JP2019221121A - Calculation program, calculation method, and calculation device, for withstanding frequency change rate - Google Patents

Abstract

To simply estimate whether a PCS will drop out.SOLUTION: The calculation program of a withstanding frequency change rate causes a computer to calculate a limit value of a frequency change rate in which a difference between a moving average of a power frequency in the latest first period and a moving average of a power frequency in a past second period before a predetermined elapsed period becomes a threshold value and output information on the basis of the calculated limit value assuming that a frequency of power changes at a constant frequency change rate from a predetermined initial value.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a calculation program, a calculation method, and a calculation device of a frequency change rate tolerance.

  The introduction of renewable energy power sources, particularly photovoltaic power generation (hereinafter, also referred to as “PV”), has been progressing toward realizing a low-carbon society. In the power system that supplies power to the customer's power receiving equipment (hereinafter also referred to as the “system”), the expansion of the introduction of PV has an obvious impact on not only supply and demand operation in normal times but also emergency stability. It is becoming.

  Electric power companies need to reduce the output of existing synchronous generators (generators) when PV output increases for a certain demand. It may be stopped. At this time, a decrease in the capacity of the generators connected in parallel to the system means a decrease in the inertia and voltage maintenance capacity of the entire system, and the frequency stability and transient stability at the time of a system failure may decrease. There is. For example, when a large power loss or system separation occurs, the rotational speed of the generator left in the system is likely to change due to a decrease in inertia. For this reason, the rate of change of the frequency of the power flowing through the system (RoCoF: Rate of Change of Frequency) tends to increase. Note that the frequency change rate can be expressed as | df / dt | as a change per unit time of the frequency f of the power supplied to the system.

  The PV is connected to the system via a power conditioner (PCS: Power Conditioning Subsystem). The PCS basically has an islanding detection function, and determines the islanding based on the cycle deviation or the frequency deviation of the interconnection point voltage. In a system in which a large number of PVs are interconnected, if the PVs drop out at once, disturbances such as voltage fluctuations and frequency fluctuations occur in the power of the system, causing a great decrease in power quality. Here, “dropout” refers to a state in which the system conditions are abnormal and the system cannot be restored after the gate block of the PCS.

  Therefore, in Japan, a requirement for fault continuation driving (Fault Ride Through) (hereinafter, also referred to as “FRT requirement”) is currently specified. The FRT requirement requires that the PCS continue operation in cooperation with the grid for frequency fluctuations of ± 2 [Hz / sec]. The PCS islanding detection function must be designed to meet FRT requirements. On the other hand, some PCSs do not support FRT before FRT requirements are defined. PCS models that do not support FRT may fall off even if the RoCoF does not reach ± 2 [Hz / sec].

  For this reason, in the event of a large power loss accident, a voltage phase jump and a frequency drop occur. Therefore, a PCS model that does not support the FRT may fall out over a wide range due to unnecessary operation of the detection method of the islanding operation detection function, which may promote the frequency drop. is there.

  The set value of the islanding detection function differs for each PCS model, and there is a difference in RoCoF where dropout occurs. For this reason, at present, various types of islanding detection functions are individually modeled, and dropouts of PCS models are estimated by simulation analysis or the like that gives desired frequency fluctuations.

  Non-Patent Document 1 proposes a technique for evaluating system stability by simulation analysis. In the technique of Non-Patent Document 1, a model of a lower system to which a PV cooperates is constructed using a PV method for a Y method that simulates the characteristics of a single PV, and a simulation analysis is performed.

Keisuke Shirasaki and Yoshihiro Kitauchi, "Basic Effects of Various System Conditions upon Large-Scale Introduction of Renewable Energy on System Stability of Backbone System", Central Research Institute of Electric Power Industry Report R14013, August 2015

  However, in the related art, it is necessary to construct a model for each PCS model and perform a simulation analysis, and it is not possible to easily estimate whether or not the PCS will be dropped.

  The present invention has been made in view of the above, and an object of the present invention is to provide a calculation program, a calculation method, and a calculation apparatus of a frequency change rate tolerance capable of easily estimating whether or not a PCS is dropped.

  In order to solve the above-described problems and achieve the object, a frequency change rate tolerance calculation program according to the present invention provides a computer with the latest power supply frequency assuming that the power frequency changes at a constant frequency change rate from a predetermined initial value. And a limit value of a frequency change rate at which a difference between the moving average of the power frequency in the first period and the moving average of the power frequency in the past second period before the predetermined elapsed period becomes a threshold value is calculated. And a process of outputting information based on the calculated limit value.

  The present invention has an effect that it can be easily estimated whether or not the PCS will be dropped.

FIG. 1 is a diagram schematically showing the determination logic. FIG. 2 is a diagram illustrating an example of a change in the period deviation with respect to a change in the frequency of the power. FIG. 3 is a diagram schematically showing a determination logic when the frequency fluctuates like a ramp. Figure 4 is a diagram showing an example of a change in cycle deviation ΔT duration t _{p +} t _r. FIG. 5 is a diagram illustrating an example of a functional configuration of the calculation device. FIG. 6 is a diagram illustrating an example of the displayed graph. FIG. 7 is a flowchart illustrating an example of the procedure of the calculation process. FIG. 8A is a diagram illustrating a detection method, a determination logic, and a set value of the islanding operation detection function. FIG. 8B is a diagram illustrating a detection method, a determination logic, and a set value of the islanding operation detection function. FIG. 9A is a diagram showing the RoCoF resistance at a reference frequency of 50 Hz. FIG. 9B is a diagram showing the RoCoF resistance at a reference frequency of 60 Hz. FIG. 10A is a diagram illustrating a frequency change rate obtained by performing a simulation analysis on the reference frequency of 50 Hz. FIG. 10B is a diagram illustrating a frequency change rate obtained by performing a simulation analysis on the reference frequency of 60 Hz. FIG. 11A is a diagram showing the result of the presence or absence of dropout by simulation analysis at a reference frequency of 50 Hz. FIG. 11B is a diagram showing the result of the presence or absence of dropout by simulation analysis at a reference frequency of 60 Hz. FIG. 12A is a diagram illustrating a result of the simulation analysis of the group B. FIG. 12B is a diagram illustrating a result of a simulation analysis of N groups. FIG. 12C is a diagram illustrating a result of the simulation analysis of the group H. FIG. 12D is a diagram illustrating a result of the simulation analysis of the group S. FIG. 13A is a graph showing the relationship between the frequency change rate RoCoF of the group of N, H, and S and the RoCoF detection time corresponding to the frequency change rate RoCoF for the reference frequency of 50 Hz. FIG. 13B is a graph showing the relationship between the frequency change rate RoCoF of the group of N, H, and S and the RoCoF detection time corresponding to the frequency change rate RoCoF for the reference frequency of 60 Hz. FIG. 14 is a diagram illustrating a computer that executes a calculation program.

