Calculation device, calculation method, program, power storage system, power generation system, and grid

Abstract

To ensure that at the start of the next section, a power storage device has enough capacity to absorb an excess or shortage of power that will occur at the next and subsequent sections.SOLUTION: A calculation device 20 for optimizing the efficiency of energy use of a grid S1 interconnected with an electric power system 1 and equipped with a power storage device 15. A range of the final state of charge of a section to be predicted for the power storage device 15 is determined based on a forecast of the supply and demand of power in the next section and thereafter. In the optimization calculation of the section to be predicted, it evaluates whether the final state of charge of the section matches the range.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to a technique for optimizing the efficiency of grid energy utilization. [Background technology]

[0002] From the viewpoint of reducing dependency on fossil fuels and environmental issues, the introduction of distributed power sources such as photovoltaic (PV) systems is being promoted. PV systems convert the electricity generated by solar panels from direct current to alternating current using an inverter circuit in a power control device, and output the converted electricity.

[0003] The following patent documents 1 is The present invention discloses a technology for controlling a second power conversion means in a power storage type photovoltaic power generation system so that the received power detected by the received power detection means does not fall below a predetermined power when both the generated power from the distributed power source and the power from the power storage means are output. This prevents the power from the power storage means from flowing back into the power grid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4765162 Summary of the Invention [Problem to be solved by the invention]

[0005] A grid equipped with a power storage device can absorb and make up for power surpluses and shortages by charging and discharging if the power storage device has sufficient surplus capacity. When surplus power is stored by charging, surplus capacity refers to the available capacity for charging. When a power shortage is made up for by discharging, surplus capacity refers to the available capacity for discharging.

[0006] When performing calculations to optimize the efficiency of grid energy utilization, if the charge state of the energy storage device is determined solely based on the power supply and demand forecast for the current section, there are cases in which the energy storage device is unable to secure sufficient spare capacity at the start of the next section to absorb any power surplus or shortage that occurs in the next section and beyond. [Means for solving the problem]

[0007] A calculation device that optimizes the energy utilization efficiency of a grid that is connected to a power system and has a power storage device, the calculation device determining a range of a final state of charge of the power storage device in a prediction target section based on a power supply and demand prediction for a next section and thereafter, The most efficient use of energy In the optimization calculation, Forecast target The final state of charge of the interval is evaluated to see if it meets the range.

[0008] The above aspect can be applied to a calculation method for optimizing the energy utilization efficiency of a grid that is connected to a power system and has a power storage device, and can be applied to a program for performing optimization calculations. Effect of the Invention

[0009] At the start of the next section, it is possible to ensure in the power storage device a surplus capacity for absorbing any surplus or shortage of power occurring in the next section and thereafter. [Brief description of the drawings]

[0010] [Figure 1] Microgrid Block Diagram [Diagram 2] Microgrid Block Diagram [Diagram 3] Graph showing correlation characteristics between solar radiation and generated power [Figure 4] A graph showing the trends in predicted power generation and power consumption [Diagram 5] A simplified block diagram of a microgrid [Figure 6] Graph showing the progress of the battery charge state [Figure 7] Graph showing the progress of the battery charge state [Figure 8A] A diagram showing the number of candidates for receiving power [Figure 8B] A diagram showing the number of candidates for receiving power [Figure 9] Diagram showing an example of dividing the forecast period [Figure 10] A graph showing the electricity supply and demand for each section [Figure 11] Calculation process flow chart [Figure 12] An enlarged view of a part of Figure 10 [Figure 13] Microgrid Block Diagram DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A calculation device that optimizes the energy utilization efficiency of a grid that is connected to a power system and has a power storage device, the calculation device determining a range of a final state of charge of the power storage device in a prediction target section based on a power supply and demand prediction for a next section and thereafter, The most efficient use of energy In the optimization calculation, Forecast target The final state of charge of the interval is evaluated to see if it meets the range.

[0012] In this configuration, the range of the final state of charge for a section is determined based on a forecast of power supply and demand for the next section and onward. Since the final state of charge for a section is the starting state of charge for the next section, by making the final state of charge for the section match the determined range, it is possible to ensure that the storage device has a surplus capacity to absorb any power surplus or shortage that occurs in the next section and onward at the start of the next section.

[0013] Calculating an amount of surplus power in a first period in which the supply of power exceeds the demand in the next section and thereafter based on a supply and demand forecast of power in the next section and thereafter; Forecast target The upper limit of the final state of charge of the section may be determined to be a value obtained by subtracting a value corresponding to the amount of surplus power from the upper limit of the usage range of the storage device. With this configuration, it is possible to ensure in the storage device a surplus capacity (free capacity) for charging the surplus power of the grid at the start of the next section. This makes it possible to reduce energy loss.

[0014] Calculating a minimum surplus energy amount for the first period based on a forecast of power supply and demand for the next section and thereafter; Forecast target The upper limit of the final state of charge of the section may be determined to be a value obtained by subtracting a value corresponding to the minimum amount of surplus energy from the upper limit of the usage range of the power storage device. In this configuration, it is possible to ensure in the power storage device a surplus capacity (available capacity) for charging at least the minimum amount of surplus energy at the start of the next section.

