JP7007994B2 - Frequency change rate tolerance calculation program, calculation method and calculation device - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act Published on pages 493 and 494 of the Proceedings of the 2018 National Conference of the Institute of Electrical Engineers of Japan, published on March 5, 2018.

Application of Article 30, Paragraph 2 of the Patent Act On June 1, 2018, it was published on the website of the Research Report of the Central Research Institute of Electric Power Industry.

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

Renewable energy power sources, especially photovoltaic power generation (hereinafter also referred to as “PV”), are being introduced toward the realization of a low-carbon society. In the power system that supplies power to the power receiving equipment of consumers (hereinafter also referred to as "system"), with the expansion of the introduction of PV, not only the supply and demand operation in normal times but also the stability in an emergency becomes apparent. It is becoming.

If the output of PV increases for a certain demand, the electric power company needs to reduce the output of the existing synchronous generator (generator). It may be stopped. At this time, the decrease in the capacity of the generators parallel to the system means that the inertia and voltage maintenance capacity of the entire system decrease, and the frequency stability and transient stability in the event of a system accident may decrease. There is. For example, when a large power source is dropped or the system is separated, the rotation speed of the generator left in the system is likely to change due to the decrease in inertia. Therefore, the frequency change rate (RoCoF: Rate of Change of Frequency) of the electric power flowing through the system tends to increase. The frequency change rate can be expressed as | df / dt | as a change in the frequency f of the power supplied to the system per unit time.

The PV is connected to the grid via a power conditioner (PCS). The PCS basically has a solitary operation detection function, and determines the solitary operation based on the periodic deviation or the frequency deviation of the interconnection point voltage. In a system in which a large amount of PV is connected, if the PV drops all at once, disturbances such as voltage fluctuation and frequency fluctuation occur in the power of the system, which causes a great deterioration in power quality. The term "dropped out" here means a state in which the PCS cannot recover due to an abnormal system condition after the gate block.

Therefore, at present, in Japan, the requirements for continued operation in the event of an accident (Fault Ride Through) (hereinafter, also referred to as "FRT requirements") are stipulated. The FRT requirement requires that the PCS continue to operate in cooperation with the grid for frequency fluctuations of ± 2 [Hz / sec]. The solitary operation detection function of the PCS needs to be designed to meet the FRT requirements. On the other hand, there are some PCS models that do not support FRT before the FRT requirements are set. For PCS models that do not support FRT, there is a risk that RoCoF will drop even if it does not reach ± 2 [Hz / sec].

For this reason, in the event of a large power supply dropout accident, voltage phase jump and frequency drop occur, so there is a risk that PCS models that do not support FRT will drop out in a wide range due to unnecessary operation of the detection method of the independent operation detection function, which will promote frequency drop. be.

The set value of the independent operation detection function differs depending on the PCS model, and there is a difference in RoCoF in which dropout occurs. Therefore, at present, various independent operation detection functions are individually modeled, and the dropout of the PCS model is estimated by simulation analysis or the like that gives a desired frequency fluctuation.

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

Keisuke Shirasaki, Yoshihiro Kitauchi, "Basic effects of various system conditions on the system stability of the backbone system when a large amount of renewable energy is introduced", Central Research Institute of Electric Power Industry Report R14013, August 2015

However, with the conventional technology, it is necessary to build a model for each PCS model and perform simulation analysis, and it is not possible to easily estimate whether or not the PCS will drop out.

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

In order to solve the above-mentioned problems and achieve the object, the frequency change rate tolerance calculation program of the present invention is most recent to the computer, assuming that the frequency of the power changes from a predetermined initial value to a constant frequency change rate. Calculate the limit value of the frequency change rate at which the 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 is the threshold value. , It is characterized in that a process of outputting information based on the calculated limit value is executed.

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

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

Hereinafter, examples of the frequency change rate tolerance calculation program, calculation method, and calculation device according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. Then, each embodiment can be appropriately combined as long as the processing contents do not contradict each other.

[Calculation method of frequency change rate withstand (RoCoF withstand)]
First, a method for calculating the limit value of the frequency change rate (RoCoF) at which the PCS does not fall off (frequency change rate withstand, hereinafter also referred to as “RoCoF withstand”) will be described. As described above, the FRT requirement requires the PCS to continue operation in cooperation with the grid against frequency fluctuations of ± 2 [Hz / sec]. The solitary operation detection function of the PCS needs to be designed to meet the FRT requirements. On the other hand, there are some PCS models that do not support FRT before the FRT requirements are set. For PCS models that do not support FRT, there is a risk that RoCoF will drop even if it does not reach ± 2 [Hz / sec].

