CN108539992B

CN108539992B - Power conversion circuit

Info

Publication number: CN108539992B
Application number: CN201710119480.7A
Authority: CN
Inventors: 李发顺; 卓森庆
Original assignee: Aux Air Conditioning Co Ltd
Current assignee: Aux Air Conditioning Co Ltd
Priority date: 2017-03-02
Filing date: 2017-03-02
Publication date: 2020-07-07
Anticipated expiration: 2037-03-02
Also published as: CN108539992A

Abstract

The invention discloses a power conversion circuit, which comprises a rectification module (1), an inductor (2), a capacitor (3), an inverter circuit (4) and a control module (5), wherein the inductor (2) is connected with an alternating current power supply (9) in series; the inverter circuit (4) is arranged on the capacitor (3) in parallel, and the rectifier module (1) is sequentially connected with the absorption circuit (7) and the absorption capacitor (8) in series; or the capacitor (3) can be arranged in parallel to a series body formed by the absorption circuit (7) and the absorption capacitor (8) in series under the control of the state switch (10), and can also be arranged in parallel to the absorption capacitor (8) under the control of the state switch (10); the control module (5) comprises a DC/DC module (52), the DC/DC module (52) being connected in parallel with the absorption capacitance (8). Has the advantages that: setting a state switch to reduce the impact current at the power-on moment; through the change of the connection state, the voltage on the direct current bus can be kept below a safe value in the power-on and working processes.

Description

Power conversion circuit

Technical Field

The invention relates to the field of air conditioners, in particular to a power conversion circuit.

Background

In the first prior art, as shown in fig. 1, an air conditioner power conversion circuit includes a rectification module 1, an inductor 2, a capacitor 3, an inverter circuit 4 and a control module 5, where the inductor 2 is connected in series with an ac power supply 9, the capacitor 3 is connected in series with the rectification module 1, the inverter circuit 4 is connected in parallel to the capacitor 3, the control module 5 is connected to the inverter circuit 4 and is configured to control the inverter circuit 4 to output a three-phase ac power, the inverter circuit 4 is connected to a motor 6, and the three-phase ac power output by the inverter circuit 4 is configured to drive the motor 6 to operate.

When the motor 6 is suddenly stopped, because the current in the inductor 2 cannot be instantly changed to 0, the current in the inductor 2 still charges the capacitor 3, which may result in an excessively high voltage on the capacitor 3, and a risk of breakdown of the capacitor 3 may easily occur, or also may result in an excessively high current in the inductor 2 due to instability of the connected commercial power, and thus, the capacitor 3 may be overcharged, and the capacitor 3 may be damaged.

In order to overcome the above problem, the second prior art further provides a power conversion circuit, as shown in fig. 9, a diode Ds, a resistor Rs, and a capacitor Cs are connected in series to form a snubber circuit, and the snubber circuit is connected in parallel to a capacitor C, so that when the capacitor C is charged to increase its voltage, the snubber circuit can absorb current, thereby reducing the voltage on the capacitor C. The capacitance Cs is an electrolytic capacitance, and the charging voltage of the electrolytic capacitor Cs is smoothed to be substantially constant. The electrolytic capacitor Cs can be used as a power source for a circuit driven at a fixed voltage. However, at the moment of power-up, the voltage on the capacitor C cannot change suddenly, the power output by the power supply is constant, and the voltage on the capacitor C is small, so that the current is large, a large impact current is formed, and the components such as a diode in the rectifier module are damaged. Secondly, in the power-on process, the voltage gradually increases, and reaches the maximum value when the voltage on the capacitor C increases to be the same as the power supply voltage, and the current can continuously charge the capacitor C, so that the voltage on the capacitor C is too high, and the capacitor 3 is damaged.

Disclosure of Invention

An object of the present invention is to provide a power conversion circuit that reduces an inrush current at the time of power-on and keeps a voltage across a capacitor stable during both power-on and operation.

Specifically, the invention is realized by the following technical scheme:

a power conversion circuit comprises a rectification module, a capacitor, an inverter circuit and a control module; the inverter circuit is arranged on the capacitor in parallel, and is characterized in that the rectifier modules are sequentially connected in parallel on a series body formed by the absorption circuit and the absorption capacitor; the capacitor can be arranged in parallel to a series body formed by the absorption circuit and the absorption capacitor connected in series under the control of the state switch, and can also be arranged in parallel to the absorption capacitor under the control of the state switch; the control module includes a DC/DC module connected in parallel with the absorption capacitance.

