Resonant converter

Abstract

The present disclosure relates to a resonant converter. The resonant converter comprises a direct-current side bridge arm circuit, a transformer, an alternating-current side half-bridge circuit, a filter capacitor, and a controller; the alternating-current side half-bridge circuit comprises an upper bridge arm circuit, a lower bridge arm circuit, and a resonant capacitor; the transformer has one end connected to the direct-current side bridge arm circuit and the other end connected to the alternating-current side half-bridge circuit; the filter capacitor is connected in parallel to an output end of the alternating-current side half-bridge circuit, and the capacitance value of the filter capacitor is greater than that of the resonant capacitor; and the controller is used for acquiring the current polarity of an alternating-current side grid voltage in response to a wave blocking signal corresponding to the resonant converter, and controlling the alternating-current side half-bridge circuit to operate according to a target freewheeling path corresponding to the current polarity, so as to transfer leakage inductance energy to the filter capacitor. By using the resonant converter, the problem of voltage stress in the alternating-current side half-bridge circuit during wave blocking can be solved, avoiding damage to an alternating-current side switching device.

Description

Resonant converter

[0001] Related applications

[0002] The present disclosure claims priority to the Chinese patent application No. 2024104743878, filed on April 19, 2024, entitled "Converter Clamper Control Method, Converter and Chip", the contents of which are incorporated herein by reference in their entirety; the present application claims priority to the PCT international application No. PCT / CN2024 / 106759, filed on July 22, 2024, entitled "Converter Clamper Control Method, Converter and Chip", the contents of which are incorporated herein by reference in their entirety. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of converter control, in particular to a resonant converter. BACKGROUND

[0004] When clamping the converter using a half-bridge circuit on the AC side, if all the switching tubes on the AC side are directly turned off, the energy stored in the transformer leakage inductance has no discharge path, which can easily lead to overvoltage stress of the half-bridge circuit on the AC side connected to the power grid, resulting in damage to the switching devices on the AC side.

[0005] Therefore, there is an urgent need for a converter clamping control method to solve the voltage stress problem of the half-bridge circuit on the AC side during clamping and to avoid damage to the switching devices on the AC side. SUMMARY

[0006] Therefore, it is necessary to provide a resonant converter capable of solving the voltage stress risk of the half-bridge circuit on the AC side during clamping.

[0007] In a first aspect, the present disclosure provides a resonant converter, wherein the resonant converter comprises a DC side bridge arm circuit, a transformer, an AC side half-bridge circuit, a filter capacitor and a controller.

[0008] The AC side half-bridge circuit comprises an upper bridge arm circuit, a lower bridge arm circuit and a resonant capacitor.

[0009] One end of the transformer is connected to the DC side bridge arm circuit, and the other end of the transformer is connected to the AC side half-bridge circuit.

[0010] The filter capacitor is connected in parallel to the output end of the AC side half-bridge circuit, and the capacitance of the filter capacitor is greater than that of the resonant capacitor.

[0011] The controller is configured to obtain a current polarity of an AC side grid voltage in response to a clamping signal corresponding to the resonant converter, and control the AC side half-bridge circuit to work according to a target freewheeling path corresponding to the current polarity, so as to transfer the leakage energy to the filter capacitor.

[0012] In one of the embodiments, a ratio between a capacitance value of the filter capacitor and a capacitance value of the resonance capacitor is greater than 10.

[0013] In one of the embodiments, the upper bridge arm circuit of the AC side half-bridge circuit comprises a first switch device and a second switch device, and the lower bridge arm circuit of the AC side half-bridge circuit comprises a third switch device and a fourth switch device, and the second switch device and the third switch device are connected with the bridge arm midpoint of the AC side half-bridge circuit respectively.

[0014] In one of the embodiments, the resonance converter further comprises a filter impedance; and the filter impedance and the filter capacitor form a filter circuit.

[0015] In one of the embodiments, the controller is configured to obtain a current polarity of the AC side grid voltage in response to the corresponding clamp signal of the converter, and control the AC side half-bridge circuit to work in a target freewheeling path corresponding to the current polarity, comprising:

[0016] The controller is configured to control the first switch device group to be turned on and the second switch device group to be turned off when the current polarity is positive, and control the second switch device group to be turned on and the first switch device group to be turned off when the current polarity is negative.

[0017] In one of the embodiments, the first switch device group comprises two switch devices in the AC side half-bridge circuit, and the second switch device group comprises the other two switch devices in the AC side half-bridge circuit.

[0018] In one of the embodiments, the controller is configured to obtain a current polarity of the AC side grid voltage in response to the corresponding clamp signal of the converter, and control the AC side half-bridge circuit to work in a target freewheeling path corresponding to the current polarity, comprising: the controller is configured to control the second switch device and the fourth switch device to be turned on and the first switch device and the third switch device to be turned off when the current polarity is positive, and control the first switch device and the third switch device to be turned on and the second switch device and the fourth switch device to be turned off when the current polarity is negative.

[0019] In one of the embodiments, the controller is configured to obtain a current polarity of the AC side grid voltage in response to the corresponding clamp signal of the resonance converter, comprising: the controller is configured to obtain a current phase of the AC side grid voltage; and determine the current polarity according to the current phase.