[0015] Next A power shortage amount caused by the supply of power falling short of the demand is calculated for a second period from the start of the section to the first period, and Forecast target The lower limit of the final state of charge of the section may be determined to be a value obtained by adding a value corresponding to the power deficit to the lower limit of the usage range of the storage device. In this configuration, the storage device can have a surplus capacity to discharge the power deficit of the grid at the start of the next section. Therefore, energy can be used efficiently.

[0016] Calculating a maximum energy shortage amount for the second period based on a power supply and demand forecast for the next section and thereafter; Forecast target The lower limit of the final state of charge of the section may be determined to be a value obtained by adding a value corresponding to the maximum amount of energy deficit to the lower limit of the usage range of the storage device. In this configuration, it is possible to ensure in the storage device a reserve capacity for discharging the maximum amount of energy deficit at the start of the next section.

[0017] <Embodiment 1> 1. Description of Microgrid S1 The microgrid S is a small-scale power system that is connected to the power system 1 and includes at least a distributed power source, a power storage device, and a load. The power system 1 may be that of a power company, or may be an independent power system that is based on the isolated operation output of a large power conditioner.

[0018] 1 is a block diagram of a microgrid S1. The microgrid S1 is composed of a photovoltaic power generation panel 10 which is a distributed power source, a storage battery 15 which is a power storage device, a power conditioner 20 which is a power control device, and a load L.

[0019] The power conditioner 20 includes a first converter circuit 21, a second converter circuit 23, a DC link unit 25, a bidirectional inverter circuit 31, a relay 37, a control device 50, a DC voltage detection unit 27, an output current detection unit 33, and an output voltage detection unit 35.

[0020] The solar power generation panel 10 is connected to the first converter circuit 21. The first converter circuit 21 is a DC / DC converter, and boosts and outputs the output voltage (direct current) of the solar power generation panel 10. The first converter circuit 21 may be a chopper.

[0021] The storage battery 15 is connected to the second converter circuit 23. The storage battery 15 is, for example, a secondary battery. The second converter circuit 23 is a bidirectional DC / DC converter that discharges and charges the storage battery 15. The second converter circuit 23 may be a bidirectional chopper.

[0022] The solar power generation panel 10 and the storage battery 15 are connected in parallel to a DC link unit 25 via a first converter circuit 21 and a second converter circuit 23.

[0023] The DC link unit 25 is located between the connection point 24 of the converter circuit and the bidirectional inverter circuit 31. The DC link unit 25 is provided with an electrolytic capacitor C1. The electrolytic capacitor C1 is provided to stabilize the voltage Vdc of the DC link unit 25.

[0024] The DC voltage detection unit 27 detects the voltage Vdc of the DC link unit 25. The voltage Vdc of the DC link unit 25 detected by the DC voltage detection unit 27 is input to the control device 50.

[0025] The bidirectional inverter circuit 31 is a bidirectional conversion circuit that selectively performs reverse conversion (inverter) that converts DC to AC and forward conversion (converter) that converts AC to DC. The bidirectional inverter circuit 31 is connected to the DC link unit 25, and during reverse conversion operation, converts DC power input from the DC link unit 25 into AC power and outputs it. In detail, power equivalent to the voltage increased from a reference value in the DC link unit 25 due to power generation by the solar power generation panel 10 is input to the bidirectional inverter circuit 31. Therefore, the power equivalent to the voltage increased from the reference value is converted from DC to AC and output from the bidirectional inverter circuit 31.

[0026] The storage battery 15 can store surplus power of the solar power generation panel 10 via the second converter circuit 23. When the power generated by the solar power generation panel 10 is insufficient, the storage battery 15 can discharge the power via the second converter circuit 23 to make up for the shortage of generated power.

[0027] The bidirectional inverter circuit 31 is connected via a relay 37 to a power system 1 that uses a system power supply 2 as an AC power supply.

[0028] The relay 37 is provided for interconnection with the power grid 1. By closing the relay 37, the microgrid S1 can be interconnected with the power grid 1.

[0029] The output current detector 33 detects the output current Iinv of the bidirectional inverter circuit 31. The output voltage detector 35 is located on the output side of the bidirectional inverter circuit 31 and detects the output voltage Vinv of the bidirectional inverter circuit 31.

[0030] The output current Iinv of the bidirectional inverter circuit 31 detected by the output current detection unit 33 and the output voltage Vinv of the bidirectional inverter circuit 31 detected by the output voltage detection unit 35 are input to the control device 50. The control device 50 calculates the output power (active power) Pinv of the bidirectional inverter circuit 31 based on the output current Iinv and output voltage Vinv of the bidirectional inverter circuit 31. The output power Pinv is "positive" during inverse conversion and "negative" during forward conversion.

[0031] A load L, which is a demand facility, is connected to a power line (main line) 5 that connects the bidirectional inverter circuit 31 and the power system 1 via a branch line 4. Power can be supplied to the load L from both the power conditioner 20 and the power system 1.

[0032] The power receiving point 3 is a point where power is supplied from the power system 1, and is a boundary portion between the power system 1 and the premises (microgrid S1) as shown in FIG.

[0033] The power system 1 is provided with an external measuring instrument 40 such as an external transducer as a meter for detecting power at the power receiving point 3.

[0034] The external measuring instrument 40 has a receiving current detection unit 41 and a system voltage detection unit 43. The external measuring instrument 40 is installed corresponding to the power receiving point 3, and the receiving current detection unit 41 detects the receiving current at the power receiving point 3. The system voltage detection unit 43 detects the system voltage of the power system 1.

