阅读说明：本技术 一种直流变压器交流分布参数网络中高频振荡抑制方法 (Method for suppressing high-frequency oscillation in alternating-current distribution parameter network of direct-current transformer ) 是由 赵彪 崔彬 安峰 白睿航 宋强 余占清 曾嵘 于 2021-01-19 设计创作，主要内容包括：本发明提供一种直流变压器交流分布参数网络中高频振荡抑制方法,包括步骤：计算高频振荡幅值周期t-(HFO)；由所述高频振荡幅值周期t-(HFO)计算得到并联吸收电容C-(parall)；在双主动全桥变换器的开关器件上并联大小为C-(parall)的吸收电容。本发明能够减小电压电流高频振荡波形幅值,抑制因高频振荡而带来的直流变压器电压电流波形畸变问题；减小变压器端口电压应力,降低变压器绝缘要求；抑制因高频振荡而带来的直流变压器电磁干扰(EMI)和共模噪声(CM noise)问题,营造良好电磁环境；减小因高频振荡而带来的直流变压器高频损耗,提升直流变压器系统效率。(The invention provides a method for suppressing high-frequency oscillation in an alternating current distribution parameter network of a direct current transformer, which comprises the following steps: calculating the period t of the amplitude of the high-frequency oscillation HFO (ii) a From said high frequency oscillation amplitude period t HFO Calculating to obtain a parallel absorption capacitor C parall (ii) a The switching device of the double-active full-bridge converter is connected in parallel with a switch with the size of C parall The absorption capacitance of (1). The invention can reduce the amplitude of the high-frequency oscillation waveform of the voltage and the current and inhibit the distortion problem of the voltage and the current waveform of the direct-current transformer caused by high-frequency oscillation; the voltage stress of the transformer port is reduced, and the insulation requirement of the transformer is lowered; suppression of electromagnetic interference (EMI) and common mode noise of DC transformers due to high frequency oscillationsAcoustic (CM noise) problems, creating a good electromagnetic environment; the high-frequency loss of the direct-current transformer caused by high-frequency oscillation is reduced, and the efficiency of the direct-current transformer system is improved.)

1. A method for suppressing high-frequency oscillation in an alternating current distribution parameter network of a direct current transformer is characterized by comprising the following steps:

calculating the period t of the amplitude of the high-frequency oscillation_HFO；

From said high frequency oscillation amplitude period t_HFOCalculating to obtain a parallel absorption capacitor C_parall；

The switching device of the double-active full-bridge converter is connected in parallel with a switch with the size of C_parallThe absorption capacitance of (1).

2. The method for suppressing high frequency oscillation in an AC distributed parameter network of a DC transformer as recited in claim 1,

the high frequency oscillation amplitude period t_HFOAnd calculating based on the distribution parameters of the transformer in the double-active full-bridge converter.

3. The method for suppressing high frequency oscillation in an AC distributed parameter network of a DC transformer as recited in claim 2,

the transformer distribution parameters include: c_p，C_s，C_ps，L_m，R_m，L_s，r_s，n，

Wherein the content of the first and second substances,

C_pis the distributed capacitance of the primary winding of the transformer;

C_sis the distributed capacitance of the secondary winding of the transformer;

C_psis a cross-over capacitor between the primary and secondary windings;

L_mis a transformer excitation inductance;

R_mis a transformer exciting resistor;

L_sis converted into the leakage inductance of the secondary side of the transformer;

r_sconverting the winding resistance to the secondary side of the transformer;

and n is the transformer transformation ratio.

4. The method for suppressing high frequency oscillation in an AC distributed parameter network of a DC transformer as recited in claim 3,

the high frequency oscillation amplitude period t_HFOSatisfies the following conditions:

wherein the content of the first and second substances,

L_phrepresenting the primary side phase-shift inductance L_ph1And secondary side phase-shifting inductor L_ph2A common magnitude of sensitivity; r is_phRepresenting the phase-shifting inductance L_ph1And L_ph2The magnitude of the common resistance.

5. The method for suppressing high frequency oscillation in an AC distributed parameter network of a DC transformer as recited in claim 4,

the parallel absorption capacitor C_parallSatisfies the following conditions:

wherein the content of the first and second substances,

i (t) is the current at the moment when the switching device is switched on or off, U_dcIs referred to as U_inAnd U_outCommon magnitude of voltage, U_inAnd U_outThe direct-current side voltages of a primary side H bridge and a secondary side H bridge of the double-active full-bridge converter are respectively;

t₀is the variation time t of the AC voltage of the double-active full-bridge converter₀＝n₁t_HFO，n₁Taking a positive integer.