[0020] In one of the embodiments, the controller is configured to obtain a current polarity of the AC side grid voltage in response to the corresponding clamp signal of the resonance converter, comprising: the controller is further configured to obtain a current instantaneous voltage of the AC side grid voltage; and determine the current polarity according to the instantaneous voltage.

[0021] In one of the embodiments, the controller is further configured to control all the switching devices of the AC side half-bridge circuit to be turned off after controlling the AC side half-bridge circuit to work according to the target freewheeling path for a preset time length.

[0022] In one of the embodiments, the preset time length ranges from 1 microsecond to 100 milliseconds.

[0023] In one of the embodiments, the target freewheeling path includes a positive freewheeling path and a negative freewheeling path, and the controller is further configured to, after controlling the AC side half-bridge circuit to work according to the target freewheeling path corresponding to the current polarity, control the target freewheeling path to switch from the positive freewheeling path to the negative freewheeling path or vice versa when detecting that the polarity of the AC side power grid changes.

[0024] The resonant converter includes a DC side bridge arm circuit, a transformer, an AC side half-bridge circuit, a filter capacitor, and a controller. The AC side half-bridge circuit includes an upper bridge arm circuit, a lower bridge arm circuit, and a resonant capacitor. One end of the transformer is connected to the DC side bridge arm circuit, and the other end of the transformer is connected to the AC side half-bridge circuit. The filter capacitor is connected in parallel to the output end of the AC side half-bridge circuit, and the capacitance of the filter capacitor is greater than that of the resonant capacitor. The controller is configured to, in response to a corresponding clamp signal of the resonant converter, acquire a current polarity of an AC side grid voltage, and control the AC side half-bridge circuit to work according to a target freewheeling path corresponding to the current polarity, so as to transfer the leakage energy to the filter capacitor. In this way, the leakage energy is stored in the filter capacitor with a larger capacitance, which can realize fast transfer of the leakage energy, reduce the voltage stress risk of the AC side switching device in the clamping process, and improve the reliability of the converter operation. Meanwhile, the current polarity of the AC side grid voltage is considered when selecting the target freewheeling path, which avoids causing short circuit of the AC side grid and ensures the safety of the clamping control of the converter. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only embodiments of the present disclosure, and other drawings can also be obtained by those skilled in the art without any creative effort based on the disclosed drawings.

[0026] FIG. 1 is a circuit topology structure of a single-stage isolated grid-connected inverter in one of the embodiments;

[0027] FIG. 2 is a circuit topology structure of a single-stage isolated grid-connected inverter in another of the embodiments;

[0028] FIG. 3 is a control timing diagram of the switching devices in the AC side half-bridge circuit when the current polarity is positive in one of the embodiments;

[0029] FIG. 4 is a control timing diagram of the switching devices in the AC side half-bridge circuit when the current polarity is negative in one embodiment;

[0030] FIG. 5 is a current flow diagram of the target freewheeling path when the current polarity is positive in one embodiment;

[0031] FIG. 6 is another current flow diagram of the target freewheeling path when the current polarity is positive in one embodiment;

[0032] FIG. 7 is a current flow diagram of the target freewheeling path when the current polarity is negative in one embodiment;

[0033] FIG. 8 is another current flow diagram of the target freewheeling path when the current polarity is negative in one embodiment;

[0034] FIG. 9 is a control timing diagram of the switching devices in the AC side half-bridge circuit when the current polarity is positive in another embodiment;

[0035] FIG. 10 is a control timing diagram of the switching devices in the AC side half-bridge circuit when the current polarity is negative in another embodiment;

[0036] FIG. 11 is a flowchart of the operation of the converter clamp control method in one embodiment. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present disclosure will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present disclosure.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure.

[0039] It can be understood that the terms "first", "second", etc. used in the present disclosure can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present disclosure, the first resistor can be referred to as the second resistor, and similarly, the second resistor can be referred to as the first resistor. The first resistor and the second resistor are both resistors, but they are not the same resistor.

[0040] It can be understood that "connection" in the following embodiments should be understood as "electrical connection", "communication connection" and the like if the circuits, modules, units and the like connected with each other have transmission of electrical signals or data.

[0041] It can be understood that the term "based on" used in the present disclosure is used to describe one or more factors that affect the determination, and does not exclude other factors that can affect the determination. For example, the phrase "determining A based on B" means that the determination of A can be based entirely or at least partially on factor B, that is, B is one factor affecting the determination of A, but does not exclude that the determination of A is also based on C.

[0042] As used herein, the singular forms "a", "an" and "the" also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprise / contain" or "have" or the like specify the presence of stated features, integers, steps, operations, components, parts or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, components, parts or combinations thereof. Meanwhile, the term "and / or" used in the specification includes any and all combinations of the related listed items.

[0043] The transformer envelope control method provided by the embodiments of the present disclosure can be used in a controller of a resonant converter with a half-bridge circuit structure on the AC side, wherein the upper bridge arm and the lower bridge arm of the half-bridge circuit are both realized by a bidirectional switch, and the controller is connected with at least each switching device in the resonant converter to control the on-off frequency, duty cycle and phase shift of each switching device. The resonant converter can be a DC-AC converter, such as a single-stage isolated grid-connected inverter, or an AC-DC converter, such as a single-stage isolated rectifier.

