JP2021516946A - How to start a modular multi-level converter with a mixture of half bridges and full bridges - Google Patents

Abstract

The present invention provides a method for activating a modular multi-level converter in which half-bridges and full-bridges coexist. The method controls all the half-bridge submodules and all the full-bridge submodules to maintain locking so that all the half-bridge submodules and all the full-bridge submodules reach the initial voltage. And all the half-bridge submodules are controlled to maintain locking so as to reduce the rate of increase of the total voltage of the full-bridge submodules, and at least some of the fullbridge submodules are locked. Controlling the operating state to include either half locking or bypass, and the voltage of all the half bridge submodules reaches the rated voltage and the voltage of all the full bridge submodules is rated. It includes controlling the operating state including any one of bypassing or locking of each full bridge submodule and the operating state of each half bridge submodule so as to reach a voltage. The present invention further provides a starter for a modular multi-level converter in which half-bridges and full-bridges coexist. According to the above method and device, it is possible to avoid a large inrush current being generated at the timing of unlocking the system, and it is possible to improve the safety of the system.

Description

The present invention relates to the technical field of power supply, and particularly to a method and apparatus for starting a modular multi-level converter in which half-bridges and full-bridges coexist.

Modular multi-level converters (MMCs) provide high voltage output by cascading the submodule units of several converter valves. MMC does not require direct cascade of switching elements, has low requirements for simultaneous triggering of elements, has good expandability, low switching frequency, low operating loss, high quality of output voltage waveform, etc. There are many advantages of.

However, when the AC transmission network supplies power to the flexible DC transmission network via the MMC, the flexible DC transmission network has low attenuation characteristics. Therefore, when the MMC causes a short-circuit failure, the current increase rate at the initial stage of the failure is It is a level of several thousand amps / millisecond. On the other hand, the AC circuit breaker also has a breaking speed that cuts off in tens of milliseconds. During this period of several tens of milliseconds, key devices such as MMCs in the DC power grid were subjected to severe electrical stress, which reduced the operational safety of the devices in the power grid. Therefore, when the MMC causes a short-circuit failure, the safety of the electric grid system deteriorates.

According to the above, to solve the problem that the safety of the electric network system is deteriorated when the current MMC causes a short circuit failure, a method and an apparatus for starting a modular multi-level converter in which a half bridge and a full bridge are mixed are provided.

A method of activating a modular multi-level converter in which half-bridge and full-bridge are mixed, the modular multi-level converter includes a plurality of half-bridge submodules and a plurality of full-bridge submodules. The method controls all the half-bridge submodules and all the full-bridge submodules to maintain locking so that all the half-bridge submodules and all the full-bridge submodules reach the initial voltage. And all the half-bridge submodules are controlled to maintain locking so as to reduce the rate of increase of the total voltage of the full-bridge submodules, and at least some of the fullbridge submodules are locked. Controlling the operating state to include either half locking or bypass, and the voltage of all the half bridge submodules reaches the rated voltage and the voltage of all the full bridge submodules is rated. It includes controlling the operating state including any one of bypassing or locking of the full bridge submodule and the operating state of each half bridge submodule so as to reach the voltage.

In one embodiment, the modular multi-level converter is connected to an AC network via a series charging resistor.

In one embodiment, all the half-bridge submodules are controlled to maintain locking so as to reduce the rate of increase in the total voltage of the full-bridge submodule, and at least some of the full-bridge submodules operate. Prior to controlling the state, it includes controlling to bypass the charging resistance when the current of the charging resistance is smaller than a preset current value.

In one embodiment, all the half-bridge submodules are controlled to maintain locking so as to reduce the rate of increase in the total voltage of the full-bridge submodule, and at least some of the full-bridge submodules operate. Prior to controlling the state, it includes controlling to bypass the charging resistance when the voltage of the charging resistance is higher than a preset voltage value.

