Control method of power conversion unit and power converter

Abstract

The invention provides a control method of a power conversion unit and a power converter. Under the condition that the direct-current capacitor in the power conversion unit is charged, the two ends of the direct-current capacitor are approximately equal to the maximum value of the line voltage between the first phase alternating current and the second phase alternating current, and the amplitudes of the line voltages between any two phases of alternating current are equal, so that under the condition that the direct-current capacitor is charged, the maximum value of the line voltages between the first phase alternating current and the second phase alternating current is equal. The first-phase alternating current is cut out of the power conversion unit, the third-phase alternating current is connected into the power conversion unit, and only small impact current can be caused. Besides, the first phase alternating current is connected to the power conversion unit through the slow start circuit, so that only small impact current is caused, and after the second phase alternating current and the third phase alternating current are directly connected to the power conversion unit, the first phase alternating current is connected to the power conversion unit through the slow start module, and only small impact current is caused. In conclusion, in the power-on process of the power conversion unit, the impact current of the direct-current capacitor is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power-on control, and in particular to a control method of a power conversion unit and a power converter. Background Art

[0002] At present, when the power conversion unit needs to be powered on, the first phase AC is first connected to the power conversion unit through the slow start module, and the second phase AC is connected to the power conversion unit at the same time. Then the third phase AC is connected to the power conversion unit.

[0003] Since there is no slow-start module between the third-phase AC power and the second-phase AC power, a surge current will flow through the DC capacitor when the third-phase AC power is connected, thereby causing a large surge current on the DC capacitor when the power conversion unit is powered on.

[0004] Therefore, how to reduce the impact current of the DC capacitor during the power-on process of the power conversion unit is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of this, the present invention provides a control method of a power conversion unit and a power converter, so as to reduce the impact current of a DC capacitor during the power-on process of the power conversion unit.

[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] On one hand, the present application provides a slow start control method of a power conversion unit, wherein the input side of the power conversion unit is used to receive three-phase alternating current; the slow start control method comprises:

[0008] Using the first-phase alternating current and the second-phase alternating current to charge the DC capacitor in the power conversion unit;

[0009] If the DC capacitor is fully charged, the first-phase AC power is cut out of the power conversion unit, and the third-phase AC power is directly connected to the power conversion unit;

[0010] The first-phase alternating current is connected to the power conversion unit through a slow-start module.

[0011] Optionally, when the line voltage between the second-phase AC power and the third-phase AC power is at a zero-crossing point, the step of cutting the first-phase AC power out of the power conversion unit and directly connecting the third-phase AC power to the power conversion unit is performed.

[0012] Optionally, when the line voltage between the first-phase AC power and any one of the other two-phase AC power is at a zero-crossing point, the step of connecting the first-phase AC power to the power conversion unit through the slow-start module is performed.

[0013] Optionally, charging a DC capacitor in the power conversion unit using the first-phase alternating current and the second-phase alternating current includes:

[0014] When the power conversion unit needs to be powered on, the first-phase alternating current is connected to the power conversion unit through the slow-start module, and the second-phase alternating current is directly connected to the power conversion unit;

[0015] When the line voltage between the first-phase alternating current and the second-phase alternating current is at a zero-crossing point, the first-phase alternating current is switched from being connected to the power conversion unit via the slow-start module to being directly connected to the power conversion unit.

[0016] Optionally, the step of connecting the first-phase alternating current to the power conversion unit through the slow-start module, and directly connecting the second-phase alternating current to the power conversion unit, comprises:

[0017] When the line voltage between the first-phase alternating current and the second-phase alternating current is at a zero-crossing point, the first-phase alternating current is connected to the power conversion unit through the slow-start module and the second-phase alternating current is directly connected to the power conversion unit.

[0018] Optionally, the slow start control method further includes:

[0019] Obtaining a voltage value across the DC capacitor;

[0020] If the voltage across the DC capacitor reaches the maximum value of the line voltage between the first-phase AC power and the second-phase AC power, it is determined that the DC capacitor is fully charged;

[0021] If the voltage across the DC capacitor does not reach the maximum value of the line voltage between the first-phase AC power and the second-phase AC power, it is determined that the DC capacitor is not completely charged.

