Power system and control method for power system

Abstract

To control the power system output without using the power generation unit maximum output data.SOLUTION: An electric power system S1 connected to a power grid 1 includes multiple power generation units 30A to 30C connected in parallel, and a control device 80. The control device 80 determines an output upper limit value for each time period of the electric power system S1 on the basis of the contracted capacity Y with an electric utility company and the power suppression for each time period instructed by the electric utility company, obtains data of outputs XA to XC from the respective power generation units 30A to 30C connected in parallel, calculates a total value XT of the output power XA to XC of the power generation units 30A to 30C connected in parallel, and controls the output power XA to XC of the respective power generation units 30A to 30C connected in parallel on the basis of the result of comparison between the output upper limit value of each time period of the electric power system S1 and the total value XT of the output power XA to XC of the power generation units 30A to 30C connected in parallel.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technique for controlling the output of a power system interconnected with a power grid. [Background technology]

[0002] In order to reduce dependence on fossil fuels and address environmental issues, the introduction of distributed power sources such as photovoltaic (PV) power generation is being promoted. PV units convert the electricity generated by solar panels from direct current to alternating current using power conversion devices such as inverter circuits, and then output the converted electricity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-200167 Summary of the Invention [Problem to be solved by the invention]

[0004] 1, in the case of a power system S0 having a plurality of power generating units 10A, 10B connected in parallel, it is conceivable to set the maximum output power of each power generating unit 10A, 10B to a reference value (100%) and control the output power of each power generating unit 10A, 10B individually. For example, if the output upper limit value of the entire power system is 50% of the sum of the maximum output power of each power generating unit 10A, 10B, the output power of each power generating unit 10A, 10B may be controlled to 50% of the maximum output power.

[0005] The maximum output power of the power generation units 10A and 10B is the maximum output in terms of performance, and is the smaller of the two capacities of the "power generation capacity (power generation capability) of the PV panel 11" and the "output capacity (output capability) of the power conversion device 13." For example, in the case of the power generation unit 10A, the power generation capacity of the PV panel 11A is 10 [kW] and the output capacity of the power conversion device 13A is 8 [kW], so the maximum output power is 8 [kW].

[0006] When the maximum output power of each power generation unit 10A, 10B is set to a reference value (100%) and the output power of each power generation unit 10A, 10B is controlled individually, data on the "power generation capacity of the PV panels 11A, 11B" and the "output capacity of the power conversion device 13" must be collected during initial setup in order to determine the maximum output power of each power generation unit 10A, 10B.

[0007] However, when the number of power generation units increases, it becomes time-consuming to collect data during initial setup, and if errors occur in data collection or input, the power system may not be able to perform to its full potential.Similar problems also arise when using distributed power sources other than PV panels as power generation units. An object of the present invention is to control the output of a power system without using data on the maximum output power of a power generating unit. [Means for solving the problem]

[0008] The power system connected to the power grid includes a plurality of power generation units connected in parallel, a control device, and a distributed power source, and a power conversion device that converts the power of the distributed power source into AC power and outputs the AC power.

[0009] The control device determines an output upper limit value for each time period of the power system based on the contract capacity with the electric utility and a power suppression value for each time period instructed by the electric utility. The control device acquires output power data from each of the power generation units connected in parallel and calculates the total value of the output power of the power generation units connected in parallel. The control device controls the output power of each of the power generation units connected in parallel based on a comparison result between the output upper limit value for each time period of the power system and the total value of the output power of the power generation units connected in parallel.

[0010] This technology can be applied to control methods and control programs for power systems. [Effects of the Invention]

[0011] This configuration makes it possible to control the output power of the power system without using data on the maximum output power of the power generating unit. [Brief explanation of the drawings]

[0012] [Figure 1] Diagram of the problem [Figure 2] Power System Block Diagram [Figure 3] Output Limitation Schedule [Figure 4] Flowchart of output control process [Figure 5] S80 subroutine [Figure 6] Graph showing output trends of power systems and power generating units [Figure 7] Power generation unit output status display screen [Figure 8] Power system configuration display screen DETAILED DESCRIPTION OF THE INVENTION

[0013] The power system connected to the power grid includes a plurality of power generation units connected in parallel, a control device, and a distributed power source, and a power conversion device that converts the power of the distributed power source into AC power and outputs the AC power.

