CN114865904A

CN114865904A - Soft start control method of power unit, converter and equipment

Info

Publication number: CN114865904A
Application number: CN202210681232.2A
Authority: CN
Inventors: 孙运杰; 王凯龙; 张亚刚
Original assignee: Xian Linchr New Energy Technology Co Ltd
Current assignee: Xian Linchr New Energy Technology Co Ltd
Priority date: 2022-06-15
Filing date: 2022-06-15
Publication date: 2022-08-05

Abstract

The embodiment of the invention provides a soft start control method of a power unit, the power unit, a converter and equipment, relates to the technical field of power electronics, and is applied to a controller in the power unit, wherein the power unit also comprises a soft start contactor and a main loop breaker, and the method comprises the following steps: acquiring a first voltage output by a power supply and a second voltage at a preset position of an output end of a main circuit breaker; if the first voltage meets the preset power supply condition, controlling the soft start contactor to be closed; under the condition that the soft start contactor is closed, if the voltage difference between the first voltage and the second voltage meets a preset soft start condition, controlling the main loop circuit breaker to be closed and controlling the soft start contactor to be opened; and if the first voltage does not meet the preset power supply condition, controlling the soft start contactor and the main loop circuit breaker to be disconnected. By adopting the invention, the reliability and stability of the soft start control can be improved.

Description

Soft start control method of power unit, converter and equipment

Technical Field

The invention relates to the technical field of power electronics, in particular to a soft start control method of a power unit, the power unit, a converter and equipment.

Background

In the soft start, actually, when the circuit is started, the output voltage is controlled to slowly rise, the starting voltage is limited, and the starting overcharge is avoided. A reasonable soft start control scheme is one of the necessary ways to improve the reliability of the circuit.

However, the existing soft start control method cannot adopt an automatic exit mechanism for the fault problem in the soft start process, and cannot automatically exit after the soft start is finished.

The improper soft start control can cause the circuit to generate larger current impact, thereby damaging power devices in the circuit, influencing the dynamic characteristics of the whole circuit and seriously influencing the safety and reliability of the whole circuit.

Disclosure of Invention

The embodiment of the invention provides a soft start control method of a power unit, the power unit, a converter and equipment, which can improve the reliability and stability of soft start control.

In a first aspect, the present invention provides a soft start control method for a power unit, which is applied to a controller in the power unit, wherein the power unit further includes a soft start contactor and a main circuit breaker, and the method includes:

acquiring a first voltage output by a power supply and a second voltage at a preset position of an output end of the main circuit breaker;

if the first voltage meets a preset power supply condition, controlling the soft start contactor to be closed;

under the condition that the soft start contactor is closed, if the voltage difference between the first voltage and the second voltage meets a preset soft start condition, controlling the main circuit breaker to be closed and controlling the soft start contactor to be opened;

and if the first voltage does not meet the preset power supply condition, controlling the soft start contactor and the main circuit breaker to be disconnected.

Optionally, before controlling the soft-start contactor to be closed if the first voltage meets a preset power supply condition, the method further includes:

if the first voltage is greater than the preset power supply voltage and an input closing instruction is received, determining that the first voltage meets the preset power supply condition;

and if the first voltage is less than or equal to the preset power supply voltage, determining that the first voltage does not meet the preset power supply condition.

Optionally, if a voltage difference between the first voltage and the second voltage meets a preset soft start condition, the method further includes, before controlling the main circuit breaker to be closed and controlling the soft start contactor to be opened, the method further includes:

if the absolute value of the voltage difference is smaller than the preset voltage difference threshold, determining that the voltage difference meets the preset soft start condition;

and if the absolute value of the voltage difference is greater than or equal to the preset voltage difference threshold value, determining that the voltage difference does not meet the preset soft start condition.

Optionally, the controlling the main circuit breaker to close and the soft start contactor to open includes:

controlling the main circuit breaker to close;

detecting a feedback state of the main circuit breaker;

and if the feedback state of the main loop circuit breaker is a closed state, controlling the soft start contactor to be switched off.

Optionally, the method further comprises:

if the feedback states of the main circuit breaker are all off states within a first preset time range from the first time, determining that the main circuit breaker has a fault; wherein the first time is a time for controlling the main circuit breaker to close.

Optionally, the method further comprises:

if the voltage difference within a second preset time range from the second time does not meet the preset soft start condition, determining that a soft start overtime fault exists; and the second time is the time for controlling the closing of the soft start contactor.

In a second aspect, an embodiment of the present invention further provides a power unit, including: the system comprises a controller, a soft start contactor and a main circuit breaker;

a first detection end of the controller is connected between a power supply and an input end of the main circuit breaker so as to detect a first voltage output by the power supply; the soft start contactor is connected in parallel between the input end and the output end of the main circuit breaker;

a second detection end of the controller is connected with a preset position on a current path of the output end of the main circuit breaker so as to detect a second voltage at the preset position;

the controller is further connected with a control end of the soft start contactor and a control end of the main circuit breaker, and the controller is used for executing the soft start control method in any one of the first aspect.

Optionally, the power unit further comprises:

and the resistor is connected in series with the soft start contactor and then is arranged between the input end and the output end of the main circuit breaker in parallel.

In a third aspect, an embodiment of the present invention further provides a converter, including: the power unit, the transformer, and the ac/dc conversion unit according to any one of the second aspects;

the output end of the main circuit breaker is connected with the alternating current end of the alternating current-direct current conversion unit through the transformer, the controller is connected with the alternating current end of the alternating current-direct current conversion unit, and the preset position on the current path is the alternating current end of the alternating current-direct current conversion unit.