The independent operation detection function of the model that does not support FRT has 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 a determination logic. In the frequency change rate detection method and the voltage phase jump detection method, the independent operation is basically determined based on whether or not the cycle deviation between the recent cycle and the past cycle calculated by the moving average exceeds the threshold value. For example, in the frequency change rate detection method and the voltage phase jump detection method, the moving average of the power cycle of the first period t _n most recent from the time t _{1 and the time t 1 are used as the reference for the time t 1 to be} determined. From, the moving average of the power cycle of the past second period _{t p} before the predetermined elapsed period tr is calculated, and the moving average of the cycle of the first period t _n and the movement of the cycle of the second period t _p . The independent operation is determined based on whether the difference from the average exceeds the threshold value. Therefore, it is considered that the frequency change rate detection method and the voltage phase jump detection method have the same basic determination logic. The cycle of AC power is the reciprocal of the frequency of 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 _tp is the _reciprocal of the moving average _fp of the frequency of the second period tp.

FIG. 2 is a diagram showing an example of a change in the periodic deviation with respect to a change in the frequency of electric power. FIG. 2A shows a change in frequency when the frequency of electric power fluctuates like a lamp. A ramp-like variation in the frequency of electric power is a state in which the frequency increases or decreases at a constant frequency change rate. In FIG. 2A, the frequency of the power is the frequency of the initial _{value f 0 to} 0.5 [Hz / sec], 1.0 [Hz / sec], 2.0 [Hz / sec] at the time ts. It shows the state of decrease in the rate of change. The initial value f ₀ is, for example, a reference frequency of electric power (50 Hz or 60 Hz).

FIG. 2B shows an example of a change in the periodic deviation when the frequency of electric power fluctuates like a ramp. FIG. 2B shows the change in the periodic deviation ΔT when the power frequency decreases at the frequency change rates of 0.5 [Hz / sec], 1.0 [Hz / sec], and 2.0 [Hz / sec], respectively. It is shown. As shown in FIG. 2B, for the periodic deviation ΔT, the second period _tp and the elapsed period _tr after the lamp-shaped frequency fluctuation starts at the time _ts are added regardless of the magnitude of the frequency change rate. It increases rapidly until the period _{t p} + tr has passed. Then, the periodic deviation ΔT gradually increases after the lapse of the period _{t p} + tr.

Here, the present inventor simplifies the RoCoF withstand capability that does not cause the PCS to drop out from the set values of the determination logics related to the frequency change rate detection method and the voltage phase jump detection method when the power frequency fluctuates like a ramp. I devised the method required for. In this embodiment, the influence of the on-delay timer for preventing unnecessary operation due to the voltage phase jump is not considered because it affects the detection time but does not affect the RoCoF withstand capability.

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

In the determination logic of the frequency change rate detection method and the voltage phase jump detection method, the moving average f _n of the power frequency in the first period t _n most recent from the time t _{1 is set based on the time t 1 to} be determined. The moving average f _p of the frequency of the power of the past second period _{t p} before the elapsed period tr from the time t ₁ is calculated respectively.

When the frequency of the electric power changes like a ramp, the larger the frequency change rate of the electric power, the larger the periodic deviation ΔT calculated in the determination logic. The frequency change rate detection method and the voltage phase jump detection method are determined to be in a single operation state when the periodic deviation ΔT exceeds the periodic conversion threshold value ΔT _t . This determination condition can be expressed by the following equation (1).

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

As shown in FIG. 2B, the periodic deviation ΔT increases rapidly from the start of the ramp-shaped frequency fluctuation until the period _{t p} + tr e elapses, regardless of the magnitude of the frequency change rate. Therefore, it is considered that the level of ramp-shaped frequency fluctuation at which the periodic deviation ΔT reaches the threshold value ΔT _t after the period _{t p} + tr has elapsed roughly corresponds to the _RoCoF tolerance, and the moving average at the time when the period t _p + tr has passed. Consider formulating f _n , the moving average f _p , and the periodic deviation ΔT.

When the frequency of electric power fluctuates like a ramp with a frequency change rate df / dt <0, as shown in FIG. 3, the moving average f _n of the frequency in the first period t _n is the first period t _n . It can be thought of as the frequency of the midpoint. Further, the moving average of the period of the second period _tp can be considered as the frequency of the midpoint of the second period _tp . Therefore, for the moving average f _n and the moving average f _p , the first period t _n , the second period _{t p} , the elapsed period tr, the frequency change rate df / dt, and the initial value f ₀ of the frequency are used. It is expressed by the following equations (3-1) and (3-2).

The following equation (4) can be obtained by combining the above equations (1) and the above equations (3), which are the conditions for detecting independent operation. That is, it means that the independent operation is detected when the inequality of the equation (4) holds, and the frequency change rate df / dt when the equal sign holds corresponds to the RoCoF withstand capability.

Here, when the typical setting values of PCS shown in FIGS. 8A and 8B described later are given, the absolute value of the item (df / dt) ² on the right side is sufficiently smaller than the other items in each case. Become. Therefore, if the term (df / dt) ² is removed from the equation (4), the approximate equation of RoCoF can be obtained as the following equation (5-1). When the inequality of Eq. (5-1) holds, Eq. (5-2) corresponds to the RoCoF withstand capacity.