  Hereinafter, embodiments of a calculation program, a calculation method, and a calculation device of a frequency change rate tolerance according to the present invention will be described in detail with reference to the drawings. The present invention is not limited by the embodiment. The embodiments can be appropriately combined within a range that does not contradict processing contents.

[Method of calculating frequency change rate tolerance (RoCoF tolerance)]
First, a method of calculating the limit value of the frequency change rate (RoCoF) at which the PCS does not drop out (the frequency change rate tolerance, hereinafter also referred to as “RoCoF tolerance”) will be described. As described above, the PCS is required to continue the operation in cooperation with the system with respect to the frequency fluctuation of ± 2 [Hz / sec] according to the FRT requirement. The PCS islanding detection function must be designed to meet FRT requirements. On the other hand, some PCSs do not support FRT before FRT requirements are defined. PCS models that do not support FRT may fall off even if the RoCoF does not reach ± 2 [Hz / sec].

  The islanding detection function of the FRT non-compliant model has a high detection sensitivity of the passive method, and typical detection methods of the passive method include a frequency change rate detection method and a voltage phase jump detection method.

FIG. 1 is a diagram schematically showing the determination logic. The frequency change rate detection method and the voltage phase jump detection method basically determine the islanding operation based on whether or not a cycle deviation between the latest cycle and the past cycle calculated by the moving average exceeds a threshold value. For example, the frequency change rate detection method and the voltage phase jump detection method, based on the time t ₁ to a determination target, a moving average of the period of the power of time t ₁ from the most recent first period t _n, the time t ₁ moves from the moving average of the period of the power of a given age t _r past the second time period t _p before is calculated, the period of the moving average of the period of the first period t _n and the second time period t _p The determination of the islanding operation is made based on whether the difference from the average exceeds the threshold value. For this reason, it is considered that the frequency change rate detection method and the voltage phase jump detection method can be regarded as having the same basic determination logic. The cycle of the AC power is the reciprocal of the frequency of the AC power. Therefore, the moving average of the period of the first period t _n is the reciprocal of the moving average f _n of the frequency of the first period t _n. Further, the moving average of the period of the second period t _p is the reciprocal of the moving average f _p of the frequency of the second period t _p.

FIG. 2 is a diagram illustrating an example of a change in the period deviation with respect to a change in the frequency of the power. FIG. 2A shows a change in the frequency when the power frequency fluctuates in a ramp shape. The ramp-like fluctuation of the power frequency is a state in which the frequency increases or decreases at a constant frequency change rate. The FIG. 2 (A), the frequency of the power, from the initial value f ₀ to the time _{t s 0.5 [Hz / sec]} , 1.0 [Hz / sec], the frequency of 2.0 [Hz / sec] This shows a state in which the rate of change is decreasing. The initial value f ₀ is, for example, a power reference frequency (50 Hz or 60 Hz).

FIG. 2B shows an example of a change in the period deviation when the power frequency fluctuates in a ramp shape. FIG. 2B shows the change in the period deviation ΔT when the frequency of the power decreases at the frequency change rates of 0.5 [Hz / sec], 1.0 [Hz / sec], and 2.0 [Hz / sec]. It is shown. As shown in FIG. 2B, cycle deviation ΔT, regardless of the magnitude of the frequency change rate, ramp-like frequency variation obtained by adding the elapsed time t _r and the second time period t _p from the start to the time t _s increases rapidly until the expiration of the period _t p + _{t r.} The cycle deviation ΔT after expiration of the time _t p + t _r, increases slowly.

  Here, in the case where the frequency of the power fluctuates in a ramp shape, the present inventor can simply determine the RoCoF resistance that the PCS does not drop off from the setting value of the determination logic regarding the frequency change rate detection method and the voltage phase jump detection method. We have devised a method that we want. In the present embodiment, the influence of the on-delay timer for preventing unnecessary operation due to the voltage phase jump has an influence on the detection time, but does not affect the RoCoF resistance, and is not considered.

FIG. 3 is a diagram schematically showing a determination logic when the frequency fluctuates like a ramp. Note that the example of FIG. 3 shows a state in which the frequency of the power is decreasing at a constant frequency change rate from the initial value f ₀ of the frequency.

In the determination logic of the frequency change rate detection method and the voltage phase jump detection method, based on the time t ₁ to a determination target, a moving average f _n of the frequency of the power at time t ₁ from the most recent first period t _n, elapsed from the time period t ₁ t _r before the previous second time period t _p power of the moving average f _p of the frequency is calculated, respectively.

When the frequency of the power changes in a ramp shape, the greater the rate of change in the frequency of the power, the greater the period deviation ΔT calculated in the determination logic. Frequency change rate detection method and the voltage phase jump detection method, cycle deviation [Delta] T is determined islanding state when a threshold is exceeded [Delta] T _t of period conversion. This determination condition can be expressed by the following equation (1).