[0022] Optionally, after the step of connecting the first-phase alternating current to the power conversion unit through the slow-start module, the method further includes:

[0023] The first-phase alternating current is switched from being connected to the power conversion unit via the slow-start module to being directly connected to the power conversion unit.

[0024] On the other hand, the present application provides a power converter, comprising: a power conversion unit, a controller, three switching switches and at least one slow-start module; wherein:

[0025] The three-phase interface on the input side of the power conversion unit receives three-phase alternating current through the three switching switches respectively, wherein the two ends of at least one of the switching switches are connected in parallel with the slow-start module;

[0026] The slow-start module, the power conversion unit, and the three switching switches are all controlled by the controller, and the controller is used to execute the control method of the power conversion unit as described in any one of the above aspects of the present application.

[0027] Optionally, the slow-start module comprises: a slow-start switch and at least one slow-start resistor; wherein:

[0028] The soft-start switch is controlled by the controller;

[0029] If the number of the slow-start resistors is greater than 1, all the slow-start resistors are connected in series and in parallel, and the formed branch is connected in series with the slow-start switch;

[0030] If the number of the slow-start resistors is equal to 1, the slow-start resistors are connected in series with the slow-start switches.

[0031] Optionally, the controller is used to control the corresponding switch to close when any phase of the alternating current is directly connected to the power conversion unit, and if the switch is connected in parallel with the slow-start module, the controller is used to control the slow-start module connected in parallel with the switch to open the circuit;

[0032] The controller is used to control the slow-start module to form a path and control the switch connected in parallel with the slow-start module to disconnect when any phase of AC power is connected to the power conversion unit through the corresponding slow-start module.

[0033] Optionally, it also includes: a voltage detection module; wherein:

[0034] The voltage detection module is connected to the controller, and is used to respectively detect the voltages of the three-phase interfaces on the input side of the power conversion unit.

[0035] It can be seen from the above technical solution that the present invention provides a control method for a power conversion unit. Since the two ends of the DC capacitor are approximately equal to the maximum value of the line voltage between the first-phase alternating current and the second-phase alternating current when the DC capacitor in the power conversion unit is fully charged, and the amplitude of the line voltage between any two-phase alternating current is equal, when the DC capacitor is fully charged, the first-phase alternating current is cut out of the power conversion unit and the third-phase alternating current is connected to the power conversion unit, which will only cause a small impact current on the DC capacitor. In addition, since the first-phase alternating current is connected to the power conversion unit through a slow-start circuit, it will only cause a small impact current on the DC capacitor, so that after the second-phase alternating current and the third-phase alternating current are directly connected to the power conversion unit, the first-phase alternating current is connected to the power conversion unit through a slow-start module, which will only cause a small impact current on the DC capacitor. In summary, the control method can reduce the impact current of the DC capacitor during the power-on process of the power conversion unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0037] Figure 1 A flowchart of an implementation method of a power conversion unit control method provided in an embodiment of the present application;

[0038] Figure 2 A flowchart of another implementation of a method for controlling a power conversion unit provided in an embodiment of the present application;

[0039] Figure 3 A flowchart of another implementation of the control method of the power conversion unit provided in the embodiment of the present application;

[0040] Figure 4 A flowchart of another implementation of the method for controlling a power conversion unit provided in an embodiment of the present application;

[0041] Figure 5 A flowchart of another implementation of the control method of the power conversion unit provided in the embodiment of the present application;

[0042] Figure 6 is a schematic diagram of the line voltage between two-phase alternating current;

[0043] Figure 7A schematic diagram of the structure of an implementation of a power converter provided in an embodiment of the present application;

[0044] Figure 8 A schematic structural diagram of another implementation of a power converter provided in an embodiment of the present application;

[0045] Fig. 9 A schematic structural diagram of another embodiment of the power converter provided in the present application;

[0046] Fig.10 A schematic structural diagram of another implementation manner of the power converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0048] In this application, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0049] In order to reduce the impact current of the DC capacitor during the power-on process of the power conversion unit, an embodiment of the present application provides a control method for the power conversion unit, where the input side of the power conversion unit receives three-phase AC power.