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

FIG. 4 is a diagram showing an example of a change in the periodic deviation ΔT of the period _{t p} + tr. As shown in FIG. 4, the increase in the periodic deviation ΔT draws an S-shaped curve from the start of the frequency fluctuation to the elapse of the period _{t p} + tr. Focusing on the fact that the deviation of the moving average _fp of the power frequency with respect to the initial value f ₀ of the frequency is relatively small in the period _{t p} + tr, if the degree of increase in the periodic deviation ΔT is simply regarded as linear, the periodic deviation The slope of the increase in ΔT and the RoCoF detection time are almost inversely proportional to each other. That is, it can be considered that the RoCoF detection time when the frequency change rate of n (> 1) times the RoCoF tolerance occurs is 1 / n times. This relationship can be expressed by the following equation (6). In this embodiment, the influence of the on-delay timer is not taken into consideration, but if it is taken into consideration, the timer time may be added to the RoCoF detection time represented by the following equation (6).

By using this equation (6), the detection period (RoCoF detection period) in which dropout is detected at the frequency change rate RoCoF can be calculated for each frequency change rate RoCoF.

[Configuration of calculation device]
Next, the configuration of the calculation device 10 to which the above-mentioned RoCoF tolerance calculation method is applied will be described. FIG. 5 is a diagram showing an example of a functional configuration of the calculation device. The calculation device 10 is an information processing device that calculates the RoCoF withstand capability by 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 portable 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 calculation device 10 may have various known functional units in addition to the functional units shown in FIG. For example, the calculation device 10 may have a communication interface unit or the like that communicates with another terminal.

The display unit 20 is a display device that displays various types of information. Examples of the display unit 20 include 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 an input device such as a keyboard and 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, since the functional configuration is shown, the display unit 20 and the input unit 21 are separately separated. For example, the display unit 20 and the input unit 21 are integrally provided with a device such as a touch panel. You may.

The storage unit 22 is a storage device that stores various types of data. For example, the storage unit 22 is a storage device such as a hard disk, an SSD (Solid State Drive), or an optical disk. The storage unit 22 may be a semiconductor memory in which data such as a RAM (Random Access Memory), a flash memory, and an NVSRAM (Non Volatile Static Random Access Memory) can be rewritten.

The storage unit 22 stores an OS (Operating System) and various programs executed by the control unit 23. For example, the storage unit 22 stores various programs including a calculation program that executes a calculation process described later. Further, the storage unit 22 stores various data used in the 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) or an MPU (Micro Processing Unit) or an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array) can be adopted. The control unit 23 has an internal memory for storing programs and control data that specify various processing procedures, and executes various processing by these. The control unit 23 functions as various processing units by operating various programs. For example, the control unit 23 has a reception unit 40, a first calculation unit 41, a second calculation unit 42, and an output unit 43.

The reception unit 40 receives various types of reception. For example, the reception unit 40 receives input of various information used for calculating the RoCoF withstand capability and various operation instructions. For example, the reception unit 40 displays an operation screen (not shown) on the display unit 20, 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. The input of the second period t _p , the elapsed period tr up to the second period _{t p} , and the threshold value ΔT _t used for the determination is accepted. From the operation screen, the reception unit 40 inputs the threshold value Δθ _t [deg] of the voltage phase jump detection method and the threshold value Δf _t [%] of the frequency change rate detection method as the threshold values used for the determination. May be accepted. Further, the reception unit 40 receives an instruction to start calculation of the RoCoF withstand capacity from an operation screen (not shown).

The first calculation unit 41 assumes that the frequency of the power changes from the initial value f ₀ at a constant frequency change rate based on various information received by the reception unit 40, and determines that the power of the latest first period t _n The RoCoF tolerance is calculated in which the difference between the moving average of the frequency and the moving average of the frequency in the past second period _{t p} before the elapsed period tr is the threshold value ΔT _t . For example, the first calculation unit 41 described above from the initial value f ₀ , the first period t _n , the second period t _p , the elapsed period _tr , and the threshold value ΔT _t received by the reception unit 40. The RoCoF withstand capacity is calculated using the equation (5-2).

When the input of the threshold value Δθ _t and the threshold value Δf _t is accepted as the threshold value used for the determination from the operation screen, the first calculation unit 41 uses the above-mentioned equation (2-1) and (2). -2) After converting to the threshold value ΔT _t [sec] by the equation, the RoCoF withstand capacity is calculated.

The second calculation unit 42 has a second detection period required for detecting dropout with respect to a multiple of the frequency change rate with respect to the _RoCoF tolerance based on the calculated _RoCoF tolerance, the second period tp and the elapsed period tr. Assuming that the period _{t p} + tr, which is the sum of the period _{t p} and the elapsed period tr, is inversely proportional, the frequency change rate and the condition of the detection period, which are the boundaries where the dropout occurs, are calculated. For example, the second calculation unit 42 substitutes the _RoCoF tolerance and the period tp + tr into the above equation (6), changes the frequency change rate _RoCoF in various ways, and sets the RoCoF detection time corresponding to the frequency change rate RoCoF. do.

