REVERSE FLOW POWER CONTROL DEVICE AND REVERSE FLOW POWER CONTROL METHOD

According to an embodiment, a reverse flow power control device includes: an input unit that accepts actual values of output power of the power conditioner, load power with respect to the load device, and reception power, and a minimum reception power value; a storage unit; and a calculator having an output controller that calculates an output command calculation value, a load controller that calculates a load command calculation value, and a command value re-calculator that calculates, by using the respective actual values, the output command calculation value, the load command calculation value, and the minimum reception power value, an output command value with respect to the power conditioner, in order to prevent a reception power value from the power system from becoming less than the minimum reception power value.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-099728 filed on Jun. 21, 2022, the entire content of which is incorporated herein by reference.

FIELD

Embodiments of the present invention relate to a reverse flow power control device and a reverse flow power control method.

BACKGROUND

Renewable energy power plants such as large-scale photovoltaic power plant and wind power plant sell all output power to a commercial power system (referred to as a power system, hereinafter) to obtain an income. Therefore, a load in a renewable energy power plant is only power of auxiliary machine such as an air conditioner, and thus the plant does not receive power from the power system except for a time zone in which there is no output power almost at all.

In recent years, attention is focused on production of hydrogen with no CO2release by using renewable energy, and a plant is being constructed in which a large-scale hydrogen producing device is provided together with a renewable energy power generator. Such a plant has a purpose of utilizing renewable energy as self-consumption, and thus it sometimes does not conclude a contract regarding a reverse flow (power selling) to the power system. In this case, the reverse flow to the power system is prevented by constantly receiving certain power from the power system.

On the other hand, there is a method of varying a load in a plant in accordance with renewable energy. In this case, it can be considered that a control delay occurs due to a control period or a communication method, resulting in that the reverse flow occurs instantaneously. When an unintended reverse flow is made to occur, it exerts an influence on the power system, and in the worst case, occurrence of power outage or the like can also be worried.

Also in a similar plant, when a required amount of hydrogen is small, there can be considered a case where a reverse flow of a surplus of renewable energy to the power system is caused, to thereby obtain a power selling income. However, when the reverse flow to the power system is caused, there is a need to respond to an output control command requested by a general power transmission and distribution operator. When the request is issued, there is a need to make reverse flow power to be equal to or less than the output control command, but if a load in a plant is varied in accordance with the renewable energy, reverse flow power exceeding the output control command may occur instantaneously due to a control delay, which may cause a financial penalty, and if violations occur many times, the power system side may limit the reverse flow.

Hereinbelow, power to be purchased from the power system will be referred to as reception power, and power of renewable energy to be sold to the power system will be referred to as reverse flow power.

In a case where the reverse flow is likely to be actually occurred, it is possible to deal with it by using a protection function to stop power generation of renewable energy. However, if the power generation is once stopped, it may take time until the power generation is restarted, due to a confirmation operation and the like for restoration, and during the time period, it is not possible to utilize output power of renewable energy.

For this reason, an operation of causing no reverse flow while achieving a predetermined object by not a protection function but a control function, is required. Further, even if the reverse flow is allowed, when a request of output control command is issued by a general power transmission and distribution operator, an operation of suppressing reverse flow power to equal to or less than the output control command is required.

DETAILED DESCRIPTION

A problem to be solved by the present invention is to prevent deviation from a condition regarding reverse flow power.