[0044] Please refer to FIG. 1 and FIG. 2, which are a circuit topology structure of a single-stage isolated grid-connected inverter. Among them, V dc represents the DC side power supply voltage, V ac is the AC side grid voltage; the AC side half-bridge circuit includes an upper bridge arm circuit, a lower bridge arm circuit, a resonant capacitor C p and a resonant capacitor C n , wherein the upper bridge arm circuit is realized based on a bidirectional switch composed of a switching device Q5 and a switching device Q6, the lower bridge arm circuit is realized based on a bidirectional switch composed of a switching device Q7 and a switching device Q8, and the bridge arm midpoint C is connected with the leakage inductance L r of the converter. p Correspondingly, the lower bridge arm circuit is connected with the resonant capacitor C n Correspondingly, the capacitor C p and the capacitor C n are connected in series, and the resonant capacitor Cp and resonant capacitor C n The intermediate connection point D is connected to the transformer in the converter; the filter capacitor C o The filter capacitor C is connected in parallel to the output end of the AC side half-bridge circuit. o and filter impedance Z g to form a filter circuit; wherein, for example, the filter impedance Zg includes an EMI (Electromagnetic Interference) filter impedance and a grid impedance. In the technical field, if the converter is an inverter, the AC side is the output end, and the filter capacitor C o may also be referred to as an output capacitor.

[0045] Wherein, the controller is not shown in FIG. 1 and FIG. 2, the controller can be implemented by an MCU (Microcontroller Unit) chip; it can also be implemented based on a DSP (Digital Signal Processor) chip, an FPGA (Field-Programmable Gate Array) or a self-customized controller chip; the specific implementation hardware of the controller is not limited in the embodiments of the present disclosure.

[0046] Please refer to FIG. 2, for example, the DC side of the resonant converter to which the converter envelope control method provided by the embodiments of the present disclosure is applied can be implemented by an H-bridge circuit, wherein the first bridge arm circuit of the DC side H-bridge circuit includes a switching device Q1 and a switching device Q2, and the second bridge arm circuit includes a switching device Q3 and a switching device Q4, wherein the A point and the B point are the load interface of the DC side H-bridge circuit, T r is a transformer.

[0047] It should be noted that the embodiments of the present disclosure do not limit the specific circuit structure adopted by the DC side, and FIG. 2 is only an example.

[0048] Wherein, the switching device involved in the embodiments of the present disclosure can also be referred to as a power switch tube; for example, the switching device can be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), or an IGBT (Insulated Gate Bipolar Transistor), and the specific type and model of the switching device are not limited in the present disclosure.

[0049] In one example embodiment, the resonant converter comprises an AC side half-bridge circuit, a filter capacitor connected in parallel to the output of the AC side half-bridge circuit, and a controller, the converter clamp control method provided by the embodiment is used in the controller of the resonant converter, and the method comprises: obtaining the current polarity of the AC side grid voltage in response to the corresponding clamp signal of the resonant converter, and controlling the AC side half-bridge circuit to work according to the target freewheeling path corresponding to the current polarity, so as to transfer the leakage energy to the filter capacitor.

[0050] Wherein, the clamp signal can be based on the external input shutdown instruction, or the controller can generate the clamp signal by itself when the running condition of the resonant converter meets the preset shutdown condition, so as to close the resonant converter. Please refer to FIG. 3 and FIG. 4, time t p1 represents the time when the controller starts to respond to the clamp signal to perform clamp control after receiving the clamp signal when the grid voltage is in the positive half cycle, time t n1 represents the time when the controller starts to respond to the clamp signal to perform clamp control after receiving the clamp signal when the grid voltage is in the negative half cycle.

[0051] Wherein, the target freewheeling path refers to the freewheeling path that can transfer the leakage energy to the filter capacitor; the target freewheeling path is constructed according to the current polarity of the AC side grid voltage, so that the leakage energy can be quickly transferred to the filter capacitor, and at the same time, the short circuit of the AC side grid can be avoided.

[0052] In one possible implementation, the process of obtaining the current polarity of the AC side grid voltage comprises: obtaining the current phase of the AC side grid voltage, and determining the current polarity according to the current phase.

[0053] Wherein, the phase corresponding to the positive polarity is 0° to 180°, and the phase corresponding to the negative polarity is 180° to 360°, wherein at the interval boundary phase of 0°, 180° or 360°, that is, the zero-crossing phase of the AC side grid voltage, it can be confirmed as positive polarity or negative polarity.

[0054] In one possible implementation, the process of obtaining the current polarity of the AC side grid voltage comprises: obtaining the current instantaneous voltage of the AC side grid voltage, and determining the current polarity according to the instantaneous voltage.

[0055] Wherein, when the instantaneous voltage is positive, the current polarity is positive, and when the instantaneous voltage is negative, the current polarity is negative. When the current instantaneous voltage is 0, it can be determined as positive polarity or negative polarity.

[0056] The filter capacitor generally uses a capacitor with a large capacitance, about 100 nF (nanofarad) or uF (microfarad), and the resonance capacitor generally uses a capacitor with a small capacitance, about 10 nF. The target freewheeling path in the embodiment is configured to transfer the leakage energy to the filter capacitor. Compared with the related art, the leakage energy is transferred to the filter capacitor, and the filter capacitor has a large capacitance, so that the leakage energy can be quickly absorbed, and the voltage stress risk of the AC side switching device during the clamping process is reduced.