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

Further, the output unit 43 outputs information based on the conditions 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 as a graph on the operation screen.

FIG. 6 is a diagram showing an example of the displayed graph. FIG. 6 shows a graph connecting various frequency change rates RoCoF and the RoCoF detection time corresponding to the frequency change rate RoCoF. In each frequency change rate RoCoF, the isolated operation is not detected at the RoCoF detection time below the line of the graph, and the isolated operation is detected at the RoCoF detection time above the line of the graph. As a result, the user can grasp the RoCoF detection time, which is the boundary at which the isolated operation is detected, for each frequency change rate RoCoF.

In addition to outputting information based on the RoCoF withstand capability and the relationship between the frequency change rate RoCoF and the RoCoF detection time corresponding to the frequency change rate RoCoF to the operation screen, the output unit 43 outputs data to an external terminal device or storage. It may be output to the device.

As a result, for example, the person in charge of the electric power company can grasp the RoCoF withstand capability for each PCS model and the RoCoF detection time for each frequency change rate RoCoF by using the calculation device 10, and the dropout of each PCS model occurs. You can grasp the ease. The person in charge of the electric power company can evaluate the stability of the system against the frequency change by using the calculated RoCoF withstand capability and the RoCoF detection time for each frequency change rate RoCoF.

Further, for example, the person in charge of the PCS meter can evaluate whether the independent operation detection function of the PCS operates appropriately with respect to the frequency change by using the calculation device 10. Further, the person in charge of the PCS meter can use the calculation device 10 for adjusting the set value of the independent operation detection function of the PCS so that the operation of the independent operation detection function of the PCS is assumed.

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

As shown in FIG. 7, the first calculation unit 41 assumes that the frequency of the power changes from the initial value f ₀ at a constant frequency change rate based on various information received by the reception unit 40, and is the latest first. The limit value of the frequency change rate (RoCoF) in which the difference between the moving average of the frequency of the power of the period t _n and the moving average of the frequency of the second period _{t p} in the past before the elapsed period tr is the threshold value ΔT _t . Withstand capacity) is calculated (S10). For example, the first calculation unit 41 described above from the initial value f ₀ , the first period t _n , the second period t _p , the elapsed period _tr , and the threshold value ΔT _t received by the reception unit 40. The RoCoF withstand capacity is calculated using the equation (5-2).

The second calculation unit 42 has a second detection period required for detecting dropout with respect to a multiple of the frequency change rate with respect to the _RoCoF tolerance based on the calculated _RoCoF tolerance, the second period tp and the elapsed period tr. Assuming that the period _tp + _tr , which is the sum of the period _tp and the elapsed period _tr , is inversely proportional, the frequency change rate and the condition of the detection period, which are the boundaries where the dropout occurs, are calculated (S11). For example, the second calculation unit 42 substitutes the _RoCoF tolerance and the period tp + tr into the above equation (6), changes the frequency change rate _RoCoF in various ways, and sets the RoCoF detection time corresponding to the frequency change rate RoCoF. do.

The output unit 43 outputs the calculation result (S12), and ends the process. For example, the output unit 43 outputs the calculated RoCoF withstand capacity to the operation image. Further, 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 as a graph on the operation screen.

[Specific example of calculation]
Next, a specific example in which the RoCoF withstand capacity is calculated 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 of the independent operation detection function The values are disclosed to some extent, and multiple models with the same value are grouped.

Strictly speaking, the timing is different, but the timing when the FRT requirements are set and the timing when the new active method, the frequency feedback method with step injection, started to be sold are near. Therefore, in this embodiment, a model that does not adopt the frequency feedback method with step injection is regarded as a model that does not support FRT. Of the 52 groups of models that do not support FRT, 49 groups corresponded to the models to which the method according to this embodiment could be applied.

8A and 8B are diagrams showing a detection method, a determination logic, and a set value of the isolated operation detection function. 8A and 8B show the detection method, the determination logic, and the set values for each of the 49 groups to which the method according to this embodiment can be applied. 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 isolated operation detection function, "position" indicates that it is a voltage phase jump detection method, and "circumferential" indicates that it is a frequency change rate detection method. The item of t _p indicates the set value of the second period t _p . The item of t _n indicates the set value of the first period t _n . The item of _tr indicates the set value of the elapsed period _tr . The item of ΔT _t indicates the set value of the threshold value ΔT _t , and the threshold value corresponding to the detection method is set to the threshold value ΔT _t [sec] by the equation (2-1) or (2-2). The values converted to are shown corresponding to the reference frequencies of the grid power of 50 Hz and 60 Hz.

