A power electronic converter, a resonant balancing circuit and a method of controlling the same

Abstract

The application provides a power electronic converter, a resonant balancing circuit and a control method thereof. The resonant balancing circuit is provided with a resonant component between the midpoints of the switching tubes connected to each half bus capacitor. By controlling the on-off of each switching tube, the resonant component can transfer energy to the two half bus capacitors, so as to realize voltage balance between the two half bus capacitors. Moreover, each switching tube is set to switch the on-off state when the resonant current of the resonant component is zero, so as to realize soft switching control of each switching tube and reduce the loss. In addition, only four power devices, i.e. the first to fourth switching tubes, are needed in the resonant balancing circuit, so as to avoid the problem of high cost caused by too many power devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, in particular to a power electronic converter, a resonant balancing circuit and a control method thereof. BACKGROUND

[0002] With the development of power electronics technology, multi-level technology is increasingly common. However, due to the complex application conditions of the circuit, in order to ensure the balance of the capacitor voltage division, the balancing circuit has been studied.

[0003] The conventional balancing circuit currently includes two-level balancing bridge, three-level balancing bridge, and can be divided into resonant balancing bridge, non-resonant balancing bridge, etc. In general, some balancing circuits use hard switching technology, which has the problem of large balancing circuit loss. Some balancing circuits use resonant technology, but require more power devices, which has the problem of high cost. SUMMARY

[0004] Therefore, the present application provides a power electronic converter, a resonant balancing circuit and a control method thereof, which reduces the loss and cost.

[0005] To achieve the above object, the present application provides the following technical solutions:

[0006] The first aspect of the present application provides a resonant balancing circuit, comprising: a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and a resonant component; wherein,

[0007] The first switch tube and the second switch tube are connected in series, and the branch after series connection is connected in parallel with a positive half bus capacitor;

[0008] The third switch tube and the fourth switch tube are connected in series, and the branch after series connection is connected in parallel with a negative half bus capacitor;

[0009] The connection point of the second switch tube and the third switch tube is connected to the connection point of the positive half bus capacitor and the negative half bus capacitor;

[0010] The resonant component has one end connected to the connection point of the first switch tube and the second switch tube, and the other end connected to the connection point of the third switch tube and the fourth switch tube;

[0011] The first switch tube, the second switch tube, the third switch tube and the fourth switch tube switch the on-off state when the resonant current of the resonant component is zero.

[0012] Optionally, the resonant component comprises a resonant capacitor and a resonant inductor connected in series.

[0013] Optionally, each switch tube comprises a body diode or is provided with an anti-parallel diode.

[0014] Optionally, the soft start circuit is further included.

[0015] The soft start circuit is connected in parallel with the first switch tube; or,

[0016] The soft start circuit is connected in parallel with the fourth switch tube.

[0017] Optionally, the soft start circuit includes a resistor.

[0018] The second aspect of the present application provides a control method of a resonant balancing circuit, the resonant balancing circuit being any one of the resonant balancing circuits according to the first aspect, and the control method comprising:

[0019] S101, acquiring voltages of positive and negative half bus capacitors;

[0020] S102, determining whether a voltage difference between the two half bus capacitors is greater than or equal to a preset value;

[0021] If the voltage difference is greater than or equal to the preset value, step S103 is performed;

[0022] S103, controlling on-off of corresponding switch tubes in the resonant balancing circuit, transferring energy through resonant components in the resonant balancing circuit, and realizing voltage balance between the two half bus capacitors.

[0023] Optionally, before step S101, the method further comprises:

[0024] S100, pre-charging the resonant components to make their resonant capacitor voltages reach voltages of any half bus capacitor when power is turned on.

[0025] Optionally, when the resonant balancing circuit includes a soft start circuit, step S100 comprises:

[0026] The resonant components are pre-charged by the soft start circuit to make their resonant capacitor voltages reach voltages of the half bus capacitor connected with the soft start circuit while the two half bus capacitors are powered by a DC bus.

[0027] Optionally, before step S103, the method further comprises:

[0028] The voltage of the resonant components changes in the same way as the voltage of the corresponding half bus capacitor.