6. The method for suppressing high frequency oscillation in an AC distributed parameter network of a DC transformer as recited in claim 5,

t₀＝t_HFOthe high frequency oscillation amplitude is minimal.

7. The method for suppressing high frequency oscillation in AC distributed parameter network of DC transformer as claimed in claim 5 or 6,

the switching devices are power electronic switching devices in a primary side H bridge and a secondary side H bridge of the double-active full-bridge converter.

8. The method for suppressing high frequency oscillation in an AC distributed parameter network of a DC transformer as recited in claim 7,

the power electronic switch device is an insulated gate bipolar transistor or a metal-oxide semiconductor field effect transistor.

Technical Field

The invention belongs to the technical field of power electronics, and particularly relates to a method for suppressing high-frequency oscillation in an alternating-current distribution parameter network of a direct-current transformer.

Background

A circuit topology of a Dual Active Bridge (DAB) converter is shown in figure 1, and the DAB converter mainly comprises a primary side H bridge A, a secondary side H bridge D, a primary side phase-shift inductor B, a secondary side phase-shift inductor C and a high-frequency isolation transformer E, and the alternating voltage U of the Dual active bridge converter is controlled₁And U₂The phase shift angle D between the two can realize the control of the transmission power and the direction. The double-active full-bridge converter has the advantages of bidirectional power transmission, soft switching, electric isolation, flexible control and the like, and is widely applied to various fields such as locomotive traction, renewable energy sources, energy storage, energy internet and the like. In recent years, the development of new generation wide bandgap semiconductor devices based on materials such as silicon carbide (SiC) and gallium nitride (GaN) and the application of nanocrystalline magnetic core materials have promoted the development of DAB with higher frequency, smaller volume and weight and higher power density. However, the high switching speed of SiC devices increases the magnitude of the voltage rate of change dv/dt of the system (v being the ac voltage U of the dual active full bridge converter)₁And U₂) The distributed capacitance of the transformer is increased due to the fact that the nanocrystalline magnetic core material has high conductivity, a complex distributed parameter network is formed on the alternating current side of DAB by the distributed capacitance of the transformer and an inductive element, and the distributed parameter network generates serious high-frequency oscillation under the excitation of dv/dt. High frequency oscillation not only increases the voltage stress and insulation level requirements of the transformer port, generates high frequency loss, but also increases the voltage stress and insulation level requirements of the transformer portThe system electromagnetic environment is deteriorated, electromagnetic interference (EMI) and common mode noise (CM noise) are generated, and the system operation reliability is influenced.

The classical three-capacitance distribution parametric model can be obtained by treating the transformer as a two-port network, as shown in fig. 2, where C_PRepresenting the primary coupling capacitance, C_SRepresenting secondary side coupling capacitance, C_PSRepresenting the coupling capacitance between the primary and secondary sides of the transformer, with Lm and Rm being the primary-side converted transformer excitation inductance and resistance, Ls and r_sTransformer leakage inductance and winding resistance translated for secondary side. A complex high-order distributed parameter network is formed by transformer distributed parameters and phase-shifting inductors on the alternating current side of the DAB, and high-frequency oscillation is easily generated under the excitation of high dvdt.

In the prior art, the distributed capacitance of the transformer is mainly reduced through the optimized design of the transformer so as to realize the suppression of high-frequency oscillation.

Disclosure of Invention

In order to solve the above problems, the present invention provides a method for suppressing High Frequency Oscillation (HFO) in an ac distributed parameter network of a dc transformer.

The invention discloses a method for suppressing high-frequency oscillation in an alternating-current distribution parameter network of a direct-current transformer, which comprises the following steps of:

calculating the period t of the amplitude of the high-frequency oscillation_HFO；

From said high frequency oscillation amplitude period t_HFOCalculating to obtain a parallel absorption capacitor C_parall；

The switching device of the double-active full-bridge converter is connected in parallel with a switch with the size of C_parallThe absorption capacitance of (1).

Further, in the present invention,

the high frequency oscillation amplitude period t_HFOAnd calculating based on the distribution parameters of the transformer in the double-active full-bridge converter.

Further, in the present invention,

the transformer distribution parameters include: c_p，C_s，C_ps，L_m，R_m，L_s，r_s，n，

Wherein the content of the first and second substances,

C_pis the distributed capacitance of the primary winding of the transformer;

C_sis the distributed capacitance of the secondary winding of the transformer;

C_psis a cross-over capacitor between the primary and secondary windings;

L_mis a transformer excitation inductance;

R_mis a transformer exciting resistor;

L_sis converted into the leakage inductance of the secondary side of the transformer;

r_sconverting the winding resistance to the secondary side of the transformer;

and n is the transformer transformation ratio.

