Turn-off control method, device, medium and equipment for phase-change current converter of turn-off power grid

Abstract

The invention relates to the technical field of turn-off power grid commutation converters, in particular to a turn-off control method and device of a turn-off power grid commutation converter, a storage medium and equipment, the turn-off power grid commutation converter comprises a converter transformer and a converter valve, the converter valve comprises a plurality of bridge arms, each bridge arm comprises an IGCT, and the IGCT is connected with the converter transformer. The method comprises the following steps: acquiring three-phase AC voltage of a converter transformer network side, and calculating commutation voltage of each bridge arm of a converter valve according to the acquired three-phase AC voltage; and after the pre-opening bridge arm enters the trigger period, starting to monitor the commutation voltage of the corresponding pre-closing bridge-cutoff arm, judging whether the commutation capability of the power grid reaches the limit or not according to the commutation voltage of the pre-closing bridge-cutoff arm, and if the commutation capability of the power grid reaches the limit, issuing an active turn-off instruction to the pre-closing bridge-cutoff arm. According to the method, the power grid voltage borne by the pre-turn-off bridge arm after each bridge arm enters the trigger period is monitored, and the turn-off instruction is issued at the zero crossing point of the power grid voltage, so that the commutation capability provided by the power grid is fully utilized to ensure that commutation failure is resisted.

Description

Technical Field

[0001] The present invention relates to the technical field of a turn-off grid phase-commutation converter, and in particular to a turn-off control method, device, storage medium and equipment for a turn-off grid phase-commutation converter. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] High-voltage direct current transmission is an important means to realize the energy channel of west-to-east power transmission. At present, my country has built and operated many high-voltage direct current transmission projects. Conventional high-voltage direct current transmission adopts grid-commutated converter (LCC), which has the advantages of large transmission capacity, mature engineering technology, and low cost compared with flexible direct current. However, LCC uses thyristors that can only be actively opened and cannot be actively turned off as core switching devices, and needs to rely on the voltage of the AC power grid to achieve phase change. When the power grid is disturbed or the voltage drops due to a fault, there is a risk of phase change failure in the receiving-end LCC. Phase change failure will cause DC overcurrent, endangering the safety of the DC transmission system; at the same time, due to the instantaneous interruption of DC power when the phase change fails, the power flow of the power grids at the sending and receiving ends is greatly adjusted, which will also endanger the safe and stable operation of the AC power grid. In view of the above-mentioned defects, the present invention has made improvements. Summary of the invention

[0004] In order to overcome the shortcomings of the background technology, the present invention provides a shutdown control method, device, storage medium and equipment for a grid-switching converter that can be shut down. The method monitors the grid voltage borne by the pre-shutdown bridge arm after each bridge arm enters the trigger period, and issues a shutdown command at the zero-crossing point of the grid voltage, thereby making full use of the commutation capacity provided by the grid to ensure resistance to commutation failure.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] In a first aspect, a shutdown control method of a shut-down grid-commutated converter is provided, wherein the shut-down grid-commutated converter comprises a converter transformer and a converter valve, the converter valve comprises a plurality of bridge arms, the bridge arm comprises an IGCT, and the shutdown control method comprises:

[0007] Collect the three-phase AC voltage on the grid side of the converter transformer, and calculate the commutation voltage of each bridge arm of the converter valve according to the collected three-phase AC voltage;

[0008] After the pre-opening bridge arm enters the triggering period, it starts to monitor the commutation voltage of the corresponding pre-closing bridge arm, and judges whether the grid commutation capacity has reached the limit based on the commutation voltage of the pre-closing bridge arm. If the grid commutation capacity has reached the limit, an active shutdown command is sent to the pre-closing bridge arm.

[0009] Further,

[0010] The method of calculating the switching voltage of each bridge arm of the converter valve according to the collected three-phase AC voltage includes:

[0011] [(u A -u B ) / k] is obtained by phase compensation to obtain u1;

[0012] [(u A -u C ) / k] is obtained by phase compensation to obtain u2;

[0013] [(u B -u C ) / k] is obtained by phase compensation to obtain u3;

[0014] [(u B -u A ) / k] is obtained by phase compensation to obtain u4;

[0015] [(u C -u A ) / k] is obtained by phase compensation to obtain u5;

[0016] [(u C -u B ) / k] is obtained by phase compensation to obtain u6;

[0017] Among them, u1~u6 are the commutation voltages of bridge arm 1~bridge arm 6, u A ~u C is the AC voltage on the grid side of the converter transformer, and k is the transformation ratio between the grid side voltage and the valve side voltage of the converter transformer.

[0018] Further,

[0019] The phase compensation is a phase compensation corresponding to the connection method of the converter transformer, including:

[0020] If the converter transformer connected to the bridge arm is Yy0 connection or Dd0 connection, there is no phase shift;

[0021] If the converter transformer connected to the bridge arm is Yd1 or Dy1 connected, the phase shift is 30°;

[0022] If the converter transformer connected to the bridge arm is Yd11 or Dy11 connected, the phase shift is 330°.

[0023] Further,

[0024] The criterion for judging whether the commutation capacity of the power grid has reached the limit according to the commutation voltage of the pre-shutdown bridge arm is:

[0025] The commutation voltage of the pre-shutdown bridge arm is greater than the preset value Uset;

[0026] The preset value Uset is selected according to the voltage level of the turn-off grid commutation converter and the number of series-connected IGCTs used in the bridge arm.

[0027] Further,

[0028] The shutdown control method further includes:

[0029] After the active shutdown command is sent to the pre-shutdown bridge arm, a first preset time is delayed, and after the delay, a trigger command is reissued to the pre-opening bridge arm.

[0030] Further,

[0031] The shutdown control method further includes:

[0032] Collect the three-phase AC current on the valve side of the converter transformer, and calculate the current of each bridge arm of the converter valve according to the collected three-phase AC current;

[0033] At the end of each bridge arm trigger period, read the current of the bridge arm within the second preset time before this moment. If the bridge arm current is less than the preset threshold value during this period, it means that the triggering of the power grid commutation converter that can be shut down is abnormal, and the issuance of the active shutdown command is prohibited at this time;

[0034] After the active shutdown is prohibited, if the above-mentioned triggering abnormal situation does not occur again within the third preset time, the issuance of the active shutdown instruction is resumed.