Preferably, before the power conversion circuit is powered on, the capacitor is arranged to be connected in parallel to the absorption capacitor under the control of the state switch.

Preferably, the power conversion circuit further includes an inductor connected in series with the ac power source.

Preferably, the power conversion circuit further comprises an inductor, and the inductor is connected in series between the rectifying module and the capacitor.

Preferably, the absorption circuit is a structure in which a diode is connected in series with an absorption resistor, and the diode is configured to enable a current output from the rectification module to pass through the diode.

Preferably, a voltage-reducing resistor is connected in parallel to the absorption capacitor.

Preferably, the absorption circuit is a structure in which a diode, an absorption resistor and a current stabilizing inductor are connected in series.

Preferably, a current limiting resistor is further connected in series on a line connecting the capacitor and the absorption capacitor.

A method for controlling the aforementioned power conversion circuit, the method comprising the steps of:

step 1: the state switch sets the capacitor to be in a state of being connected in parallel to the absorption capacitor;

step 2: the power conversion circuit is powered on to charge the absorption capacitor, the voltage of the absorption capacitor is increased to supply power to the DC/DC module, the DC/DC module works to provide a working power supply for the control device, and the control device works;

and step 3: the control device judges whether the voltage on the capacitor is higher than a preset voltage threshold value, if so, the step 4 is executed;

and 4, step 4: the control device controls the state switching switch to set the capacitor in a state of being connected in parallel to a series body formed by the absorption circuit and the absorption capacitor connected in series.

The invention has the beneficial effects that: (1) by arranging the state change-over switch between the rectifier module and the inverter circuit, the impact current at the power-on moment is reduced, and the safety of the rectifier module is protected; (2) through the change of the connection state between the rectifier module and the inverter circuit, the voltage on the direct current bus can be kept below a safe value in the power-on and working processes.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic diagram of a power conversion circuit according to a first prior art;

fig. 2 is a schematic diagram of a power conversion circuit according to a first embodiment of the present invention;

fig. 2(a) is a schematic structural diagram of a power conversion circuit according to a second embodiment of the present invention;

fig. 2(b) is a schematic diagram of a power conversion circuit according to a third embodiment of the present invention;

FIG. 3 is a schematic diagram of an equivalent circuit structure of FIG. 2 when the terminals K2 and K3 are turned on;

fig. 4 is a schematic diagram of a power conversion circuit according to a fourth embodiment of the present invention;

fig. 5 is a schematic diagram of a power conversion circuit according to a fifth embodiment of the present invention;

fig. 6 is a schematic diagram of a power conversion circuit according to a sixth embodiment of the present invention;

fig. 7 is a schematic diagram of a power conversion circuit according to a seventh embodiment of the present invention;

fig. 8 is a schematic diagram of a power conversion circuit according to an eighth embodiment of the present invention;

fig. 9 is a schematic diagram of a power conversion circuit according to the second prior art.

Description of the reference numerals

To further clarify the structure and connection between the various components of the present invention, the following reference numerals are given and described.

1. A rectification module; 2. an inductor; 3. a capacitor; 4. an inverter circuit; 5. a control module; 51. a control device; 52. a DC/DC module; 53. a PWM generator; 6. a motor; 7. an absorption circuit; 71. a diode; 72. an absorption resistance; 73. a voltage-reducing resistor; 74. a current stabilizing inductor; 75. a current limiting resistor; 8. an absorption capacitance; 9. an alternating current power supply; 10. a state change-over switch; 11. a voltage sensor;

the technical scheme of the invention can be more clearly understood and explained by combining the embodiment of the invention through the reference sign description.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, these information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present invention. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.

The present invention will be described in detail below by way of examples.

In a first embodiment of the present invention, a power conversion circuit, as shown in fig. 2, includes a rectification module 1, a capacitor 3, an inverter circuit 4, and a control module 5; the inverter circuit 4 is arranged on the capacitor 3 in parallel; the rectifier module 1 is connected in parallel to a series body formed by an absorption circuit 7 and an absorption capacitor 8; one end of the capacitor 3 is connected with a zero line end of an alternating current power supply 9, the other end of the capacitor is connected with a state switch 10, as shown in fig. 2, when the state switch 10 conducts a K2 end and a K3 end, the capacitor 3 is connected with the rectifier module 1 in parallel, and when the state switch 10 conducts a K1 end and a K3 end, the capacitor 3 is connected with the absorption capacitor 8 in parallel; the inverter circuit 4 is connected with a motor 6, and the three-phase alternating current output by the inverter circuit 4 is used for driving the motor 6 to operate; the control module 5 comprises a control device 51, a DC/DC module 52 and a PWM generator 53, the DC/DC module 52 is connected in parallel with the absorption capacitor 8, and the DC/DC module 52 is used for driving the control device 51; the control device 51 is connected with the PWM generator 53, and is configured to control the PWM generator 53 to generate a set PWM wave, so as to output a set three-phase alternating current through the PWM control inverter circuit 4, and the control device 51 is further connected with the state switch 10, and is configured to control a conduction condition of the state switch 10; the control device 51 is also connected to a voltage sensor 11 arranged on the bus on which the capacitor 3 is located for obtaining bus voltage information.