[0035] The external measuring instrument 40 calculates the received power (active power) P based on the received current and the system voltage. RCV The received power P detected by the external measuring device 40 is calculated. RCV is input to the control device 50. RCV The external measuring instrument 40 can be used to determine the state of the power flow (hereinafter, simply referred to as the power flow). RCV It is an instrument that measures.

[0036] Receiving power P RCVIn this section, forward power flow (Figure 1: the flow of electricity from power grid 1 to microgrid S1) is considered to be "positive" and reverse power flow (Figure 2: the flow of electricity from microgrid S1 to power grid 1) is considered to be "negative."

[0037] The control device 50 has a CPU 51 and a memory 53. The memory 53 stores a program for predicting power supply and demand in the microgrid S1 and a program for executing an optimization calculation for optimizing the energy utilization efficiency of the microgrid S1. The control device 50 is an example of the "computation device" of the present invention.

[0038] The control device 50 can control switching between the forward conversion operation and the inverse conversion operation by giving a command to the bidirectional inverter circuit 31. The control device 50 can control the output of the bidirectional inverter circuit 31, that is, the output power Pinv. The output power Pinv can be controlled by adjusting the output current Iinv.

[0039] The control device 50 can control the connection / disconnection of the solar power generation panel 10 to the DC link unit 25 by turning the first converter circuit 21 on and off. The control device 50 can control the connection / disconnection of the storage battery 15 to the DC link unit 25 by turning the second converter circuit 23 on and off. The control device 50 can control switching between charging and discharging the storage battery 15 via the second converter circuit 23. The control device 50 can control the charging current and discharging current of the storage battery 15 via the second converter circuit 23.

[0040] 2. Power generation and load forecasts for microgrid S1 The control device 50 predicts the power generation [kW] of the photovoltaic power generation panel 10 and the power consumption [kW] of the load L.

[0041] Power generation P of solar panel 10 PV As shown in Figure 3, there is a correlation between the amount of solar radiation X and the generated power P PV The predicted value can be obtained from a predicted data providing center 70 via a network NW. The predicted data providing center 70 may be a providing center of the supplier of the power conditioner 20. goodThe power generated by the solar panel 10 P PV is converted to AC by the bidirectional inverter circuit 31. The conversion efficiency η is the conversion efficiency of the inverter circuit 31 when converting direct current DC to alternating current AC.

[0042] Power consumption P of load L LOAD can be predicted from past data. For example, the power consumption P LOAD By statistically processing this data, it is possible to predict the power consumption for the next day.

[0043] Power consumption P of load L LOAD is the receiving power P at receiving point 3 RCV and the output power Pinv of the bidirectional inverter circuit 31. RCV >0), the power consumption P of the load L LOAD is the output power Pinv and the receiving power P RCV The reverse power flow (P RCV <0), the power consumption P of the load L LOAD is the output power Pinv and the receiving power P RCV This is the difference.

[0044] P LOAD =Pinv+P RCV (A)

[0045] Fig. 4 is a graph showing the results of power generation prediction and load prediction of the microgrid S1. The dashed line indicates the predicted value of the power generation of the microgrid S1, and the solid line indicates the predicted value of the power consumption of the microgrid S1. In this example, the prediction period T is set to one day, and power generation prediction and load prediction are performed every hour, and the predicted value is a step-like waveform whose value changes every hour. The power generation prediction and load prediction of the microgrid S1 may be performed by the control device 50, or data predicted by another device may be obtained.

[0046] 3. Optimization calculations to optimize the energy efficiency of microgrids FIG. 5 is a simplified block diagram of microgrid S1. The control device 50 performs an optimization calculation to optimize the energy utilization efficiency of the microgrid S1. The optimization calculation is carried out based on the power generation prediction and the load prediction (FIG. 4) to obtain the received power P that minimizes the objective function F of the formula 1. RCV The target value of the received power (hereinafter, the target value of the received power P RCVref ) to find the optimal value.

[0047] Equation 1 is an objective function for evaluating the energy utilization efficiency of the microgrid S1.

number

[0048] The first and second terms of the objective function F are terms that evaluate the usage restriction period of the storage battery 15. The third and fourth terms are terms that evaluate the electricity fee for the microgrid S1.

[0049] During the usage restriction period, the charging restriction period T MAX and discharge limit period T MIN There are two periods: MAX is a period during which charging is restricted, for example, when the SOC of the storage battery 15 is at the upper limit of the usage range (when fully charged). MIN is a period during which discharging is restricted, for example, when the SOC of the storage battery 15 is at the lower limit of the usage range.

[0050] In this example, k1>k2>k3>k4, and in the evaluation of the energy utilization efficiency of the microgrid S1, the evaluation of the usage restriction period of the storage battery 15 is prioritized. It is also possible that k1=k2 and k3=k4.

[0051] Receiving power target value P RCVref When performing the calculation to optimize the power receiving target value P RCVref and the upper and lower limits of the output power [kW] of the storage battery 15 (Equation 3).