[0035] Further,

[0036] The method of calculating the current of each bridge arm of the converter valve according to the collected three-phase AC current includes:

[0037] i1=i A ;

[0038] i2=-i c ;

[0039] i3=i B ;

[0040] i4=-i A ;

[0041] i5=i C ;

[0042] i6=-i B ;

[0043] Among them, i1~i6 are the currents of bridge arm 1~bridge arm 6, and the current direction of i1~i6 is positive with the IGCT forward current direction. A ~i C is the AC current on the valve side of the converter transformer, i A ~iC The current direction is positive when it flows into the converter valve; each bridge arm takes the corresponding valve-side AC current according to the above formula only during its own triggering period, and the bridge arm current is set to 0 during the non-triggering period.

[0044] Further,

[0045] The second preset time is 1ms;

[0046] The preset threshold is 0.05pu;

[0047] The criterion for judging whether the shutdown grid commutation converter triggers abnormality and prohibits active shutdown is:

[0048] The current within 1ms before the end of the triggering period of any bridge arm of the grid-shutdown commutation converter is always less than 0.05pu.

[0049] In a second aspect, a shutdown control device for a shut-down grid-commutated converter is also provided, wherein the shut-down grid-commutated converter comprises a converter transformer and a converter valve, the converter valve comprises a plurality of bridge arms, the bridge arms comprise IGCT,

[0050] The shutdown control device comprises:

[0051] A voltage calculation unit is used to collect the three-phase AC voltage on the grid side of the converter transformer, and calculate the commutation voltage of each bridge arm of the converter valve according to the collected three-phase AC voltage;

[0052] The shutdown control unit is used to start monitoring the commutation voltage of the corresponding pre-shutdown bridge arm after the pre-opening bridge arm enters the trigger period, and judge whether the grid commutation capacity has reached the limit according to the commutation voltage of the pre-shutdown bridge arm. If the grid commutation capacity has reached the limit, an active shutdown command is sent to the pre-shutdown bridge arm.

[0053] Further,

[0054] The voltage calculation unit is specifically used to calculate the commutation voltage of bridge arm 1 to bridge arm 6, including:

[0055] [(u A -u B ) / k] is obtained by phase compensation to obtain u1;

[0056] [(u A -u C ) / k] is obtained by phase compensation to obtain u2;

[0057] [(u B -u C ) / k] is obtained by phase compensation to obtain u3;

[0058] [(u B -u A) / k] is obtained by phase compensation to obtain u4;

[0059] [(u C -u A ) / k] is obtained by phase compensation to obtain u5;

[0060] [(u C -u B ) / k] is obtained by phase compensation to obtain u6;

[0061] Among them, u1~u6 are the commutation voltages of bridge arm 1~bridge arm 6, u A ~u C is the AC voltage on the grid side of the converter transformer, and k is the transformation ratio between the grid side voltage and the valve side voltage of the converter transformer.

[0062] Further,

[0063] In the voltage calculation unit, the phase compensation is a phase compensation corresponding to the connection method of the converter transformer, including:

[0064] If the converter transformer connected to the bridge arm is Yy0 connection or Dd0 connection, there is no phase shift;

[0065] If the converter transformer connected to the bridge arm is Yd1 or Dyl, the phase shift is 30°;

[0066] If the converter transformer connected to the bridge arm is Yd11 or Dy11 connected, the phase shift is 330°.

[0067] Further,

[0068] In the shutdown control unit, the criterion for judging whether the commutation capacity of the power grid has reached the limit according to the commutation voltage of the pre-shutdown bridge arm is:

[0069] The commutation voltage of the pre-shutdown bridge arm is greater than the preset value Uset;

[0070] The preset value Uset is selected according to the voltage level of the turn-off grid commutation converter and the number of series-connected IGCTs used in the bridge arm.

[0071] Further,

[0072] The shutdown control device also includes:

[0073] The delay trigger module is used to delay for a first preset time after sending an active shutdown instruction to the pre-shutdown bridge arm, and resend a trigger instruction to the pre-opening bridge arm after the delay ends.

[0074] Further,

[0075] The shutdown control device further includes a current calculation unit and a shutdown protection unit, wherein the shutdown protection unit includes a shutdown prohibition module and a shutdown recovery module;

[0076] The current calculation unit is used to collect the three-phase AC current on the valve side of the converter transformer, and calculate the current of each bridge arm of the converter valve according to the collected three-phase AC current;

[0077] The shutdown prohibition module is used to read the current of the bridge arm within the second preset time before each bridge arm trigger period at the end of the time. If the bridge arm current is less than the preset threshold value during this time, it means that the triggering of the grid commutation converter that can be shut down is abnormal, and the issuance of the active shutdown instruction is prohibited at this time;

[0078] The shutdown recovery module is used to resume the issuance of the active shutdown instruction if the above-mentioned triggering abnormal situation does not occur again within a third preset time after the active shutdown is prohibited.

[0079] Further,

[0080] The current calculation unit is specifically used to calculate the current of bridge arm 1 to bridge arm 6, including:

[0081] i1=i A ;

[0082] i2=-i c ;

[0083] i3=i B ;

[0084] i4=-i A ;

[0085] i5=i C ;

[0086] i6=-i B ;

[0087] Among them, i1~i6 are the currents of bridge arm 1~bridge arm 6, and the current direction of i1~i6 is positive with the IGCT forward current direction. A ~i C is the AC current on the valve side of the converter transformer, i A ~i C The current direction is positive when it flows into the converter valve; each bridge arm takes the corresponding valve-side AC current according to the above formula only during its own triggering period, and the bridge arm current is set to 0 during the non-triggering period.

[0088] Further,

[0089] In the shutdown inhibition module,

[0090] The second preset time is 1ms;

[0091] The preset threshold is 0.05pu;

[0092] The criterion for judging whether the shutdown grid commutation converter triggers abnormality and prohibits active shutdown is:

[0093] The current within 1ms before the end of the triggering period of any bridge arm of the grid-shutdown commutation converter is always less than 0.05pu.

