Dual-phase-shift control method and system for a bidirectional DC / DC converter

Abstract

The present invention discloses a dual-phase-shift control method and system for a bidirectional DC / DC converter. The dual-phase-shift control method includes: obtaining the inner phase-shift angle α1 of the primary side and the inner phase-shift angle α2 of the secondary side of the bidirectional DC / DC converter; obtaining the outer phase-shift angle of the bidirectional DC / DC converter; obtaining the phase-shift angle α1dz converted from the dead-time of the primary side and the phase-shift angle α2dz converted from the dead-time of the secondary side of the bidirectional DC / DC converter; calculating one or more of the primary-side reference offset phase angle D1, the primary-side lagging leg offset phase angle D2, the secondary-side leading-leg offset phase angle D3, and the secondary-side lagging leg offset phase angle D4 of the bidirectional DC / DC converter according to the inner phase-shift angle α1 of the primary side, the inner phase-shift angle α2 of the secondary side, the phase-shift angle α1dz converted from the dead-time of the primary side, the phase-shift angle α2dz converted from the dead-time of the secondary side, and the outer phase-shift angle β. The present invention adopts an active control method of wide-range dual-phase-shift, further improving the efficiency and reducing the system stress.

Description

Technical Field

[0001] The present invention relates to a dual-phase-shift control method and system for a bidirectional DC / DC converter. Background Art

[0002] A renewable bidirectional energy converter consists of three major parts. The first part is a new energy power generation system, such as renewable new energy like photovoltaic power generation and tidal power generation, which mainly converts energy into DC voltage. The second part is an energy conversion device composed of a bidirectional DC / DC converter, a DC-AC converter, etc., responsible for energy conversion. The third part is an energy storage unit such as a storage battery and a supercapacitor. When the new energy is connected and operating, the new energy converts the energy into DC voltage through the power generation system. Part of it is converted into alternating current through the DC-AC converter for use by electrical equipment, and part of it is stored in the energy storage unit such as a storage battery or a supercapacitor through the bidirectional DC / DC converter. When an abnormality occurs in the new energy power generation system, such as when the photovoltaic power generation unit cannot output electric energy at night, the electric quantity of the energy storage unit needs to be supplied to the DC bus through the bidirectional DC / DC converter to ensure the normal operation of the AC electrical equipment.

[0003] Referring to Figure 1 As shown, the main circuit of a dual-active-bridge bidirectional DC / DC converter consists of a high-frequency transformer, an inductor (the sum of the externally connected inductor and the leakage inductance of the transformer), full-bridge circuits on both sides of the transformer, capacitors, and a power supply. Among them, the high-frequency transformer plays the role of electrical isolation and voltage transformation, the inductor ensures the energy transmission of the converter, and the capacitors on both sides of the transformer play the role of filtering and voltage stabilization. The converter can control the magnitude and direction of power transmission according to the demand relationship of the energy acting on both sides of the inductor by the transformer.

[0004] Currently, the control method of the dual-active-bridge bidirectional DC / DC converter mainly adopts single-phase-shift control. Through phase-shift control, a square-wave voltage with a certain phase-shift duty cycle is applied across the leakage inductance of the high-frequency transformer, and power transfer is achieved through the voltage difference. The magnitude and direction of power transmission are achieved by adjusting the phase-shift angle between the primary and secondary bridges, and the control is simple and convenient.

[0005] The traditional single-phase-shift control method can only control the phase-shift angle variable between the primary and secondary bridges. This method is simple and easy to implement closed-loop regulation, but it cannot adjust the comprehensive power characteristics of the system, such as reactive power and tube current stress, resulting in large reactive power during light-load output of the system, too high effective value and peak value of the alternating current flowing through the leakage inductance of the transformer, large system losses, and low efficiency.

[0006] Correspondingly, to address the above drawbacks, different multi-variable control methods have been proposed one after another. Among them, the dual-phase-shift control method not only adjusts the external phase-shift angle between the primary and secondary bridges but also adjusts the internal phase-shift angle generated within the primary bridge or the secondary bridge. By finding the optimal combination of the external and internal phase-shift angles, the reactive power and current stress of the system can be significantly reduced while ensuring a certain output power, thereby greatly improving the system efficiency.