In one embodiment, all the half-bridge submodules are controlled to maintain locking so as to reduce the rate of increase in the total voltage of the full-bridge submodule, and at least some of the full-bridge submodules operate. Controlling the state further controls all half-bridge submodules to maintain locking when the voltage of each full-bridge submodule reaches the operating threshold of the self-powered acquisition power supply, and the voltage. Is controlled so that the full bridge submodule having a voltage equal to or higher than the first threshold voltage is bypassed, and the voltage is between the second threshold voltage lower than the first threshold voltage and the first threshold voltage. The full bridge submodule is controlled to be half-locked, and the full bridge submodule whose voltage is less than the second threshold voltage is controlled to be locked.

In one embodiment, all the half-bridge submodules are controlled to maintain locking so as to reduce the rate of increase in the total voltage of the full-bridge submodule, and at least some of the full-bridge submodules operate. After controlling the state, if the ratio of the average voltage of all the half-bridge submodules to the average voltage of all the full-bridge submodules is greater than a preset multiple, then all the full-bridge submodules. It includes controlling the module to be half-locked and controlling all the half-bridge submodules to be locked.

In one embodiment, the preset multiple is in the range of 0.6 to 1.4.

In one embodiment, each full-bridge submodule and each half-bridge submodule so that the voltages of all the half-bridge submodules reach the rated voltage and the voltages of all the full-bridge submodules reach the rated voltage. To control each of the operating states of the above is further controlled so that the full bridge submodule whose voltage is equal to or higher than the third threshold voltage is bypassed, and the half bridge sub module whose voltage is equal to or higher than the third threshold voltage. Includes controlling the module to bypass.

A starter for a modular multi-level converter in which half-bridge and full-bridge are mixed, the modular multi-level converter includes a plurality of half-bridge submodules and a plurality of full-bridge submodules, and the modular multi-level converter is in series. It is connected to the AC network via a charging resistor. The device controls all the half-bridge submodules and all the full-bridge submodules to maintain locking so that all the half-bridge submodules and all the full-bridge submodules reach the initial voltage. All the half-bridge submodules are controlled to maintain locking, and at least some of the full-bridge submodules are controlled so as to reduce the rate of increase of the total voltage of the uncontrolled start module and the full bridge submodule. A partial control start module that controls the module so that it is in an operating state that includes any one of locking, half-locking, or bypass, and all the full bridges as the voltage of all the half-bridge submodules reaches the rated voltage. All control activation that controls the operating state including any one of bypassing or locking of each full bridge submodule and the operating state of each half bridge submodule so that the voltage of the submodule reaches the rated voltage. Includes modules and.

In one embodiment, the partial control activation module controls all the half bridge submodules to maintain locking when the voltage of each full bridge submodule reaches the operating threshold of the self-powered acquisition power supply. Then, the full bridge submodule whose voltage is equal to or higher than the first threshold voltage is controlled to bypass, and the voltage is between the second threshold voltage lower than the first threshold voltage and the first threshold voltage. The full bridge submodule is controlled to be half-locked, and the full bridge submodule whose voltage is less than the second threshold voltage is controlled to be locked.

According to the above-mentioned method and device for starting a modular multi-level converter in which half-bridge and full-bridge are mixed, first, all half-bridge submodules and all full-bridge submodules must reach the initial voltage in order to reach the initial voltage. Control the submodule and all full bridge submodules to maintain locking, i.e. control all half bridge submodules and all full bridge submodules to be charged. Next, all half-bridge submodules are controlled to maintain locking, and at least some full-bridge submodules are controlled to operate so as to reduce the rate of increase in the total voltage of the full-bridge submodules. In this way, the average voltage of all half-bridge submodules gradually increases, the average voltage of all full-bridge submodules also gradually increases, and the values of both gradually approach each other. The voltage of the module is averaged. After that, the operating state of each full-bridge submodule and each half-bridge submodule is controlled so that the voltage of all half-bridge submodules reaches the rated voltage and the voltage of all full-bridge submodules reaches the rated voltage. To do. Thus, while the modular multi-level converter is booting, the voltages of all full-bridge submodules and all half-bridge submodules will gradually increase, and the voltages of all submodules will be averaged. It is maintained in a state of being. Therefore, the output voltage of the modular multi-level converter gradually increases to the rated voltage. As a result, it is possible to prevent a large inrush current from being generated at the timing of unlocking the system, and it is possible to improve the safety of the electric network system.