Further, in FIGS. 8A and 8B, in the item of RoCoF withstand capability, these set values and the RoCoF withstand capability calculated by the above equation (5) are shown corresponding to the reference frequencies of 50 Hz and 60 Hz of the power of the system. However, as shown in FIGS. 8A and 8B, there are some models that do not support FRT, in which the set value required for calculating the RoCoF withstand capability from the equation (5) is partially unknown. Therefore, when the second period _tp and the detection threshold value, which are considered to vary greatly depending on the model, are unknown, the RoCoF tolerance is unknown. If the first period _{t n} is unknown, the first period _{t n} is assumed to be 1 cyc, and if the elapsed period tr is unknown, the elapsed period tr = 1st from FIGS. 8A and 8B. Since it can be read that the period t _n of the above is often the _{case, the RoCoF tolerance was calculated by setting the elapsed period tr as the same value as the first period t n .} In FIGS. 8A and 8B, a pattern is attached to the item of the RoCoF tolerance of the model whose calculated RoCoF tolerance is less than 2 [Hz / sec].

As shown in FIGS. 8A and 8B, the larger the second period _{t p} and the elapsed period tr, and the smaller the threshold value ΔT _t and the first period t _n , the smaller the RoCoF tolerance. In addition, even if the model does not support FRT, the model whose RoCoF withstand capacity is less than the FRT requirement of 2 [Hz / sec] is limited. However, in the frequency change rate detection method, there is a model in which the RoCoF withstand capability is very small due to the large second period t _p and the small threshold value ΔT _t .

Further, even if the determination logic and the set value are the same, the RoCoF withstand voltage is basically 1.44 times or 1.2 times larger when the reference frequency is 50 Hz and when the reference frequency is 60 Hz. The reason for this is that in equation (5-2), ΔT _t · f ₀ is a dimensionless quantity, and when the denominator t is given as the “number of cycles”, the denominator is proportional to the reciprocal of f ₀ . Dimensionless quantity is proportional to f ₀ ² . This corresponds to many voltage phase jump detection methods. On the other hand, when the denominator is given in "seconds", the denominator does not depend on f ₀ and is constant, so that the RoCoF tolerance is proportional to f ₀ . This corresponds to many frequency change rate detection methods. In FIGS. 8A and 8B, there is a model in which the set value required for calculating the RoCoF withstand capability is partially unknown. If the set value becomes clear by providing information from the PCS maker, the accuracy of calculating the RoCoF amount will be improved.

Next, the validity of the calculated RoCoF tolerance and RoCoF detection time is verified. In order to verify the validity of the RoCoF withstand capability, 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 this embodiment, the RoCoF withstand capacity was calculated from the set values of the PCS models of each group. FIG. 9A is a diagram showing the RoCoF withstand capability at a reference frequency of 50 Hz. FIG. 9B is a diagram showing the RoCoF withstand capacity at a reference frequency of 60 Hz. 9A and 9B also show the setting values of the PCS models of the groups B, N, H, and S.

Further, for example, by the technique described in Non-Patent Document 1, for each group of B, N, H, and S, the lower system in which PV cooperates using the PV model for the Y method with the set values of FIGS. 9A and 9B. The model was constructed, and simulation analysis was performed to determine whether or not to operate independently in each detection method when the frequency changes in the frequency change rate at the reference frequencies of 50 Hz and 60 Hz, respectively, and the frequency drops like a ramp. In the simulation analysis, the lower limit of the ramp-shaped frequency fluctuation was set to 47.5 Hz at the reference frequency of 50 Hz and 57.0 Hz at the reference frequency of 60 Hz. In addition, the calculation was terminated when 20 [sec] had elapsed from the start of frequency fluctuation.

FIG. 10A is a diagram showing a frequency change rate obtained by performing simulation analysis for a reference frequency of 50 Hz. FIG. 10B is a diagram showing a frequency change rate obtained by performing simulation analysis for a reference frequency of 60 Hz. The RoCoF tolerance of each group is different. Therefore, in FIGS. 10A and 10B, the frequency change rate of the RoCoF tolerance is set to 100%, and the ratio of the frequency change rate at the time of simulation is shown as a% value as the frequency fluctuation level.

FIG. 11A is a diagram showing the result of presence / absence of dropout by simulation analysis at a reference frequency of 50 Hz. FIG. 11B is a diagram showing the result of presence / absence of dropout by simulation analysis at a reference frequency of 60 Hz. In FIGS. 11A and 11B, the presence or absence of dropout is shown at the frequency fluctuation level with the frequency change rate of the RoCoF withstand as 100%. “○” indicates that the independent operation of the detection method did not operate in the simulation analysis, and the operation linked with the system continued. “X” indicates that the isolated operation was detected in the simulation analysis and dropped out.