[0007] Currently, the dual-phase-shift modulation method mainly uses the external phase-shift angle variable between the bridges and the internal phase-shift generated within the primary bridge or the secondary bridge to achieve. However, in the actual process, when using the combination of the external phase-shift angle variable between the bridges and the internal phase-shift angle variable within a single bridge, it is impossible to achieve m = N ps V dc2 / V dc1 wide-range adjustment. Summary of the Invention

[0008] In view of this, considering various factors such as cost and comprehensive indicators, the present invention provides a dual-phase-shift control method and system for a bidirectional DC / DC converter, which adopts an active control method with wide-range dual-phase-shift to further improve the efficiency and reduce the system stress.

[0009] According to the first aspect of the present invention, there is provided a phase-shift control method for a bidirectional DC / DC converter, comprising:

[0010] Step A: Obtain the internal phase-shift angle α1 on the primary side and the internal phase-shift angle α2 on the secondary side of the bidirectional DC / DC converter;

[0011] Step B: Obtain the external phase-shift angle β of the bidirectional DC / DC converter;

[0012] Step C: Obtain the phase-shift angle α 1dz converted from the dead-time on the primary side and the phase-shift angle α 2dz converted from the dead-time on the secondary side of the bidirectional DC / DC converter;

[0013] Step D: Calculate one or more of the primary-side reference offset phase angle D1, the primary-side lagging bridge arm offset phase angle D2, the secondary-side leading arm offset phase angle D3, and the secondary-side lagging bridge arm offset phase angle D4 of the bidirectional DC / DC converter according to the internal phase-shift angle α1 on the primary side, the internal phase-shift angle α2 on the secondary side, the phase-shift angle α 1dz converted from the dead-time on the primary side, the phase-shift angle α 2dz converted from the dead-time on the secondary side, and the external phase-shift angle β.

[0014] According to a specific and preferred embodiment, the specific steps of Step A are as follows:

[0015] Step A1: Obtain the modulation ratio coefficient m of the DC / DC converter based on the voltages of the primary side and secondary side of the bidirectional DC / DC converter;

[0016] Step A2: Determine whether m is greater than 1. When the result is no, set the inner phase-shift angle of the primary side and the inner phase-shift angle of the secondary side according to the inner phase-shift angle adjustment of the primary side of the bidirectional DC / DC converter; when the result is yes, set the inner phase-shift angle of the primary side and the inner phase-shift angle of the secondary side according to the inner phase-shift angle adjustment of the secondary side of the bidirectional DC / DC converter.

[0017] More preferably, in step A1, m is calculated by the formula m = N ps V dc2 / V dc1 where V dc1 is the voltage of the primary side of the bidirectional DC / DC converter, V dc2 is the voltage of the secondary side of the bidirectional DC / DC converter, and N ps is the voltage ratio coefficient between the primary side and the secondary side of the bidirectional DC / DC converter.

[0018] More preferably, in step A2, when the result is no, the inner phase-shift angle of the primary side α1 = π(1 - m), and the inner phase-shift angle of the secondary side α2 = 0; when the result is yes, the inner phase-shift angle of the primary side α1 = 0, and the inner phase-shift angle of the secondary side α2 = π(1 - 1 / m).

[0019] Preferably, in step B, the outer phase-shift angle β is obtained through a control loop based on the voltage information and current information of the primary side and secondary side of the bidirectional DC / DC converter. Specifically, the voltage information and current information of the primary side and secondary side of the bidirectional DC / DC converter are combined with the control loop to obtain the system outer phase-shift angle β, and this control loop is one of a voltage loop, a current loop, a combination of a voltage loop and a current loop, and a power loop.

[0020] Preferably, in step C, according to the dead-time of the secondary side and the primary side of the dual-active full-bridge bidirectional DC / DC converter, the converted phase-shift angle α 2dz of the dead-time of the secondary side and the converted phase-shift angle α 1dz of the dead-time of the primary side of the dual-active full-bridge bidirectional DC / DC converter are obtained.