[0052]

number

number

[0053] [Table 1]

[0054] The SOC (State of Charge) is the ratio of the charge amount to the rated capacity of the storage battery 15. The SOC is an example of the "state of charge" of the storage battery 15. In order to calculate the objective function F, it is necessary to estimate the SOC of the storage battery 15. The SOC of the storage battery 15 and the received power P RCVt We explain how to simulate the estimate of

[0055] Charging limit period T at time slice t MAX and discharge limit period T MIN The calculation method will be described below. <step1> From Equation 4 and Equation 5, the provisional output power prediction value P of the storage battery 15 at the time slice t BATtmpt Calculate.

[0056]

number

number

[0057] <step2> From Equation 6 to Equation 9, the provisional predicted state of charge SOC of the storage battery 15 at the time slice t is tmp t Calculate. (a) When t=0

number

number

[0058] (b) When t ≠ 0

number

number

[0059] <step3> Determine whether there is an upper or lower limit deviation or an upper or lower limit match at the time section t, and the predicted state of charge SOC of the storage battery 15 t , the output power P of the storage battery BATt , the charging deadline period T MAX , the discharging deadline period T MIN are determined. (a) SOC tmpt When SOC ≥ SOCMAX

Number

Number

[0060] (b) SOC tmpt When SOC ≤ SOCMIN

Number

Number

[0061] (c) When SOCMIN < SOC tmpt < SOCMAX

Number

Number

[0062] Next, from Formulas 16 and 17, the initial value (when t = 0) of the predicted charge amount Wh of the storage battery 15 can be obtained. BATt is obtained.

Number

Number

[0063] Next, for each time section (t ≠ 0), the predicted charge amount Wh of the storage battery 15 is calculated using Equation 18. BATt From Equation 19, the predicted value SOC of the storage battery 15 can be calculated. t It is possible to ask for:

number

number

[0064] Predicted power received at time slice t P RCV can be calculated from Equations 20 and 21.

number

number

[0065] Peak power reception prediction value P during the prediction period T PEAK can be calculated from Equation 22.

number

[0066] [Table 2]

[0067] From Equations 4 to 19, the predicted power generation value P PVt ×η and predicted power consumption value P of load L LOADt For the receiving power target value P RCVreft Once this is determined, the SOC of the storage battery 15 t can be estimated.

[0068] The control device 50 determines the receiving power target value P RCVreft With the variable, the SOC of the storage battery 15 t From the results, the four terms of the objective function F are calculated.

[0069] Such calculation is performed for the prediction target period T (if the prediction target period T is one day and the calculation cycle is one hour, the calculation is performed for 24 cycles). Then, the target value P RCVreft By comparing the values ​​of the objective function F for the combination patterns of the above, the combination of the receiving power target values ​​that minimizes the objective function F, that is, the receiving power target value P RCVreft It is possible to determine.

[0070] 6 and 7 are graphs with the horizontal axis representing time [h], the left vertical axis representing power [kW], and the right vertical axis representing SOC [%]. Y1 (bold line) represents the trend in received power [kW], and Y2 represents the trend in generated power [kW]. Y3 represents the trend in power consumption [kW] of the load, Y4 represents the trend in output power [kW] of the storage battery, and Y5 (dashed line) represents the trend in SOC [%] of the storage battery 15.

[0071] FIG. 6 shows the target receiving power value P RCVref When is determined empirically, Fig. 7 shows the receiving power target value P RCVref is determined based on the objective function F.

[0072] Receiving power target value P RCVref When the SOC is determined empirically (FIG. 6), the SOC of the storage battery 15 is maintained at approximately 100% during the time period from 4:00 p.m. to 6:00 p.m. Therefore, it is necessary to limit the acceptance of charges by the storage battery 15 during the time period from 4:00 p.m. to 6:00 p.m.

[0073] Receiving power target value P RCVref When the target value P is determined based on the objective function F (FIG. 7), the SOC of the storage battery 15 is in a state where it is always possible to charge and discharge the battery 15 with a margin relative to the SOC upper limit line Lim1 (SOCMAX=100[%]) and the SOC lower limit line Lim2 (SOCMIN=10[%]). RCVref Compared to the case where it is determined based on experience, the SOC is kept low for the time period from 4:00 pm to 6:00 pm (part A), and there is an improvement in that there are no restrictions on charging during this time period.

[0074] 4. Microgrid Power Control The control device 50 receives the power P RCV is the target power receiving value P calculated using the objective function F. RCVref The power control of the microgrid S1 is performed so as to follow the

[0075] For example, when the power receiving point 3 is in the forward flow and the inverter circuit 31 is in the reverse conversion operation, the received power P RCV The measured value of the receiving power target value P RCVref If the received power P RCV Measured value and target value of receiving power P RCVref The difference between the received power and the RCV The measured value of the receiving power target value P RCVref If the received power P RCV Measured value and target value of receiving power P RCVref Reduce the difference between.

[0076] As described above, the received power P RCV The output of the storage battery 15 is adjusted according to the difference between the measured value and the target value, so that the received power P RCV The target value of the received power P calculated using the objective function F RCVref It is possible to make it follow the

[0077] 5. Methods for reducing computational load Receiving power target value P RCVref To determine the optimal value of, for each time slice t of the prediction period T, the target power receiving value P RCVref It is necessary to estimate the SOC of the storage battery 15 and calculate each term of the objective function F for the number of candidates. For example, if the prediction target period T is one day and the number of time slices is 24, the receiving power target value P RCVref When the power receiving target value P is changed in increments of 1 kW in the range of 0 to 10 kW, RCVref The total number of candidates is 11 24 =9.85×10 24 The computational load increases in proportion to the total number of candidates.

