Control methods for power converters, power converters and electronic equipment

Abstract

This disclosure provides a control method, power converter, and electronic device for a power converter. The power converter includes an input-side circuit, an output-side circuit, and a resonant circuit. The input-side circuit is connected to a DC voltage terminal, and the output-side circuit is connected to three-phase AC terminals. The method includes: determining the average current value of the three AC-side bridge arms of the output-side circuit during a switching cycle based on a set current value at the three-phase AC terminals; determining the switching phase shift angle and target operating frequency of the power converter's switching transistors during a switching cycle based on the average current value, the DC sampling voltage value at the DC voltage terminal, and the AC voltage sampling values ​​at the three-phase AC terminals; and generating a drive signal based on the switching phase shift angle and the target operating frequency to drive the switching transistors in the power converter. Embodiments of this disclosure can improve the efficiency of the power converter.

Description

Technical Field

[0001] This disclosure relates to the field of power electronics technology, and in particular to a control method for a power converter, a power converter, and an electronic device. Background Technology

[0002] In DC / AC conversion systems, resonant single-stage DC / AC converters have been widely used in various power conversion scenarios due to their advantages such as low cost and high efficiency. Common resonant single-stage DC / AC converters have a full-bridge structure on the AC side; replacing it with a half-bridge structure can further reduce system costs. However, there is no clear power model for this half-bridge power converter in related technologies. How to achieve functional control of the power converter by controlling the on / off state and switching frequency of the DC and AC side switches is a problem that urgently needs to be solved. Summary of the Invention

[0003] This disclosure provides a control method for a power converter, a power converter, and an electronic device.

[0004] In a first aspect, this disclosure provides a control method for a power converter, the power converter including an input-side circuit, an output-side circuit, and a resonant circuit connected between the input-side circuit and the output-side circuit. The input-side circuit is connected to a DC voltage terminal, and the output-side circuit is connected to three-phase AC terminals. The method includes: determining the average current value of the three AC-side arms of the output-side circuit during a switching cycle based on a set current value at the three-phase AC terminals; determining the switching phase shift angle of the power converter's switching transistors during a switching cycle and the target operating frequency of the power converter based on the average current value, the DC sampling voltage value at the DC voltage terminal, and the AC voltage sampling value at the three-phase AC terminals; and generating a drive signal based on the switching phase shift angle and the target operating frequency, the drive signal being used to drive the switching transistors in the power converter.

[0005] Secondly, this disclosure provides a power converter, which includes: an input-side circuit, an output-side circuit, a resonant circuit, and a controller. The input-side circuit is connected to a DC voltage terminal, and the output-side circuit is connected to a three-phase AC terminal. The resonant circuit is connected between the input-side circuit and the output-side circuit. The controller is connected to the input-side circuit and the output-side circuit and is configured to execute the control method of the power converter described above.

[0006] Thirdly, this disclosure provides an electronic device that includes the power converter described above.

[0007] The embodiments provided in this disclosure can achieve precise regulation of the three-phase output current of the power converter by coordinating multiple control variables, thereby reducing the switching losses on the AC side of the power converter and improving the efficiency of the power converter.

[0008] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0009] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the embodiments of the present disclosure to explain the disclosure and do not constitute a limitation thereof. The above and other features and advantages will become more apparent to those skilled in the art from the detailed exemplary embodiments described with reference to the accompanying drawings.

[0010] Figure 1 This is a schematic diagram of a power converter provided in an embodiment of the present disclosure.

[0011] Figure 2 A flowchart of a control method for a power converter provided in an embodiment of this disclosure.

[0012] Figure 3 This is a schematic diagram of the voltage and current waveforms of a power converter provided in an embodiment of the present disclosure.

[0013] Figure 4 This is a schematic diagram of the resonant current of a power converter provided in an embodiment of this disclosure.

[0014] Figure 5 This is a schematic diagram of the primary voltage and resonant current of a power converter provided in an embodiment of this disclosure.

[0015] Figure 6 This is a schematic diagram of the secondary voltage and resonant current of a power converter provided in an embodiment of this disclosure.

[0016] Figure 7 This is a schematic diagram of the secondary voltage and resonant current of a power converter provided in an embodiment of this disclosure.

[0017] Figure 8 This is a schematic diagram of the secondary voltage and resonant current of a power converter provided in an embodiment of this disclosure.

[0018] Figure 9 This is a schematic diagram of the conduction sequence of the three-phase AC switching transistors of the power converter provided in an embodiment of this disclosure. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of this disclosure, exemplary embodiments of this disclosure are described below with reference to the accompanying drawings, including various details of the embodiments of this disclosure to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this disclosure. Similarly, for clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description.

[0020] Where there is no conflict, the various embodiments of this disclosure and the features thereof in the embodiments may be combined with each other.

[0021] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, the singular forms “a” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded. Words such as “connected” or “linked” are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect.

[0023] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and this disclosure, and will not be interpreted as having an idealized or overly formal meaning, unless expressly so defined herein.

[0024] As mentioned earlier, in power converters employing a half-bridge structure, a key challenge is how to achieve functional control of the power converter by controlling the on / off state and switching frequency of the DC and AC side switches. This functional control includes power regulation, soft switching of the switches, and efficiency optimization.

[0025] According to embodiments of this disclosure, a control method for a power converter is provided. This method can establish a power model of the power converter under multiple modulation degrees of freedom through fundamental wave analysis. By coordinating multiple control variables, it can not only achieve precise regulation of the three-phase output current, but also optimize the resonant current amplitude using redundant control degrees of freedom. At the same time, it can ensure the soft switching of all switching transistors of the power converter through constraint conditions, thereby reducing the switching losses on the AC side of the power converter and significantly improving the efficiency and soft switching performance of the power converter.

[0026] Figure 1 This is a schematic diagram of a power converter provided in an embodiment of this disclosure. (Refer to...) Figure 1 This is the circuit topology of a power converter, which includes an input-side circuit 11, an output-side circuit 12, and a resonant circuit connected between the input-side circuit 11 and the output-side circuit 12.

[0027] In some possible implementations, the input-side circuit 11 is connected to a DC voltage terminal, denoted as V. dc The input-side circuit 11 is a full-bridge structure, including two DC-side bridge arms, each containing switching transistors S1, S2 and S3, S4, used to convert DC voltage to AC voltage. The primary-side voltage and primary-side current of the input-side circuit 11 are respectively v p and i p .

[0028] In some possible implementations, the resonant circuit includes a transformer (with a turns ratio denoted as N1:N2) and a resonant capacitor C. r and resonant inductance L r The resonant current is i Lr The secondary voltage output to the output-side circuit 12 is denoted as v. s .

[0029] In some possible implementations, the output-side circuit 12 is a half-bridge structure, including three AC-side bridge arms. Each AC-side bridge arm includes a switching transistor group and a capacitor. One end of the switching transistor group and one end of the capacitor are connected as the output terminal of the AC-side bridge arm and connected to one phase of the three-phase AC power grid. The other end of the switching transistor group and the other end of the capacitor are respectively connected to the resonant circuit.

[0030] Reference Figure 1 Each of the three AC side bridge arm switch groups includes two switch transistors, namely S... a1 / S a2 S b1 / S b2 S c1 / S c2 The average current of the switching transistors of the three AC side bridge arms during the switching cycle is denoted as I. Sa I SbI Sc The capacitors are filter capacitors, with C respectively. a C b C c The capacitor voltage is denoted as v. ca v cb v cc One end of the switching transistor group and one end of the capacitor are connected as the output terminals of the AC side bridge arm, and are respectively connected through the filter inductor L. a L b L c Connected to one phase of a three-phase AC power grid, the phase voltages on the AC side are denoted as v. a v b v c .

[0031] It should be understood that Figure 1 This is merely a schematic diagram of a power converter. Those skilled in the art can configure the circuit topology of the power converter according to actual conditions, and this disclosure does not impose any restrictions on it.

[0032] In some possible implementations, the power converter also includes a controller (not shown) connected to the input-side circuit 11 and the output-side circuit 12, respectively, for controlling the switching transistors in the power converter. The controller can execute the control method of the power converter according to embodiments of this disclosure. The controller can be implemented in hardware or software, and this disclosure does not limit its implementation.