It is the schematic of the modular multi-level converter of one Example. It is the schematic of the half bridge submodule of one Example. It is the schematic of the state which the half bridge submodule of one Example was bypassed. It is the schematic of the full bridge submodule of one Example. It is the schematic of the state which the full bridge submodule of one Example is half-locked. It is the schematic of the state which the full bridge submodule of one Example was bypassed. It is the schematic which connects the modular multi-level converter of one Example to an AC electric network. It is the schematic of the procedure of the activation method of the modular multi-level converter in which the half bridge and the full bridge of the first embodiment are mixed. It is the schematic of the procedure of the activation method of the modular multi-level converter in which the half bridge and the full bridge of the second embodiment are mixed. It is the schematic of the procedure of the activation method of the modular multi-level converter in which the half bridge and the full bridge of the third embodiment are mixed. It is a block diagram of the activation device of the modular multi-level converter in which the half bridge and the full bridge of one embodiment are mixed.

In order to clarify the above object, feature and advantage of the present invention, specific embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic view of a modular multi-level converter of one embodiment. As shown in FIG. 1, the modular multi-level converter includes a plurality of half-bridge submodules and a plurality of full-bridge submodules. Here, the half-bridge submodule and the full-bridge submodule are collectively referred to as a submodule. Modular multi-level converters (also abbreviated as converters) with a mixture of half-bridges and full-bridges include at least one phase unit. In this embodiment, the converter includes a three-phase unit, which is an A-phase unit, a B-phase unit, and a C-phase unit, respectively. Each phase unit includes an upper arm and a lower arm. The configuration of the upper arm and the lower arm is the same. The upper arm and the lower arm each include at least one half-bridge submodule connected in series with each other, at least one full-bridge submodule, and one reactance. In this embodiment, the upper arm and the lower arm each include one half-bridge submodule, one full-bridge submodule, and one reactance connected in series with each other. In this embodiment, the converter further includes a control device (not shown).

First, the half-bridge submodule and the full-bridge submodule will be described in detail below.

FIG. 2 is a schematic view of a half-bridge submodule of one embodiment. The half-bridge submodule includes a capacitor and a first switching unit connected in parallel to the capacitor. In this embodiment, the first switching unit includes a first breakable element and a second breakable element. The negative electrode of the first breakable element and the positive electrode of the second breakable element are connected in series with each other to form the first switching unit. The positive electrode of the first cuttable element functions as the positive electrode of the first switching unit, and the negative electrode of the second cuttable element functions as the negative electrode of the first switching unit. The place where the first breakable element and the second breakable element are connected functions as a first terminal, and the negative electrode of the first switching unit functions as a second terminal. The half-bridge submodule is connected to the corresponding circuit via a first terminal and a second terminal. The operating state of the half-bridge submodule includes bypassing or locking.

The operating state in which the half-bridge submodule is locked may be referred to in FIG. Locking the half-bridge submodule means that the first breakable element of the half-bridge submodule is turned off and the second breakable element is turned off.

FIG. 3 is a schematic view of a state in which the half bridge submodule of one embodiment is bypassed. As shown in FIG. 3, bypassing the half-bridge submodule means that the first breakable element of the half-bridge submodule is turned off and the second breakable element is turned on. ..

FIG. 4 is a schematic view of a full bridge submodule of one embodiment. The full bridge submodule includes a capacitor and a second switching unit and a third switching unit connected in parallel to the capacitor. The second switching unit includes a third breakable element and a fourth breakable element. The negative electrode of the third breakable element is connected in series with the positive electrode of the fourth breakable element. The positive electrode of the third cuttable element functions as the positive electrode of the second switching unit, and the negative electrode of the fourth cuttable element functions as the negative electrode of the second switching unit. The place where the third breakable element and the fourth breakable element are connected functions as a third terminal. The third switching unit includes a fifth breakable element and a sixth breakable element. The negative electrode of the fifth breakable element is connected in series with the positive electrode of the sixth breakable element. The positive electrode of the fifth breakable element functions as the positive electrode of the third switching unit, and the negative electrode of the sixth cuttable element functions as the negative electrode of the third switching unit. The place where the fifth breakable element and the sixth breakable element are connected functions as a fourth terminal. The full bridge submodule is connected to the corresponding circuit via a third terminal and a fourth terminal. The operating state of the full bridge submodule includes one of locking, half locking, or bypass.