In a fourth aspect, an embodiment of the present invention further provides a microgrid control device, where the microgrid control device includes the converter described in the fourth aspect, a controller in the microgrid control device is configured to execute the soft start control method for the power unit described in any one of the first aspects, and the controller is a controller in the power unit included in the converter.

Compared with the prior art, according to the soft start control method of the power unit, the converter and the equipment provided by the embodiment of the invention, the soft start contactor is controlled to be closed when the acquired first voltage of the output of the power supply meets the preset power supply condition, and then the main loop circuit breaker is controlled to be closed and the soft start contactor is controlled to be opened when the difference between the first voltage and the second voltage at the preset position of the output end of the main loop circuit breaker meets the soft start condition, and the soft start contactor and the main loop circuit breaker are controlled to be opened when the first voltage does not meet the preset power supply condition, so that the soft start control of the power unit is completed. By the mode, the switching state of the soft start contactor can be controlled in the power unit according to the power supply condition, the switching states of the main loop circuit breaker and the soft start contactor can be respectively controlled according to the soft start condition in the soft start process, the power unit can judge and control abnormal conditions in the soft start process, the situation that the power unit continuously operates under the condition that the power supply condition is not met to cause that a circuit bears larger impact voltage is avoided, the situation that devices of the power unit continuously input under the condition that the soft start condition is not met to cause damage due to overheating of the circuit is also avoided, and the power unit can run more safely and reliably by using the judging mechanism.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

Fig. 1 is a schematic structural diagram of a power unit according to the present invention;

FIG. 2 is a schematic diagram of another power cell according to the present invention;

fig. 3 is a schematic flowchart of a soft start control method of a power unit according to the present invention;

fig. 4 is a schematic flow chart illustrating a power supply condition determination in a soft start control method of a power unit according to the present invention;

fig. 5 is a schematic flowchart illustrating a soft start condition determination process in a soft start control method of a power unit according to the present invention;

fig. 6 is a schematic flow chart illustrating a main circuit breaker and a soft start contactor controlled in a soft start control method of a power unit according to the present invention;

FIG. 7 is a schematic flow chart illustrating another method for controlling soft-start of a power unit according to the present invention;

fig. 8 is a schematic structural diagram of a current transformer according to the present invention;

fig. 9 is a schematic structural diagram of another current transformer provided by the present invention;

fig. 10 is a schematic structural diagram of another current transformer provided by the present invention;

fig. 11 is a schematic structural diagram of another current transformer provided by the present invention;

fig. 12 is a schematic structural diagram of a microgrid control device according to the present invention;

fig. 13 is a schematic diagram of a soft start control device of a power unit according to the present invention.

Icon: 1, a power unit; 2, a current transformer; 11, a controller; 12, soft starting the contactor; 13, an alternating current circuit breaker; 14, a resistor; 15, a transformer; 16, an AC-DC conversion unit; 17, an AC-DC converter; 18, a direct current breaker; and 3, controlling equipment by the micro-grid.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

Before explaining the present invention in detail, an application scenario of the present invention will be described.

For power cells, especially for high power, direct start-up results in large inrush currents, inrush torques and large grid voltage drops. The surge current generates extremely high instantaneous voltage in the power unit to destroy the power unit, and the service life of the power unit is shortened. Particularly in the practical application of the power unit, the impact current can also cause instantaneous power grid voltage dip to cause undervoltage trip protection with other equipment of the power grid, so that the production is interrupted and the factory benefit is reduced. Therefore, in order to ensure normal start of the power unit, reduce the failure rate and improve the circuit reliability, the power unit is usually soft-started.

However, the existing soft start technology has a plurality of defects. For example, the existing soft start control cannot be actively exited when the start fails, or cannot be actively exited after the soft start is completed, so that the soft start circuit is put into use for a long time, and not only is the electronic device damaged to a certain extent, but also the use risk of the power grid system still exists.

Based on the above, the invention provides a soft start control method of a power unit, the power unit, a converter and a microgrid control device, wherein the power unit is subjected to fault judgment in the soft start process and is timely disconnected, and the power unit is timely quitted from the soft start mechanism after the soft start is finished, so that the power unit avoids impact current in use, protects power electronic devices, and enhances the safety and reliability of the power unit.

Before describing the method for controlling the soft start of the power unit provided by the embodiment of the present invention, the power unit to which the method for controlling the soft start of the power unit is applied will be explained with reference to the drawings. Fig. 1 is a schematic structural diagram of a power unit provided in the present invention, and as shown in fig. 1, the power unit 1 includes: the system comprises a controller 11, a soft start contactor 12 and a main circuit breaker 13; wherein, a first detection end of the controller 11 is connected between the power supply and the input end of the main circuit breaker 13 to detect a first voltage output by the power supply; a soft start contactor 12 is also connected in parallel between the input end and the output end of the main circuit breaker 13; a second detection terminal of the controller 11 is connected to a preset position on a current path of the output terminal of the main circuit breaker 13 to detect a second voltage at the preset position.

In the present embodiment, the controller 11 performs detection of the first voltage and the second voltage through two detection ports. In one possible implementation, the power unit may further include: an electricity meter; wherein the meter may be connected between the power source and the input of the main circuit breaker 13 to detect a first voltage output by the power source, the first voltage detected by the meter may be transmitted to the controller 11 through the communication connection. In another possible implementation manner, the power unit may further include: and the measuring chip detects the first voltage and the second voltage through a detection port of the measuring chip, and then the controller 11 receives the detected first voltage and second voltage through communication interaction between the measuring chip and the controller 11. Optionally, the power unit may further include: the voltage sampling circuit is connected to two detection ports of the controller 11, so that the controller 11 obtains a first voltage and a second voltage. Optionally, the power unit may further include: the voltage sensor, controller 11 obtains first voltage and second voltage through connecting two voltage sensors at two detection ports, and this application does not limit the way that this controller 11 obtains first voltage and second voltage.

