JP4776475B2 - Power grid interconnection system - Google Patents

Description

  The present invention has a backbone power system and a small-scale power system linked to the backbone interconnection line, and the small-scale power system includes a plurality of children each having a power load and a power supply device for the power load. The present invention relates to a power grid interconnection system in which small-scale power grids are interconnected by child interconnection lines.

  In recent years, a power grid interconnection system has been used in which a small-scale power system constructed by a plurality of distributed power sources is linked with a large-scale backbone power system provided by a power company or the like and stably operated. In other words, along with the progress of low price, widespread use, and power liberalization of distributed power sources, there is an increase in small-scale power systems (also called microgrids) that can generate power with small distributed power sources such as diesel, gas, solar and wind power. I am doing.

  As described above, this small-scale power system is usually connected to the main power system, which is a commercial power system of an electric power company, at one point (one-point connection). For this reason, when a power supply failure such as a power failure due to an accident or the like occurs on the main power system side, a small power system may become a total power failure if no countermeasure is taken. In addition, the number of small-scale power systems and cases composed of several sub-small-scale power systems will increase in the future, and it is becoming difficult to perform control to prevent spillovers to small-scale power systems.

  Some proposals related to interconnection control and their operation in an electric power system using such a distributed power source have also been seen (see, for example, Patent Document 1 and Patent Document 2).

  Patent Document 1 is for preventing an important load of an in-house system from an instantaneous drop, and detects an instantaneous drop in a commercial system and switches the important load to the in-house system side. In other words, the critical load is switched to the private power system side for the instantaneous drop of the commercial system. However, algorithms for preventing the expansion of blackouts in small power systems are not considered. Further, Patent Document 2 relates to management of consumers having distributed power sources in a small-scale power system, and performs economic power accommodation by combining consumers that meet predetermined conditions. However, the algorithm for preventing the power outage expansion in the small power system is still not taken into consideration.

  On the other hand, when there is a partial power system that is interconnected by a connection line in the power company's main power system, the generator in the partial power system is cut off or loaded in an emergency when the connection line is cut off due to a connection line accident, etc. Stabilizers (SSC: System Stabilizing Controller or TSC: Transient Stability Controller) that can be cut off urgently and prevent all power outages have been put into practical use.

However, in such a system, it is necessary to monitor information on many generators and loads through a transmission system, so many transmission systems and terminals, complicated on-line computation for monitoring, many control terminals, A circuit breaker is required. For this reason, it is not efficient to apply to a small power system of group management type.
JP 2004-15883 A JP 2004-15882 A

  Therefore, the applicant of the present invention detects a small-scale power system (microgrid) that is linked to a commercial system and several small-scale power systems (child microgrids) when a commercial power failure occurs. However, it was considered that the pattern of the interconnection current flow between the child microgrids before the power outage, for example, cut off the smallest interconnection line and survive the child microgrids.

  This method is effective as an efficient control method for preventing all blackouts, but requires constant centralized monitoring of all interconnected power flow. In addition, a computer, a transmission system, and a monitoring / control terminal for controlling when an accident occurs are also required. Further, when it is desired to artificially make the child microgrids into independent systems, logic for suppressing power fluctuation and frequency fluctuation after separation and control using the same are required.

  It is an object of the present invention to safely and independently form a child microgrid with a simple algorithm even when a power supply failure such as a power failure occurs on the main commercial system side and when it is desired to artificially make the child microgrid independent. It is to provide a power grid interconnection system having a function.

The power grid interconnection system of the present invention includes a backbone power grid and a small scale power grid that is linked to the backbone power grid by a trunk grid line, and the small scale power grid includes a power load and the power load. A plurality of small-scale power systems each having a power supply device for each of the plurality of small-scale power systems connected in series with each other through a slave interconnection line , and the small-scale power systems located at both ends of the plurality of small-scale power systems connected in series A scale power system is a power system interconnection system that is connected to a connection point with the backbone interconnection line, and is provided in each of the child small-scale power systems, and the magnitude of the tidal current of the child interconnection line A reference range in which the supply and demand imbalance amount in the corresponding small-scale power system is determined from the power flow of these sub-interconnection lines, and this supply-demand imbalance amount is determined by the frequency tolerance of the corresponding small-scale power system To be within Characterized by comprising a monitoring control means for controlling either or both of the power load and the power generation amount of the power supply of the child small power system.

  Further, in the power grid interconnection system of the present invention, the monitoring control means has a child small-scale power system corresponding so that the supply and demand imbalance amount is within a reference range determined by the frequency tolerance of the corresponding child small-scale power system. You may comprise so that either or both of the said electric power load amount and the electric power generation amount of the said power supply device may be controlled.

  Further, in the power grid interconnection system of the present invention, a secondary battery that can be charged / discharged is used as a part of the power supply device, and the monitoring control means is a secondary battery when the supply / demand imbalance exceeds the power generation amount. The charging control may be performed, and when the load is exceeded, the secondary battery may be controlled to be discharged.

  Further, in the power grid interconnection system of the present invention, a secondary battery that can be charged / discharged is used as a part of the power supply device, and the monitoring control means is connected to a child interconnection line with another child small-scale power grid. It has a function to monitor the presence or absence of interruption, and when the interruption of the corresponding child interconnection line is detected, if the supply and demand imbalance at that time exceeds the power generation amount, charge control of the secondary battery is performed. You may comprise so that a secondary battery may carry out discharge control.

  Further, in the power grid interconnection system of the present invention, as a power load, a load that can be cut off urgently when the load amount is exceeded is provided as a part of the power load, and as a power supply device, a generator that can be cut off urgently when the amount of power generation is exceeded The monitoring control means has a function of monitoring the presence / absence of interruption of the child interconnection line with other child small-scale electric power systems, and when the interruption of the corresponding child interconnection line is detected, the supply and demand imbalance at that time is detected. However, it may be configured to have an emergency shut-off function that shuts off the emergency shut-off power generation facility when the power generation amount is exceeded, and emergency shuts off the emergency shut-off load when the load amount is exceeded.

  Further, in the power grid interconnection system of the present invention, it is configured to be connectable to a plurality of child small-scale power systems constituting the small-scale power system, and according to the supply and demand imbalance of the connected child small-scale power systems. The power generation amount may be controlled so as to have a common power supply device.

  Further, in the power grid interconnection system of the present invention, a chargeable / dischargeable secondary battery is used for a part of the shared power supply, and this secondary battery is unbalanced between the supply and demand of the connected small-scale power grid. Depending on the case, the charge / discharge control may be performed.

  Furthermore, in the power grid interconnection system of the present invention, it is configured to be connectable to a plurality of child small-scale power systems constituting the small-scale power system, and according to the supply and demand imbalance of the connected child small-scale power systems. It may be configured to have a common secondary battery that is charged and discharged.

  According to the present invention, a power supply failure such as a power failure has occurred on the main commercial grid side, so when artificially subdividing a child microgrid, a simple algorithm does not cause significant fluctuations in voltage and frequency. The child microgrid can be safely organized independently.

  Hereinafter, an embodiment of a power grid interconnection system according to the present invention will be described in detail with reference to the drawings.