[0029] Optionally, if the resonant capacitor voltage is the same as the voltage of the half bus capacitor with smaller voltage, step S103 comprises:

[0030] S201, control the switch tube in the first path to conduct, make the voltage of two half bus capacitors greater one charge the resonance component;

[0031] S202, control the switch tube in the second path to conduct, make the resonance component discharge to the voltage smaller one of two half bus capacitors;

[0032] Return to step S102, until the difference between the voltage is less than the preset value;

[0033] If the resonance capacitor voltage is the same as the voltage of the voltage greater one of two half bus capacitors, step S103 includes:

[0034] S301, control the switch tube in the first path to conduct, make the resonance component discharge to the voltage smaller one of two half bus capacitors;

[0035] S302, judge whether the difference between the voltage of two half bus capacitors is greater than or equal to the preset value;

[0036] If the difference between the voltage is still greater than or equal to the preset value, step S303 is executed;

[0037] S303, control the switch tube in the second path to conduct, make the voltage greater one of two half bus capacitors charge the resonance component;

[0038] Return to step S301, until the difference between the voltage is less than the preset value.

[0039] Optionally, if the resonance capacitor voltage is the same as the voltage of the negative half bus capacitor, the switch tube in the first path is: the first switch tube and the third switch tube;The switch tube in the second path is: the second switch tube and the fourth switch tube;

[0040] If the resonance capacitor voltage is the same as the voltage of the positive half bus capacitor, the switch tube in the first path is: the second switch tube and the fourth switch tube;The switch tube in the second path is: the first switch tube and the third switch tube.

[0041] Optionally, the conduction time of each switch tube is within the preset range of half resonance period of the resonance component.

[0042] The third aspect of the present application provides an electric power electronic converter, comprising: a main circuit and a control unit;

[0043] The positive and negative poles of the DC bus in the main circuit are connected with the resonance balancing circuit as any one of the first aspect of the present application;

[0044] The main circuit is controlled by the control unit;

[0045] The control unit is used to execute the control method for the resonant balanced circuit as described in any of the second aspects of this application.

[0046] The resonant balancing circuit provided in this application has a resonant component placed between the midpoints of the switching transistors connected to each half-bus capacitor. By controlling the on / off state of each switching transistor, the resonant component can transfer energy between the two half-bus capacitors, achieving voltage balance between them. Furthermore, by setting each switching transistor to switch on / off state when the resonant current of the resonant component is zero, soft-switching control of each switching transistor can be achieved, reducing losses. In addition, this resonant balancing circuit only requires four power devices, namely the first to fourth switching transistors, thus avoiding the problem of high cost caused by a large number of power devices. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the resonant balance circuit provided in the embodiments of this application;

[0049] Figure 2 A schematic diagram of the resonant balance circuit provided for the prior art;

[0050] Figure 3 This is a schematic diagram of the specific structure of the resonant balance circuit provided in the embodiments of this application;

[0051] Figure 4a and Figure 4b These are schematic diagrams of two other specific structures of the resonant balance circuit provided in the embodiments of this application;

[0052] Figure 5 for Figure 4a The diagram shows the current path for pre-charging the resonant capacitor under the structure shown.

[0053] Figure 6 , Figure 7 , Figure 8a and Figure 8b Four flowcharts are shown for the control methods of the resonant balance circuit provided in the embodiments of this application.

[0054] Figure 9a and Figure 9b They are respectively Figure 4a Two schematic diagrams of the energy transfer loop under the structure shown. Detailed Implementation

[0055] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort belong to the scope of the present application.

[0056] In the present application, the terms "comprising", "containing" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitation, the element defined by the sentence "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0057] The present application provides a resonant balancing circuit, which reduces loss and cost.

[0058] The resonant balancing circuit balances the voltage of the positive half bus capacitor C1 and the negative half bus capacitor C2. The positive half bus capacitor C1 and the negative half bus capacitor C2 can be the capacitor between the positive and negative poles of the DC bus in a power electronic converter such as an inverter.

[0059] As shown in Figure 1 The resonant balancing circuit includes a first switch tube T1, a second switch tube T2, a third switch tube T3, a fourth switch tube T4 and a resonant component 101. Wherein:

[0060] The first switch tube T1 and the second switch tube T2 are connected in series, and the branch after series connection is connected in parallel with the positive half bus capacitor C1. The connection point between the first switch tube T1 and the second switch tube T2 is connected with one end of the resonant component 101.

[0061] The third switch tube T3 and the fourth switch tube T4 are connected in series, and the branch after series connection is connected in parallel with the negative half bus capacitor C2. The connection point between the third switch tube T3 and the fourth switch tube T4 is connected with the other end of the resonant component 101.