In the case of the voltage phase jump detection method, the threshold used for determination is given as a threshold Δθ _t [deg]. In the case of the frequency change rate detection method, the threshold value used for the determination is given as a threshold value Δf _t [%]. The threshold value Δθ _t [deg] can be converted to a threshold value ΔT _t [sec] by the following equation (2-1). Also, the threshold value Δf [%] can be converted into a threshold value ΔT _t [sec] by the following equation (2-2).

As shown in FIG. 2 (B), period deviation ΔT is rapidly irrespective of the magnitude of the frequency change rate, the ramp-like frequency variation starts until after the period t _{p +} t _r. Therefore, considered that the period t _{p +} t _r cycle deviation [Delta] T by the elapsed time to the level of the ramp-shaped frequency variation reaches the threshold [Delta] T _t generally corresponding to RoCoF capability, moving average of time has elapsed period t _{p +} t _r f _n, consider that formulating a moving average f _p and cycle deviation [Delta] T.

Frequency power is, to change in a ramp shape at the frequency change ratio df / dt <0, as shown in FIG. 3, the moving average f _n of the frequency of the first period t _n is the first time period t _n It can be thought of as the midpoint frequency. Further, the moving average of the period of the second period t _p may be thought of as a frequency of the intermediate point of the second period t _p. Therefore, the moving average f _n, the moving average _{f p,} using the first time period t _n, a second time period _{t p,} age t _r, the frequency change rate df / dt, the initial value f ₀ frequency, It is represented by the following equations (3-1) and (3-2).

  The following equation (4) is obtained by simultaneously combining the above equation (1), which is the islanding detection condition, and the above equation (3). That is, it means that islanding is detected when the inequality expression (4) is satisfied, and the frequency change rate df / dt when the equality is satisfied corresponds to the RoCoF resistance.

Here, when typical setting values of the PCS shown in FIGS. 8A and 8B described later are given, in each case, the absolute value of the (df / dt) ² term on the right side is sufficiently smaller than the other terms. Become. Therefore, if the term of (df / dt) ² is removed from the equation (4), an approximate equation of RoCoF is obtained as in the following equation (5-1). The expression (5-2) when the inequality expression (5-1) is satisfied corresponds to the RoCoF tolerance.

  As a detection method of the islanding operation detection function, there is a model that uses a total value instead of a moving average value to calculate the past cycle and the latest cycle. However, the total value of n cycles is n times the moving average value of n cycles. Therefore, if the detection threshold value is set to 1 / n times, the total value can be regarded as a moving average value, so that the expression (5-2) can be applied. This corresponds to, for example, the group N in FIG. 8A described later. However, since the detection threshold is set to the same level as the others, the RoCoF resistance is reduced.

Figure 4 is a diagram showing an example of a change in cycle deviation ΔT duration t _{p +} t _r. As shown in FIG. 4, the fluctuation start frequency until the elapse of time t _{p +} t _r, increased cycle deviation ΔT draws a S-shaped curve. In the period t _{p +} t _r, paying attention to that deviation of the moving average f _p of the frequency of the power with respect to the initial value f ₀ frequency is relatively small, is regarded as the simple linear a degree of increase in cycle deviation [Delta] T, cycle deviation The slope of the increase in ΔT and the RoCoF detection time are almost inversely proportional. That is, it can be considered that the RoCoF detection time when the frequency change rate is n (> 1) times the RoCoF tolerance is 1 / n times. This relationship can be expressed by the following equation (6). In the present embodiment, the influence of the on-delay timer is not taken into consideration, but if it is taken into account, the timer time may be added to the RoCoF detection time shown in the following equation (6).

By using the equation (6), it is possible to calculate a detection period (RoCoF detection period) in which dropout is detected at the frequency change rate RoCoF for each frequency change rate RoCoF.

[Configuration of calculation device]
Next, a configuration of the calculation device 10 to which the above-described RoCoF tolerance calculation method is applied will be described. FIG. 5 is a diagram illustrating an example of a functional configuration of the calculation device. The calculation device 10 is an information processing device that calculates the RoCoF tolerance using the method according to the present embodiment. The calculation device 10 may be a computer such as a notebook computer or a personal computer, or may be a mobile terminal device such as a tablet terminal.

  The calculation device 10 includes a display unit 20, an input unit 21, a storage unit 22, and a control unit 23. The calculating device 10 may include various known functional units in addition to the functional units illustrated in FIG. For example, the calculation device 10 may include a communication interface unit that communicates with another terminal.

  The display unit 20 is a display device that displays various information. The display unit 20 includes a display device such as an LCD (Liquid Crystal Display). The display unit 20 displays various information. For example, the display unit 20 displays various operation screens and calculation results.

  The input unit 21 is an input device for inputting various information. For example, examples of the input unit 21 include input devices such as a keyboard and a mouse connected to the calculation device 10, various buttons provided on the calculation device 10, and a transmissive touch sensor provided on the display unit 20. . In the example of FIG. 5, the display unit 20 and the input unit 21 are separately provided to show a functional configuration. For example, the display unit 20 and the input unit 21 are configured by a device integrally provided with the display unit 20 and the input unit 21 such as a touch panel. May be.

  The storage unit 22 is a storage device that stores various data. For example, the storage unit 22 is a storage device such as a hard disk, a solid state drive (SSD), and an optical disk. The storage unit 22 may be a rewritable semiconductor memory such as a random access memory (RAM), a flash memory, or a non-volatile random access memory (NVSRAM).

  The storage unit 22 stores an OS (Operating System) executed by the control unit 23 and various programs. For example, the storage unit 22 stores various programs including a calculation program for executing a calculation process described later. Further, the storage unit 22 stores various data used in a program executed by the control unit 23.

  The control unit 23 is a device that controls the calculation device 10. As the control unit 23, an electronic circuit such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit), and an integrated circuit such as an ASIC (Application Specific Integrated Circuit) and an FPGA (Field Programmable Gate Array) can be adopted. The control unit 23 has an internal memory for storing programs and control data defining various processing procedures, and executes various processing by using these. The control unit 23 functions as various processing units by executing various programs. For example, the control unit 23 includes a reception unit 40, a first calculation unit 41, a second calculation unit 42, and an output unit 43.

