A filter switching selection control method and system for an open-close loop AC system

Abstract

The application relates to a switching selection control method and system of a split-ring AC system filter, priority initial values of input and removal sequences of each group of filters are set; when a group of filters needs to be selected to be input, a filter with the highest input priority in the filter in a state capable of being input is selected to be input, the input filter is set to have the lowest removal priority, and the removal priorities of other filters are improved by one level; when a group of filters needs to be selected to be removed, a filter with the highest removal priority in the filter in a state capable of being removed is selected to be input, the input filter is set to have the lowest input priority, and the input priorities of other filters are improved by one level. The application avoids the phenomenon that filters in a field are removed or input in a short time when an AC field bus tie circuit breaker is tripped and split-ring operation is switched from loop operation, avoids the situation that a certain AC filter is unavailable, loop operation mode cannot input or remove filters for reactive power control, and ensures normal operation of a DC system.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage direct current (HVDC) converter stations, and in particular to a switching selection control method and system for filters in an open-close loop alternating current (AC) system. Background Art

[0002] The split-loop and closed-loop operation modes of the AC system of a high-voltage DC converter station can be achieved through the open and closed states of the AC field busbar circuit breaker. The corresponding filter field also realizes unified control of all filters or is divided into two filter fields for independent control according to the busbar circuit breaker state. Due to some abnormal reasons, the AC system and filter field may passively switch from closed-loop operation to split-loop operation due to abnormal tripping of the busbar breaker. If the control method for selecting the switching of the sub-filter under the reactive power control function during closed-loop operation is not properly designed, the number of filters put into operation in the two filter fields after split-loop operation will be unbalanced. In the same time period, one filter field in the AC system will continuously remove multiple groups of filters due to excessive reactive power output, while another filter field in the AC system will continuously put multiple groups of filters into operation due to harmonic performance or reactive power output not meeting system requirements, thus affecting the stable operation of the system.

[0003] At present, the domestic research on how to achieve a balanced filter type and number in the two filter fields when the HVDC converter station split-loop AC system transitions from closed loop to split-loop based on the equal switching probability of each filter is still under research and discussion. Summary of the Invention

[0004] The present invention provides a filter switching selection control method and system for a split-and-closed-loop AC system, which avoids the phenomenon of multiple switching on or off of the filter field in a short period of time when the AC field busbar circuit breaker trips and switches from closed-loop operation to split-loop operation; and the problem that a certain AC filter is unavailable, resulting in the inability to switch on or off the filter in the closed-loop operation mode due to reactive power control, thereby ensuring the normal operation of the DC system.

[0005] To achieve the above object, the present invention provides a switching selection control method for a filter in an open-close loop AC system, comprising:

[0006] Each busbar is equipped with two sets of parallel filters, and the busbars operate in a closed loop;

[0007] Set the initial priority value of the input and removal order for each group of filters of the same type;

[0008] When a group of filters need to be selected for use, the filter with the highest priority among the available filters is selected for use, and the removal priority of the filter is set to the lowest. The removal priority of other filters is increased by one level.

[0009] When a group of filters needs to be selected for removal, the filter with the highest removal priority among the filters in the removable state is selected and put into use, and the input priority of the filter is set to the lowest, and the input priority of other filters is increased by one level.

[0010] Furthermore, the priority of the initial values ​​of the order of input and removal of each group of filters is set from high to low as follows:

[0011] The first group of filters for busbar i, the first group of filters for busbars located in different AC fields from busbar i and connected through a bus coupler, the second group of filters for busbar i, the second group of filters for busbars located in different AC fields from busbar i and connected through a bus coupler, the first group of filters for busbars located in the same AC field as busbar i, the first group of filters for busbars located in different AC fields from busbar i and not connected through a bus coupler, the second group of filters for busbars located in the same AC field as busbar i, and the second group of filters for busbars located in different AC fields from busbar i and not connected through a bus coupler.

[0012] Furthermore, if the state of a certain filter is not available for engagement, the engagement priority is set to be infinitely low.

[0013] Furthermore, if the state of a certain filter changes from a non-engageable state to an engageable state, the engagement priority is set to the real-time value of the engagement priority of the current switching priority filter.

[0014] Furthermore, if the state of a certain filter is a non-removable state, the removal priority is set to be infinitely low.