The operation of the power conversion circuit shown in fig. 2 is as follows:

s101: before power-on, the K1 end and the K3 end of the state switch 10 are conducted, and the capacitor 3 is disconnected with the rectifying module 1;

s102: after power-on, the current provided by the alternating current power supply 9 is rectified by the rectifying module and flows to the absorption circuit 7 and the absorption capacitor 8, the voltage at two ends of the absorption capacitor 8 is continuously increased, when the voltage at two ends of the absorption capacitor 8 is continuously increased by a certain amount, the DC/DC module 52 works, a stable working power supply is provided for the control device 51, and the control device 51 works;

s103: when the control device 51 detects whether the voltage on the capacitor 3 is higher than the preset voltage threshold through the voltage sensor 11, if so, S104 is executed;

s104: the control device 51 controls the state switching switch 10 to switch to the state where the terminal K2 and the terminal K3 are connected, and at this time, the capacitor 3 is connected to the rectifying module 1, and the rectifying module 1 inputs current to the capacitor 3 directly.

By setting the circuit structure and executing the corresponding control method, on one hand, the impact current generated in the power-on process is absorbed by the absorption circuit 7 and the absorption capacitor 8, so that the damage to components in the rectifier module caused by the overlarge impact current is avoided; on the other hand, when the state change switch 10 is switched to a state where the terminals K2 and K3 are turned on, as shown in fig. 3, the capacitor 3 is connected in parallel to a series connection body formed by the snubber circuit 7 and the snubber capacitor 8, and this state is a normal operation state of the power conversion circuit, in which a ripple current generated when the ac power supply 9 fluctuates in voltage or the power conversion circuit suddenly stops (whether an excessive current generated by the ac power supply 9 fluctuating in voltage or a current generated at the time of the sudden stop) is absorbed by the snubber circuit 7, and the capacitor 3 can be protected from being damaged by the excessive current when the power conversion circuit normally operates.

Further, in order to further obtain a dc voltage with stronger dc performance, in a second embodiment of the present invention, the power conversion circuit further includes an inductor 2, as shown in fig. 2(a), the inductor 2 is connected in series with an ac power supply 9; alternatively, in the third embodiment of the present invention, as shown in fig. 2(b), the inductor 2 is connected in series between the rectifying module 1 and the capacitor 3. In the circuits shown in fig. 2(a) and 2(b), when the aforementioned control method is adopted, since the rectifying circuit 1 and the inductor 2 are not directly connected to the capacitor 3 during power-on, the problem of rise in voltage on the capacitor 3 due to freewheeling in the inductor 2 during power-on is avoided; when the state switch 10 is switched to a state where the terminal K2 and the terminal K3 are connected, when the ac power supply 9 has voltage fluctuation or the power conversion circuit is suddenly stopped, the generated ripple current (whether the current is too high due to the voltage fluctuation of the ac power supply 9 or the current flows through the inductor 2 during the sudden stop) is absorbed by the absorption circuit 7, so that the capacitor 3 can be protected from being damaged by the too high current during the normal operation of the power conversion circuit.

In the fourth embodiment of the present invention, as shown in fig. 4, it is different from the second embodiment in that the snubber circuit 7 is a structure in which a diode 71 and a snubber resistor 72 are connected in series, and the diode 71 is provided so that a current output from the rectifier module can pass through the diode; the absorption resistor 72 is used for dissipating current and can play a role in reducing impact current at the power-on moment, and the diode 71 is used for preventing the current on the branch of the absorption circuit from flowing backwards.