[0050] The specific process of this control method is as follows Figure 1 As shown, the specific steps include:

[0051] S110 , using the first-phase alternating current and the second-phase alternating current to charge the DC capacitor in the power conversion unit.

[0052] Since the DC capacitor is charged by the first-phase AC power and the second-phase AC power, after the DC capacitor is fully charged, the two ends of the DC capacitor are approximately equal to the maximum value of the line voltage between the first-phase AC power and the second-phase AC power. Since the amplitude of the line voltage between any two-phase AC power is equal, that is, the maximum value of the line voltage between any two-phase AC power is equal, after the DC capacitor is fully charged, the two ends of the DC capacitor are approximately equal to the maximum value of the line voltage between any two-phase AC power.

[0053] S120: Determine whether the DC capacitor has been fully charged.

[0054] If the DC capacitor is fully charged, S130 and S140 are executed in sequence; if the DC capacitor is not fully charged, the control method of the power conversion unit is stopped.

[0055] In a specific example, an implementation of step S120 specifically includes the following steps:

[0056] S121. Obtain the voltage value across the DC capacitor.

[0057] If the voltage across the DC capacitor reaches the maximum value of the line voltage between the first phase AC power and the second phase AC power, step S122 is executed; if the voltage across the DC capacitor does not reach the maximum value of the line voltage between the first phase AC power and the second phase AC power, step S123 is executed.

[0058] S122, determining that the DC capacitor has completed charging.

[0059] S123: Determine whether the DC capacitor has not been fully charged.

[0060] The above example only shows one implementation of step S120. In practical applications, including but not limited to this, no specific limitation is made here and it may be determined according to the specific circumstances, all of which are within the scope of protection of this application.

[0061] S130: If the DC capacitor has completed charging, the first-phase AC power is cut out of the power conversion unit, and the third-phase AC power is directly connected to the power conversion unit.

[0062] Cutting the first phase AC power out of the power conversion unit means that the first phase AC power no longer flows into the power conversion unit. How to cut the first phase AC power out of the power conversion unit will be described in detail later in conjunction with the connection relationship of the power conversion unit.

[0063] Directly connecting the third-phase AC power to the power conversion unit means that the third-phase AC power directly flows into the power conversion unit without passing through an impedance. As for how to directly connect the third-phase AC power to the power conversion unit, it will be described in detail later in conjunction with the connection relationship of the power conversion unit.

[0064] After executing S130 , both the second-phase AC power and the third-phase AC power are connected to the power conversion unit, so S130 is equivalent to switching the first-phase AC power to the third-phase AC power to connect to the power conversion unit.

[0065] From the above, it can be seen that after the DC capacitor is fully charged, the two ends of the DC capacitor are approximately equal to the maximum value of the line voltage between any two phases of AC. Therefore, after the DC capacitor is fully charged, the two ends of the DC capacitor can be approximately equal to the maximum value of the line voltage between the third phase AC and the second phase AC. Therefore, after the DC capacitor is fully charged, the first phase AC is switched to the third phase AC. Since the voltage amplitudes are the same, the impact current caused by the switch on the DC capacitor is smaller.

[0066] S140, connecting the first phase AC power to the power conversion unit through the slow start module.

[0067] Connecting the first-phase AC power to the power conversion unit through the slow-start module means that the first-phase AC power needs to pass through the slow-start module before flowing into the power conversion unit. As for how to connect the first-phase AC power to the power conversion unit through the slow-start module, it will be described in detail later in conjunction with the connection relationship of the power conversion unit, and will not be repeated here.

[0068] Since the first-phase AC is connected to the power conversion unit through the slow-start circuit, which is equivalent to forming a slow-start loop between the first-phase AC and the second-phase AC, and a slow-start loop between the first-phase AC and the second-phase AC, the impact current caused on the DC capacitor is small. Therefore, after the second-phase AC and the third-phase AC are connected to the power conversion unit, the first-phase AC is connected to the power conversion unit through the slow-start module.