 First, an electric power system to which the present invention is applied will be described with reference to FIG. In FIG. 1, reference numeral 2 denotes a main power system, which is a large-scale commercial system provided by an electric power company. The main power system 2 is connected to the small-scale power system 1 by a main power line 3 having a main power line breaker 4. The small-scale power system (hereinafter referred to as a microgrid) 1 has a plurality (in the example of the figure, 5) of child small-scale power systems (hereinafter referred to as child microgrids) 5. Each of the plurality of child microgrids 5 has a distributed power source as shown in the figure, and is connected in series by a child interconnection line 6 having a child interconnection line breaker 7. Of the plurality of child microgrids 5 connected in series, the child microgrids 5 positioned at both ends are connected to the main interconnection line 3 by child interconnection lines 6 each having a child interconnection line breaker 7. Connected to a point.

  Here, the above-described microgrid 1 is a small-scale power system connected to the main power system 2 that is the power system of the power company via the interconnection line 3 and should be referred to as a child as described above. It is constituted by several small-scale power systems, that is, child microgrids 5. As described above, each child microgrid 5 has a small-scale generator called a distributed power source, and the consumer load in the microgrid 1 includes a main power system 2 of an interconnected power company and a microgrid 1. Power is supplied by the distributed power source.

  The microgrid 1 is composed of five child microgrids 5 as described above. These five child microgrids 5 are referred to as a child microgrid 51, a child microgrid 52, a child microgrid 53, a child microgrid 54, and a child microgrid 55. Each child microgrid 51 to 55 is connected by a child interconnection line 6. Among these child interconnection lines 6, a child interconnection line 601 connecting the interconnection line 3 and the child microgrid 51, a child interconnection line 612 connecting the child microgrid 51 and the child microgrid 52, The child interconnection line linking the child microgrid 54 is 624, the child interconnection line linking the child microgrid 54 and the child microgrid 55 is 645, the child interconnection line linking the child microgrid 55 and the child microgrid 53 is 653, and the child A child interconnection line connecting the microgrid 53 and the interconnection line 3 is designated as 603. Moreover, the circuit breaker 7 which turns on and off each child interconnection line 6 is used as a child interconnection line breaker. Then, the child interconnection line breaker provided in the child interconnection line 601 is designated as 701. Similarly, the child interconnection line breaker provided in the child interconnection line 612 is provided in 712 and the child interconnection line 624. 724, the child connection line breaker provided in the child connection line 645, 745, the child connection line breaker provided in the child connection line 653, 753, the child connection line breaker A child interconnection line breaker provided on the line 603 is designated as 703.

  In the above configuration, when a power failure occurs in the main power system 2 by an electric power company or the like, the voltage of the main power system 2 becomes zero, and the current flows in the reverse direction from the small power system 1 to the main power system 2 as it is. (Called reverse tide). In order to prevent this reverse tide, the interconnection breaker 4 is interrupted. The interconnection breaker 4 is normally cut off by the operation of a protection relay (not shown) according to the voltage of the main power system 2 and the direction of power flow.

  If the grid breaker 4 is left after being shut off, the frequency and voltage in the micro grid 1 suddenly change, and a voltage relay or frequency relay (not shown) installed in the micro grid 1 operates in a chained manner, resulting in a total power failure. There are many cases.

  In this case, for example, two child interconnection lines 6 satisfying the conditions described later are selected from the respective child interconnection lines 601, 612, 624, 645, 653, and 603 in the microgrid 1, and these are selected. The child interconnection line breaker 7 provided on the two child interconnection lines 6 may be interrupted. As a result, the child microgrid 5 included between the two cut-off points is cut off to prevent a complete power failure.

  For example, when the child interconnection breaker 724 between the child microgrid 52 and the child microgrid 54 and the child interconnection breaker 745 between the child microgrid 54 and the child microgrid 55 are cut off, the child included between the breakpoints By separating the microgrid 54 and preventing the power failure, the power failure of the microgrid 1 due to the power failure is avoided.

  The selection conditions for the above-described interruption points are determined based on the tidal current values in the respective child interconnection lines 601, 612, 624, 645, 653, 603. Accordingly, each child interconnection line 601, 612, 624, 645, 653, 603 is provided with a tidal current detection device (not shown) in order to detect the magnitude of the tidal current of the corresponding child interconnection line.

  In order to make a determination based on the power flow value in this way, it is necessary to periodically capture and record the power flow of the interconnection line 3 and each child interconnection line 6 before the occurrence of the power failure in the central control system. Further, in order to grasp the power demand of each child microgrid 5, the output of the distributed power source and the like are also input. Then, from the recorded information on the latest power flow before the occurrence of the power outage of the interconnection line 3 and each of the child interconnection lines 6, the appropriate child interconnection line 6 is selected to be cut off in order to prevent all power outages.

  For this reason, based on the tidal current value in each of the child interconnection lines 601, 612, 624, 645, 653, and 603, a combination of two child interconnection lines 6 appropriate as a cutoff target is selected, and the two selected child elements are selected. The child interconnection line breaker 7 provided in the interconnection line 6 is interrupted, and the child microgrid 5 included between the two interruption points is disconnected, thereby preventing a total power failure. In other words, each child interconnection line 6 is selected from a combination of two child interconnection lines 6 having a small cutoff current. This is because the smaller the cut-off power flow, the smaller the frequency and voltage fluctuation of the cut-off child microgrid 5 and the greater the probability that a power failure can be prevented.

  The above method was conceived by the applicant of the present application and is effective as an efficient control method for preventing all blackouts, but it is used for continuous centralized monitoring of all interconnected power flow and for control in the event of an accident. A computer, transmission system and monitoring / control terminal are required. In addition, when it is desired to artificially form the child microgrid 5 as an independent system, logic for suppressing power fluctuation and frequency fluctuation after separation and control using the same are required. That is, in order to select an appropriate child microgrid interconnection breaker 7 to be interrupted, data collection means and interruption interconnection line calculation means are required, and these allow periodic data collection and calculation. There is a need to do.

  However, even if any child microgrid interconnection breaker 7 in the microgrid 1 is cut off, the frequency and voltage in the child microgrid 5 after being cut off are not changed suddenly, and the system can be safely independent. If possible, it is possible to greatly simplify the functions of the data collection means and the disconnection interconnection line calculation means.

  For example, as shown in FIG. 2, when all the inter-microgrid interconnection breakers 7 of the microgrid 1 are cut off in a state where the interconnection breaker 4 is cut off (indicated by x), in advance, If any child microgrid interconnection circuit breaker 7 is cut off, all the child shown in FIG. The microgrid 5 can be safely independent.

  This is the same even when the inter-microgrid interconnection breakers 701 and 703 connected to the interconnection line 3 of the small-scale power system 1 are cut off as shown in FIG. That is, as shown in FIG. 2, even if any of the child microgrid interconnection breakers 7 of any individual child microgrid 5 is shut off in advance, the child microgrid 5 after being shut off can be safely and independently systematized. If controlled so as to be possible, even if the two inter-microgrid interconnection breakers 701 and 703 close to the interconnection breaker 4 are cut off, all the cut off child micro-grids 51, 52, 53, 54, and 55 can be safely grouped independently.