[0021] More preferably, in step C, the converted phase-shift angle α 1dz of the dead-time of the primary side and the converted phase-shift angle α 2dz of the dead-time of the secondary side are calculated according to the following formula

[0022] α 1dz = T 1dz / T1 * 2π

[0023] α 2dz = T2dz / T2 * 2π

[0024] Among them, T 1dz is the dead - time on the primary side of the bidirectional DC / DC converter, and T1 is the control period on the primary side of the bidirectional DC / DC converter; T 2dz is the dead - time on the secondary side of the bidirectional DC / DC converter, and T2 is the control period on the secondary side of the bidirectional DC / DC converter.

[0025] Preferably, in step D, the primary - side reference offset phase angle D1, the primary - side lagging - leg offset phase angle D2, the secondary - side leading - arm offset phase angle D3, and the secondary - side lagging - leg offset phase angle D4 of the bidirectional DC / DC converter are calculated according to the following formula

[0026] D1 = 0

[0027] D2 = α1 + α 1dz = α1 + T 1dz / T1 * 2π

[0028] D3 = β + D2 = β + α1 + T 1dz / T1 * 2π

[0029] D4 = α 2dz + D3 + α2 = α 2dz + β + α1 + T 1dz / T1 * 2π + α2 = β + α1 + T 1dz / T1 * 2π + T 2dz / T2 * 2π + α2.

[0030] Preferably, the bidirectional DC / DC converter is controlled by a PWM register according to the calculation result of step E.

[0031] According to the second aspect of the present invention, a phase - shift control system for a bidirectional DC / DC converter is provided, including a control unit on which the above - mentioned dual - phase - shift control method is carried.

[0032] Preferably, the phase - shift control system further includes a signal acquisition unit for acquiring the current information of the bidirectional DC / DC converter.

[0033] The present invention adopts the above - mentioned scheme, and has the following advantages compared with the prior art:

[0034] The dual - phase - shift control method and system of the bidirectional DC / DC converter of the present invention adopt an active control method of wide - range dual - phase - shift, further improving the efficiency, reducing the system stress, and can well solve the problems of large reactive power, high effective value and peak value of the alternating current flowing through the leakage inductance of the transformer, large system loss and low efficiency when the system is lightly loaded. Description of the Drawings

[0035] To more clearly illustrate the technical solution of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0036] Figure 1 It is a hardware circuit diagram of a bidirectional DC / DC converter;

[0037] Figure 2 It is a schematic diagram of the principle of a dual-phase-shift control method according to an embodiment of the present invention;

[0038] Figure 3 It is a flowchart of a dual-phase-shift control method according to an embodiment of the present invention;

[0039] Figure 4 It is an implementation effect diagram of a dual-phase-shift control method according to an embodiment of the present invention. Specific Embodiments

[0040] The following will elaborate on the preferred embodiments of the present invention in conjunction with the drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted here that the description of these embodiments is for helping to understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] According to an embodiment of the present invention, an optimal dual-phase-shift method for a dual-active full-bridge bidirectional DC / DC converter is provided. Specifically, by detecting the current information of the dual-active full-bridge bidirectional DC / DC converter, this current can be the primary-side current information of the dual-active full-bridge bidirectional DC / DC converter, can be the secondary-side current information of the dual-active full-bridge bidirectional DC / DC converter, or can be the two information of the primary side and the secondary side of the dual-active full-bridge bidirectional DC / DC converter; by detecting the voltage information of the dual-active full-bridge bidirectional DC / DC converter, this voltage information is mainly divided into secondary-side voltage information and primary-side voltage information. Through the voltage information and the current information, combined with the control loop, the external phase-shift angle β of the system is obtained. At the same time, calculate m = N ps V dc2 / V dc1 where V dc1 is the primary-side voltage of the dual-active full-bridge bidirectional DC / DC converter, V dc2 is the secondary-side voltage of the dual-active full-bridge bidirectional DC / DC converter, and N psis the voltage ratio coefficient between the primary side and the secondary side of the dual-active full-bridge bidirectional DC / DC converter, and m is the system modulation ratio coefficient of the dual-active full-bridge bidirectional DC / DC converter after conversion. By selecting different internal phase-shift amounts through m, combining the internal phase-shift with the external phase-shift, and combining with the dead-time compensation algorithm of the secondary side and the primary side of the dual-active full-bridge bidirectional DC / DC converter, the dual-phase-shift control quantity of the system is realized through the hardware circuit, so as to achieve the optimal dual-phase-shift control result of the dual-active full-bridge bidirectional DC / DC converter.