[0033] Figure 2 A flowchart illustrating a control method for a power converter provided in an embodiment of this disclosure. (Refer to...) Figure 2 The control method includes the following steps S21-S23.

[0034] In step S21, the average current value of the three AC side bridge arms of the output side circuit during the switching cycle is determined according to the set current value of the three-phase AC terminals.

[0035] In step S22, the switching phase shift angle of the power converter's switching transistor during the switching cycle and the target operating frequency of the power converter are determined based on the average current value, the DC sampling voltage value of the DC voltage terminal, and the AC voltage sampling value of the three-phase AC terminal.

[0036] In step S23, a drive signal is generated based on the switch phase shift angle and the target operating frequency. The drive signal is used to drive the switching transistor in the power converter.

[0037] For example, such as Figure 1The control of the power converter shown includes two time dimensions: the switching cycle and the AC cycle. At the switching cycle level, control is achieved by controlling the DC-side switches (S1~S4) and the AC-side bidirectional switches (S...). a1,2 S b1,2 S c1,2 Switching the primary and secondary sides on and off will generate different primary and secondary AC voltages (primary voltage v). p Secondary voltage v s ), thereby affecting L r and C r The resonance process generates a corresponding resonant current i. Lr In AC cycle-level control: via AC-side bidirectional switching transistor (S... a1,2 S b1,2 S c1,2 The resonant current is distributed to ultimately obtain the desired three-phase current.

[0038] In some possible implementations, the input-side circuit includes a first switching group and a second switching group. The switches in the first switching group are complementary in conduction, and the switches in the second switching group are complementary in conduction. The first phase shift angle of the switching of the first switching group is 0. The switching phase shift angle includes the second phase shift angle of the switching of the second switching group and the fundamental equivalent phase shift angle.

[0039] The first switching transistor group includes transistors S1 and S2, and the second switching transistor group includes transistors S3 and S4. In each switching cycle of the power converter, DC-side switching transistors S1-S4 employ phase-shift modulation, with S1 and S2 conducting complementaryly, and S3 and S4 conducting complementaryly. Assuming the first phase shift angle for switching transistors S1 and S2 is 0, then the second phase shift angle lagging behind the switching of the second switching transistor group is... dc That is, S3 lags behind the phase shift angle of S1. dc Meanwhile, taking the zero-crossing point of the fundamental current as the reference point, the equivalent phase shift angle of the fundamental current at the moment S1 is turned on is denoted as... dc1 .

[0040] In some possible implementations, based on the magnitude relationship between the AC voltage sampling values, the L-phase, M-phase, and S-phase bridge arms can be determined from the three AC-side bridge arms a, b, and c. Then, the conduction sequence of the three-phase switches is determined based on the sign of the average current of the switching transistors in the M-phase bridge arm. If the average current of the switching transistors in the M-phase bridge arm is positive, the conduction sequence of the three-phase switches is one of SML, LSM, or MLS; if the average current of the switching transistors in the M-phase bridge arm is negative, the conduction sequence of the three-phase switches is one of LMS, MSL, or SLM.

[0041] In some possible implementations, a switching cycle can be set within [ ac1 , ac2 In the specified interval, the switch of the phase with the largest absolute value of average current is always turned on. In the SML, LSM, and MLS cases, the currents of phases S, L, and M are positive and reach their maximum absolute values, respectively. S12 These correspond to the currents of phases S, L, and M, respectively. In the cases of LMS, MSL, and SLM, the currents of phases L, M, and S are negative and their absolute values ​​reach their maximum values, respectively. S12 These correspond to the currents of phase L, phase M, and phase S, respectively.

[0042] Among them, the L phase, M phase, and S phase are ordered according to the magnitude relationship between the AC voltage sampling values, i.e., V L >V M >V S This allows V to L V M V S respectively compared with AC voltage sampling value v a v b v c Correspondingly, it can be further determined that [ ac1 , ac2 ]、[ ac2 , ac3 ]、[ ac3 , ac1 The interval [+2π] specifically refers to which of the three phases a, b, and c is turned on. This maps phases a, b, and c to phases L, M, and S, where different conduction sequences in phases L, M, and S correspond to V1~V3 and I. S12 ~I S31 Thus, using the L, M, and S phases as a medium, V1~V3 and I... S12 ~I S31 With respect to the voltage v of the specific circuit switching transistor group a ~v b and current I Sa ~I Sc To put it in perspective.

[0043] In some possible implementations, the three AC-side bridge arms can be divided into a first-phase bridge arm, a second-phase bridge arm, and a third-phase bridge arm according to the conduction sequence of the switching transistors; the voltage of the first-phase bridge arm is V1, and the current is I. S12 The voltage of the second phase bridge arm is V2, and the current is I. S23The voltage of the third phase bridge arm is V3, and the current is I. S31 It should be understood that those skilled in the art can determine the first phase arm, the second phase arm, and the third phase arm based on the actual situation, and this disclosure does not impose any restrictions on this.

[0044] Accordingly, the output-side circuit includes the third switching transistor group of the first phase bridge arm, the fourth switching transistor group of the second phase bridge arm, and the fifth switching transistor group of the third phase bridge arm. The switching phase shift angle also includes the third phase shift angle at which the switching transistors of the third switching transistor group begin to conduct simultaneously. ac1 The fourth phase shift angle is when the switching transistors of the third switching group simultaneously turn on and the switching transistors of the fourth switching group simultaneously turn on. ac2 The fifth phase shift angle is when the switching transistors of the fourth switching group simultaneously turn on and the switching transistors of the fifth switching group simultaneously turn on. ac3 .

[0045] Among them, at any given time, the AC side bidirectional switch S a1,2 S b1,2 S c1,2 Only one set of switching transistors is turned on, ensuring that the resonant current has a flow path while avoiding capacitance C. a ~C c For a short circuit, the phase shift angles at the turn-on times of the third, fourth, and fifth switching transistor groups are denoted as . ac1 ~ ac3 The switching frequency of all switching transistors is denoted as f. s Therefore, theoretically, a power converter has 6 degrees of freedom for control. dc , dc1 , ac1 , ac2 , ac3 , f s On the other hand, since the AC side is star-connected, the three-phase output current control objective actually has only two independent controlled variables; the zero-crossing point of the fundamental frequency of the resonant current is also a controlled variable. The redundant three control degrees of freedom can be used to achieve objectives such as minimum resonant current and soft-switching control.

[0046] Figure 3 This is a schematic diagram of the voltage and current waveforms of a power converter provided in an embodiment of this disclosure. Figure 3In the diagram, the horizontal axis represents time t, and the vertical axis, from top to bottom, represents the voltages of DC-side switches S1 and S2 (high voltage indicates the switch is on, low voltage indicates the switch is off); the voltages of S3 and S4 (high voltage indicates the switch is on, low voltage indicates the switch is off); and the primary-side voltage v. p Secondary voltage v s ; Resonant current i Lr .

[0047] Reference Figure 3 ,exist Figure 1 In the resonant single-stage DC / AC power converter topology shown, the primary voltage v of the transformer... p When S1 and S3 are both on, the voltage V at the DC voltage terminal is... dc When S2 and S4 are both on, it is -V dc It is 0 at other times, such as Figure 3 As shown. Taking the zero-crossing point of the fundamental frequency of the resonant current as the reference point, if dc1 A value greater than zero indicates that the turn-on time of S1 lags behind the reference point, and vice versa. When the resonant current approaches a sine wave, to achieve soft switching of all DC-side switching transistors, the following requirements must be met. dc1 + dc ≤ yu .because dc It must be greater than 0, therefore dc1 It must be less than zero. Among them, yu This indicates the setting value for achieving soft switching of all DC-side switching transistors. yu Theoretically, the value should be 0, but in practical applications, it can be set to any small value as a margin for the circuit. This disclosure... yu There are no restrictions on the specific values ​​that can be obtained.

[0048] In some possible implementations, the primary voltage v of the transformer p It can be expressed as the following formula (1).

