Isolation bidirectional converter low switching loss bipolar control method
By controlling the switching frequency and duty cycle of the half-bridge circuit and the full-bridge circuit, the DC bidirectional converter works at the resonant frequency point of the series resonant circuit, solving the low efficiency and transmission of traditional converters under wide input voltage and large voltage regulation. The problem of inconsistent characteristics achieves efficient power transmission and smooth dynamic characteristics.
Patent Information
- Application Number
- CN202411265984.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-10
- Publication Date
- 2024-12-17
AI Technical Summary
In the wide input voltage range and large voltage regulation requirements, traditional DC bidirectional converters have problems of inefficiency and inconsistent transmission characteristics, especially the large switching loss, which affects the power transmission efficiency.
By controlling the duty cycle of the half-bridge circuit and the switching frequency of the full-bridge circuit, the converter always works at the resonant frequency point of the series resonant circuit, reducing the number of switch tubes to turn off, realizing bidirectional energy regulation, independent of the power magnitude and direction.
It significantly reduces switching losses, improves power transmission efficiency, and realizes soft switching and smooth dynamic characteristics in a wide load range.
Smart Images
Figure CN119154633A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a low switching loss bipolar control method for an isolated bidirectional converter, belonging to the technical field of power electronic converters, in particular to the technical field of isolated bidirectional DC-DC electric energy conversion. Background Art
[0002] In electric vehicles, energy storage and other systems, bidirectional converters are the key to achieving energy interconnection and management. Bidirectional converters can reduce the volume, weight and cost of the system. In addition, with the popularization and application of solar photovoltaic power generation systems, the market for DC bidirectional converters is even broader. They are efficient, stable and reliable, and can improve the power generation efficiency and reliability of solar photovoltaic power generation systems. How to improve the power transmission efficiency of the converter and find a control method with superior performance, smoothness and stability are the key issues in this field.
[0003] The resonant converter has attracted wide attention for its excellent soft switching characteristics and high safety and reliability of galvanic isolation. The traditional LLC variable frequency resonant converter can realize soft switching and high frequency of semiconductor devices, but when the input voltage range is wide and the required voltage regulation range is large, the magnetizing inductance L m The smaller the value, the greater the circulating current loss of the transformer resonant cavity, resulting in reduced efficiency. When it is used in bidirectional applications, there are still problems such as inconsistent transmission characteristics and inability to achieve smooth switching of forward and reverse power transmission. In addition, traditional DC bidirectional converters are mainly two-stage structures. In order to achieve a lighter, more efficient and miniaturized DC bidirectional converter, a single-stage structure has more advantages due to its inherent high efficiency and high density. Therefore, in order to achieve a wider voltage regulation range, a single-stage structure is constructed to further reduce power transmission losses, improve the working efficiency of the converter, and make the forward and reverse power transmission switching smoother. Series resonant converters have been widely studied.