Further, in the present invention,

the high frequency oscillation amplitude period t_HFOSatisfies the following conditions:

wherein the content of the first and second substances,

L_phrepresenting the primary side phase-shift inductance L_ph1And secondary side phase-shifting inductor L_ph2A common magnitude of sensitivity; r is_phRepresenting the phase-shifting inductance L_ph1And L_ph2The magnitude of the common resistance.

Further, in the present invention,

the parallel absorption capacitor C_parallSatisfies the following conditions:

wherein the content of the first and second substances,

i (t) for switching on the switching deviceOr the current at the moment of switching-off, U_dcIs referred to as U_inAnd U_outCommon magnitude of voltage, U_inAnd U_outThe direct-current side voltages of a primary side H bridge and a secondary side H bridge of the double-active full-bridge converter are respectively;

t₀is the variation time t of the AC voltage of the double-active full-bridge converter₀＝n₁t_HFO，n₁Taking a positive integer.

Further, in the present invention,

t₀＝t_HFOthe high frequency oscillation amplitude is minimal.

Further, in the present invention,

the switching devices are power electronic switching devices in a primary side H bridge and a secondary side H bridge of the double-active full-bridge converter.

Further, in the present invention,

the power electronic switch device is an insulated gate bipolar transistor or a metal-oxide semiconductor field effect transistor.

The HFO suppression method in the alternating current distribution parameter network of the direct current transformer can realize that: (1) the amplitude of the high-frequency oscillation waveform of the voltage and the current is reduced, and the problem of the waveform distortion of the voltage and the current of the direct-current transformer caused by high-frequency oscillation is solved; (2) the voltage stress of the transformer port is reduced, and the insulation requirement of the transformer is lowered; (3) the problems of electromagnetic interference (EMI) and common mode noise (CMnoise) of the direct-current transformer caused by high-frequency oscillation are suppressed, and a good electromagnetic environment is created; (4) the high-frequency loss of the direct-current transformer caused by high-frequency oscillation is reduced, and the efficiency of the direct-current transformer system is improved.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Figure 1 shows a circuit topology of a dual active full bridge converter according to the prior art;

FIG. 2 shows a DAB AC side distribution parameter model diagram according to an embodiment of the present invention;

FIG. 3 is a graph illustrating the relationship between the amplitude of the high frequency oscillation and the distributed capacitances C and dv/dt of the transformer, according to an embodiment of the present invention;

FIG. 4 shows a schematic diagram of a high frequency oscillation suppression method according to an embodiment of the invention;

fig. 5 shows a graph of the primary voltage waveform of a prior art DAB transformer.

Fig. 6 shows a graph of the primary voltage waveform of the port of the transformer in DAB using the hf oscillation suppression method of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The DAB alternating current side distribution parameter model adopted by the invention is shown in figure 2. In FIG. 2, C_pIs a distributed capacitance, C, of the primary winding of a high-frequency transformer F_sIs the distributed capacitance, C, of the secondary winding of a high-frequency transformer F_psIs a cross-over capacitance, L, between primary and secondary windings_mIs the transformer excitation inductance, R_mIs a transformer exciting resistance, L_sIs converted into leakage inductance, r, of the secondary side of the transformer_sConverted to the winding resistance on the secondary side of the transformer, n is the transformer transformation ratio.

Through the distribution parameter model of fig. 2, the functional relationship between the high-frequency oscillation amplitude VSA and the transformer distribution capacitances C and dv/dt can be derived as shown in equation (1):

in the formula (1), the reaction mixture is,

wherein, t₀Is a double-active full-bridge converter AC voltage U₁And U₂Time of change of voltage, time of change of voltage; i.e. i_L(0) is primary side phase-shifting inductance L_ph1And secondary side phase-shifting inductor L_ph2Common initial current, U_C(0. ANG.) is the distributed capacitance C_pAnd C_sThe voltage of the common initial voltage is set to be,i_L(0. ANG.) and U_CThe underline in (0. ANG.) is a minus sign, representing an initial value; l is_phRepresenting the primary side phase-shift inductance L_ph1And secondary side phase-shifting inductor L_ph2A common magnitude of sensitivity; r is_phRepresenting the phase-shifting inductance L_ph1And L_ph2The common resistance value is large or small; u shape_dcIs referred to as U_inAnd U_outCommon magnitude of voltage, U_inAnd U_outThe direct-current side voltages of the primary side H bridge and the secondary side H bridge of the DAB are respectively.

