Low-frequency and low-voltage load shedding control method for power distribution network

Abstract

The invention discloses a low-frequency and low-voltage load shedding control system and method for a power distribution network. The system comprises a master station system and an off-station terminal, the master station system comprises a defense line system display module, a low-frequency locking FA module, a multi-source data fusion analysis module and an automatic alternate switching strategy generation module; the off-station terminal comprises a low-voltage load shedding module, a low-frequency load shedding module, an anti-islanding remote jump module and a GOOSE multicast interface module; the low-frequency load shedding module comprises six standard wheels and two special wheels; the low-voltage load shedding module comprises two standard wheels and two special wheels; according to the invention, low-voltage and low-frequency load shedding protection is carried out on the power distribution terminal by arranging multiple continuous standard wheels and multiple independent special wheels, so that the safety of the power distribution terminal is effectively improved, and the problems that a power system is faced with safety and stability risks and even large-area power failure accidents occur when control equipment is not coordinated with each other are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of power system control, and in particular to a low-frequency and low-voltage load shedding control method for a distribution network. Background Art

[0002] The power system is a large and complex system that may be subject to disturbances such as short circuit failures, equipment component tripping, and large fluctuations in power or load at any time. In order to cope with various disturbances, the power system is equipped with a variety of automatic adjustment and automatic control devices and systems to ensure the safe and stable operation of the power system. When the disturbance exceeds the capacity of these adjustment and control devices or the response strategy is inappropriate, and the control devices are not coordinated with each other, the power system will face safety and stability risks, and even large-scale power outages may occur. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a method for controlling low-frequency and low-voltage load reduction in a distribution network, which aims to solve the problems in the background technology.

[0004] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a distribution network low-frequency and low-voltage load reduction control system, comprising: a master station system and an off-site terminal; the master station system comprises a defense line system display module, a low-frequency locking FA module, a multi-source data fusion analysis module and a wheel switching strategy automatic generation module; the off-site terminal comprises a low-voltage load reduction module, a low-frequency load reduction module, an anti-island remote jump module and a GOOSE multicast interface module; the low-frequency load reduction module comprises six standard wheels and two special wheels, and the low-voltage load reduction module comprises two standard wheels and two special wheels.

[0005] A distribution network low-frequency and low-voltage load shedding control method is applied to a distribution network low-frequency and low-voltage load shedding control system, comprising the following steps: six standard wheels in a low-frequency load shedding module perform low-frequency load shedding actions in sequence, except for the first standard wheel that performs low-frequency load shedding actions, the low-frequency load shedding actions of the remaining standard wheels must be started after the previous standard wheel performs low-frequency load shedding actions, and two special wheels perform low-frequency load shedding actions independently of each other; two standard wheels in a low-voltage load shedding module perform low-voltage load shedding actions in sequence, and the two special wheels perform low-voltage load shedding actions independently of each other; an anti-islanding remote tripping module combines electric quantity protection and non-electric quantity protection based on an input joint tripping protection logic; and the anti-islanding remote tripping module starts to operate when specified conditions are met.

[0006] Furthermore, the low-frequency load shedding action of the standard wheels and special wheels is controlled by the soft load shedding pressure plate and the hard load shedding pressure plate. When both the soft load shedding pressure plate and the hard load shedding pressure plate are put into operation, the standard wheels and special wheels are opened to perform low-frequency load shedding action.