[0014] The control device determines an output upper limit value for each time period of the power system based on the contract capacity with the electric utility and a power suppression value for each time period instructed by the electric utility. The control device acquires output power data from each of the power generation units connected in parallel and calculates the total value of the output power of the power generation units connected in parallel. The control device controls the output power of each of the power generation units connected in parallel based on a comparison result between the output upper limit value for each time period of the power system and the total value of the output power of the power generation units connected in parallel.

[0015] With this configuration, the output power of the power system can be controlled without using data on the maximum output power of the power generation units. Therefore, there is no need to collect data on the power generation capacity of the distributed power sources or the output capacity of the power conversion devices during initial setup, reducing the effort required for initial setup. It also prevents the performance of the power system from being limited by data collection or input errors. Furthermore, if the power system includes power generation units with surplus capacity, even if some of the power generation units fail, the loss of power generation due to the failure can be compensated for by increasing the output power of the power generation units with surplus capacity.

[0016] The output conditions of each power generation unit are not necessarily the same and may differ. For example, in the case of solar power generation, the amount of power generated by a PV panel is affected by solar radiation, so the output power of each PV panel differs depending on the solar radiation conditions. Even if a distributed power source other than PV panels is used for the power generation unit, the output conditions are not necessarily the same and may differ.

[0017] When controlling the output power of power generation units individually, if the output status of each power generation unit differs when a request is received from an electric utility to limit the output of the power system, power generation units with large power generation volumes and high output may have their output restricted more than necessary.

[0018] For example, suppose an electric power system consists of three power generating units, and the output limit requested by the electric utility is 50% of the total maximum output power of each generating unit. If the three generating units are operating at 60%, 50%, and 40% of their maximum output power when the output limit is imposed, the average output of the three generating units is 50% of their maximum output power, and considering the power system as a whole, it is operating at 50% of its maximum output power, so there is no need to reduce the output of the generating units.

[0019] However, if the output power of the three power generation units is controlled individually in accordance with the output limits requested by the electric utility (limiting them uniformly to 50% or less), the power generation unit with 60% output will be adjusted to 50% output. As a result, when considering the power system as a whole, the output power will be limited beyond the output limits requested by the electric utility, and losses may occur.

[0020] With this configuration, regardless of the power generation status or output status of each power generation unit, the total output power of the power generation units connected in parallel can be controlled to the power system's output upper limit for each time period, and the power output power of the power system will not be limited beyond the output limit requested by the electric utility. In the above example, a power generation unit with 60% output will not be adjusted to 50% and will be able to maintain 60% output. This reduces power output loss in the power system and enables effective use of energy generated by distributed power sources.

[0021] This configuration not only reduces output loss from the power generation unit and enables effective use of generated energy, but also prevents the output power of the power system from exceeding the power suppression value for each time period instructed by the electric power company, which would result in a breach of contract.

[0022] The control device may increase the output power of each of the power generating units connected in parallel from the output power of each of the power generating units at the time when the total output power is calculated, when the total output power of the power generating units connected in parallel is less than the output upper limit of the power system. In this configuration, when the total output power of the power generating units connected in parallel is less than the output upper limit of the power system, the control device increases the output power of each of the power generating units until it reaches the output upper limit of the power system. Therefore, the power system will not continue to operate when the total output power of the power generating units connected in parallel is insufficient for the output upper limit, and energy generated by the distributed power source can be used without loss.