[0062] The connection point between the second switch tube T2 and the third switch tube T3 is connected with the connection point of the positive half bus capacitor C1 and the negative half bus capacitor C2.

[0063] The first switch tube T1, the second switch tube T2, the third switch tube T3 and the fourth switch tube T4 switch on-off state when the resonant current of the resonant component 101 is zero.

[0064] When the voltage of the positive half bus capacitor C1 and the negative half bus capacitor C2 is unbalanced, for example, the difference between the two voltages is greater than or equal to a preset value, a path for energy transfer between the positive half bus capacitor C1 and the negative half bus capacitor C2 can be provided by controlling the on-off of the corresponding switch tube, and due to the presence of the resonance component 101, it not only can serve as a transit station when energy is transferred between the positive half bus capacitor C1 and the negative half bus capacitor C2, but also can achieve soft switching control of each switch tube by setting the action time of each switch tube at the time when the resonance current is zero, thereby avoiding the corresponding loss. In addition, when the voltage of the positive half bus capacitor C1 and the negative half bus capacitor C2 is balanced, each switch tube can remain in an off state, thereby greatly reducing the loss.

[0065] It is worth noting that in actual application, the on time of the switch tube providing a path for the above energy transfer can be set to be approximately equal to 1 / 2 of the resonance period of the resonance component 101, as long as soft switching operation can be achieved.

[0066] The resonance balancing circuit provided by the embodiment has a resonance component 101 between the midpoints of the switch tubes connected to the half bus capacitors, and by controlling the on-off of the switch tubes, the resonance component 101 can transfer energy between the two half bus capacitors to balance the voltage between the two half bus capacitors. Moreover, by setting the on-off state of each switch tube at the time when the resonance current of the resonance component 101 is zero, soft switching control of each switch tube can be achieved, thereby reducing the loss.

[0067] In addition, only four power devices, i.e., the first switch tube T1 to the fourth switch tube T4, are needed in the resonance balancing circuit, which saves two diodes compared with the conventional three-level balancing bridge shown in Figure 2 , thereby avoiding the problem of high cost caused by too many power devices.

[0068] On the basis of the above embodiment, referring to Figure 3 , the resonance component 101 of the resonance balancing circuit includes a resonance capacitor Cf and a resonance inductor Lf connected in series.

[0069] After the parameters of the resonance capacitor Cf and the resonance inductor Lf are determined, the resonance frequency and the resonance period can be determined, and the action timing and the on time of the four switch tubes, i.e., the first switch tube T1 to the fourth switch tube T4, can be set in the corresponding control software, thereby achieving voltage balancing between the two half bus capacitors C1 and C2 with low loss. The action timing of each switch tube can be seen below.

[0070] In actual application, in order to improve the balancing response speed, the resonance capacitor Cf can be pre-charged to be equal to the voltage of the two half bus capacitors, thereby directly transferring the energy difference between the two half bus capacitors when the voltage of the two half bus capacitors is unbalanced.

[0071] It is worth mentioning that an additional power supply can be used to pre-charge the resonance capacitor Cf, but in view of the actual application, each switch tube generally includes a body diode or is provided with an anti-parallel diode, as shown in Figure 1 and Figure 3 Therefore, more preferably, the resonance balancing circuit further comprises a soft start circuit 102, as shown in Figure 4a The soft start circuit 102 is connected in parallel with the fourth switch tube T4, or as shown in Figure 4b The soft start circuit 102 is connected in parallel with the first switch tube T1. The soft start circuit 102 includes a resistor R.

[0072] Taking the structure shown in Figure 4a as an example, as shown in Figure 5 When the DC bus is powered, the current paths 1 and 2 exist at the same time, and at this time the circuit is equivalent to a series structure of the negative half bus capacitor C2 and the resonance capacitor Cf+resonance inductor Lf+resistor R in parallel; under the condition that the resistor R is properly selected, pre-charging of the resonance capacitor Cf can be achieved.

[0073] Moreover, when the circuit enters a steady state, if the potentials of the positive half bus capacitor C1 and the negative half bus capacitor C2 change, due to the existence of the resistor R path, the voltage on the resonance capacitor Cf will be clamped by the negative half bus capacitor C2, that is, the resonance capacitor Cf can automatically follow and keep the voltage of the resonance capacitor Cf consistent with the voltage of the negative half bus capacitor C2.

