Inverter circuit

Abstract

The inverter circuit comprises a rectifier module, a capacitor module and a pre-charging module, the capacitor module is connected between a positive direct current bus and a negative direct current bus of the rectifier module, the pre-charging module is connected between the positive direct current bus and the capacitor module in series, the pre-charging module at least comprises an IGBT module and a PWM controller, and the PWM controller is connected with the capacitor module. And the IGBT module is connected with the PWM controller and is set to be switched on and off according to the control of the PWM controller. A single IGBT module is used for replacing a plurality of original components to form a pre-charging module, so that the pre-charging of a capacitor module is realized; moreover, the PWM controller can be used for controlling the opening time of the IGBT module, thereby achieving the control of the charging current peak value of the capacitor module, and also achieving the control of the charging current peak value of the capacitor module through the adjustment of the reactance module.

Description

Technical Field

[0001] The utility model relates to the field of rectifier inverter circuits, and more specifically, to an inverter circuit. Background Art

[0002] For some rectifier or inverter circuits, the capacitor in the circuit is in a zero voltage state before power is turned on, that is, there is no energy in the capacitor. Then, at the moment of circuit closing, it is equivalent to a direct short circuit, and the current is very large. If such a large current is not limited, it will cause a huge impact on the battery and relay and cause damage. Therefore, the system must be equipped with a pre-charging circuit to reduce the impact current when power is turned on.

[0003] Figure 1 The circuit structure diagram of the pre-charging circuit in the prior art is disclosed. Figure 1 As shown, the pre-charging circuit is a typical first-order RC series circuit. At the beginning, the switch s1 is closed first, and when the capacitor module C is charged to a certain proportion of the target voltage, such as 80%, the switch s2 is closed to bypass the pre-charging resistor R.

[0004] It can be seen that the circuit components required for the above pre-charging circuit are a resistor R and two contactors S1 and S2. It is relatively troublesome to assemble the circuit, and it is impossible to achieve current control of the pre-charging circuit. Utility Model Content

[0005] In view of this, the utility model proposes a new inverter circuit to solve the above problems.

[0006] According to an embodiment of the utility model, an inverter circuit includes a rectifier module, a capacitor module and a pre-charging module, wherein the capacitor module is connected between a positive DC bus and a negative DC bus of the rectifier module, and the pre-charging module is connected in series between the positive DC bus and the capacitor module, wherein the pre-charging module includes at least one IGBT module and one PWM controller, and the IGBT module is connected to the PWM controller and is configured to be switched on and off according to the control of the PWM controller.

[0007] Furthermore, the collector of the IGBT module is connected to the positive DC bus, and the emitter of the IGBT module is connected to the capacitor module.

[0008] Furthermore, the rectifier module includes an AC input end, a reactance module and a switch tube module, the input end of the reactance module is connected to the AC input end, and the output end of the reactance module is connected to the switch tube module.

[0009] Furthermore, the AC input end includes a U-phase input end, a V-phase input end and a W-phase input end, and the reactance module includes a first reactance, a second reactance and a third reactance, wherein the U-phase input end is connected to the first reactance, the V-phase input end is connected to the second reactance, and the W-phase input end is connected to the third reactance.

[0010] Furthermore, the first reactance, the second reactance and the third reactance are adjustable reactances.

[0011] Furthermore, the PWM controller is implemented using an MCU chip.

[0012] Furthermore, it comprises a plurality of the capacitor modules, and one capacitor module is adapted to one IGBT module.

[0013] Furthermore, one of the capacitor modules includes a plurality of electrolytic capacitors.