[0049] (1).

[0050] In formula (1), n ​​represents the harmonic order of the coefficients of the Fourier series; a0 represents the primary voltage v. p The DC component of the Fourier series; a n Indicates the primary voltage v p The coefficients of the cosine terms in the Fourier series; b nIndicates the primary voltage v p The coefficients of the sine term in the Fourier series; ω s ω represents the switching angular frequency of the transistor. s =2π / T s ;T s t represents the switching period, and t represents any time.

[0051] In formula (1), a0 and a n b n It can be expressed as the following formula (2).

[0052] (2).

[0053] In some possible implementations, the primary voltage v of the transformer... p By performing a Fourier series expansion, we can obtain the following formula (3).

[0054] (3).

[0055] In formula (3), n represents the harmonic order; n=1, 3, 5, … indicates that the waveform contains only odd harmonic components.

[0056] In some possible implementations, the primary voltage v p The fundamental component v of p1 It can be expressed as the following formula (4).

[0057] (4).

[0058] In formula (4), a1 represents the primary voltage v p The fundamental coefficients of the cosine terms of the Fourier series; b1 represents the primary voltage v. p The fundamental coefficient of the sine term of the Fourier series.

[0059] In some possible implementations, at any time t, the AC side switch S a1,2 S b1,2 S c1,2 When exactly one set of switching transistors is turned on simultaneously, the secondary voltage v can be obtained. s The waveform is as follows Figure 3 As shown. When S k1,2 (k=a, b, c) are simultaneously turned on, that is, when both switches of one bridge arm are turned on at the same time, the secondary voltage v s Equal to capacitance C k voltage v Ck This can also be considered equal to the AC voltage value at the three-phase AC terminals. Since the on / off times of the AC-side switching transistors are not yet determined, they will be represented by V1, V2, and V3 for now. ac1, ac2 ]、[ ac2 , ac3 ]、[ ac3 , ac1 The secondary voltage v in the interval [+2π] s voltage value, ac1 , ac2 , ac3 All reference points are taken at the zero-crossing point of the fundamental frequency of the resonant current. ac1 < ac2 < ac3 .

[0060] In some possible implementations, the secondary voltage v s The Fourier series expansion can be expressed as the following formula (5).

[0061] (5).

[0062] In formula (5), n represents the harmonic order; c0 represents the secondary voltage v. s The DC component of the Fourier series; c n Indicates the secondary voltage v s The coefficients of the cosine terms in the Fourier series; d n Indicates the secondary voltage v s The coefficients of the sine term in the Fourier series. In formula (5), c0, c... n d n It can be represented as follows.

[0063] .

[0064] Wherein, the secondary voltage v s The DC component c0 is represented as follows.

[0065] .

[0066] Wherein, the secondary voltage v s The fundamental component v of s1 It is expressed as the following formula (6).

[0067] (6).

[0068] In formula (6), c1 represents the secondary voltage v sThe fundamental coefficient of the cosine term of the Fourier series; d1 represents the secondary voltage v. s The fundamental coefficients of the sine term of the Fourier series. Among them, c1 and d1 in formula (6) can be expressed as follows.

[0069] .

[0070] In some possible implementations, to simplify the analysis of the resonant current, the fundamental wave analysis method is used to calculate and simplify the resonant current, that is, only the primary voltage v is considered. p and secondary voltage v s The fundamental component (Equations (4) and (6)). In this case, the resonant inductor L can be combined. r and resonant capacitor C r Calculate the resonant current i Lr The fundamental component is shown in formula (7).

[0071] (7).

[0072] In formula (7), ω and ω s Both represent the switching angular frequency of the switching transistor, k. iLr_cos Represents the resonant current i Lr The cosine coefficients of the fundamental component; k iLr_sin Represents the resonant current i Lr The sinusoidal coefficients of the fundamental component. Where, k iLr_cos and k iLr_sin It can be represented as follows.

[0073]

[0074] .

[0075] Among them, let k iLr_cos =0, which allows the resonant current i Lr The initial phase is zero, and the simplified calculation is shown in formula (8).

[0076] (8).

[0077] In some possible implementations, when given an output current command I... Sa I Sb I Sc At this time, the average current of the switching transistor in each switching cycle can be calculated separately. To simplify subsequent calculations, I Sa I Sb I Sc The different intervals will be denoted as I. S12 I S23 I S31 IS12 Indicates in [ ac1 , ac2 The average current flowing through the corresponding switching transistor in the interval corresponds to V1; I S23 Indicates in [ ac2 , ac3 The average current flowing through the corresponding switching transistor in the interval corresponds to V2; I S31 Indicates in [ ac3 , ac1 The average current flowing through the corresponding switching transistor in the +2π interval corresponds to V3, and is set within one switching cycle [ ac1 , ac2 The switch of the phase with the largest absolute value of average current is always turned on within the interval. Although there are three equations, there are only two independent equations because the average value of the fundamental resonant current in each switching cycle is zero.

[0078] Among them, in [ ac1 , ac2 ]、[ ac2 , ac3 ]、[ ac3 , ac1 The average current I flowing through the corresponding switching transistor in the interval +2π] S12 (θ), I S23 (θ), I S31 (θ), as shown in formula (9).

[0079] (9).

[0080] In formula (9), θ represents the instantaneous phase angle of the current at the three-phase AC terminals.

[0081] Figure 4 This is a schematic diagram of the resonant current of a power converter provided in an embodiment of this disclosure. Figure 4 In the diagram, the horizontal axis represents time t, and the vertical axis, from top to bottom, represents the resonant current i. Lr 、[ ac1 , ac2 The current value flowing through the corresponding switching transistor in the interval, ac2 , ac3 The current value flowing through the corresponding switching transistor in the interval and [ ac3 , ac1 The current value flowing through the corresponding switching transistor in the +2π interval.

[0082] In some possible implementations, equations (7) and (9) can be used as the power model under multiple modulation degrees of freedom of the power converter. In equation (9), when the AC current command value is given, the average current of the switching transistor in each switching cycle can be calculated. Theoretically, all control variables of the power converter can be solved by combining equations (7) and (9).

[0083] In some possible implementations, the average current value of the three AC-side bridge arms of the output circuit during the switching cycle can be determined in step S21 based on the set current value of the three-phase AC terminals. The set current value of the three-phase AC terminals can be a preset current command value, i.e., the desired current value during the switching cycle. By averaging the set current value during the switching cycle, the average current value of the three AC-side bridge arms during the switching cycle can be obtained, corresponding to I in the above formula (9). S12 (θ), I S23 (θ), I S31 (θ).

[0084] In some possible implementations, the DC sampling voltage value at the DC voltage terminal corresponds to Figure 1 And the voltage V in the above formula (8) dc .

[0085] In some possible implementations, the AC voltage sample value at the three-phase AC terminals can be the voltage value across the capacitor, or the voltage value at the connection point between the filter circuit and the three-phase AC mains. That is, corresponding to... Figure 1 The sampled voltage values ​​of the AC side bridge arms a, b, and c can be represented by the filter capacitor C. a C b C c capacitor voltage v ca v cb v cc It can also be the phase voltage v on the AC side. a v b v c This disclosure does not restrict the selection location of the AC voltage sampling values ​​at the three-phase AC terminals. This approach allows for more flexible voltage sampling methods and improves the overall flexibility of voltage sampling.

[0086] In some possible implementations, the conduction sequence of the three AC side bridge arms can be determined based on the magnitude relationship between the AC voltage sample values. The first phase bridge arm, the second phase bridge arm, and the third phase bridge arm are determined based on the conduction sequence, and the corresponding AC voltage sample values ​​correspond to the secondary voltage v in the above formula (7). s The voltage values ​​are V1, V2, and V3.

[0087] In some possible implementations, in step S22, based on the average current value, the DC sampled voltage value at the DC voltage terminal, and the AC voltage sampled value at the three-phase AC terminal, all control variables, including the switching phase shift angle of the power converter switching transistor during the switching cycle, can be solved by simultaneously applying formulas (7) and (9). dc , dc1 , ac1 , ac2 , ac3 and the target operating frequency f of the power converter s .