[0074] Figure 4b Under the structure, the voltage of the resonance capacitor Cf will be consistent with the voltage of the positive half bus capacitor C1, and the principle is similar to the above content and will not be described again.

[0075] In this embodiment, by setting the soft start circuit 102, not only can the pre-charging of the resonance capacitor Cf at the initial power-on be achieved, but also the automatic tracking of the voltage of the resonance capacitor Cf when the voltage difference between the two half bus capacitors C1 and C2 does not exceed a preset value can be achieved.

[0076] Another embodiment of the present application also provides a control method of a resonance balancing circuit, the structure and principle of the resonance balancing circuit can be referred to the above embodiments and will not be described here; the control method, as shown in Figure 6 , comprises:

[0077] S101, acquiring the voltages of the positive half bus capacitor and the negative half bus capacitor.

[0078] Specifically, the voltages can be acquired by a voltage detection module inside a power electronic converter where the two half bus capacitors are located.

[0079] S102. Determine whether the voltage difference between the two half-bus capacitors is greater than or equal to a preset value.

[0080] If the voltage difference is greater than or equal to the preset value, then proceed to step S103. If the voltage difference is less than the preset value, then keep all switching transistors off to avoid losses.

[0081] S103. Control the on / off state of the corresponding switching transistors in the resonant balance circuit, and transfer energy through the resonant components in the resonant balance circuit to achieve voltage balance between the two half-bus capacitors.

[0082] The above process can achieve voltage balance between the two half-bus capacitors. Moreover, since each switch in the resonant balance circuit switches between on and off states when the resonant current of the resonant component is zero, soft switching control of each switch can be achieved, reducing losses.

[0083] In addition, to achieve pre-charging of the resonant capacitor in the resonant component, the control method further includes, before step S101,... Figure 7 As shown:

[0084] S100: When powered on, precharge the resonant component so that the voltage of its resonant capacitor reaches the voltage of any half of the bus capacitor.

[0085] Moreover, when the resonant balance circuit includes Figure 4b or Figure 4b When the soft start circuit 102 is shown, step S100 specifically includes: while the DC bus connected to the two half bus capacitors is energized, the soft start circuit pre-charges the resonant component so that the resonant capacitor voltage of the resonant component reaches the voltage of the half bus capacitor connected to the soft start circuit.

[0086] When the resonant balance circuit includes Figure 4a In the soft-start circuit 102 shown, the half-bus capacitor connected to the soft-start circuit 102 is the negative half-bus capacitor C2. Specifically, step S100 causes the resonant capacitor voltage (i.e., the voltage of the resonant capacitor Cf) to reach the voltage of the negative half-bus capacitor C2. When the resonant balancing circuit includes... Figure 4b When the soft start circuit 102 is shown, the half bus capacitor connected to the soft start circuit 102 is the positive half bus capacitor C1. Specifically, step S100 will cause the resonant capacitor voltage to reach the voltage of the positive half bus capacitor C1.

[0087] Furthermore, based on the principle described in the above embodiments, before step S103, that is, when there is no voltage imbalance between the two half-bus capacitors, the control method further includes: the voltage of the resonant component follows the voltage of the corresponding half-bus capacitor in the same manner. That is, for Figure 4aThe structure shown can make the resonance capacitor voltage consistent with the voltage of the negative half bus capacitor C2 through the soft start circuit 102; and for Figure 4b The structure shown can make the resonance capacitor voltage consistent with the voltage of the positive half bus capacitor C1 through the soft start circuit 102.

[0088] Regardless of the resonance capacitor voltage being pre-charged to the voltage of which half bus capacitor, when the voltage of the two half bus capacitors is unbalanced:

[0089] (1) If the resonance capacitor voltage is the same as the voltage of the smaller one of the two half bus capacitors, see Figure 8a (based on the example of Figure 6 ), step S103, specifically includes:

[0090] S201, control the switch tube in the first path to be turned on, so that the larger one of the two half bus capacitors charges the resonance assembly.

[0091] S202, control the switch tube in the second path to be turned on, so that the resonance assembly discharges to the smaller one of the two half bus capacitors.

[0092] Return to step S102 until the voltage difference is less than the preset value.

[0093] (2) If the resonance capacitor voltage is the same as the voltage of the larger one of the two half bus capacitors, see Figure 8b (based on the example of Figure 6 ), step S103, specifically includes:

[0094] S301, control the switch tube in the first path to be turned on, so that the resonance assembly discharges to the smaller one of the two half bus capacitors.