[0023] When the total output power of the power generating units connected in parallel is greater than the upper output limit of the power system, the control device may reduce the output power of each of the power generating units connected in parallel from the output power of each of the power generating units at the time the total output power was calculated. In this configuration, when the total output power of the power generating units connected in parallel exceeds the upper output limit of the power system, the control device reduces the output power of each of the power generating units until it reaches the upper output limit of the power system. As a result, the total output power of the power generating units connected in parallel does not continue to exceed the upper output limit of the power system, suppressing voltage increases in the power grid and contributing to maintaining the quality of electricity.

[0024] When the total value of the output power of the power generation units connected in parallel is equal to the contract capacity of the electric utility, the control device may record the output power of each of the power generation units connected in parallel as the maximum output value relative to the contract capacity. The maximum output value relative to the contract capacity may be displayed on a screen showing the output status of the power generation units, along with the progress of the output power of the power generation units. By displaying the maximum output value relative to the contract capacity, it becomes easier to understand how much output a power generation unit is able to produce relative to the contract capacity. The maximum output value relative to the contract capacity of each power generation unit may be displayed together with each power generation unit on a screen showing the system configuration of the power system. It becomes easier to understand the setting of the maximum output value of each power generation unit.

[0025] The distributed power sources may be photovoltaic power generation panels. When there is a difference of a predetermined value or more between the maximum output values ​​of the power generation units, the control device may display a message encouraging the rearrangement of the photovoltaic power generation panels of the power generation units with low maximum output values. Photovoltaic power generation panels are exposed to sunlight in different ways depending on the installation location, which can result in differences in the amount of power generated. By encouraging the rearrangement of the power generation units with low maximum output values ​​and rearranging the photovoltaic power generation panels to a location more suitable for power generation, the power generated by the photovoltaic power generation panels can be increased and the imbalance in maximum output values ​​can be eliminated or reduced.

[0026] <Embodiment 1> 1. Description of power system S1 2 is a block diagram of the power system S1. The power system S1 includes three power generation units 30A to 30C and a control device 80.

[0027] The power generation unit 30A includes a solar power generation panel 40A and a power conditioner 50A. The solar power generation panel 40A is an example of a "distributed power source," and the power conditioner 50A is an example of a "power conversion device."

[0028] The power conditioner 50A includes a converter circuit 51, an inverter circuit 53, a measuring instrument 54, and a unit control unit 55.

[0029] The solar panel 40A is connected to the converter circuit 51. The converter circuit 51 is a DC / DC converter. The converter circuit 51 boosts the output (direct current) of the solar panel 40A and outputs it to the inverter circuit 53.

[0030] The inverter circuit 53 performs an inverse conversion operation to convert DC to AC. The inverter circuit 53 converts the DC power input from the converter circuit 51 into AC power and outputs it.

[0031] The measurement unit 54 measures the output voltage Vinv and the output current Iinv of the inverter circuit 53. The measurement results of the measurement unit 54 are input to the unit control unit 55.

[0032] The unit control unit 55 has a CPU 56 and a memory 57. The unit control unit 55 monitors the output power of the power conditioner 50A, i.e., the output power XA of the power generation unit 30A, based on the measurement results of the measurement unit 54. The unit control unit 55 controls the output power XA [kW] of the power generation unit 30A based on commands from the control device 80. Hereinafter, the output power will be simply referred to as output.

[0033] The power generation unit 30A is connected to the power system 1 via an interconnection line L0. The power system 1 is a system operated by an electric utility company and includes a system power source 3. A dashed line F shown in FIG. 2 indicates the boundary between the power system 1 and the power system S1. A load 110 is connected to point A on the interconnection line L0 via a branch line L1.

[0034] The power generation units 30B and 30C have the same configuration as the power generation unit 30A, and the power generation unit 30B has a solar power generation panel 40B and a power conditioner 50B. The power generation unit 30C has a solar power generation panel 40C and a power conditioner 50C. A parallel line L2 is connected to point B of the interconnection line L0. The power generation units 30B and 30C are connected in parallel to the power generation unit 30A via the parallel line L2.

