CN108011506A - A kind of Current limited Control method and system of inverter - Google Patents

Abstract

The present application relates to a current limiting control method and system of an inverter. The method includes obtaining the output current of the inverter; when the output current is greater than or equal to the first current threshold, turning off two main switching tubes; waiting for a delay Turn off the two auxiliary switching tubes after a certain time; when the output current of the inverter is less than the first current threshold, make all the switching tubes work according to the normal switching logic. The system includes an output current acquisition module, a judgment module, a control module and a delay time setting module. The method and system in this application can release the energy of the parasitic capacitance in the freewheeling diode by setting the delay time, which is beneficial to protect the switch tube, and by setting the second current threshold, it can avoid frequent triggering of the first current when overcurrent occurs Threshold, used to protect the inverter.

Description

A current limiting control method and system for an inverter

technical field

The present application relates to the technical field of inverters, and in particular to a current limiting control method and system for inverters.

Background technique

Server power supplies are usually uninterruptible power supplies, and inverters are used in power electronics applications such as uninterruptible power supplies, new energy power generation, and active power filtering. Common inverters include I-type and T-type inverters. See Figure 1. Take the I-type three-level inverter as an example. In Figure 1, Q1 and Q4 are the main switch tubes, Q2 and Q3 are the auxiliary switch tubes, and C1 is the center switch. Bus capacitor, C2 is the negative bus capacitor, C3 is the filter capacitor, D1 and D2 are freewheeling diodes, L is the energy storage inductor, and R is the resistive load. Controlling the current limit of the inverter is an important part of inverter debugging, and the current limit of the inverter can prevent the switching devices from being burned due to overcurrent.

Usually, there are two methods to control the current limit of the inverter. The first method is to directly turn off the drive when the current on the switch tube is too large, and let the current drop naturally, so as to realize the current limit of the inverter. That is, it is equivalent to turning off the four drivers Q1, Q4, Q2, and Q3 in Fig. 1 at the same time. The second method is to turn off the main switch and turn on the auxiliary switch, that is, turn off the current limit of Q1 and Q4 in Figure 1 and turn on Q2 and Q3 at the same time. At this time, the two freewheeling diodes D1 and D2 are turned on. The voltage at point A is clamped to 0, and there is only a single BUS voltage between the positive BUS and point A, and between the negative BUS and point A, that is, only 360V voltage, so the stress of all switch tubes will not be too high.

However, in the current current limiting method, when all the drivers are turned off in the first method, the voltage at point A fluctuates severely, which causes great stress on the auxiliary switch tubes Q2 and Q3. For example: make a timing diagram according to the process of all switching tubes controlling the current of the inverter. In the positive half cycle of the timing diagram, Q1 is on and Q3 is complementary to off, and when Q2 is normally on and Q4 is normally off, the current is positive and the current is limited. Afterwards, all the drivers are pulled down, but due to the individual differences between the switch tubes, all the switch tubes are not turned off at the same time. It may happen that Q2 is cut off first and Q1 is turned off later. At this time, the voltage at point B is limited to +360V. The voltage at point A is clamped to -360V due to the continuous flow of the current. With the addition of interference factors, the voltage between the collector and emitter of the auxiliary switch tube Q2 may withstand a voltage of more than 1000V instantaneously, resulting in the destruction of the auxiliary switch tube Q2. Similarly, if in the negative half cycle of the timing diagram, Q4 is on, Q2 is complementary to off, Q3 is normally on and Q1 is normally off, the current is reversed. After the current limit, Q3 may be turned off first and then Q4. At this time, the auxiliary switch The tube Q3 is momentarily subjected to a voltage above 1000V, which causes the auxiliary switch tube Q3 to be destroyed. In the second method, since the load cast on the inverter includes capacitance, resistance, inductance and various combinations thereof. When the pure filter capacitor load C3 is applied, there is a negative voltage on C3 and the output is at the peak value of the positive half axis when the load is applied, after the filter capacitor load is applied, the voltage in the circuit is pulled to the same direction as the current on the filter capacitor load C3, that is, When the inverter output voltage is pulled reversely. Since the stray capacitance of the diode D1 is much higher than that of the IGBT transistor, when all drivers are suddenly turned off, the voltage generated by the stray capacitance of D1 is all added to Q2. At this time, a large current will be generated on the energy storage inductor L, which will eventually damage the auxiliary switch tube Q2. Similarly, when the pure filter capacitor load C3 is applied, there is a negative and positive voltage on C3 and the output is at the peak value of the negative half-axis at the instant of the load, after C3 is loaded, the voltage generated by the stray capacitance of D2 is all added to Q3, which will eventually be damaged Auxiliary switch tube Q3.