[0015] Furthermore, if the state of a certain filter changes from a non-removable state to a removable state, the removal priority is set to the real-time value of the removal priority of the current removal priority filter.

[0016] Another aspect of the present invention provides a filter switching selection control system for an open-close ring AC system, comprising four busbars and a controller;

[0017] Each busbar is equipped with two sets of parallel filters, and the four buses operate in a ring;

[0018] The controller obtains or sets the initial priority value of the order of input and removal of each group of filters of the same type; when receiving a filter input instruction, the filter with the highest input priority among the filters in the input state is selected for input, and the removal priority of the input filter is set to the lowest, and the removal priority of other filters is increased by one level; when receiving a filter removal instruction to select a group of filters, the filter with the highest removal priority among the filters in the removable state is selected for input, and the input priority of the input filter is set to the lowest, and the input priority of other filters is increased by one level.

[0019] Furthermore, the priority of each group of filters in the order of input and removal is as follows from high to low:

[0020] The first group of filters for busbar i, the first group of filters for busbars located in different AC fields from busbar i and connected through a bus coupler, the second group of filters for busbar i, the second group of filters for busbars located in different AC fields from busbar i and connected through a bus coupler, the first group of filters for busbars located in the same AC field as busbar i, the first group of filters for busbars located in different AC fields from busbar i and not connected through a bus coupler, the second group of filters for busbars located in the same AC field as busbar i, and the second group of filters for busbars located in different AC fields from busbar i and not connected through a bus coupler.

[0021] Furthermore, the controller reads the status of the filter. If the status of a certain filter is not in an investable state, the controller sets the investment priority of the filter to infinitely low.

[0022] Furthermore, the controller reads the status of the filter. If the status of a filter changes from a non-engageable state to an engageable state, the controller sets the engagement priority of the filter to the real-time value of the engagement priority of the current switching priority filter.

[0023] Furthermore, the controller reads the status of the filter. If the status of a certain filter is a non-removable state, the controller sets the removal priority of the filter to infinitely low.

[0024] Furthermore, the controller reads the status of the filter. If the status of a filter changes from a non-removable state to a removable state, the controller sets the removal priority of the filter to the real-time value of the removal priority of the current switching priority filter.

[0025] The above technical solution of the present invention has the following beneficial technical effects:

[0026] (1) The present invention adopts a cross-balancing control method for switching priorities of filters of the same type to achieve a balance in the number of switching priorities of filters of the same type in two filter fields.

[0027] (2) The present invention proposes a method for selecting and controlling the switching on / off of a group of filters under closed-loop operation, thereby ensuring that when a certain AC filter is unavailable, the other available filters can be selected as the next group of filters to be switched on or off under reactive power control, thereby ensuring that when a certain AC filter is unavailable, the other available filters can be selected as the next group of filters to be switched on or off under reactive power control.

[0028] (3) The present invention avoids the problem that when the AC field busbar circuit breaker trips and switches from closed-loop operation to open-loop operation, the filter field may be cut off or put on multiple times in a short period of time, and a certain AC filter may be unavailable, resulting in the reactive power control in the closed-loop operation mode being unable to put in or cut off the filter, thereby ensuring the normal operation of the DC system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the topological structure of the closed-loop AC system. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0031] In the closed-loop operation of the AC filter field, a cross-balancing control method for the priority of switching on and off filters of the same type is adopted to achieve a balanced number of switching priorities for filters of the same type in the two filter fields. In the closed-loop operation, a control method for selecting the switching on and off of the next group of filters is adopted according to the filter's available / removable status and the switching on and off priority status to ensure that when a certain AC filter is unavailable, the other available filters can be selected as the next group of filters to be switched on or off for reactive power control. The purpose of the present invention is to avoid the phenomenon of multiple switching on and off in the filter field in a short period of time when the AC field main circuit breaker is tripped and the operation is switched from closed-loop to split-loop operation; and the problem that a certain AC filter is unavailable, resulting in the inability to switch on or off the filter in the closed-loop operation mode in reactive power control, affecting the normal operation of the DC system.

[0032] The present invention provides a topological structure of a closed-loop AC system, such as Figure 1 shown.