[0088] In some possible implementations, step S22 may include: determining, according to the fundamental model, a first relationship between the first fundamental component of the primary voltage of the input circuit and the DC sampled voltage value, and a second relationship between the second fundamental component of the secondary voltage of the output circuit and the AC voltage sampled value; and determining the switching phase shift angle and the target operating frequency according to the average current value, the first relationship, and the second relationship.

[0089] In other words, based on the fundamental wave model, the first fundamental wave component v of the primary voltage can be determined through the derivation process of the above formulas (1)-(4). p1 With DC sampling voltage value V dc The first relationship is given by formula (4); based on the fundamental wave model, through the derivation process of the above formulas (5) and (6), the second fundamental wave component v of the secondary voltage can be determined. s1 The second relationship with the AC voltage sampling values ​​V1, V2, and V3 is given by formula (6); then, based on the average current value, the first relationship, and the second relationship, formulas (7) and (9) are combined to calculate the switching phase shift angle. dc , dc1 , ac1 , ac2 , ac3 and the target operating frequency f s .

[0090] This approach simplifies the solution of control variables in power converters, reduces computational complexity, and improves processing efficiency.

[0091] In some possible implementations, in step S23, a drive signal is generated based on the switching phase shift angle and the target operating frequency, and the drive signal is used to drive the switching transistors in the power converter.

[0092] According to embodiments of this disclosure, a power model of a power converter under multiple modulation degrees of freedom can be established through fundamental wave analysis. By coordinating multiple control variables, precise control of the three-phase output current of the power converter can be achieved, thereby reducing the switching losses on the AC side of the power converter and improving the efficiency of the power converter.

[0093] The control variables (switching phase shift angle) of the power converter are determined through the above processing method. dc , dc1 , ac1 , ac2 , ac3 and target operating frequency f s In the case of ), there are redundant control degrees of freedom among these control variables, so the minimum resonant inductor current and soft switching condition can also be used as additional control objectives.

[0094] In some possible implementations, step S22 may include: determining the minimum amplitude of the resonant current of the resonant circuit and the operating mode corresponding to the minimum amplitude based on the average current value, the DC sampling voltage value, the AC voltage sampling value, and the transformer turns ratio of the resonant circuit.

[0095] Based on the phase shift angle constraint corresponding to the operating mode, the average current value, the first fundamental component of the primary voltage of the input circuit and the first relationship between the DC sampling voltage value, and the second fundamental component of the secondary voltage of the output circuit and the second relationship between the AC voltage sampling value, the switch phase shift angle and the target operating frequency are determined.

[0096] The driving signal generated based on the switch phase shift angle and the target operating frequency minimizes the amplitude of the resonant current when the power converter transmits a preset power.

[0097] For example, there are several ways to achieve the minimum resonant current throughout the entire AC cycle. One method is to start from the primary side of the transformer, making the DC current i of the transformer... p Minimum, equivalent to resonant current i Lr=(N2 / N1)×i p Minimum; another is to start from the AC side of the transformer, so that the resonant current i Lr Minimum, such as Figure 1 As shown.

[0098] In some possible implementations, to achieve the minimum DC-side current throughout the entire AC cycle, the phase shift angle of the DC-side switch needs to be set in each switching cycle. dc The resonant current i is 0. Lr With primary voltage v p In phase ( dc1 Also 0), such as Figure 5 As shown.

[0099] Figure 5 This is a schematic diagram of the primary-side voltage and resonant current of a power converter provided in an embodiment of this disclosure. Figure 5 In the diagram, the horizontal axis represents time t, and the vertical axes represent the primary voltage v. p and resonant current i Lr .

[0100] In this case, the converter power P is calculated from the DC side. dc_sw As shown in formula (10).

[0101] (10).

[0102] Among them, due to k iLr_cos =0, therefore the fundamental amplitude of the resonant current is the sine coefficient k. iLr_sin .

[0103] In this case, the converter power is calculated from the AC side as shown in formula (11).

[0104] (11).

[0105] By combining formulas (10) and (11), the minimum value of the fundamental amplitude of the resonant current starting from the DC side can be obtained as shown in formula (12).

[0106] (12).

[0107] It can be seen that when the phase shift angle constraint is satisfied... dc =0 and dc1 + dc When =0, k iLr_sin Reaching the minimum value corresponds to the physical case where the primary-side output is a square wave with a 50% pulse width and is in phase with the resonant current, such as... Figure 5 As shown. In this operating mode, the required resonant current amplitude is minimized when transmitting a given power.

[0108] In some possible implementations, this operating mode can be referred to as the first operating mode. The first phase shift angle constraint corresponding to the first operating mode includes: the second phase shift angle. dc Equivalent phase shift angle of the fundamental wave dc1 The sum is 0.

[0109] In some possible implementations, substituting formula (7) into formula (9) can also yield the amplitude k of the resonant current from the AC side. iLr_sin As shown in formula (13).

[0110] (13).

[0111] Figure 6 This is a schematic diagram of the secondary voltage and resonant current of a power converter provided in an embodiment of this disclosure. Figure 7 This is a schematic diagram of the secondary voltage and resonant current of a power converter provided in an embodiment of this disclosure. Figure 6 and Figure 7 In the diagram, the horizontal axis represents time t, and the vertical axes represent the secondary voltage v. s and resonant current i Lr .

[0112] According to formula (13), the phase current with the largest absolute value is positive (I). s12 When ≥0), set a phase shift angle limit. ac1 =0、 ac2 =π when k iLr_sin Get the minimum value ,like Figure 6 As shown. When the phase current with the largest absolute value is negative (I... s12 When <0), set phase angle limit conditions. ac1 =π、 ac2 When k = 2π iLr_sin Get the minimum value ,like Figure 7 As shown.

[0113] In some possible implementations, this operating mode can be referred to as the second operating mode. The second phase shift angle constraint corresponding to the second operating mode includes: the phase current with the largest absolute value among the average current values ​​is a positive value (I). s12 In the case of ≥0), the third phase shift angle ac1 The fourth phase shift angle is 0. ac2 The value is π; among the average current values, the phase current with the largest absolute value is negative (I). s12 In the case of <0), the third phase shift angle ac1 The fourth phase shift angle is π. ac2 It is 2π.

[0114] In practice, the choice of which working mode to select depends on the relationship between the two minimum values.

[0115] In some possible implementations, the minimum amplitude of the resonant current of the resonant circuit and the corresponding operating mode can be determined based on the average current value, the DC sampling voltage value, the AC voltage sampling value, and the transformer turns ratio of the resonant circuit. This step includes: determining a first minimum amplitude of the resonant current based on the first phase shift angle constraint, the average current value, the DC sampling voltage value, and the transformer turns ratio of the resonant circuit; determining a second minimum amplitude of the resonant current based on the absolute value of the phase current with the largest absolute current value in the average current value; determining the operating mode as a first operating mode if the first minimum value is greater than or equal to the second minimum value; and determining the operating mode as a second operating mode if the first minimum value is less than the second minimum value.

[0116] For example, based on formula (12), the resonant current amplitude reaches its first minimum value when the first phase shift angle constraint is met. According to the average current value I S12 (θ), I S23 (θ), I S31 (θ); DC sampling voltage value V dc The first minimum value of the resonant current amplitude can be calculated from the AC voltage sampling values ​​V1, V2, V3 and the transformer turns ratio N1:N2 of the resonant circuit.

[0117] In some possible implementations, based on formula (13), the second minimum value of the resonant current amplitude is determined according to the absolute value of the phase current with the largest absolute value among the average current values. .

[0118] In some possible implementations, if the first minimum value is greater than or equal to the second minimum value, that is... If the first minimum value is less than the second minimum value, then the power converter is determined to operate in the first operating mode; conversely, if the first minimum value is less than the second minimum value, then the power converter is determined to operate in the second operating mode. When all other conditions are the same, different transformer turns ratios N1:N2 can be set during circuit design to control the power converter to operate in different operating modes.

[0119] In this way, the amplitude of the resonant current of the power converter when transmitting a given power can be reduced, thereby improving the efficiency of the power converter.