The controller 11 is further connected to a control end of the soft start contactor 12 and a control end of the main circuit breaker 13, so that the soft start contactor 12 is controlled to be closed when the first voltage meets a preset power supply condition, the soft start contactor 12 is controlled to be opened when the voltage difference between the first voltage and the second voltage meets the soft start condition, the main circuit breaker 13 is controlled to be closed, and the soft start contactor 12 and the main circuit breaker 13 are controlled to be opened when the first voltage does not meet the preset power supply condition.

Alternatively, the controller 11 controls the soft start contactor 12 and the main circuit breaker 13 to be closed or opened by opening and closing the output relay coil; meanwhile, the soft start contactor 12 and the main circuit breaker 13 output a closed or open state through a dry contact and return to the controller 11, so that crosstalk can be prevented, and the smoothness of an information transmission channel can be ensured.

Alternatively, in the power unit 1, the power supply may be an alternating current power supply, for example, an alternating current power supply that outputs three-phase alternating current power, and may also be a direct current power supply.

After the soft start contactor 12 completes the soft start control, the main circuit breaker 13 is closed and the soft start contactor 12 is opened, and then the main circuit of the power unit 1 is electrified.

In the embodiment, the soft start control is performed on the power unit, so that the influence of the impact current in the circuit is reduced, the power unit can be started smoothly, the service life of an electronic device is prolonged, and the safety of the power unit is protected.

On the basis of the above embodiments, the present invention also provides a possible implementation manner of the power unit. Fig. 2 is a schematic structural diagram of another power unit provided in the present invention. As shown in fig. 2, the power unit 1 further includes: the resistor 14, the resistor 14 and the soft start contactor 12 are connected in series and then arranged in parallel between the input end and the output end of the main circuit breaker 13.

Specifically, the resistor 14 may be formed by a super capacitor, and the soft start contactor 12 is connected in series with the resistor, so that the super capacitor is used in the circuit to maintain the power failure, and if an abnormal power failure occurs in the circuit, the abnormal condition of the circuit may be determined for a certain time, and a circuit fault caused by the abnormal power failure is avoided.

In the embodiment, the power failure is kept in the circuit by connecting the soft start contactor with the resistor in series, so that a certain time is provided for an operator to judge the abnormality, the problem that the circuit fault occurs when the electronic device is jacked to jump when the power unit is abnormally powered down is prevented, and the circuit safety is guaranteed.

The following describes an exemplary soft-start control method for a power unit according to an embodiment of the present invention with reference to the drawings. Fig. 3 is a schematic flowchart of a soft-start control method of a power unit according to the present invention. As shown in fig. 3, the soft-start control method of the power unit is applied to the controller 11 in any one of the power units in the foregoing embodiments, and the method includes:

s110, acquiring a first voltage output by a power supply and a second voltage at a preset position of an output end of the main circuit breaker.

In the power unit 1, a first detection terminal of the controller 11 is connected between the power supply and the input terminal of the main circuit breaker 13 to detect a first voltage output from the power supply; a second detection terminal of the controller 11 is connected to a preset position on a current path of the output terminal of the main circuit breaker 13 to detect a second voltage at the preset position. In the present embodiment, the controller 11 performs detection of the first voltage and the second voltage through two detection ports. Alternatively, in this embodiment, the power supply may be a three-phase alternating current or a direct current.

When the power supply is direct current, the soft start control method of the power unit is to control a direct current soft start loop, at the moment, the soft start contactor 12 is a direct current contactor, the main loop circuit breaker 13 is a direct current circuit breaker, and the influence of impact current generated in the direct current electrifying moment on the direct current power supply is avoided through the soft start control method provided by the application. If the power supply is direct current, the first voltage is the direct current U output by the power supply _dc1 (ii) a The second voltage is the direct current U at a predetermined position on the direct current path at the output of the main circuit breaker 13 _dc2 。

When the power supply is alternating current, the soft start control method of the power unit is to control an alternating current soft start loop, at the moment, the soft start contactor 12 is an alternating current contactor, the main loop circuit breaker 13 is an alternating current circuit breaker, and through the soft start control method provided by the application, the impact current generated in the moment of electrifying the alternating current is prevented from influencing the alternating currentThe influence of the grid. If the power supply is alternating current, the first voltage is the maximum value U of the effective value of the three-phase alternating current output by the power supply at the moment _grid (ii) a The second voltage is the maximum value U of the effective value of the alternating current at a predetermined position on the alternating current path at the output of the main circuit breaker 13 _abc . In the following embodiments of the present application, the power supply is used as ac power for explanation, and the soft start control method when the power supply is dc power is the same as that described above, and no additional details are described.

And S120, if the first voltage meets the preset power supply condition, controlling the soft start contactor to be closed.

When the power supply is alternating current, the preset power supply condition is the preset alternating current power supply condition.

In the present embodiment, in order to avoid the abnormal condition of the circuit voltage, it is necessary to vary the first voltage U according to the circuit voltage _grid And judging whether the preset alternating current power supply condition is met. And if the preset alternating current power supply condition is met, controlling the soft start contactor 12 to be closed.

If U is _grid And if the preset alternating current power supply condition is met, controlling the soft start contactor 12 to be closed. In one possible implementation, at U _grid After the preset alternating current power supply condition is met, whether an alternating current closing instruction exists or not needs to be judged, wherein the alternating current closing instruction is an externally input instruction and can be manually controlled; when the controller 11 receives an ac closing instruction, the soft start contactor 12 may be controlled to be closed.