  Further, as shown in FIG. 4, when the inter-child microgrid interconnection breakers 712 and 753 between the child microgrids 51 and 52 and between the child microgrids 55 and 53 are shut off, for example, the child microgrids 52 and 54 are cut off. , 55 and the child microgrids 51, 53 are independent systems. Also in this case, as described above, even if the interconnection breaker 7 between any individual child microgrids 5 is interrupted in advance, all the child microgrids 5 after the interruption can be safely independent. If the control is performed as possible, the two independent systems described in FIG. 4 can be safely made into independent systems.

  Furthermore, even if only the interconnection breaker 4 is cut off as shown in FIG. 5 (electrically equivalent to FIG. 3), any child microgrid interconnection breaker 7 is cut off in advance, If the child microgrid 5 after the interruption is controlled so that it can be safely and independently organized, a data collection means for selecting an appropriate child microgrid interconnection breaker 7 to be interrupted, Therefore, the disconnection interconnection calculation means becomes unnecessary, and periodic data collection and calculation control become unnecessary.

  Therefore, the present invention controls each child microgrid 5 in a state where it is not necessary to interrupt the child interconnection line breaker 7 on the microgrid 1 side at the time of interconnection interruption. This will be specifically described below.

  FIG. 6 is a conceptual diagram showing one child microgrid in the microgrid 1. The child microgrids (for example, described as 54 but the same for other child microgrids) have various power loads 27 and power supply devices 26 for these power loads 27, respectively. A monitoring control system 30 that monitors and controls the supply and demand state of the vehicle. This monitoring control system 30 is provided individually for each child microgrid 5. Moreover, the power supply device 26 is comprised by various generators so that it may mention later.

  The child microgrid 54 is connected to other microgrid interconnection lines (in this example, 624 and 645), and these interconnection lines are provided with child microgrid interconnection line breakers 724 and 745. It has been. These interconnection lines 624 and 645 are each provided with a tidal current detection device (not shown) in order to measure a tidal current with another child microgrid. Then, the tidal current values P24 and P45 detected by them are input to the monitoring control system 30.

  The tidal current detection device has a transformer for measuring instruments such as CT and PT, and the tidal current is extracted by extracting the electric quantity such as voltage and current at the measuring point by means of CT and PT installed on the corresponding interconnection line. Find the value and its direction.

  As described above, the supervisory control system 30 is provided in each child microgrid 5, and the sizes of the power flows P24 and P45 of the child interconnection lines (624 and 645 in this example) with the other child microgrids 5 and Monitor direction. Then, the supply and demand imbalance amount in the corresponding child microgrid (54 in this example) is obtained from the power flows P24 and P45 of these child interconnection lines 624 and 645. Then, either or both of the load amount of the power load 27 and the power generation amount of the power supply device 26 corresponding to the child microgrid 54 are controlled so that the supply and demand imbalance amount becomes zero as much as possible.

  That is, the child microgrid 54 shown in FIG. 6 is connected to the other child microgrid 5 by two interconnection lines 624 and 645 between the child microgrids. The tidal currents flowing in the two inter-micro-grid interconnection lines 624 and 645 are referred to as one inter-micro-microgrid interconnection line current P24 and the other inter-micro-grid interconnection line current P45. In order for the child microgrid 54 to be safely independent after the breaker 724, 745 between the child microgrids shown in the figure is cut off, the supply and demand balance before the breakage in the child microgrid 54 must be balanced. is required. If the supply and demand balance is not well balanced, frequency and voltage fluctuations will occur as described above, and it will not be possible to safely establish an independent system.

  The supply-demand balance refers to the balance between the total amount of the load 27 in the child microgrid before the interruption and the total amount of the power supply device 26 in the child microgrid. The difference between the total amount of the power load 27 in the child microgrid before the interruption and the total amount of power generated by the power supply facility 26 in the child microgrid is the sum of the power flows P24 and P45 flowing through the child microgrid interconnection lines 624 and 645. In FIG. 6, the direction of the tide P24 and the tide P45 is positive in the direction of entering the child microgrid 54. Therefore, if the total amount of the power load 27 in the child microgrid is larger than the total power generation amount of the power supply device 26 in the child microgrid, the sum of the power flow P24 and the power flow P45 is positive, and vice versa.

  Therefore, the supply and demand imbalance amount can be calculated by measuring the interconnection currents P24 and P45 between the child microgrids and taking the sum thereof. Therefore, the child microgrid monitoring and control system 30 performs monitoring and control for making the sum of the inter-child microgrid interconnection currents P24 and P45 as zero as possible. Therefore, the power flow P24 and P45 between the child microgrids is always measured and the sum thereof is calculated. If the calculated value is positive, the output for increasing the output of the power supply device 26 in the child microgrid is output. An increase command is issued, and if the calculated value is negative, an output decrease command for reducing the output of the power supply device 26 in the child microgrid is issued.

  Usually, the power supply device 26 in the child microgrid 5 has a plurality of small generators (also referred to as distributed power supplies), and is intended for base load 26A, load follow-up 26B, and interconnected line constant control in consideration of economy. 26C for fine adjustment.

  FIG. 7 shows the total amount of the power load 27 in the child microgrid for one day as a demand curve 27R, and shows the output sharing by the base load generator 26A, the load following generator 26B, and the fine adjustment generator 27C. . The base load generator 26A keeps the most efficient output in consideration of economy and does not change the output so much. The load following generator 26B performs a relatively slow load following power generation output in consideration of demand prediction and actual load fluctuations. The fine-tuning generator 26C is a relatively small generator with good responsiveness, and absorbs a short-time interconnection power flow fluctuation.

  FIG. 8 is a schematic sequence diagram for performing supply and demand balance control by making the sum of the interconnection flow between the child microgrids in the child microgrid monitoring control system 30 shown in FIG. 6 zero. The control system 30 collects the tidal flow rates of the inter-microgrid interconnection line flows P24 and P45 by the interconnection line flow rate collecting means 37 (step 801). The supply / demand imbalance amount calculation means 38 calculates the sum of the inter-child microgrid interconnection currents P24 and P45 (step 802). Then, it is determined whether the sum of the calculated inter-child microgrid interconnection line flows, that is, the supply and demand imbalance amount is positive or negative (step 803). As a result, if the supply and demand imbalance amount is positive (step 803: YES), an output increase command for the fine adjustment generator 26C is issued (step 804). If the supply and demand imbalance amount is negative (step 803: NO), an output reduction command for the fine adjustment generator 26C is issued (step 805).

  In this way, in each child microgrid 5, the power generation amount of the power supply device 26 is always such that the unbalance between the total amount of the internal power load 27 and the total power generation amount of the internal power supply device 26, that is, the supply / demand imbalance amount becomes zero as much as possible. Is controlling. For this reason, the supply and demand imbalance in each child microgrid is always almost zero. Even if the line breaker 4 is shut off due to an accident on the main grid 2 side, there is almost no effect on the microgrid 1 side. Even if the interconnection line breaker 7 is cut off, the voltage and frequency on the microgrid 1 side do not fluctuate greatly to cause a complete power failure.