[0095] S302, judge whether the voltage difference of the two half bus capacitors is greater than or equal to the preset value.

[0096] If the voltage difference is still greater than or equal to the preset value, step S303 is executed.

[0097] S303, control the switch tube in the second path to be turned on, so that the larger one of the two half bus capacitors charges the resonance assembly.

[0098] Return to step S301 until the voltage difference is less than the preset value.

[0099] In the above two specific processes, if applied to Figure 4aIn the structure shown, that is, the resonance capacitor voltage is the same as the voltage of the negative half bus capacitor C2, then the switch tubes in the first path are the first switch tube T1 and the third switch tube T3, and the switch tubes in the second path are the second switch tube T2 and the fourth switch tube T4. If applied to Figure 4b In the structure shown, that is, the resonance capacitor voltage is the same as the voltage of the positive half bus capacitor C1, then the switch tubes in the first path are the second switch tube T2 and the fourth switch tube T4, and the switch tubes in the second path are the first switch tube T1 and the third switch tube T3. Moreover, the conduction time of each switch tube is within a preset range of half of the resonance period of the resonance assembly 101, that is, in actual application, the conduction time of each path can be set to be equal to 1 / 2 of the resonance period of the resonance assembly 101, and the preset range is not limited specifically, as long as soft switching operation can be realized, which is within the protection scope of the present application.

[0100] The following will be described by taking the structure shown in FIG. 2 as an example. Figure 4a

[0101] (1) If Vc1>Vc2, wherein Vc1 is the voltage of the positive half bus capacitor C1, and Vc2 is the voltage of the negative half bus capacitor C2, then according to the control method shown in FIG. 2, the specific operation process of the control method is as follows. Figure 9a

[0102] 1) First, the first switch tube T1 and the third switch tube T3 are turned on, at this time, the positive half bus capacitor C1 is discharged through the loop 1, and the resonance capacitor Cf and the resonance inductor Lf resonate.

[0103] 2) When the resonance current on the resonance inductor Lf is 0, the voltage of the resonance capacitor Cf reaches the maximum, and the first switch tube T1 and the third switch tube T3 are turned off; at this time, the first switch tube T1 and the third switch tube T3 are zero-current turned off. At the same time, since the first switch tube T1 and the third switch tube T3 are turned off, the resonance capacitor Cf cannot be discharged, and Vcf>Vc1; the energy of the positive half bus capacitor C1 is transferred to the resonance capacitor Cf.

[0104] 3) Then, the second switch tube T2 and the fourth switch tube T4 are turned on, at this time, the second switch tube T2 and the fourth switch tube T4 are zero-current turned on. At this time, since Vcf>Vc1>Vc2, a resonance discharge loop is formed through the loop 2.

[0105] 4) When the resonance discharge ends, that is, when the resonance inductor Lf current is 0, the discharge ends. At this time, the second switch tube T2 and the fourth switch tube T4 are turned off, and the two are zero-current turned off, realizing the energy transfer from the resonance capacitor Cf to the negative half bus capacitor C2.

[0106] ​​5) If Vc1-Vc2 still exceeds the preset value after the above conversion, steps 1) to 3) can be repeated; until the difference between the voltages of the two half bus capacitors is less than the preset value.

[0107] 6) The above steps can be integrated to achieve energy transfer from the positive half bus capacitor C1 to the negative half bus capacitor C2, and to achieve voltage balancing of the two half bus capacitors C1 and C2.

[0108] (2) If Vc2>Vc1, where Vc1 is the voltage of the positive half bus capacitor C1 and Vc2 is the voltage of the negative half bus capacitor C2, then in combination with Figure 9b , the specific operation process of the control method is as follows:

[0109] 1) At this time, since the resonant capacitor Cf is clamped by the negative half bus capacitor C2 under steady state conditions, it can be considered that Vcf=Vc2>Vc1. Vcf is the voltage of the resonant capacitor Cf, that is, the resonant capacitor voltage in the above.

[0110] 2) Turn on the first switch tube T1 and the third switch tube T3. Since Vcf>Vc1, at this time the resonant capacitor Cf forms a resonant discharge circuit through loop 1, and energy is transferred from the resonant capacitor Cf to the positive half bus capacitor C1, achieving charging of the positive half bus capacitor C1.