[0094] Based on the same inventive concept, the present invention also provides a computer-readable storage medium storing one or more programs, which, when executed, can implement the aforementioned shutdown control method of the shutoff grid-commutated converter.

[0095] Based on the same inventive concept, the present invention also provides an electronic device, including a processor, a communication interface, the aforementioned computer-readable storage medium and a communication bus; wherein the processor, the communication interface, and the computer-readable storage medium communicate with each other via the communication bus; and the processor is used to execute the program stored in the computer-readable storage medium.

[0096] Compared with the prior art, the present invention has the following beneficial effects:

[0097] 1. By monitoring the grid voltage borne by the pre-shutdown bridge arm after each bridge arm enters the trigger period (i.e. monitoring the commutation voltage of the corresponding pre-shutdown bridge arm), a shutdown command is issued at the zero-crossing point of the grid voltage (i.e. when the grid commutation capacity reaches the limit), thereby making full use of the commutation capacity provided by the grid to ensure resistance to commutation failure;

[0098] 2. After each active shutdown, an additional trigger pulse is sent to the pre-opened bridge arm, and the triggering status of the bridge arm is monitored to avoid DC power congestion caused by forced current cut-off;

[0099] 3. The real-time values ​​of the AC voltage on the grid side of the converter transformer are subtracted from each other to perform transformation ratio conversion, and then the phase compensation corresponding to the connection method of the converter transformer is performed to obtain the commutation voltage of each bridge arm, which can provide a basis for subsequent judgment.

[0100] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings.

[0101] The present invention will be further described below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0103] Figure 1 A schematic flow chart of a shutdown control method for a power grid phase-commutation converter that can be shut down according to an embodiment of the present invention;

[0104] Figure 2 A schematic diagram of a topology principle of a grid-commutation converter capable of shutting down an embodiment of the present invention;

[0105] Figure 3 A control block diagram of a shutdown control method for a power grid commutation converter that can be shut down according to an embodiment of the present invention;

[0106] Figure 4 A schematic diagram of an action waveform principle of a shutdown control method for shutting down a grid-commutated converter according to an embodiment of the present invention;

[0107] Figure 5 A schematic diagram of a structure of a shutdown control device capable of shutting down a grid-commutated converter according to an embodiment of the present invention;

[0108] Figure 6 The figure is a schematic diagram of an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0109] In order to make the purpose, technical solution and advantages of the implementation of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0110] like Figure 1-4 As shown, the first embodiment of the present invention provides a shutdown control method for a shut-down grid-commutated converter, wherein the shut-down grid-commutated converter includes a converter transformer and a converter valve, the converter valve includes a plurality of bridge arms, the bridge arm includes an IGCT, and the shutdown control method includes:

[0111] Collect the three-phase AC voltage on the grid side of the converter transformer, and calculate the commutation voltage of each bridge arm of the converter valve according to the collected three-phase AC voltage;

[0112] After the pre-opening bridge arm enters the triggering period, it starts to monitor the commutation voltage of the corresponding pre-closing bridge arm, and judges whether the grid commutation capacity has reached the limit based on the commutation voltage of the pre-closing bridge arm. If the grid commutation capacity has reached the limit, an active shutdown command is sent to the pre-closing bridge arm.

[0113] In the above technical scheme, by collecting the three-phase AC voltage on the grid side of the converter transformer, the commutation voltage of each bridge arm of the converter valve can be calculated, thereby providing a basis for subsequent judgment. By monitoring the grid voltage borne by the pre-shutdown bridge arm after each bridge arm enters the trigger period (i.e. monitoring the commutation voltage of the corresponding pre-shutdown bridge arm), a shutdown command is issued at the zero-crossing point of the grid voltage (i.e. when the grid commutation capacity reaches the limit), thereby making full use of the commutation capacity provided by the grid to ensure resistance to commutation failure.

[0114] In view of the problems existing in the prior art, the embodiments of the present invention adopt a new IGCT switch device that can be actively turned on and off to replace the thyristor in the LCC, so as to form a turnable grid-commutated converter (HCC). Under the premise of keeping the original converter topology and commutation principle unchanged, the ability of active shutdown to complete commutation can be increased, thereby achieving resistance to commutation failure and improving the safety, stability and grid-friendliness of high-voltage direct current transmission.

[0115] Actively shutting down the bridge arm that is conducting and forcing the current to commutate to the next bridge arm will cause overvoltage at the moment of shutting down, increasing the working stress of the converter valve. Therefore, the shut-down grid-commutation converter of the embodiment of the present invention should try to work in the same commutation mode as the original LCC when the grid voltage is normal, and use the grid voltage to make the current naturally commutate between the bridge arms to avoid the overvoltage stress caused by active shutdown; and when the grid voltage is abnormal, causing the converter to be unable to complete the natural commutation, active shutdown should intervene in time to ensure that the converter valve maintains commutation in the correct phase sequence and passes through the abnormal process of the grid voltage.

[0116] Figure 2 The topological principle diagram of the control object of the shutdown control method of the present invention, namely, the shutdown grid commutation converter (HCC), in which the converter valve, converter transformer, and u A ~u C 、i A ~i C The grid-shutdown commutation converter described above belongs to the prior art, and its specific topology and principle can be further referred to the prior art, which will not be described in detail here.

[0117] As a preferred technical solution, the calculation of the switching voltage of each bridge arm of the converter valve according to the collected three-phase AC voltage includes:

[0118] [(u A -uB ) / k] is obtained by phase compensation to obtain u1;

[0119] [(u A -u C ) / k] is obtained by phase compensation to obtain u2;

[0120] [(u B -u C ) / k] is obtained by phase compensation to obtain u3;

[0121] [(u B -u A ) / k] is obtained by phase compensation to obtain u4;

[0122] [(u C -u A ) / k] is obtained by phase compensation to obtain u5;

[0123] [(u C -u B ) / k] is obtained by phase compensation to obtain u6;

[0124] Among them, u1~u6 are the commutation voltages of bridge arm 1~bridge arm 6, u A ~u C is the AC voltage on the grid side of the converter transformer, and k is the transformation ratio between the grid side voltage and the valve side voltage of the converter transformer.