  FIG. 9 shows the total amount of power load 27 in the child microgrid for one day as a demand curve 27R, the output sharing state of the base load generator 26A and the load following generator 26B, and the fine adjustment power generation shown in FIG. The supply / demand balance control state by the secondary battery 26D is shown instead of the machine 26C.

  Also in this case, the base load generator 26A holds the most efficient output in consideration of economy and does not change the output so much. The load following generator 26B also performs a relatively slow load following power generation output in consideration of demand prediction and actual load fluctuations. Since the secondary battery 26D can perform inverter control of charging and discharging, the responsiveness is very fast and absorbs a short-time fluctuation in the interconnection power flow.

  FIG. 10 shows a schematic sequence for explaining the control in the child microgrid monitoring control system 30 when the above-described secondary battery 26D is used. Also in this case, the control system 30 collects the tidal flow rates of the inter-microgrid interconnecting line flows P24 and P45 by the interconnecting line tidal flow collecting means 37 (step 1001). The supply / demand imbalance amount calculation means 38 calculates the sum of the inter-child microgrid interconnection line flows P24 and P45 (step 1002). Then, it is determined whether the sum of the calculated power flows between the child microgrids, that is, the supply / demand imbalance amount is positive or negative (step 1003). As a result, if the supply and demand imbalance amount is positive (excess load amount) (step 1003: YES), a discharge command is output to the secondary battery 26D (step 1004). If the supply and demand imbalance amount is negative (power generation excess) (step 1003: NO), a charge command is output to the secondary battery 26D (step 1005).

  As described above, according to the present embodiment, the supply and demand imbalance amount indicated by the sum of the inter-child microgrid interconnection lines can be reduced as much as possible (almost zero). Even if it is cut off, the cut off child microgrid 5 can be safely independent.

  Next, another embodiment will be described. FIG. 11 shows an example of frequency fluctuation in the interrupted child microgrid 5 when any of the child microgrid interconnection breakers 7 is interrupted. In this example, it is assumed that the interrupted child microgrid 5 includes a generator that is in a governor-free operation (frequency control by the generator).

  Here, in the child microgrid 5 in which the child microgrid interconnection breaker 7 is cut off, when the power generation amount of the power supply device 26 before the interruption exceeds the load amount of the power load 27, that is, the supply and demand imbalance amount < When 0, the frequency rises after cutoff. On the other hand, when the supply / demand imbalance amount> 0, the frequency drops after the cutoff. The degree of frequency rise and fall depends on the magnitude of the absolute value of supply and demand imbalance. The greater the absolute value of the supply / demand imbalance, the greater the frequency rises and falls.

  In such a child microgrid 5, a frequency increase limit value 40 and a frequency decrease limit value 41 are set. These limit values 40 and 41 are determined by the characteristics of the power load 27, the characteristics of the generator in the power supply device 26, the set value of the frequency relay, and the like. The frequency increase limit value 40 is a limit value on the frequency increase side, and if the frequency of the child microgrid 5 exceeds the frequency increase limit value 40 for a certain time or more, the child microgrid 5 cannot operate stably and a power failure may occur. Many. The frequency decrease limit value 41 is a limit value on the frequency decrease side, and if the frequency of the child microgrid 5 falls below the frequency decrease limit value 41 for a certain time or more, the child microgrid 5 cannot operate stably in this case as well. In many cases.

  The degree of frequency increase and frequency decrease depends on the level of supply and demand imbalance. For this reason, the electric power supply / demand unbalance amount is always within a predetermined range so that the frequency of the child microgrid 5 does not exceed the frequency increase limit value 40 or the frequency decrease limit value 41 due to the interruption of the interconnection breaker 7 between the child microgrids. Need to keep inside.

  The limit value of supply and demand unbalance amount exceeding the frequency increase limit value 40 is the frequency increase side limit supply and demand unbalance amount, and the limit value of supply and demand unbalance amount lower than the frequency decrease limit value 41 is the frequency decrease side limit supply and demand Called the unbalance amount. In this embodiment, the child microgrid monitoring control system 30 does not exceed the frequency increase limit value 40 or the frequency decrease limit value 41 even if the child microgrid interconnection breaker 7 is cut off. Thus, the power supply / demand imbalance amount is controlled. The schematic sequence will be described with reference to FIG.

  In this case as well, the control system 30 collects the tidal flow rates of the inter-micro-grid interconnection line flows P24 and P45 by the interconnection line tidal flow collecting means 37 (step 1201). The supply and demand imbalance amount calculation means 38 calculates the sum of the inter-sub-microgrid interconnection line flows P24 and P45 (step 1202). Then, it is determined whether the sum of the calculated inter-child microgrid grid line flows, that is, the supply / demand imbalance amount is larger than the frequency lowering side limit supply / demand unbalance amount (step 1203). As a result, if it is larger than the frequency decreasing side limit supply and demand imbalance amount (step 1203: YES), an output increase command for the fine adjustment generator 26C is issued (step 1204). On the other hand, if it is smaller than the frequency decrease side limit supply / demand unbalance amount (step 1203: NO), it is determined whether the supply / demand unbalance amount is larger than the frequency increase side limit supply / demand unbalance amount (step 1205). As a result, if it is larger than the frequency increase limit supply / demand imbalance amount (step 1205: YES), an output reduction command for the fine adjustment generator 26C is issued (step 1205).

  That is, in this embodiment, the magnitude of the tidal current of the child interconnection line 6 is monitored, the supply and demand imbalance amount in the corresponding child microgrid 5 is obtained from the tidal current of the child interconnection line 6, and this supply and demand imbalance is obtained. The power generation amount of the power supply device 26 of the corresponding child microgrid 5 is controlled so that the amount falls within a reference range determined by the frequency tolerance of the corresponding child microgrid 5.

  FIG. 13 is a schematic sequence diagram in the child microgrid monitoring control system 30 when the secondary battery 26D is used instead of the fine adjustment generator 26C. The processing of steps 1301 to 1303 and step 1305 in this schematic sequence is the same as the processing of steps 1201 to 1203 and step 1205 in FIG. In step 1304, it is necessary to increase the frequency from the previous determination result (1303: YES), and control is performed to discharge the secondary battery 26D. On the other hand, in step 1306, it is necessary to lower the frequency from the previous determination result (1305: YES), and control is performed to charge the secondary battery 26D.

  FIG. 14 is a schematic sequence diagram of the control system 30 in the child microgrid 5 in which the fine adjustment generator 26 </ b> C and the secondary battery 26 </ b> D are mixed as the power supply device 26. The processing of steps 1401 to 1403 and 1405 in this schematic sequence is the same as the processing of steps 1201 to 1203 and step 1205 in FIG. In step 1403, the supply / demand imbalance amount is compared with the frequency lowering side limit supply / demand imbalance amount. That is, the determination of | supply / demand unbalance amount |> | frequency lowering side limit supply / demand unbalance amount | is made. The machine 26C is assigned (step 1413). That is, the secondary battery 26D discharge command (step 1423) and the fine adjustment generator 26C output increase command (step 1433). Usually, the output increase command of the fine adjustment generator 26C is issued at a slow cycle, and the discharge command of the secondary battery 26D is issued at a fast cycle.