[0004] The existing mainstream control methods for series resonant converters include fixed frequency control and phase shift control. The literature "H.Wu, X.Tang, J.Zhao and Y.Xing, "An Isolated Bidirectional Microinverter Based on Voltage-in-Phase PWM-Controlled Resonant Converter," in IEEE Transactions on Power Electronics, vol.36, no.1, pp.562-570, Jan.2021, doi: 10.1109 / TPEL.2020.2997981." proposed the following method: Figure 3The control strategy of the fixed-frequency bipolar modulation method shown in the figure enables the converter to always operate at the resonant frequency point of the series resonant circuit, has good soft switching characteristics, and can achieve bidirectional energy regulation only by adjusting the duty cycle of the switch tube. In addition, the voltage gain of the converter is only related to the duty cycle of the original secondary side and has nothing to do with the load, which makes the converter have good dynamic characteristics; however, this control strategy is based on the PWM modulation strategy, and the shutdown current changes with the change of the PWM pulse width, which has a large shutdown loss. Under this control, the half-bridge switch tube is turned on and off many times in one switching cycle, which leads to a further increase in the switching loss, greatly reducing the power transmission efficiency of the converter. Summary of the invention Purpose of the invention:
[0005] The purpose of the present invention is to provide an isolated DC bidirectional resonant converter control method in view of the deficiencies in the prior art. The control method can make the converter always operate at the resonant frequency point of the series resonant circuit (20), and can achieve bidirectional energy regulation only by adjusting the duty cycle of the switch tube of the half-bridge circuit (10). The control method of the present invention makes the input and output voltage relationship of the resonant converter independent of the size and direction of the transmitted power, has the ability of bidirectional power rapid regulation, and reduces the number of times the switch tube of the half-bridge circuit (10) is turned on and off in a switching cycle, greatly reduces the switching loss, and improves the power transmission efficiency. Technical solution:
[0006] The purpose of the present invention is achieved through the following technical solutions:
[0007] The converter consists of a DC source 1 (U dc1 ), a half-bridge circuit (10), a series resonant circuit (20), a transformer (T), a full-bridge circuit (30) and a DC source 2 (U dc2 ), the half-bridge circuit (10) is composed of a first switch tube (S1) and a second switch tube (S2), and the series resonant circuit (20) is composed of a resonant inductor (L r )、resonant capacitor (C r ), the full-bridge circuit (30) is composed of a third switch tube (S3), a fourth switch tube (S4), a fifth switch tube (S5), and a sixth switch tube (S6), wherein the DC source 1 (U dcl ) is connected to one end of a capacitor C1 and the drain of a first switch tube (S1) of a half-bridge circuit (10), and the other end of the capacitor C1 is connected to one end of a capacitor C2 and a resonant capacitor (C r ) at one end, the resonant capacitor (C r ) is connected to the non-identical end of the primary winding of the transformer (T), and the other end of the capacitor C2 is connected to the DC source 1 (U dc1), the source of the first switch tube (S1) is connected to the drain of the second switch tube (S2) and the resonant inductor (L) of the series resonant circuit (20) r ) at one end, the resonant inductor (L r ) is connected to the same end of the primary winding of the transformer (T), and the source of the second switch tube (S2) is connected to the DC source 1 (U dc1 ), the same-name end of the secondary winding of the transformer (T) is connected to the source of the third switch tube (S3) and the drain of the fourth switch tube (S4) of the full-bridge circuit (30), the non-same-name end of the secondary winding of the transformer (T) is connected to the source of the fifth switch tube (S5) and the drain of the sixth switch tube (S6) of the full-bridge circuit (30), and the drains of the third switch tube (S3) and the fifth switch tube (S5) are connected to the DC source 2 (U dc2 ), the source electrodes of the fourth switch tube (S4) and the sixth switch tube (S6) are connected to the DC source 2 (U dc2 )’s negative terminal;
[0008] The first switch tube (S1) and the second switch tube (S2) of the half-bridge circuit (10) are complementary turned on, the third switch tube (S3) and the fourth switch tube (S4) of the full-bridge circuit (30) are complementary turned on, the fifth switch tube (S5) and the sixth switch tube (S6) are complementary turned on, the duty cycle of the third switch tube (S3), the fourth switch tube (S4), the fifth switch tube (S5), and the sixth switch tube (S6) is equal and equal to 0.5, the third switch tube (S3) and the fifth switch tube (S5) are turned on alternately at 180 degrees, and the switching frequencies of the third switch tube (S3), the fourth switch tube (S4), the fifth switch tube (S5), and the sixth switch tube (S6) are equal and greater than or equal to the resonant frequency of the series resonant circuit (20);