[0007] Furthermore, the low-frequency load shedding action of the open standard wheel and the special wheel includes two situations: low-frequency load shedding enabling and low-frequency load shedding blocking; the low-frequency load shedding enabling is: putting the load shedding soft pressure plate and the load shedding hard pressure plate into operation to open the standard wheel and the special wheel for low-frequency load shedding action; the low-frequency load shedding blocking is: selecting the data where the sum of Uab<0.3*Un, Ubc<0.3*Un, and Uca<0.3*Un is greater than or equal to 1; obtaining the data of the frequency slip blocking and -df / dt>Dfzd put into operation, when Uab<0. When the sum of 3*Un, Ubc<0.3*Un, Uca<0.3*Un is greater than or equal to 1, the frequency slip interlock and -df / dt>Dfzd data are obtained, and the sum of PTDX and f<40Hz or f>55Hz is greater than or equal to 1, low-frequency load reduction interlock is performed, where PTDX represents the PT line break telesignal value; Uab, Ubc, Uca and Un are all voltages on the bus; f represents the bus frequency; df / dt represents the bus frequency change rate; Dfzd represents the frequency slip interlock value.

[0008] Furthermore, the specific process of the six standard wheels performing low-frequency load shedding actions in sequence is: f<F1, the standard wheels are opened to perform low-frequency load shedding actions, and the first round of low-frequency load shedding actions of the standard wheels is completed; f<F2, the standard wheels are opened to perform low-frequency load shedding actions, and the second round of low-frequency load shedding actions of the standard wheels is completed; f<F3, the standard wheels are opened to perform low-frequency load shedding actions, and the third round of low-frequency load shedding actions of the standard wheels is completed; f<F4, the standard wheels are opened to perform low-frequency load shedding actions, and the fourth round of low-frequency load shedding actions of the standard wheels is completed; f<F5, the standard wheels are opened to perform low-frequency load shedding actions, and the fifth round of low-frequency load shedding actions of the standard wheels are completed; f<F6, the standard wheels are opened to perform low-frequency load shedding actions, and the sixth round of low-frequency load shedding actions of the standard wheels are completed.

[0009] Furthermore, the specific process of the two special wheels performing low-frequency load shedding action independently of each other is: f<Fs1, the special wheels are opened to perform low-frequency load shedding action, and the first round of special wheel low-frequency load shedding action is completed; f<Fs1, the special wheels are opened to perform low-frequency load shedding action, and the second round of special wheel low-frequency load shedding action is completed.

[0010] Furthermore, the low-voltage load shedding of the standard wheels and special wheels is controlled by the soft pressure plate and the hard pressure plate. When both the soft pressure plate and the hard pressure plate are put into operation, the standard wheels and the special wheels are opened to perform low-voltage load shedding. When low voltage, voltage mutation and PT line break occur, the standard wheels and the special wheels are locked to perform low-voltage load shedding.

[0011] Furthermore, the specific process of opening the standard wheels and special wheels for low-pressure load reduction action is: put the soft pressure plate and the hard pressure plate into use to open the standard wheels and special wheels for low-pressure load reduction action; select the data whose sum of Uab<0.15*Un, Ubc<0.15*Un, Uca<0.15*Un is greater than or equal to 1; obtain the data of -df / dt>0.8*Un. When the data whose sum of Uab<0.15*Un, Ubc<0.15*Un, Uca<0.15*Un is greater than or equal to 1, the data of -df / dt>0.8*Un and the sum of PTDX is greater than or equal to 1, the standard wheels and special wheels are opened for low-pressure load reduction action.

[0012] Furthermore, the specific process of the two standard wheels performing low-voltage load shedding actions in sequence is: when Umax<U1, the standard wheels are opened to perform low-voltage load shedding actions, and the first round of low-voltage load shedding actions of the standard wheels are completed; when Umax<U2, the standard wheels are opened to perform low-voltage load shedding actions, and the second round of low-voltage load shedding actions of the standard wheels are completed; the specific process of the two special wheels performing low-voltage load shedding actions independently of each other is: when Umax<Us1, the special wheels are opened to perform low-voltage load shedding actions, and the first round of low-voltage load shedding actions of the special wheels are completed; when Umax<Us2, the special wheels are opened to perform low-voltage load shedding actions, and the second round of low-voltage load shedding actions of the special wheels are completed; wherein, Umax represents the maximum bus voltage.