[0125] In this embodiment, the commutation voltage of each bridge arm of the converter valve is obtained by the grid-side voltage of the converter transformer through transformation ratio conversion and phase compensation; specifically, the real-time values ​​of the grid-side AC voltage are subtracted from each other and then the transformation ratio is converted, and then the phase compensation corresponding to the connection method of the converter transformer is performed to obtain the commutation voltage of each bridge arm. The condition for the establishment of this method is that the commutation voltage of the pre-closed bridge arm is only used during the pre-opened bridge arm trigger period.

[0126] As a preferred technical solution, the phase compensation is a phase compensation corresponding to the connection method of the converter transformer, including:

[0127] If the converter transformer connected to the bridge arm is Yy0 connection or Dd0 connection, there is no phase shift;

[0128] If the converter transformer connected to the bridge arm is Yd1 or Dy1 connected, the phase shift is 30°;

[0129] If the converter transformer connected to the bridge arm is Yd11 or Dy11 connected, the phase shift is 330°.

[0130] In this embodiment, according to the working principle of the power transformer, if the converter transformer connected to the bridge arm is of Yy0 connection or Dd0 connection, no phase shift is performed; if the converter transformer connected to the bridge arm is of Yd1 connection or Dy1 connection, the grid-side voltage is phase shifted by 30° (for a 50Hz system, a delay of 1.666667ms); if the converter transformer connected to the bridge arm is of Yd11 connection or Dy11 connection, the grid-side voltage is phase shifted by 330° (for a 50Hz system, a delay of 18.333333ms).

[0131] As a preferred technical solution, the criterion for judging whether the commutation capacity of the power grid has reached the limit according to the commutation voltage of the pre-shutdown bridge arm is:

[0132] The commutation voltage of the pre-shutdown bridge arm is greater than the preset value Uset;

[0133] The preset value Uset is selected according to the voltage level of the turn-off grid commutation converter and the number of series-connected IGCTs used in the bridge arm.

[0134] In this embodiment, the specific criterion for judging whether the commutation capacity of the power grid has reached the limit according to the commutation voltage is: the commutation voltage of the pre-shutdown bridge arm is greater than a certain fixed value Uset (i.e., the preset value Uset), which is selected according to the voltage level of the converter and the number of series-connected IGCT devices used in the bridge arm, and can generally be obtained by accumulating -50V per IGCT device. The following example illustrates that, assuming that bridge arm 1 is composed of 20 IGCTs connected in series, when it is detected that u1>-1000V=(-50V*20), it is considered that bridge arm 1 has reached the limit of the commutation capacity of the power grid.

[0135] As a preferred technical solution, the shutdown control method further includes:

[0136] After the active shutdown command is sent to the pre-shutdown bridge arm, a first preset time is delayed, and after the delay, a trigger command is reissued to the pre-opening bridge arm.

[0137] Since the sending end always maintains DC power feeding, when a bridge arm of the receiving end converter valve actively shuts off the current, if the corresponding pre-opening bridge arm fails to open normally, the fed-in power will be accumulated in the DC system, causing overvoltage of the DC system and energy accumulation of local equipment, which seriously endangers the safety of the system and equipment. Therefore, the active shutdown of the converter valve also needs to be closely coordinated with the trigger function to prevent unsafe shutdown behavior; in this embodiment, after the active shutdown command is issued to the pre-shutdown bridge arm, a trigger command is quickly issued to the pre-opening bridge arm (i.e., after the first preset time is delayed), which can further ensure the safety of the shutdown action. The specific execution method is: after the active shutdown command is issued to the pre-shutdown bridge arm, a certain time (i.e., the first preset time) is delayed, and a trigger command is issued to the pre-opening bridge arm after the delay. The delay time is set considering the issuance and execution speed deviation of the trigger / shutdown command of different bridge arms, and the value can generally be 100~200μs.

[0138] As a preferred technical solution, the shutdown control method further includes:

[0139] Collect the three-phase AC current on the valve side of the converter transformer, and calculate the current of each bridge arm of the converter valve according to the collected three-phase AC current;

[0140] At the end of each bridge arm trigger period, read the current of the bridge arm within the second preset time before this moment. If the bridge arm current is less than the preset threshold value during this period, it means that the triggering of the power grid commutation converter that can be shut down is abnormal, and the issuance of the active shutdown command is prohibited at this time;

[0141] After the active shutdown is prohibited, if the above-mentioned triggering abnormal situation does not occur again within the third preset time, the issuance of the active shutdown instruction is resumed.

[0142] In this embodiment, the current of each bridge arm of the converter valve can be calculated by collecting the three-phase AC current on the valve side of the converter transformer, thereby providing a basis for subsequent judgment. By setting the second preset time and the preset threshold, it is convenient to judge whether the converter triggers an abnormality based on the bridge arm current, and prohibit active shutdown when the abnormality is triggered. Whether to restore active shutdown is determined by judging whether the converter has no triggered abnormality for consecutive times.

[0143] In some embodiments, the specific criterion for judging whether the converter has continuously recovered from active shutdown without triggering abnormalities is that all bridge arms of the converter have no situation satisfying the aforementioned triggering abnormality criterion within 1 hour (i.e., the third preset time), wherein the time value of 1 hour is mainly selected based on the energy discharge speed of the converter valve bridge arm lightning arrester after the triggering abnormality causes the forced shutdown current.

[0144] As a preferred technical solution, the method of calculating the current of each bridge arm of the converter valve according to the collected three-phase AC current includes:

[0145] i1=iA ;

[0146] i2=-i c ;

[0147] i3=i B ;

[0148] i4=-i A ;

[0149] i5=i C ;

[0150] i6=-i B ;

[0151] Among them, i1~i6 are the currents of bridge arm 1~bridge arm 6, and the current direction of i1~i6 is positive with the IGCT forward current direction. A ~i C is the AC current on the valve side of the converter transformer, i A ~i C The current direction is positive when it flows into the converter valve; each bridge arm takes the corresponding valve-side AC current according to the above formula only during its own triggering period, and the bridge arm current is set to 0 during the non-triggering period.