In a fifth embodiment of the present invention, as shown in fig. 5, it is different from the fourth embodiment in that a voltage-reducing resistor 73 is further connected in parallel to the absorption capacitor 8, and the voltage-reducing resistor 73 is used for: when the power conversion circuit is powered down, the voltage on the absorption capacitor 8 can be quickly consumed by the voltage-reducing resistor 73, so that the absorption capacitor 8 is prevented from still having electric energy when the power conversion circuit is powered down. Since the absorption capacitor 8 is used for providing voltage for the DC/DC module 52 on one hand and absorbing undesired current during the power-on process or normal operation of the power conversion circuit on the other hand, the undesired current can be better absorbed during the next power-on operation after the power consumption in the absorption capacitor 8.

In a sixth embodiment of the present invention, as shown in fig. 6, it is different from the fourth embodiment in that the absorption circuit 7 is a structure in which a diode 71, an absorption resistor 72 and a ballast inductor 74 are connected in series; in the power-on process of the power conversion circuit, or when the voltage of the direct current bus is surged, because the current on the current stabilizing inductor 74 can not change suddenly, the current stabilizing inductor 74 presents high impedance, an absorption resistor with larger resistance value is not required to be connected in the absorption circuit, the current stabilizing inductor 74 can restrain the current charged to the absorption capacitor 8 from being overlarge, the damage of devices is avoided, and when the system works normally, the current stabilizing inductor 74 presents low impedance, the loss of the absorption resistor with smaller resistance value is small, and the overall loss of the circuit is reduced.

In the seventh embodiment of the present invention, as shown in fig. 7, the difference from the sixth embodiment is that a voltage-dropping resistor 73 is further connected in parallel to the absorption capacitor 8, which makes the power conversion circuit of the seventh embodiment have all the advantages of the power conversion circuits of the fifth and sixth embodiments.

In the eighth embodiment of the present invention, as shown in fig. 8, the difference from the seventh embodiment is that a current limiting resistor 75 is further provided in series on the line connecting the capacitor 3 and the absorption capacitor 8, and by using the current limiting resistor 75, it is possible to avoid that when the voltages of the capacitor 3 and the absorption capacitor 8 are different, the state change switch 10 conducts a large current generated at the moment of turning on the terminals K1 and K3, and further functions to protect the capacitor 3.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A power conversion circuit comprises a rectification module (1), a capacitor (3), an inverter circuit (4) and a control module (5); the inverter circuit (4) is arranged on the capacitor (3) in parallel, and the rectifier module (1) is connected in parallel on a series body formed by the absorption circuit (7) and the absorption capacitor (8); the capacitor (3) can be arranged in parallel to a series body formed by the absorption circuit (7) and the absorption capacitor (8) in series under the control of the state switch (10), and can also be arranged in parallel to the absorption capacitor (8) under the control of the state switch (10); the control module (5) comprises a DC/DC module (52), the DC/DC module (52) being connected in parallel with the absorption capacitance (8); the conversion method comprises the following steps:

step 1: the capacitor is set to be connected in parallel to the absorption capacitor by the state change-over switch, the K1 end and the K3 end of the state change-over switch (10) are conducted, and the rectifying module (1) is conducted with the inverter circuit (4) through the absorption circuit (7);

and 4, step 4: the control device controls the state switching switch to a state where the K2 terminal and the K3 terminal are conducted, and sets the capacitor to a state of being connected in parallel to a series body formed by the absorption circuit and the absorption capacitor in series.

2. A power conversion circuit according to claim 1, characterized in that the capacitor (3) is arranged in parallel across the absorption capacitance (8) under the control of a state-change switch (10) before power-up of the power conversion circuit.

3. The power conversion circuit according to claim 1, characterized in that the power conversion circuit further comprises an inductor (2), the inductor (2) being connected in series with an alternating current power source (9).

4. The power conversion circuit according to claim 1, further comprising an inductor (2), the inductor (2) being connected in series between the rectifier module (1) and the capacitor (3).

5. The power conversion circuit according to claim 1, wherein the snubber circuit (7) is a structure in which a diode (71) is connected in series with a snubber resistor (72), and the diode (71) is arranged so that a current output from the rectifier module passes through the diode (71).

6. The power conversion circuit according to claim 5, wherein a voltage-reducing resistor (73) is connected in parallel to the absorption capacitor (8).

7. The power conversion circuit according to claim 5, wherein the absorption circuit (7) is a structure in which a diode (71), an absorption resistor (72), and a ballast inductor (74) are connected in series.

8. The power conversion circuit according to claim 7, wherein a voltage-reducing resistor (73) is connected in parallel to the absorption capacitor (8).

9. A power conversion circuit according to claim 8, characterized in that a current limiting resistor (75) is further provided in series in the line connecting the capacitor (3) and the absorption capacitor (8).