[0009] When the third switch tube (S3) and the sixth switch tube (S6) are turned on, the high level centers of the driving signals of the first switch tube (S1), the third switch tube (S3) and the sixth switch tube (S6) are aligned, and at this time, the duty cycle of the first switch tube (S1) is D1; when the fourth switch tube (S4) and the fifth switch tube (S5) are turned on, the high level centers of the driving signals of the first switch tube (S1), the fourth switch tube (S4) and the fifth switch tube (S5) are aligned, and at this time, the duty cycle of the first switch tube (S1) is D2;
[0010] Bridge arm midpoint voltage u ab When the third switch tube (S3) and the sixth switch tube (S6) are turned on, they are not odd symmetric with when the fourth switch tube (S4) and the fifth switch tube (S5) are turned on. The duty ratios D1 and D2 of the first switch tube (S1) of the half-bridge circuit (10) are adjusted to maintain u abThe output voltage and power of the isolated DC bidirectional converter are adjusted while the fundamental wave when the third switch tube (S3) and the sixth switch tube (S6) are turned on and the fundamental wave when the fourth switch tube (S4) and the fifth switch tube (S5) are turned on are continuous;
[0011] The technical solution of the present invention is essentially different from the existing technical solution in that, under the present control method, by controlling the switching frequency of the switch tubes of the half-bridge circuit (10) and the full-bridge circuit (30) to be equal to the resonant frequency, the converter can always operate at the resonant frequency point of the series resonant circuit (20), and bidirectional energy regulation can be achieved by simply adjusting the duty cycle of the switch tube of the half-bridge circuit (10). The control method of the present invention makes the input-output voltage relationship of the resonant converter independent of the size and direction of the transmitted power, and has the ability of bidirectional power rapid regulation. Moreover, by reducing the number of times the switch tube of the half-bridge circuit (10) is turned on and off, the switching loss is reduced, and the working efficiency of the converter is improved.
[0012] The present invention has the following beneficial effects:
[0013] (1) The control method of the present invention reduces the number of times the switch of the half-bridge circuit (10) is turned on and off in one switching cycle, greatly reduces switching losses, and improves power transmission efficiency;
[0014] (2) The converter operates at the resonant frequency point of the series resonant circuit (20), and can realize soft switching of all switch tubes within a wide load range;
[0015] (3) The overall voltage regulation range of the converter is relatively wide, the output gain is independent of the load, and it has smooth dynamic characteristics. The voltage and current of the DC bidirectional converter can be regulated over a wide range simply by adjusting the duty cycle of the switch tube of the half-bridge circuit (10). BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the embodiments;
[0017] Attached Figure 1 This is the schematic diagram of the isolated DC bidirectional converter on which this patent is based;
[0018] Attached Figure 2 This is a typical working waveform diagram of the control method described in this patent;
[0019] Attached Figure 3Shown is a typical operating waveform of the control strategy adopted in the literature “H.Wu, X.Tang, J.Zhao and Y.Xing, “An Isolated Bidirectional Microinverter Based on Voltage-in-Phase PWM-Controlled ResonantConverter,” in IEEE Transactions on Power Electronics, vol.36, no.1, pp.562-570, Jan.2021, doi: 10.1109 / TPEL.2020.2997981.”;
[0020] Attached Figure 4 This is a comparison chart of the number of switching times of the switch tube of the half-bridge circuit (10) within one switching cycle between the control strategy adopted in the document “H.Wu, X.Tang, J.Zhao and Y.Xing, “An Isolated Bidirectional Microinverter Based on Voltage-in-Phase PWM-Controlled Resonant Converter,” in IEEE Transactions on Power Electronics, vol.36, no.1, pp.562-570, Jan.2021, doi: 10.1109 / TPEL.2020.2997981.” and the control method described in this patent. DETAILED DESCRIPTION
[0021] The technical solution of the present invention is described in detail below with reference to the accompanying drawings;