[0120] In some possible implementations, after determining the operating mode of the power converter, all control variables, including the switching phase shift angle of the power converter switch during the switching cycle, can be solved by combining formulas (7) and (9) based on the phase shift angle constraint corresponding to the operating mode, the average current value, the first relationship between the first fundamental component of the primary voltage of the input circuit and the DC sampling voltage value, and the second relationship between the second fundamental component of the secondary voltage of the output circuit and the AC voltage sampling value. dc , dc1 , ac1 , ac2 , ac3 and the target operating frequency f of the power converter s .

[0121] Furthermore, in step S23, a drive signal is generated based on the switch phase shift angle and the target operating frequency to drive the switching transistors in the power converter. In this case, the drive signal generated based on the switch phase shift angle and the target operating frequency minimizes the amplitude of the resonant current of the power converter when transmitting a preset power.

[0122] In this way, the control objective of minimizing the resonant inductor current can be achieved, reducing the amplitude of the resonant current when the power converter transmits a given power, and further improving the efficiency of the power converter.

[0123] Based on achieving the above control objectives, the performance of the power converter can be further optimized by achieving zero-voltage switching of the power converter's switching transistors.

[0124] In some possible implementations, when the operating mode is the first operating mode, determining the switch phase shift angle and the target operating frequency includes: when the first operating mode employs a first modulation strategy, determining the third phase shift angle, the fourth phase shift angle, the fifth phase shift angle, and the target operating frequency based on the first phase shift angle constraint, the average current value, the first relationship, and the second relationship, wherein the first modulation strategy includes: the fourth phase shift angle = π + the third phase shift angle; or the fourth phase shift angle = π - the third phase shift angle, that is... ac2 =π+ ac1 or ac2 =π- ac1 .

[0125] The driving signal generated based on the switching phase shift angle and the target operating frequency enables the power converter's switching transistors to switch at zero voltage.

[0126] For example, in the first operating mode, based on the first phase shift angle constraint, the second phase shift angle... dc Equivalent phase shift angle of the fundamental wave dc1 The sum is 0. In this case, the solution formula in the resonant current analysis can be simplified; furthermore, to simplify the solution, it is also possible to... ac1 ~ ac3 Given a single variable or the relationship between two variables.

[0127] In some possible implementations, a first modulation strategy can be set in the first operating mode, which includes: the fourth phase shift angle = π + the third phase shift angle; or, the fourth phase shift angle = π - the third phase shift angle, that is... ac2 =π+ ac1 or ac2 =π- ac1 In this case, cos ac2 =-cos ac1 Formula (13) can be obtained, as follows.

[0128] (14).

[0129] In some possible implementations, when the first modulation strategy is used in the first operating mode, the third phase shift angle is determined based on the average current value, the first relationship, and the second relationship. ac1 Fourth phase shift angle ac2 Fifth phase shift angle ac3 and target operating frequency f s .

[0130] Based on formula (14), the third phase shift angle can be solved. ac1 and the fifth phase shift angle ac3 Therefore, the fourth phase shift angle is determined. ac2 Among these requirements, the resonant impedance must be variable, meaning that frequency modulation is necessary to fully satisfy formula (14) and obtain the desired solution. ac1 ~ ac3 It meets the requirements for soft switching.

[0131] Furthermore, in step S23, a drive signal is generated based on the switching phase shift angle and the target operating frequency to drive the switching transistors in the power converter. In this case, the drive signal generated based on the switching phase shift angle and the target operating frequency causes the switching transistors of the power converter to switch at zero voltage.

[0132] In this way, the control objective of zero-voltage switching of the power converter's switching transistors can be achieved, reducing the switching losses on the AC side of the power converter and further improving the efficiency and soft-switching performance of the power converter.

[0133] In some possible implementations, when the operating mode is the first operating mode, determining the switch phase shift angle and the target operating frequency includes:

[0134] When the second modulation strategy is adopted in the first operating mode, the third phase shift angle, the fourth phase shift angle, the fifth phase shift angle and the target operating frequency are determined according to the first phase shift angle constraint, the average current value, the first relationship and the second relationship. The second modulation strategy includes: when the phase current with the largest absolute value of the current in the average current value is positive, the fourth phase shift angle is π; when the phase current with the largest absolute value of the current in the average current value is negative, the third phase shift angle is π.

[0135] The driving signal generated based on the switching phase shift angle and the target operating frequency enables the power converter's switching transistors to switch at zero voltage.

[0136] For example, a second modulation strategy can also be set in the first operating mode, which includes: when the phase current with the largest absolute value in the average current value is positive, the fourth phase shift angle... ac2 The third phase shift angle is π; when the phase current with the largest absolute value in the average current values ​​is negative, the third phase shift angle is π. ac1 It is π.

[0137] At the fourth phase shift angle ac2 When the value is equal to π, formula (15) can be obtained as follows.

[0138] (15).

[0139] Based on formula (15), the third phase shift angle can be solved. ac1 and the fifth phase shift angle ac3 Among these requirements, the resonant impedance must be variable, meaning that frequency modulation is necessary to fully satisfy formula (15) and obtain the desired solution. ac1 ~ ac3 It meets the requirements for soft switching.

[0140] At the third phase shift angle ac1 When the value is equal to π, formula (16) can be obtained as follows.

[0141] (16).

[0142] Based on formula (16), the fourth phase shift angle can be solved. ac2 and the fifth phase shift angle ac3 Among these requirements, the resonant impedance must be variable, meaning that frequency modulation is necessary to fully satisfy formula (16) and ensure that the solution yields the desired result. ac1 ~ ac3 It meets the requirements for soft switching.

[0143] Furthermore, in step S23, a drive signal is generated based on the switching phase shift angle and the target operating frequency to drive the switching transistors in the power converter. In this case, the drive signal generated based on the switching phase shift angle and the target operating frequency causes the switching transistors of the power converter to switch at zero voltage.

[0144] In this way, the control objective of zero-voltage switching of the power converter's switching transistors can be achieved, reducing the switching losses on the AC side of the power converter and further improving the efficiency and soft-switching performance of the power converter.

[0145] It should be understood that the first modulation strategy and the second modulation strategy described above are merely examples of modulation strategies in the first operating mode. Those skilled in the art can set various modulation strategies in the first operating mode according to actual conditions, and this disclosure does not impose any restrictions on them.

[0146] In some possible implementations, when the operating mode is the second operating mode, determining the switch phase shift angle and the target operating frequency includes: when the second operating mode adopts a third modulation strategy, determining the second phase shift angle, the fundamental equivalent phase shift angle, the fifth phase shift angle, and the target operating frequency based on the second phase shift angle constraint, the average current value, the first relationship, and the second relationship, wherein the third modulation strategy includes: the sum of the second phase shift angle and the fundamental equivalent phase shift angle is less than or equal to 0.

[0147] The driving signal generated based on the switching phase shift angle and the target operating frequency enables the power converter's switching transistors to switch at zero voltage.

[0148] For example, in the second operating mode, based on the second phase shift angle constraint, the phase current with the largest absolute value among the average current values ​​is a positive value (I). s12 In the case of ≥0), the third phase shift angle ac1 The fourth phase shift angle is 0. ac2 The value is π; among the average current values, the phase current with the largest absolute value is negative (I). s12 In the case of <0), the third phase shift angle ac1 The fourth phase shift angle is π. ac2 The value is 2π. In this case, to satisfy the soft-switching requirement of the DC-side switch, a third modulation strategy can be set, including the fundamental equivalent phase shift angle. dc1 +Second phase shift angle dc ≤0.

[0149] Among them, the formula can be set dc1 + dc =0, in practical applications, in order to achieve soft switching, the current should have a certain margin, that is... dc1 + dc It can be set to a value less than zero.

[0150] The phase current with the largest absolute value in the average current values ​​is the positive value (I). s12 In the case of ≥0), formula (17) can be obtained, as follows.

[0151] (17).

[0152] The phase current with the largest absolute value in the average current values ​​is negative (I). s12 When <0), formula (18) can be obtained, as follows.

[0153] (18).