Contents of the invention

In order to overcome the problem in the related art that the switching tube of the inverter will be damaged by the hardware shutdown operation, the present application provides a current limiting control method and system for the inverter.

A current limiting control method of an inverter, which is used in a three-level inverter, and each phase of the three-level inverter includes two main switching tubes and two auxiliary switching tubes, the method includes the following steps :

Obtain the output current of the inverter;

When the output current is greater than or equal to a first current threshold, the two main switch tubes are turned off, and the first current threshold is the mandatory current limiting threshold of the inverter;

After waiting for a delay time, turn off the two auxiliary switch tubes, and the delay time is the time interval between the moment when the two main switch tubes are turned off to the time when the two freewheeling diodes discharge the electricity;

When the output current of the inverter is less than the first current threshold, all the switching tubes are operated according to the normal switching logic.

Optionally, the method also includes:

A second current threshold is introduced in the inverter to limit the output current of the inverter, so that the output duty cycle of the inverter when the current is limited is kept the same as the output duty cycle of the inverter before the current limit Consistent, the second current threshold is smaller than the first current threshold and can drive the load of the inverter;

The output current is compared with the first current threshold and the second current threshold, and a current limiting operation is performed.

Optionally, the method for introducing a second current threshold in the inverter includes:

The second current threshold is written into the IC chip of the inverter as a signal pin, and the signal pin is connected with the main circuit of the inverter.

Optionally, comparing the output current with the first current threshold and the second current threshold to perform a current limiting operation includes the following steps:

Obtain the output current of the inverter;

When the output current is greater than or equal to the first current threshold, turn off the two main switch tubes;

After waiting for a delay time, turn off the two auxiliary switch tubes, and the delay time is the time interval between the moment when the two main switch tubes are turned off to the time when the two freewheeling diodes discharge the electricity;

When the output current of the inverter is greater than or equal to the second current threshold and less than the first current threshold, the output current of the inverter is limited by the second current threshold. At this time, the output current of the inverter is the same as the second The magnitude of the current threshold is equal;

When the output current of the inverter is less than the second current threshold, all the switching tubes are made to work according to the normal switching logic.

Optionally, when the output current of the inverter is less than the second current threshold, making all the switching tubes work according to the normal switching logic includes:

When the output current of the inverter is less than the second current threshold, control the two auxiliary switching tubes to work according to the normal switching logic;

Control the two main switching tubes to work according to the normal switching logic.

Optionally, the second current threshold is the product of the output current and the output crest factor.

A current-limiting control system of an inverter, which is used in a three-level inverter, and each phase of the three-level inverter includes two main switching tubes and two auxiliary switching tubes, wherein the The system includes:

an output current obtaining module, configured to obtain the output current of the inverter;

A judging module, configured to judge the magnitude relationship between the output current and the first current threshold, where the first current threshold is the mandatory current limiting threshold of the inverter;

A control module, configured to turn off the two main switch tubes when the output current is greater than or equal to the first current threshold;

The delay time setting module is used to make the system enter the delay waiting state and maintain a delay time after the two main switch tubes are turned off. the time interval between the moments of venting;

The control module is also used to turn off the two auxiliary switch tubes after waiting for a delay time;

The control module is also used to make all the switching tubes work according to the normal switching logic when the output current of the inverter is lower than the first current threshold.

Optionally, the system also includes:

The second current threshold setting module is used to introduce a second current threshold in the inverter, and the second current threshold is used to limit the output current of the inverter, so that the output current of the inverter when current limiting occurs The duty cycle is consistent with the output duty cycle of the inverter before current limiting, and the second current threshold is smaller than the first current threshold and can drive the load of the inverter.

Optionally, the second current threshold setting module is a signal pin inside the IC chip, and the signal pin is connected to the main circuit of the inverter.

Optionally, the system also includes:

The judging module is also used to judge the magnitude relationship between the output current and the second current threshold;

The control module is also used to control the second current threshold setting module to limit the output current of the inverter when the output current of the inverter is greater than or equal to the second current threshold and less than the first current threshold. The magnitude of the output current of the transformer is equal to the magnitude of the second current threshold;

The control module is also used to make all the switching tubes work according to the normal switching logic when the output current of the inverter is lower than the second current threshold.

The technical solutions provided by the embodiments of the present application may include the following beneficial effects:

The present application provides a current limiting control method of an inverter, which includes obtaining the output current of the inverter; when the output current is greater than or equal to the first current threshold, turning off two main switching tubes; after waiting for a delay time, turning off the two main switches Auxiliary switching tubes, the delay time is the time interval between the time when the two main switching tubes are turned off and the time when the two freewheeling diodes discharge the power; when the output current of the inverter is less than the first current threshold, all switches are activated The tube operates according to normal switching logic. The setting of the delay time in the embodiment of the present application can make the energy of the parasitic capacitance in the two freewheeling diodes of the upper and lower bridge arms be released after the two main switch tubes of the upper and lower bridge arms are turned off, thereby avoiding the two auxiliary switches of the upper and lower bridge arms. The switching tube is blown up due to over-voltage, so the setting of the delay time can effectively protect the inverter and the switching tube. Since the delay time in this application is the time interval between the moment when the two main switch tubes are turned off and the moment when the two freewheeling diodes discharge the power, any load in the inverter will make the parasitic capacitance in the freewheeling tube The energy is released, but the delay time setting is different for different loads. The current limiting control method in the embodiment of the present application also introduces a second current threshold, which is used to limit the output current of the inverter, so that the output duty ratio of the inverter when current limiting occurs is the same as the inverter limit. The output duty cycle before the current flow remains consistent, and the setting of the second current threshold can avoid frequent triggering of the first current threshold used for the inverter's forced current limit when overcurrent occurs, which is beneficial to further protect the inverter, and the second The setting of the current threshold keeps the output duty ratio of the inverter unchanged, which is beneficial to improve the stability of the inverter.

The present application provides a current limiting control system of an inverter, including an output current acquisition module, a judgment module, a control module and a delay time setting module. First, the output current of the inverter is obtained through the output current acquisition module, and then the magnitude relationship between the output current and the first current threshold is judged by the judgment module, and when the output current is greater than or equal to the first current threshold, the two Main switch tube: After closing the two main switch tubes, the system enters the delay waiting state through the delay time setting module and maintains a certain delay time. When the two freewheeling diodes discharge the power, the two auxiliary switches are turned off through the control module Finally, when the judging module judges that the output current of the inverter is less than the first current threshold, the control module makes all the switching tubes work according to the normal switching logic. The setting of the delay time setting module in the embodiment of the present application can make the energy of the parasitic capacitance in the two freewheeling diodes of the upper and lower bridge arms be released after the two main switch tubes of the upper and lower bridge arms are turned off, thereby avoiding the damage of the upper and lower bridge arms. The two auxiliary switch tubes are blown up due to over-voltage, so the setting of the delay time can effectively protect the switch tubes. The current limiting control system in the embodiment of the present application is also provided with a second current threshold setting module. The setting of the second current threshold setting module can avoid frequent triggering of the first current used for forced current limiting of the inverter when an overcurrent occurs. The threshold is used to further protect the performance of the inverter.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description serve to explain the principles of the application.

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, In other words, other drawings can also be obtained from these drawings without paying creative labor.

Fig. 1 is the schematic diagram of the circuit structure of I-type three-level inverter in the prior art;

FIG. 2 is a schematic flowchart of a current limiting control method for an inverter provided in an embodiment of the present application;

FIG. 3 is a schematic flowchart of another inverter current limiting control method provided by the embodiment of the present application;

Fig. 4 is a schematic structural diagram of a current limiting control system of an inverter provided in an embodiment of the present application.

Detailed ways

In order to clearly illustrate the technical characteristics of the present solution, the present application will be described in detail below through specific implementation modes and in conjunction with the accompanying drawings. The following disclosure provides many different embodiments or examples for implementing different structures of the present application. To simplify the disclosure of the present application, components and arrangements of specific examples are described below. Furthermore, the application may repeat reference numbers and/or letters in different instances. This repetition is for the purpose of simplicity and clarity and does not in itself indicate a relationship between the various embodiments and/or arrangements discussed. It should be noted that components illustrated in the figures are not necessarily drawn to scale. Descriptions of well-known components and processing techniques and processes are omitted herein to avoid unnecessarily limiting the application.