As shown in FIGS. 11A and 11B, both groups were marked with "x" with respect to the RoCoF withstand capacity (100% value), confirming that the accuracy was generally good. However, in the N and S groups, the discrepancy between the calculated RoCoF tolerance (100% value) and the frequency fluctuation level at which isolated operation is detected in the simulation results was relatively large.

Therefore, the cause will be considered by comparing the cases where the frequency fluctuation level is 97% and the frequency fluctuation is given to each group.

FIG. 12A is a diagram showing the results of simulation analysis of group B. FIG. 12A (A) shows the change in the frequency of the electric power when the frequency is lowered at the frequency change rate of 4.414 [Hz / sec], which is a 97% value of the frequency fluctuation level at the reference frequency of 60 Hz. There is. 12A (B) shows the change in the periodic deviation ΔT when the frequency of the electric power changes as shown in FIG. 12A (A).

When the frequency change rate is 4.414 [Hz / sec], the frequency reaches from 60 Hz to 57 Hz when about 0.68 [sec] has elapsed from the start of the frequency fluctuation. On the other hand, the period _{t p} + tr is 0.55 [sec], and the difference is about 0.13 [sec]. Even after the period _{t p} + tr has elapsed from the start of the frequency fluctuation, the periodic deviation ΔT gradually increases and becomes an error factor, but since the time is as short as 0.15 [sec], the method and Y according to this embodiment. It is considered that the deviation from the simulation result by the legal PV model is also small.

FIG. 12B is a diagram showing the results of simulation analysis of the N group. FIG. 12B (A) shows the change in the frequency of the electric power when the frequency is lowered at a frequency change rate of 0.580 [Hz / sec], which is a 97% value of the frequency fluctuation level at the reference frequency of 60 Hz. There is. FIG. 12B (B) shows the change in the periodic deviation ΔT when the frequency of the electric power changes as shown in FIG. 12B (A).

When the frequency change rate is 0.580 [Hz / sec], the frequency reaches from 60 Hz to 57 Hz when about 5.2 [sec] has elapsed from the start of the frequency fluctuation. On the other hand, since the period _{t p} + tr is 0.33 [sec], the difference is about 4.8 [sec]. Even after the period _{t p} + tr has elapsed from the start of the frequency fluctuation, the periodic deviation ΔT gradually increases and becomes an error factor, but since the time is as long as 4.8 [sec], the method according to this embodiment and Y It is considered that the deviation from the simulation result by the legal PV model has increased.

FIG. 12C is a diagram showing the results of simulation analysis of the group H. FIG. 12C (A) shows the change in the frequency of the electric power when the frequency is lowered at a frequency change rate of 0.0338 [Hz / sec], which is a 97% value of the frequency fluctuation level at the reference frequency of 60 Hz. There is. FIG. 12C (B) shows the change in the periodic deviation ΔT when the frequency of the electric power changes as shown in FIG. 12C (A).

When the frequency change rate is 0.0338 [Hz / sec], the frequency reaches from 60 Hz to 57 Hz when about 88.8 [sec] has elapsed from the start of the frequency fluctuation. In this embodiment, the simulation time is cut off at 20 [sec] from the start of frequency fluctuation. On the other hand, since the period _{t p} + tr is 10.2 [sec], the difference is 9.8 [sec]. The period deviation ΔT gradually increases even after the period _{t p} + tr has elapsed from the start of the frequency fluctuation, which causes an error. However, since the frequency change rate is very slow, the period after the period _{t p} + tr e has elapsed. The increase in deviation ΔT is also very gradual. Therefore, in the case of the group H, it is considered that the degree of influence of the error factor is relatively small, so that the discrepancy between the method according to this embodiment and the simulation result by the PV model for the Y method is small.

FIG. 12D is a diagram showing the results of simulation analysis of the group S. FIG. 12D (A) shows the change in the frequency of the electric power when the frequency is lowered at a frequency change rate of 0.862 [Hz / sec], which is a 97% value of the frequency fluctuation level at the reference frequency of 60 Hz. There is. FIG. 12D (B) shows the change in the periodic deviation ΔT when the frequency of the electric power changes as shown in FIG. 12D (A).

The simulation results of the S group have the same consideration as the N group. When the frequency change rate is 0.862 [Hz / sec], the frequency reaches from 60 Hz to 57 Hz when about 3.5 [sec] has elapsed from the start of the frequency fluctuation. On the other hand, since the period _{t p} + tr is 1.10 [sec], the difference is about 2.4 [sec]. Even after the period _{t p} + tr has elapsed from the start of the frequency fluctuation, the periodic deviation ΔT gradually increases and becomes an error factor, but since the time is as long as 2.4 [sec], the method according to this embodiment and Y It is considered that the deviation from the simulation result by the legal PV model has increased.

From the above, the error factors can be organized as follows. The degree of increase in the periodic deviation ΔT after the period _{t p} + tr has elapsed is an error. The larger the frequency change rate, the greater the degree of increase in the periodic deviation ΔT after the period _{t p} + tr. The periodic deviation ΔT increases according to the frequency change rate by the time of the error due to the difference between the time until the frequency stops falling and the period _{t p} + tr.