  On the other hand, if the decision result in the step 1403 is NO, in a step 1405, the supply / demand unbalance amount is compared with the frequency increasing side limit supply / demand unbalance amount. That is, the determination of | supply / demand imbalance amount |> | frequency increase limit supply / demand imbalance amount | is made, and in the case of YES, the secondary battery 26D and the fine adjustment power generation by the distribution function 44 for the excess supply / demand imbalance increase side The machine 26C is assigned (step 1415). That is, a charge command for the secondary battery 26D (step 1425) and an output decrease command for the fine adjustment generator 26C are issued (step 1435). Also in this case, an output decrease command for the fine adjustment generator 26C is issued at a slow cycle, and a charge command for the secondary battery 26D is issued at a fast cycle.

  Thus, according to the present embodiment, the reference range determined by the frequency tolerance of the child microgrid 5 is provided, and the supply and demand imbalance amount indicated by the interconnection flow between the child microgrids 5 does not exceed the reference range. Since it controls, even if it interrupts | blocks arbitrary arbitrary connection lines 6 between child microgrids, the interrupted child microgrid 5 can be safely made into an independent system. Further, since the control is performed so that the supply / demand imbalance amount is zero as much as possible according to the embodiment, the control is performed so as not to exceed the reference range.

  In this embodiment, the control when the interruption of the corresponding child interconnection line 6 is detected has been described. However, the present invention is not limited to such a case, and the supply / demand imbalance in the child microgrid 5 always falls within the reference range. You may control so that it may not be exceeded.

  FIG. 15 is a schematic sequence diagram when the capacity of the secondary battery 26D used as a part of the power supply device 26 of the child microgrid 5 has a sufficient capacity, or when there is a spare secondary battery 26D. The schematic sequence of FIG. 15 differs from the schematic sequence of FIG. 14 described above only in the judgment criteria in step 1503 and step 1505, and the processing in the other steps is the same as in FIG. As described above, the secondary battery 26D can be instantaneously charged and discharged by inverter control. Therefore, immediately after the breaker 7 between the micro-microgrids is cut off, the secondary battery 26D having a sufficient capacity can be charged and discharged urgently. In other words, the range of the frequency decrease side limit supply and demand imbalance amount and the frequency increase side limit supply and demand unbalance amount can be expanded by the amount of the charge margin and discharge margin amount of the secondary battery 26D.

  Therefore, the determination formula of step 1503 is | supply / demand imbalance amount |> | frequency lowering side limit supply / demand unbalance amount + secondary battery charge margin amount |, and the determination formula of step 1505 is | supply / demand imbalance amount |> | Frequency rising limit supply and demand imbalance amount + secondary battery discharge margin amount | If the determination result in step 1503 is YES, the supply / demand unbalance descending excess with the added secondary battery charging margin is distributed by the distribution function 44, and the secondary battery 26D discharge command and the fine adjustment generator Command 35 to increase output. In this case, the secondary battery 26D is given a discharge command for a shared amount including the secondary battery charging margin amount at a fast cycle. Further, an output increase command is issued at a slow cycle to the fine adjustment generator 26C.

  On the other hand, if the determination result in step 1503 is NO, the determination is made in step 1505. If the determination result is YES, the distribution function 44 uses the distribution function 44 to determine the supply / demand imbalance increase excess with the secondary battery discharge margin added. The secondary battery 26D charge command and the fine adjustment generator 26C output increase command are issued. In this case, the secondary battery 26D is instructed to charge the charge amount including the secondary battery discharge margin amount at a fast cycle. Further, an output reduction command is issued at a slow cycle to the fine adjustment generator 26C.

  Thus, according to the present embodiment, since the secondary battery 26 is provided with a charge / discharge allowance, it is possible to perform control with a further allowance.

  FIG. 16 is a diagram showing the frequency fluctuation when the generator breakage or the load breakage is performed after the breaker 7 between the micro-microgrids is cut off and detected. When the supply and demand state in the microgrid 5 before the inter-child microgrid interconnection breaker 7 is cut off is a supply-demand imbalance amount <0, that is, when the power generation amount is excessive, the frequency increases after the breaker 7 is cut off. On the contrary, when the supply and demand imbalance amount> 0, that is, when the load amount is excessive, the frequency decreases after the breaker 7 is cut off. Therefore, when the supply / demand unbalance amount <0, the frequency is recovered by cutting off an appropriate amount of power generation, and when the supply / demand unbalance amount> 0, the frequency is recovered by cutting off an appropriate load amount.

  In the example of FIG. 16, when the supply and demand imbalance amount <0, the frequency increase limit value 40 is exceeded without the generator being cut off, whereas the frequency is within the frequency increase limit value 40 with the generator being cut off. Further, when the supply and demand imbalance amount> 0, the frequency falls below the frequency drop limit value 41 without load interruption, while the frequency falls within the frequency drop limit value 41 with load interruption.

  Thus, with the generator cutoff function and the load cutoff function, even if the absolute value of the supply and demand imbalance increases, the system can be stably independent without exceeding the frequency increase limit value 40 or the frequency decrease limit value 41. Is possible.

  FIG. 17 shows an emergency generator / load cutoff function (hereinafter referred to as an emergency cutoff function) 48 in the child microgrid 5. This emergency cutoff function 48 is realized as one function in the child microgrid monitoring control system 30 shown in FIG. The emergency shutoff function 48 is always connected to the power line 26 between the power generator 26, the load 27, and the interconnecting line 6, for example, in a cycle of 2 to 3 minutes, the power flow value between the child microgrids, the load in the child microgrid, and the child microgrid. An input unit 500 is provided for inputting the amount of generated power. When the child microgrid interconnection breaker 7 is cut off, the child microgrid interconnection line breaking signal is sent to the child microgrid interconnection line breaking detection means 501, and the child microgrid 5 becomes a single system. Is detected.

  The frequency in the child microgrid 5 that becomes a single system rises or falls according to the supply and demand imbalance state. If the power supply device 26 in the child microgrid 5 has the secondary battery 26D, the emergency battery control means 502 performs charge or discharge control according to the supply / demand imbalance state as described above. When the capacity of the secondary battery 26 is small, the frequency fluctuation cannot be suppressed and the frequency tends to exceed the limit value 40 or 41.

  At this time, it is possible to determine whether the current state is an excess load amount or an excess power generation amount from the tidal current value, the load amount, and the power generation amount input by the input unit 500. When the load amount is exceeded, the emergency load cutoff means 503 urgently cuts off the load on the interconnection line between the child microgrids before the cutoff and the load. When the amount of power generation is excessive, the emergency power generator shutoff means 504 emergency shuts off the power generator for the power line connected between the child microgrids before the power shutoff.

  In other words, in the present embodiment, a part of the power load 27 that can be urgently cut off when the load exceeds the load is provided, and a part of the power supply device 26 is provided with a power generation facility that can be urgently cut off when the amount of power generation is exceeded. The supervisory control means realized by the supervisory control system 30 has a function of monitoring the presence / absence of the interruption of the child interconnection breaker 7 in the child interconnection line 6 with the other child microgrid 5, and the corresponding child interconnection line 6 is detected, if the supply and demand imbalance state at that time is large in the amount of power generation, the generator capable of emergency shutoff in the power supply device 26 is shut off, and if the load amount is large, Loads that can be cut off urgently are cut off urgently.