[0033] When bus tie breaker 1 or bus tie breaker 2 is in the closed position, the AC field and filter field are in a closed-loop operation mode, and the four filter groups (filters 1, 2, 3, and 4) collectively participate in the reactive power control function of converters 1 and 2. When bus tie breaker 1 and bus tie breaker 2 are both in the open position, filters 1 and 2 participate in the reactive power control function of converter 1, and filters 3 and 4 participate in the reactive power control function of converter 2. This invention is used for filter switching control in a closed-loop condition.

[0034] Set the four major filter groups, Filters 1, 2, 3, and 4, to each be configured with two small groups of parallel filters of the same type; the corresponding relationship between the major filter groups and the small group filters is as follows:

[0035] Filter 1: ACF11, ACF12

[0036] Filter 2: ACF22, ACF23

[0037] Filter 3: ACF31, ACF33

[0038] Filter 4: ACF42, ACF44

[0039] The present invention provides a filter priority change table for sequentially putting all filters into operation according to default priorities when all filters are available for use in closed-loop operation, as shown in Table 1.

[0040] Table 1 Default priority filter priority change table

[0041]

[0042] The present invention provides a filter priority change table for sequentially removing filters according to default priorities when all filters can be removed during closed-loop operation, as shown in Table 2.

[0043] Table 2 Default priority filter priority change table

[0044]

[0045] After power-on initialization, the filter controller assigns a default filter priority to each filter of the same type. 0 is the highest priority, and 7 is the lowest. The lowest priority level is adjustable based on the maximum number of filters of the same type in AC Field 1 and AC Field 2. The nth column in Tables 1 and 2 shows the default filter priority for each filter group in closed-loop operation. This indicates that the filters in AC Field 1 and AC Field 2 are assigned priority in descending order.

[0046] Filter default priority down / down filter priority change control principle:

[0047] When the filter ACF XY The casting / cutting priority of (1<=X<=4; 1<=Y<=4) is M / N (0<=M<=7; 0<=N<=7). After this group of filters is put into use, N is forced to switch to 7, and M remains unchanged, that is, the cutting priority is forced to switch to the lowest priority of the cutting priority, and the casting priority remains unchanged; the casting / cutting priority of other filters M1 / N1 (0<=M1<=7; 0<=N1<=7) changes according to the cutting priority N1≥N, then N1=N1-1; otherwise it remains unchanged; the casting priority remains unchanged.

[0048] When the filter ACF XYThe casting / cutting priority of (1<=X<=4; 1<=Y<=4) is M / N (0<=M<=7; 0<=N<=7). After cutting off this group of filters, M is forced to switch to 7, and N remains unchanged, that is, the casting priority is forced to switch to the lowest priority of the casting priority, and the cutting priority remains unchanged; the casting / cutting priority M1 / N1 (0<=M1<=7; 0<=N1<=7) of other filters changes in accordance with the casting priority M1≥M, then M1=M1-1; otherwise, it remains unchanged; the cutting priority remains unchanged.

[0049] Table 1 and Table 2 show that when all filters can be put into operation or cut off, all filters are put into operation or cut off in sequence according to the default priority, and eventually all the filter putting / cutting priorities will be restored to the initial default filter putting / cutting priority configuration.

[0050] The present invention proposes a control step for selecting the next group of filters of the same type to be put into operation according to the available filters and the priority of the filters to be put into operation under closed-loop operation, as follows:

[0051] 1) Determine the status of all filters, select the filter that is ready to be put into use and proceed to step 2);

[0052] The filter is in the exit state and can be set to be put into operation, which is the filter put into operation state; the filter is in the operation state or the filter is in the exit state and can not be set to be put into operation, which is the filter non-put into operation state;

[0053] 2) Collect the input priority of all filters that can be put into operation;

[0054] 3) Calculate the highest input priority P of all filters ON_TOP ;

[0055] P ON_TOP =MIN{M1(ACF 11 ),M2(ACF 12 ),…M(ACF XY )}

[0056] If ACF XY If it is a non-investable filter, then it participates in the highest investment priority P of all filters ON_TOP. Calculation input priority: M = +∞.

[0057] 4) Select the next group to be put into the filter

[0058] If P ON_TOP =M(ACF XY ), then ACF XY The filter bank is selected as the next one to be input.