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 N, H, and S groups calculated to have a RoCoF tolerance of 2 [Hz / sec] or less, various frequency change rates RoCoF and RoCoF detection times corresponding to the frequency change rates RoCoF, respectively, at reference frequencies of 50 Hz and 60 Hz, respectively. Was calculated.

Further, for example, by the technique described in Non-Patent Document 1, for each group of N, H, and S, a model of a lower system in which PV is linked is constructed by using a PV model for the Y method, and at reference frequencies of 50 Hz and 60 Hz. Simulation analysis was performed to determine whether or not to operate independently in each detection method when the frequency drops like a ramp by changing the frequency change rate.

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

Further, the graphs of FIGS. 13A and 13B show the dropout areas for each model of the N, H, and S groups. That is, when the RoCoF and RoCoF detection times are within the upper side of the graph, it is possible to easily estimate the model to be dropped, assuming that the detection method of the model operates unnecessarily. Therefore, if the dropout area as shown in the graphs of FIGS. 13A and 13B is obtained in advance for each PCS model, the dropout region may drop out with respect to the level and duration of the lamp-shaped frequency fluctuation regardless of the simulation. It is possible to efficiently grasp a certain PCS model.

In addition, the dropout area for each PCS model obtained by the method according to this 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 when frequency fluctuation occurs can be obtained. It can also be used for simple and high-speed estimation.

[effect]
As described above, in the calculation device 10 according to the present embodiment, it is assumed that the frequency of the power changes from a predetermined initial value f ₀ at a constant frequency change rate, and the frequency of the power of the most recent first period t _n . The limit value ( _RoCoF withstand capability) of the frequency change rate whose threshold is the difference between the moving average of the moving average and the moving average of the frequency of the power of the past second period _tp before the predetermined elapsed period tr is calculated. The calculation device 10 outputs information based on the calculated limit value. As a result, the user can acquire the limit value of the frequency change rate at which the PCS does not drop out from the calculation device 10 without constructing the model of the PCS and performing the simulation. As a result, the user can easily estimate whether the PCS is dropped from the limit value.

Further, in the calculation device 10 according to the present embodiment, the moving average of the frequency of the power of the first period t _n is set as the frequency of the midpoint of the first period t _n , and the frequency of the power of the second period t _p is used. The limit value is calculated by using the moving average as the frequency of the midpoint of the second period _tp . As a result, the calculation device 10 can simplify the calculation for obtaining the moving average and can easily calculate the limit value.

Further, the calculation device 10 according to the present embodiment has the above-mentioned (5-2) from the initial value f ₀ , the first period t _n , the elapsed period _tr , the second period t _p , and the threshold value ΔT _t . The limit value (RoCoF withstand capacity) is calculated by the formula. As a result, the calculation device 10 can calculate the limit value without performing the simulation in which the PCS model is constructed.

Further, when the detection method of the independent operation detection function is the voltage phase jump detection method, the calculation device 10 according to the present embodiment uses the formula (2-1) from the threshold value Δθ _t of the voltage phase jump detection method. When the threshold value ΔT _t is calculated and the detection method of the isolated operation 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 equation (2-2). Calculate ΔT _t . As a result, the calculation device 10 can calculate the limit value of the frequency change rate at which the PCS does not fall off by the same method for the voltage phase jump detection method and the frequency change rate detection method.

Further, the calculation device 10 according to the present embodiment drops out with respect to a multiple of the frequency change rate with respect to the limit value based on the calculated limit value ( _RoCoF withstand capacity), the second period tp and the elapsed period tr _. Assuming that the detection period required for detection is inversely proportional to the period _{t p} + tr, the frequency change rate and the conditions of the detection period, which are the boundaries at which dropout occurs, are calculated. The calculation device 10 outputs information based on the calculated conditions. Thereby, the calculation device 10 can provide the conditions of the frequency change rate and the detection period, which are the boundaries at which 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 conditions. As a result, the user can grasp the frequency change rate and the detection period, which are the boundaries where the dropout occurs, from the displayed graph.

By the way, although the embodiment regarding the disclosed apparatus has been described so far, the disclosed technique may be implemented in various different forms other than the above-described embodiment. Therefore, another embodiment included in the present invention will be described below.

For example, in the above embodiment, the case where the input of various set values used for calculating the RoCoF withstand capability is accepted from the operation screen has been described, but the disclosed device is not limited to this. For example, a part or all of various set values may be stored as data, and a part or all of various set values may be read from the data to calculate the RoCoF withstand capacity. For example, the calculation device 10 uses data that stores the set values of the initial value f ₀ of the power frequency, the first period t _n , the second period _{t p} , the elapsed period tr, and the threshold value ΔT _t . The RoCoF withstand capacity may be calculated.