[0035] The control device 80 has a CPU 81, a memory 83, an input unit 84, a communication unit 85, and a display unit 87. The memory 83 stores a program for controlling the output of the power system S1 and data necessary for controlling the output of the power system S1. The input unit 84 is for inputting data. The control device 80 is connected to be able to communicate with the unit control units 55 of each of the power conditioners 50A to 50C via a communication line L3.

[0036] The communication unit 85 is for communication connection with the network NW. A power server 100 operated by an electric utility company is connected to the network NW. The display unit 87 displays the system configuration of the power system S1 and the output status of each of the power generation units 30A to 30C.

[0037] 2. Output restriction of power system S1 The output limit of the power system S1 is implemented at the request of the electric utility company in order to balance the supply and demand of electricity. Figure 3 shows an example of an output limit schedule distributed from the electric utility company's power server 100. The output limit schedule determines the upper output limit value of the power system S1 for each time slot T using an output suppression value K.

[0038] The output suppression value K is a ratio to the contracted capacity Y [kW] of the power system S1. For example, when K=50%, the output upper limit value of the power system S1 is set to 50% of the contracted capacity Y [kW].

[0039] The contracted capacity Y [kW] is the maximum capacity (maximum power) that the power system S1 can output, and is contracted between the operator of the power system S1 and the electric utility that operates the power grid 1 to which the power system S1 is connected.

[0040] 3. Output control process of power system S1 4 is a flowchart of the output control process of the power system S1. The output control process consists of 10 steps S10 to S100. The two processes S10 and S20 are mainly executed when the power system S1 is initially set up.

[0041] In S10, a process is performed in which the contract capacity Y [kW] of the power system S1 is input to the control device 80. The contract capacity Y [kW] is input by, for example, a maintenance worker. The input contract capacity Y is stored in the memory 83.

[0042] In S20, a process is performed in which the number N of connected power conditioners 50 connected to the power system 1 is input to the control device 80. In this example, the number of connected power conditioners 50 is three, so "N=3" is input.

[0043] The number of connected units N may be input by a maintenance person, or may be automatically detected by the control device 80 using communication with each of the power conditioners 50A to 50C. The input or automatically detected number of connected units N is stored in the memory 83.

[0044] The eight processes of S30 to S100 are processes that are executed at a predetermined cycle while the power system S1 is in operation (power generation). When the solar power generation panels 40A to 40C of each power generation unit 30A to 30C start generating power due to solar radiation, the power conditioners 50A to 50C convert the DC power generated by the solar power generation panels 40A to 40C into AC power and output it, without relying on the maximum output power of the performance of each power generation unit.

[0045] In S30, the control device 80 accesses the power server 100 via the network NW and reads the data of the output restriction schedule into the memory 83. Then, the control device 80 acquires the output suppression value K [%] for the corresponding time slot T.

[0046] In S40, the control device 80 calculates an output upper limit value XG of the power system S1. The output upper limit value XG is the product of the contract capacity Y [kW] and the output suppression value K [%], and is calculated and updated for each time slot T.

[0047] XG = Y × K (1)

[0048] The output upper limit value XG may be determined based on the contract capacity Y [kW] and the output suppression value [%], and may be a value that is several percent smaller than Y×K, for example.

[0049] In S50, the control device 80 accesses each of the power conditioners 50A to 50C to acquire data on the outputs XA to XC of each of the power generation units 30A to 30C.

[0050] The control device 80 calculates the total output value XT of the three power generating units 30A to 30C from the acquired data of the outputs XA to XC. The total output value XT is the overall output of the power system S1.

[0051] XT = XA + XB + XC (2) XA to XC are the outputs [kW] of the power generation units 30A to 30C, respectively.

[0052] In S60, the control device 80 determines the total output value XT of the power generation units 30A to 30C. Specifically, it determines whether the total output value XT is equal to the output upper limit value XG. Even if the two values XT and XG do not match, if the difference (XG - XT) is less than a predetermined value, it may be determined that they are equal.