[0022] like Figure 1 As shown, the converter consists of a DC source 1 (U dc1 ), a half-bridge circuit (10), a series resonant circuit (20), a transformer (T), a full-bridge circuit (30) and a DC source 2 (U dc2 ), the half-bridge circuit (10) is composed of a first switch tube (S1) and a second switch tube (S2), and the series resonant circuit (20) is composed of a resonant inductor (L r )、resonant capacitor (C r ), the full-bridge circuit (30) is composed of a third switch tube (S3), a fourth switch tube (S4), a fifth switch tube (S5), and a sixth switch tube (S6), wherein the DC source 1 (U dc1) is connected to one end of a capacitor C1 and the drain of a first switch tube (S1) of a half-bridge circuit (10), and the other end of the capacitor C1 is connected to one end of a capacitor C2 and a resonant capacitor (C r ) at one end, the resonant capacitor (C r ) is connected to the non-identical end of the primary winding of the transformer (T), and the other end of the capacitor C2 is connected to the DC source 1 (U dc1 ), the source of the first switch tube (S1) is connected to the drain of the second switch tube (S2) and the resonant inductor (L) of the series resonant circuit (20) r ) at one end, the resonant inductor (L r ) is connected to the same end of the primary winding of the transformer (T), and the source of the second switch tube (S2) is connected to the DC source 1 (U dc1 ), the same-name end of the secondary winding of the transformer (T) is connected to the source of the third switch tube (S3) and the drain of the fourth switch tube (S4) of the full-bridge circuit (30), the non-same-name end of the secondary winding of the transformer (T) is connected to the source of the fifth switch tube (S5) and the drain of the sixth switch tube (S6) of the full-bridge circuit (30), and the drains of the third switch tube (S3) and the fifth switch tube (S5) are connected to the DC source 2 (U dc2 ), the source electrodes of the fourth switch tube (S4) and the sixth switch tube (S6) are connected to the DC source 2 (U dc2 )’s negative terminal;
[0023] like Figure 2 As shown, the first switch tube (S1) and the second switch tube (S2) of the half-bridge circuit (10) are complementary turned on, the third switch tube (S3) and the fourth switch tube (S4) of the full-bridge circuit (30) are complementary turned on, the fifth switch tube (S5) and the sixth switch tube (S6) are complementary turned on, the duty cycle of the third switch tube (S3), the fourth switch tube (S4), the fifth switch tube (S5), and the sixth switch tube (S6) is equal and equal to 0.5, the third switch tube (S3) and the fifth switch tube (S5) are turned on 180 degrees staggered, and the switching frequencies of the third switch tube (S3), the fourth switch tube (S4), the fifth switch tube (S5), and the sixth switch tube (S6) are equal and greater than or equal to the resonant frequency of the series resonant circuit (20);
[0024] When the third switch tube (S3) and the sixth switch tube (S6) are turned on, the high level centers of the driving signals of the first switch tube (S1), the third switch tube (S3) and the sixth switch tube (S6) are aligned, and at this time, the duty cycle of the first switch tube (S1) is D1; when the fourth switch tube (S4) and the fifth switch tube (S5) are turned on, the high level centers of the driving signals of the first switch tube (S1), the fourth switch tube (S4) and the fifth switch tube (S5) are aligned, and at this time, the duty cycle of the first switch tube (S1) is D2;
[0025] Bridge arm midpoint voltage u ab When the third switch tube (S3) and the sixth switch tube (S6) are turned on, they are not odd symmetric with when the fourth switch tube (S4) and the fifth switch tube (S5) are turned on. The duty ratios D1 and D2 of the first switch tube (S1) of the half-bridge circuit (10) are adjusted to maintain u ab The output voltage and power of the isolated DC bidirectional converter are adjusted while the fundamental wave when the third switch tube (S3) and the sixth switch tube (S6) are turned on and the fundamental wave when the fourth switch tube (S4) and the fifth switch tube (S5) are turned on are continuous;
[0026] like Figure 4 As shown, compared with the control method described in the document “H.Wu, X.Tang, J.Zhao and Y.Xing, ″An Isolated Bidirectional Microinverter Based on Voltage-in-Phase PWM-Controlled Resonant Converter, ″in IEEE Transactions on Power Electronics, vol.36, no.1, pp.562-570, Jan.2021, doi: 10.1109 / TPEL.2020.2997981.”, the control method described in the present patent has fewer times of switching on and off of the switch tube of the half-bridge circuit (10) in one switching cycle, and smaller switching loss;
[0027] The above description is only a preferred example of the present invention and is not intended to limit the present invention. For ordinary technicians in this technical field, under the premise that the corresponding technical solution does not essentially deviate from the principle of the present invention, several improvements and modifications can be made, which should be regarded as within the protection scope of the present invention.