According to an aspect of the present invention, there is provided a reverse flow power control device that prevents occurrence of reverse flow power from a plant having a renewable energy power generating device, a power conditioner capable of adjusting output power of the renewable energy power generating device, and a load device, and connected to an external power system, to the power system, the reverse flow power control device comprising: an input unit that accepts actual values of the output power, load power supplied to the load device, and reception power received by the plant from the power system, and information including a minimum reception power value being a minimum value of the reception power; a storage unit that stores the information accepted by the input unit; a calculator that performs a calculation of command values of the output power and the load power based on the information and the respective actual values stored in the storage unit; and an output unit that outputs the command values to the load device and the power conditioner, wherein the calculator includes: an output controller that calculates an output command calculation value; a load controller that calculates a load command calculation value; a command value re-calculator that calculates, by using the respective actual values, the output command calculation value, the load command calculation value, and the minimum reception power value, an output command value with respect to the power conditioner, in order to prevent a reception power value being a value of the reception power from becoming less than the minimum reception power value; and a calculation interval adjustment part that sets a calculation interval of generating a plurality of calculation steps, regarding a dead time in the renewable energy power generating device, the power conditioner, and the load device; wherein the command value re-calculator calculates a change in the reception power value in an interval up to an end of the plurality of calculation steps in which a command value is reflected by the dead time, and calculates the output command value that prevents the reception power value from becoming less than the minimum reception power value.

Hereinafter, a reverse flow power control device and a reverse flow power control method according to an embodiment of the present invention will be described while referring to the drawings. Here, mutually the same or similar parts will be denoted by common reference signs, and an overlapped explanation will be omitted.

First Embodiment

FIG.1is a block diagram illustrating a relationship between a reverse flow power control device100according to a first embodiment and a plant1targeted by the reverse flow power control device100.

The plant1targeted by the reverse flow power control device100has a renewable energy power generating device (“PV”)10, a power conditioner (“PCS”)20, and a load device30.

The PV10is a device that converts natural energy into electric power, which is a photovoltaic power generating device, for example, but the PV10is not limited to this.

The PCS20makes direct-current power generated in the PV10to be input therein to output alternating-current power, and adjusts a level of the alternating-current power to be output to a predetermined value of equal to or less than an input power level.

The load device30is a device that consumes power, which is a hydrogen producing facility, for example, but the load device30is not limited to this. The load device30has a local controller31. The local controller31controls states of respective loads in the load device30according to an external load power command, so as to make power to be consumed by the load device30, namely, load power match a load power command value.

An in-plant busbar3is provided in the plant1, and the PCS20and the load device30are connected to the in-plant busbar3via connection lines4, respectively. Further, the in-plant busbar3is connected to an external power system2via the connection line4. Each connection line4is provided with a power meter50. Specifically, an output power meter51is provided to the connection line4between the in-plant busbar3and the PCS20, a load power meter52is provided to the connection line4between the in-plant busbar3and the load device30, and a transaction power meter53is provided to the connection line4between the in-plant busbar3and the power system2, by which a flow of power can be measured and monitored.

The reverse flow power control device100accepts outputs of the power meters50of the plant1, namely, outputs from the output power meter51, the load power meter52, and the transaction power meter53, respectively, as an output power actual value51a, a load power actual value52a, and a transaction power actual value53a, and outputs a PCS output command value PCSset and a load command value Lset to the PCS20and the load device30, respectively, of the plant1.

FIG.2is a block diagram illustrating a configuration of the reverse flow power control device100according to the first embodiment.

The reverse flow power control device100has an input unit110, a calculator120, a storage unit130, and an output unit140. The reverse flow power control device100may also be a combination of individual devices, which is a computer system, for example.

The calculator120has a control calculator121, a command value re-calculator122, and a change rate limiter123.

The control calculator121performs a control calculation by making the planned values of the output power and the load power, and the output power actual value51aand the load power actual value52aaccepted by the input unit110, to be inputted therein, thereby calculating a provisional PCS output command value and a provisional load command value. The control calculator121has a first subtractor121aand a first control circuit121brelated to the load command value, and a second subtractor121cand a second control circuit121drelated to the output command value. Note that although the present embodiment describes a case, as an example, in which the control calculator121performs PID control, but another control method may also be employed.

The command value re-calculator122performs re-calculation based on a result of the control calculation performed by the control calculator121, to thereby calculate the PCS output command value PCSset. Details of the calculator120will be described later while referring toFIG.3.

The change rate limiter123increases the output of the command value re-calculator122to the PCS20not rapidly but at a certain inclination, to thereby stabilize the control.