Further, in the above embodiment, the case where the item (df / dt) ² is excluded in the above equation (5-1) has been described, but the disclosed apparatus is not limited to this. For example, the RoCoF withstand capacity may be calculated from the formula including the term (df / dt) ² . For example, when a, b, and c are represented as shown in (7-2)-(7-4) below, the frequency change rate is changed from the above equation (4) to the following equation (7-1). The equation for df / dt is obtained. The boundary of the inequality in equation (7-1)) corresponds to the RoCoF withstand capacity. As a result, the RoCoF withstand capacity can be calculated more accurately.

Further, each component of each of the illustrated devices is a functional concept, and does not necessarily have to be physically configured as shown in the figure. That is, the specific state of distribution / integration of each device is not limited to the one shown in the figure, and all or part of the distribution / integration is functionally or physically distributed / physically in any unit according to various loads and usage conditions. Can be integrated and configured. For example, each processing unit of the reception unit 40, the first calculation unit 41, the second calculation unit 42, and the output unit 43 may be integrated as appropriate. Further, the processing of each processing unit may be appropriately separated into the processing of a plurality of processing units. Further, each processing function performed in 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]
Further, the various processes described in the above-described embodiment can also be realized by executing a program prepared in advance on a computer system such as a personal computer or a workstation. Therefore, in the following, an example of a computer system that executes a program having the same functions as those in the above embodiment will be described. FIG. 14 is a diagram showing a computer that executes a calculation program.

As shown in FIG. 14, the computer 300 has a CPU (Central Processing Unit) 310, an HDD (Hard Disk Drive) 320, and a RAM (Random Access Memory) 340. Each of these 300 to 340 parts is connected via the bus 400.

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

Further, the HDD 320 stores various information. For example, the HDD 320 stores various data used for calculating the RoCoF withstand capacity.

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

The above-mentioned calculation program 320a does not necessarily have 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 in the computer 300. Then, the computer 300 may read the program from these and execute the program.

Further, the program is stored in an "other 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 the program from these and execute the program.

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 frequency of power changes from a predetermined initial value at a constant frequency change rate, the moving average of the frequency of power in the most recent first period and the frequency of power in the past second period before a predetermined elapsed period. Calculate the limit value of the frequency change rate whose threshold is the difference from the moving average of
A frequency change rate tolerance calculation program characterized in that a computer executes a process of outputting information based on the calculated limit value. In the process of calculating the limit value, the moving average of the frequency of the power in the first period is set as the frequency of the midpoint of the first period, and the moving average of the frequency of the power in the second period is set as the second. The frequency change rate tolerance calculation program according to claim 1, wherein the limit value is calculated as the frequency at the midpoint of the period. In the process of calculating the limit value, the initial value is f ₀ , the first period is t _n , the elapsed period is _tr , the second period is t _p , and the threshold value is set. The frequency change rate tolerance calculation program according to claim 1, wherein when ΔT _t is set, the limit value is calculated from the equation (1).

When the threshold value is ΔT _t and the detection method of the isolated operation detection function is the voltage phase jump detection method, the threshold value Δθ t of the voltage phase jump detection method is used from the threshold value Δθ _t to the above equation (2-1). When the threshold value ΔT _t is calculated and the detection method of the isolated operation detection function is the frequency change rate detection method, the above threshold is used from the threshold value Δf _t of the frequency change rate detection method using equation (2-2). The frequency change rate tolerance calculation program according to any one of claims 1 to 3, wherein the value ΔT _t is calculated.

Based on the calculated limit value, the second period, and the elapsed period, the detection period required for detecting the dropout with respect to a multiple of the frequency change rate with respect to the limit value is the second period and the elapsed period. Assuming that it is inversely proportional to the addition period obtained by adding and, the computer is further executed to calculate the frequency change rate that is the boundary where the dropout occurs and the condition of the detection period.
The frequency change rate tolerance calculation program according to any one of claims 1 to 4, wherein the output process outputs information based on the calculated conditions. The frequency change rate tolerance calculation program according to claim 5, wherein the output process displays the relationship between the frequency change rate and the detection period in a graph based on the above conditions. Assuming that the frequency of power changes from a predetermined initial value at a constant frequency change rate, the moving average of the frequency of power in the most recent first period and the frequency of power in the past second period before a predetermined elapsed period. Calculate the limit value of the frequency change rate whose threshold is the difference from the moving average of
A method for calculating a frequency change rate tolerance, characterized in that a computer executes a process of outputting information based on the calculated limit value. Assuming that the frequency of power changes from a predetermined initial value at a constant frequency change rate, the moving average of the frequency of power in the most recent first period and the frequency of power in the past second period before a predetermined elapsed period. A calculation unit that calculates the limit value of the frequency change rate whose threshold is the difference from the moving average of
An output unit that outputs information based on the limit value calculated by the calculation unit, and an output unit.
A device for calculating the withstand frequency change rate, which is characterized by having.

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