Parasitic capacitance generally refers to the capacitance characteristics of inductors, resistors, or chip pins at high frequencies. In fact, a resistor is equivalent to a capacitor, an inductor, and a resistor in series, which is not obvious at low frequencies, but at high frequencies, the equivalent value will increase and cannot be ignored. Parasitic capacitance means that there is no capacitance designed somewhere, but because there is always mutual capacitance between wirings, mutual capacitance seems to be parasitic between wirings, also known as stray capacitance.

In order to better understand the present application, the implementation manner of the present application will be explained in detail below in conjunction with the accompanying drawings.

Embodiment one

Referring to FIG. 2 , FIG. 2 is a schematic flowchart of an inverter current limiting control method provided by an embodiment of the present application. It can be seen from FIG. 2 that the current limiting control method of the inverter in the embodiment of the present application mainly includes the following steps:

S11: Obtain the output current of the inverter.

In this embodiment, the wave-by-wave current limiting is mainly performed by collecting the output current and comparing the output current with the first current threshold. Usually, the current flowing through the switch tube passes through the energy storage inductor, therefore, the current information on the switch tube, that is, the current in the inverter circuit, can be obtained by measuring the current flowing through the energy storage inductor. The output current in the inverter circuit can be measured by a current sensor, such as a Hall current sensor or a power frequency current sensor.

After the output current of the inverter is obtained, the relationship between the current output current of the inverter and the first current threshold is judged, and whether the output current is greater than or equal to the first current threshold is judged. Enter step S12: when the output current is greater than or equal to the first current threshold, turn off the two main switch tubes.

Wherein, the first current threshold is the mandatory current limit threshold of the inverter, that is, the maximum current that the inverter can withstand. When the output current exceeds the first current threshold, the inverter will be burned down. The first current threshold is usually much larger than to the normal output current of the inverter.

This embodiment adopts the current limiting method of first turning off the main switching tube and then closing the auxiliary switching tube. When the output current is greater than or equal to the first current threshold, the current limiting program is entered, and the two main switching tubes are first turned off, so that the inverter circuit The current starts to drop.

After step S12 is executed, go to step S3: after waiting for a delay time, turn off the two auxiliary switch tubes.

Wherein, the delay time is the time interval between the time when the two main switch tubes are turned off and the time when the two freewheeling diodes discharge the electricity. Referring to Figure 1, since the freewheeling diodes D1 and D2 are much larger than the parasitic capacitance on the IGBT (Insulated Gate Bipolar Transistor, insulated gate bipolar transistor) Q1, Q2, Q3 or Q4 during operation, when the two main switches are turned off , due to the existence of parasitic capacitance in the freewheeling diode, there is a large voltage on D1 or D2. In this embodiment, by setting a delay time, the power in the two freewheeling diodes can be released to avoid the auxiliary switching tubes Q2 and Q3 It is blown up due to overvoltage, which is beneficial to protect the inverter. Generally, when the parasitic capacitance in the freewheeling diode is emptied, the voltage in the auxiliary switch tube will be greatly reduced, usually down to about 20% of the rated voltage of the auxiliary switch tube.

To control the delay time, it is possible to measure whether the capacitance in the two freewheeling diodes is zero through instruments such as high-voltage isolation carbon rods. When the capacitance in the two freewheeling diodes is measured to be zero, turn off the two auxiliary switch tubes.

However, this method is rather cumbersome in actual operation, and the method of setting the delay time can be adopted. Since the moment when the two main switch tubes are turned off is the moment when the two freewheeling diodes start to discharge, the delay time is also the discharge time of the two freewheeling diodes, and the general delay time is several microseconds. In actual use, the delay time can be set according to the discharge time of the freewheeling diode and different inverter circuit loads. Generally, in order to ensure that the freewheeling diode is discharged, the delay time can be set to 1.1-1.2 times of the freewheeling diode discharge time.

Step S13 can further reduce the output current in the inverter loop by turning off the two auxiliary switching tubes, and then judge the relationship between the output current and the first current threshold again at this time, and perform step S14: when the output current of the inverter is less than When the first current threshold is reached, all the switching tubes are made to work according to the normal switching logic.