The storage unit130has a planned value storage131, a control parameter storage132, a minimum reception power storage133, an actual value storage134, a command value calculation result storage135, and a re-calculation result storage136.

The planned value storage131stores and houses the planned values of the load power and the output power read by the input unit110. Here, the planned value read by the input unit110is a time-series value regarding a time period during which the reverse flow power control device100performs the control. However, it is also possible to design such that the input unit110sequentially reads planned values regarding a predetermined time width, and in response to this, the planned value storage131sequentially houses and stores the planned values.

The control parameter storage132houses and stores a load control parameter PLand an output control parameter PPbeing control parameters read by the input unit110. Here, the control parameters are, in a case of PID control, for example, a gain, an integral time, and a derivative time.

The minimum reception power storage133houses and stores the minimum reception power read by the input unit110.

The actual value storage134houses and stores the outputs of the power meters50(actual values) read by the input unit110, namely, the output power actual value51a, the load power actual value52a, and the transaction power actual value53a. These actual values to be stored may be only the values read by the input unit110right immediately before the calculation, but values obtained by a given plurality of times of sampling may be housed in chronological order.

The command value calculation result storage135stores the calculation result of the control calculator121. The calculation result to be stored may be only the latest calculation result obtained by the control calculator121, but the results of a plurality of times of calculation up to the last calculation may be housed in chronological order.

The re-calculation result storage136stores the calculation result of the command value re-calculator122. The calculation result to be stored may be only the latest calculation result obtained by the command value re-calculator122, but the results of a plurality of times of calculation up to the last calculation may be housed in chronological order.

The output unit140outputs a load command calculation value Lcal (t) being a calculation result of the control calculator121to the load device30as a load command value Lset (t), and outputs a PCS output command value PCSset (t) being a calculation result of the command value re-calculator122to the PCS20.

FIG.3is a control block diagram illustrating contents of processing performed by the reverse flow power control device100according to the first embodiment.

When broadly classified, the processing includes a part related to a command with respect to the load device30, and a part related to a command with respect to the PCS20.

The part related to the command with respect to the load device30is as follows.

The input unit110accepts a load planned value Plan-L being a planned value of the load power, and L (t) being the load power actual value52afrom the load power meter52. Here, the value of the load planned value Plan-L is stored in the planned value storage131, and used as a reference value Lref (t) of the load power at each time point. A load controller121hof the control calculator121calculates, based on these signals, the load command calculation value Lcal (t) for giving a load command to the load device30.

Here, the load controller121hhas the first subtractor121aand the first control circuit121b. The first subtractor121asubtracts the load power actual value L (t) from the load power desired value Lref (t), to thereby output a deviation signal eL(t). The first control circuit121bperforms a control calculation based on the deviation signal eL(t), and calculates the load command calculation value Lcal (t) by the following equation (1).

Here, FLmeans that Lcal (t) is a function of Lref (t), L (t), and PL.

For example, in a case where the control by the load controller121his the PID control, Lcal (t) can be obtained by the following equation (2).

The calculated value of the load command calculation value Lcal (t) is output from the output unit140as a load command signal Lset (t) with respect to the local controller31of the load device30.

The part related to the command with respect to the PCS20is as follows.

The input unit110accepts a planned value Plan-P of the output power, and R being the output power actual value51afrom the output power meter51. Here, the value of the planned value Plan-P is stored in the planned value storage131, and used as a reference value PCSref (t) of the output power at each time point. An output controller121pof the control calculator121calculates, based on these signals, the output command calculation value PCScal with respect to the PCS20.

Here, the output controller121phas a second subtractor121cand a second control circuit121d. The second subtractor121csubtracts the output power actual value PCS (t) from the output power desired value PCSref (t), to thereby output a deviation signal ep(t). The second control circuit121cperforms a control calculation based on the deviation signal ep(t), and calculates the output command calculation value PCScal (t) by the following equation (3).

Here, FPCSmeans that PCScal (t) is a function of PCSref (t), PCS (t), and PP.

For example, in a case where the control by the output controller121pis the PID control, PCScal (t) can be obtained by the following equation (4).

Here, KPP, KIP, and KDPare the output control parameters Ppread by the input unit110and stored in the control parameter storage132.

The command value re-calculator122calculates, based on the output command calculation value PCScal (t) calculated by the output controller121p, the load command calculation value Lcal (t) calculated by the load controller121h, and a minimum reception power value Rmin housed in the minimum reception power storage133of the storage unit130, the output command value PCSset (t) in order to prevent a reception power value R (t) from the system from becoming less than the minimum reception power value Rmin. Here, the reception power value R (t) is a value obtained by subtracting the output power value PCS (t) from a load power value L (t). The contents of calculation in the command value re-calculator122will be described later in detail while citingFIG.4.

The output command value PCSset (t) calculated by the command value re-calculator122is limited by the change rate limiter123so that the change rate, namely, a rate of change of the value becomes a predetermined value or less, and then output as the output command value PCSset (t) to the PCS20from the output unit140.

FIG.4is a conceptual graph for explaining details of re-calculation of the output command value in a reverse flow power control method according to the first embodiment. A horizontal axis indicates a time, and a vertical axis indicates each electric power (kW). Δt is a time width of a control step, namely, a control period.FIG.4illustrates a case where a calculation period, namely, a calculation step time width matches the control period Δt. Specifically, actual values of respective powers are obtained at a time t, and after performing the calculation, a command value is output at the next control step time (t+Δt). Details will be described hereinbelow.

First, regarding the load power, the load command value Lset (t) is calculated by the load controller121h. As described above, upon receiving the load command value Lset (t), the local controller31of the load device30performs control so that a load power value L (t+Δt) used by the load device30matches the value of the load command value Lset (t). Therefore, at the next control step time (t+Δt), the value of the load power value L (t+Δt) can be approximated to the value of the load command value Lset (t). Here, a rising width of the load power after Δt (L (t+Δt)−L (t)) will be described as ΔL.

In the same way, regarding the output power, the output command calculation value PCScal (t) is calculated by the output controller121p. As described above, when the PCS20receives the output command of this value, it performs control so that an output power value PCS (t+Δt) matches this value PCScal (t). Therefore, in this case, at the next control step time (t+Δt), the value of the output power value PCS (t+Δt) can be approximated to this value PCScal (t). Here, a rising width of the output power after Δt in this case (PCS (t+Δt)−PCS (t)) will be described as APCS.

Here, the command value re-calculator122calculates, based on the command values capable of being approximated as respective prediction values at the next control step time (t+Δt), namely, the load command value Lset (t) and the output command calculation value PCScal (t), and the reception power value R (t), the PCS output command value PCSset (t) being an output command value that prevents the prediction value R (t) of the reception power from becoming less than the minimum reception power value Rmin.

Concretely, the PCS output command value PCSset (t) is calculated by the following equation (5).

Here, the equation (5) can be represented as the following equation (6).

FIG.5is a flow chart illustrating a procedure of the reverse flow power control method according to the first embodiment. Hereinafter, the procedure of the reverse flow power control method will be described while citingFIG.5.

First, reading of parameters is performed (step S10). Concretely, the input unit110reads the load control parameter PL, and the control parameter storage132stores the parameter (step S11). Further, the input unit110reads the output control parameter Pp, and the control parameter storage132stores the parameter (step S12). Further, the input unit110reads the minimum reception power value Rmin, and the minimum reception power storage133stores the value (step S13).

Next, the other external data is read (step S20). Concretely, the input unit110reads the load planned value Plan-L and the output planned value Plan-P, and the planned value storage131stores the values (step S21). Further, the input unit110accepts the load power actual value L (t) and the output power actual value PCS (t) as the power actual values, and the actual value storage134stores the values (step S22). Note that the reception power value R (t) obtained by subtracting the output power actual value PCS (t) from the load power actual value L (t) is also housed in the actual value storage134.