[0078] The computational load of optimization calculations can be reduced by using the following two methods. (A) Restrictions on the range of change in the target receiving power value (B) Dividing the forecast period T

[0079] Let us explain (A). Receiving power P RCV Since the change in may affect the power quality of the power system 1, it is desirable to make the change as small as possible. Therefore, as shown in Equation 23, the target value P RCVref Set restrictions on the range of change.

[0080]

number

[0081] 8A and 8B show the receiving power target value P RCVreft FIG. 8A shows a combination of candidates for the receiving power target value P RCVref 8B shows the case where no restriction is placed on the range of change in the receiving power target value P RCVref The maximum change range is set to ±2 [kW].

[0082] Target power receiving value P per time slice t RCVref The number of candidates is the target power receiving value P RCVref When there is no restriction on the range of change in the power receiving target value P RCVref When the maximum value of the change range is set to ±2 [kW] (as in FIG. 8B), the result is "5".

[0083] In this way, the target receiving power value P RCVref By restricting the range of change in RCVref This reduces the number of candidates, and the calculation load can be significantly reduced. This reduces the impact on the power grid 1, and makes it possible to maintain the quality of electricity.

[0084] Let us explain (B). B1. Division of Sections The prediction target period T is divided into a plurality of intervals ΔT. Then, each divided interval ΔT is treated as one prediction target period, and the control device 50 performs optimization calculations to optimize the energy efficiency of the microgrid S1. In other words, the received power target value P RCVref Determine the optimal value of

[0085] For example, when the prediction target period T is one day, it is divided into four intervals ΔT, ΔT1 to ΔT4, as shown in FIG. 9. Then, with each interval ΔT being one prediction target period, the control device 50 calculates the receiving power target value P RCVref Find the optimal value of .

[0086] In this case, the target power receiving value P for the entire forecast period T is RCVref is the target power receiving value P for each time section t of each section ΔT determined as the optimal value. RCVref are connected in chronological order.

[0087] Forecast target period By dividing T, the target power receiving value P for the entire forecast period T is calculated. RCVref Therefore, the target power receiving value P RCVref Since the number of candidate combinations is reduced, the computational load can be significantly reduced.

[0088] The number of divisions N of the forecast period T can be any number other than 4, such as 3. good However, they do not have to be the same. It is preferable that each section ΔT is longer than the period of the power generation prediction and the load prediction. In the example of Fig. 9, ΔT = 6 hours, and the period of the power generation prediction and the load prediction = 1 hour.

[0089] B2. Ensuring spare battery capacity at the start of the next section Figure 10 shows the prediction target period 10 is a graph showing a forecast of power supply and demand for T. The forecast of power supply and demand can be made from a forecast value of power generation by the photovoltaic power generation panel 10, a forecast value of power consumption by the load L, and a target value of power received from the power grid 1. Y1 in Fig. 10 indicates the target value of power reception (minimum), Y2 indicates the forecast value of power generation, and Y3 indicates the forecast value of power consumption.

[0090] Forecast target period If you divide T and perform optimization calculations for each interval ΔT, n If we calculate only by considering the supply and demand forecast within the next section, ΔT n+1 At the start of the next section ΔT n+1 In some cases, the battery 15 may not be able to secure the surplus or shortage of power required for absorbing the power surplus or shortage in the section ΔT n At the end of the next section, ΔT n+1 There is a problem of how to secure the surplus capacity of the storage battery 15 in anticipation of the electricity supply and demand forecast. The surplus capacity is the free capacity that can be charged when the surplus of electricity is charged and stored. It is also the capacity that can be discharged when the shortage of electricity is compensated for by discharging.

[0091] In order to solve the above problem, the control device 50 of the power conditioner 20 is n The final SOC range of the storage battery 15 is set as the next section ΔT n+1 The calculation is based on the electricity supply and demand forecast.

[0092] Section ΔT n Final SOC = next section ΔT n+1 Since this is the start SOC of the section ΔT n By matching the final SOC of the storage battery 15 with the calculated range, the section ΔT n+1 At the start of the operation, the battery 15 can have a surplus capacity. In other words, the battery 15 can be operated with a margin relative to the upper limit SOCMAX and the lower limit SOCMIN of the usage range, and any excess or shortage of power can be absorbed and compensated for by charging and discharging. Fig. 11 is a flowchart of the calculation process for calculating the SOC range.

[0093] (S10) Final SOC upper limit SOC UPPER Calculation of The control device 50 controls the section ΔT n The upper limit of the final SOC of the storage battery 15 UPPER Next section ΔT n+1 This is calculated from the surplus power WC.

[0094] The surplus energy WC is the next interval ΔT n+1 In the above, the predicted power generation value P of the solar power generation panel 10, which is a distributed power source, PVt and the predicted power consumption value P of the load L LOADt is a value obtained by integrating the surplus power during the first period (A1 in FIG. 10) during which the difference between the power consumption and the power consumption is continuously positive.

[0095] The surplus power is the generated power P PV For power consumption P LOAD and receiving power P RCV The surplus power is the difference between the received power P RCV It depends on the size of the received power P RCV The smaller, the smaller.