  As described above, according to the present embodiment, in addition to charge / discharge control of the secondary battery 26D after the child microgrid 5 is interrupted, more reliable control is performed by performing emergency load interruption and emergency generator interruption. Is possible.

  Next, the embodiment shown in FIG. 18 will be described. In this embodiment, the basic configuration of the microgrid 1 is the same as that shown in FIG. 1, but a common power supply device 56 is provided for a plurality of child microgrids 5 constituting the microgrid 1. This shared power supply device 56 is configured to be connectable by each child microgrid 5 and the circuit breaker 8, and is configured such that the power generation amount is controlled in accordance with the supply / demand unbalance amount in the connected child microgrid 5. . As the shared power supply device 56, a fine adjustment generator 56C and a secondary battery 56D capable of charge / discharge control are used.

  Here, in each of the above-described embodiments, for each child microgrid 5 constituting the microgrid 1, each child microgrid interconnection line flow is set to zero as much as possible, or within a predetermined range. The secondary battery 26D of the power supply device 26 and the fine adjustment generator 26C are controlled. However, in order to control the power flow 27 in the child microgrid 5 so that the power flow 49 between the child microgrids is zero as much as possible or within a predetermined range at any sudden change in the load amount. Therefore, it is necessary to increase the capacity of the fine adjustment generator 26 </ b> C and the secondary battery 26 </ b> D in the power supply device 26 in each child microgrid 5 by assuming a maximum load amount sudden change. Or the operation which ensured the reserve for the time of the maximum load amount sudden change of the generator 26C for fine adjustment and the secondary battery 26D is needed. In addition, if the fine adjustment generator 26C and the secondary battery 26D are stopped for maintenance or the occurrence of a failure is taken into consideration, the reserve fine adjustment generator 26C and the secondary battery 26D are required.

  However, in general, it is rare that a sudden change in the load amount occurs simultaneously in each child microgrid 5 of the microgrid 1 or that the fine adjustment generator 26C and the secondary battery 26D fail simultaneously. Further, the timing for stopping the fine adjustment generator 26C and the secondary battery 26D for maintenance can be shifted for each child microgrid 5. Considering these, the capacity of the fine adjustment generator 26C and the secondary battery 26D is increased assuming that the maximum load amount suddenly changes for each child microgrid 5, or the fine adjustment generator 26C and the secondary battery 26D Rather than operating with a reserve capacity for the maximum load sudden change, or installing a spare fine-tuning generator 26C or secondary battery 26D, fine-tuning power generation that can be shared by each child microgrid 5 It may be more economical to install a machine or a secondary battery and control the power for the necessary child microgrid 5.

  Therefore, as shown in FIG. 18, for example, a shared power supply device 56 is provided for the microgrids 51, 54, and 55 among the child microgrids 5 constituting the microgrid 1. As the shared power supply device 56, a shared secondary battery 56D and a shared fine tuning generator 56C are installed.

  In the example of FIG. 18, the shared secondary battery 56 </ b> D and the shared fine adjustment generator 56 </ b> C are connected to the child microgrid 51 via the circuit breaker 8. The other connectable child microgrids 54 and 55 are not connected to the shared power supply device 56 because the circuit breaker 8 is open (indicated by X in the drawing).

  FIG. 19 shows a schematic sequence realized by the control system 30 of the child microgrid 51 that can be connected to the shared power supply device 56. The processing of steps 1901, 1902 and 1903 in this schematic sequence is the same as the processing of steps 801, 802 and 803 in FIG. That is, the tidal flow of the interconnection line flow between the child microgrids (in this case, P01 and P12) is collected by the interconnection tidal flow collecting means 37 (step 1901). The supply / demand imbalance amount calculation means 38 calculates the sum of the inter-child microgrid interconnection currents P01 and P12 (step 1902). Then, it is determined whether the sum of the calculated power flows of the interconnection lines between the child microgrids, that is, the supply and demand imbalance amount is positive or negative (step 1903).

  As a result, when the supply / demand imbalance amount> 0, the supply / demand imbalance (power shortage) is assigned to each power supply device by the distribution function 44 (1904). That is, first, a discharge command (step 1906) for the secondary battery 26D and the output of the fine adjustment generator 26C are assigned to the secondary battery 26D and the fine adjustment generator 26C of the power supply device 26 in the child microgrid 51. An increase command (step 1907) is issued. If the supply power is still insufficient due to these assignments, the shared power supply 56 is made to share the shortage. That is, a discharge command (step 1907) of the shared secondary battery 56D and an output increase command (step 1908) of the shared fine adjustment generator 56C are issued.

  On the other hand, when the supply / demand imbalance amount <0, the supply / demand imbalance (power surplus) is allocated to each power supply device by the distribution function 44 (step 1909). That is, first, a charge command (step 1910) for the secondary battery 26D to be shared by the secondary battery 26D and the fine adjustment generator 26C of the power supply device 26 in the child microgrid 51, and the output of the fine adjustment generator 26C. A decrease command (step 1911) is issued. In addition, even if these shares are shared, if the supply power is excessive, the excess is shared by the shared power supply 56. That is, a charge command for the shared secondary battery 56D (step 1912) and an output reduction command for the common fine adjustment generator 56C (step 1913) are issued.

  As described above, according to the present embodiment, the shared secondary battery 56D and the shared fine-tuning generator 56C are provided, and these charge / discharge commands and generator output increase / decrease commands are executed, thereby making it more economical. Thus, it is possible to control the supply and demand imbalance amount to be as zero as possible.

  In the above embodiment, the supply and demand imbalance amount is compared with 0, and the common power supply device 56 is controlled so that the supply and demand imbalance amount becomes zero as much as possible. However, in the embodiment described with reference to FIG. As described above, the common power supply device 56 may be controlled so that the supply and demand imbalance amount falls within a predetermined reference range.

  That is, in the embodiment of FIG. 14, in step 1403, the supply / demand imbalance amount is compared with the frequency-decreasing limit supply-demand imbalance amount, and | demand-supply imbalance amount |> | frequency-decreasing limit supply-demand imbalance amount | In the case of YES (in the case of power shortage), the excess of the supply / demand imbalance descending side is shared by the distribution function 44 to the secondary battery 26D and the fine adjustment generator 26C (step 1413). That is, although the discharge command (step 1423) of the secondary battery 26D and the output increase command (step 1433) of the fine adjustment generator 26C are issued, the supply and demand imbalance amount does not fall within the reference range even by these processes. In this case, in order to share the insufficient power to the shared power supply device 56, a discharge command for the shared secondary battery 56D and an output increase command for the shared fine adjustment generator 56C are issued.