Next, the control calculator121of the calculator120calculates the command values (step S30). Concretely, the load controller121hof the control calculator121calculates the load command calculation value Lcal (t) (step S31). The obtained load command calculation value Lcal (t) is output as the load command value Lset (t) to the local controller31of the load device30, as will be described later (step S60).

Further, the output controller121pof the control calculator121calculates the output command value calculation value PCScal (t) (step S32). These calculated load power command value Lset (t) and output command value calculation value PCScal (t), and the reception power value R (t) obtained by subtracting the output command value calculation value PCScal (t) from the load command calculation value Lcal (t), are housed and stored in the command value calculation result storage135.

Next, the command value re-calculator122performs re-calculation by using the respective power actual values housed in the actual value storage134and the calculation result housed in the command value calculation result storage135, to thereby calculate the PCS output command value PCSset (t) (step S50). This result is output as the output command value PCSset (t) to the PCS20from the output unit140via the change rate limiter123. Further, the load command calculation value Lcal (t) obtained in step S30is output as the load command value Lset (t) to the local controller31of the load device30(step S60).

Although the calculator120described above performs the calculation regarding absolute values of the load power and the output power, namely, the values of the load power and the output power themselves, the calculation is not limited to this. For example, it is possible that change amounts from the actual values (ΔL, ΔPCS, and the like) are calculated, instead of the load power command value Lset (t), the output command value calculation value PCScal (t), and the output command value PCSset (t), and absolute values of the load power command value and the output power command value are calculated in the output unit140. The calculation by the change amounts, not the absolute values of the command calculation value and the command value as described above can further simplify the calculation.

Note that the above-described embodiment describes a case, as an example, in which the output command value PCSset (t) is calculated by using the min function based on one minimum reception power value Rmin, but the embodiment is not limited to this. For example, it is possible that a plurality of threshold values as a substitute for the minimum reception power are read by the input unit110and then housed in the minimum reception power storage133, change amounts up to the respective threshold values are calculated, and the command value re-calculator122calculates an average value, a median value, or a maximum value of the change amounts.

As described above, according to the reverse flow power control device100in the present embodiment, in each control step, the control calculation result is not output as it is to the PCS20, but the re-calculation is performed in order to prevent the reception power value R (t) from becoming less than the minimum reception power value Rmin. As a result of this, it is possible to prevent the reverse flow from the plant1to the power system2.

Second Embodiment

FIG.6is a block diagram illustrating a configuration of a reverse flow power control device100aaccording to a second embodiment.

The present embodiment is a modification of the first embodiment, and relates to a case where there exists a dead time in a response of a part or all of the renewable energy power generating device (PV)10, the power conditioner (PCS)20, and the load device30.

In the present embodiment, a calculator120afurther has a calculation interval adjustment part124, and a storage unit130afurther has a dead time storage137.

The input unit110accepts dead time DLi information as an external input, and the dead time storage137stores this information. Further, the actual value storage134stores respective pieces of power actual value data of at least (M+1) times of calculation to be described later. Here, when there exists the dead time DLi information (i=1 to 3) of each of the PV10, the PCS20, and the load device30, a maximum value thereof is set as the dead time DL.

The calculation interval adjustment part124calculates, based on the dead time DL and a normal calculation time interval Δtn, a calculation interval Δt by using the following equation (7) and equation (8).

Here, ROUND (DL/Δtn, 0) is for rounding up digits after a decimal point of a numeric value of (DL/Δtn) to form an integer.

FIG.7is a conceptual graph for explaining details of re-calculation of an output command value in a reverse flow power control method according to the second embodiment.

FIG.7illustrates a case, as an example, in which a calculation of five steps is performed regarding the dead time DL, namely, the above-described (M+1) is 5.