[0096] If the storage battery 15 does not have a capacity to charge at least the minimum surplus power amount WC, energy loss occurs. PVt and the predicted power consumption value P LOADt and the minimum receiving power target value P RCVrefmin t Based on this, the next section ΔT n+1 The minimum surplus energy WC is calculated.

[0097] Next section ΔT n+1 The minimum receiving power target value P RCVrefmin t is the interval ΔT n The final power receiving prediction value P RCV tend This can be calculated by subtracting the maximum change range set in (A) from the above for each time slice.

[0098] The surplus power WC is ΔT n+1 and ΔT n+2 For example, the calculation may be performed over a plurality of sections (for example, for a period of 6 to 8 hours).

[0099] In order to ensure a free capacity capable of charging the surplus energy WC in the first period A1, the value obtained by subtracting the SOC corresponding to the surplus energy WC from the upper limit SOCMAX of the usage range of the storage battery 15 is set to the range ΔT n The upper limit of the final SOC of the storage battery 15 UPPER The surplus energy WC is at least good Or it could be something else.

[0100] In FIG. 12, "Lim1" indicates the upper limit of the use range SOCMAX, and "Lim3" indicates the upper limit of the final SOC SOC UPPER "Y5" is the SOC of the storage battery 15. The upper limit SOCMAX of the usage range is the limit value on the charging side of the SOC (the value above which charging is not possible).

[0101]

number

[0102] In the microgrid S1, depending on the balance between power supply and demand, power may be insufficient as well as in surplus. When the final SOC of the storage battery 15 is near the lower limit SOCMIN of the usage range, the time section t cross Therefore, the control device 50 sets the lower limit value SOC of the final SOC so that there is a margin for discharge. LOWER Calculate.

[0103] (S20) Final SOC lower limit SOC LOWER Calculation of Section ΔT n The lower limit of the final SOC of the storage battery 15 LOWER is the next interval ΔT n+1 From the start of the first period A2 (time period t cross The amount of power shortage WD is calculated for the second period A2 (from 0 to 100). The amount of power shortage WD is a value obtained by accumulating the power shortage for the second period A2.

[0104] The power shortage is the power consumption P LOAD Generated power P PV and receiving power P RCV The power shortage is the power received from the power grid P RCV It depends on the size of the received power P RCV The smaller, the larger.

[0105] If the storage battery 15 has a surplus capacity capable of discharging the maximum power shortage WD, the minimum received power can be maintained, and the energy utilization efficiency is high. PVt and the predicted power consumption value P of the load L LOADt and the minimum receiving power target value P RCVrefmint Based on this, the next section ΔT n+1 The maximum power shortage WD is calculated for the second period A2.

[0106] If the discharge amount of storage battery 15 exceeds the power shortage WD, a reverse power flow occurs. Since a reverse power flow occurs from storage battery 15 to the grid, exceeding the power shortage WD is not permissible.

[0107] In order to ensure that the capacity to discharge the energy deficit WD is secured, the value obtained by adding the SOC corresponding to the energy deficit WD to the lower limit SOCMIN of the usage range of the storage battery 15 is within the range ΔT n Final SOC lower limit SOC LOWER The power deficit WD is good In FIG. 12, "Lim2" indicates the lower limit SOCMIN of the use range, and "Lim4" indicates the lower limit SOC of the final SOC. LOWER Y5 is the SOC of the storage battery 15. The lower limit SOCMIN of the usage range is the limit value on the discharge side of the SOC (the value above which the battery cannot be discharged).

[0108]

number

[0109] (S30) Penalty for deviation Therefore, the section ΔT n Regarding the final SOC of the storage battery 15 in LOWER Lower limit, SOC UPPER It is possible to obtain a range Z (see FIG. 12) with an upper limit of

[0110] If the final SOC of the storage battery 15 deviates from the range Z, that is, does not match, a penalty is calculated. If it does not deviate from the range Z, that is, matches, no penalty is calculated.

number

[0111] Equation 27 is the objective function E in which the penalty evaluation terms are added to four items for the objective function F. The interval ΔT is set as one forecast period, and the power receiving target value P RCVref Calculate the optimal value of

[0112] And, for each section ΔT n When performing optimization calculations for the interval ΔT n The final SOC of the storage battery 15 is calculated for the next division section ΔT n+1 Initial SOC of the battery 15 INI Then, steps S10 to S30 are repeated for the number of sections. After all sections are completed, the target power receiving value P RCVref The optimal solution can be obtained.

[0113] By adding a penalty evaluation term to the objective function E, a solution with no or small penalty can be obtained as the optimal solution. n It is possible to suppress the final SOC from matching range Z.

[0114]

number

[0115] The magnitude relationship between the coefficients k5 and k6 that determine the penalty weight and the other coefficients may be k1>k2>k3>k4>k5>k6. It may also be k5>k6>k1>k2>k3>k4. The magnitude relationship between the two coefficients may be k5>k6. good And k5 <k6でもよい。

[0116] 6.Effects The storage battery 15 compensates for power shortages by charging the storage battery 15 with surplus power from the microgrid S1 and discharging the battery when there is a power shortage. If the use of the storage battery 15 is restricted, the surplus power cannot be stored, resulting in energy loss, and the energy utilization efficiency of the microgrid S1 decreases.