[0042] Combined with Figure 2 and Figure 3 As shown in, the flow of the phase-shift control method of this bidirectional DC / DC converter is as follows.

[0043] Step S100, start.

[0044] Step S101, collect the voltage and current information of the bidirectional DC / DC converter. The current information is the primary side current information of the dual-active full-bridge bidirectional DC / DC converter, or the secondary side current information or the two current information of the primary side and the secondary side; the voltage information is the secondary side voltage information and the primary side voltage information.

[0045] Step S102, calculate the system modulation ratio coefficient m of the bidirectional DC / DC converter after conversion.

[0046] m = N ps V dc2 / V dc1 ; where V dc1 is the primary side voltage of the dual-active full-bridge bidirectional DC / DC converter; V dc2 is the secondary side voltage of the dual-active full-bridge bidirectional DC / DC converter; N ps is the voltage ratio coefficient between the primary side and the secondary side of the dual-active full-bridge bidirectional DC / DC converter, and this value can be obtained offline.

[0047] The N of the dual-active full-bridge bidirectional DC / DC converter ps is the voltage ratio coefficient between the primary side and the secondary side of the dual-active full-bridge bidirectional DC / DC converter, which is mainly determined by the turns ratio of the isolation transformer, and this value can be modified offline.

[0048] S103, judge whether m > 1?

[0049] When m ≤ 1, adjust the internal phase-shift angle of the primary side of the dual-active full-bridge bidirectional DC / DC converter. The specific internal phase-shift angle is: the primary side internal phase-shift angle α1 = π(1 - m), and the secondary side internal phase-shift angle α2 = 0; when m > 1, adjust the internal phase-shift angle of the secondary side of the dual-active full-bridge bidirectional DC / DC converter. The specific internal phase-shift angle is: the primary side internal phase-shift angle α1 = 0, and the secondary side internal phase-shift angle α2 = π(1 - 1 / m).

[0050] Step S104: Obtain the external phase-shift angle β of the bidirectional DC / DC converter;

[0051] According to the voltage and current information of the primary side and the secondary side of the dual-active-bridge bidirectional DC / DC converter collected in step S101, combined with the control loop, the system external phase-shift angle β is obtained. The control loop is a voltage loop, or a current loop, or a voltage loop and a current loop, or a power loop. By controlling the loop, the phase-shift angles of the primary side and the secondary side of the dual-active-bridge bidirectional DC / DC converter are obtained, and this phase-shift angle is denoted as the system external phase-shift angle β.

[0052] Step S105: Obtain the dead-time of the primary and secondary sides of the bidirectional DC / DC converter and the control period;

[0053] T 1dz is the dead-time of the primary side of the dual-active-bridge bidirectional DC / DC converter, and T1 is the control period of the primary side of the dual-active-bridge bidirectional DC / DC converter; T 2dz is the dead-time of the secondary side of the dual-active-bridge bidirectional DC / DC converter, and T2 is the control period of the secondary side of the dual-active-bridge bidirectional DC / DC converter. The dead-time of the secondary side and the primary side is mainly configured to prevent direct conduction of the upper and lower bridge arms of the secondary side and the primary side of the dual-active-bridge bidirectional DC / DC converter. This dead-time is determined by indicators such as turn-on time and turn-off time.