[0059] The present invention proposes a control step for selecting the next group of filters of the same type to be cut out according to the filter cutout capability and filter cutout priority in closed loop operation as follows:

[0060] 1) Determine the status of all filters, select the filter that is in the removable state and proceed to step 2);

[0061] The filter is in the enabled state and the cut-off setting is allowed as the filter cut-off state; the filter is in the cut-off state or the filter is in the enabled state and the cut-off setting is not allowed as the filter non-enabled state;

[0062] 2) Collect the removal priorities of all filters in the current removable state;

[0063] 3) Calculate the highest cutoff priority P of all filters OFF_TOP ;

[0064] P OFF_TOP =MIN{N1(ACF 11 ),N2(ACF 12 ),…N(ACF XY )}

[0065] If ACF XY If it is a non-removable filter, then the highest removal priority P of all filters is involved. OFF_TOP. Calculated resection priority: N = +∞.

[0066] 4) Select the next set of filters to be removed

[0067] If P OFF_TOP =N(ACF XY ), then ACF XY The filter bank selected as the next set to be cut off.

[0068] When the filter is in a non-engageable or non-removable state, it does not affect the current activation / removal priority of the filter, but only affects whether it is selected as the control strategy for the next group of activation or removal filters.

[0069] When a filter changes from a non-engageable or non-removable state to an engageable or removable state, it participates in the control of the next group of engaged or removable filters based on its current engagement / removal priority. If a filter changes from a non-engageable state to an engageable state, the engagement priority is set to the real-time engagement priority value of the filter with the current removable priority. If a filter changes from a non-removable state to a removable state, the removal priority is set to the real-time removable priority value of the filter with the current engagement priority.

[0070] The present invention provides a switching selection control method for a filter in an open-close loop AC system, comprising the following steps:

[0071] Set the initial priority value of the activation and deactivation order for each group of filters of the same type; the order of the initial priority values ​​from high to low is: the first group of filters for bus i, the first group of filters for buses located in different AC fields from bus i and connected through bus couplers, the second group of filters for bus i, the second group of filters for buses located in different AC fields from bus i and connected through bus couplers, the first group of filters for buses located in the same AC field as bus i, the first group of filters for buses located in different AC fields from bus i and not connected through bus couplers, the second group of filters for buses located in the same AC field as bus i, and the second group of filters for buses located in different AC fields from bus i and not connected through bus couplers.

[0072] When a group of filters need to be selected for use, the filter with the highest priority among the filters that can be used is selected for use, and the removal priority of the filter to be used is set to the lowest, and the removal priority of other filters is increased by one level.

[0073] When a group of filters needs to be selected for removal, the filter with the highest removal priority among the filters in the removable state is selected and put into use, and the input priority of the filter is set to the lowest, and the input priority of other filters is increased by one level.

[0074] The present invention provides a filter switching selection control system for an open-close ring AC system, comprising four busbars and a controller;

[0075] Each busbar is equipped with two sets of parallel filters, and the four buses operate in a ring;

[0076] The controller obtains or sets the initial priority value of the order of input and removal of each group of filters of the same type; when receiving a filter input instruction, the filter with the highest input priority among the filters in the input state is selected for input, and the removal priority of the input filter is set to the lowest, and the removal priority of other filters is increased by one level; when receiving a filter removal instruction to select a group of filters, the filter with the highest removal priority among the filters in the removable state is selected for input, and the input priority of the input filter is set to the lowest, and the input priority of other filters is increased by one level.

[0077] In summary, the present invention relates to a filter switching selection control method and system for a split-loop AC system, which sets an initial priority value for the order of switching on and off for each group of filters; when a group of filters needs to be selected for switching on, the filter with the highest switching priority among the filters in the switching-on state is selected for switching on, and the switching-off priority of the switched-on filter is set to the lowest, and the switching-off priority of other filters is increased by one level; when a group of filters needs to be selected for switching off, the filter with the highest switching priority among the filters in the switching-off state is selected for switching on, and the switching-on priority of the switched-on filter is set to the lowest, and the switching-on priority of other filters is increased by one level. The present invention avoids the phenomenon of multiple switching or multiple switching on of the filter field in a short period of time when the AC field main circuit breaker trips and switches from closed-loop operation to split-loop operation, avoids the unavailability of a certain AC filter, and causes the reactive power control in the closed-loop operation mode to be unable to switch on or off the filter, thereby ensuring the normal operation of the DC system.