[0057] The converter control method provided in the embodiment responds to the clamping signal corresponding to the resonant converter, obtains the current polarity of the AC side grid voltage, controls the AC side half-bridge circuit to work according to the target freewheeling path corresponding to the current polarity, and transfers the leakage energy to the filter capacitor. In this way, the leakage energy is stored in the filter capacitor with a large capacitance, the size and direction of the leakage inductance current do not need to be detected, the leakage energy can be quickly transferred, the voltage stress risk of the AC side switching device during the clamping process is reduced, and the reliability of the resonant converter is improved. At the same time, the current polarity of the AC side grid voltage is considered when the target freewheeling path is selected, so as to avoid causing the short circuit of the AC side grid and ensure the safety of the clamping control of the resonant converter.

[0058] In one exemplary embodiment, controlling the AC side half-bridge circuit to work according to the target freewheeling path corresponding to the current polarity includes: when the current polarity is positive, controlling the first switching device group to be turned on and the second switching device group to be turned off; and when the current polarity is negative, controlling the second switching device group to be turned on and the first switching device group to be turned off.

[0059] The first switching device group includes two switching devices in the AC side half-bridge circuit, and the second switching device group includes the other two switching devices in the AC side half-bridge circuit.

[0060] In one possible implementation of the embodiment, the upper bridge arm circuit of the AC side half-bridge circuit includes a first switching device and a second switching device, the lower bridge arm circuit of the AC side half-bridge circuit includes a third switching device and a fourth switching device, and the second switching device and the third switching device are respectively connected to the bridge arm midpoint of the AC side half-bridge circuit. In combination with the circuit topologies in FIGS. 1 and 2, the first switching device in the embodiment is the switching device Q5 in FIGS. 1 and 2, the second switching device is the switching device Q6 in FIGS. 1 and 2, the third switching device is the switching device Q7 in FIGS. 1 and 2, and the fourth switching device is the switching device Q8 in FIGS. 1 and 2.

[0061] In the embodiment, the first switch device group includes the second switch device and the fourth switch device, and the third switch device includes the first switch device and the fourth switch device. The control of the AC side half-bridge circuit working according to the target freewheeling path corresponding to the current polarity includes: when the current polarity is positive, controlling the second switch device and the fourth switch device to be turned on, and simultaneously controlling the first switch device and the third switch device to be turned off; and when the current polarity is negative, controlling the first switch device and the third switch device to be turned on, and simultaneously controlling the second switch device and the fourth switch device to be turned off.

[0062] Please refer to FIG. 3, FIG. 5 and FIG. 6, wherein FIG. 3 is a control timing diagram of the switch devices of the AC side half-bridge circuit when the current polarity is positive, and FIG. 5 and FIG. 6 are current flow direction diagrams of the leakage energy transferring according to the target freewheeling path when the current polarity is positive. As shown in FIG. 3, before time t p1 , the AC side grid voltage is in the positive half cycle, and no matter whether the control mode of the AC side half-bridge circuit is the first mode, i.e., the switch device Q6 and the switch device Q8 are always turned on, and the switch device Q5 and the switch device Q7 are high-frequency complementary turned on, or the control mode of the AC side half-bridge circuit is the second mode (not limited in the disclosure), at time t p1 , the switch device Q5 and the switch device Q7 are controlled to be turned off, and the switch device Q6 and the switch device Q8 are turned on.

[0063] Please refer to FIG. 5, at time t p1 , the current direction at the leakage inductance L r is from the leakage inductance L r to point C, at this time, the leakage energy is transferred to the resonant capacitor C p and the filter capacitor C o through the anti-parallel diode in the turned-on switch device Q6 and the turned-off switch device Q5 according to the target freewheeling path; because the capacitance of the filter capacitor C o is large, the leakage energy can be quickly absorbed, so that the AC side half-bridge circuit is safely clamped.

[0064] Please refer to FIG. 6, at time t p1 , the current direction at the leakage inductance L r is from point C to the leakage inductance L r , at this time, the leakage energy is transferred to the resonant capacitor C n and the filter capacitor C o through the anti-parallel diode in the turned-on switch device Q8 and the turned-off switch device Q7 according to the target freewheeling path; because the capacitance of the filter capacitor C o is large, the leakage energy can be quickly absorbed, so that the AC side half-bridge circuit is safely clamped.

[0065] Please refer to Fig. 4, Fig. 7 and Fig. 8, wherein Fig. 4 is a control timing diagram of the switching devices of the AC side half-bridge circuit when the current polarity is negative, Fig. 7 and Fig. 8 are current flow direction diagrams of the leakage energy transferred according to the target freewheeling path when the current polarity is negative. As shown in Fig. 4, before time t n1 , the AC side grid voltage is in the negative half cycle, at this time, no matter whether the control mode of the AC side half-bridge circuit is the first mode when the AC side half-bridge circuit is outside the zero-crossing interval, i.e. the switching device Q5 and the switching device Q7 are always on, the switching device Q6 and the switching device Q8 are high-frequency complementary conduction, or the control mode of the AC side half-bridge circuit is the second mode when the AC side half-bridge circuit is inside the zero-crossing interval, at time t1, the switching device Q6 and the switching device Q8 are controlled to be turned off, and the switching device Q5 and the switching device Q7 are turned on.

[0066] Please refer to Fig. 7, at time t n1 , the current direction at the leakage inductance L r is from the leakage inductance L r to point C, at this time, through the target freewheeling path, the leakage energy is transferred to the resonant capacitor C n and the filter capacitor C o through the anti-parallel diode in the turned-on switching device Q7 and the turned-off switching device Q8; because the capacitance of the filter capacitor C o is large, the leakage energy can be quickly absorbed, so that the AC side half-bridge circuit is safely clamped.

[0067] Please refer to Fig. 8, at time t n1 , the current direction at the leakage inductance L r is from point C to the leakage inductance L r , at this time, through the target freewheeling path, the leakage energy is transferred to the resonant capacitor C p and the filter capacitor C o through the anti-parallel diode in the turned-on switching device Q5 and the turned-off switching device Q6; because the capacitance of the filter capacitor C o is large, the leakage energy can be quickly absorbed, so that the AC side half-bridge circuit is safely clamped.

[0068] As can be seen from Fig. 5 and Fig. 6, in the case that the AC side grid voltage is positive, no matter whether the current direction at the leakage inductance L r is from the leakage inductance L r to point C or from point C to the leakage inductance L r , the target freewheeling path provided in the embodiment can make the filter capacitor C o be continuously charged in the first direction; similarly, as can be seen from Fig. 7 and Fig. 8, in the case that the AC side grid voltage is negative, no matter whether the current direction at the leakage inductance L r is from the leakage inductance L r to point C or from point C to the leakage inductance L r, the target freewheeling path provided by this embodiment can continuously flow to the filter capacitor C along the second direction o Thus, the converter provided by this embodiment of the invention provides a method for controlling the wave envelope, which can continuously charge the filter capacitor C in one direction. o Charging can quickly transfer the leakage inductance energy to the filter capacitor for storage, reduce the voltage stress risk of the AC side switching device during the blocking wave, and improve the reliability of the resonant converter. At the same time, the converter blocking wave control method provided in this embodiment does not need to judge the leakage inductance L at the blocking wave moment. r The current direction at the point avoids the related art based on the leakage inductance L r When the freewheeling path is selected for the current direction at the current source, there may be a risk of voltage stress on the AC side switching device due to misjudgment of the current direction.

[0069] Furthermore, even if the polarity of the AC side grid voltage is not accurately determined near the zero crossing point, since the AC side voltage value near the zero crossing point is small and the leakage inductance energy is small, a short period of shoot-through generally does not cause stress risk to the switching device. At the same time, the target freewheeling path provided in this embodiment can still ensure that the leakage inductance energy is within the leakage inductance L. r and resonant capacitor C p Or resonant capacitor C n Bidirectional flow between them further avoids the risk of device stress.

[0070] In an exemplary embodiment, after detecting the leakage inductance L r When the current value at is less than a preset threshold, all switching devices of the AC side half-bridge circuit are controlled to be turned off.

[0071] In an exemplary embodiment, a preset duration of freewheeling operation according to a target freewheeling path is pre-configured; after the AC side half-bridge circuit is controlled to operate according to the target freewheeling path for the preset duration, all switching devices of the AC side half-bridge circuit are controlled to be turned off. For example, please refer to FIG3 and FIG4. At time tp2 or time t n2 All switching devices of the AC side half-bridge circuit are controlled to be turned off. ΔT in FIG3 and FIG4 is a preset time length.

[0072] In one possible embodiment, the provided converter wave blocking control method also includes: obtaining the current power value corresponding to the AC side half-bridge circuit in response to the wave blocking signal corresponding to the resonant converter; and obtaining a preset duration based on the current power value and the capacitance of the filter capacitor.

[0073] In this embodiment, the preset duration is obtained based on the current operating rate value corresponding to the AC side half-bridge circuit and the capacitance of the filter capacitor when the wave-blocking signal is received, thereby improving the accuracy of the freewheeling working duration of the wave-blocking process.

[0074] In another possible implementation, the preset time length for the target freewheeling path is an empirical value configured in advance according to a large number of experiments.

[0075] The applicant finds through circuit principle analysis and a large number of experiments that the value range of the preset time length for the target freewheeling path can be set to 1 μs to 100 ms, which can achieve fast clamping while solving the voltage stress problem of the AC side half-bridge circuit at the time of clamping, and avoid damage to the AC side switching device.

[0076] In the embodiment, the working time length of the freewheeling path is controlled according to the determined preset time length, which, compared with the way of determining the turn-off of all switching devices of the AC side half-bridge circuit by real-time collection of the current value at the leakage inductance L r , does not need to additionally set a current sampling circuit, saves hardware resources, and improves control efficiency.

[0077] In one exemplary embodiment, the target freewheeling path includes a positive freewheeling path and a negative freewheeling path. Please refer to FIG. 9 and FIG. 10, after the controller controls the AC side half-bridge circuit to work according to the target freewheeling path corresponding to the current polarity, the controller controls the target freewheeling path to switch from the positive freewheeling path to the negative freewheeling path, or controls the target freewheeling path to switch from the negative freewheeling path to the positive freewheeling path when detecting that the polarity of the AC side power grid changes.

[0078] For example, the positive freewheeling path includes that the second switching device and the fourth switching device are turned on, and the first switching device and the third switching device are turned off; the negative freewheeling path includes that the first switching device and the third switching device are turned on, and the second switching device and the fourth switching device are turned off; please refer to FIG. 9 and FIG. 10, the positive freewheeling path includes that the switching device Q6 and the switching device Q8 are turned on, and the switching device Q5 and the switching device Q7 are turned off; the negative freewheeling path includes that the switching device Q5 and the switching device Q7 are turned on, and the switching device Q6 and the switching device Q8 are turned off.

[0079] In one possible implementation, as shown in FIG. 9, the time t p1 represents the time responding to the clamping signal corresponding to the resonant converter; in the embodiment shown in FIG. 9, the clamping signal is received when the grid voltage is in the positive half cycle, at this time, the current polarity is positive, the target freewheeling path corresponding to the current polarity is the positive freewheeling path, the switching device Q6 and the switching device Q8 are turned on, and the switching device Q5 and the switching device Q7 are turned off; at the first zero-crossing time t p1 after the time t z1 , the target freewheeling path is switched from the positive freewheeling path to the negative freewheeling path, that is, the switching device Q5 and the switching device Q7 are turned on, and the switching device Q6 and the switching device Q8 are turned off; at the zero-crossing time t z1the next zero-crossing time t z2 The target freewheeling path is switched from the negative freewheeling path to the positive freewheeling path, and the target freewheeling path is switched according to the polarity change of the grid voltage.

[0080] In one possible implementation, as shown in FIG. 10, the time t n1 The time t represents the time when the resonant converter receives the blocking signal; in the implementation shown in FIG. 10, the blocking signal is received when the grid voltage is in the negative half cycle, at this time, the current polarity is negative, the target freewheeling path corresponding to the current polarity is the negative freewheeling path, the switching devices Q5 and Q7 are turned on, and the switching devices Q6 and Q8 are turned off, and at the time t n1 the first zero-crossing time t z1 The target freewheeling path is switched from the negative freewheeling path to the positive freewheeling path, the switching devices Q6 and Q8 are turned on, and the switching devices Q5 and Q7 are turned off, at the zero-crossing time t z1 the next zero-crossing time t z2 The target freewheeling path is switched from the positive freewheeling path to the negative freewheeling path, and the target freewheeling path is switched according to the polarity change of the grid voltage.

[0081] In the converter control method provided by the above embodiment, after the blocking signal is received, no preset time length for freewheeling is set, the target freewheeling path follows the polarity change of the grid voltage, the short circuit of the AC side grid voltage after the polarity change of the AC side grid voltage is avoided, and the safety and reliability of the grid operation are ensured.

[0082] In the scenario where the time when the blocking signal is received is close to the zero-crossing time of the grid voltage, when the polarity of the grid voltage changes, there may be a situation that the leakage energy has not been completely transferred to the filter capacitor, and the converter control method provided by the above embodiment is adopted, the target freewheeling path follows the polarity change of the AC side grid voltage, and the safety of the grid operation in the freewheeling process is improved.

[0083] In one exemplary embodiment, the resonant converter includes an AC side half-bridge circuit, a filter capacitor, and a controller, the filter capacitor is connected in parallel to the output end of the AC side half-bridge circuit, the upper bridge arm circuit of the AC side half-bridge circuit includes a first switching device and a second switching device, the lower bridge arm circuit of the AC side half-bridge circuit includes a third switching device and a fourth switching device, and the second switching device and the third switching device are respectively connected to the bridge arm midpoint of the AC side half-bridge circuit; the converter blocking control method provided by the present embodiment is used in the controller, please refer to FIG. 11, and the method includes steps 1102 to 1108, wherein:

[0084] Step 1102, in response to the corresponding envelope signal of the transformer, the current polarity of the AC side grid voltage is obtained.

[0085] Optionally, the current phase of the AC side grid voltage is obtained, and the current polarity is determined according to the current phase.

[0086] Optionally, the current instantaneous voltage of the AC side grid voltage is obtained, and the current polarity is determined according to the instantaneous voltage.

[0087] Step 1104, it is judged whether the current polarity is positive or not.

[0088] Step 1106, if the current polarity is positive, the AC side half-bridge circuit is controlled to work according to the positive freewheeling path, so as to transfer the leakage energy to the filter capacitor; wherein, the positive freewheeling path includes that the first switch device and the third switch device are turned off, and the second switch device and the fourth switch device are turned on.

[0089] Optionally, after controlling the AC side half-bridge circuit to work according to the positive freewheeling path for a preset time length, the first switch device, the second switch device, the third switch device and the fourth switch device are turned off.

[0090] Optionally, after controlling the AC side half-bridge circuit to work according to the positive freewheeling path, when it is detected that the polarity of the AC side grid changes, the target freewheeling path is switched between the positive freewheeling path and the negative freewheeling path, so that the target freewheeling path matches the polarity of the grid voltage; wherein, the negative freewheeling path includes that the first switch device and the third switch device are turned on, and the second switch device and the fourth switch device are turned off.