[0054] Step S106: Obtain the phase-shift angle α converted from the dead-time of the primary side of the bidirectional DC / DC converter 1dz and the phase-shift angle α converted from the dead-time of the secondary side 2dz ;

[0055] The phase-shift angle is obtained by converting the dead-time of the primary and secondary sides, and the phase-shift angle α converted from the dead-time of the secondary side of the dual-active-bridge bidirectional DC / DC converter 2dz and the phase-shift angle α converted from the dead-time of the primary side 1dz are obtained, where α 1dz = T 1dz / T1 * 2π,; α 2dz = T 2dz / T2 * 2π.

[0056] Step S107: Calculate the reference offset phase angle D1 of the primary side, the offset phase angle D2 of the lagging bridge arm of the primary side, the offset phase angle D3 of the leading arm of the secondary side, and the offset phase angle D4 of the lagging bridge arm of the secondary side of the bidirectional DC / DC converter according to the internal phase-shift angle α1 of the primary side, the internal phase-shift angle α2 of the secondary side, the phase-shift angle α converted from the dead-time of the primary side 1dz 、the phase-shift angle α converted from the dead-time of the secondary side 2dz and the external phase-shift angle β. Specifically: D1 = 0, D2 = α1 + α 1dz = α1 + T1dz / T1 * 2π, D3 = β + D2 = β + α1 + T 1dz / T1 * 2π and D4 = α 2dz + D3 + α2 = α 2dz + β + α1 + T 1dz / T1 * 2π + α2 = β + α1 + T 1dz / T1 * 2π + T 2dz / T2 * 2π + α2. Taking the primary side as a reference, D1 represents the reference offset phase angle of the primary side of the dual-active-bridge bidirectional DC / DC converter, D2 represents the offset phase angle of the lagging leg on the primary side of the dual-active-bridge bidirectional DC / DC converter, D3 represents the offset phase angle of the leading arm on the secondary side of the dual-active-bridge bidirectional DC / DC converter, and D4 represents the offset phase angle of the lagging leg on the secondary side of the dual-active-bridge bidirectional DC / DC converter.

[0057] The method of realizing the optimal fundamental wave phase shift of the dual-active-bridge bidirectional DC / DC converter is achieved by applying the obtained D1, D2, D3, and D4 through the PWM register and the hardware circuit.

[0058] This embodiment also provides a dual-phase-shift control system for a dual-active-bridge bidirectional DC / DC converter, including: a signal acquisition unit and a control unit. Among them, the signal acquisition unit is used to acquire the current information of the dual-active-bridge bidirectional DC / DC converter; the control unit is equipped with the above-mentioned dual-phase-shift control method.

[0059] The control unit, according to the acquired voltage information and current information of the dual-active-bridge bidirectional DC / DC converter, combines loop control, and finally combines the external phase shift angle of the system, the internal phase shift on the primary side and the internal phase shift on the secondary side, the phase shift angle converted from the dead time on the primary side and the phase shift angle converted from the dead time on the secondary side, which is realized through the hardware circuit, so as to achieve the optimal dual-phase-shift control result of the dual-active-bridge bidirectional DC / DC converter.

[0060] The above control unit can adopt a DSP (Digital Signal Processor) chip. During implementation, the current information of the dual-active-bridge bidirectional DC / DC converter is AC-DC. The signal acquisition unit uses a current sensor to detect the current. Since the A / D converter built in the DSP chip used by the control unit is unipolar and can only receive voltage signals of 0 to 3.0V, the control system also includes a voltage conversion unit to convert the acquired voltage so that it can be connected to the DSP. The optimal dual-phase-shift control algorithm of the dual-active-bridge bidirectional DC / DC converter is implemented in the DSP, combined with the above control algorithm to control the output of the dual-active-bridge bidirectional DC / DC converter, and the optimal dual-phase-shift control of the dual-active-bridge bidirectional DC / DC converter is achieved.

[0061] Refer toFigure 4 As shown, by adopting the dual-phase-shift control method of the above-mentioned dual-active full-bridge bidirectional DC / DC converter, on the dual-active full-bridge bidirectional DC / DC converter circuit, problems such as large reactive power existing during light-load output of the system, too high effective value and peak value of the alternating current flowing through the leakage inductance of the transformer, large system loss and low efficiency can be well solved.

