the second load are respectively connected with two parallel points of the second full-bridge circuit. Preferably, the first primary exciting inductance L m1 and the second primary exciting inductance L m2 of the four-winding transformer T r form a two-level staggered full-bridge circuit, the series structure formed by the first primary exciting inductance L m1 and the second primary exciting inductance L m2 is connected in parallel with two bridge arms of the first full-bridge circuit, the positive electrode of the input voltage is connected with the connection point of the first primary exciting inductance L m1 and the second primary exciting inductance L m2, and the negative electrode of the input voltage is connected with the middle point of the first bridge arm of the first full-bridge circuit. Preferably, the self-equalizing dc converter further includes a clamping capacitor C c, and the clamping capacitor C c is connected between a midpoint of the first leg