[0053] When the total output value XT is not equal to the output upper limit value XG (S60: NO), the process proceeds to S80. When the process proceeds to S80, the control device 80 adjusts the outputs of the power generation units 30A to 30C.

[0054] FIG. 5 is a subroutine of S80 (output adjustment process). In S81, the control device 80 determines whether the total output value XT is less than the output upper limit value XG.

[0055] When XT < XG, the process proceeds to S83, and the control device 80 sends a command to increase the outputs XA to XC of the power generation units 30A to 30C with respect to each of the power conditioners 50A to 50C from the current values. The current values are the outputs XA to XC of the power generation units 30A to 30C at the time when the total output value XT was calculated.

[0056] When XT > XG, the process proceeds to S85, and the control device 80 sends a command to decrease the outputs XA to XC of the power generation units 30A to 30C with respect to each of the power conditioners 50A to 50C from the current values. The current values are the outputs XA to XC of the power generation units 30A to 30C at the time when the total output value XT was calculated.

[0057] Upon receiving a command from the control device 80, the unit control sections 55 of each of the power conditioners 50A to 50C adjust the outputs XA to XC of the power generation units 30A to 30C to increase or decrease them by adjusting the output of the inverter circuit 53. The adjustment of the increase or decrease of the output may be performed by the converter circuit 51 to adjust the outputs of the solar power generation panels 40A to 40C.

[0058] By the output adjustment process of S80, the difference |XG - XT| between the total output value XT of the power generation units 30A to 30C with respect to the output upper limit value XG of the power system S1 becomes smaller.

[0059] Thereafter, the process returns to S30, and the loop R (S30 to S80) shown in FIG. 4 is repeated, so that the outputs XA to XC of the power generation units 30A to 30C are adjusted until the total output value XT becomes equal to the output upper limit value XG.

[0060] When XT=XG, the determination in S60 is YES, and the process proceeds to S70. When the process proceeds to S70, the control device 80 sends a command to each of the power conditioners 50A-50C to maintain the outputs XA-XC of each of the power generation units 30A-30C at their current values. The current values ​​are the outputs XA-XC of each of the power generation units 30A-30C at the time when XT=XG.

[0061] Thereafter, the process proceeds to S90, where the control device 80 determines whether the output suppression value K is 100[%]. If K=100[%] (S90: YES), the process proceeds to S100.

[0062] When the process proceeds to S100, the control device 80 records in the memory 83 each of the outputs XA to XC at the time when XT=XG, as the maximum output value Xmax for the contract capacity Y of each of the power generation units 30A to 30C.

[0063] Then, the process returns to S30. If K≠100[%] (S90: NO), the recording of the maximum output value Xmax is skipped, and the process returns to S30.

[0064] As described above, the control device 80 compares the total output value XT of each of the three power generating units 30A to 30C with the output upper limit value XG of the power system S1, and adjusts the outputs XA to XC of each of the power generating units 30A to 30C so as to reduce the difference (XG-XT).

[0065] Therefore, the total output value XT of the three power generation units 30A to 30C can be automatically adjusted to the output upper limit value XG of the power system S1.

[0066] While the power system S1 is operating (power generation), the output suppression value K [%] for the time slot T is read out and the output upper limit value XG is updated in accordance with the change in the time slot T in the output limit schedule. In this configuration, the total output value XT of the three power generation units 30A to 30C can be made to follow the output upper limit value XG updated according to the time slot T.

[0067] FIG. 6 is a graph showing the transition of the output of the power system S1 and the power generating unit 30A per day (weekday).

[0068] When solar panel 40A starts generating power due to solar radiation, power generation unit 30A converts the DC power generated by solar panel 40A into AC power using power conditioner 50A and outputs the AC power, without relying on the maximum output power of each power generation unit. The same applies to power generation units 30B and 30C.