The reception unit 40 performs various receptions. For example, the receiving unit 40 receives input of various information used for calculating the RoCoF tolerance and various operation instructions. For example, the reception unit 40 causes the display unit 20 to display an operation screen (not shown), and from the operation screen, the initial value f ₀ of the power frequency, the first period t _n for obtaining the latest moving average, and the past moving average. second time period t _p to obtain the _elapsed time t _r to the second time period t _p, and accepts the input of the threshold [Delta] t _t used for the determination. The receiving unit 40 inputs, from the operation screen, a threshold value Δθ _t [deg] of the voltage phase jump detection method and a threshold value Δf _t [%] of the frequency change rate detection method as threshold values used for the determination. May be accepted. In addition, the receiving unit 40 receives an instruction to start calculation of RoCoF resistance from an operation screen (not shown).

The first calculation unit 41, based on the various information received in the reception section 40, as the frequency of power changes from an initial value f ₀ at a fixed frequency variation rate, the most recent first period t _n power the difference between the moving average of the frequency of past second period t _p of age t _r before and the moving average of the frequency is calculated RoCoF tolerance as the threshold value [Delta] t _t. For example, the first calculation unit 41, receiving unit the initial value f ₀ accepted 40, the first period t _n, a second time period _{t p,} age t _r, and, from the threshold [Delta] T _t, the above-mentioned The RoCoF tolerance is calculated using the equation (5-2).

Incidentally, the operation screen, as a threshold used for the determination, if accepted threshold [Delta] [theta] _t, the input threshold Delta] f _t, the first calculation unit 41, the above-mentioned equation (2-1), (2 After conversion into the threshold value ΔT _t [sec], the RoCoF resistance is calculated by the equation -2).

Second calculating section 42, calculated RoCoF capability, based on the second time period _{t p} and age t _r, with respect to a multiple of the frequency change ratio relative to RoCoF capability, the detection period required for the detection of the falling, the second period t _{p +} t _r where the sum of the duration t _p and the elapsed time t _r of as being inversely proportional to calculate the condition of the detection period and the frequency change rate at the boundary dropouts occurs. For example, the second calculating unit 42, the above-mentioned (6), by substituting RoCoF tolerance and duration _t p + t _r, variously changing the frequency change rate RoCoF, RoCoF detection time corresponding to the frequency change rate RoCoF I do.

  The output unit 43 performs various outputs. For example, the output unit 43 outputs information based on the RoCoF tolerance calculated by the first calculation unit 41. As an example, the output unit 43 outputs the calculated RoCoF tolerance to the operation image. Thereby, the user can grasp the RoCoF tolerance.

  The output unit 43 outputs information based on the condition calculated by the second calculation unit 42. As an example, the output unit 43 displays the relationship between the frequency change rate RoCoF and the RoCoF detection time corresponding to the frequency change rate RoCoF in a graph on the operation screen.

  FIG. 6 is a diagram illustrating an example of the displayed graph. FIG. 6 shows a graph connecting various frequency change rates RoCoF and RoCoF detection times corresponding to the frequency change rates RoCoF. At each frequency change rate RoCoF, the islanding operation is not detected in the RoCoF detection time below the line in the graph, and the islanding operation is detected in the RoCoF detection time above the line in the graph. Thereby, the user can grasp the RoCoF detection time, which is the boundary where islanding is detected, for each frequency change rate RoCoF.

  The output unit 43 outputs the information based on the RoCoF tolerance and the relationship between the frequency change rate RoCoF and the RoCoF detection time corresponding to the frequency change rate RoCoF to an operation screen. You may output to an apparatus.

  Thereby, for example, the person in charge of the power company can use the calculation device 10 to know the RoCoF tolerance for each PCS model and the RoCoF detection time for each frequency change rate RoCoF, and the dropout of each PCS model occurs. Easy to understand. The person in charge of the power company can evaluate the stability of the system with respect to the frequency change using the calculated RoCoF tolerance and the RoCoF detection time for each frequency change rate RoCoF.

  In addition, for example, the person in charge of the PCS meter can use the calculation device 10 to evaluate whether the islanding detection function of the PCS operates properly with respect to the frequency change. Also, the person in charge of the PCS meter can use the calculation device 10 to adjust the set value of the PCS islanding operation detection function so that the islanding operation detection function of the PCS performs an assumed operation.

[Processing flow]
Next, the flow of a calculation process in which the calculation device 10 according to the present embodiment calculates the RoCoF resistance will be described. FIG. 7 is a flowchart illustrating an example of the procedure of the calculation process. This calculation process is executed at a predetermined timing, for example, at a timing when the reception unit 40 receives an instruction to start calculating the RoCoF tolerance.

As illustrated in FIG. 7, the first calculation unit 41 determines that the power frequency changes from the initial value f _{0 at a} constant frequency change rate based on various types of information received by the reception unit 40, moving average power of the frequency of the periods t _n between the elapsed time t _r limit value before the frequency change rate difference is a threshold [Delta] t _t of the moving average of the frequency of past second period t _p of (RoCoF Is calculated (S10). For example, the first calculation unit 41, receiving unit the initial value f ₀ accepted 40, the first period t _n, a second time period _{t p,} age t _r, and, from the threshold [Delta] T _t, the above-mentioned The RoCoF tolerance is calculated using the equation (5-2).

Second calculating section 42, calculated RoCoF capability, based on the second time period _{t p} and age t _r, with respect to a multiple of the frequency change ratio relative to RoCoF capability, the detection period required for the detection of the falling, the second period t _{p +} t _r where the sum of the duration t _p and the elapsed time t _r of as being inversely proportional to calculate the condition of the detection period and the frequency change rate at the boundary of dropping occurs (S11). For example, the second calculating unit 42, the above-mentioned (6), by substituting RoCoF tolerance and duration _t p + t _r, variously changing the frequency change rate RoCoF, RoCoF detection time corresponding to the frequency change rate RoCoF I do.