[0013] Furthermore, the specified conditions include: the anti-islanding remote tripping module is enabled; the terminal detects that GOOSE communication is normal; the terminal at the PCC boundary automatically identifies the distribution line topology and obtains the upstream switch information based on the GOOSE network step-by-step query, and the upstream switch status meets the action conditions; the limit value of the anti-islanding remote tripping module protection is reached.

[0014] Compared with the existing technology, the present invention has the following beneficial effects: the present invention performs low-voltage and low-frequency load reduction protection on the distribution terminal by setting multiple rounds of continuous standard wheels and multiple rounds of independent special wheels, thereby effectively improving the safety of the distribution terminal and avoiding the problem that the power system faces safety and stability risks and even large-scale power outages when the control devices are not coordinated with each other; the present invention is suitable for applications such as 35kV and below switchgear, distribution stations, ring network cabinets, box transformers, pole-mounted switches, etc., and can be installed near the controlled primary equipment to realize various functions such as protection, information collection, fault detection, and execution of remote control commands on site. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the system structure of the present invention.

[0016] Figure 2 The present invention provides a flow chart of the low-frequency load reduction action of the open standard wheel and the special wheel.

[0017] Figure 3 The present invention is a flow chart of the six standard wheels and the two standard wheels sequentially performing low-pressure load reduction actions.

[0018] Figure 4 The present invention provides a flow chart of the low-pressure load reduction action for the open standard wheel and the special wheel.

[0019] Figure 5 The present invention is a flow chart of two standard wheels and two special wheels performing low-voltage load reduction actions in sequence. DETAILED DESCRIPTION

[0020] like Figure 1 As shown, the present invention provides a technical solution: a distribution network low-frequency and low-voltage load reduction control system, comprising: a master station system and an off-site terminal; the master station system comprises a defense line system display module, a low-frequency locking FA module, a multi-source data fusion analysis module and a wheel switching strategy automatic generation module; the off-site terminal comprises a low-voltage load reduction module, a low-frequency load reduction module, an anti-island remote jump module and a GOOSE multicast interface module; the low-frequency load reduction module comprises six standard wheels and two special wheels, and the low-voltage load reduction module comprises two standard wheels and two special wheels.

[0021] A method for controlling low-frequency and low-voltage load shedding in a distribution network is applied to a low-frequency and low-voltage load shedding control system of a distribution network, comprising the following steps: six standard wheels in a low-frequency load shedding module perform low-frequency load shedding actions in sequence, except for the first standard wheel that performs low-frequency load shedding actions, the remaining standard wheels must start performing low-frequency load shedding actions after the previous standard wheel performs low-frequency load shedding actions, and two special wheels perform low-frequency load shedding actions independently of each other; two standard wheels in a low-voltage load shedding module perform low-voltage load shedding actions in sequence, and the two special wheels perform low-voltage load shedding actions independently of each other; an anti-islanding remote tripping module combines electric quantity protection and non-electric quantity protection based on an input joint tripping protection logic; when specified conditions are met, the anti-islanding remote tripping module starts to operate

[0022] like Figure 2As shown, the open standard wheel and special wheel perform low-frequency load shedding action, including low-frequency load shedding enabling and low-frequency load shedding blocking. The low-frequency load shedding enabling is: putting the load shedding soft pressure plate and the load shedding hard pressure plate into the open standard wheel and special wheel to perform low-frequency load shedding action; the low-frequency load shedding blocking is: selecting the data where the sum of Uab<0.3*Un, Ubc<0.3*Un, and Uca<0.3*Un is greater than or equal to 1; obtaining the data of the frequency slip blocking and -df / dt>Dfzd put in, when Uab<0.3 is selected *Un, Ubc<0.3*Un, Uca<0.3*Un data greater than or equal to 1, obtain the frequency slip lock and -df / dt>Dfzd data, PTDX and f<40Hz or f>55Hz sum is greater than or equal to 1, low-frequency load reduction lock, where PTDX represents the PT line break telesignal value; Uab, Ubc, Uca and Un are all bus voltages; f represents bus frequency; df / dt represents bus frequency change rate; Dfzd represents frequency slip lock value.