[0154] In some possible implementations, the second phase shift angle, the fundamental equivalent phase shift angle, the fifth phase shift angle, and the target operating frequency are determined based on the second phase shift angle constraint, the average current value, the first relationship, and the second relationship. That is, the second phase shift angle in these two cases is solved based on formulas (17) and (18), respectively. dc Equivalent phase shift angle of fundamental wave dc1 and the fifth phase shift angle ac3 So that the solution is dc , dc1 and ac1 ~ ac3 It must meet the requirements for soft switching. In practical applications, to achieve soft switching, a certain margin in the current should be provided, that is... ac1 ~ ac3 When making presets, a certain margin can be left.

[0155] Furthermore, in step S23, a drive signal is generated based on the switching phase shift angle and the target operating frequency to drive the switching transistors in the power converter. In this case, the drive signal generated based on the switching phase shift angle and the target operating frequency causes the switching transistors of the power converter to switch at zero voltage.

[0156] In this way, the control objective of zero-voltage switching of the power converter's switching transistors can be achieved, reducing the switching losses on the AC side of the power converter and further improving the efficiency and soft-switching performance of the power converter.

[0157] It should be understood that the above-described third modulation strategy is merely an example of a modulation strategy in the second operating mode. Those skilled in the art can set various modulation strategies in the second operating mode according to actual conditions, and this disclosure does not impose any restrictions on this.

[0158] As mentioned earlier, the three AC side arms can be divided into the first phase, second phase, and third phase arms according to the conduction sequence of the switching transistors; the voltage of the first phase arm is V1, and the current is I. S12 The voltage of the second phase bridge arm is V2, and the current is I. S23 The voltage of the third phase bridge arm is V3, and the current is I. S31 .

[0159] The following is an application example of the switching transistor driving strategy for power converters.

[0160] Under the condition of unity power factor (PF=1), the amplitudes of the AC voltages of phases A, B, and C at the three-phase AC grid terminals are equal, and the amplitudes of the AC currents are also equal. Specifically, the phases of phase A voltage and current are the same, with an initial phase of 0°; the phase of phase B voltage lags phase A voltage by 120°, and the phase of phase C voltage lags phase B voltage by 120°; furthermore, the phase of phase B current lags phase A current by 120°, and the phase of phase C current lags phase B current by 120°.

[0161] Figure 8 This is a schematic diagram of the switching transistor driving strategy of the power converter provided in the embodiments of this disclosure. Figure 8 The horizontal axis represents phase, the vertical axis of the upper half of the image represents voltage, and the vertical axis of the lower half of the image represents current.

[0162] Reference Figure 8 Corresponding to A, B, and C, Figure 8 The voltage values ​​V of the three AC side bridge arms in the upper part of the image ca V cb V cc The current value I in the curve and the lower half of the image Sa I Sb I Sc The curves also conform to the above-mentioned rules for amplitude and phase, and the current and voltage are in phase.

[0163] Under the above-mentioned conditions, the multiple phase values ​​at which the magnitude relationship between voltage values ​​switches are 30°, 90°, 150°, 210°, 270°, and 330°. Furthermore, the AC cycle is divided into a corresponding number of phase regions based on the multiple phase values. For example, under the above phase values ​​of 30°, 90°, 150°, 210°, 270°, and 330°, one AC cycle can be divided into 6 phase regions.

[0164] In some possible implementations, the phase value ranges corresponding to the plurality of phase regions are 330°~30°, 30°~90°, 90°~150°, 150°~210°, 210°~270°, and 270°~330°, respectively.

[0165] Reference Figure 8 The upper half of the image shows three curves corresponding to the voltage values ​​V of the three AC side arms. ca V cb V cc Under the aforementioned conditions, an alternating current cycle is divided into phase regions V-1, V-2, V-3, V-4, V-5, and V-6. Phase region V-1 corresponds to a phase value range of 330° to 30°; phase region V-2 corresponds to a phase value range of 30° to 90°; phase region V-3 corresponds to a phase value range of 90° to 150°; phase region V-4 corresponds to a phase value range of 150° to 210°; phase region V-5 corresponds to a phase value range of 210° to 270°; and phase region V-6 corresponds to a phase value range of 270° to 330°.

[0166] In some possible implementations, for any phase region, the AC side bridge arm with the highest voltage value in that phase region is determined as the L-phase bridge arm, the AC side bridge arm with the lowest voltage value is determined as the S-phase bridge arm, and the AC side bridge arm with the middle voltage value is determined as the M-phase bridge arm, i.e., V L >V M >V S .

[0167] In other words, under the above-mentioned conditions, for the phase region V-1 (330°~30°), V cc >V ca >V cb Then, AC side bridge arm c is the L-phase bridge arm, AC side bridge arm a is the M-phase bridge arm, and AC side bridge arm b is the S-phase bridge arm. For phase region V-2 (30°~90°), V ca >V cc >V cb Then, AC side bridge arm a is the L-phase bridge arm, AC side bridge arm c is the M-phase bridge arm, and AC side bridge arm b is the S-phase bridge arm. For phase region V-3 (90°~150°), V ca >V cb >V cc Then, AC side bridge arm a is the L-phase bridge arm, AC side bridge arm b is the M-phase bridge arm, and AC side bridge arm c is the S-phase bridge arm. For phase region V-4 (150°~210°), V cb >V ca >V ccThen, AC side bridge arm b is the L-phase bridge arm, AC side bridge arm a is the M-phase bridge arm, and AC side bridge arm c is the S-phase bridge arm. For phase region V-5 (210°~270°), V cb >V cc >V ca Then, AC side bridge arm b is the L-phase bridge arm, AC side bridge arm c is the M-phase bridge arm, and AC side bridge arm a is the S-phase bridge arm. For phase region V-6 (270°~330°), V cc >V cb >V ca Then, AC side bridge arm c is the L-phase bridge arm, AC side bridge arm b is the M-phase bridge arm, and AC side bridge arm a is the S-phase bridge arm.

[0168] For any phase region, based on the current command value of the M-phase bridge arm in that phase region, sub-regions with current command values ​​less than zero and sub-regions with current command values ​​greater than zero can be determined respectively, thus obtaining... Figure 8 The system is divided into 12 sub-regions, numbered 1 to 12. The driving strategy for the bridge arm switches in each sub-region is then configured.

[0169] In the example, for subregion 1, V cc >V ca >V cb Therefore, AC side bridge arm c is the L-phase bridge arm, AC side bridge arm a is the M-phase bridge arm, and AC side bridge arm b is the S-phase bridge arm. The average current of the switching transistors in the M-phase bridge arm is positive, and the absolute value of the current in the S-phase bridge arm reaches its maximum and is negative. Therefore, the conduction sequence is SML, and the first, second, and third phase bridge arms are b, a, and c, respectively. Furthermore, the voltage V1 of the first phase bridge arm can be determined as V... cb Current I S12 =I Sb The voltage of the second phase bridge arm is V2 = V ca Current I S23 =I Sa The voltage of the third phase bridge arm is V3 = V cc Current I S31 =I Sc .

[0170] In the example, for sub-region 2, V ca >V cc >V cb Therefore, AC side bridge arm a is the L-phase bridge arm, AC side bridge arm c is the M-phase bridge arm, and AC side bridge arm b is the S-phase bridge arm. The average current of the switching transistors in the M-phase bridge arm is positive, and the absolute value of the current in the S-phase bridge arm reaches its maximum and is negative. Therefore, the conduction sequence is SML, and the first, second, and third phase bridge arms are b, c, and a, respectively. Furthermore, the voltage V1 of the first phase bridge arm can be determined as V... cb Current I S12 =I SbThe voltage of the second phase bridge arm is V2 = V cc Current I S23 =I Sc The voltage of the third phase bridge arm is V3 = V ca Current I S31 =I Sa .