[0152] The following example illustrates the calculation of the above bridge arm current. Figure 2 In the topology shown, when bridge arm 1 is triggered and bridge arm 4 is turned off, i1 = i A , i4=0; when bridge arm 1 is turned off and bridge arm 4 is triggered, i1=0, i4=-i A ; If neither bridge arm 1 nor bridge arm 4 is triggered, then i1=i4=0; when the converter operates normally, there is no situation where both bridge arm 1 and bridge arm 4 are triggered.

[0153] As a preferred technical solution, the second preset time is 1ms; the preset threshold is 0.05pu; and the criterion for judging whether the shutdown grid commutation converter triggers an abnormality and prohibits active shutdown is:

[0154] The current within 1ms before the end of the triggering period of any bridge arm of the grid-shutdown commutation converter is always less than 0.05pu.

[0155] The 1ms window time is selected mainly to prevent misjudgment, and the 0.05pu constant is selected mainly to be less than the minimum operating current of the DC system (generally 0.1pu). When the off-grid commutation converter is operating normally, the minimum operating current within 1ms before the end of the bridge arm trigger period is 0.1pu. If the actual current is less than this value, it can be considered that the bridge arm is abnormally triggered. Here, <0.05pu is used as the judgment criterion.

[0156] In summary, the present invention further provides a shutdown control method for a power-supply-able power grid-commutated converter as a preferred embodiment, and the shutdown control method comprises the following steps:

[0157] (1) Collecting the three-phase AC voltage on the grid side of the converter transformer, and calculating the commutation voltage of each bridge arm of the converter valve based on the collected three-phase AC voltage;

[0158] (2) collecting the three-phase AC current on the valve side of the converter transformer, and calculating the current of each bridge arm of the converter valve based on the collected three-phase AC current;

[0159] (3) After the pre-opening bridge arm enters the triggering period, the commutation voltage of the corresponding pre-closing bridge arm begins to be monitored. When the commutation voltage determines that the grid commutation capacity has reached its limit (i.e., when the commutation voltage indicates that the grid commutation capacity has reached its limit), an active shutdown command is issued to the pre-closing bridge arm;

[0160] (4) After the active shutdown command is issued, a trigger command is quickly issued to the pre-opened bridge arm (i.e., after a delay of the first preset time);

[0161] (5) At the end of each bridge arm triggering period, read the current of the bridge arm within a period of time before this moment (i.e., the second preset time). If the bridge arm current during this period is less than a certain value (i.e., the preset threshold), it means that the converter triggering is abnormal, and the issuance of active shutdown instructions is prohibited at this time; after the active shutdown is prohibited, if the above-mentioned triggering abnormality does not occur again within a continuous period of time (i.e., the third preset time), the issuance of active shutdown instructions can be restored.

[0162] In the above technical solution, by monitoring the grid voltage borne by the pre-shutdown bridge arm after each bridge arm enters the trigger period, a shutdown command is issued at the zero-crossing point of the grid voltage, thereby making full use of the commutation capacity provided by the grid to ensure resistance to commutation failure. At the same time, after each active shutdown is performed, an additional trigger pulse is sent to the pre-open bridge arm, and the triggering status of the bridge arm is monitored to avoid DC power congestion caused by forced current cutoff. In the above steps, steps (1) and (3) are used to realize the basic shutdown function, and steps (2), (4) and (5) are based on the basic scheme of steps (1) and (3) to further ensure the safety of the shutdown action.

[0163] In order to make the shutdown control method of the grid-commutated converter that can be shut down according to the embodiment of the present invention clearer, it will be further explained below in conjunction with the control block diagram and the action waveform principle diagram.

[0164] Figure 3 : is a control block diagram of the shutdown control method of an embodiment of the present invention. The control function is executed at the valve control level of the converter valve and is controlled by the pole control trigger instruction. CPi is the trigger instruction of the i-th bridge arm issued by the pole control, and its value is 1, indicating that the bridge arm i is in the trigger period.A ~u C 、u1~u6、i A ~i C The definitions of i1-i6, Uset, and Delay are as described in the above-mentioned technical solution of the invention. The shut-off pulse i and the supplementary trigger pulse i are the shut-off and trigger pulse signals that the valve control finally sends to the i-th bridge arm of the converter valve.

[0165] Figure 3 In the figure, the dotted line frame part describes the logic block diagram when the i-th bridge arm executes the shutdown control method of the present invention. The dotted line means that there are 6 sets of the same logic, one set for each bridge arm, and the internal logic is the same. (i-2) Represents the voltage of the i-2nd bridge arm. This representation is used here because when the i-th CP signal of the pole control is received, the i-2nd bridge arm is shut down and the i-th bridge arm is triggered. For example: when the CP3 instruction arrives, bridge arm 3 will be triggered and bridge arm 1 will be shut down. After bridge arm 1 is shut down, bridge arm 3 will be triggered once.

[0166] The pole control sends the control instructions of CP1 to CP12 to the valve control. After receiving the pole control instructions, the valve control sends the trigger pulse and the shut-off pulse (instruction) to the converter valve. The converter valve performs the triggering when receiving the trigger pulse of the valve control, and performs the shut-off when receiving the shut-off pulse of the valve control. In this embodiment, the pole control is a pole control device, which can be a chassis, connected to the valve control device through optical fiber; the valve control is a valve control device, which can be a chassis, connected to the pole control device through optical fiber, and connected to the converter valve through optical fiber.

[0167] Figure 4 The schematic diagram of the action waveform of the shutdown control method of the present invention shows the process of active shutdown of bridge arm 1 to prevent commutation failure when the voltage disturbance of phase A on the grid side causes commutation abnormality. A ~u C , u1, i1, i3, i5, CP1, CP3 and CP5 are defined as in the above invention technical solution and Figure 3 α is the trigger angle of bridge arm 3, and the end time of the trigger angle corresponds to the time when i1 starts to decrease and i3 starts to increase; Pon1, Pon3, and Pon5 are the trigger pulses (including the supplementary trigger pulses) sent by the valve control to bridge arms 1, 3, and 5 respectively; Poff1, Poff3, and Poff5 are the active shut-off pulses sent by the valve control to bridge arms 1, 3, and 5 respectively.