[0069] In summary, the control method can reduce the impact current of the DC capacitor during the power-on process of the power conversion unit.

[0070] Another embodiment of the present application provides another implementation method of a control method for a power conversion unit, and the specific process is as follows: Figure 2 As shown, this embodiment further includes the following steps before S130 in the above embodiment:

[0071] S210: Determine whether the line voltage between the second-phase alternating current and the third-phase alternating current is at a zero-crossing point.

[0072] If the line voltage between the second-phase AC power and the third-phase AC power is at a zero-crossing point, S130 is executed; if the line voltage between the second-phase AC power and the third-phase AC power is not at a zero-crossing point, the control method of the power conversion unit is stopped.

[0073] It should be noted that how to find the zero-crossing point will be described in detail below and will not be repeated here.

[0074] In this embodiment, when the line voltage between the second-phase AC and the third-phase AC is at a zero point, the first-phase AC is switched to the third-phase AC, which is equivalent to: under zero voltage, the first-phase AC is switched to the third-phase AC. Therefore, when the first-phase AC is switched to the third-phase AC, a smaller current is generated on the DC capacitor, thereby further reducing the impact current on the DC capacitor during the power-on process of the power conversion unit.

[0075] Another embodiment of the present application provides another implementation of the control method of the power conversion unit. The specific process can be found in Figure 3 ( Figure 3 Only in Figure 2 This embodiment is demonstrated on the basis of FIG. 1 ), before S140 in the above embodiment, this embodiment further includes the following steps:

[0076] S310, determining whether the line voltage between the first-phase alternating current and any one of the other two-phase alternating currents is at a zero-crossing point.

[0077] If the line voltage between the first phase AC and any of the other two phases AC is at a zero crossing point, execute S140; if the line voltage between the first phase AC and each of the other two phases AC is not at a zero crossing point, stop executing the control method of the power conversion unit.

[0078] Optionally, any one of the other two phases of AC power may be the second phase AC power or the third phase AC power, which is not specifically limited here and may be determined according to specific circumstances, and all are within the protection scope of this application.

[0079] It should be noted that how to find the zero-crossing point will be described in detail below and will not be repeated here.

[0080] In this embodiment, when the line voltage between the first-phase AC power and any one of the other two-phase AC power is at a zero-crossing point, the first-phase AC power is connected to the power conversion unit through the slow-start module, which is equivalent to: under zero voltage, the first-phase AC power is connected to the power conversion unit through the slow-start module. Therefore, when the first-phase AC power is connected to the power conversion unit through the slow-start module, the current generated on the DC capacitor is smaller, and thus when the first-phase AC power is connected to the power conversion unit through the slow-start module, the impact current caused on the DC capacitor is smaller. Therefore, this implementation can further reduce the impact current of the DC capacitor during the power-on process of the power conversion unit.

[0081] Another embodiment of the present application provides a specific implementation of step S110. The specific process can be found in Figure 4 ( Figure 4 Only in Figure 1 The specific steps include:

[0082] S410: Determine whether the power conversion unit needs to be powered on.

[0083] If the power conversion unit needs to be powered on, S420, S430, and S440 are executed in sequence; if the power conversion unit does not need to be powered on, the control method of the power conversion unit is stopped.

[0084] Generally, if a power-on instruction of a power conversion unit is received, it indicates that the power conversion unit needs to be powered on, and if no power-on instruction of the power conversion unit is received, it indicates that the power conversion unit does not need to be powered on. As for the power-on instruction of the power conversion unit, it is very common in the prior art and will not be described in detail here.

[0085] S420, connecting the first phase AC power to the power conversion unit through the slow start module, and directly connecting the second phase AC power to the power conversion unit.

[0086] It should be noted that how to connect the first phase AC power to the power conversion unit through the slow start module will be described in detail later in conjunction with the connection relationship of the power conversion unit, and will not be repeated here. In addition, directly connecting the second phase AC power to the power conversion unit is the same as directly connecting the third phase AC power to the power conversion unit, and will not be repeated here.

[0087] Since the first phase of the alternating current is connected to the power conversion unit through the slow-start module and the second phase is directly connected to the power conversion unit, it is equivalent to forming a slow-start circuit between the first phase of the alternating current and the second phase of the alternating current, that is, realizing the slow start of the power conversion unit, so the impact current caused on the DC capacitor at this time is relatively small.

[0088] S430: Determine whether the line voltage between the first-phase alternating current and the second-phase alternating current is at a zero-crossing point.

[0089] If the line voltage between the first phase AC power and the second phase AC power is at the zero crossing point, execute S240; if the line voltage between the first phase AC power and the second phase AC power is not at the zero crossing point, stop executing the control method of the power conversion unit.

[0090] It should be noted that how to find the zero-crossing point will be described in detail below and will not be repeated here.

[0091] S440, switching the first phase AC power from being connected to the power conversion unit via the slow-start module to being directly connected to the power conversion unit.

[0092] It should be noted that how to connect the first phase AC power to the power conversion unit through the slow start module will be described in detail later in conjunction with the connection relationship of the power conversion unit, and will not be repeated here. Directly connecting the first phase AC power to the power conversion unit is the same as directly connecting the third phase AC power to the power conversion unit, and will not be repeated here.

[0093] When the line voltage between the first-phase AC power and the second-phase AC power is at a zero point, the first-phase AC power is directly connected to the power conversion unit, which is equivalent to: under zero voltage, the first-phase AC power is directly connected to the power conversion unit. Therefore, when the first-phase AC power is directly connected to the power conversion unit, the current generated on the DC capacitor is smaller, thereby causing a smaller impact current on the DC capacitor.

[0094] It can be understood that there are two stages for charging the DC capacitor. In the first stage, the first phase AC can be connected to the power conversion unit through the slow start module, and the second phase AC can be directly connected to the power conversion unit. In this way, due to the existence of the slow start module, the impact current at the moment of attraction can be reduced, thereby slowly charging the DC capacitor. However, due to the existence of the slow start module, the bus voltage cannot reach the maximum value of the theoretical two-line voltage. In the second stage, when it is detected that the line voltage between the first phase AC and the second phase AC passes through the zero point, the first phase AC no longer passes through the slow start module, but is directly connected to the power conversion unit. In this way, the DC capacitor can continue to be charged, so that the theoretical maximum value of the two-line voltage can be reached after being fully charged.

[0095] In summary, this implementation can further reduce the impact current of the DC capacitor during the power-on process of the power conversion unit.

[0096] Another embodiment of the present application provides another specific implementation of step S110. This implementation further includes the following steps before step S420 in the above implementation:

[0097] S510: Determine whether the line voltage between the first-phase alternating current and the second-phase alternating current is at a zero-crossing point.

[0098] If the line voltage between the first phase AC power and the second phase AC power is at the zero crossing point, S420 is executed; if the line voltage between the first phase AC power and the second phase AC power is not at the zero crossing point, the control method of the power conversion unit is stopped.

[0099] It should be noted that how to find the zero-crossing point will be described in detail below and will not be repeated here.

[0100] In this embodiment, when the line voltage between the first-phase AC power and the second-phase AC power is at a zero-crossing point, the first-phase AC power and the second-phase AC power are connected to the power conversion unit, which is equivalent to: when the first-phase AC power and the second-phase AC power are connected to the power conversion unit at zero voltage, the current generated on the DC capacitor when the first-phase AC power and the second-phase AC power are connected to the power conversion unit is smaller, thereby causing a smaller impact current on the DC capacitor. This implementation can further reduce the impact current of the DC capacitor during the power-on process of the power conversion unit.

[0101] Another embodiment of the present application provides another implementation of the control method of the power conversion unit. The specific process of this implementation can be found in Figure 5 ( Figure 5 Only in Figure 3 As shown in the example, after S140 in the above embodiment, this embodiment further includes the following steps:

[0102] S610, switching the first phase AC power from being connected to the power conversion unit via the slow-start module to being directly connected to the power conversion unit.

[0103] It should be noted that how to connect the first-phase AC power to the power conversion unit through the slow-start module will be described in detail later in conjunction with the connection relationship of the power conversion unit, and will not be repeated here. In addition, directly connecting the first-phase AC power to the power conversion unit is the same as directly connecting the third-phase AC power to the power conversion unit, and will not be repeated here.

[0104] In this embodiment, the first phase AC power is switched from being connected to the power conversion unit through the slow-start module to being directly connected to the power conversion unit, so that the current provided to the power conversion unit by the first phase AC power is consistent with the current provided to the power conversion unit by other phase AC power.

[0105] Another embodiment of the present application provides a method for finding a zero-crossing point, which is specifically described as follows:

[0106] By real-time sampling of the line voltage between the two-phase AC power to be tested, when the line voltage is in the positive half cycle, the sampling value of the line voltage is positive, and when the line voltage is in the negative half cycle, the line voltage is negative. Figure 6 It can be seen that near the zero-crossing moment of the line voltage, Figure 6At the position indicated by arrows 1 and 2 in the figure, the line voltage gradually decreases to zero, then the line voltage becomes negative, and then the line voltage gradually increases in a negative direction. Therefore, it can be seen that the controller can determine the zero-crossing point of the line voltage, that is, the point corresponding to the zero-crossing moment, by the positive and negative changes of two consecutive sampling values. Specifically, if the current sampling value is less than zero and the previous sampling value is greater than zero, it can be determined that the zero-crossing point of the line voltage is between the two sampling points.

[0107] In this embodiment, a method for finding a zero-crossing point is provided, which can avoid the problem of traditional methods requiring the processing of a lot of data, and also avoids the adaptability problem of the phase-locked loop controller, thereby making the detection effect more direct, simple, and efficient, thereby saving the processing time of the controller.

[0108] Another embodiment of the present application provides a power converter, whose specific structure is as follows: Figure 7 ( Figure 7 Only one slow start module 4 is shown as an example, specifically including: a power conversion unit 10, a controller 20, three switching switches 30 and at least one slow start module 40. The connection relationship between the various components is as follows:

[0109] The three-phase interfaces on the input side of the power conversion unit 10 receive three-phase alternating current respectively through three switching switches 30. For example, the first phase interface on the input side of the power conversion unit 10 receives the first phase alternating current through the first switching switch 30, the second phase interface on the input side of the power conversion unit 10 receives the second phase alternating current through the second switching switch 30, and the third phase interface on the input side of the power conversion unit 10 receives the third phase alternating current through the third switching switch 30.

[0110] Optionally, each switching switch 30 may be a mechanical switch or an electronic switch, which is not specifically limited here and may be determined according to specific circumstances, and all are within the protection scope of this application.

[0111] Optionally, the power conversion unit 10 can be a DC / AC conversion unit or an AC / AC conversion unit. In practical applications, this includes but is not limited to this. No specific limitation is made here and it can be determined according to specific circumstances. All of them are within the scope of protection of this application.

[0112] A slow-start module 40 is connected in parallel at both ends of at least one switch 30. For example, following the above example, Figure 7 As shown, only the two ends of the first switch 30 are connected in parallel with the slow-start module 40 .

[0113] The slow start module 40, the power conversion unit 10, and the three switches 30 are all controlled by the controller 20, and the controller 20 is used to execute the control method of the power conversion unit 10 provided in the above embodiment. Generally, the controller 20 needs to have a voltage detection function, that is, it is used to perform voltage detection on the voltage of the three-phase interface on the input side of the power conversion unit 10, that is, to perform voltage detection on the three-phase alternating current.

[0114] The controller 20 is used to control the corresponding switch 30 to close when any phase of AC power is directly connected to the power conversion unit 10. If the switch 30 is connected in parallel with a slow-start module 40, the controller 20 is used to control the slow-start module 40 to form a circuit break. The controller 20 is used to control the slow-start module 40 to form a path and control the switch 30 connected in parallel with the slow-start module 40 to disconnect when any phase of AC power is connected to the power conversion unit 10 through the corresponding slow-start module 40.

[0115] Continuing with the above example, by controlling the first switching switch 30 to be closed and controlling the slow-start modules 40 at both ends of the first switching switch 30 to form an open circuit, the first-phase AC power can be directly connected to the power conversion unit 10. By controlling the second switching switch 30 to be closed, the second-phase AC power can be directly connected to the power conversion unit 10. By controlling the third switching switch 30 to be closed, the third-phase AC power can be directly connected to the power conversion unit 10. By controlling the first switching switch 30 to be disconnected and controlling the slow-start modules 40 at both ends of the first switching switch 30 to form a path, the first-phase AC power can be connected to the power conversion unit 10 through the corresponding slow-start modules 40.

[0116] In practical applications, the input side of the power conversion unit 10 may have a fourth interface as a neutral line interface of the power converter, such as Figure 8 In this case, the controller 20 is also used for voltage detection at the neutral line interface of the power converter.

[0117] In this embodiment, since the controller 20 executes the control method of the power conversion unit 10 provided in the above embodiment, the power converter can reduce the impact current of the DC capacitor during the power-on process of the power conversion unit 10 .

[0118] Another embodiment of the present application provides an implementation of the slow start module 40, which is applicable to each slow start module 40. The specific structure of this implementation is as follows Fig. 9 ( Fig. 9 Only in Figure 8 As shown in the figure, a slow-start resistor Rh is taken as an example, and specifically includes: a slow-start switch 41 and at least one slow-start resistor Rh.

[0119] If the number of the slow-start resistors Rh is greater than 1, all the slow-start resistors Rh are connected in series and in parallel, and the formed branch is connected in series with the slow-start switch 41 , and the two ends of the formed series branch serve as the two ends of the slow-start module 40 .

[0120] If the number of the slow-start resistors Rh is equal to 1, the slow-start resistor Rh is connected in series with the slow-start switch 41, and the two ends of the series branch formed are respectively used as the two ends of the slow-start module 40. Fig. 9 shown.

[0121] The soft-start switch 41 is controlled by the controller 20 .

[0122] Optionally, the slow-start switch 41 may be a mechanical switch or an electronic switch, which is not specifically limited here and may be determined according to specific circumstances, and all are within the protection scope of the present application.

[0123] The above is only a specific implementation of the slow-start module 40. In practical applications, including but not limited to this, no specific limitation is made here, and it can be determined according to specific circumstances, all of which are within the protection scope of this application.

[0124] Another embodiment of the present application provides another implementation of a power converter, and its specific structure is as follows: Fig.10 ( Fig.10 Only in Fig. 9 As shown in the example of a slow-start resistor, this implementation, based on the above implementation, further includes: a voltage detection module 50.

[0125] The voltage detection module 50 is connected to the controller 20 , and is used to detect the voltages of the three-phase interfaces at the input side of the power conversion unit 10 , that is, the voltage detection module 50 is used to perform voltage detection on the three-phase alternating current respectively.

[0126] In the case where the power converter includes the voltage detection module 50 , the controller 20 may not have a voltage detection function, that is, the controller 20 implements voltage detection of the three-phase interface on the input side of the power conversion unit 10 through the voltage detection module 50 .

[0127] It should be noted that the voltage detection module 50 is already very mature in the prior art and will not be described in detail here.

[0128] In this embodiment, since the controller 20 may not have a voltage detection function, the difficulty of selecting the controller 20 is reduced, which is beneficial to the market promotion of the power converter.

[0129] For the above description of the disclosed embodiments, the features recorded in each embodiment in this specification can be replaced or combined with each other, so that professionals in the field can implement or use the present application. The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with a preferred embodiment, it is not used to limit the present invention. Any technician familiar with the field can make many possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A soft start control method for a power conversion unit, characterized in that: The input side of the power conversion unit is used to receive three-phase alternating current; the soft start control method comprises: Using the first-phase alternating current and the second-phase alternating current to charge the DC capacitor in the power conversion unit; If the DC capacitor is fully charged, the first-phase AC power is cut out of the power conversion unit, and the third-phase AC power is directly connected to the power conversion unit; The first-phase alternating current is connected to the power conversion unit through a slow-start module.