When the output current is less than the first current threshold, the inverter will not be damaged, and the current limiting program ends, so that all the switching tubes work according to the normal switching logic. That is, after the current limiting is over, firstly control the two auxiliary switching tubes to work according to the normal switching logic; then control the two main switching tubes to work according to the normal switching logic. Since the parasitic capacitors in the two auxiliary switch tubes have been discharged at this time, when the current limiting ends and the normal switching logic is restored, the auxiliary switch tube and the main switch tube can be turned on directly without causing damage to the circuit.

The so-called normal switching logic is that the main switch tube and the auxiliary switch tube are turned on and off according to the sine wave timing diagram before current limiting, that is, in the positive half cycle of the timing diagram, the main switch tube of the upper bridge arm is turned on and the auxiliary switch tube of the lower bridge arm is turned on. The switching tubes are complementary and turned off, the auxiliary switching tube of the upper bridge arm is normally on and the main switching tube of the lower bridge arm is normally off, and the current is in the positive direction; in the negative half cycle of the timing diagram, the main switching tube of the lower bridge arm is turned on and the auxiliary switching tube of the upper bridge arm is complementary When it is turned off, the auxiliary switch tube of the lower bridge arm is normally on and the main switch tube of the upper bridge arm is normally off, and the current is in the negative direction.

Embodiment two

Referring to FIG. 3 on the basis of the embodiment shown in FIG. 2 , FIG. 3 is a schematic flowchart of another inverter current limiting control method provided by the embodiment of the present application.

In this embodiment, a second current threshold is introduced in the inverter, which is used to limit the output current of the inverter, so that the output duty cycle of the inverter when current limiting occurs is the same as the output duty cycle of the inverter before current limiting. Keep the duty ratio consistent, and then compare the output current with the first current threshold and the second current threshold to perform current limiting operation. Wherein, the second current threshold is smaller than the first current threshold and can drive the load of the inverter. The introduction of the second current threshold can avoid frequent triggering of the first current threshold when the inverter is overcurrent, which is beneficial to further protect the inverter. Moreover, the introduction of the second current threshold can keep the output duty ratio of the inverter unchanged, thereby improving the stability of the inverter and protecting the inverter. In this embodiment, by introducing the second current threshold, the output current of the inverter plus the load current feed-forward is used as the current loop setting, which is a supplement to the current limiting method of the first current threshold.

Further, in the embodiment of the present application, the following method can be adopted to introduce the second current threshold: write the second current threshold as a signal pin into the IC chip of the inverter, and connect the signal pin to the main circuit connection.

It can be seen from FIG. 3 that the current limiting control method of the inverter in this embodiment mainly includes the following steps:

S21: Obtain the output current of the inverter.

S22: When the output current is greater than or equal to the first current threshold, turn off the two main switch tubes.

S23: After waiting for a delay time, turn off the two auxiliary switch tubes, and the delay time is the time interval between the time when the two main switch tubes are turned off and the time when the two freewheeling diodes are discharged.

The methods in the above steps S21-S23 have been described in detail in Embodiment 1 shown in FIG. 2 , and will not be repeated here.

After step S23 is executed, the relationship between the output current and the second current threshold and the first current threshold is judged, and step S24 and step S25 are executed respectively according to the relationship between the output current and the second current threshold and the first current threshold.

Step S24: When the output current of the inverter is greater than or equal to the second current threshold and less than the first current threshold, the output current of the inverter is limited by the second current threshold. At this time, the output current of the inverter is equal to the magnitude of the second current threshold.

S25: When the output current of the inverter is less than the second current threshold, make all the switching tubes work according to the normal switching logic.

In the above steps S24-S25, the output current of the inverter is further divided into two situations that are lower than the first current threshold. When the output current of the inverter is greater than or equal to the second current threshold and less than the first current threshold, the output current of the inverter is limited by the second current threshold. At this time, the output current of the inverter is the same as the second The magnitudes of the current thresholds are equal. That is, after turning off the main switching tube and turning off the auxiliary switching tube to limit the current of the inverter, the output current of the inverter will gradually decrease. When the output current of the inverter reaches the second current threshold and is less than the first current threshold , in order to ensure that the output duty ratio of the inverter remains unchanged, the inverter is clipped without triggering the first current threshold again. When the output current of the inverter decreases to less than the second current threshold, all the switching tubes are made to work according to the normal switching logic.