Locking the full bridge submodule means that all the third, fourth, fifth, and sixth interruptable elements of the full bridge submodule are turned off. A schematic diagram of the locked state of the full bridge module may be referred to in FIG.

FIG. 5 is a schematic view of a state in which the full bridge submodule of one embodiment is half-locked. As shown in FIG. 5, the fact that the full bridge submodule is half-locked means that the third breakable element of the full bridge submodule is turned on and the fourth, fifth, and sixth breakable elements are turned on. Means that is turned off. In other embodiments, the third, fourth, and fifth destructible elements may be turned off and the sixth destructible element may be turned on.

FIG. 6 is a schematic view of a state in which the full bridge submodule of one embodiment is bypassed. As shown in FIG. 6, the bypass of the full bridge submodule means that the third and fifth breakable elements of the full bridge submodule are turned off and the fourth and sixth breakable elements are turned on. Means to become. In other embodiments, the third and fifth breakable elements may be turned on and the fourth and sixth breakable elements may be turned off.

FIG. 7 is a schematic view of the modular multi-level converter of one embodiment connected to an AC network. The modular multi-level converter is connected to the AC network via a series charging resistor. In this embodiment, the converter is connected to the AC network via the charging resistor R, its bypass switch QA, and the inlet switch QF. However, the charging resistor R is connected in series with the inlet switch QF. The charging resistor R is connected in parallel with the bypass switch QA.

FIG. 8 is a schematic diagram of a procedure of a method of starting a modular multi-level converter in which a half bridge and a full bridge of the first embodiment are mixed. This method includes the following procedure.

In step S120, all half-bridge submodules and all full-bridge submodules are controlled to maintain locking so that all half-bridge submodules and all full-bridge submodules reach the initial voltage.

Specifically, this step is an uncontrolled activation stage. That is, at this stage, the controller controls all submodules to lock, turns on the inlet switch QF to charge all submodules, and thus has an initial voltage at which all submodules can operate. Let me. As a result, each submodule can be moved to the preparatory operation. The charging resistor R can prevent the system element from being destroyed due to an overcurrent generated at the initial stage of charging the AC system. The control device controls to bypass the charging resistance when the current of the charging resistance is smaller than a preset current value. Alternatively, the control device controls to bypass the charging resistor when the voltage of the charging resistor is higher than a preset voltage value. During one cycle of alternating current, one full-bridge submodule is continuously charged, whereas one half-bridge submodule is charged only in half of that cycle. Therefore, even after the same charging time has passed, the voltage of one full-bridge submodule is about twice as high as the voltage of one half-bridge submodule, and the voltage of each submodule is low. In this way, the converter is ready for the next stage of operation. Further, the preset current value may be 0.1 pu. The preset voltage value may be "0".

In step S140, all half-bridge submodules are controlled to maintain locking and at least some full-bridge submodules are controlled to operate so as to reduce the rate of increase in the total voltage of the full-bridge submodules. ..

Specifically, this stage is a partial control activation stage. That is, the control device controls the full bridge submodule without controlling the half bridge submodule. The controller controls these full-bridge submodules to be half-locked because some full-bridge submodules are charged in half the cycle of the alternating current. Alternatively, the control device controls these full-bridge submodules to bypass so that some full-bridge submodules stop charging. In this way, the charging speed of all full-bridge submodules can be reduced to reduce the rate of increase in total voltage, while the charging rate of all half-bridge submodules can be increased to increase the rate of voltage increase. .. Therefore, the average voltage of all half-bridge submodules gradually increases, the average voltage of all full-bridge submodules also gradually increases, and the values of both gradually approach each other, and finally all the submodules. The voltage is averaged. Therefore, the output voltage of the converter rises smoothly, and the inrush current generation rate decreases.