[0023] like Figure 3 As shown, the specific process of the six standard wheels performing low-frequency load shedding actions in sequence is: f<F1, the open standard wheels perform low-frequency load shedding actions to complete the first round of low-frequency load shedding actions of the standard wheels, f<F2, the open standard wheels perform low-frequency load shedding actions to complete the second round of low-frequency load shedding actions of the standard wheels, f<F3, the open standard wheels perform low-frequency load shedding actions to complete the third round of low-frequency load shedding actions of the standard wheels, f<F4, the open standard wheels perform low-frequency load shedding actions to complete the fourth round of low-frequency load shedding actions of the standard wheels, f<F5, the open standard wheels perform low-frequency load shedding actions to complete the fifth round of low-frequency load shedding actions of the standard wheels, and f<F6, the open standard wheels perform low-frequency load shedding actions to complete the sixth round of low-frequency load shedding actions of the standard wheels.

[0024] Among them, the specific process of the two special wheels performing low-frequency load shedding action independently of each other is: f<Fs1, the special wheels are opened to perform low-frequency load shedding action, and the first round of special wheel low-frequency load shedding action is completed; f<Fs1, the special wheels are opened to perform low-frequency load shedding action, and the second round of special wheel low-frequency load shedding action is completed.

[0025] Among them, the low-voltage load shedding module includes two standard wheels and two special wheels. The two standard wheels perform low-voltage load shedding actions in sequence, and the two special wheels perform low-voltage load shedding actions independently of each other; the low-voltage load shedding of the standard wheels and the special wheels is controlled by the load shedding soft pressure plate and the load shedding hard pressure plate. When the load shedding soft pressure plate and the load shedding hard pressure plate are both put into operation, the standard wheels and the special wheels are opened to perform low-voltage load shedding actions; when low voltage, voltage mutation and PT disconnection occur, the standard wheels and the special wheels are locked to perform low-voltage load shedding actions;

[0026] Low voltage lockout: The bus line voltage is used as the judgment basis. When the minimum line voltage is lower than 15% of the rated bus line voltage, the low voltage load reduction protection is locked.

[0027] Voltage mutation blocking: The voltage mutation blocking function is fixedly put into operation. When -dv / dt>0.8*Un, the low-voltage load reduction function is blocked; when the minimum effective value of the line voltage recovers to more than 70% of the rated value and after 6S, the blocking is released;

[0028] PT line break lockout: When the busbar PT line break is detected, the low-voltage load reduction protection is instantly locked out; until the PT line break is restored, the low-voltage load reduction protection lockout is released.

[0029] like Figure 4 As shown, the specific process of opening the standard wheel and the special wheel for low-pressure load reduction action is: put the soft pressure plate and the hard pressure plate into use to open the standard wheel and the special wheel for low-pressure load reduction action; select the data whose sum of Uab<0.15*Un, Ubc<0.15*Un, Uca<0.15*Un is greater than or equal to 1; obtain the data of -df / dt>0.8*Un, when the data whose sum of Uab<0.15*Un, Ubc<0.15*Un, Uca<0.15*Un is greater than or equal to 1, the data of -df / dt>0.8*Un is obtained and the sum of PTDX is greater than or equal to 1, the standard wheel and the special wheel are opened for low-pressure load reduction action.

[0030] like Figure 5 As shown, the specific process of the two standard wheels performing low-voltage load shedding actions in sequence is: when Umax<U1, the standard wheels are opened to perform low-voltage load shedding actions, and the first round of low-voltage load shedding actions of the standard wheels are completed; when Umax<U2, the standard wheels are opened to perform low-voltage load shedding actions, and the second round of low-voltage load shedding actions of the standard wheels are completed; the specific process of the two special wheels performing low-voltage load shedding actions independently of each other is: when Umax<Us1, the special wheels are opened to perform low-voltage load shedding actions, and the first round of low-voltage load shedding actions of the special wheels are completed; when Umax<Us2, the special wheels are opened to perform low-voltage load shedding actions, and the second round of low-voltage load shedding actions of the special wheels are completed; wherein, Umax represents the maximum bus voltage.

[0031] Among them, the specified conditions include: the anti-islanding remote tripping module is enabled; the terminal detects that the GOOSE communication is normal; the terminal at the PCC boundary automatically identifies the distribution line topology and obtains the upstream switch information based on the GOOSE network step-by-step query, and the upstream switch status meets the action conditions; the limit value of the anti-islanding remote tripping module protection is reached.

[0032] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-frequency and low-voltage load reduction control system for a distribution network, characterized in that: include: The master station system and the off-site terminal; the master station system includes a defense line system display module, a low-frequency locking FA module, a multi-source data fusion analysis module and a wheel switching strategy automatic generation module; the off-site terminal includes a low-voltage load reduction module, a low-frequency load reduction module, an anti-island remote jump module and a GOOSE multicast interface module; the low-frequency load reduction module includes six standard wheels and two special wheels, and the low-voltage load reduction module includes two standard wheels and two special wheels.

2. A method for controlling low-frequency and low-voltage load shedding in a distribution network, applied to the low-frequency and low-voltage load shedding control system of the distribution network according to claim 1, characterized in that: The method comprises the following steps: six standard wheels in a low-frequency load shedding module perform low-frequency load shedding action in sequence, and except for the first standard wheel, the low-frequency load shedding action of the remaining standard wheels shall be started after the previous standard wheel performs low-frequency load shedding action, and two special wheels perform low-frequency load shedding action independently of each other; two standard wheels in a low-voltage load shedding module perform low-voltage load shedding action in sequence, and the two special wheels perform low-voltage load shedding action independently of each other; the anti-islanding remote tripping module combines the electric quantity protection and the non-electric quantity protection based on the open-in joint tripping protection logic; when the specified conditions are met, the anti-islanding remote tripping module starts to operate.

3. A method for controlling low-frequency and low-voltage load shedding in a distribution network according to claim 2, characterized in that: The low-frequency load reduction action of the standard wheels and special wheels is controlled by the soft load reduction pressure plate and the hard load reduction pressure plate. When both the soft load reduction pressure plate and the hard load reduction pressure plate are put into operation, the standard wheels and special wheels are opened to perform low-frequency load reduction action.

4. A method for controlling low-frequency and low-voltage load shedding in a distribution network according to claim 3, characterized in that: The low-frequency load shedding action of the open standard wheel and the special wheel includes two situations: low-frequency load shedding enabling and low-frequency load shedding blocking. The low-frequency load shedding enabling is: putting the load shedding soft pressure plate and the load shedding hard pressure plate into the open standard wheel and the special wheel to perform the low-frequency load shedding action; the low-frequency load shedding blocking is: selecting the data where the sum of Uab<0.3*Un, Ubc<0.3*Un, and Uca<0.3*Un is greater than or equal to 1; obtaining the data of the frequency slip blocking and -df / dt>Dfzd put into operation, when Uab<0.3*U n. When the sum of Ubc<0.3*Un, Uca<0.3*Un is greater than or equal to 1, the data of frequency slip lockout and -df / dt>Dfzd are obtained, and the sum of PTDX and f<40Hz or f>55Hz is greater than or equal to 1, low-frequency load reduction lockout is performed, where PTDX represents the PT line break telesignal value; Uab, Ubc, Uca and Un are all voltages on the bus; f represents the bus frequency; df / dt represents the bus frequency change rate; Dfzd represents the frequency slip lockout value.

5. A method for controlling low-frequency and low-voltage load shedding in a distribution network according to claim 4, characterized in that: The specific process of the six standard wheels performing low-frequency load shedding actions in sequence is: f<F1, the standard wheels are opened for low-frequency load shedding actions to complete the first round of low-frequency load shedding actions of the standard wheels, f<F2, the standard wheels are opened for low-frequency load shedding actions to complete the second round of low-frequency load shedding actions of the standard wheels, f<F3, the standard wheels are opened for low-frequency load shedding actions to complete the third round of low-frequency load shedding actions of the standard wheels, f<F4, the standard wheels are opened for low-frequency load shedding actions to complete the fourth round of low-frequency load shedding actions of the standard wheels, f<F5, the standard wheels are opened for low-frequency load shedding actions to complete the fifth round of low-frequency load shedding actions of the standard wheels, f<F6, the standard wheels are opened for low-frequency load shedding actions to complete the sixth round of low-frequency load shedding actions of the standard wheels.

6. A method for controlling low-frequency and low-voltage load shedding in a distribution network according to claim 5, characterized in that: The specific process of the two special wheels performing low-frequency load shedding action independently of each other is: f<Fs1, the special wheels are opened to perform low-frequency load shedding action, and the first round of special wheel low-frequency load shedding action is completed; f<Fs1, the special wheels are opened to perform low-frequency load shedding action, and the second round of special wheel low-frequency load shedding action is completed.

7. A method for controlling low-frequency and low-voltage load shedding in a distribution network according to claim 6, characterized in that: The low-voltage load shedding of the standard wheel and the special wheel is controlled by the soft pressure plate and the hard pressure plate. When both the soft pressure plate and the hard pressure plate are put into operation, the standard wheel and the special wheel are opened to perform low-voltage load shedding. When low voltage, voltage mutation and PT line break occur, the standard wheel and the special wheel are locked to perform low-voltage load shedding.

8. A method for controlling low-frequency and low-voltage load shedding in a distribution network according to claim 7, characterized in that: The specific process of opening the standard wheel and the special wheel for low-voltage load shedding is as follows: put the soft pressure plate and the hard pressure plate into use to open the standard wheel and the special wheel for low-voltage load shedding; select the data whose sum of Uab<0.15*Un, Ubc<0.15*Un, Uca<0.15*Un is greater than or equal to 1; obtain the data of -df / dt>0.8*Un. When the data whose sum of Uab<0.15*Un, Ubc<0.15*Un, Uca<0.15*Un is greater than or equal to 1, the data of -df / dt>0.8*Un and the sum of PTDX is greater than or equal to 1, the standard wheel and the special wheel are opened for low-voltage load shedding.

9. A method for controlling low-frequency and low-voltage load shedding in a distribution network according to claim 8, characterized in that: The specific process of the two standard wheels performing low-voltage load shedding actions in sequence is: when Umax<U1, the standard wheels are opened to perform low-voltage load shedding actions, and the first round of low-voltage load shedding actions of the standard wheels are completed; when Umax<U2, the standard wheels are opened to perform low-voltage load shedding actions, and the second round of low-voltage load shedding actions of the standard wheels are completed; the specific process of the two special wheels performing low-voltage load shedding actions independently of each other is: when Umax<Us1, the special wheels are opened to perform low-voltage load shedding actions, and the first round of low-voltage load shedding actions of the special wheels are completed; when Umax<Us2, the special wheels are opened to perform low-voltage load shedding actions, and the second round of low-voltage load shedding actions of the special wheels are completed; wherein, Umax represents the maximum bus voltage.

10. A method for controlling low-frequency and low-voltage load shedding in a distribution network according to claim 2, characterized in that: The specified conditions include: the anti-islanding remote tripping module is enabled; the terminal detects that GOOSE communication is normal; the terminal at the PCC boundary automatically identifies the distribution line topology and obtains the upstream switch information based on the GOOSE network step-by-step query, and the upstream switch status meets the action conditions; the limit value of the anti-islanding remote tripping module protection is reached.

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