2. The slow start control method of the power conversion unit according to claim 1, characterized in that: When the line voltage between the second-phase AC power and the third-phase AC power is at a zero-crossing point, the step of cutting the first-phase AC power out of the power conversion unit and directly connecting the third-phase AC power to the power conversion unit is performed.

3. The slow start control method of the power conversion unit according to claim 1, characterized in that: When the line voltage between the first-phase alternating current and any one of the other two-phase alternating currents is at a zero-crossing point, the step of connecting the first-phase alternating current to the power conversion unit through the slow-start module is performed.

4. The soft start control method of a power conversion unit according to any one of claims 1 to 3, characterized in that: Using the first-phase alternating current and the second-phase alternating current to charge the DC capacitor in the power conversion unit includes: When the power conversion unit needs to be powered on, the first-phase alternating current is connected to the power conversion unit through the slow-start module, and the second-phase alternating current is directly connected to the power conversion unit; When the line voltage between the first-phase alternating current and the second-phase alternating current is at a zero-crossing point, the first-phase alternating current is switched from being connected to the power conversion unit through the slow-start module to being directly connected to the power conversion unit.

5. The slow start control method of the power conversion unit according to claim 4, characterized in that: The step of connecting the first-phase alternating current to the power conversion unit through the slow-start module, and directly connecting the second-phase alternating current to the power conversion unit, comprises: When the line voltage between the first-phase alternating current and the second-phase alternating current is at a zero-crossing point, the first-phase alternating current is connected to the power conversion unit through the slow-start module and the second-phase alternating current is directly connected to the power conversion unit.

6. The soft start control method of a power conversion unit according to any one of claims 1 to 3, characterized in that: The slow start control method further includes: Obtaining a voltage value across the DC capacitor; If the voltage across the DC capacitor reaches the maximum value of the line voltage between the first-phase AC power and the second-phase AC power, it is determined that the DC capacitor is fully charged; If the voltage across the DC capacitor does not reach the maximum value of the line voltage between the first-phase AC power and the second-phase AC power, it is determined that the DC capacitor is not completely charged.

7. The soft start control method of a power conversion unit according to any one of claims 1 to 3, characterized in that: After the step of connecting the first-phase alternating current to the power conversion unit through the slow-start module, the method further includes: The first-phase alternating current is switched from being connected to the power conversion unit via the slow-start module to being directly connected to the power conversion unit.

8. A power converter, characterized in that: include: A power conversion unit, a controller, three switching switches and at least one slow-start module; wherein: The three-phase interface on the input side of the power conversion unit receives three-phase alternating current through the three switching switches respectively, wherein the two ends of at least one of the switching switches are connected in parallel with the slow-start module; The slow-start module, the power conversion unit, and the three switches are all controlled by the controller, and the controller is used to execute the control method of the power conversion unit according to any one of claims 1 to 7.

9. The power converter according to claim 8, characterized in that: The slow-start module comprises: a slow-start switch and at least one slow-start resistor; wherein: The soft-start switch is controlled by the controller; If the number of the slow-start resistors is greater than 1, all the slow-start resistors are connected in series and in parallel, and the formed branch is connected in series with the slow-start switch; If the number of the slow-start resistors is equal to 1, the slow-start resistors are connected in series with the slow-start switches.

10. The power converter according to claim 8, characterized in that: The controller is used to control the corresponding switch to close when any phase of AC power is directly connected to the power conversion unit, and if the switch is connected in parallel with the slow-start module, the controller is used to control the slow-start module connected in parallel with the switch to open the circuit; The controller is used to control the slow-start module to form a path and control the switch connected in parallel with the slow-start module to disconnect when any phase of AC power is connected to the power conversion unit through the corresponding slow-start module.

11. The power converter according to any one of claims 8 to 10, characterized in that: Also includes: Voltage detection module; wherein: The voltage detection module is connected to the controller, and is used to respectively detect the voltages of the three-phase interfaces on the input side of the power conversion unit.

Images