In step S160, the operating states of each full-bridge submodule and each half-bridge submodule are set so that the voltages of all half-bridge submodules reach the rated voltage and the voltages of all full-bridge submodules reach the rated voltage. To control.

Specifically, this stage is the full control activation stage. That is, the control device can control the full bridge submodule and the half bridge submodule at the same time. The operating state of each full-bridge submodule and each half-bridge submodule is dynamically controlled to gradually adjust the voltage of all submodules to the rated voltage to complete the startup process.

According to the above method of starting a modular multi-level converter with a mixture of half-bridge and full-bridge, first, all half-bridge submodules and all full-bridge submodules must reach the initial voltage in order for all half-bridge submodules to reach the initial voltage. And all full bridge submodules are controlled to maintain locking, i.e. all half bridge submodules and all full bridge submodules are controlled to be in a charged state. Next, all half-bridge submodules are controlled to maintain locking, and at least some full-bridge submodules are controlled to operate so as to reduce the rate of increase in the total voltage of the full-bridge submodules. In this way, the average voltage of all half-bridge submodules gradually increases, the average voltage of all full-bridge submodules also gradually increases, and the values of both gradually approach each other. The voltage of the module is averaged. After that, the operating state of each full-bridge submodule and each half-bridge submodule is controlled so that the voltage of all half-bridge submodules reaches the rated voltage and the voltage of all full-bridge submodules reaches the rated voltage. To do. Thus, while the modular multi-level converter is booting, the voltages of all full-bridge submodules and all half-bridge submodules will gradually increase, and the voltages of all submodules will be averaged. It is maintained in a state of being. Therefore, the output voltage of the modular multi-level converter gradually increases to the rated voltage. As a result, it is possible to prevent a large inrush current from being generated at the timing of unlocking the system, and it is possible to improve the safety of the electric network system.

FIG. 9 is a schematic diagram of the procedure of how to start the modular multi-level converter in which the half bridge and the full bridge of the second embodiment are mixed. All half-bridge submodules are controlled to maintain locking so as to reduce the rate of increase in the total voltage of the full-bridge submodules, and at least some of the full-bridge submodules are controlled to operate. That is, step S140. Before doing so, it further includes the following steps:

In step S130, it is detected whether or not the voltage of each full bridge submodule has reached the operating threshold value of the self-power acquisition power supply. When the voltage of each full bridge submodule reaches the operating threshold of the self-power acquisition power supply, step S140 is executed. If the voltage of each full bridge submodule has not reached the operating threshold of the self-power acquisition power supply, step S130 is continuously executed.

Specifically, whether or not the voltage of each full-bridge submodule reaches the operating threshold value of the self-power acquisition power supply means whether or not each full-bridge submodule can operate normally. This means that each full-bridge submodule can trigger and operate by itself when the voltage of each full-bridge submodule reaches the operating threshold of the self-power acquisition power supply. Otherwise, the full bridge submodule whose voltage has not reached the operating threshold needs to be continuously charged.

All half-bridge submodules are controlled to maintain locking so as to reduce the rate of increase in the total voltage of the full-bridge submodules, and at least some of the full-bridge submodules are controlled to operate. That is, step S140. Before doing so, it further includes the following steps:

When the voltage of each full-bridge submodule reaches the operating threshold of the self-power acquisition power supply, step S141 is executed to control all half-bridge submodules to maintain locking.

Specifically, at this time, the voltage of each half-bridge submodule is lower than the voltage of any one full-bridge submodule. In this step, the device is controlled so that the half-bridge submodule is continuously charged.

In step S142, the full bridge submodule whose voltage is equal to or higher than the first threshold voltage is controlled to bypass.

Specifically, the control device controls the full-bridge submodules whose voltage is equal to or higher than the first threshold voltage so that they are bypassed so that they are neither charged nor discharged. In this way, in the same AC network, the number of full-bridge submodules to be charged at the same time can be reduced, and the number of half-bridge submodules to be charged remains the same, so that the voltage rise rate of each half-bridge submodule is fast. Become. That is, the charging speed of each half-bridge submodule is increased.