  The output unit 43 outputs the calculation result (S12), and ends the processing. For example, the output unit 43 outputs the calculated RoCoF tolerance to the operation image. In addition, the output unit 43 graphically displays the relationship between the frequency change rate RoCoF and the RoCoF detection time corresponding to the frequency change rate RoCoF on the operation screen.

[Specific example of calculation]
Next, a specific example of calculating the RoCoF resistance using the calculation device 10 will be described. On the website of the Japan Electrical Manufacturers' Association (JEMA) (https://www.jema-net.or.jp/Japanese/res/fukusudai/kenshutsu.html), the detection method, judgment logic, and settings for the islanding detection function The value is released to some extent, and a plurality of identical models are grouped.

  Although the timing is strictly different, the timing at which the FRT requirement is determined and the timing at which sales of the new active type frequency feedback method with step injection are started are close. For this reason, in the present embodiment, a model in which the frequency feedback method with step injection is not adopted is regarded as an FRT non-compliant model. Among the 52 groups of FRT non-compliant models, 49 groups corresponded to the models to which the method according to the present embodiment is considered applicable.

8A and 8B are diagrams illustrating a detection method, a determination logic, and a set value of the islanding operation detection function. 8A and 8B show the detection method, the determination logic, and the set values for each of the 49 groups for which the method according to the present embodiment is considered to be applicable. The group of PCS models shown in FIGS. 8A and 8B uses the group described on the Web page of the Japan Electrical Manufacturers' Association. The item of the method indicates the detection method of the islanding operation detection function, where “place” indicates the voltage phase jump detection method and “lap” indicates the frequency change rate detection method. item t _p indicates the set value of the second time period _{t p.} item t _n indicates the set value of the first time period t _n. item of t _r shows the set value of the elapsed time period t _r. Item [Delta] T _t indicates the set value of the threshold [Delta] T _t, a threshold value corresponding to a detection method (2-1) or (2-2) threshold [Delta] T _t [sec] by formula Are shown corresponding to the reference frequencies 50 Hz and 60 Hz of the power of the system.

8A and 8B, in the item of RoCoF resistance, the set values and the RoCoF resistance calculated by the above equation (5) are shown corresponding to the reference frequencies 50 Hz and 60 Hz of the power of the system. However, as shown in FIG. 8A and FIG. 8B, there are some FRT non-compliant models whose setting values necessary for calculating the RoCoF resistance from Equation (5) are partially unknown. Therefore, if the second time period t _p and the detection threshold considered variations depending on the model is large is unknown, was unknown to RoCoF resistance. For unknown first period t _n, the first time period t _n and 1cyc as a provisional value, when the elapsed time t _r is unknown, FIGS. 8A and 8B, the elapsed time t _r = first since often a tendency can read period t _n of the elapsed time t _r as the first time period t _n and equivalent was calculated RoCoF resistance. 8A and 8B, a pattern is attached to the item of the RoCoF resistance of the model whose calculated RoCoF resistance is less than 2 [Hz / sec].

As shown in FIGS. 8A and 8B, the second time period _{t p,} as the elapsed time t _r is large, also, as the threshold value [Delta] T _t, the first time period t _n small, RoCoF capability decreases. Further, even if the model does not support the FRT, the model whose RoCoF tolerance is less than the FRT requirement of 2 [Hz / sec] is limited. However, the frequency change rate detection method, the second time period t _p is large, further, there RoCoF withstand capability are very small model by threshold [Delta] T _t is small.

Further, even if the determination logic and the set value are the same, the RoCoF resistance is basically 1.44 times or 1.2 times larger when the reference frequency is 50 Hz and 60 Hz. The reason for this is that in equation (5-2), ΔT _t · f ₀ is a dimensionless quantity, and when the way of giving the denominator t is “the number of cycles”, the denominator is proportional to the reciprocal of f _0. tolerance is proportional to the f ₀ ^2. This corresponds to the voltage phase jump detection method in many cases. On the other hand, if the way given the denominator of "second", since the denominator becomes constant without depending on f _0, RoCoF capability is proportional to f _0. This often corresponds to the frequency change rate detection method. In FIGS. 8A and 8B, there are models whose setting values required for calculating the RoCoF tolerance are partially unknown. If the set value becomes clear by providing information from the PCS maker or the like, the calculation accuracy of the RoCoF amount is improved.

  Next, the validity of the calculated RoCoF tolerance and the RoCoF detection time will be verified. In order to verify the validity of the RoCoF tolerance, two representative B, N, H, and S groups were selected from the voltage phase jump detection method and the frequency change rate detection method with reference to FIGS. 8A and 8B. Then, using the method according to the present embodiment, the RoCoF resistance was calculated from the set values of the PCS models of each group. FIG. 9A is a diagram showing the RoCoF resistance at a reference frequency of 50 Hz. FIG. 9B is a diagram showing the RoCoF resistance at a reference frequency of 60 Hz. FIG. 9A and FIG. 9B also show the set values of the PCS models of the groups B, N, H, and S.

  Also, for example, according to the technology described in Non-Patent Document 1, for each group of B, N, H, and S, the lower system in which the PV cooperates using the Y method PV model with the set values of FIGS. 9A and 9B. Was constructed, and simulation analysis was performed to determine whether or not the individual operation was determined in each detection method when the frequency decreased in a ramp shape by changing the frequency change rate at each of the reference frequencies 50 Hz and 60 Hz. In the simulation analysis, the lower limit value of the ramp-shaped frequency fluctuation was set to 47.5 Hz at a reference frequency of 50 Hz, and set to 57.0 Hz at a reference frequency of 60 Hz. The calculation was terminated when 20 [sec] had elapsed after the start of the frequency fluctuation.