And S130, under the condition that the soft start contactor is closed, if the voltage difference between the first voltage and the second voltage meets a preset soft start condition, closing the main loop circuit breaker and opening the soft start contactor.

After the soft start contactor is closed, that is, the first voltage meets the preset power supply condition, whether the soft start condition is met or not needs to be judged according to the voltage difference between the first alternating voltage and the second alternating voltage. In particular, according to | U _grid -U _abc And the value of | judges whether a preset soft start condition is met.

If U _grid -U _abc If the value of | meets the preset soft start condition, controllingAnd the main circuit breaker 13 is closed, and the soft start contactor 12 is controlled to be opened, so that the process of soft start of the power unit 1 is completed.

And S140, if the first voltage does not meet the preset power supply condition, controlling the soft start contactor and the main loop circuit breaker to be disconnected.

During the soft start control of the power unit 1, if the first voltage U is lower than the second voltage U _grid Unsatisfied to predetermine the power supply condition, unsatisfied preset alternating current power supply condition promptly, then confirm that alternating voltage is unusual, need control soft start contactor 12 and major loop circuit breaker 13 disconnection, prevent that circuit device still works after the circuit loses voltage, the problem of circuit device damage.

In this embodiment, when the first voltage of the output of the obtained power supply satisfies the preset power supply condition, the soft start contactor is controlled to be closed, and then when the difference between the first voltage and the second voltage at the preset position of the output end of the main circuit breaker satisfies the soft start condition, the main circuit breaker is controlled to be closed, the soft start contactor is controlled to be opened, and when the first voltage does not satisfy the preset power supply condition, the soft start contactor and the main circuit breaker are controlled to be opened, so that the soft start control of the power unit is completed. By the mode, the switching state of the soft start contactor can be controlled in the power unit according to the power supply condition, the switching states of the main loop circuit breaker and the soft start contactor can be respectively controlled according to the soft start condition in the soft start process, the power unit can judge and control abnormal conditions in the soft start process, the situation that the power unit continuously operates under the condition that the power supply condition is not met to cause that a circuit bears larger impact voltage is avoided, the situation that devices of the power unit continuously input under the condition that the soft start condition is not met to cause damage due to overheating of the circuit is also avoided, and the power unit can run more safely and reliably by using the judging mechanism.

In order to clearly explain the process of judging the preset power supply condition in the soft start control method of the power unit, the embodiment of the invention also provides a possible implementation manner of judging the power supply condition in the soft start control method of the power unit. Fig. 4 is a schematic flow chart illustrating a power supply condition determination method for a power unit according to the present invention. As shown in fig. 4, in the method S120, before controlling the soft-start contactor to close if the first voltage meets the preset power supply condition, the method further includes:

and S122, if the first voltage is greater than the preset power supply voltage and an input closing instruction is received, determining that the first voltage meets the preset power supply condition.

In this embodiment, it is necessary to first determine whether the first voltage is greater than a predetermined power supply voltage. The rated working voltage U of the power unit 1 can be utilized _e And judging the power supply condition. When the power supply is an alternating current power supply, optionally, the power supply voltage can be preset to be 0.75U _e First voltage U obtained by controller 11 _grid Judgment of U _grid Whether it satisfies U _grid ＞0.75U _e 。

If it is judged that U is present _grid Satisfy U _grid ＞0.75U _e And at this time, when the controller 11 receives a closing instruction input from the outside, it is determined that the current circuit satisfies the power supply condition, and the current control state is maintained.

S124, if the first voltage is less than or equal to the preset power supply voltage, determining that the first voltage does not satisfy the preset power supply condition.

If the first voltage U is judged _grid Satisfy U _grid ≤0.75U _e If the current voltage is abnormal, the soft start contactor 12 and the main circuit breaker 13 are controlled to be disconnected, and the problem that circuit devices still work and are damaged after the circuit loses voltage is solved.

In this embodiment, the power supply condition is determined in the soft start process of the power unit, which is not only a prerequisite condition for the soft start of the circuit, but also enables the current power unit to exit the soft start process when the circuit is in voltage loss after the soft start is finished, so that the problem that the circuit device still works when the circuit is in voltage loss and the service life of the device is shortened is avoided.

In order to clearly explain the process of determining the soft start condition in the soft start control method of the power unit, embodiments of the present invention further provide a possible implementation manner of determining the soft start condition in the soft start control method of the power unit. Fig. 5 is a schematic flow chart illustrating the soft start condition determination in the method for controlling soft start of a power unit according to the present invention. As shown in fig. 5, in the method S130, if the voltage difference between the first voltage and the second voltage satisfies the preset soft start condition, before controlling the main circuit breaker to close and controlling the soft start contactor to open, the method includes:

s132, if the absolute value of the voltage difference is smaller than the preset voltage difference threshold, determining that the voltage difference satisfies the preset soft start condition.

In this embodiment, it is mainly determined whether the current power unit satisfies the preset soft start condition according to a voltage difference between the first voltage and the second voltage. Specifically, the judgment is made to determine whether the absolute value of the voltage difference is smaller than a preset alternating current voltage difference threshold value. Alternatively, the nominal operating voltage U of the power unit 1 can be utilized _e And judging the soft start condition. The voltage difference threshold value can be preset to be 0.05U _e First voltage U obtained by controller 11 _grid And a second voltage U _abc Judging | U _grid -U _abc Whether | is less than 0.05U _e . And if the absolute value of the voltage difference is smaller than a preset voltage difference threshold value, determining that the soft start condition is met.

If it is judged to be | U _grid -U _abc |＜0.05U _e If the soft start condition is satisfied, the main circuit breaker 13 is controlled to be closed, and the soft start contactor 12 is controlled to be opened.