In step S143, the full bridge submodule whose voltage is between the second threshold voltage and the first threshold voltage is controlled to be half-locked.

Specifically, the second threshold voltage is lower than the first threshold voltage. The controller makes the full-bridge submodule equivalent by controlling the full-bridge submodule whose voltage is between the second threshold voltage and the first threshold voltage so that it is half-locked. Can be done. Since the voltage of these full bridge submodules is low, they can be continuously charged, but the charging speed is reduced. On the other hand, the charging speed of each bridge module can be further increased.

In step S144, the full bridge submodule whose voltage is less than the second threshold voltage is controlled to lock.

Specifically, because the voltage of the full bridge submodule whose voltage is less than the second threshold voltage is low, the controller controls these full bridge submodules to lock, i.e., these full bridge submodules are usually Control to continuously charge at a high speed.

Through the above steps, the controller can reduce the overall charging rate of all full-bridge submodules and increase the overall charging rate of all half-bridge submodules. The average voltage of all half-bridge submodules gradually increases. The average voltage of all full bridge submodules also gradually increases. However, the rate of increase in the average voltage of all half-bridge submodules is faster than the rate of increase in the average voltage of all full-bridge submodules. Eventually, the average voltage of the half-bridge submodule and the average voltage of the full-bridge submodule will match. That is, the average voltage of the half-bridge submodule and the average voltage of the full-bridge submodule are equal or almost equal. In this way, the voltages of all the submodules in the converter gradually reach a state of being averaged, and finally the voltages of all the submodules reach the operating threshold of the self-power acquisition power supply. This reduces the difficulty of designing the self-powered power source of each submodule. Further, the inrush current can be effectively avoided by gradually increasing the voltage of the converter.

FIG. 10 is a schematic diagram of a procedure of a method of starting a modular multi-level converter in which a half bridge and a full bridge of the third embodiment are mixed. In this embodiment, all half-bridge submodules are controlled to maintain locking and at least some full-bridge submodules are controlled to operate so as to reduce the rate of increase in the total voltage of the full-bridge submodules. That is, after step S140, the following procedure is further included.

In step S151, it is determined whether or not the ratio of the average voltage of all half-bridge submodules to the average voltage of all full-bridge submodules is greater than a preset multiple.

In step S153, if the ratio of the average voltage of all half-bridge submodules to the average voltage of all full-bridge submodules is greater than a preset multiple, all full-bridge submodules are half-locked. Control and control all half-bridge submodules to lock.

In this way, the controller ensures that all full bridge submodules correspond to half bridge submodules. That is, all submodules in the converter are half-bridge submodules. In this case, the type of submodule of the converter can be made single, and the control device can be easily controlled. Specifically, the preset multiple may be in the range of 0.6 to 1.4. Thus, the average voltage of all half-bridge submodules and the average voltage of all full-bridge submodules are approximately equal. That is, the voltage of the converter reaches the balanced state, and the voltage of the converter always increases in a well-balanced manner.

In this embodiment, the operating state of each full bridge submodule and each half bridge submodule is set so that the voltage of all half bridge submodules reaches the rated voltage and the voltage of all full bridge submodules reaches the rated voltage. Controlling each, i.e., step S160 further includes the following procedure.

In step S161, the full bridge submodule whose voltage is equal to or higher than the third threshold voltage is controlled to bypass, and the half bridge submodule whose voltage is equal to or higher than the third threshold voltage is controlled to bypass.

Specifically, the control device controls so that when the voltage of the converter approaches the rated voltage, some of the full bridge submodules having a high voltage stop charging, that is, they are in a bypass state. The control device controls some of the high voltage half-bridge submodules to stop charging, that is, to be in a bypass state. In this way, the voltage rise rate of all submodules is further reduced, and the total voltage of all submodules gradually approaches the rated voltage. As a result, it is possible to prevent a large inrush current from being generated at the timing of unlocking the system.