In this embodiment, the second current threshold is smaller than the first current threshold, but if the second current threshold can drive the load of the inverter, it can be understood that the second current threshold is slightly smaller than the first current threshold. The inventors have concluded through a large number of experiments that the second current threshold is more appropriate when the product of the output current and the output crest factor is used. Generally, the output crest factor is 3. The parameter setting of the second current threshold can not only ensure that the size of the second current threshold can drive the inverter load, but also effectively limit the output current through the second current threshold in time to ensure that the inverter in the current limiting program The output duty cycle of the inverter is consistent with the output duty cycle of the inverter in normal logic, which is beneficial to improve the stability of the inverter.

For parts not described in detail in this embodiment, reference may be made to Embodiment 1 shown in FIG. 2 , and the two may refer to each other, and will not be described in detail here.

Referring to FIG. 4 , FIG. 4 shows a schematic structural diagram of an inverter current limiting control system provided by an embodiment of the present application. It can be seen from Fig. 4 that a current limiting control system of an inverter provided by the present application mainly includes four parts: an output current acquisition module, a judgment module, a control module and a delay time setting module. Wherein, the output current obtaining module is used to obtain the output current of the inverter; the judging module is used to judge the magnitude relationship between the output current and the first current threshold; the control module is used for when the output current is greater than or equal to the first current threshold, Turn off the two main switching tubes, and turn off the two auxiliary switching tubes after waiting for a delay time, and, when the output current of the inverter is less than the first current threshold, make all the switching tubes work according to the normal switching logic; the delay time The setting module is used to make the system enter the delay waiting state and maintain a delay time after the two main switch tubes are turned off. The delay time is from the moment when the two main switch tubes are turned off to the time when the two freewheeling diodes discharge the power time interval between.

Wherein, the output current acquisition module may use a current sensor, such as a Hall current sensor or a power frequency current sensor. The judgment module can use a comparator, the control module can use a CPU chip, and the delay time setting module can use a timer.

Further, the current limiting control system of the inverter in the embodiment of the present application further includes a second current threshold setting module, configured to introduce a second current threshold into the inverter. Wherein, the second current threshold is used to limit the output current of the inverter, so that the output duty cycle of the inverter when the current limit occurs is consistent with the output duty cycle of the inverter before the current limit, and the second current The threshold is less than the first current threshold and capable of driving a load of the inverter.

Specifically, the second current threshold setting module may be a signal pin inside the IC chip, and the signal pin is connected to the main circuit of the inverter.

Matching with the second current threshold setting module, in the current limiting control system of the inverter in the embodiment of the present application: the judging module is also used to judge the magnitude relationship between the output current and the second current threshold; the control module also uses When the output current of the inverter is greater than or equal to the second current threshold and less than the first current threshold, the second current threshold setting module is controlled to limit the output current of the inverter, and, when the output current of the inverter When it is less than the second current threshold, all the switch tubes are made to work according to the normal switch logic.

The setting of the delay time setting module in the embodiment of the present application can make the energy of the parasitic capacitance in the two freewheeling diodes be released after the two main switch tubes of the upper and lower bridge arms are turned off, thereby preventing the two auxiliary switch tubes from being overwhelmed by The high voltage will blow up, so the setting of the delay time can effectively protect the switch tube. The setting of the second current threshold setting module can avoid frequent triggering of the first current threshold used for the forced current limit of the inverter when overcurrent occurs, which is beneficial to further protect the performance of the inverter, and the setting of the second current threshold module The output duty ratio of the inverter can be kept constant, which is beneficial to improve the stability of the inverter.

The working principle and working method of the current limiting control system of the inverter in the embodiment of the present application have been described in detail in Embodiment 1 shown in FIG. 2 and Embodiment 2 shown in FIG. 3 , and will not be repeated here.

The above are only optional implementations of the present application. For those of ordinary skill in the art, without departing from the principle of the present application, some improvements and modifications can also be made, and these improvements and modifications are also considered as protection scope of this application.

Claims (10)

1. a kind of Current limited Control method of inverter, for three-level inverter, and each phase includes two in three-level inverter A main switch and two auxiliary switches, it is characterized in that, include the following steps：

Obtain the output current of inverter；

When the output current is greater than or equal to the first current threshold, two main switches, first current threshold are closed Current limit threshold is forced for inverter；

After waiting a time delay, two auxiliary switches are closed, at the time of the time delay is closes two main switches Time interval between at the time of electricity is vented to two fly-wheel diodes；

When the output current of inverter is less than the first current threshold, all switching tubes are made to work according to normal switching logic.