[0069] At time t1 when power generation starts, the total output value XT of the power system S1 is below the output upper limit value XG. Therefore, a command to increase the outputs XA to XC of the power conditioners 50A to 50C is sent from the control device 80. As a result, after time t1, the outputs XA to XC of the power generation units 30A to 30C and the total output value XT of the power system S1 increase.

[0070] At time t2, the total output value XT of the power system S1 reaches the output upper limit value XG. Note that the output suppression value K at time t2 is 100%.

[0071] After time t2, a command to maintain outputs XA to XC at the current values ​​is transmitted from control device 80 to each of power conditioners 50A to 50C. As a result, after time t2, total output value XT of power system S1 is maintained at output upper limit value XG.

[0072] At time t3, output suppression value K decreases from 100% to 80%, and total output value XT of power system S1 becomes greater than output upper limit value XG. Therefore, after time t3, control device 80 sends commands to each of power conditioners 50A-50C to reduce their outputs XA-XC. Therefore, after time t3, outputs XA-XC of each of power generation units 30A-30C and total output value XT of power system S1 decrease.

[0073] At time t4, the total output value XT of the power system S1 decreases to the output upper limit value XG. After time t4, the control device 80 sends a command to each of the power conditioners 50A-50C to maintain the outputs XA-XC at their current values. As a result, after time t4, the total output value XT of the power system S1 maintains the output upper limit value XG.

[0074] At time t5, the amount of power generated by the solar power generation panels 40A to 40C decreases due to a decrease in solar radiation, and as a result, the total output value XT of the power system S1 decreases. Then, at time t6, power generation ends.

[0075] In the example of Figure 6, at time t2 when XT = XG, K = 100%, so the control device 80 records the outputs XA to XC of each of the power generation units 30A to 30C in memory 83 as the maximum output values ​​Xmax for the contract capacity Y of each of the power generation units 30A to 30C.

[0076] In the example of FIG. 6, since XA=10 [kW] at time t2, the maximum output value Xmax for the contract capacity Y of the power generation unit 30A is recorded as 10 [kW].

[0077] At time t2, for example, when XB=8 [kW] and XC=7 [kW], the maximum output value Xmax for the contract capacity Y of the power generating unit 30B is recorded as 8 [kW], and the maximum output value Xmax for the contract capacity Y of the power generating unit 30C is recorded as 7 [kW]. Normally, the maximum output value Xmax for the contract capacity Y is equal to or less than the maximum output power in terms of the performance of the power generating unit 30.

[0078] The control device 80 may display (broken line in FIG. 7) the maximum output value Xmax of the contract capacity Y for each of the power generating units 30A to 30C along with the transition of the outputs XA to XC of each of the power generating units 30A to 30C on a screen showing the output status of each of the power generating units 30A to 30C, such as the display unit 87. Displaying the maximum output value Xmax of the contract capacity Y makes it easier to grasp the output status of each of the power generating units 30A to 30C.

[0079] When there is a difference of a predetermined value or more in the maximum output value Xmax among the power generation units 30A to 30C, the control device 80 may display a message on the display unit 87 prompting the rearrangement (relocation) of the power generation units 30A to 30C with the lower maximum output value. The solar power generation panels 40A to 40C may be exposed to sunlight in different ways depending on the installation locations, which may result in differences in the amount of power generated. By prompting the rearrangement and rearranging the solar power generation panels 40A to 40C with the lower maximum output value in a location more suitable for power generation, the power generated by the solar power generation panels 40A to 40C can be increased and the imbalance in the maximum output values ​​can be eliminated. The message prompting the rearrangement may be displayed on a monitoring monitor or the like provided separately from the control device 80.

[0080] 4.Effectiveness In this configuration, the output power of the power system S1 can be controlled without using data on the maximum output power (maximum output in terms of performance) of each of the power generation units 30A to 30C.