Claims
1. A low switching loss bipolar control method for an isolated bidirectional converter is characterized by: The converter consists of a DC source 1 (U dc1 ), a half-bridge circuit (10), a series resonant circuit (20), a transformer (T), a full-bridge circuit (30) and a DC source 2 (U dc2 ), the half-bridge circuit (10) is composed of a first switch tube (S1) and a second switch tube (S2), and the series resonant circuit (20) is composed of a resonant inductor (L r )、resonant capacitor (C r ), the full-bridge circuit (30) is composed of a third switch tube (S3), a fourth switch tube (S4), a fifth switch tube (S5), and a sixth switch tube (S6), wherein the DC source 1 (U dc1 ) is connected to one end of a capacitor C1 and the drain of a first switch tube (S1) of a half-bridge circuit (10), and the other end of the capacitor C1 is connected to one end of a capacitor C2 and a resonant capacitor (C r ) at one end, the resonant capacitor (C r ) is connected to the non-identical end of the primary winding of the transformer (T), and the other end of the capacitor C2 is connected to the DC source 1 (U dc1 ), the source of the first switch tube (S1) is connected to the drain of the second switch tube (S2) and the resonant inductor (L) of the series resonant circuit (20) r ) at one end, the resonant inductor (L r ) is connected to the same end of the primary winding of the transformer (T), and the source of the second switch tube (S2) is connected to the DC source 1 (U dc1 ), the same-name end of the secondary winding of the transformer (T) is connected to the source of the third switch tube (S3) and the drain of the fourth switch tube (S4) of the full-bridge circuit (30), the non-same-name end of the secondary winding of the transformer (T) is connected to the source of the fifth switch tube (S5) and the drain of the sixth switch tube (S6) of the full-bridge circuit (30), and the drains of the third switch tube (S3) and the fifth switch tube (S5) are connected to the DC source 2 (U dc2 ), the source electrodes of the fourth switch tube (S4) and the sixth switch tube (S6) are connected to the DC source 2 (U dc2 )’s negative terminal; The first switch tube (S1) and the second switch tube (S2) of the half-bridge circuit (10) are complementary turned on, the third switch tube (S3) and the fourth switch tube (S4) of the full-bridge circuit (30) are complementary turned on, the fifth switch tube (S5) and the sixth switch tube (S6) are complementary turned on, the duty cycle of the third switch tube (S3), the fourth switch tube (S4), the fifth switch tube (S5), and the sixth switch tube (S6) is equal and equal to 0.5, the third switch tube (S3) and the fifth switch tube (S5) are turned on alternately at 180 degrees, and the switching frequencies of the third switch tube (S3), the fourth switch tube (S4), the fifth switch tube (S5), and the sixth switch tube (S6) are equal and greater than or equal to the resonant frequency of the series resonant circuit (20); When the third switch tube (S3) and the sixth switch tube (S6) are turned on, the high level centers of the driving signals of the first switch tube (S1), the third switch tube (S3) and the sixth switch tube (S6) are aligned, and at this time, the duty cycle of the first switch tube (S1) is D1; when the fourth switch tube (S4) and the fifth switch tube (S5) are turned on, the high level centers of the driving signals of the first switch tube (S1), the fourth switch tube (S4) and the fifth switch tube (S5) are aligned, and at this time, the duty cycle of the first switch tube (S1) is D2; Bridge arm midpoint voltage u ab When the third switch tube (S3) and the sixth switch tube (S6) are turned on, they are not odd symmetric with when the fourth switch tube (S4) and the fifth switch tube (S5) are turned on. The duty ratios D1 and D2 of the first switch tube (S1) of the half-bridge circuit (10) are adjusted to maintain u ab The output voltage and power of the isolated DC bidirectional converter are adjusted while the fundamental wave when the third switch tube (S3) and the sixth switch tube (S6) are turned on and the fundamental wave when the fourth switch tube (S4) and the fifth switch tube (S5) are turned on are continuous.