[0062] The above embodiments are only for illustrating the technical concept and characteristics of the present invention and are a preferred embodiment. The purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A dual-phase-shift control method for a bidirectional DC / DC converter, characterized in that, Including: Step A: Obtain the primary-side internal phase-shift angle α1 and the secondary-side internal phase-shift angle α2 of the bidirectional DC / DC converter; Step B: Obtain the external phase-shift angle β of the bidirectional DC / DC converter; Step C: Calculate the primary-side dead-time conversion phase-shift angle α of the bidirectional DC / DC converter 1dz and the secondary-side dead-time conversion phase-shift angle α 2dz , α 1dz = T 1dz / T1 * 2π α 2dz = T 2dz / T2 * 2π Among them, T 1dz is the dead time on the primary side of the bidirectional DC / DC converter, and T1 is the control period on the primary side of the bidirectional DC / DC converter; T 2dz is the dead time on the secondary side of the bidirectional DC / DC converter, and T2 is the control period on the secondary side of the bidirectional DC / DC converter; Step D: Calculate the reference phase shift angle D1 of the primary side, the phase shift angle D2 of the lagging leg on the primary side, the phase shift angle D3 of the leading leg on the secondary side, and the phase shift angle D4 of the lagging leg on the secondary side of the bidirectional DC / DC converter according to the inner phase shift angle α1 on the primary side, the inner phase shift angle α2 on the secondary side, the phase shift angle α converted from the dead time on the primary side, the phase shift angle α converted from the dead time on the secondary side, and the outer phase shift angle β; 1dz , the phase shift angle α converted from the dead time on the secondary side 2dz and the outer phase shift angle β; The specific steps of Step A are as follows: Step A1: Collect the voltage information of the secondary side and the primary side of the bidirectional DC / DC converter, and obtain the modulation ratio coefficient m of the DC / DC converter according to the voltages of the primary side and the secondary side of the bidirectional DC / DC converter. m is calculated by the formula m = N ps V dc2 / V dc1 where V dc1 is the voltage of the primary side of the bidirectional DC / DC converter, V dc2 is the voltage of the secondary side of the bidirectional DC / DC converter, and N ps is the voltage ratio coefficient between the primary side and the secondary side of the bidirectional DC / DC converter; Step A2: Determine whether m is greater than 1. When the result is no, set the primary-side internal phase-shift angle and the secondary-side internal phase-shift angle according to the primary-side internal phase-shift angle regulation of the bidirectional DC / DC converter. The primary-side internal phase-shift angle α1 = π(1 - m), and the secondary-side internal phase-shift angle α2 = 0. When the result is yes, set the primary-side internal phase-shift angle and the secondary-side internal phase-shift angle according to the secondary-side internal phase-shift angle regulation of the bidirectional DC / DC converter. The primary-side internal phase-shift angle α1 = 0, and the secondary-side internal phase-shift angle α2 = π(1 - 1 / m); In Step D, calculate the primary-side reference offset phase angle D1, the primary-side lagging leg offset phase angle D2, the secondary-side leading leg offset phase angle D3, and the secondary-side lagging leg offset phase angle D4 of the bidirectional DC / DC converter according to the following formula, D1＝0 D2＝α1+α 1dz D3 = β + D2 D4 = α 2dz + D3 + α2。 2. The dual-phase-shift control method according to claim 1, wherein In Step B, obtain the external phase-shift angle β through a control loop based on the voltage information and current information of the primary side and the secondary side of the bidirectional DC / DC converter.

3. The dual-phase-shift control method according to claim 1, wherein, Control the bidirectional DC / DC converter through a PWM register according to the calculation result of Step D.

4. A dual-phase-shift control system for a bidirectional DC / DC converter, characterized in that, Including a control unit, which is equipped with the dual-phase-shift control method described in any one of claims 1 to 3.

5. The dual-phase shift control system according to claim 4, wherein The phase-shift control system further includes a signal acquisition unit, which is used to acquire the current information of the bidirectional DC / DC converter.

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