  On the other hand, if the determination result of step 1403 indicates that | supply / demand unbalance amount |> | frequency lowering side limit supply / demand unbalance amount | is NO, in step 1405, | supply / demand unbalance amount |> | frequency increasing side. The marginal supply and demand imbalance amount | is determined. As a result, in the case of YES (in the case of excess power), the excess of the supply / demand imbalance increase side is assigned to the secondary battery 26D and the fine adjustment generator 26C by the distribution function 44 (step 1415). That is, although the charge command (step 1425) of the secondary battery 26D and the output decrease command (step 1435) of the fine adjustment generator 26C are performed, the supply and demand imbalance amount does not fall within the reference range even by these processes. In this case, in order to share the excess power to the shared power supply device 56, a charge command for the shared secondary battery 56D and an output decrease command for the shared fine adjustment generator 56C are issued.

  As described above, according to the present embodiment, the shared secondary battery 56D and the shared fine-tuning generator 56C are provided, and these charge / discharge commands and generator output increase / decrease commands are executed, thereby making it more economical. Thus, the supply and demand imbalance amount can be controlled more flexibly within the reference range.

  Next, the embodiment shown in FIG. 20 will be described. In this embodiment, a secondary battery 56 </ b> D is used as the shared power supply device 56. In this case, normally, the circuit breaker 8 is opened (indicated by X in the figure), and the shared secondary battery 56D is on standby. When the child microgrid interconnection breaker 7 of the child microgrid interconnection line 6 is cut off and a child microgrid 5 becomes an independent system, this situation is cut off. Detected by the shutoff information of the device 7. Then, the shared secondary battery 56D is connected to the child microgrid 5 that is an independent system, and the shared secondary battery 56D is urgently discharged or charged.

  FIG. 21 shows a schematic sequence of processing from when a certain child microgrid 5 becomes an independent system, until this is detected and emergency discharge or emergency charging of the shared secondary battery 56D is performed. In FIG. 21, for example, in the control system 30 of the child microgrid 54, the tidal flow rates of the inter-microgrid interconnection line flows P24 and P45 are collected by the interconnection line tidal flow collecting means 37 (step 2101). The supply / demand imbalance amount calculation means 38 calculates the sum of the inter-micro-grid interconnection currents P24 and P45, that is, the supply / demand imbalance amount (step 2102).

  If it is detected that the circuit breaker 7 (in this case, 724, 745) of the interconnection line 6 between the child microgrids (in this case, 624, 645) is cut off (step 2103: YES), is the supply-demand unbalance amount positive? It is determined whether it is negative (step 2104). As a result, when the supply and demand imbalance amount> 0 (in the case of power shortage), the distribution function 44 causes each power supply device to share the power shortage (step 2105). That is, first, a discharge command is given to the secondary battery 26D of the power supply device 26 of the disconnected child microgrid 54 (step 2106), and the circuit breaker 8 provided on the line to the shared secondary battery 56D is turned on. The shared secondary battery 56D is connected (step 2107). Then, a discharge command is issued to the connected shared secondary battery 56D (step 2108). The distribution ratio of the secondary battery 26D and the shared secondary battery 56D is determined by the distribution function 44 based on their discharge capacity.

  On the other hand, when the supply and demand imbalance amount <0 (in the case of excess power), the distribution function 44 causes each power supply device to share excess power (step 2109). That is, first, a charge command is given to the secondary battery 26D of the power supply device 26 of the interrupted child microgrid 54 (step 2110), and the circuit breaker 8 provided on the line to the shared secondary battery 56D is turned on. The shared secondary battery 56D is connected (step 2111). Then, a charge command is issued to the connected shared secondary battery 56D (step 2112). The charge sharing ratio between the secondary battery 26D and the shared secondary battery 56D is determined by the distribution function 44 based on their charge capacity.

  As described above, according to the present embodiment, the shared secondary battery 56D is provided, and when the child microgrid 5 is shut off, this is detected and the emergency secondary battery is charged and discharged by the shared secondary battery 56. This enables more reliable and more flexible control.

  In the above embodiment, when the child microgrid 5 becomes an independent system, this is detected, and the common secondary battery 56D is urgently discharged or urgently charged. You may cut off the generator.

  In FIG. 22, when the child microgrid 5 becomes an independent system, this is detected, and after the emergency discharge or the emergency charging of the shared secondary battery 56 is performed, the emergency load shutdown or the emergency generator shutdown is performed as necessary. It is a schematic sequence diagram which shows the process until it performs.

  In this embodiment, the input unit 500 is the same as the input unit 500 described with reference to FIG. The interconnection line power flow value, the load amount in the child microgrid, and the power generation amount in the child microgrid are input (step 2201).

  Here, for example, the child microgrid 54 will be described as an example. In the control system 30, the supply / demand imbalance amount calculation is performed using the inter-child microgrid interconnection currents P 24 and P 45 input by the input unit 500. The means 38 calculates the sum of the inter-microgrid interconnection line flows P24 and P45, that is, the supply and demand imbalance amount (step 2202).

  If it is detected that the circuit breaker 7 (in this case, 724, 745) of the interconnection line 6 (in this case, 624, 645) between the child microgrids is disconnected (step 2203: YES), is the supply-demand imbalance amount positive? It is determined whether it is negative (step 2204). As a result, when the supply and demand imbalance amount> 0 (in the case of power shortage), the distribution function 44 shares the power shortage (step 2205). That is, first, a discharge command is given to the secondary battery 26D of the power supply device 26 of the disconnected child microgrid 54 (step 2206), and the circuit breaker 8 provided on the line to the shared secondary battery 56D is turned on. The shared secondary battery 56D is connected (step 2207). Then, a discharge command is issued to the connected shared secondary battery 56D (step 2208). The discharge sharing ratio of the secondary battery 26D and the shared secondary battery 56D is determined by the distribution function 44 from their discharge capacities. Further, when the supply and demand imbalance state is not eliminated even by the emergency discharge of the secondary battery 26D and the shared secondary battery 56D, the emergency load cutoff means 503 cuts off the load urgently (step 2209).

On the other hand, when the supply and demand imbalance amount <0 (in the case of excess power), the distribution function 44 shares the excess power (step 2210). That is, first, a charge command is given to the secondary battery 26D of the power supply device 26 of the disconnected child microgrid 54 (step 2211), and the circuit breaker 8 provided on the line to the shared secondary battery 56D is turned on. The shared secondary battery 56D is connected (step 2212). Then, a charge command is issued for the connected shared secondary battery 56D (step 2213). The charge sharing ratio between the secondary battery 26D and the shared secondary battery 56D is determined by the distribution function 44 based on their charge capacity. Further, when the supply and demand imbalance state is not resolved even by the emergency charging of the secondary battery 26D and the shared secondary battery 56D, the generator is urgently shut down by the emergency generator shutting means 504 (step 2214).

  Thus, according to the present embodiment, when the child microgrid 5 is interrupted, this is detected, and in addition to performing the emergency secondary battery charging / discharging by the shared secondary battery 56, By providing the function of shutting off the generator, more reliable and flexible control is possible.