Fig. 3 shows a graph of the amplitude of the high frequency oscillations versus the transformer distributed capacitance C and dv/dt, wherein arrow G represents the method of reducing dv/dt, arrow H represents the method of reducing dv/dt and the transformer distributed capacitance C simultaneously, and arrow I represents the method of reducing the transformer distributed capacitance C. As can be seen from fig. 3:

1) the traditional method of reducing the distributed capacitance C of the transformer to suppress high frequency oscillation is not suitable for the occasion of high dv/dt.

2) The method of reducing dv/dt to suppress high frequency oscillations is not suitable for high distributed capacitance applications.

3) The high-frequency oscillation amplitude has a complex nonlinear relation with the distributed capacitance C and dv/dt of the transformer.

With the use of high-speed switching devices in DAB in recent years, high dv/dt is generated in the system, the problem of high-frequency oscillation in DAB is an unavoidable and urgent problem to be solved, but the invention can provide a scheme that a plurality of groups of optimally distributed capacitors exist, and dv/dt can enable the amplitude of high-frequency oscillation to take a minimum value so as to solve the problem. The method for suppressing the high-frequency oscillation provided by the invention comprises the following steps:

by oscillating amplitude A at high frequency versus time t of voltage change₀Taking the derivative and making the derivative equal to zero yields:

wherein the content of the first and second substances,

t_HFOin order to have a high-frequency oscillation period,

let the amplitude a take the minimum solution as:

t₀＝n₁t_HFO,(n₁∈N^*) (11)，

in the formula (11), N^*Is a positive integer. From the equation (10), when the voltage changes for a time t₀Is an oscillation period t_HFOThe high-frequency oscillation amplitude a takes a minimum value at integral multiples of (d), as shown in fig. 4.

In the present invention, the voltage change time t of the H-bridge dv/dt₀The regulation can be realized by connecting a switch device in DAB in parallel with an absorption capacitor C_parallImplementation, absorption capacitance C_parallCalculated from equations (8) and (11):

i (t) is the current at the moment when the switching device is turned on or off. When t is satisfied₀＝t_HFOWhen the high-frequency oscillation amplitude A is minimum, t can be obtained from the formula (11)₀Then, k is obtained from the formula (8), and C is obtained from the formula (12)_parall。

The high-frequency oscillation suppression method of the present invention includes the steps of:

the method comprises the following steps: the method for extracting the distribution parameters of the transformer in the DAB converter through simulation or experiment comprises the following steps: c_p，C_s，C_ps，L_m，R_m，L_s，r_sAnd n is a number. Wherein, due to L_sAnd r_sThe values of the two parameters are small, and can be ignored in the formula derivation process.

Step two: calculating the high-frequency oscillation amplitude period t by the formulas (6) and (10)_HFO。

Step three: the parallel absorption capacitance C of the switching device is calculated from the equations (8), (11) and (12)_parallThe size of (2).

Step four: the switch device of DAB is connected with C in parallel_parallIs suckedThe capacitance can make the amplitude of high-frequency oscillation in DAB obtain the minimum value, thus solving the problem of high-frequency oscillation in DAB. The switch devices are power electronic switch devices in a primary side H bridge and a secondary side H bridge of DAB, and the commonly used switch devices comprise an Insulated Gate Bipolar Transistor (IGBT), a metal-oxide semiconductor field effect transistor (MOSFET) and the like.

Fig. 5 shows a graph of a primary voltage waveform of a transformer in a prior art DAB, and fig. 6 shows a graph of a primary voltage waveform of a port of a transformer in a DAB after the high frequency oscillation suppression method of the present invention is applied. As can be seen from fig. 5, the transformer in the prior art DAB has a significant problem of high frequency oscillation. Fig. 6 illustrates that the high-frequency oscillation is obviously suppressed after the high-frequency oscillation amplitude suppression method provided by the invention is adopted. Therefore, the suppression method provided by the patent can perfectly solve the problem of high-frequency oscillation generated in the DAB.

The invention can reduce the amplitude of the high-frequency oscillation waveform of the voltage and the current and inhibit the distortion problem of the voltage and the current waveform of the direct-current transformer caused by high-frequency oscillation; the voltage stress of the transformer port is reduced, and the insulation requirement of the transformer is lowered; the problems of electromagnetic interference (EMI) and common mode noise (CM noise) of the direct current transformer caused by high-frequency oscillation are suppressed, and a good electromagnetic environment is created; the high-frequency loss of the direct-current transformer caused by high-frequency oscillation is reduced, and the efficiency of the direct-current transformer system is improved.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.