[0171] In the example, for sub-region 3, V ca >V cc >V cb Therefore, AC side bridge arm a is the L-phase bridge arm, AC side bridge arm c is the M-phase bridge arm, and AC side bridge arm b is the S-phase bridge arm. The average current of the switching transistors in the M-phase bridge arm is negative, while the absolute value of the current in the L-phase bridge arm reaches its maximum and is positive. Therefore, the conduction sequence is LMS, and the first, second, and third phase bridge arms are a, c, and b, respectively. Furthermore, the voltage V1 of the first phase bridge arm can be determined as V... ca Current I S12 =I Sa The voltage of the second phase bridge arm is V2 = V cc Current I S23 =I Sc The voltage of the third phase bridge arm is V3 = V cb Current I S31 =I Sb .

[0172] Figure 9 This is a schematic diagram illustrating the conduction sequence of the three-phase AC switching transistors in a power converter provided in an embodiment of this disclosure. (Refer to...) Figure 9 They can be determined separately. Figure 8 The mapping relationship between phases L, M, and S and phases a, b, and c in the 12 sub-regions numbered 1 to 12; based on whether the average current of the switch tubes in phase M is positive or negative, the phase corresponding to the largest absolute current, and whether the current in that phase is positive or negative, the conduction sequence of the switch tubes in phases L, M, and S is determined, and the first phase ([ ac1 , ac2 ] interval), second phase ([ ac2 , ac3 ] interval), third phase ([ ac3 , ac1 The mapping relationship between the bridge arm (+2π] interval) and the three phases a, b, and c.

[0173] It should be understood that the above is merely an example of the conduction sequence of the three-phase switching transistors on the AC side of the power converter. Those skilled in the art can determine the first, second, and third phase arms according to the actual situation of the circuit, and this disclosure does not impose any restrictions on this.

[0174] According to the control method of the power converter according to the embodiments of the present disclosure, a power model of the power converter under multiple modulation degrees of freedom can be established by fundamental wave analysis. By coordinating multiple control variables, not only can the precise regulation of the three-phase output current be achieved, but also the amplitude of the resonant current can be optimized by using redundant control degrees of freedom. At the same time, the soft switching of all switching transistors of the power converter can be guaranteed by constraint conditions, thereby reducing the switching loss on the AC side of the power converter and significantly improving the efficiency and soft switching performance of the power converter.

[0175] It is understood that the various method embodiments mentioned above in this disclosure can be combined with each other to form combined embodiments without violating the principle and logic. Due to space limitations, this disclosure will not elaborate further. Those skilled in the art will understand that in the above methods of specific implementation, the specific execution order of each step should be determined by its function and possible internal logic.

[0176] In addition, this disclosure also provides power converters and electronic devices, all of which can be used to implement the control method of any power converter provided in this disclosure. The corresponding technical solutions and descriptions are described in the corresponding descriptions in the method section and will not be repeated here.

[0177] According to embodiments of this disclosure, a power converter is also provided, with reference to... Figure 1 The power converter includes an input-side circuit 11, an output-side circuit 12, a resonant circuit, and a controller (not shown). The input-side circuit is connected to a DC voltage terminal, and the output-side circuit is connected to a three-phase AC terminal. The resonant circuit is connected between the input-side circuit and the output-side circuit.

[0178] The controller is connected to the input-side circuit and the output-side circuit and is configured to execute the control method of the power converter described above.

[0179] In some possible implementations, the controller is configured to: determine the average current value of the three AC-side bridge arms of the output-side circuit during a switching cycle based on the set current value of the three-phase AC terminals; determine the switching phase shift angle of the power converter's switching transistors during a switching cycle and the target operating frequency of the power converter based on the average current value, the DC sampling voltage value of the DC voltage terminal, and the AC voltage sampling value of the three-phase AC terminals; and generate a drive signal based on the switching phase shift angle and the target operating frequency, the drive signal being used to drive the switching transistors in the power converter.

[0180] In some possible implementations, the controller is specifically configured to: determine, according to the fundamental model, a first relationship between the first fundamental component of the primary voltage of the input circuit and the DC sampled voltage value, and a second relationship between the second fundamental component of the secondary voltage of the output circuit and the AC voltage sampled value; and determine the switching phase shift angle and the target operating frequency according to the average current value, the first relationship, and the second relationship.

[0181] In some possible implementations, the controller is specifically configured to: determine the minimum amplitude of the resonant current of the resonant circuit and the operating mode corresponding to the minimum amplitude based on the average current value, the DC sampling voltage value, the AC voltage sampling value, and the transformer turns ratio of the resonant circuit; determine the switching phase shift angle and the target operating frequency based on the phase shift angle constraint corresponding to the operating mode, the average current value, the first fundamental component of the primary voltage of the input circuit and the first relationship with the DC sampling voltage value, and the second fundamental component of the secondary voltage of the output circuit and the second relationship with the AC voltage sampling value; wherein, the drive signal generated based on the switching phase shift angle and the target operating frequency minimizes the amplitude of the resonant current of the power converter when transmitting a preset power.

[0182] In some possible implementations, the input-side circuit includes a first switch group and a second switch group, and the output-side circuit includes a third switch group of the first phase bridge arm, a fourth switch group of the second phase bridge arm, and a fifth switch group of the third phase bridge arm. The switches in the first switch group are complementary in conduction, and the switches in the second switch group are complementary in conduction. The first phase shift angle for the switching of the first switch group is 0. The phase shift angle includes the second phase shift angle for the switching of the second switch group and the fundamental equivalent phase shift angle, the third phase shift angle at which the switches in the third switch group begin to conduct simultaneously, and the fourth phase shift angle at which the switches in the third switch group end to conduct simultaneously and the switches in the fourth switch group begin to conduct simultaneously. The phase shift angle is the fifth phase shift angle at which the switching transistors of the fourth switching group simultaneously turn on and the switching transistors of the fifth switching group simultaneously turn on; the operating mode includes a first operating mode, and the first phase shift angle restriction condition corresponding to the first operating mode includes: the sum of the second phase shift angle and the fundamental equivalent phase shift angle is 0; the operating mode also includes a second operating mode, and the second phase shift angle restriction condition corresponding to the second operating mode includes: when the phase current with the largest absolute value of current in the average current value is positive, the third phase shift angle is 0 and the fourth phase shift angle is π; when the phase current with the largest absolute value of current in the average current value is negative, the third phase shift angle is π and the fourth phase shift angle is 2π.

[0183] In some possible implementations, the controller is specifically configured to: determine a first minimum value of the resonant current amplitude based on the first phase shift angle constraint, the average current value, the DC sampling voltage value, the AC voltage sampling value, and the transformer turns ratio of the resonant circuit; determine a second minimum value of the resonant current amplitude based on the absolute value of the phase current with the largest absolute current value in the average current value; determine the operating mode as a first operating mode if the first minimum value is greater than or equal to the second minimum value; and determine the operating mode as a second operating mode if the first minimum value is less than the second minimum value.

[0184] In some possible implementations, when the operating mode is the first operating mode, the controller is specifically configured to: determine the third phase shift angle, the fourth phase shift angle, the fifth phase shift angle, and the target operating frequency based on the first phase shift angle constraint, the average current value, the first relationship, and the second relationship when the first modulation strategy is adopted in the first operating mode, wherein the first modulation strategy includes: the fourth phase shift angle = π + the third phase shift angle; or, the fourth phase shift angle = π - the third phase shift angle; wherein the drive signal generated based on the switching phase shift angle and the target operating frequency causes the switching transistor of the power converter to switch at zero voltage.

[0185] In some possible implementations, when the operating mode is the first operating mode, the controller is specifically configured to: when the first operating mode employs a second modulation strategy, determine the third phase shift angle, the fourth phase shift angle, the fifth phase shift angle, and the target operating frequency based on the first phase shift angle constraint, the average current value, the first relationship, and the second relationship, wherein the second modulation strategy includes: when the phase current with the largest absolute current value in the average current value is positive, the fourth phase shift angle is π; when the phase current with the largest absolute current value in the average current value is negative, the third phase shift angle is π; wherein the drive signal generated based on the switching phase shift angle and the target operating frequency causes the switching transistor of the power converter to switch at zero voltage.