[0081] Therefore, during initial setup, there is no need to collect data on the power generation capacity of the solar panels 40A-40C or the output capacity of the power conditioners 50A-50C, reducing the effort required for initial setup. It also prevents performance limitations of the power system S1 due to data collection or input errors. Furthermore, if the power system S1 includes power generation units 30A-30C with surplus capacity, even if one of the power generation units 30A-30C fails, the output XA-XC of the power generation units 30A-30C with surplus capacity can be increased to compensate for the decrease in power generation resulting from the failure.

[0082] In this configuration, if the total output value XT of the power system S1 is insufficient relative to the upper output limit value XG, adding solar power generation panels 40 (see FIG. 1) adjusts the output of the power generation units 30 to make up for the output shortage, so that the power generated by the added panels can be automatically output. This eliminates the need for setting up additional panels (inputting the increased power generation capacity), which has the advantage of simplifying the management of the power system S1.

[0083] In this configuration, regardless of the power generation status or output status of each power generation unit 30A-30C, it is possible to control the total output value XT of the power generation units 30A-30C connected in parallel to the output upper limit value XG for each time period of the power system S1, and the outputs XA-XC of the power generation units 30A-30C are not limited beyond the output limit requested by the electric utility. This makes it possible to reduce output loss in the power system S1 and make effective use of the generated energy.

[0084] <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.

[0085] (1) In the embodiment, the distributed power source is the solar power generation panel 40. The distributed power source may be a power source other than the solar power generation panel 40, such as a storage battery or a power source using renewable energy such as wind power generation. The distributed power source is not limited to a DC output, and may also be an AC output. In the case of an AC output, the AC output may be rectified and converted into DC, and then converted into AC by a power conversion device such as a power conditioner for output.

[0086] (2) In the embodiment, the power system S1 has three power generation units 30A to 30C. The number of power generation units 30 may be any number other than three, as long as it is two or more.

[0087] (3) In the above embodiment, the output upper limit value XG of the power system S1 is the product of the contract capacity Y [kW] and the output suppression value K [%]. The output upper limit value XG may be a different value determined by a different method as long as it is determined based on the contract capacity Y [kW] and the output suppression value K [%].

[0088] (4) In the above embodiment, the maximum output value Xmax for the contract capacity Y is displayed on a screen (for example, the display screen of the display unit 87) showing the output status of each of the power generating units 30A to 30C along with the transition of the outputs XA to XC of each of the power generating units 30A to 30C. As shown in FIG. 8 , the control device 80 may display the maximum output value Xmax for the contract capacity Y for each of the power generating units 30A to 30C on a screen (for example, the display screen of the display unit 87) showing the system configuration of the power system S1. Displaying the maximum output value Xmax for the contract capacity Y on the display screen of the system configuration of the power system S1 makes it easier to understand the setting of the maximum output value Xmax for the contract capacity Y for each of the power generating units 30A to 30C. The display format of the system configuration of the power system S1 may be any display format as long as it includes information on the maximum output value Xmax for the contract capacity Y for each of the power generating units 30A to 30C. Furthermore, the display location is not limited to the display unit 87. It may also be displayed on a monitoring monitor or the like provided separately from the control device 80. The same applies to the case where the output status of each of the power generation units 30A to 30C is displayed.

[0089] (5) In the above embodiment, when XT < XG, the control device 80 sends a command to increase the outputs XA to XC of each of the power conditioners 50A to 50C from the current values to the power generation units 30A to 30C, and performs control to increase the outputs XA to XC of the power generation units by 30A to 30C. When XT < XG, the control device 80 may control so that only some of the power generation units among the power generation units 30A to 30C increase the output, and the other power generation units maintain the output. For example, when there is a difference in the outputs XA to XC of the power generation units 30A to 30C, the output of the power generation unit with a high output may be maintained, and the output of the power generation unit with a low output may be increased. Even when only the output of the power generation unit with a low output is increased, the total output value XT increases, so the difference from the output upper limit value XG can be reduced. The same applies to the case where XT > XG, and control may be performed so that only some of the power generation units among the power generation units 30A to 30C decrease the output, and the other power generation units maintain the output. For example, when there is a difference in the outputs XA to XC of the power generation units 30A to 30C, the output of the power generation unit with a high output may be decreased, and the output of the power generation unit with a low output may be maintained.