[0117] In this configuration, the receiving power target value P RCVreft By finding the optimal value of , it is possible to minimize the usage restriction period of the storage battery 15. Therefore, from the viewpoint of the utilization efficiency of the storage battery 15, it is possible to optimize the utilization efficiency of the energy of the microgrid S1.

[0118] In this configuration, the prediction period T is divided into multiple intervals ΔT, and optimization calculations are performed to optimize the energy usage efficiency of the microgrid S1. This reduces the calculation load and shortens the time required to calculate the optimal solution.

[0119] In this configuration, the section ΔT n The final SOC range Z of the next section ΔT n+1 The final SOC for the next section ΔT is determined based on the forecast of the power supply and demand. n+1 Since this is the start SOC of the section ΔT n By making the final SOC of the next section ΔT n+1 At the start of the next section ΔT n+1 The storage battery 15 can secure a surplus capacity to absorb any subsequent power surplus or shortage.

[0120] In this configuration, the next section ΔT n+1 Based on the prediction of the future supply and demand of electricity, the surplus energy WC in the first period A1 in which the supply of electricity exceeds the demand is calculated. n Final SOC upper limit SOC UPPER is determined to be the upper limit of the range of use SOCMAX minus the SOC equivalent to the surplus energy WC. In this configuration, the next section ΔT n+1 At the start of the operation, the battery 15 can have a surplus capacity for charging the surplus power of the microgrid S1. Therefore, the energy loss can be suppressed.

[0121] In this configuration, the next section ΔT n+1 The amount of energy shortage WD is calculated for the second period A2 from the start of the first period A1 to the start of the second period A2. n Final SOC lower limit SOC LOWER is determined to be a value obtained by adding the SOC corresponding to the power shortage WD to the lower limit SOCMIN of the usage range. n+1 At the start of the power outage, the battery 15 can have a surplus capacity to discharge the power shortage of the microgrid S1. Therefore, the energy can be used efficiently.

[0122] <Other embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included within the technical scope of the present invention.

[0123] (1) In the first embodiment, a grid having a linear power line (trunk) 5 is shown as an example of the microgrid S1, but a grid having a circular power line (trunk) may also be used. The microgrid S2 shown in Fig. 13 has a circular power line 100. A solar power generation panel 110 and a wind power generator 120 are connected to the power line 100 via power converters 115 and 125. A load 130 and a storage battery 140 are connected to the power line 100. The power line 100 of the microgrid S2 is connected to the power system 1 via an interconnection line 105.

[0124] The microgrid S2 includes a control device 150. The control device 150 divides the prediction target period T into a plurality of sections, performs an optimization calculation to optimize the energy utilization efficiency of the microgrid S2, and calculates a receiving power target value P RCVref The control device 150 calculates the optimal solution when the received power at the power receiving point 3 is equal to or smaller than the calculated received power target value P RCVref Specifically, the power receiving point 3 is controlled based on the output of the meter 160 provided at the power receiving point 3 so as to follow the received power P RCV Then, the control device 150 monitors the receiving power target value P RCVref If there is a difference with respect to the received power P, the difference is reduced by charging or discharging the storage battery 140 via the power converter 145. RCV The calculated target value P RCVref This allows the controller 150 to follow the current state of the microgrid S2 and optimize the energy utilization efficiency of the microgrid S2. The controller 150 is an example of the "computing device" of the present invention.

[0125] The term "distributed power sources" is a general term for small-scale power generation facilities that are distributed adjacent to demand areas. Distributed power sources may be, for example, biomass power generation devices in addition to the solar power generation panels 10 and wind power generators 120. Distributed power sources may also be power sources that utilize renewable energy. good And even with fossil fuel power sources good .

[0126] (2) In the first embodiment, a calculation was performed to optimize the energy utilization efficiency of the microgrid S1 using the target value of received power as a variable. A calculation may be performed to optimize the energy utilization efficiency of the microgrid using the SOC of the storage battery 15 as a variable. The present technology is not limited to a microgrid (small-scale power system) and can be applied to any grid (power system) that is linked to another power system and includes a power storage device. In the first embodiment, the storage battery 15 is exemplified as the power storage device, but the power storage device may be a capacitor or the like.

[0127] (3) In the first embodiment, the objective function F is a function that is composed of four terms, the first term to the fourth term, and that multiplies and adds these four terms by weighting coefficients k1 to k4. In the first embodiment, the magnitude relationship of the weighting coefficients is k1>k2>k3>k4, but it may be k3>k4>k1>k2. By reversing the magnitude relationship of the weighting coefficients, it is possible to prioritize the evaluation of the electricity rate of the microgrid, and therefore it is possible to optimize the energy utilization efficiency of the microgrid from the viewpoint of the electricity rate. The objective function F includes only the first and second terms that evaluate the usage restriction period of the storage battery 15. good However, even just the third and fourth items that evaluate the electricity tariff of the microgrid good The objective function F may be any function other than the one that optimizes the energy utilization efficiency of the microgrid. The same is true for the objective function E.

[0128] (4) In the first embodiment, the optimization calculation for optimizing the energy utilization efficiency of the microgrid is performed by the control device 51 of the power conditioner 20. The main body of the calculation is not limited to the power conditioner 20, and may be a calculation device provided separately from the power conditioner 20.