  FIG. 10A is a diagram illustrating a frequency change rate obtained by performing a simulation analysis on the reference frequency of 50 Hz. FIG. 10B is a diagram illustrating a frequency change rate obtained by performing a simulation analysis on the reference frequency of 60 Hz. The RoCoF tolerance of each group is different. For this reason, FIGS. 10A and 10B show the frequency change rate of the RoCoF resistance amount as 100% and the ratio of the frequency change rate in the simulation as a frequency change level as a% value.

  FIG. 11A is a diagram showing the result of the presence or absence of dropout by simulation analysis at a reference frequency of 50 Hz. FIG. 11B is a diagram showing the result of the presence or absence of dropout by simulation analysis at a reference frequency of 60 Hz. FIGS. 11A and 11B show the presence or absence of dropout at a frequency variation level where the frequency change rate of the RoCoF resistance is 100%. “O” indicates that the independent operation of the detection method did not operate in the simulation analysis, and the operation in cooperation with the grid continued. “×” indicates that islanding was detected in simulation analysis and dropped out.

  As shown in FIG. 11A and FIG. 11B, each group was “×” with respect to the RoCoF resistance (100% value), and it was confirmed that the accuracy was generally good. However, in the groups N and S, the difference between the calculated RoCoF resistance (100% value) and the frequency fluctuation level at which the isolated operation was detected in the simulation result was relatively large.

  Therefore, the cause is considered by comparing the case where the frequency fluctuation level of the frequency fluctuation level is 97% to each group.

  FIG. 12A is a diagram illustrating a result of the simulation analysis of the group B. FIG. 12A (A) shows a change in the power frequency when the frequency is reduced at a frequency change rate of 4.414 [Hz / sec] with a frequency variation level of 97% at a reference frequency of 60 Hz. I have. FIG. 12A (B) shows a change in the period deviation ΔT when the power frequency changes as in FIG. 12A (A).

When the frequency change rate is 4.414 [Hz / sec], the frequency increases from 60 Hz to 57 Hz when about 0.68 [sec] has elapsed after the start of the frequency change. On the other hand, the period _t p + _{t r} is a 0.55 [sec], the difference is about 0.13 [sec]. Cycle deviation ΔT after the period t _{p +} t _r from frequency fluctuation start has elapsed, but increases gradually cause an error, because the time is short and 0.15 [sec], techniques and Y according to the present embodiment It is considered that the deviation from the simulation result by the formal PV model is small.

  FIG. 12B is a diagram illustrating a result of a simulation analysis of N groups. FIG. 12B (A) shows a change in the power frequency when the frequency is reduced at a frequency change rate of 0.580 [Hz / sec], which is a 97% value of the frequency fluctuation level at a reference frequency of 60 Hz. I have. FIG. 12B (B) shows a change in the period deviation ΔT when the power frequency changes as in FIG. 12B (A).

When the frequency change rate is 0.580 [Hz / sec], the frequency increases from 60 Hz to 57 Hz when about 5.2 [sec] has elapsed after the start of the frequency fluctuation. In contrast, the period _t p + t _r are the 0.33 [sec], the difference is about 4.8 [sec]. Cycle deviation ΔT after the period t _{p +} t _r from frequency fluctuation start has elapsed, but increases gradually cause an error, because the time is long and 4.8 [sec], techniques and Y according to the present embodiment It is considered that the deviation from the simulation result by the forensic PV model became large.

  FIG. 12C is a diagram illustrating a result of the simulation analysis of the group H. FIG. 12C (A) shows a change in the power frequency when the frequency is reduced at a frequency change rate of 0.0338 [Hz / sec], which is a 97% value of the frequency fluctuation level at a reference frequency of 60 Hz. I have. FIG. 12C (B) shows a change in the period deviation ΔT when the power frequency changes as in FIG. 12C (A).

When the frequency change rate is 0.0338 [Hz / sec], the frequency increases from 60 Hz to 57 Hz when about 88.8 [sec] has elapsed after the start of the frequency change. In this embodiment, the simulation time is stopped at 20 [sec] from the start of the frequency fluctuation. In contrast, the period _t p + t _r are the 10.2 [sec], the difference is 9.8 [sec]. Cycle deviation ΔT after the period t _{p +} t _r from frequency fluctuation start has passed, although the increasing moderately error factors, since the change rate of the frequency is very gradual, cycle after age t _{p +} t _r The increase in the deviation ΔT is also very slow. Therefore, in the case of the group H, it is considered that the discrepancy between the method according to the present embodiment and the simulation result by the PV model for the Y method is small because the degree of influence of the error factor is relatively small.

  FIG. 12D is a diagram illustrating a result of the simulation analysis of the group S. FIG. 12D (A) shows a change in the power frequency when the frequency is reduced at a frequency change rate of 0.862 [Hz / sec], which is a 97% frequency change level for a reference frequency of 60 Hz. I have. FIG. 12D (B) shows a change in the period deviation ΔT when the power frequency changes as in FIG. 12D (A).

The simulation result of the group S has the same consideration as that of the group N. When the frequency change rate is 0.862 [Hz / sec], the frequency increases from 60 Hz to 57 Hz at about 3.5 [sec] after the start of the frequency change. On the other hand, the period _t p + _{t r} is, because it is a 1.10 [sec], the difference is about 2.4 [sec]. Since cycle deviation ΔT after the period t _{p +} t _r from frequency fluctuation start has passed, although the increasing moderately error factors, long and the time is 2.4 [sec], techniques and Y according to the present embodiment It is considered that the deviation from the simulation result by the forensic PV model became large.

From the above, the error factors can be arranged as follows. The degree of increase in the period t _{p +} t _r is cycle deviation ΔT after a lapse of the error. As the frequency change rate is large, the degree of increase in the period t _{p +} t _r after the cycle deviation ΔT becomes large. Only time to frequency stops decreasing and duration t _{p +} t _r and error time due to the difference, depending on the frequency change rate, cycle deviation ΔT increases.