[0111] 3) When the resonant discharge ends, turn off the first switch tube T1 and the third switch tube T3. At this time, Vcf<Vc1.

[0112] 4) If Vc2-Vc1 still exceeds the preset value at this time, turn on the second switch tube T2 and the fourth switch tube T4. Since Vc1>Vcf, the resonant capacitor Cf forms a resonant charging circuit through loop 2, achieving energy transfer from the negative half bus capacitor C2 to the resonant capacitor Cf.

[0113] 5) At the end of the resonance, turn off the second switch tube T2 and the fourth switch tube T4.

[0114] 6) Repeat step 2) to achieve energy transfer from the resonant capacitor Cf to the positive half bus capacitor C1.

[0115] 7) The above steps can be integrated to achieve energy transfer from the negative half bus capacitor C2 to the positive half bus capacitor C1, thereby achieving balanced control of the positive half bus capacitor C1 and the negative half bus capacitor C2.

[0116] For Figure 4b structures, the two cases are similar, except that Figure 4aIn the case shown, the sequence of turning on the first switch T1 and the third switch T3 first and then turning on the second switch T2 and the fourth switch T4 is changed to turning on the second switch T2 and the fourth switch T4 first and then turning on the first switch T1 and the third switch T3, and details are not repeated here.

[0117] Another embodiment of the present application also provides an electric power electronic converter, comprising: a main circuit and a control unit; wherein:

[0118] The resonant balancing circuit as described in any of the above embodiments is connected between the positive and negative poles of a DC bus in the main circuit; the specific topology of the main circuit is not limited, as long as the main circuit is provided with a DC bus, and the positive and negative poles of the DC bus are provided with a positive half bus capacitor and a negative half bus capacitor connected in series, and the two half bus capacitors are further connected with the resonant balancing circuit, all of which are within the protection scope of the present application.

[0119] The main circuit is controlled by the control unit; the control unit is used to execute the control method of the resonant balancing circuit as described in any of the above embodiments. The junction and principle of the resonant balancing circuit, and the specific process and principle of the control method are described in the above embodiments, and details are not repeated here.

[0120] The electric power electronic converter provided by the embodiment can realize soft switching of the switching device in the resonant balancing circuit, greatly reducing the power loss; and compared with the conventional three-level balancing circuit, the resonant balancing circuit has fewer power devices and lower cost.

[0121] The same and similar parts among the embodiments in the present specification can be referred to each other, and each embodiment mainly describes the difference from other embodiments. Especially, for the system or system embodiment, since it is basically similar to the method embodiment, it is described more simply, and the related parts can be referred to the part of the method embodiment. The system and system embodiment described above are only illustrative, and the units described as separate components can be or can not be physically separated, and the components shown as units can be or can not be physical units, that is, they can be located in one place or distributed on multiple network units. According to the actual needs, some or all of the modules can be selected to achieve the purpose of the embodiment. Those skilled in the art can understand and implement without creative labor.

[0122] Those skilled in the art will further realize that the mechanisms of the various examples described herein are capable of being implemented using any number of combinations of the described features. Accordingly, these examples are not limited to the mechanisms described herein, but rather, the intent is to cover all modifications and alternatives equivalent thereto. The preceding description of the examples is illustrative, and not restrictive. Many other examples will be apparent to those of skill in the art upon reviewing the above description. The scope of the examples should, therefore, be determined not with reference to the above description, but instead should be given to the appended claims, along with their full scope of equivalents.

[0123] The above description of disclosed examples is merely intended to illustrate the features of the various embodiments described herein. The features of the various embodiments described in this specification can be replaced or combined with each other, enabling those skilled in the art to implement or use the present application. Various modifications to the examples will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other examples without departing from the spirit or scope of the application. Therefore, the present application will not be limited to the examples shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A resonant balanced circuit, characterized in that, include: The first switch transistor, the second switch transistor, the third switch transistor, the fourth switch transistor, and the resonant assembly; wherein, The first switch is connected in series with the second switch, and the branch after series connection is connected in parallel with the positive half bus capacitor. The third switch is connected in series with the fourth switch, and the branch after series connection is connected in parallel with the negative half bus capacitor. The connection point between the second switch and the third switch is connected to the connection point between the positive half bus capacitor and the negative half bus capacitor. The resonant component has one end connected to the connection point of the first switch and the second switch, and the other end connected to the connection point of the third switch and the fourth switch. The first switch, the second switch, the third switch, and the fourth switch switch switch to switch on and off states when the resonant current of the resonant component is zero. Also includes: soft start circuit; The soft-start circuit is connected in parallel with the first switching transistor; or... The soft start circuit is connected in parallel with the fourth switch. The soft-start circuit is used to pre-charge the resonant capacitor in the resonant component during the initial power-on phase, and also to track the voltage of the resonant capacitor when the voltage difference between the two half-bus capacitors does not exceed a preset value.