The second embodiment is different from the first embodiment in that it performs a calculation of the load command calculation value Lcal by the load controller121h, a calculation of the output command calculation value PCScal by the output controller121p, and a calculation of the reception power value R, at the initial four steps, as represented by the following equation (9) to equation (12), and then performs a calculation of output command in the command value re-calculator122after the lapse of dead time, namely, at the fifth step, as represented by the following equation (13).

Note that when the above is generalized, in a case where the dead time includes T steps, future reception power is calculated by the following equation (14), and the PCS output command value PCSset (t) is calculated by the equation (15).

Note that although the above-described embodiment describes a case, as an example, in which the dead time in the load device30and the dead time in the PCS20are the same, but even in a case where the values of the dead time are mutually different, it is possible to perform processing in a similar manner.

However, when the load device30and the PCS20have mutually different dead time, it is desirable that the dead time in the PCS20is shorter than that in the load device30.

As described above, in the present embodiment, even if the dead time is large, it is possible to prevent the reception power value Rm (t) from becoming less than the minimum reception power value Rmin.

Third Embodiment

FIG.8is a block diagram illustrating a configuration of a reverse flow power control device100baccording to a third embodiment.

The present embodiment is a modification of the first embodiment, and takes a response characteristic of each of the renewable energy power generating device (PV)10, the power conditioner (PCS)20, and the load device30into consideration.

In the present embodiment, the input unit110accepts characteristic models obtained by modeling these response characteristics, as an external input. A storage unit130bfurther has a characteristic model storage138that stores these characteristic models. Further, a calculator120bfurther has a prediction value calculator125that calculates prediction values of response by using these characteristic models. The prediction value calculator125has an output prediction value calculator125aand a load prediction value calculator125b.

Each characteristic model may be a single characteristic table or a combination of characteristic tables. Alternatively, a calculation of an output prediction value PCSpd (t+Δt) by the output prediction value calculator125aand a calculation of a load prediction value Lpd (t+Δt) by the load prediction value calculator125bmay be performed by the form of functions as represented by the following equation (16) and equation (17), respectively.

Here, qPand qLare a set of constants related to respective characteristics (characteristic constants). For example, they are a time constant and a gain in a case of first-order lag or second-order lag.

Note that the calculation of the output prediction value PCSpd (t+Δt) by the output prediction value calculator125aand the calculation of the load prediction value Lpd (t+Δt) by the load prediction value calculator125bare not limited to be performed as described above and may be performed linearly or nonlinearly as long as it is possible to predict future power with respect to a command value for each device, and it is possible to use, for example, a prediction method of deep learning such as a neural network or a random forest using a tree structure.

FIG.9is a control block diagram illustrating a configuration and operations of the reverse flow power control device100baccording to the third embodiment.

Regarding a part related to a command with respect to the load device30, the load controller121hof the control calculator121calculates the load command calculation value Lcal (t), and the output unit140outputs this value as the load command value Lset (t), to thereby enable operations similar to those of the first embodiment.

On the other hand, regarding a part related to a command with respect to the PCS20, a part different from that of the first embodiment will be described below.

Firstly, the load prediction value calculator125bcalculates the load prediction value Lpd (t+Δt) by using the load command calculation value Lcal (t) calculated by the load controller121h.

Secondly, the output prediction value calculator125acalculates the output prediction value PCSpd (t+Δt) by using the output command calculation value PCScal (t) calculated by the output controller121p.

Thirdly, the command value re-calculator122calculates, based on respective prediction values at the next control step time (t+Δt), namely, the load prediction value Lpd (t+Δt) and the output prediction value PCSpd (t+Δt), and the reception power value R (t), the PCS output command value PCSset (t) being an output command value that prevents the prediction value R (t+Δt) of the reception power from becoming less than the minimum reception power value Rmin.

Concretely, the PCS output command value PCSset (t) is calculated based on the respective prediction values by using the following equation (18), instead of the equation (5) in the first embodiment.