[0091] Step 1108, if the current polarity is negative, the AC side half-bridge circuit is controlled to work according to the negative freewheeling path, so as to transfer the leakage energy to the filter capacitor.

[0092] Optionally, after controlling the AC side half-bridge circuit to work according to the negative freewheeling path for a preset time length, the first switch device, the second switch device, the third switch device and the fourth switch device are turned off.

[0093] Optionally, after controlling the AC side half-bridge circuit to work according to the negative freewheeling path, when it is detected that the polarity of the AC side grid changes, the target freewheeling path is switched between the negative freewheeling path and the positive freewheeling path, so that the target freewheeling path matches the polarity of the grid voltage.

[0094] It should be understood that although the steps in the flowcharts involved in the above embodiments are shown in sequence according to the arrows, the steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, the execution of the steps is not strictly limited in sequence, and the steps can be executed in other sequences or simultaneously. Moreover, at least some of the steps in the flowcharts involved in the above embodiments can include multiple steps or stages, which are not necessarily executed at the same time but can be executed at different times, and the execution sequence of the steps or stages is not necessarily sequential but can be executed alternately or alternately with at least some of the other steps or steps or stages in other steps.

[0095] The embodiments of the present disclosure also provide a resonant converter. The implementation scheme for solving the problem provided by the resonant converter is similar to the implementation scheme described in the above method, so the specific limitations in one or more resonant converter embodiments provided below can refer to the limitations of the converter control method in the above, which will not be repeated here. The resonant converter includes a DC side bridge arm circuit, a transformer, an AC side half-bridge circuit, a filter capacitor, and a controller; the AC side half-bridge circuit includes an upper bridge arm circuit, a lower bridge arm circuit, and a resonant capacitor; one end of the transformer is connected with the DC side bridge arm circuit, and the other end of the transformer is connected with the AC side half-bridge circuit; the filter capacitor is connected in parallel at the output end of the AC side half-bridge circuit, and the capacitance value of the filter capacitor is greater than that of the resonant capacitor; the controller is configured to obtain a current polarity of an AC side grid voltage in response to a corresponding clamping signal of the converter, and control the AC side half-bridge circuit to work according to a target freewheeling path corresponding to the current polarity, so as to transfer leakage energy to the filter capacitor.

[0096] In an exemplary embodiment, the ratio between the capacitance value of the filter capacitor and the capacitance value of the resonant capacitor is greater than 10.

[0097] In an exemplary embodiment, the upper bridge arm circuit of the AC side half-bridge circuit includes a first switching device and a second switching device, and the lower bridge arm circuit of the AC side half-bridge circuit includes a third switching device and a fourth switching device, and the second switching device and the third switching device are respectively connected with a bridge arm midpoint of the AC side half-bridge circuit.

[0098] In an exemplary embodiment, the resonant converter further includes a filter impedance; wherein the filter impedance and the filter capacitor form a filter circuit.

[0099] In one example embodiment, the controller is configured to obtain a current polarity of the AC side grid voltage in response to the corresponding clamp signal of the converter, and control the AC side half-bridge circuit to operate in a target freewheeling path corresponding to the current polarity, including: when the current polarity is positive, the controller is configured to control the first switch device group to be turned on and the second switch device group to be turned off; and when the current polarity is negative, the controller is configured to control the second switch device group to be turned on and the first switch device group to be turned off, wherein the first switch device group includes two switch devices in the AC side half-bridge circuit, and the second switch device group includes the other two switch devices in the AC side half-bridge circuit.

[0100] In one example embodiment, the controller is configured to obtain a current polarity of the AC side grid voltage in response to the corresponding clamp signal of the converter, and control the AC side half-bridge circuit to operate in a target freewheeling path corresponding to the current polarity, including: when the current polarity is positive, the controller is configured to control the second switch device and the fourth switch device to be turned on and the first switch device and the third switch device to be turned off; and when the current polarity is negative, the controller is configured to control the first switch device and the third switch device to be turned on and the second switch device and the fourth switch device to be turned off.

[0101] In one example embodiment, the controller is configured to obtain a current polarity of the AC side grid voltage in response to the corresponding clamp signal of the converter, including: the controller is configured to obtain a current phase of the AC side grid voltage; and determine the current polarity according to the current phase.

[0102] In one example embodiment, the controller is configured to obtain a current polarity of the AC side grid voltage in response to the corresponding clamp signal of the converter, including: the controller is configured to obtain a current phase of the AC side grid voltage; and determine the current polarity according to the current phase.

[0103] In one example embodiment, the controller is further configured to control all switch devices of the AC side half-bridge circuit to be turned off after controlling the AC side half-bridge circuit to operate in the target freewheeling path for a preset time length.

[0104] In one example embodiment, the preset time length is in a range of 1 microsecond to 100 milliseconds.

[0105] In one example embodiment, the target freewheeling path includes a positive freewheeling path and a negative freewheeling path, and the controller is further configured to, after controlling the AC side half-bridge circuit to operate in the target freewheeling path corresponding to the current polarity, control the target freewheeling path to switch from the positive freewheeling path to the negative freewheeling path or from the negative freewheeling path to the positive freewheeling path when detecting that the polarity of the AC side grid voltage changes.