S134, if the absolute value of the voltage difference is greater than or equal to the preset voltage difference threshold, determining that the voltage difference does not satisfy the preset soft start condition.

If it is judged to be | U _grid -U _abc |≥0.05U _e And if the voltage difference does not meet the preset soft start condition, the soft start fault is determined, and the soft start contactor 12 and the main circuit breaker 13 are controlled to be disconnected.

In this embodiment, the soft start condition is judged according to the current voltage condition after the power supply condition is met, so that the situation that the electronic device is overheated and damaged due to the fact that the circuit is still connected when the soft start fails is avoided, and the safe and stable operation of the circuit is guaranteed.

In order to clearly explain the process of controlling the main circuit breaker and the soft start contactor in the soft start control method of the power unit, the embodiment of the invention also provides a possible implementation mode of controlling the main circuit breaker and the soft start contactor in the soft start control method of the power unit. Fig. 6 is a schematic flow chart illustrating a process of controlling a main circuit breaker and a soft start contactor in the soft start control method of the power unit according to the present invention. As shown in fig. 6, in the method S140, controlling the main circuit breaker to close and controlling the soft start contactor to open includes:

and S142, controlling the main circuit breaker to be closed.

When the power unit 1 meets the soft start condition at this time, the main circuit breaker 13 is controlled to be closed first. Specifically, the main circuit breaker 13 may be controlled to close by way of the controller 11 output relay.

And S144, detecting the feedback state of the main circuit breaker.

After the controller 11 actively outputs the closing control to the main circuit breaker 13, at this time, the main circuit breaker 13 feeds back the current working state of the main circuit breaker 13 to the controller 11 in a dry contact manner, and at this time, the controller 11 needs to detect whether the feedback state of the main circuit breaker 13 is the closing state.

And S146, if the feedback state of the main loop breaker is a closed state, controlling the soft start contactor to be opened.

If the controller 11 detects that the feedback state of the main circuit breaker 13 is the closed state, the soft start contactor 12 is controlled to be opened. Alternatively, if the controller 11 detects that the feedback state of the main circuit breaker 13 is the open state, it determines that the main circuit breaker 13 is in a fault, and controls the soft start contactor 12 and the main circuit breaker 13 to open.

In the embodiment, the power unit judges the closing condition of the main circuit breaker in the soft start process, so that the condition that a circuit under the fault of the main circuit breaker cannot normally run is avoided, the electronic device is prevented from being damaged due to overheating caused by long-term running under the fault, and the safe running of the power unit is guaranteed.

On the basis of the schematic flow chart of controlling the main circuit breaker and the soft start contactor in the soft start control method of the power unit provided in fig. 6, the method further includes:

and S150, if the feedback states of the main circuit breaker are all the off states within a first preset time range from the first time, determining that the main circuit breaker has a fault.

The first time is the time for controlling the closing of the main circuit breaker.

And when the power unit 1 meets the soft start condition, timing is started from the closing of the main circuit breaker 13, and the first time is the time for controlling the closing of the main circuit breaker 13. In order to prevent the problem of the closed fault of the main circuit breaker 13, in this embodiment, the first time range may be preset to be 10s, and if the feedback states of the main circuit breaker 13 in the first preset time range from the first time are all open states, that is, when the main circuit breaker 13 is in an open state within 10s after the controller 11 sends out control to close the main circuit breaker 13, it is determined that the main circuit breaker 13 has a fault, and the soft start contactor 12 and the main circuit breaker 13 are controlled to be opened.

In this embodiment, when the controller of the power unit determines whether the main circuit breaker is closed, a certain buffering time is provided to determine whether the main circuit breaker is closed, so as to avoid misjudgment caused by data transmission problems.

On the basis of the schematic flow chart of determining the soft start condition in the soft start control method of the power unit provided in fig. 3, the method further includes:

and S160, if the absolute values of the voltage differences within a second preset time range from the second time are all larger than or equal to the preset voltage difference threshold, determining that the soft start overtime fault exists.

And the second time is the time for controlling the closing of the soft start contactor.

And after the power unit 1 meets the power supply condition, timing is started from the closing of the soft start contactor 12, and the second time is the time for controlling the closing of the soft start contactor 12. In order to prevent the soft start timeout from failing, in this embodiment, the second time range may be preset to be 30s, if the second time range is from the beginningThe absolute values of the voltage differences within a second preset time range from the second time are all larger than or equal to a preset voltage difference threshold value, namely | U within 30s _grid -U _abc All full symbol and U _grid -U _abc |≥0.05U _e Then, it is determined that there is a soft start timeout fault, and the soft start contactor 12 and the main circuit breaker 13 are controlled to open.

In this embodiment, when the controller of the power unit determines the soft start condition, a certain buffering time is provided to determine whether the soft start condition is satisfied, so as to avoid erroneous determination caused by data transmission problem. To more clearly illustrate the flow of the power unit soft start control method, reference is made to fig. 7. Fig. 7 is a flowchart illustrating another method for controlling soft-start of a power unit according to the present invention. In this embodiment, the soft-start control method for a power unit, where the power unit used is the power unit illustrated in any one of the above embodiments, is applied to the controller 11 in the power unit 1, and includes:

s1001, a first alternating current voltage output by a power supply and a second voltage at a preset position of an output end of a main circuit breaker are obtained.

First, a first voltage output by the power supply and a second voltage at a preset position of the output end of the main circuit breaker 13 need to be obtained by using a first detection end of the controller 11. The procedure of this step is similar to the procedure of S110, and is not described herein again.

S1002, judging whether the first voltage is larger than a preset power supply voltage.