Here, if the same method of thinking as the first embodiment is tried to be applied strictly, there is a need to use an inverse function of PCSpd (t) and PCS (t) for the output command value PCSset (t) that prevents the prediction value R (t+Δt) of the reception power from becoming less than the minimum reception power value Rmin, but the processing becomes complicated, and further, realistically speaking, it can be considered that the control response and the response characteristic related to the PV10, the PCS20, and the load device30can be ignored when seen from the reverse flow power control device100side. In such a case, by correcting an amount of ΔR (refer toFIG.4) from the output prediction value PCSpd (t) as in the following equation (19), it is possible to obtain the PCS output command value PCSset (t).

FIG.10is a flow chart illustrating a procedure of a reverse flow power control method according to the third embodiment. The procedure up to step S30is similar to that of the first embodiment. Hereinbelow, only a part different from that of the first embodiment will be described.

The present embodiment further has a prediction value calculation step (step S40). Specifically, the load prediction value calculator125bperforms a load power prediction value calculation to calculate a load prediction value Lpd (t+Δt) (step S41), and the output prediction value calculator125aperforms an output power prediction value calculation to calculate an output prediction value PCSpd (t+Δt) (step S42).

Further, in an output command value re-calculation step S50ain the present embodiment, the PCS output command value PCSset (t) is calculated based on the respective prediction values by using the equation (19), instead of the equation (5) in the first embodiment.

As described above, according to the present embodiment, it is possible to obtain an effect similar to that of the first embodiment. Further, by predicting future power by using the models of the respective devices, an influence due to the characteristics of the respective devices can be considered, which enables to further securely reduce the possibility that the reception power becomes less than the minimum reception power.

Fourth Embodiment

FIG.11is a block diagram illustrating a relationship between a reverse flow power control device100caccording to a fourth embodiment and a plant1ctargeted by the reverse flow power control device100c.

The present embodiment is a modification of the first embodiment, and the plant1cfurther has a storage battery40and a charge/discharge power meter54.

FIG.12is a block diagram illustrating a configuration of the reverse flow power control device100caccording to the fourth embodiment. The reverse flow power control device100cfurther has a storage battery controller121q. Further, a command value re-calculator122cis provided instead of the command value re-calculator122in the first embodiment, and a re-calculation target is not the output command value with respect to the PCS20in the first embodiment but a charge/discharge command value with respect to the storage battery40. A part other than the above is similar to that of the first embodiment. Hereinafter, a part different from that of the first embodiment will be mainly described, and an explanation of a part similar to that of the first embodiment will be omitted.

FIG.13is a conceptual graph for explaining details of re-calculation of an output command value in a reverse flow power control method according to the fourth embodiment.

The output command calculation value PCScal (t) calculated by the output controller121pis output as the output command value PCSset (t) from the output unit140to the PCS20.

The storage battery controller121qcalculates a charge/discharge command calculation value BATcal (t) of the storage battery40through a control calculation. Here, a change amount of the charge/discharge command calculation value BATcal (t) with respect to a charge/discharge actual value BAT (t) of the storage battery40is set to ABAT. Here, if the change is in the case of charge, ABAT is positive, and if the change is in the case of discharge, ABAT is negative.

The command value re-calculator122ccalculates, based on the command values capable of being approximated as respective prediction values at the next control step time (t+Δt), namely, the load command calculation value Lcal (t), the output command calculation value PCScal (t), and the charge/discharge command calculation value BATcal (t), and the respective actual values, a charge/discharge command value BATset (t) being a charge/discharge command value that prevents the prediction value R (t) of the reception power from becoming less than the minimum reception power value Rmin.

Concretely, the charge/discharge command value BATset (t) is calculated by the following equation (20).

Charge/discharge command value

Here, the equation (20) can be represented as the following equation (21).

As described above, in the plant1ctargeted by the reverse flow power control device100caccording to the present embodiment, the storage battery40is provided, so that by charging the power generated by the PV10in the storage battery40without being suppressed by the PCS20, the renewable energy can be used maximally.