[0014] According to an inverter circuit of an embodiment of the utility model, a single IGBT module is used to replace the original multiple components to form a pre-charging module to achieve pre-charging of the capacitor module; and the peak value of the charging current of the capacitor module can be controlled by controlling the opening time of the IGBT module through a PWM controller, and the peak value of the charging current of the capacitor module can also be controlled by adjusting the reactance module. Through the inverter circuit of the embodiment of the utility model, the circuit is more concise, and the maximum current of the capacitor module pre-charging circuit can be controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that those skilled in the art will be more aware of the above and other features and advantages of the present invention. In the accompanying drawings:

[0016] Figure 1 A circuit structure diagram of a pre-charging circuit in the prior art;

[0017] Figure 2 It is a structural schematic diagram of an inverter circuit according to an embodiment of the utility model;

[0018] Figure 3 1 is a PWM waveform diagram of an inverter circuit according to an embodiment of the utility model;

[0019] Figure 4 is a diagram showing simulation results of charging current of an inverter circuit according to an embodiment of the utility model;

[0020] The reference numerals are as follows:

[0021] S1, S2 switches

[0022] R Pre-charge resistor

[0023] C capacitor module

[0024] 10 AC input terminal

[0025] 11 First reactance

[0026] 13 Second reactance

[0027] 15Third Reactance

[0028] 20 switch tube module

[0029] 40IGBT modules DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the utility model clearer, the utility model is further described in detail with examples below.

[0031] Figure 2 It is a structural schematic diagram of an inverter circuit according to an embodiment of the utility model;

[0032] like Figure 2 As shown, the inverter circuit includes a rectifier module, a capacitor module C and a pre-charging module, wherein the capacitor module C is connected between the positive DC bus and the negative DC bus of the rectifier module, and the pre-charging module is connected in series between the positive DC bus and the capacitor module C, wherein the pre-charging module includes at least one IGBT module 40 and a PWM controller, and the IGBT module 40 is connected to the PWM controller and is configured to be switched on and off according to the control of the PWM controller.

[0033] Based on this embodiment, in addition to the rectifier module and the capacitor module C for DC charging, the inverter circuit also has a pre-charging module for pre-charging the capacitor module C. The pre-charging module is composed of an IGBT module 40 and a PWM controller (not shown in the drawings). The PWM controller can control the on and off of the IGBT module 40, thereby controlling the pre-charging current.

[0034] According to another embodiment of the present invention, the collector of the IGBT module 40 is connected to the positive DC bus, and the emitter of the IGBT module 40 is connected to the capacitor module C.

[0035] According to another embodiment of the utility model, the rectifier module includes an AC input terminal 10, an inductor module and a switch tube module 20, the input terminal of the inductor module is connected to the AC input terminal 10, and the output terminal of the inductor module is connected to the switch tube module 20, wherein the AC input terminal 10 includes a U-phase input terminal, a V-phase input terminal and a W-phase input terminal, and the inductor module includes a first inductor 11, a second inductor 13 and a third inductor 15, wherein the U-phase input terminal is connected to the first inductor 11, the V-phase input terminal is connected to the second inductor 13, and the W-phase input terminal is connected to the third inductor 15.

[0036] In the above embodiment, specifically, the switch tube module 20 can be a bridge-shaped connection circuit composed of six diodes, so that the inverter circuit of the utility model is suitable for the rectifier module of the three-phase rectifier bridge, and then realizes the control of the current size of the pre-charge of the capacitor module C in this circuit.

[0037] Furthermore, the peak value of the pre-charging current can be reduced by adjusting the inductance values ​​of the first reactor 11 , the second reactor 13 , and the third reactor 15 , or by adjusting the turn-on time of the IGBT module 40 through a PWM controller.

[0038] The peak value of the charging current of the capacitor module C can be calculated according to the formula U=-L di / dt, wherein U is the DC voltage output by the rectifier module, L is the inductance value of the first inductor 11, the second inductor 13 and the third inductor 15, Di is the increased current, and dt is the turn-on time of the IGBT module 40; if it is necessary to reduce the pre-charging current peak, the inductance value L can be increased or the turn-on time dt can be reduced.

[0039] Figure 3 PWM waveform diagram of a circuit according to an embodiment of the utility model; Figure 4 is a diagram showing simulation results of charging current of a circuit according to an embodiment of the utility model;

[0040] like Figure 3 As shown, the on-time of the IGBT module 40 is set to 10us. When the 3AC input terminal 10 is 380V and the inductance of the reactance is 100uH, the DC voltage U output by the rectifier module is 380*1.35=513V. According to the above formula, the pre-charge current peak value Di=u*dt / L=380*1.35*10*10^-6 / 100*10^-6=53A can be calculated. Figure 4 It can be seen that the simulation results of the circuit are consistent with the calculated results.