1 is a conceptual system diagram showing an embodiment of a power grid interconnection system according to the present invention. It is a conceptual system diagram which shows the state which interrupted | blocked all the connection line circuit breakers of the electric power system shown in FIG. FIG. 2 is a conceptual system diagram illustrating a state in which two connection line breakers with a main system on the side of a power system shown in FIG. 1 and a main system on the small power system side are cut off. In the power system shown in Fig. 1, the small power system is separated into two groups by the fault power system by cutting off the two interconnected lines on the side of the power system and the small power system. It is a conceptual system diagram which shows a state. It is a conceptual system diagram which shows the state which interrupted | blocked the interconnection line breaker with the main | strain system of the electric power system shown in FIG. FIG. 2 is a conceptual configuration diagram illustrating a configuration of one small-scale power system in FIG. 1. It is a characteristic view which shows the load sharing state by the various generators of the power supply device shown in FIG. It is a flowchart showing the control sequence for making the supply-and-demand imbalance in the child small-scale power system shown in FIG. 6 zero. It is a characteristic view which shows the state which changes to the generator for fine adjustment shown in FIG. 7, and absorbs a demand imbalance by charging / discharging of a secondary battery. It is a flowchart showing the control sequence for making the supply-and-demand imbalance in the child small-scale electric power system shown in FIG. 6 as zero as possible using a secondary battery. FIG. 7 is a characteristic diagram for explaining a relationship between supply and demand imbalance and frequency fluctuation when the child microgrid interconnection breaker is cut off in the child small-scale power system shown in FIG. 6. It is a flowchart showing the control sequence for keeping the supply-and-demand imbalance in the sub small-scale electric power system shown in FIG. 6 in the predetermined range by the generator for fine adjustment. It is a flowchart showing the control sequence for keeping the supply-and-demand imbalance in the sub small-scale electric power system shown in FIG. 6 in the predetermined range by charging / discharging of a secondary battery. FIG. 7 is a flowchart showing a control sequence for keeping supply and demand imbalance in the child small-scale power system shown in FIG. 6 within a predetermined range by charging and discharging a secondary battery and a fine adjustment generator. FIG. 7 is a flowchart showing a control sequence for keeping the supply and demand imbalance in the child small-scale power system shown in FIG. 6 within a predetermined range by charging and discharging a secondary battery with a margin and a fine adjustment generator. Explains the relationship between supply and demand imbalance and frequency fluctuation when the breaker between micro-microgrids is cut off in the child small-scale power system shown in FIG. 6, and changes in frequency when emergency generator / load interruption is performed FIG. It is a functional block diagram explaining the emergency generator / load cutoff function used by this invention. It is a conceptual system diagram explaining the case where a common power supply device (secondary battery, fine adjustment generator) is used for a plurality of small-scale power systems shown in FIG. It is a flowchart showing the control sequence for making the supply-and-demand imbalance of a child small-scale power system zero as much as possible using the shared power supply device of FIG. It is a conceptual system diagram explaining the case where a common power supply device (secondary battery) is used for a plurality of small-scale power systems shown in FIG. It is a flowchart showing the control sequence for making the supply-and-demand imbalance of a child small-scale power system zero as much as possible using the shared secondary battery of FIG. In the power system shown in FIG. 20, the secondary battery charge / discharge control and emergency generator / load cut-off control are performed for the supply and demand imbalance in a certain small-scale power system when the power breaker between the child microgrids is cut off. It is a flowchart showing the control sequence for falling in a predetermined range.

Explanation of symbols

1 Small power system (microgrid)
2 Core system 3 Interconnection line 4 Interconnection line breaker 5 Child small-scale power system (child microgrid)
6 Small-scale power system interconnection line 7 Small-scale power system interconnection circuit breaker 26 Power supply device 26C Fine adjustment generator 26D Secondary battery 30 Monitoring control system having monitoring control means as function 48 Emergency cut-off function 56 Common power supply 56C Common fine-tuning generator 56D Common secondary battery

Claims (8)

A main power system and a small-scale power system interconnected by the main power system and a main interconnection line, and the small-scale power system includes a plurality of children each having a power load and a power supply device for the power load. Small-scale power systems are connected in series with each other through a child interconnection line , and the child small-scale power systems located at both ends of the plurality of child small-scale power systems connected in series are connected to the main interconnection line. A power grid interconnection system connected to a connection point with
Provided in each of the child small-scale power systems, monitoring the magnitude of the power flow of the child interconnection lines, and obtaining the supply and demand imbalance amount in the corresponding child small-scale power system from the power flow of these child interconnection lines, Power comprising a monitoring control means for controlling either or both of the power load amount and the power generation amount of the power supply device corresponding to the supply and demand imbalance amount as much as possible to be zero Grid interconnection system. A main power system and a small-scale power system interconnected by the main power system and a main interconnection line, and the small-scale power system includes a plurality of children each having a power load and a power supply device for the power load. Small-scale power systems are connected in series with each other through a child interconnection line , and the child small-scale power systems located at both ends of the plurality of child small-scale power systems connected in series are connected to the main interconnection line. A power grid interconnection system connected to a connection point with
Provided in each of the child small-scale power systems, monitoring the magnitude of the power flow of the child interconnection lines, and obtaining the supply and demand imbalance amount in the corresponding child small-scale power system from the power flow of these child interconnection lines, Either or both of the power load amount and the power generation amount of the power supply device corresponding to the sub-small power system so that the supply and demand imbalance amount is within a reference range determined by the frequency tolerance of the corresponding sub-small power system. A power grid interconnection system comprising monitoring control means for controlling the power.   A secondary battery that can be charged / discharged is used as a part of the power supply, and the monitoring control means controls charging of the secondary battery when the supply / demand imbalance exceeds the amount of power generation, and the secondary battery when the load is excessive. The power system interconnection system according to claim 1, wherein the secondary battery is controlled to be discharged.   As a power supply device, a chargeable / dischargeable secondary battery is used as a part thereof, and the monitoring control means has a function of monitoring the presence / absence of interruption of the child interconnection line with another child small-scale power system, and corresponds. When the disconnection of the child interconnection is detected, the supply / demand imbalance at that time is controlled to charge the secondary battery if the power generation amount is excessive, and the secondary battery is discharge controlled if the load is excessive. The power grid interconnection system according to claim 1 or 2.   As part of the power load, a load that can be cut off urgently when the load exceeds the load is provided, and as a power supply unit, a generator that can be cut off urgently when the amount of generated power is exceeded is provided. It has a function to monitor the presence or absence of the interruption of the child interconnection line with the scale power system, and if the interruption of the corresponding child interconnection line is detected, the emergency interruption can be performed if the supply and demand imbalance at that time exceeds the power generation amount 5. An emergency shut-off function for shutting off a power generation facility and emergency shutting off the load capable of being shut off in an emergency when the load is exceeded. Power system interconnection system.   A common power supply device that is configured to be connectable to a plurality of sub-small power systems that make up a small-scale power system, and whose power generation is controlled according to the supply and demand imbalance of the connected sub-small power systems. The power grid interconnection system according to claim 1, wherein the power grid interconnection system is provided.   A secondary battery that can be charged / discharged is used as part of the shared power supply, and this secondary battery is subject to charge / discharge control according to the supply / demand imbalance of the connected small-scale power system. The power grid interconnection system according to claim 6, wherein the system is a power grid interconnection system.   Shared secondary battery that is configured to be connectable to multiple small-scale power systems that make up a small-scale power system, and that is charged and discharged according to the supply and demand imbalance of the connected small-scale power systems. The power grid interconnection system according to any one of claims 1 to 5, characterized by comprising: