Method and system for extracting interval frequency of synchronous phasor measurement device

Abstract

The invention provides a synchronous phasor measurement device interval frequency extraction method and system, and the method comprises the steps: carrying out the effectiveness discrimination of each phase voltage frequency measured by a synchronous phasor measurement device according to a phase voltage effectiveness criterion and a phase voltage frequency sudden change criterion; wherein the phase voltage validity criterion is as follows: the phase voltage amplitude is in a range formed by a voltage amplitude dead zone and a voltage amplitude threshold, and the frequency change rate is smaller than a voltage frequency change rate threshold; the phase voltage frequency abrupt change criterion is that the difference between the voltage frequency of the current time section and the voltage frequency before one cycle subtracts the difference between the voltage frequency before one cycle and the voltage frequency before two cycles, and the absolute value of the result is larger than a frequency abrupt change threshold value; and extracting the interval frequency according to the effectiveness judgment result of the phase voltage frequency of each phase. According to the method, the interval frequency of the synchronous phasor measurement device can be extracted, engineering can be implemented, and the operand is low.

Description

Technical Field

[0001] The invention belongs to the technical field of power system operation control and protection, and relates to a method and system for extracting interval frequency of a synchronous phasor measurement device. Background Art

[0002] With the continuous expansion of the scale of power grid and the access of renewable energy, the structure and operation characteristics of the power grid have become more complex, which puts forward higher requirements for the online monitoring of the real-time operation of the power grid. At present, the main stations of dispatching centers at all levels in provinces in my country have built wide-area monitoring systems for online monitoring of real-time waveform, frequency, frequency change rate, oscillation, etc. of the power grid.

[0003] The synchronous phasor measurement device collects phase voltage and current, obtains the corresponding amplitude and phase through calculation, and completes the frequency calculation of the interval through the positive sequence voltage. However, due to the advancement of high proportion of new energy and high proportion of power electronics in the power grid, single-phase line disturbance will affect the positive sequence voltage; at the same time, for single-phase faults and two-phase faults with a high ratio on site, the positive sequence voltage will be seriously deformed; in addition, for storage application scenarios, commutation will cause the positive sequence voltage at the collection end to be zero. For the above scenarios, using the positive sequence voltage to calculate the frequency will bring large errors, or the lack of positive sequence voltage will make it impossible to complete the frequency calculation. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a method and system for extracting the interval frequency of a synchronous phasor measurement device. Aiming at the requirements of the wide-area measurement system for the frequency accuracy of the phasor measurement device, combined with the computing power of the applied secondary embedded device, the interval frequency extraction of the synchronous phasor measurement device of the plant station is realized, which is feasible and has low computational complexity.

[0005] The present invention adopts the following technical solution.

[0006] A first aspect of the present invention provides a method for extracting interval frequency of a synchronized phasor measurement device, comprising:

[0007] Step 1: According to the phase voltage validity criterion and the phase voltage frequency mutation criterion, the validity of the phase voltage frequency of each phase measured by the synchronous phasor measurement device is judged;

[0008] Step 2: Extract the interval frequency based on the validity judgment results of the phase voltage frequency of each phase.

[0009] Preferably, the phase voltage validity criterion is:

[0010] The phase voltage amplitude is within the range formed by the voltage amplitude dead zone and the voltage amplitude threshold, and the phase voltage frequency change rate at the current time section is less than the voltage frequency change rate threshold, where the voltage frequency change rate threshold is determined according to the device trigger recording frequency change rate start threshold and is within the range of 1Hz / s to 10Hz / s.

[0011] Preferably, the voltage amplitude dead zone is 9% of the rated voltage;

[0012] The voltage amplitude threshold is 121% of the rated voltage.

[0013] Preferably, the voltage frequency change rate threshold is taken according to the device triggering recording frequency change rate start threshold, which is as follows:

[0014] When the start threshold is in the range of 1 Hz / s to 10 Hz / s, the voltage-frequency change rate threshold is set according to the start threshold; when the start threshold is less than 1 Hz / s, the voltage-frequency change rate threshold is 1 Hz / s; when the start threshold is greater than 10 Hz / s, the voltage-frequency change rate threshold is 10 Hz / s.