After the first voltage is acquired, whether the first voltage is greater than a preset power supply voltage needs to be judged, so that whether the current voltage condition meets the power supply condition is judged. The procedure of this step is similar to the procedure of S120, and is not described herein again.

And S1003, if the first voltage is greater than the preset power supply voltage, determining that the power supply condition is met.

If the first voltage is larger than the preset power supply voltage, the current voltage condition meets the power supply condition, and the following steps are continued.

And S1004, if the first voltage is less than or equal to the preset power supply voltage, controlling the soft start contactor and the main circuit breaker to be disconnected.

If the first voltage is less than or equal to the preset power supply voltage, it indicates that the current voltage is in an abnormal fault problem, and the soft start contactor 12 and the main circuit breaker 13 need to be controlled to be disconnected. The procedure of this step is similar to the procedure of S124, and is not described herein again.

And S1005, judging whether a closing command exists.

When the first voltage is greater than the preset power supply voltage, whether a closing instruction exists needs to be judged, wherein the closing instruction is an externally input instruction and can be manually controlled; when the controller 11 receives a closing instruction, the soft start contactor 12 may be controlled to be closed.

And S1006, controlling the soft start contactor to be closed.

And when the controller 11 receives a closing instruction, controlling the soft start contactor 12 to be closed.

S1007, determining whether an absolute value of the voltage difference is smaller than a preset voltage difference threshold according to the voltage difference between the first voltage and the second voltage.

After the soft start contactor 12 is controlled to be closed, the voltage difference between the first voltage and the second voltage needs to be judged, and whether the absolute value of the voltage difference is smaller than a preset voltage difference threshold value needs to be judged. The procedure of this step is similar to the procedure of S132, and is not described herein again.

S1008, if the absolute value of the voltage difference is smaller than the preset voltage difference threshold, it is determined that the soft start condition is satisfied.

And if the voltage difference between the first voltage and the second voltage is smaller than a preset voltage difference threshold value, the current circuit condition meets the soft start condition, and the soft start is carried out. The procedure of this step is similar to the procedure of S132, and is not described herein again.

And S1009, if the absolute values of the voltage difference within the second preset time range from the second time are all larger than or equal to the preset voltage difference threshold, determining that the soft start overtime fault exists, and controlling the soft start contactor and the main circuit breaker to be disconnected.

When the absolute value of the voltage difference is judged to meet the preset voltage difference threshold condition, a certain time is provided for buffer judgment. The procedure of this step is similar to the procedure of S160, and is not described herein again.

And S1010, controlling the main circuit breaker to close.

When the soft start condition is satisfied, the controller 11 is required to control the main circuit breaker 13 to close. The procedure of this step is similar to the procedure of S142, and is not described herein again.

S1011, detecting whether the feedback state of the main circuit breaker is a closed state.

After the controller 11 outputs the closing control of the main circuit breaker 13, it is necessary to detect whether the feedback state of the main circuit breaker 13 is the closed state. The procedure of this step is similar to the procedure of S144, and is not described herein again.

And S1012, if the state is the closed state, controlling the soft start contactor to be disconnected.

If the state of the main circuit breaker 13 fed back to the controller 11 is the closed state, the controller 11 controls the soft start contactor 12 to open. The procedure of this step is similar to the procedure of S156, and is not described herein again.

And S1013, if the feedback states of the main circuit breaker are all off states within a first preset time range from the first time, determining that the main circuit breaker has a fault, and controlling the soft start contactor and the alternating current breaker to be off.

When judging whether the main circuit breaker 13 is closed, a certain time is provided for buffer judgment. The procedure of this step is similar to the procedure of S146, and is not described herein again.

In the embodiment, the power unit is subjected to fault judgment in the soft start process, and circuit connection can be cut off in time when a fault occurs, so that the electronic device is protected while the safe operation of the power unit is ensured, and the electronic device is prevented from being continuously connected to generate heat and damaged under the fault condition; meanwhile, the power unit is enabled to actively quit the soft start under the condition that the circuit voltage is in voltage loss after the soft start is finished, and the problems that circuit devices still work and are damaged after the circuit voltage is in voltage loss are solved.

With the increasing application of converters in the field of power distribution networks, the problem of controlling faults of the converters becomes more and more important. When the transformer is switched on or the fault is recovered and the transformer is put into the power grid again, due to the saturation of the magnetic flux of the iron core of the transformer and the nonlinear characteristic of the iron core material, excitation inrush current with quite large amplitude can be generated to flow through the differential protection of the transformer, and the differential protection malfunctions. When the transformer capacity is large, the generated magnetizing inrush current amplitude is also large, and even can reach dozens of times of rated current of the transformer. In addition, the magnetizing inrush current contains a plurality of harmonic components and direct-current components, so that the power supply quality of the power system can be reduced, and meanwhile, the higher harmonics in the inrush current can have a strong destructive effect on sensitive power electronic devices connected to the power system.

In order to solve the problem of magnetizing inrush current of a transformer in a converter and reduce the influence of the magnetizing inrush current on a power grid system, soft start control is often adopted for the transformer to achieve smooth start of the transformer and reduce the influence of start current on the power grid, so that the power grid system is protected. However, the existing soft start control cannot be actively withdrawn when the start fails, or is actively withdrawn after the soft start is completed, so that the soft start circuit is put into use for a long time, the electronic device is damaged to a certain extent, the problem of excitation inrush current of the transformer cannot be completely solved, and the use risk of a power grid system still exists.

Therefore, an embodiment of the present application further provides a converter, which includes the power unit, the transformer, and the ac-dc conversion unit included in any embodiment corresponding to fig. 1 and fig. 2, so as to implement the soft start control provided by the present application for the converter.