FIG. 11 is a block diagram of a starter device of a modular multi-level converter in which a half bridge and a full bridge of one embodiment are mixed. In a modular multi-level converter activation device in which half-bridge and full-bridge are mixed, the modular multi-level converter includes a plurality of half-bridge submodules and a plurality of full-bridge submodules, and the modular multi-level converter provides a series charging resistor. It is connected to the AC network via. This device controls all half-bridge submodules and all full-bridge submodules to maintain locking so that all half-bridge submodules and all full-bridge submodules reach the initial voltage. All half-bridge submodules are controlled to maintain locking, and at least some full-bridge submodules are locked, half-locking, to reduce the rate of increase in the total voltage of module 120 and the full-bridge submodule. Alternatively, the partial control start module 140 that controls the operation state including any one of the bypasses and the voltage of all the half bridge submodules reaches the rated voltage, and the voltage of all the full bridge submodules reaches the rated voltage. Includes an operating state that includes any one of bypassing or locking of each full bridge submodule and a full control activation module 160 that controls the operating state of each halfbridge submodule, respectively.

According to the above half-bridge and full-bridge mixed modular multi-level converter starter, first all half-bridge submodules and all full-bridge submodules have to reach the initial voltage in order for all half-bridge submodules to reach the initial voltage. And all full bridge submodules are controlled to maintain locking, i.e. all half bridge submodules and all full bridge submodules are controlled to be in a charged state. Next, all half-bridge submodules are controlled to maintain locking, and at least some full-bridge submodules are controlled to operate so as to reduce the rate of increase in the total voltage of the full-bridge submodules. In this way, the average voltage of all half-bridge submodules gradually increases, the average voltage of all full-bridge submodules also gradually increases, and the values of both gradually approach each other. The voltage of the module is averaged. After that, the operating state of each full-bridge submodule and each half-bridge submodule is controlled so that the voltage of all half-bridge submodules reaches the rated voltage and the voltage of all full-bridge submodules reaches the rated voltage. To do. Thus, while the modular multi-level converter is booting, the voltages of all full-bridge submodules and all half-bridge submodules will gradually increase, and the voltages of all submodules will be averaged. It is maintained in a state of being. Therefore, the output voltage of the modular multi-level converter gradually increases to the rated voltage. As a result, it is possible to prevent a large inrush current from being generated at the timing of unlocking the system, and it is possible to improve the safety of the electric network system.

In one embodiment, the partial control activation module 140 controls all halfbridge submodules to maintain locking when the voltage of each full bridge submodule reaches the operating threshold of the self-powered acquisition power supply.

The partial control activation module 140 further controls the full bridge submodule whose voltage is equal to or higher than the first threshold voltage so as to bypass.

The partial control activation module 140 further controls the full bridge submodule between the second threshold voltage and the first threshold voltage whose voltage is lower than the first threshold voltage so as to be half-locked.

The partial control activation module 140 further controls the full bridge submodule whose voltage is less than the second threshold voltage to lock.

The technical features of each of the above embodiments can be arbitrarily combined, and for the sake of brevity, all combinations of the features of each of the above embodiments are not described, but combinations of these features are not described. As long as there is no contradiction, it is natural that it falls within the scope of the present application.

Each of the above examples merely shows some embodiments of the present invention and has been described in detail and in detail, but it should be understood that the scope of the present application is not limited. For those skilled in the art, even if some modifications and improvements are made, they belong to the scope of the present application as long as they do not deviate from the gist of the present application. Therefore, the scope of the present application is based on the attached claims.

Claims (10)