[0186] In some possible implementations, when the operating mode is the second operating mode, the controller is specifically configured to: when the second operating mode employs a third modulation strategy, determine the second phase shift angle, the fundamental equivalent phase shift angle, the fifth phase shift angle, and the target operating frequency based on the second phase shift angle constraint, the average current value, the first relationship, and the second relationship, wherein the third modulation strategy includes: the sum of the second phase shift angle and the fundamental equivalent phase shift angle is less than or equal to 0; wherein the drive signal generated based on the switching phase shift angle and the target operating frequency causes the switching transistor of the power converter to switch at zero voltage.

[0187] An electronic device comprising the power converter described above is also provided according to embodiments of the present disclosure.

[0188] Those skilled in the art will understand that all or some of the steps, systems, and apparatuses disclosed above, and their functional modules / units, can be implemented as software, firmware, hardware, or suitable combinations thereof. In hardware implementations, the division between functional modules / units mentioned above does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed collaboratively by several physical components. Some or all physical components may be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit (ASIC). Such software can be distributed on a computer-readable storage medium, which may include computer storage media (or non-transitory media) and communication media (or transient media).

[0189] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in connection with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in connection with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of this disclosure as set forth by the appended claims.

Claims

1. A control method for a power converter, characterized in that, The power converter includes an input-side circuit, an output-side circuit, and a resonant circuit connected between the input-side circuit and the output-side circuit. The input-side circuit is connected to a DC voltage terminal, and the output-side circuit is connected to a three-phase AC terminal. The method includes: Based on the set current value of the three-phase AC terminals, determine the average current value of the three AC side bridge arms of the output side circuit during the switching cycle. Based on the average current value, the DC sampling voltage value at the DC voltage terminal, and the AC voltage sampling value at the three-phase AC terminal, the switching phase shift angle of the power converter's switching transistor during the switching cycle and the target operating frequency of the power converter are determined. A drive signal is generated based on the switch phase shift angle and the target operating frequency. The drive signal is used to drive the switching transistors in the power converter.

2. The method according to claim 1, characterized in that, The step of determining the switching phase shift angle of the power converter's switching transistors during the switching cycle and the target operating frequency of the power converter based on the average current value, the DC sampling voltage value at the DC voltage terminal, and the AC voltage sampling value at the three-phase AC terminals includes: Based on the fundamental wave model, the first fundamental wave component of the primary side voltage of the input side circuit and the first relationship between the DC sampling voltage value are determined, and the second fundamental wave component of the secondary side voltage of the output side circuit and the second relationship between the AC voltage sampling value are determined. Based on the average current value, the first relationship, and the second relationship, the switch phase shift angle and the target operating frequency are determined.

3. The method according to claim 1, characterized in that, The step of determining the switching phase shift angle of the power converter's switching transistors during the switching cycle and the target operating frequency of the power converter based on the average current value, the DC sampling voltage value at the DC voltage terminal, and the AC voltage sampling value at the three-phase AC terminals includes: Based on the average current value, the DC sampling voltage value, the AC voltage sampling value, and the transformer turns ratio of the resonant circuit, determine the minimum amplitude of the resonant current of the resonant circuit and the operating mode corresponding to the minimum amplitude. Based on the phase shift angle constraint corresponding to the operating mode, the average current value, the first fundamental component of the primary voltage of the input circuit and the first relationship between the DC sampling voltage value, and the second fundamental component of the secondary voltage of the output circuit and the second relationship between the AC voltage sampling value, the switch phase shift angle and the target operating frequency are determined. The driving signal generated based on the switch phase shift angle and the target operating frequency minimizes the amplitude of the resonant current when the power converter transmits a preset power.

4. The method according to claim 3, characterized in that, The input-side circuit includes a first switching transistor group and a second switching transistor group. The output-side circuit includes a third switching transistor group of the first phase bridge arm, a fourth switching transistor group of the second phase bridge arm, and a fifth switching transistor group of the third phase bridge arm. The switching transistors in the first switching transistor group are complementary in conduction, and the switching transistors in the second switching transistor group are complementary in conduction. The first phase shift angle of the switching of the first switching transistor group is 0. The switching phase shift angle includes the second phase shift angle and the fundamental equivalent phase shift angle of the second switching transistor group switching, the third phase shift angle at which the switching transistors of the third switching transistor group start to conduct simultaneously, the fourth phase shift angle at which the switching transistors of the third switching transistor group end to conduct simultaneously and the switching transistors of the fourth switching transistor group start to conduct simultaneously, and the fifth phase shift angle at which the switching transistors of the fourth switching transistor group end to conduct simultaneously and the switching transistors of the fifth switching transistor group start to conduct simultaneously. The operating mode includes a first operating mode, and the first phase shift angle constraint corresponding to the first operating mode includes: the sum of the second phase shift angle and the fundamental equivalent phase shift angle is 0; The operating mode also includes a second operating mode, and the second phase shift angle limiting conditions corresponding to the second operating mode include: when the phase current with the largest absolute value of the current in the average current value is positive, the third phase shift angle is 0 and the fourth phase shift angle is π; when the phase current with the largest absolute value of the current in the average current value is negative, the third phase shift angle is π and the fourth phase shift angle is 2π.

5. The method according to claim 4, characterized in that, The step of determining the minimum amplitude of the resonant current of the resonant circuit and the corresponding operating mode based on the average current value, the DC sampling voltage value, and the transformer turns ratio of the resonant circuit includes: Based on the first phase shift angle constraint, the average current value, the DC sampling voltage value, the AC voltage sampling value, and the transformer turns ratio of the resonant circuit, determine the first minimum value of the resonant current amplitude; The second minimum value of the resonant current amplitude is determined based on the absolute value of the phase current with the largest absolute value among the average current values. If the first minimum value is greater than or equal to the second minimum value, the working mode is determined to be the first working mode; If the first minimum value is less than the second minimum value, the working mode is determined to be the second working mode.

6. The method according to claim 4, characterized in that, When the operating mode is the first operating mode, determining the switch phase shift angle and the target operating frequency includes: When the first modulation strategy is adopted in the first operating mode, the third phase shift angle, the fourth phase shift angle, the fifth phase shift angle, and the target operating frequency are determined based on the first phase shift angle constraint, the average current value, the first relationship, and the second relationship. The first modulation strategy includes: the fourth phase shift angle = π + the third phase shift angle; or, the fourth phase shift angle = π - the third phase shift angle; The driving signal generated based on the switching phase shift angle and the target operating frequency enables the power converter's switching transistors to switch at zero voltage.

7. The method according to claim 4, characterized in that, When the operating mode is the first operating mode, determining the switch phase shift angle and the target operating frequency includes: When the second modulation strategy is adopted in the first operating mode, the third phase shift angle, the fourth phase shift angle, the fifth phase shift angle, and the target operating frequency are determined based on the first phase shift angle constraint, the average current value, the first relationship, and the second relationship. The second modulation strategy includes: when the phase current with the largest absolute value of the current in the average current values ​​is positive, the fourth phase shift angle is π; when the phase current with the largest absolute value of the current in the average current values ​​is negative, the third phase shift angle is π. The driving signal generated based on the switching phase shift angle and the target operating frequency enables the power converter's switching transistors to switch at zero voltage.

8. The method according to claim 4, characterized in that, When the operating mode is the second operating mode, determining the switch phase shift angle and the target operating frequency includes: When the third modulation strategy is adopted in the second operating mode, the second phase shift angle, the fundamental equivalent phase shift angle, the fifth phase shift angle, and the target operating frequency are determined based on the second phase shift angle constraint, the average current value, the first relationship, and the second relationship. The third modulation strategy includes: the sum of the second phase shift angle and the fundamental equivalent phase shift angle is less than or equal to 0; The driving signal generated based on the switching phase shift angle and the target operating frequency enables the power converter's switching transistors to switch at zero voltage.

9. A power converter, characterized in that, Includes input-side circuitry, output-side circuitry, resonant circuitry, and a controller. The input-side circuit is connected to the DC voltage terminal, and the output-side circuit is connected to the three-phase AC terminal; The resonant circuit is connected between the input-side circuit and the output-side circuit; The controller is connected to the input-side circuit and the output-side circuit, and is configured to perform the control method of the power converter according to any one of claims 1-8.

10. An electronic device, characterized in that, Includes the power converter according to claim 9.

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