Regarding such a plant1c, the reverse flow power control device100caccording to the present embodiment outputs the charge/discharge command value BATset (t) after re-calculating the command value with respect to the storage battery40while setting the minimum reception power value Rmin as a condition. As a result of this, it is possible to avoid a situation in which the reception power value R (t) becomes less than the minimum reception power value Rmin or a reverse flow occurs due to a control delay.

Fifth Embodiment

FIG.14is a block diagram illustrating a relationship between a reverse flow power control device100daccording to a fifth embodiment and a plant1targeted by the reverse flow power control device100d.

The present embodiment is a modification of the first embodiment, and is an embodiment in a case where reverse flow power from the plant1to the power system2is allowed under a certain condition. Accordingly, when the reverse flow power is allowed, a reverse flow allowance signal2ais sent from the power system2to the reverse flow power control device100d.

FIG.15is a block diagram illustrating a configuration of the reverse flow power control device100daccording to the fifth embodiment.

The input unit110accepts the reverse flow allowance signal2asent from the power system2. Here, the reverse flow allowance signal2aincludes an allowed time zone ΔTp during which the reverse flow is allowed, and a maximum reverse flow power value Smax being an upper limit value of the reverse flow at that time.

A storage unit130dfurther has a maximum reverse flow power storage139that houses and stores the allowed time zone ΔTp and the maximum reverse flow power value Smax accepted by the input unit110.

A calculator120dfurther has a control condition determination part126. The control condition determination part126designates either of two control states (a first control state and a second control state), based on the allowed time zone ΔTp and the maximum reverse flow power value Smax housed in the storage unit130d.

A command value re-calculator122dperforms processing according to the respective control states.

Firstly, the first control state corresponds to a case where the reverse flow is not allowed, in the same manner as in the first embodiment. Specifically, the command value re-calculator122dcalculates, based on the output command calculation value PCScal (t) calculated by the output controller121p, the load command calculation value Lcal (t) calculated by the load controller121h, and the minimum reception power value Rmin housed in the minimum reception power storage133of the storage unit130, the output command value PCSet (t) in order to prevent the reception power value R (t) from the system from becoming less than the minimum reception power value Rmin.

The second control state corresponds to a case where the reverse flow is allowed in the allowed time zone ΔTp based on the reverse flow allowance signal2asent from the power system2. The command value re-calculator122dcalculates, based on the output command calculation value PCScal (t) calculated by the output controller121p, the load command calculation value Lcal (t) calculated by the load controller121h, and the maximum reverse flow power value Smax housed in the maximum reverse flow power storage139of the storage unit130, the output command value PCSset (t) using the following equation (22), in order to prevent reverse flow power S (t) with respect to the system from exceeding the maximum reverse flow power value Smax.

Here, the equation (22) can be represented as the following equation (23).

Note that in the above description, the case in which the reverse flow allowance signal2aincludes the allowed time zone ΔTp during which the reverse flow is allowed, and the maximum reverse flow power value Smax being the upper limit value of the reverse flow at that time, is described as an example, but not limited to this. For example, the reverse flow allowance signal2afrom the power system2may include only the maximum reverse flow power value Smax. In this case, the control condition determination part126can designate the first control state during a period of time in which the reverse flow allowance signal2afrom the power system2is not sent, and it can designate the second control state during a period of time in which the signal is sent.

As described above, according to the present embodiment, even in a case where the reverse flow is allowed, it is possible to prevent the reverse flow power from exceeding the maximum reverse flow power value Smax due to the control delay, by re-calculating the output command value PCSset (t) with respect to the PCS20by using the maximum reverse flow power value Smax included in the reverse flow allowance signal2aacquired from the power system2.

According to the embodiments described above, it becomes possible to prevent the deviation from the condition regarding the reverse flow power.

While certain embodiments of the present invention have been described above, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. The characteristics of the respective embodiments may be combined. For example, the characteristic of the second embodiment may be combined with any characteristic of the third to fifth embodiments or with all characteristics of the third to fifth embodiments. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions, and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

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