How to start a modular multi-level converter with a mixture of half-bridges and full-bridges
The modular multi-level converter includes a plurality of half-bridge submodules and a plurality of full-bridge submodules.
The method is
To control all the half-bridge submodules and all the full-bridge submodules to maintain locking so that all the half-bridge submodules and all the full-bridge submodules reach the initial voltage.
All the half-bridge submodules are controlled to maintain locking so as to reduce the rate of increase in the total voltage of the full-bridge submodules, and at least some of the fullbridge submodules are locked, half-locked, or Controlling to include one of the bypasses and
Includes any one of bypassing or locking of each full bridge submodule so that the voltage of all the half bridge submodules reaches the rated voltage and the voltage of all the full bridge submodules reaches the rated voltage. The method is characterized by including controlling the operating state and the operating state of each of the half-bridge submodules. The method of claim 1, wherein the modular multi-level converter is connected to an AC network via a series charging resistor. Control all the half-bridge submodules to maintain locking and control the operating state of at least some of the full-bridge submodules so as to reduce the rate of increase in the total voltage of the full bridge submodules. In front of,
The method according to claim 2, wherein when the current of the charging resistor is smaller than a preset current value, control is performed so as to bypass the charging resistor. Control all the half-bridge submodules to maintain locking and control the operating state of at least some of the full-bridge submodules so as to reduce the rate of increase in the total voltage of the full bridge submodules. In front of,
The method according to claim 2, wherein when the voltage of the charging resistor is higher than a preset voltage value, control is performed so as to bypass the charging resistor. Control all the half-bridge submodules to maintain locking and control the operating state of at least some of the full-bridge submodules so as to reduce the rate of increase in the total voltage of the full bridge submodules. Is
Furthermore, when the voltage of each full bridge submodule reaches the operating threshold of the self-power acquisition power supply, all half bridge submodules are controlled to maintain locking.
Control so that the full bridge submodule whose voltage is equal to or higher than the first threshold voltage is bypassed.
Controlling the full bridge submodule between the second threshold voltage whose voltage is lower than the first threshold voltage and the first threshold voltage so as to be half-locked.
The method according to claim 1, wherein the full bridge submodule whose voltage is less than the second threshold voltage is controlled to lock. Control all the half-bridge submodules to maintain locking and control the operating state of at least some of the full-bridge submodules so as to reduce the rate of increase in the total voltage of the full bridge submodules. After the,
If the ratio of the average voltage of all the half-bridge submodules to the average voltage of all the full-bridge submodules is greater than a preset multiple, control so that all the full-bridge submodules are half-locked. The method of claim 1, wherein all the half-bridge submodules are controlled to lock. The method according to claim 6, wherein the preset multiple is in the range of 0.6 to 1.4. The operating states of each full-bridge submodule and each half-bridge submodule are set so that the voltages of all the half-bridge submodules reach the rated voltage and the voltages of all the full-bridge submodules reach the rated voltage. To control
Further, the present invention includes controlling the full bridge submodule having a voltage equal to or higher than the third threshold voltage to bypass, and controlling the half bridge submodule having a voltage equal to or higher than the third threshold voltage so as to bypass. The method according to claim 1, wherein the method is characterized by the above. A modular multi-level converter starter with a mix of half-bridges and full-bridges.
The modular multi-level converter includes a plurality of half-bridge submodules and a plurality of full-bridge submodules, and the modular multi-level converter is connected to an AC network via a series charging resistor.
The device is
An uncontrolled activation that controls all the half-bridge submodules and all the full-bridge submodules to maintain locking so that all the half-bridge submodules and all the full-bridge submodules reach the initial voltage. Module and
All the half-bridge submodules are controlled to maintain locking so as to reduce the rate of increase in the total voltage of the full-bridge submodules, and at least some of the fullbridge submodules are locked, half-locked, or A partial control activation module that controls the operating state including any one of the bypasses,
Includes any one of bypassing or locking of each full bridge submodule so that the voltage of all the half bridge submodules reaches the rated voltage and the voltage of all the full bridge submodules reaches the rated voltage. The device is characterized by including an operating state and an all-control activation module that controls the operating state of each of the half-bridge submodules. The partial control activation module is
When the voltage of each full bridge submodule reaches the operating threshold of the self-powered acquisition power supply, all the half bridge submodules are controlled to maintain locking.
The full bridge submodule whose voltage is equal to or higher than the first threshold voltage is controlled so as to be bypassed.
The full bridge submodule located between the second threshold voltage whose voltage is lower than the first threshold voltage and the first threshold voltage is controlled to be half-locked.
The device according to claim 9, wherein the full bridge submodule whose voltage is less than the second threshold voltage is controlled to lock.

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