[0168] It should be noted that Figure 4Emphasis is placed on the shutdown process of bridge arm 1, and the process of bridge arms 2 to 6 is the same; the waveforms of bridge arms 3 and 5 are also drawn in the figure because the waveforms of 1, 3, and 5 do not conflict with each other, and by drawing them we can clearly see the process of each bridge arm executing the shutdown in turn; the waveforms of bridge arms 2, 4, and 6 are the same as those of bridge arms 1, 3, and 5, and if they are drawn together they will overlap and be unclear, so they are not drawn.

[0169] In summary, the shutdown control method provided by the embodiment of the present invention can effectively realize the shutdown control of the shutdown grid-commutated converter:

[0170] When the grid voltage is normal and the grid commutation can be completed naturally, the method will issue an additional shutdown command after the bridge arm is naturally shut down, which will not affect the original commutation process and device stress; when the shutdown control method of the embodiment of the present invention is not adopted, the control is performed according to the traditional grid commutation converter (LCC), and the valve control will not send a shutdown pulse to the converter valve, and the converter valve depends entirely on the natural shutdown of the converter valve with the grid voltage. After adopting this method, in addition to the natural shutdown, the valve control will also issue an active shutdown after the voltage passes through zero.

[0171] When the grid voltage is abnormally insufficient to complete grid commutation, this method will promptly issue an active shutdown after the grid commutation process reaches its limit, which not only fully utilizes the grid's commutation capacity, but also ensures that the shutdown will be completed in each cycle, thereby achieving resistance to commutation failure.

[0172] At the same time, the method also achieves effective detection of abnormal triggering of the converter valve, and promptly prohibits active shutdown when an abnormal triggering occurs, thereby preventing DC power congestion and equipment damage caused by forced current cutoff when there is a triggering problem inside the converter valve.

[0173] like Figure 5 As shown, the second embodiment of the present invention further provides a shutdown control device for a shut-down grid-commutated converter, wherein the shut-down grid-commutated converter comprises a converter transformer and a converter valve, the converter valve comprises a plurality of bridge arms, the bridge arms comprise IGCT,

[0174] The shutdown control device comprises:

[0175] A voltage calculation unit is used to collect the three-phase AC voltage on the grid side of the converter transformer, and calculate the commutation voltage of each bridge arm of the converter valve according to the collected three-phase AC voltage;

[0176] The shutdown control unit is used to start monitoring the commutation voltage of the corresponding pre-shutdown bridge arm after the pre-opening bridge arm enters the trigger period, and judge whether the grid commutation capacity has reached the limit according to the commutation voltage of the pre-shutdown bridge arm. If the grid commutation capacity has reached the limit, an active shutdown command is sent to the pre-shutdown bridge arm.

[0177] As a preferred technical solution, the voltage calculation unit is specifically used to calculate the commutation voltage of bridge arm 1 to bridge arm 6, including:

[0178] [(u A -u B ) / k] is obtained by phase compensation to obtain u1;

[0179] [(u A -u C ) / k] is obtained by phase compensation to obtain u2;

[0180] [(u B -u C ) / k] is obtained by phase compensation to obtain u3;

[0181] [(u B -u A ) / k] is obtained by phase compensation to obtain u4;

[0182] [(u C -u A ) / k] is obtained by phase compensation to obtain u5;

[0183] [(u C -u B ) / k] is obtained by phase compensation to obtain u6;

[0184] Among them, u1~u6 are the commutation voltages of bridge arm 1~bridge arm 6, u A ~u C is the AC voltage on the grid side of the converter transformer, and k is the transformation ratio between the grid side voltage and the valve side voltage of the converter transformer.

[0185] As a preferred technical solution, in the voltage calculation unit, the phase compensation is a phase compensation corresponding to the connection method of the converter transformer, including:

[0186] If the converter transformer connected to the bridge arm is Yy0 connection or Dd0 connection, there is no phase shift;

[0187] If the converter transformer connected to the bridge arm is Yd1 or Dy1 connected, the phase shift is 30°;

[0188] If the converter transformer connected to the bridge arm is Yd11 or Dy11 connected, the phase shift is 330°.

[0189] As a preferred technical solution, in the shutdown control unit, the criterion for judging whether the commutation capacity of the power grid has reached the limit according to the commutation voltage of the pre-shutdown bridge arm is:

[0190] The commutation voltage of the pre-shutdown bridge arm is greater than the preset value Uset;

[0191] The preset value Uset is selected according to the voltage level of the turn-off grid commutation converter and the number of series-connected IGCTs used in the bridge arm.

[0192] As a preferred technical solution, the shutdown control device further includes:

[0193] The delay trigger module is used to delay for a first preset time after sending an active shutdown instruction to the pre-shutdown bridge arm, and resend a trigger instruction to the pre-opening bridge arm after the delay ends.

[0194] As a preferred technical solution,

[0195] The shutdown control device further includes a current calculation unit and a shutdown protection unit, wherein the shutdown protection unit includes a shutdown prohibition module and a shutdown recovery module;

[0196] The current calculation unit is used to collect the three-phase AC current on the valve side of the converter transformer, and calculate the current of each bridge arm of the converter valve according to the collected three-phase AC current;

[0197] The shutdown prohibition module is used to read the current of the bridge arm within the second preset time before each bridge arm trigger period at the end of the time. If the bridge arm current is less than the preset threshold value during this time, it means that the triggering of the grid commutation converter that can be shut down is abnormal, and the issuance of the active shutdown instruction is prohibited at this time;

[0198] The shutdown recovery module is used to resume the issuance of the active shutdown instruction if the above-mentioned triggering abnormal situation does not occur again within a third preset time after the active shutdown is prohibited.