Fig. 8 is a schematic structural diagram of a current transformer provided in the present invention, and as shown in fig. 8, the current transformer 2 includes: the device comprises a controller 11, a soft start contactor 12, a main circuit breaker 13, a transformer 15 and an alternating current-direct current conversion unit 16.

In this embodiment, the power source is an ac power source. Wherein, a first detection end of the controller 11 is connected between the power supply and the input end of the main circuit breaker 13 to detect a first voltage output by the power supply; a soft start contactor 12 is also connected in parallel between the input end and the output end of the main circuit breaker 13; the output end of the main circuit breaker 13 is connected with the alternating current end of the alternating current-direct current conversion unit 16 through the transformer 15, namely the output end of the main circuit breaker 13 is connected with the input end of the transformer 15, the output end of the transformer 15 is also connected with the alternating current end of the alternating current-direct current conversion unit 16, and the direct current end of the alternating current-direct current conversion unit 16 is used for outputting a direct current signal; a soft start contactor 12 is connected in parallel between the input end and the output end of the main circuit breaker 13. The controller 11 is connected to an ac terminal of the ac-dc conversion unit 16 to detect a second voltage of the ac power input to the ac-dc conversion unit 16; the preset position on the current path is an alternating current end of the alternating current-direct current conversion unit.

The controller 11 is further connected with a control end of the soft start contactor 12 and a control end of the main loop circuit breaker 13, so that the soft start contactor 12 is controlled to be closed under the condition that the first voltage meets the preset power supply condition, the soft start contactor 12 is controlled to be opened when the voltage difference between the first voltage and the second voltage meets the soft start condition, the main loop circuit breaker 13 is controlled to be closed, and the soft start contactor 12 and the main loop circuit breaker 13 are controlled to be opened under the condition that the first voltage does not meet the preset power supply condition.

Alternatively, the controller 11 controls the soft start contactor 12 and the main circuit breaker 13 to be closed or opened by opening and closing the output relay coil; meanwhile, the soft start contactor 12 and the main circuit breaker 13 output a closed or open state through a dry contact and return to the controller 11, so that not only can crosstalk be prevented, but also the smoothness of an information transmission channel can be ensured.

In this embodiment, in the power unit 1, the power supply outputs three-phase alternating current, after the soft start contactor 12 completes the soft start control, the main circuit breaker 13 is closed and the soft start contactor 12 is disconnected, and then the main circuit of the power unit 1 is powered on at this time, and is isolated by the transformer 15 to perform ac-dc conversion in the ac-dc conversion unit 16, so as to obtain a dc electrical signal and supply power to the power grid.

Further, in the present embodiment, the transformer 15 plays a role of electrical isolation, and is used for isolating respective currents of the primary and secondary winding coils as a safety power protection circuit, but at the same time, a magnetizing inrush current is generated when the transformer 15 is switched on, and the electronic device is gradually loosened due to the impact of multiple magnetizing inrush currents. Further, the magnetizing inrush current may cause a differential protection operation of the transformer. In order to solve the problem of magnetizing inrush current, the soft start contactor 12 is used for carrying out soft start control on the transformer 15, and the bypass contactor is used for providing rated voltage so as to reduce the heat loss of electronic devices and solve the problem of magnetizing inrush current of the transformer. Meanwhile, fault judgment is carried out and connection is cut off in time in the soft start process, and meanwhile the transformer is made to exit the mechanism in time after the soft start is finished, so that the influence of excitation surge current on the circuit is avoided.

In the embodiment, the soft start control is realized by connecting the converter with the soft start contactor, so that the magnetizing inrush current influence of the transformer in the circuit is reduced, the transformer can be started smoothly, the impact of the starting current on a power grid is reduced, the service life of an electronic device is prolonged, and the circuit safety is protected.

On the basis of the above embodiments, the present invention also provides a possible implementation manner of the converter. Fig. 9 is a schematic structural diagram of another current transformer provided by the present invention. As shown in fig. 9, the current transformer 2 further includes: the resistor 14, the resistor 14 and the soft start contactor 12 are connected in series and then arranged in parallel between the input end and the output end of the main circuit breaker 13.

In the embodiment, the power failure is kept in the circuit by connecting the soft start contactor with the resistor in series, so that a certain time is provided for an operator to judge the abnormality, the problem that the circuit fault occurs when the electronic device is jacked to jump when the circuit is abnormally powered down is prevented, and the circuit safety is guaranteed.

On the basis of the above embodiments, the present invention also provides a possible implementation manner of the converter. Fig. 10 is a schematic structural diagram of another current transformer provided by the present invention. As shown in fig. 10, ac/dc conversion section 16 includes: the DC ends of the N AC/DC converters 17 after being connected in parallel are the DC ends of the AC/DC conversion unit 16; the sum of the input powers of the N ac/dc converters 17 is equal to the output power of the power supply.

Specifically, each ac/dc converter 17 can independently play a role of the ac/dc conversion unit 16, and the capacity of the converter can be expanded by the parallel connection, so that the converter can be applied to different ac power supplies. In practical applications, how many ac-dc converters 17 are used depends on the output power of the power supply; if any one of the AC/DC converters 17 fails, the AC/DC converter 17 can be replaced and processed independently, so that the difficulty of failure processing is reduced.

In this embodiment, the ac/dc conversion is performed by using the modular ac/dc converter, so that the ac/dc conversion can be more flexibly performed in accordance with the ac input conditions of various powers.

On the basis of the above embodiments, the present invention also provides a possible implementation manner of the converter. Fig. 11 is a schematic structural diagram of another current transformer provided by the present invention. As shown in fig. 11, the current transformer 2 further includes: the direct current breaker 18 and the direct current end of the alternating current-direct current conversion unit 16 are further connected with the direct current breaker 18, and are used for separating all parts of a power grid and providing reliability of the power grid under a fault.