  As described above, the method according to the present embodiment is generally good in terms of accuracy as a whole, although some errors occur in some groups.

  Next, the validity of the RoCoF detection time will be verified. For the groups of N, H, and S whose RoCoF tolerance was calculated to be 2 [Hz / sec] or less, various frequency change rates RoCoF and RoCoF detection times corresponding to the frequency change rates RoCoF at the reference frequencies 50 Hz and 60 Hz, respectively. Was calculated.

  Further, for example, by using the technology described in Non-Patent Document 1, a model of a lower system in which PVs cooperate is constructed for each group of N, H, and S using a PV model for the Y method, and the reference frequency is 50 Hz and 60 Hz. Simulation analysis was performed to determine whether or not the islanding operation was determined in each detection method when the frequency decreased in a ramp shape by changing the frequency change rate.

  FIG. 13A is a graph showing the relationship between the frequency change rate RoCoF of the group of N, H, and S and the RoCoF detection time corresponding to the frequency change rate RoCoF for the reference frequency of 50 Hz. FIG. 13B is a graph showing the relationship between the frequency change rate RoCoF of the group of N, H, and S and the RoCoF detection time corresponding to the frequency change rate RoCoF for the reference frequency of 60 Hz. 13A and 13B are graphs showing the relationship between the frequency change rate RoCoF of the group of N, H, and S and the RoCoF detection time corresponding to the frequency change rate RoCoF. 13A and 13B show, for the groups of N, H, and S, the RoCoF detection time corresponding to the frequency change rate RoCoF for which the single operation was not determined by the simulation analysis using the PV model for the Y method is “ × ”. As shown in FIG. 13A and FIG. 13B, the “×” and the graph correspond to each other, and it can be confirmed that the RoCoF detection time by the method according to the present embodiment is approximately appropriate.

  Further, the graphs of FIGS. 13A and 13B show the dropout areas for each model of the groups N, H, and S. That is, when the RoCoF and the RoCoF detection time fall within the upper side of the graph, it is possible to simply estimate the model that will be dropped, assuming that the detection method of that model performs unnecessary operation. For this reason, if a drop-out area as shown in the graphs of FIGS. 13A and 13B is obtained in advance for each PCS model, the drop-out area may drop with respect to the level of the ramp-like frequency fluctuation and the duration thereof regardless of the simulation. It is possible to efficiently grasp the PCS model with the information.

  Further, the dropout area for each model of PCS obtained by the method according to the present embodiment is combined with information such as the distribution of each model and the output prediction based on the amount of solar radiation, so that the dropout amount of PV in the event of frequency fluctuation is obtained. It can be used for simple and fast estimation.

[effect]
As described above, the calculation device 10 according to the present embodiment assumes that the power frequency changes at a constant frequency change rate from the predetermined initial value f _{0, and} determines that the power frequency in the latest first period t _n the difference between the moving average of the frequency of past power of the second time period t _p of the moving average and a predetermined elapsed time period t _r previous calculates the limit value of the frequency change ratio which threshold value (RoCoF tolerance). The calculation device 10 outputs information based on the calculated limit value. Thereby, the user can acquire the limit value of the frequency change rate at which the PCS does not drop out of the calculation device 10 without constructing a PCS model and performing simulation. As a result, the user can easily estimate whether the PCS will drop out of the limit value.

Also, calculating device 10 according to this embodiment, the moving average of the frequency of the electric power of the first time period t _n the frequency of the intermediate point of the first period t _n, the frequency of the power of the second time period t _p the moving average as a frequency of the intermediate point of the second period t _p, calculates the limit value. Thereby, the calculation device 10 can simplify the calculation for obtaining the moving average, and can easily calculate the limit value.

Also, calculating device 10 according to this embodiment, the initial value f _0, a first time period t _n, age t _r, the second time period _{t p,} the threshold [Delta] T _t, the above-mentioned (5-2) The limit value (RoCoF tolerance) is calculated by the equation. Thus, the calculation device 10 can calculate the limit value without performing a simulation that builds a PCS model.

Also, calculating device 10 according to this embodiment, when the detection method of the independent operation detecting function is a voltage phase jump detection method, using the threshold [Delta] [theta] _t of the voltage phase jump detection method (2-1) below The threshold value ΔT _t is calculated, and if the detection method of the islanding detection function is the frequency change rate detection method, the threshold value is calculated from the threshold value Δf _t of the frequency change rate detection method using the equation (2-2). Calculate ΔT _t . Thereby, the calculation device 10 can calculate the limit value of the frequency change rate at which the PCS does not drop out by the same method for the voltage phase jump detection method and the frequency change rate detection method.

Also, calculating device 10 according to this embodiment, the calculated limit value (RoCoF capability), based on the second time period t _p and age t _r, with respect to a multiple of the frequency change ratio relative to the limit value, the dropout detection period required for detection, as being inversely proportional to the period t _{p +} t _r, calculates the condition of the detection period and the frequency change rate at the boundary dropouts occurs. The calculation device 10 outputs information based on the calculated conditions. Thereby, the calculation device 10 can provide the condition of the frequency change rate and the detection period, which are the boundaries where the dropout occurs.

  Further, the calculation device 10 according to the present embodiment displays the relationship between the frequency change rate and the detection period in a graph based on the condition. Thereby, the user can grasp the frequency change rate and the detection period, which are boundaries where dropout occurs, from the displayed graph.

  [B] Second Embodiment Although the embodiments related to the disclosed apparatus have been described above, the disclosed technology may be implemented in various different forms other than the above-described embodiments. Therefore, another embodiment included in the present invention will be described below.

For example, in the above-described embodiment, a case has been described in which the input of various setting values used for calculating the RoCoF tolerance is received from the operation screen. However, the disclosed device is not limited to this. For example, some or all of the various set values may be stored as data, and some or all of the various set values may be read from the data to calculate the RoCoF tolerance. For example, calculating apparatus 10, an initial value f ₀ of the frequency of the power, the first time period t _n, a second time period t _p, using the data stored set value of the elapsed time t _r and the threshold value [Delta] T _t The RoCoF resistance may be calculated.