[0199] As a preferred technical solution, the current calculation unit is specifically used to calculate the current of bridge arm 1 to bridge arm 6, including:

[0200] i1=i A ;

[0201] i2=-i c ;

[0202] i3=i B ;

[0203] i4=-i A ;

[0204] i5=i C ;

[0205] i6=-i B ;

[0206] Among them, i1~i6 are the currents of bridge arm 1~bridge arm 6, and the current direction of i1~i6 is positive with the IGCT forward current direction. A ~i Cis the AC current on the valve side of the converter transformer, i A ~i C The current direction is positive when it flows into the converter valve; each bridge arm takes the corresponding valve-side AC current according to the above formula only during its own triggering period, and the bridge arm current is set to 0 during the non-triggering period.

[0207] As a preferred technical solution, in the shutdown prohibition module,

[0208] The second preset time is 1ms;

[0209] The preset threshold is 0.05pu;

[0210] The criterion for judging whether the shutdown grid commutation converter triggers abnormality and prohibits active shutdown is:

[0211] The current within 1ms before the end of the triggering period of any bridge arm of the grid-shutdown commutation converter is always less than 0.05pu.

[0212] Regarding the device in the above embodiment, the specific manner in which each unit module performs the operation has been described in detail in the embodiment of the method, and will not be elaborated here.

[0213] Based on the same inventive concept, the present invention also provides a computer-readable storage medium storing one or more programs, which, when executed, can implement the aforementioned shutdown control method of the shutoff grid-commutated converter.

[0214] Based on the same inventive concept, Figure 6 As shown, the present invention also provides an electronic device, including a processor, a communication interface, the aforementioned computer-readable storage medium and a communication bus; wherein the processor, the communication interface, and the computer-readable storage medium communicate with each other via the communication bus; and the processor is used to execute the program stored in the computer-readable storage medium.

[0215] The specific implementation method and specific criteria mentioned in the present invention are only a specific implementation method of the invention. All specific active shutdown implementation schemes based on the measurement means and commutation principle involved in the present invention should be within the protection scope of the claims of the invention.

[0216] It should be noted that, for the convenience of description, the aforementioned method embodiments are all described as a series of action combinations, but those skilled in the art should be aware that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present invention.

[0217] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0218] Parts not involved in the above embodiments are the same as the prior art or can be implemented by using the prior art, and will not be further described here.

[0219] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A shutdown control method for a power grid-commutation converter, wherein: The switchable grid-commutation converter comprises a converter transformer and a converter valve, wherein the converter valve comprises a plurality of bridge arms, wherein the bridge arms comprise IGCT, and is characterized in that: The shutdown control method comprises: Collect the three-phase AC voltage on the grid side of the converter transformer, and calculate the commutation voltage of each bridge arm of the converter valve according to the collected three-phase AC voltage; After the pre-opening bridge arm enters the triggering period, it starts to monitor the commutation voltage of the corresponding pre-closing bridge arm, and judges whether the grid commutation capacity has reached the limit based on the commutation voltage of the pre-closing bridge arm. If the grid commutation capacity has reached the limit, an active shutdown command is sent to the pre-closing bridge arm.

2. A shutdown control method for a shut-down grid-commutated converter according to claim 1, characterized in that: The method of calculating the switching voltage of each bridge arm of the converter valve according to the collected three-phase AC voltage includes: [(u A -u B ) / k] is obtained by phase compensation to obtain u1; [(u A -u C ) / k] is obtained by phase compensation to obtain u2; [(u B -u C ) / k] is obtained by phase compensation to obtain u3; [(u B -u A ) / k] is obtained by phase compensation to obtain u4; [(u C -u A ) / k] is obtained by phase compensation to obtain u5; [(u C -u B ) / k] is obtained by phase compensation to obtain u6; Among them, u1~u6 are the commutation voltages of bridge arm 1~bridge arm 6, u A ~u C is the AC voltage on the grid side of the converter transformer, and k is the transformation ratio between the grid side voltage and the valve side voltage of the converter transformer.

3. A shutdown control method for a shut-down grid-commutated converter according to claim 2, characterized in that: The phase compensation is a phase compensation corresponding to the connection method of the converter transformer, including: If the converter transformer connected to the bridge arm is Yy0 connection or Dd0 connection, there is no phase shift; If the converter transformer connected to the bridge arm is Yd1 or Dy1 connected, the phase shift is 30°; If the converter transformer connected to the bridge arm is Yd11 or Dy11 connected, the phase shift is 330°.

4. A shutdown control method for a shut-down grid-commutated converter according to claim 1, characterized in that: The criterion for judging whether the commutation capacity of the power grid has reached the limit according to the commutation voltage of the pre-shutdown bridge arm is: The commutation voltage of the pre-shutdown bridge arm is greater than the preset value Uset; The preset value Uset is selected according to the voltage level of the turn-off grid commutation converter and the number of series-connected IGCTs used in the bridge arm.

5. A shutdown control method for a shut-down grid-commutated converter according to any one of claims 1 to 4, characterized in that: The shutdown control method further includes: After the active shutdown command is sent to the pre-shutdown bridge arm, a first preset time is delayed, and after the delay, a trigger command is reissued to the pre-opening bridge arm.

6. A shutdown control method for a shut-down grid-commutated converter according to claim 5, characterized in that: The shutdown control method further includes: Collect the three-phase AC current on the valve side of the converter transformer, and calculate the current of each bridge arm of the converter valve according to the collected three-phase AC current; At the end of each bridge arm trigger period, read the current of the bridge arm within the second preset time before this moment. If the bridge arm current is less than the preset threshold value during this period, it means that the triggering of the power grid commutation converter that can be shut down is abnormal, and the issuance of the active shutdown command is prohibited at this time; After the active shutdown is prohibited, if the above-mentioned triggering abnormal situation does not occur again within the third preset time, the issuance of the active shutdown instruction is resumed.

7. A shutdown control method for a shut-down grid-commutated converter according to claim 6, characterized in that: The method of calculating the current of each bridge arm of the converter valve according to the collected three-phase AC current includes: i1=i A ; i2=-i c ; i3=i B ; i4=-i A ; i5=i C ; i6=-i B ; Among them, i1~i6 are the currents of bridge arm 1~bridge arm 6, and the current direction of i1~i6 is positive with the IGCT forward current direction. A ~i C is the AC current on the valve side of the converter transformer, i A ~i C The current direction is positive when it flows into the converter valve; each bridge arm takes the corresponding valve-side AC current according to the above formula only during its own triggering period, and the bridge arm current is set to 0 during the non-triggering period.