2. a kind of Current limited Control method of inverter as claimed in claim 1, it is characterized in that, the method further includes：

The second current threshold is introduced in inverter, for carrying out amplitude limit to the output current of inverter, limits inverter Output duty cycle during stream is consistent with the output duty cycle before inverter current limliting, and second current threshold is less than the first electricity Flow threshold value and the load of inverter can be driven；

By the output current compared with first current threshold, the second current threshold, current-limiting operation is carried out.

3. a kind of Current limited Control method of inverter as claimed in claim 2, it is characterized in that, it is described that the is introduced in inverter The method of two current thresholds, including：

Using the second current threshold as in the IC chip of signal pins write-in inverter, and by the signal pins and inversion The main circuit connection of device.

4. a kind of Current limited Control method of inverter as described in claim 2, it is characterized in that, by the output current and institute State the first current threshold, the second current threshold is compared, carry out current-limiting operation, include the following steps：

Obtain the output current of inverter；

When the output current is greater than or equal to the first current threshold, two main switches are closed；

After waiting a time delay, two auxiliary switches are closed, at the time of the time delay is closes two main switches Time interval between at the time of electricity is vented to two fly-wheel diodes；

When the output current of inverter is greater than or equal to the second current threshold and is less than the first current threshold, pass through the second electric current Threshold value carries out amplitude limit to the output current of inverter, at this time the output current size of inverter and the size phase of the second current threshold Deng；

When the output current of inverter is less than the second current threshold, all switching tubes are made to work according to normal switching logic.

5. a kind of Current limited Control method of inverter as claimed in claim 4, it is characterized in that, it is described when the output electricity of inverter When stream is less than the second current threshold, all switching tubes are made to work according to normal switching logic, including：

When the output current of inverter is less than the second current threshold, two auxiliary switches of control are according to normal switching logic Work；

Two main switches of control work according to normal switching logic.

6. a kind of Current limited Control system of inverter as described in any one in claim 2-5, it is characterized in that, described second Current threshold is output current and the product for exporting crest factor.

7. a kind of Current limited Control system of inverter, for three-level inverter, and each phase includes two in three-level inverter A main switch and two auxiliary switches, it is characterized in that, the system comprises：

Output current acquisition module, for obtaining the output current of inverter；

Judgment module, for judging the magnitude relationship between output current and the first current threshold, first current threshold is Inverter forces current limit threshold；

Control module, for when output current is greater than or equal to the first current threshold, closing two main switches；

Time delay setting module, after closing two main switches, makes system enter delay wait state and maintains one to prolong The slow time, the time delay for close two main switches at the time of to two fly-wheel diodes electricity is vented at the time of it Between time interval；

The control module is additionally operable to after waiting a time delay, closes two auxiliary switches；

The control module is additionally operable to, when the output current of inverter is less than the first current threshold, make all switching tubes according to just Normal switching logic work.

8. a kind of Current limited Control system of inverter as claimed in claim 7, it is characterized in that, the system also includes：

Second current threshold setup module, for introducing the second current threshold in inverter, second current threshold is used for Amplitude limit is carried out to the output current of inverter, output duty cycle when making the inverter occur current limliting and the output before inverter current limliting Duty cycle is consistent, and second current threshold is less than the first current threshold and can drive the load of inverter.

9. a kind of Current limited Control system of inverter as claimed in claim 8, it is characterized in that, second current threshold is set Module is a signal pins inside IC chip, and the main circuit of the signal pins and inverter connects.

10. a kind of Current limited Control system of inverter as claimed in claim 8, it is characterized in that, the system also includes：

The judgment module is additionally operable to judge the magnitude relationship between output current and the second current threshold；

The control module is additionally operable to when the output current of inverter is greater than or equal to the second current threshold and is less than the first electric current During threshold value, the second current threshold setup module of control carries out amplitude limit to the output current of inverter, at this time the output electricity of inverter Stream size is equal in magnitude with the second current threshold；

The control module is additionally operable to, when the output current of inverter is less than the second current threshold, make all switching tubes according to just Normal switching logic work.