2. The resonant balanced circuit according to claim 1, characterized in that, The resonant components include a resonant capacitor and a resonant inductor connected in series.

3. The resonant balanced circuit according to claim 1 or 2, characterized in that, Each switching transistor includes a body diode, or each transistor has an anti-parallel diode.

4. The resonant balanced circuit according to claim 1, characterized in that, The soft-start circuit includes a resistor.

5. A control method for a resonant balanced circuit, characterized in that, The resonant balancing circuit is the resonant balancing circuit as described in any one of claims 1 to 4, and the control method includes: S101. Obtain the voltage of the positive half-bus capacitor and the negative half-bus capacitor; S102. Determine whether the voltage difference between the two half-bus capacitors is greater than or equal to a preset value. If the voltage difference is greater than or equal to the preset value, then step S103 is executed; S103. Control the on / off state of the corresponding switching transistors in the resonant balance circuit, and transfer energy through the resonant components in the resonant balance circuit to achieve voltage balance between the two half-bus capacitors.

6. The control method for the resonant balanced circuit according to claim 5, characterized in that, Before step S101, the method further includes: S100. When powered on, the resonant component is pre-charged so that its resonant capacitor voltage reaches the voltage of any half of the bus capacitor.

7. The control method for the resonant balanced circuit according to claim 6, characterized in that, When the resonant balancing circuit includes a soft-start circuit, step S100 includes: While the DC bus connected to the two half-bus capacitors is energized, the soft-start circuit pre-charges the resonant component, so that the resonant capacitor voltage of the resonant component reaches the voltage of the half-bus capacitor connected to the soft-start circuit.

8. The control method for the resonant balanced circuit according to claim 7, characterized in that, Before step S103, the method further includes: The voltage of the resonant component changes in the same way as the voltage of the corresponding half-bus capacitor.

9. The control method for the resonant balanced circuit according to any one of claims 6 to 8, characterized in that, If the voltage of the resonant capacitor is the same as the voltage of the smaller of the two half-bus capacitors, then step S103 includes: S201. Control the switching transistor in the first path to turn on, so that the larger voltage of the two half-bus capacitors charges the resonant component. S202. Control the switching transistor in the second path to turn on, so that the resonant component discharges to the one with the smaller voltage in the two half-bus capacitors. Return to step S102 until the voltage difference is less than the preset value; If the voltage of the resonant capacitor is the same as the voltage of the larger of the two half-bus capacitors, then step S103 includes: S301. Control the switching transistor in the first path to turn on, so that the resonant component discharges to the half-bus capacitor with the smaller voltage. S302. Determine whether the voltage difference between the two half-bus capacitors is greater than or equal to the preset value; If the voltage difference is still greater than or equal to the preset value, then proceed to step S303; S303, control the switch in the second path to turn on, so that the larger voltage of the two half-bus capacitors charges the resonant component; Return to step S301 until the voltage difference is less than the preset value.

10. The control method for the resonant balanced circuit according to claim 9, characterized in that, If the voltage of the resonant capacitor is the same as the voltage of the negative half-bus capacitor, then the switching transistors in the first path are: the first switching transistor and the third switching transistor; the switching transistors in the second path are: the second switching transistor and the fourth switching transistor. If the voltage of the resonant capacitor is the same as the voltage of the positive half-bus capacitor, then the switching transistors in the first path are: the second switching transistor and the fourth switching transistor; the switching transistors in the second path are: the first switching transistor and the third switching transistor.

11. The control method for the resonant balanced circuit according to claim 9, characterized in that, The conduction time of each switch is within a preset range of half the resonant period of the resonant component.

12. A power electronic converter, characterized in that, include: Main circuit and control unit; The main circuit is connected between the positive and negative terminals of the DC bus as described in any one of claims 1 to 4; The main circuit is controlled by the control unit; The control unit is used to execute the control method for the resonant balance circuit as described in any one of claims 5 to 11.

Images