[0106] The embodiments of the present disclosure further provide a chip, which comprises a memory and a processor, the memory stores a computer program, and the processor implements the steps in the above method embodiments when executing the computer program.

[0107] In an embodiment, a computer device is further provided, which comprises a memory and a processor, the memory stores a computer program, and the processor implements the steps in the above method embodiments when executing the computer program.

[0108] In an embodiment, a computer readable storage medium is provided, which stores a computer program, and the computer program implements the steps in the above method embodiments when executed by a processor.

[0109] In an embodiment, a computer program product is provided, which comprises a computer program, and the computer program implements the steps in the above method embodiments when executed by a processor.

[0110] It should be noted that the user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the present disclosure are all information and data authorized by the user or authorized by all parties, and the collection, use and processing of the related data need to comply with relevant regulations.

[0111] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage medium, and when the computer program is executed, the processes of the above-mentioned embodiments of each method can be included. Any reference to memory, database or other medium used in each embodiment provided by the present disclosure can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical storage, high-density embedded non-volatile memory, resistive memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration but not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The database involved in each embodiment provided by the present disclosure can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a block chain, etc., without being limited thereto. The processor involved in each embodiment provided by the present disclosure can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., without being limited thereto.

[0112] Each technical feature of the above-mentioned embodiments can be combined arbitrarily. In order to make the description simple, all possible combinations of each technical feature in the above-mentioned embodiments are not described, however, as long as the combination of these technical features does not exist contradictory, it should be considered as the scope of the present disclosure.

[0113] The above-mentioned embodiments only express several implementation manners of the present disclosure, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent application. It should be noted that for those skilled in the art, without departing from the concept of the present disclosure, a number of modifications and improvements can be made, which are within the scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure should be subject to the appended claims.

Claims

1. A resonant converter, wherein, The resonant converter comprises a DC side bridge arm circuit, a transformer, an AC side half-bridge circuit, a filter capacitor and a controller; The AC side half-bridge circuit comprises an upper bridge arm circuit, a lower bridge arm circuit and a resonant capacitor; One end of the transformer is connected with the DC side bridge arm circuit, and the other end of the transformer is connected with the AC side half-bridge circuit; The filter capacitor is connected in parallel with an output end of the AC side half-bridge circuit, and a capacitance value of the filter capacitor is greater than a capacitance value of the resonant capacitor; The controller is configured to acquire a current polarity of an AC side grid voltage in response to a corresponding clamping signal of the resonant converter, and control the AC side half-bridge circuit to work in a target freewheeling path corresponding to the current polarity to transfer leakage energy to the filter capacitor.

2. The resonant converter of claim 1, wherein, A ratio between the capacitance value of the filter capacitor and the capacitance value of the resonant capacitor is greater than 10.

3. The resonant converter of claim 1, wherein, The upper bridge arm circuit of the AC side half-bridge circuit comprises a first switch device and a second switch device, the lower bridge arm circuit of the AC side half-bridge circuit comprises a third switch device and a fourth switch device, and the second switch device and the third switch device are respectively connected with a bridge arm midpoint of the AC side half-bridge circuit.

4. The resonant converter of claim 1, wherein, The resonant converter further comprises a filter impedance; and the filter impedance and the filter capacitor form a filter circuit.

5. The resonant converter of claim 3, wherein, The controller is configured to acquire a current polarity of an AC side grid voltage in response to a corresponding clamping signal of the resonant converter, and control the AC side half-bridge circuit to work in a target freewheeling path corresponding to the current polarity. The controller is configured to control a first switch device group to be turned on and a second switch device group to be turned off when the current polarity is positive, and control the second switch device group to be turned on and the first switch device group to be turned off when the current polarity is negative. The first switch device group comprises two switch devices in the AC side half-bridge circuit, and the second switch device group comprises the other two switch devices in the AC side half-bridge circuit.

6. The resonant converter of claim 3, wherein, The controller is configured to acquire a current polarity of an AC side grid voltage in response to a corresponding clamping signal of the resonant converter, and control the AC side half-bridge circuit to work in a target freewheeling path corresponding to the current polarity.

7. The resonant converter of claim 1, wherein, The controller is configured to acquire a current phase of the AC side grid voltage, and determine the current polarity according to the current phase.

8. The resonant converter of claim 1, wherein, The controller is configured to obtain a current polarity of the AC side grid voltage in response to the corresponding clamped wave signal of the resonant converter, including: the controller is configured to obtain a current instantaneous voltage of the AC side grid voltage, and determine the current polarity according to the instantaneous voltage.

9. The resonant converter of claim 1, wherein, The controller is further configured to control all switching devices of the AC side half-bridge circuit to be turned off after controlling the AC side half-bridge circuit to work in the target freewheeling path for a preset time length.

10. The resonant converter of claim 9, characterized in that, The preset time length ranges from 1 microsecond to 100 milliseconds.

11. The resonant converter of claim 1, wherein, The target freewheeling path includes a positive freewheeling path and a negative freewheeling path, and the controller is further configured to, after controlling the AC side half-bridge circuit to work in the target freewheeling path corresponding to the current polarity, control the target freewheeling path to switch from the positive freewheeling path to the negative freewheeling path or from the negative freewheeling path to the positive freewheeling path when detecting that the polarity of the AC side grid changes.

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