[0129] (5) In the first embodiment, the calculation for optimizing the energy utilization efficiency of the microgrid is exemplified by using the objective functions E and F. However, the calculation may be performed using, for example, AI.

[0130] (6) In the first embodiment, the section ΔT n Final SOC upper limit SOC UPPER and lower limit SOC LOWER For example, the next section ΔT n+1 In the case where the second period A2 in which power is insufficient does not exist before the first period A1, the upper limit value SOC of the final SOC is set based on the surplus power WC in the first period A1. UPPER The final SOC lower limit may be set as the lower limit of the range of use SOCMIN. n+1 In the case where only a period of power shortage exists, the lower limit of the final SOC SOC is set based on the power shortage WD. LOWER The upper limit value of the final SOC may be set as the upper limit SOCMAX of the usage range.

[0131] (7) In the first embodiment, the SOC [%] of the storage battery 15 is evaluated in the calculation for optimizing the energy utilization efficiency of the microgrid. Instead of the SOC [%], the remaining capacity [Ah] of the storage battery 15 may be evaluated. In other words, the prediction target interval ΔT n The range of the final remaining capacity of is determined based on the power supply and demand forecast for the next section and thereafter, and the forecast target section ΔT n of Energy efficiency In the optimization calculation, the interval ΔT n The final remaining capacity of the battery may be evaluated to see if it matches the determined range. The SOC and remaining capacity are examples of the "state of charge" of the battery.

[0132] (8) In the first embodiment, the prediction period T is divided into multiple intervals in order to reduce the load of the optimization calculation. The present technology can be applied when the optimization calculation is performed for any prediction interval, regardless of whether the prediction period is divided or not. [Explanation of symbols]

[0133] 1 Power system 2 power supplies 3 Receiving point 10. Photovoltaic power generation panel (an example of the "distributed power source" of the present invention) 15 Energy storage device 20 Power conditioner (an example of the "computing device" of the present invention) 21 First converter circuit 23 Second converter circuit 31 Inverter circuit 40 External measuring instruments 50 Control device S1, S2 Microgrid

Claims

1. A calculation device that optimizes energy utilization efficiency of a grid that is connected to a power system and has a power storage device, A computing device that determines the range of the final state of charge of the storage device for a prediction target section based on a supply and demand forecast of electricity for the next section and thereafter, and evaluates whether the final state of charge of the prediction target section matches the range in an optimization calculation of energy utilization efficiency for the prediction target section.

2. 2. The computing device of claim 1, Calculating an amount of surplus power in a first period in which the supply of power exceeds the demand in the next section and thereafter based on a supply and demand forecast of power in the next section and thereafter; A calculation device that determines an upper limit value of the final state of charge of the prediction section to be a value obtained by subtracting a numerical value corresponding to the amount of surplus power from an upper limit of a usage range of the power storage device.

3. 3. A computing device as claimed in claim 2, comprising: Calculating a minimum amount of surplus power in the first period based on a forecast of power supply and demand for the next section and thereafter; A calculation device that determines an upper limit value of the final state of charge of the prediction section to be a value obtained by subtracting a numerical value corresponding to the minimum amount of surplus power from an upper limit of a usage range of the power storage device.

4. A computing device according to claim 2 or claim 3, Calculating an amount of power shortage resulting from the supply of power falling short of the demand for a second period from the start of the next section to the first period; a calculation device that determines a lower limit of the final state of charge of the prediction section to be a value obtained by adding a numerical value corresponding to the amount of power shortage to a lower limit of a usage range of the power storage device.

5. 5. A computing device according to claim 4, comprising: Calculating a maximum energy shortage amount for the second period based on a power supply and demand forecast for the next section and thereafter; a calculation device that determines a lower limit of the final state of charge of the prediction section to be a value obtained by adding a numerical value corresponding to the maximum amount of energy shortage to a lower limit of a usage range of the power storage device.

6. A computing device according to any one of claims 1 to 5, A computing device that optimizes energy utilization efficiency by calculating an optimal value of a target value of received power in a forecast target section of the grid based on a power demand forecast.

7. A computing device according to any one of claims 6, A computing device that adjusts an output of the power storage device in accordance with a difference between a measured value of received power of the grid and the target value of received power.

8. A calculation method for optimizing energy utilization efficiency of a grid that is connected to a power system and has a power storage device, comprising: A calculation method in which the range of the final state of charge of the storage device for a prediction target section is determined based on a power supply and demand forecast for the next section and thereafter, and an optimization calculation of the energy utilization efficiency for the prediction target section is performed to evaluate whether or not the final state of charge of the prediction target section matches the range.

9. A program for optimizing energy utilization efficiency of a grid that is connected to a power grid and has a power storage device, A process of determining a range of a final state of charge of the power storage device in a prediction target section based on a supply and demand prediction of power in a next section and thereafter, and evaluating whether or not a final state of charge of the prediction target section matches the range in an optimization calculation of energy utilization efficiency of the prediction target section.

10. A power storage system connected to a power grid, A computing device according to any one of claims 1 to 7; A power storage system including a power storage device.

11. A power generation system interconnected with an electric power grid, A computing device according to any one of claims 1 to 7; A power generation system comprising:

12. A grid connected to a power system, A computing device according to any one of claims 1 to 7; A power storage device; A grid including a distributed generation system.

Images