Further, in the above-described embodiment, the case where the term of (df / dt) ² is excluded from the above equation (5-1) has been described, but the disclosed device is not limited to this. For example, RoCoF tolerance may be calculated from an expression including the term (df / dt) ² . For example, when a, b, and c are expressed as in the following (7-2)-(7-4), the frequency change rate is calculated from the above equation (4) as in the following equation (7-1). An expression for df / dt is obtained. The boundary of the inequality in (7-1)) corresponds to the RoCoF tolerance. Thereby, the RoCoF tolerance can be calculated more accurately.

  Each component of each device illustrated is a functional concept, and does not necessarily need to be physically configured as illustrated. In other words, the specific state of distribution / integration of each device is not limited to the one shown in the figure, and all or a part of it is functionally or physically distributed / arbitrarily divided into arbitrary units according to various loads and usage conditions. Can be integrated and configured. For example, the processing units of the reception unit 40, the first calculation unit 41, the second calculation unit 42, and the output unit 43 may be appropriately integrated. Further, the processing of each processing unit may be appropriately separated into the processing of a plurality of processing units. Further, all or any part of each processing function performed by each processing unit may be realized by a CPU and a program analyzed and executed by the CPU, or may be realized as hardware by wired logic. .

[Frequency change rate tolerance calculation program]
The various processes described in the above embodiments can also be realized by executing a prepared program on a computer system such as a personal computer or a workstation. Therefore, an example of a computer system that executes a program having the same function as the above embodiment will be described below. FIG. 14 is a diagram illustrating a computer that executes a calculation program.

  As shown in FIG. 14, the computer 300 includes a CPU (Central Processing Unit) 310, a HDD (Hard Disk Drive) 320, and a RAM (Random Access Memory) 340. These units 300 to 340 are connected via a bus 400.

  The HDD 320 stores in advance a calculation program 320a that performs the same functions as those of the reception unit 40, the first calculation unit 41, the second calculation unit 42, and the output unit 43. Note that the calculation program 320a may be separated as appropriate.

  The HDD 320 stores various information. For example, the HDD 320 stores various data used for calculating the RoCoF tolerance.

  Then, the CPU 310 reads out the calculation program 320a from the HDD 320 and executes the same to execute the same operation as each processing unit of the embodiment. That is, the calculation program 320a performs the same operation as the reception unit 40, the first calculation unit 41, the second calculation unit 42, and the output unit 43.

  Note that the above-described calculation program 320a does not necessarily need to be stored in the HDD 320 from the beginning.

  For example, the program is stored in a “portable physical medium” such as a flexible disk (FD), a CD-ROM, a DVD disk, a magneto-optical disk, or an IC card inserted into the computer 300. Then, the computer 300 may read out the program from these and execute it.

  Further, the program is stored in “another computer (or server)” connected to the computer 300 via a public line, the Internet, a LAN, a WAN, or the like. Then, the computer 300 may read out the program from these and execute it.

Reference Signs List 10 calculation device 20 display unit 21 input unit 22 storage unit 23 control unit 40 reception unit 41 first calculation unit 42 second calculation unit 43 output unit

Claims (8)

Assuming that the power frequency changes at a constant rate of change from a predetermined initial value, the moving average of the power frequency of the latest first period and the power frequency of the past second period before the predetermined elapsed period Calculate a limit value of the frequency change rate at which the difference from the moving average becomes a threshold value,
A computer-readable storage medium storing a program for causing a computer to execute a process of outputting information based on the calculated limit value. The processing of calculating the limit value may be performed by setting a moving average of the power frequency in the first period as a frequency at an intermediate point of the first period, and calculating a moving average of the power frequency in the second period as the second average. The frequency change rate tolerance calculation program according to claim 1, wherein the limit value is calculated as a frequency at an intermediate point of the period. Processing for calculating the limit value, the initial value is set to f _0, the first period as the t _n, the elapsed time and t _r, the second period and t _p, the threshold The program according to claim 1, wherein when ΔT _t is set, the limit value is calculated from Expression (1).

If the threshold was set to [Delta] T _t, when the detection method of the independent operation detecting function is a voltage phase jump detection method using the threshold value [Delta] [theta] _t of the voltage phase jump detection method of (2-1) below the The threshold ΔT _t is calculated, and when the detection method of the islanding operation detection function is the frequency change rate detection method, the threshold is calculated from the threshold value Δf _t of the frequency change rate detection method by using the expression (2-2). The program according to claim 1, wherein the value ΔT _t is calculated.

Based on the calculated limit value, the second period, and the elapsed period, a detection period required for detecting dropout is a second period and the elapsed period for a multiple of a frequency change rate with respect to the limit value. And the computer further executes a process of calculating a condition of the detection period and a frequency change rate which is a boundary at which dropout occurs, as being inversely proportional to the addition period obtained by adding
5. The non-transitory computer-readable recording medium according to claim 1, wherein the outputting includes outputting information based on the calculated condition. 6. The computer-readable storage medium according to claim 5, wherein, in the output processing, a relationship between a frequency change rate and the detection period is displayed in a graph based on the condition. Assuming that the power frequency changes at a constant rate of change from a predetermined initial value, the moving average of the power frequency of the latest first period and the power frequency of the past second period before the predetermined elapsed period Calculate a limit value of the frequency change rate at which the difference from the moving average becomes a threshold value,
A computer executes a process of outputting information based on the calculated limit value, wherein the computer executes the process. Assuming that the power frequency changes at a constant rate of change from a predetermined initial value, the moving average of the power frequency of the latest first period and the power frequency of the past second period before the predetermined elapsed period A calculation unit that calculates a limit value of the frequency change rate at which a difference from the moving average becomes a threshold value,
An output unit that outputs information based on the limit value calculated by the calculation unit,
A frequency change rate tolerance calculation device, comprising:

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