[0015] Preferably, the phase voltage frequency mutation criterion is:

[0016] |(f-fpre1)-(fpre1-fpre2)|>dFset

[0017] Among them, |·| means finding the absolute value;

[0018] F is the phase voltage frequency of the current time section;

[0019] Fpre1 is the phase voltage frequency one cycle before the current time section;

[0020] Fpre2 is the phase voltage frequency two cycles ago at the current time section;

[0021] dFset is the frequency mutation threshold.

[0022] Preferably, in step 1, if the phase voltage measured by the synchronous phasor measurement device meets the phase voltage validity criterion but does not meet the phase voltage frequency mutation criterion, the phase voltage frequency of the corresponding phase is valid, otherwise the phase voltage frequency of the corresponding phase is invalid.

[0023] Preferably, step 2 is specifically:

[0024] If the phase voltage frequencies of the three phases are all invalid, the interval frequency is invalid and is set to 0;

[0025] If the phase voltage frequency of a single phase is valid, the interval frequency is the phase voltage frequency of this phase;

[0026] If the phase voltage frequencies of two phases are valid, the interval frequency is the phase voltage frequency with the priority phase sequence first.

[0027] If the phase voltage frequencies of the three phases are all valid, the interval frequency is the phase voltage frequency of the stable phase.

[0028] Preferably, the phase voltage frequency of the stable phase is determined by:

[0029] The phase voltage frequencies of the three phases are subtracted from each other and their absolute values ​​are taken. The phase voltage frequency is extracted from the phase corresponding to the smallest absolute value, and the phase voltage frequency with the priority phase sequence in the extracted phase voltage frequencies is taken as the phase voltage frequency of the stable phase.

[0030] Preferably, the method further comprises: after selecting the interval frequency, calculating the change rate thereof to obtain the interval frequency change rate.

[0031] A second aspect of the present invention provides a synchronous phasor measurement device interval frequency extraction system, comprising:

[0032] The validity judgment module is used to judge the validity of the phase voltage frequency of each phase measured by the synchronous phasor measurement device according to the phase voltage validity judgment criterion and the phase voltage frequency mutation judgment criterion;

[0033] The interval frequency extraction module is used to extract the interval frequency according to the validity judgment result of the phase voltage frequency of each phase.

[0034] Compared with the prior art, the beneficial effects of the present invention include at least:

[0035] The present invention judges the validity of the phase voltage frequency of each phase measured by a synchronous phasor measurement device according to the phase voltage validity criterion and the phase voltage frequency mutation criterion, and extracts the interval frequency according to the validity judgment result of the phase voltage frequency of each phase. By using this method, the CPU processing time is short, the storage occupancy is small, the logic is clear, and the interval frequency measurement accuracy and reliability are greatly improved. The problem of decreased interval frequency measurement accuracy caused by non-full-phase disturbance and fault of the system when using positive sequence voltage for frequency calculation is solved, and the temporary loss of frequency in the storage switching process is avoided.

[0036] At the same time, the phase voltage validity criterion of the present invention limits the range of the voltage frequency change rate threshold, which can effectively avoid the failure of the validity criterion caused by the starting threshold being set too small in the running system, and avoid the situation where the actual system jitter is still judged as valid when the starting threshold is set too large. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flow chart of the interval frequency extraction method of the synchronized phasor measurement device;

[0038] Figure 2 It is a schematic diagram of the internal data flow of the synchronized phasor measurement device;

[0039] Figure 3 Extract coordinate plots for frequencies;

[0040] Figure 4 It is a schematic diagram for judging the validity of single-phase frequency;

[0041] Figure 5 Extract the state machine diagram for the interval frequency;

[0042] Figure 6 It is the conditions and thresholds for triggering recording of the device. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0044] Embodiment 1 of the present invention provides a method for extracting the interval frequency of a synchronous phasor measurement device, which determines the validity of the phase voltage amplitude and the phase voltage frequency mutation, identifies the effective phase frequency, and completes the interval frequency selection by referring to the interval frequency selection state machine, such as Figure 1 As shown, specifically including:

[0045] Step 1: According to the phase voltage validity criterion and the phase voltage frequency mutation criterion, the validity of the phase voltage frequency of each phase measured by the synchronous phasor measurement device is judged;

[0046] Figure 2 The figure is a schematic diagram of the internal data flow of the synchronous phasor measurement device (hereinafter referred to as the device) of the present invention. The core of the device consists of two parts: the phasor calculation processor collects phase voltage and phase current, completes phasor calculation, outputs the amplitude, phase, frequency, and frequency change rate of the corresponding phase voltage, and outputs the amplitude and phase of the corresponding phase current; the communication management processor collects the output data of each phase and outputs it in an interval mode according to national standards. The interval data includes the amplitude and phase of each phase, the frequency of the interval, and the frequency change rate.

[0047] Figure 3 The device performs phasor calculation based on the whole cycle data window, and puts the time stamp of the calculated data point in the middle of the data window, and the frequency output interval is 10ms. In this embodiment, the whole cycle position point is used to judge the frequency mutation. F is the current point frequency, Fpre1 is the frequency before the current point for one cycle, and Fpre2 is the frequency before the current point for two cycles.

[0048] Further preferably, the effective phase frequency is identified by phase voltage amplitude validity judgment and phase voltage frequency mutation judgment: if the phase voltage measured by the synchronous phasor measurement device meets the phase voltage validity judgment but does not meet the phase voltage frequency mutation judgment, the phase voltage frequency of the corresponding phase is valid, otherwise the phase voltage frequency of the corresponding phase is invalid, as follows:

[0049] (1) Determine whether the phase voltage at the current time section is valid. If so, proceed to (2). Otherwise, determine that the phase voltage frequency at the current time section is invalid.

[0050] The phase voltage validity criterion is: the phase voltage amplitude is greater than the voltage amplitude dead zone and less than the voltage amplitude threshold, and the voltage frequency change rate at this calculation point (phase voltage frequency change rate at the current time section) is less than the voltage frequency change rate threshold, where the voltage frequency change rate threshold is determined according to the device trigger recording frequency change rate start threshold, and the range is 1Hz / s to 10Hz / s.

[0051] like Figure 4 As shown, if the phase voltage validity criterion is met, the phase voltage is judged to be valid, otherwise the phase voltage is judged to be invalid.

[0052] Preferably, referring to the detection specification, the voltage amplitude dead zone of the measuring point is set to 9% of the rated voltage, the voltage amplitude threshold is set to 121% of the rated voltage, and the voltage measurement value is within the range of 9% to 121% of the rated voltage, then the measurement amplitude is within the effective voltage range.

[0053] like Figure 6 As shown, there are multiple trigger recording conditions. The present invention selects the frequency change rate start value, and the default value of the frequency change rate start threshold is 1. When the site changes, it is adjusted or set to other values ​​according to the site.

[0054] The voltage-frequency change rate threshold is taken from the device trigger recording frequency change rate start threshold, and the range is 1Hz / s to 10Hz / s. That is, if the start threshold is in the range of 1Hz / s to 10Hz / s, the voltage-frequency change rate threshold is set according to the start threshold; if the start threshold is less than 1, the voltage-frequency change rate threshold is 1Hz / s; if the start threshold is greater than 10, the voltage-frequency change rate threshold is 10Hz / s. By limiting the range of 1Hz / s to 10Hz / s, it is possible to avoid the failure of the validity criterion caused by the start threshold being set too small in the running system, and to avoid the actual system jitter being judged as valid when the start threshold is set too large.

[0055] (2) Determine whether the phase voltage frequency at the current time section changes suddenly. If so, determine that the phase voltage frequency is invalid; otherwise, determine that the phase voltage frequency is valid;

[0056] The criterion for phase voltage frequency mutation is:

[0057] |(f-fpre1)-(fpre1-fpre2)|>dFset

[0058] Where || is the absolute value, F is the frequency of the current point, Fpre1 is the wavefront frequency of one cycle in the current time section, Fpre2 is the wavefront frequency of two cycles in the time section, and dFset is the mutation threshold.

[0059] In this embodiment, dFset is set to twice the standard requirement of 0.002 Hz, that is, 0.004 Hz. This value can ensure that a 5% amplitude step frequency is not misjudged as a step.

[0060] Based on the above criteria, if the absolute value of the difference between the voltage frequency of the current time section and the voltage frequency of one wave before minus the difference between the voltage frequency of one wave before and the voltage frequency of two waves before is greater than the frequency mutation threshold, the phase voltage frequency will mutation; otherwise, there will be no mutation in the phase voltage frequency.

[0061] According to the above (1)-(2), if the phase voltage is judged to be valid and the phase voltage frequency has no sudden change, then the phase voltage frequency is valid; otherwise, the phase voltage frequency is invalid, that is, when the measured amplitude is within the valid voltage range and the measured frequency has no sudden change, the measured frequency of the phase voltage is valid.

[0062] Step 2: Extract the interval frequency based on the validity judgment results of the phase voltage frequency of each phase.

[0063] Further preferably, based on the single-phase frequency validity determination result in step 1, the interval frequency extraction state machine is used to extract the current time section frequency of the interval, that is, the interval frequency is selected after the validity determination of the three-phase voltage frequency, such as Figure 5 As shown, the details are as follows:

[0064] (1) If the three-phase voltage frequency is invalid, the interval voltage frequency is invalid. When the interval frequency is invalid, it is set to 0. That is, when the three-phase frequency is invalid, the frequency and frequency change rate calculated by the CPU are random numbers, and the default frequency is 0. This scenario is mostly the default output of the system without power supply or three-phase failure.

[0065] (2) If the single-phase voltage frequency is valid, the interval voltage frequency is selected as the voltage frequency of this phase, that is, when the single-phase frequency is valid, the selected frequency is the single-phase frequency. It is mainly used in the case where only one phase of the bus interval extracts voltage, or when two phases fail.

[0066] (3) If the two-phase voltage frequency is valid, the interval voltage frequency is selected as the voltage frequency with the first phase sequence, that is, when the two-phase frequency is valid, the selected frequency is the frequency with the first phase sequence in the two phases. It is mainly used in VV wiring mode or frequency selection when a single-phase fault occurs. In specific implementation, the phase sequence priority is: A>B>C.

[0067] (4) If the three-phase voltage frequencies are all valid, the interval voltage frequency is selected as the stable phase voltage frequency. The three-phase voltage frequencies are subtracted from each other and the absolute value is taken. The voltage frequency is extracted from the phase corresponding to the smallest absolute value, and the voltage frequency with the earliest phase sequence is prioritized as the stable phase voltage frequency. That is, when the three-phase frequencies are all valid, the one with the smallest three-phase frequency difference is selected, and the phase with the earliest phase sequence min[|fa-fb|,|fb-fc|,|fc-fa|] is prioritized. This scenario is the main scenario during on-site operation. The three-phase frequencies are all valid. The identification of min[|fa-fb|,|fb-fc|,|fc-fa|] is mainly performed when the line has a small disturbance, and the interval frequency can still be stably selected.

[0068] Further preferably, the interval frequency change rate and the frequency selection are the same phase calculation results, that is, after the interval frequency is selected, the interval frequency change rate is calculated to obtain the interval frequency change rate.

[0069] Embodiment 2 of the present invention provides a system for extracting interval frequency of a synchronized phasor measurement device, the system comprising:

[0070] The validity judgment module is used to judge the validity of the phase voltage frequency of each phase measured by the synchronous phasor measurement device according to the phase voltage validity judgment criterion and the phase voltage frequency mutation judgment criterion;

[0071] The interval frequency extraction module is used to extract the interval frequency according to the validity judgment result of the phase voltage frequency of each phase.

[0072] Embodiment 3 of the present invention provides a terminal, including a processor and a storage medium; the storage medium is used to store instructions;

[0073] The processor is configured to operate according to the instructions to execute the steps of the method.

[0074] Embodiment 4 of the present invention provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of the method when executed by a processor.

[0075] Compared with the prior art, the beneficial effects of the present invention include at least:

[0076] The present invention judges the validity of the phase voltage frequency of each phase measured by a synchronous phasor measurement device according to the phase voltage validity criterion and the phase voltage frequency mutation criterion, and extracts the interval frequency according to the validity judgment result of the phase voltage frequency of each phase. By using this method, the CPU processing time is short, the storage occupancy is small, the logic is clear, and the interval frequency measurement accuracy and reliability are greatly improved. The problem of decreased interval frequency measurement accuracy caused by non-full-phase disturbance and fault of the system when using positive sequence voltage for frequency calculation is solved, and the temporary loss of frequency in the storage switching process is avoided.

[0077] At the same time, the phase voltage validity criterion of the present invention limits the range of the voltage frequency change rate threshold, which can effectively avoid the failure of the validity criterion caused by the starting threshold being set too small in the running system, and avoid the situation where the actual system jitter is still judged as valid when the starting threshold is set too large.

[0078] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for extracting interval frequency of a synchronized phasor measurement device, characterized in that: The method comprises: Step 1: According to the phase voltage validity criterion and the phase voltage frequency mutation criterion, the validity of the phase voltage frequency of each phase measured by the synchronous phasor measurement device is judged; Step 2: Extract the interval frequency based on the validity judgment results of the phase voltage frequency of each phase.

2. A method for extracting interval frequency of a synchronized phasor measurement device according to claim 1, characterized in that: The phase voltage validity criterion is: The phase voltage amplitude is within the range formed by the voltage amplitude dead zone and the voltage amplitude threshold, and the phase voltage frequency change rate at the current time section is less than the voltage frequency change rate threshold, where the voltage frequency change rate threshold is determined according to the device trigger recording frequency change rate start threshold and is within the range of 1Hz / s to 10Hz / s.

3. A method for extracting interval frequency of a synchronized phasor measurement device according to claim 2, characterized in that: The voltage amplitude dead zone is 9% of the rated voltage; The voltage amplitude threshold is 121% of the rated voltage.

4. A method for extracting interval frequency of a synchronized phasor measurement device according to claim 2, characterized in that: The voltage-frequency change rate threshold is specifically determined as follows: When the start threshold is in the range of 1 Hz / s to 10 Hz / s, the voltage-frequency change rate threshold is set according to the start threshold; when the start threshold is less than 1 Hz / s, the voltage-frequency change rate threshold is 1 Hz / s; when the start threshold is greater than 10 Hz / s, the voltage-frequency change rate threshold is 10 Hz / s.

5. The method for extracting interval frequency of a synchronized phasor measurement device according to claim 1, characterized in that: The criterion for phase voltage frequency mutation is: |(f-fpre1)-(fpre1-fpre2)|>dFset Among them, |·| means finding the absolute value; F is the phase voltage frequency of the current time section; Fpre1 is the phase voltage frequency one cycle before the current time section; Fpre2 is the phase voltage frequency two cycles ago at the current time section; dFset is the frequency mutation threshold.

6. A method for extracting interval frequency of a synchronized phasor measurement device according to claim 1, characterized in that: In step 1, if the phase voltage measured by the synchronous phasor measurement device meets the phase voltage validity criterion but does not meet the phase voltage frequency mutation criterion, the phase voltage frequency of the corresponding phase is valid, otherwise the phase voltage frequency of the corresponding phase is invalid.

7. A method for extracting interval frequency of a synchronized phasor measurement device according to claim 1, characterized in that: Step 2 is as follows: If the phase voltage frequencies of the three phases are all invalid, the interval frequency is invalid and is set to 0; If the phase voltage frequency of a single phase is valid, the interval frequency is the phase voltage frequency of this phase; If the phase voltage frequencies of two phases are valid, the interval frequency is the phase voltage frequency with the priority phase sequence first. If the phase voltage frequencies of the three phases are all valid, the interval frequency is the phase voltage frequency of the stable phase.

8. A method for extracting interval frequency of a synchronized phasor measurement device according to claim 7, characterized in that: The phase voltage frequency of the stable phase is determined as follows: The phase voltage frequencies of the three phases are subtracted from each other and their absolute values ​​are taken. The phase voltage frequency is extracted from the phase corresponding to the smallest absolute value, and the phase voltage frequency with the priority phase sequence in the extracted phase voltage frequencies is taken as the phase voltage frequency of the stable phase.

9. A method for extracting interval frequency of a synchronized phasor measurement device according to claim 1, characterized in that: The method also includes: after selecting the interval frequency, calculating the change rate thereof to obtain the interval frequency change rate.

10. A system for extracting interval frequency of a synchronized phasor measurement device, using the method according to any one of claims 1 to 9, characterized in that: The system comprises: The validity judgment module is used to judge the validity of the phase voltage frequency of each phase measured by the synchronous phasor measurement device according to the phase voltage validity judgment criterion and the phase voltage frequency mutation judgment criterion; The interval frequency extraction module is used to extract the interval frequency according to the validity judgment result of the phase voltage frequency of each phase.

Images