[0041] According to another embodiment of the present invention, the first reactance 11, the second reactance 13 and the third reactance 15 are adjustable reactances. By adjusting the inductance values ​​of the first reactance 11, the second reactance 13 and the third reactance 15, the value of the inductance value L in the above formula can be increased, thereby achieving the effect of reducing the current peak value.

[0042] According to another embodiment of the present invention, the PWM controller is set as a part of the MCU chip. By controlling the PWM controller to change the frequency and duty cycle of the pulse signal, the value of the on-off time dt of the IGBT module 40 in the above formula can be reduced.

[0043] According to another embodiment of the present invention, the PWM controller is configured to provide a 10 kHz PWM signal to the IGBT module 40. Based on this embodiment, the peak value of the charging current can be effectively reduced by a high switching frequency.

[0044] According to another embodiment of the present invention, a plurality of capacitor modules C are included, and one capacitor module C is adapted to one IGBT module 40. In this way, different inverter circuit requirements can be met as much as possible.

[0045] According to another embodiment of the utility model, the capacitor module C includes multiple electrolytic capacitors. For example, an AC 400V 900KW inverter uses 24 5.8mF electrolytic capacitors, 12 of which are connected in parallel as one group, for a total of two groups. Then the two groups are connected in series, and the total capacitance of the capacitor module C is: 5.8*12 / 2=34.8mF.

[0046] It can be seen that the inverter circuit of the embodiment of the utility model uses a single IGBT module 40 to replace the original multiple components to form a pre-charging module, so as to realize the pre-charging of the capacitor module C; and the peak value of the charging current of the capacitor module C can be controlled by controlling the opening time of the IGBT module 40 by the PWM controller, and the peak value of the charging current of the capacitor module C can also be controlled by adjusting the reactance module. Through the inverter circuit of the embodiment of the utility model, the circuit is more concise, and the maximum current of the pre-charging circuit of the capacitor module C can be controlled.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An inverter circuit, characterized in that: The invention comprises a rectifier module, a capacitor module (C) and a pre-charging module, wherein the capacitor module (C) is connected between a positive DC bus and a negative DC bus of the rectifier module, and the pre-charging module is connected in series between the positive DC bus and the capacitor module (C), wherein the pre-charging module comprises at least an IGBT module (40) and a PWM controller, and the IGBT module (40) is connected to the PWM controller and is configured to be switched on and off according to the control of the PWM controller.

2. The inverter circuit according to claim 1, characterized in that: The collector of the IGBT module (40) is connected to the positive DC bus, and the emitter of the IGBT module (40) is connected to the capacitor module.

3. The inverter circuit according to claim 1 or 2, characterized in that: The rectifier module comprises an AC input end (10), a reactance module and a switch tube module (20), wherein the input end of the reactance module is connected to the AC input end (10), and the output end of the reactance module is connected to the switch tube module (20).

4. The inverter circuit according to claim 3, characterized in that: The AC input terminal (10) comprises a U-phase input terminal, a V-phase input terminal and a W-phase input terminal, and the reactance module comprises a first reactance (11), a second reactance (13) and a third reactance (15), wherein the U-phase input terminal is connected to the first reactance (11), the V-phase input terminal is connected to the second reactance (13), and the W-phase input terminal is connected to the third reactance (15).

5. The inverter circuit according to claim 4, characterized in that: The first reactance (11), the second reactance (13) and the third reactance (15) are adjustable reactances.

6. The inverter circuit according to claim 1, characterized in that: The PWM controller is implemented using an MCU chip.

7. The inverter circuit according to claim 1, characterized in that: It comprises a plurality of capacitor modules, and one capacitor module (C) is adapted to one IGBT module (40).

8. The inverter circuit according to claim 1, characterized in that: One of the capacitor modules (C) includes a plurality of electrolytic capacitors.

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