Explanation of Signs

[0090] 1 Power system 3 System power source 30A~30C Power generation units 40A~40C Photovoltaic panels (an example of the "distributed power source" of the present invention) 50A~50C Power conditioners (an example of the "power conversion device" of the present invention) 80 Control device S1 Power system

Claims

1. An electric power system connected to an electric power grid, a plurality of power generating units connected in parallel; a control device; The power generation unit comprises: Distributed power sources and a power conversion device that converts the power of the distributed power source into AC power and outputs the AC power, The control device determining an output upper limit value for each time period of the power system based on a contract capacity with an electric power utility and a power suppression value for each time period instructed by the electric power utility; acquiring output power data from each of the power generation units connected in parallel, and calculating a total value of the output power of the power generation units connected in parallel; A power system that controls the output power of each of the power generation units connected in parallel based on a comparison result between an output upper limit value for each time period of the power system and a total value of the output power of the power generation units connected in parallel.

2. 2. The power system of claim 1, When the total value of the output power of the power generation units connected in parallel is smaller than the output upper limit value of the power system, the control device increases the output power of each of the power generation units connected in parallel to be greater than the output power of each of the power generation units at the time the total value of the output power was calculated.

3. The power system according to claim 1 or 2, When the total value of the output power of the power generation units connected in parallel is greater than the output upper limit value of the power system, the control device reduces the output power of each of the power generation units connected in parallel to be lower than the output power of each of the power generation units at the time the total value of the output power was calculated.

4. An electric power system connected to an electric power grid, a plurality of power generating units connected in parallel; a control device; The power generation unit comprises: Distributed power sources and a power conversion device that converts the power of the distributed power source into AC power and outputs the AC power, The control device determining an output upper limit value for each time period of the power system based on a contract capacity with an electric power utility and a power suppression value for each time period instructed by the electric power utility; acquiring output power data from each of the power generation units connected in parallel, and calculating a total value of the output power of the power generation units connected in parallel; controlling the output power of each of the power generation units connected in parallel based on a comparison result between an output upper limit value for each time period of the power system and a total value of the output power of the power generation units connected in parallel; When the total value of the output power of the power generation units connected in parallel is equal to the contract capacity with the electric utility, the control device records the output power of each of the power generation units connected in parallel as the maximum output value relative to the contract capacity.

5. 5. The power system of claim 4, The control device displays the maximum output value relative to a contract capacity along with a transition in the output power of the power generation unit on a screen showing the output status of the power generation unit.

6. 5. The power system of claim 4, The control device displays, on a screen showing a system configuration of the power system, the maximum output value of each of the power generation units connected in parallel, together with the contract capacity of each of the power generation units.

7. The power system according to any one of claims 4 to 6, the distributed power source is a solar power generation panel; When there is a difference of a predetermined value or more between the maximum output values ​​of the power generation units, the control device displays a message encouraging rearrangement of the solar power generation panels of the power generation unit with the lower maximum output value.

8. A power system according to any one of claims 1 to 3, The control device controls the output power of the power system without using data on the maximum output power of the power generation unit.

9. 1. A method for controlling a power system having a plurality of power generating units connected in parallel, comprising: determining an output upper limit value for each time period of the power system based on a contract capacity with an electric power utility and a power suppression value for each time period instructed by the electric power utility; acquiring output power data from each of the power generation units connected in parallel, and calculating a total value of the output power of the power generation units connected in parallel; A control method for a power system, which controls the output power of each of the power generation units connected in parallel based on a comparison result between an output upper limit value for each time zone of the power system and the total value of the output power of the power generation units connected in parallel.

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