8. A shutdown control method for a shut-down grid-commutated converter according to claim 6, characterized in that: The second preset time is 1ms; The preset threshold is 0.05pu; The criterion for judging whether the shutdown grid commutation converter triggers abnormality and prohibits active shutdown is: The current within 1ms before the end of the triggering period of any bridge arm of the grid-shutdown commutation converter is always less than 0.05pu.

9. A shutdown control device capable of shutting down a grid-commutated converter, wherein: The switchable grid-commutation converter comprises a converter transformer and a converter valve, wherein the converter valve comprises a plurality of bridge arms, wherein the bridge arms comprise IGCT, and is characterized in that: The shutdown control device comprises: A voltage calculation unit is used to collect the three-phase AC voltage on the grid side of the converter transformer, and calculate the commutation voltage of each bridge arm of the converter valve according to the collected three-phase AC voltage; The shutdown control unit is used to start monitoring the commutation voltage of the corresponding pre-shutdown bridge arm after the pre-opening bridge arm enters the trigger period, and judge whether the grid commutation capacity has reached the limit according to the commutation voltage of the pre-shutdown bridge arm. If the grid commutation capacity has reached the limit, an active shutdown command is sent to the pre-shutdown bridge arm.

10. A shutdown control device for a shutdown grid-commutated converter according to claim 9, characterized in that: The voltage calculation unit is specifically used to calculate the commutation voltage of bridge arm 1 to bridge arm 6, including: [(u A -u B ) / k] is obtained by phase compensation to obtain u1; [(u A -u C ) / k] is obtained by phase compensation to obtain u2; [(u B -u C ) / k] is obtained by phase compensation to obtain u3; [(u B -u A ) / k] is obtained by phase compensation to obtain u4; [(u C -u A ) / k] is obtained by phase compensation to obtain u5; [(u C -u B ) / k] is obtained by phase compensation to obtain u6; Among them, u1~u6 are the commutation voltages of bridge arm 1~bridge arm 6, u A ~u C is the AC voltage on the grid side of the converter transformer, and k is the transformation ratio between the grid side voltage and the valve side voltage of the converter transformer.

11. A shutdown control device for a shutdown grid-commutated converter according to claim 10, characterized in that: In the voltage calculation unit, the phase compensation is a phase compensation corresponding to the connection method of the converter transformer, including: If the converter transformer connected to the bridge arm is Yy0 connection or Dd0 connection, there is no phase shift; If the converter transformer connected to the bridge arm is Yd1 or Dy1 connected, the phase shift is 30°; If the converter transformer connected to the bridge arm is Yd11 or Dy11 connected, the phase shift is 330°.

12. A shutdown control device for a shutdown grid-commutated converter according to claim 9, characterized in that: In the shutdown control unit, the criterion for judging whether the commutation capacity of the power grid has reached the limit according to the commutation voltage of the pre-shutdown bridge arm is: The commutation voltage of the pre-shutdown bridge arm is greater than the preset value Uset; The preset value Uset is selected according to the voltage level of the turn-off grid commutation converter and the number of series-connected IGCTs used in the bridge arm.

13. A shutdown control device for a shutdown grid-commutated converter according to any one of claims 9 to 12, characterized in that: The shutdown control device also includes: The delay trigger module is used to delay for a first preset time after sending an active shutdown instruction to the pre-shutdown bridge arm, and resend a trigger instruction to the pre-opening bridge arm after the delay ends.

14. A shutdown control device for a shutdown grid-commutated converter according to claim 13, characterized in that: The shutdown control device further includes a current calculation unit and a shutdown protection unit, wherein the shutdown protection unit includes a shutdown prohibition module and a shutdown recovery module; The current calculation unit is used to collect the three-phase AC current on the valve side of the converter transformer, and calculate the current of each bridge arm of the converter valve according to the collected three-phase AC current; The shutdown prohibition module is used to read the current of the bridge arm within the second preset time before each bridge arm trigger period at the end of the time. If the bridge arm current is less than the preset threshold value during this time, it means that the triggering of the grid commutation converter that can be shut down is abnormal, and the issuance of the active shutdown instruction is prohibited at this time; The shutdown recovery module is used to resume the issuance of the active shutdown instruction if the above-mentioned triggering abnormal situation does not occur again within a third preset time after the active shutdown is prohibited.

15. A shutdown control device for a shutdown grid-commutated converter according to claim 14, characterized in that: The current calculation unit is specifically used to calculate the current of bridge arm 1 to bridge arm 6, including: i1=i A ; i2=-i C ; i3=i B ; i4=-i A ; i5=i C ; i6=-i B ; Among them, i1~i6 are the currents of bridge arm 1~bridge arm 6, and the current direction of i1~i6 is positive with the IGCT forward current direction. A ~i C is the AC current on the valve side of the converter transformer, i A ~i C The current direction is positive when it flows into the converter valve; each bridge arm takes the corresponding valve-side AC current according to the above formula only during its own triggering period, and the bridge arm current is set to 0 during the non-triggering period.

16. A shutdown control device for a shutdown grid-commutated converter according to claim 14, characterized in that: In the shutdown inhibition module, The second preset time is 1ms; The preset threshold is 0.05pu; The criterion for judging whether the shutdown grid commutation converter triggers abnormality and prohibits active shutdown is: The current within 1ms before the end of the triggering period of any bridge arm of the grid-shutdown commutation converter is always less than 0.05pu.

17. A computer-readable storage medium storing one or more programs, characterized in that: When the one or more programs are executed, the shutdown control method of the shutoff grid-commutated converter described in any one of claims 1 to 8 can be implemented.

18. An electronic device comprising a processor, a communication interface, the computer-readable storage medium of claim 17, and a communication bus; wherein: The processor, the communication interface, and the computer-readable storage medium communicate with each other via a communication bus; It is characterized in that The processor is configured to execute a program stored in a computer-readable storage medium.

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