In an interconnected power distribution network, in order to expand the control range, a converter is often used as a power conversion device in cooperation with transformers of different power grades. When the converter is used, however, the transformer as an iron core-containing element often causes a magnetic saturation phenomenon due to a remanence phenomenon and a normal period magnetic flux, so that an excitation inrush current problem occurs, a main circuit breaker cannot bear overcurrent and is tripped, and a circuit cannot be operated reliably. Therefore, in order to improve the stability of the power grid, the present application further provides a microgrid control device, and fig. 12 is a schematic structural diagram of the microgrid control device provided by the present invention.

As shown in fig. 12, the microgrid control device 3 comprises the converter 2 illustrated in any one of fig. 8 to 11, wherein a controller 11 in the microgrid control device 3 is used for executing the soft start control method of the power unit provided in any one of the embodiments, and the controller 11 is the controller 11 in the power unit 1 included in the converter 2.

Fig. 13 is a schematic diagram of a soft-start control apparatus for a power unit according to the present invention, and as shown in fig. 13, a soft-start control apparatus for a power unit, which is applied to any one of the controllers in the power unit in the foregoing embodiments, includes:

the acquisition module 1000 is configured to acquire a first voltage output by a power supply and a second voltage at a preset position of an output end of a main circuit breaker;

the control module 2000 is configured to control the soft start contactor to be closed if the first voltage meets a preset power supply condition;

the control module 2000 is further configured to, when the soft start contactor is closed, control the main circuit breaker to be closed and control the soft start contactor to be opened if a voltage difference between the first voltage and the second voltage meets a preset soft start condition.

The control module 2000 is further configured to control the soft-start contactor and the main circuit breaker to be disconnected if the first voltage does not satisfy the preset power supply condition.

Optionally, the control module 2000 is further specifically configured to determine that the first voltage meets the preset power supply condition if the first voltage is greater than the preset power supply voltage and an input closing instruction is received; and if the first voltage is less than or equal to the preset power supply voltage, determining that the first voltage does not meet the preset power supply condition. Optionally, the control module 2000 is further specifically configured to determine that the voltage difference satisfies the preset soft start condition if the absolute value of the voltage difference is smaller than the preset voltage difference threshold; and if the absolute value of the voltage difference is greater than or equal to the preset voltage difference threshold value, determining that the voltage difference does not meet the preset soft start condition.

Optionally, the control module 2000 is specifically further configured to control the main circuit breaker to close; detecting a feedback state of a main loop breaker; and if the feedback state of the main loop circuit breaker is a closed state, controlling the soft start contactor to be disconnected.

Optionally, the control module 2000 is further specifically configured to determine that the main circuit breaker has a fault if the feedback states of the main circuit breaker are all off states within a first preset time range from the first time; the first time is the time for controlling the closing of the main circuit breaker.

Optionally, the control module 2000 is further specifically configured to determine that a soft start timeout fault exists if the voltage difference within a second preset time range from the second time does not satisfy the preset soft start condition; and the second time is the time for controlling the closing of the soft start contactor.

These above modules may be one or more integrated circuits configured to implement the above methods, such as: one or more Application Specific Integrated Circuits (ASICs), or one or more Digital Signal Processors (DSPs), or one or more Field Programmable Gate Arrays (FPGAs), etc. For another example, when one of the above modules is implemented in the form of a Processing element scheduler code, the Processing element may be a general-purpose processor, such as a Central Processing Unit (CPU) or other processor capable of calling program code. For another example, these modules may be integrated together and implemented in the form of a system-on-a-chip (SOC).

Optionally, the invention also provides a program product, for example a computer-readable storage medium, comprising a program which, when being executed by a processor, is adapted to carry out the above-mentioned method embodiments.

In the embodiments provided in the present invention, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit may be implemented in the form of hardware, or in the form of hardware plus a software functional unit.

The integrated unit implemented in the form of a software functional unit may be stored in a computer readable storage medium. The software functional unit is stored in a storage medium and includes several instructions to enable a computer device (which may be a personal computer, a server, or a network device) or a processor (processor) to execute some steps of the methods according to the embodiments of the present invention. And the aforementioned storage medium includes: a U disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are also within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A soft start control method of a power unit is applied to a controller in the power unit, the power unit further comprises a soft start contactor and a main circuit breaker, and the method comprises the following steps:

2. The method according to claim 1, wherein before controlling the soft start contactor to close if the first voltage meets a preset power supply condition, the method further comprises:

3. The method according to claim 1, wherein before controlling the main circuit breaker to close and controlling the soft start contactor to open if the voltage difference between the first voltage and the second voltage satisfies a preset soft start condition, the method further comprises:

4. The method of claim 1, wherein the controlling the main circuit breaker to close and the soft start contactor to open comprises:

controlling the main circuit breaker to close;

detecting a feedback state of the main circuit breaker;

5. The method of claim 4, further comprising:

6. The method of claim 1, further comprising:

7. A power cell, comprising: the system comprises a controller, a soft start contactor and a main circuit breaker;

the controller is also connected with the control end of the soft start contactor and the control end of the main circuit breaker, and is used for executing the soft start control method of any one of the claims 1-6.

8. The power cell of claim 7, further comprising:

9. A current transformer, comprising: the power unit, transformer, and ac-dc conversion unit of any of claims 7-8;

10. A microgrid control device, characterized in that the microgrid control device comprises a converter according to claim 9, a controller in the microgrid control device being adapted to perform a method for controlling a soft start of a power unit according to any one of claims 1 to 6, the controller being a controller in a power unit comprised by the converter.