[0078] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A method for switching selection and control of filters in an open-close loop AC system, characterized in that: include: Each busbar is equipped with two sets of parallel filters, and the busbars operate in a closed loop; Set the initial priority value of the input and removal order for each group of filters of the same type; When a group of filters need to be selected for use, the filter with the highest priority among the available filters is selected for use, and the removal priority of the filter is set to the lowest. The removal priority of other filters is increased by one level. When a group of filters need to be selected for removal, the filter with the highest removal priority among the filters in the removable state is selected and put into use, and the input priority of the filter is set to the lowest, and the input priority of other filters is increased by one level; The order of the initial priority of setting the order of input and removal for each group of filters is from high to low: The first group of filters for busbar i, the first group of filters for busbars located in different AC fields from busbar i and connected through a bus coupler, the second group of filters for busbar i, the second group of filters for busbars located in different AC fields from busbar i and connected through a bus coupler, the first group of filters for busbars located in the same AC field as busbar i, the first group of filters for busbars located in different AC fields from busbar i and not connected through a bus coupler, the second group of filters for busbars located in the same AC field as busbar i, and the second group of filters for busbars located in different AC fields from busbar i and not connected through a bus coupler.

2. The filter switching selection control method for an open-close loop AC system according to claim 1, characterized in that: If the status of a filter is not enableable, the enable priority is set to infinitely low.

3. The filter switching selection control method for an open-close loop AC system according to claim 2, characterized in that: If the state of a filter changes from a non-engageable state to an engageable state, the engagement priority is set to the real-time value of the current switching priority filter's engagement priority.

4. The filter switching selection control method for an open-close loop AC system according to claim 1, characterized in that: If the status of a filter is non-removable, the removable priority is set to infinitely low.

5. The filter switching selection control method for an open-close loop AC system according to claim 4, characterized in that: If the state of a filter changes from a non-removable state to a removable state, the removal priority is set to the real-time value of the removal priority of the current switching priority filter.

6. A filter switching selection control system for an open-close loop AC system, characterized in that: Includes four busbars and controller; Each busbar is equipped with two sets of parallel filters, and the four buses operate in a ring; The controller obtains or sets the initial priority value of the order of activation and removal of filters of the same type in each group; upon receiving a filter activation instruction, the filter with the highest activation priority among the filters in the activation state is selected for activation, and the removal priority of the activated filter is set to the lowest, and the removal priority of other filters is increased by one level; upon receiving a filter removal instruction to select a group of filters, the filter with the highest removal priority among the filters in the removal state is selected for activation, and the activation priority of the activated filter is set to the lowest, and the activation priority of other filters is increased by one level; The priority of each group of filters in the order of input and removal is as follows from high to low: The first group of filters for busbar i, the first group of filters for busbars located in different AC fields from busbar i and connected through a bus coupler, the second group of filters for busbar i, the second group of filters for busbars located in different AC fields from busbar i and connected through a bus coupler, the first group of filters for busbars located in the same AC field as busbar i, the first group of filters for busbars located in different AC fields from busbar i and not connected through a bus coupler, the second group of filters for busbars located in the same AC field as busbar i, and the second group of filters for busbars located in different AC fields from busbar i and not connected through a bus coupler.

7. The filter switching selection control system for an open-close loop AC system according to claim 6, characterized in that: The controller reads the status of the filter. If the status of a filter is not available for input, the controller sets the input priority of the filter to infinitely low.

8. The filter switching selection control system for an open-close loop AC system according to claim 7, characterized in that: The controller reads the status of the filter. If the status of a filter changes from a non-engageable state to an engageable state, the controller sets the engagement priority of the filter to the real-time value of the current switching priority filter engagement priority.

9. The filter switching selection control system for an open-close loop AC system according to claim 6, characterized in that: The controller reads the status of the filters. If the status of a filter is a non-removable state, the controller sets the removal priority of the filter to infinitely low.

10. The filter switching selection control system for an open-close loop AC system according to claim 9, characterized in that: The controller reads the status of the filter. If the status of a filter changes from a non-removable state to a removable state, the controller sets the removal priority of the filter to the real-time value of the removal priority of the current switching priority filter.

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