Standalone grid-connected systems and power conditioners

Abstract

To implement autonomous operation by a plurality of power conditioners without performing mutual information communication.SOLUTION: An autonomous interconnection system comprises: a first power conditioner PCS1 configured to be capable of autonomous operation; and a second power conditioner configured to control output of an interconnection terminal P22 according to voltage and a frequency of the interconnection terminal P22. The first power conditioner PCS1 comprises: detection means for detecting a charging enabled / disabled state of power storage means BT; and control means for controlling at least one of voltage and a frequency of an autonomous terminal P13. When it is detected that the power storage means BT is in a charging disabled state, the control means makes the frequency of the autonomous terminal P13 change into the outside of a standard range of a system interconnection standard to stop output of the second power conditioner PCS2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an autonomous interconnection system and a power conditioner that include a distributed power source such as a photovoltaic power generation means and a power storage means, and a power conversion device. [Background technology]

[0002] In a power generation system utilizing a photovoltaic power generation means, in the event of a power outage or the like, a so-called stand-alone operation is performed in which a power conditioner is operated in a state separated from the power grid to supply power to a load.

[0003] For example, Patent Document 1 discloses a grid-connected inverter device that performs grid-connected operation to supply AC power from the power grid to a load when there is no power outage in the power grid, and performs independent operation to disconnect the load from the power grid and supply power from a DC power source to the load when a power outage occurs in the power grid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-184673 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a need to increase the supply capacity to loads during autonomous operation from a power conditioner with autonomous operation function (hereinafter referred to as an "autonomous PCS"), or to connect a power conditioner connected to another distributed power source (hereinafter referred to as a "grid-connected PCS") to supply additional power in cases where the output power or power generation amount of a solar power generation means is insufficient with the autonomous PCS alone.

[0006] However, if the power supply from the grid-connected PCS continues to exceed the power consumption of the load, it is expected that the storage means of the stand-alone PCS will become fully charged. This could cause malfunctions due to an increase in the bus voltage of the stand-alone PCS, or the power conditioners of both the stand-alone PCS and the grid-connected PCS may stop operating, making it impossible to supply power to the load.

[0007] To address this issue, for example, in a grid-connected PCS, there is a method of monitoring the state of the power storage means of a stand-alone PCS and adjusting the amount of power output from the grid-connected PCS. However, this poses a problem in that the grid-connected PCS needs to be provided with an additional output control function.

[0008] In view of the above problems, an object of the present invention is to realize independent operation using a plurality of power conditioners without exchanging information between the plurality of power conditioners. [Means for solving the problem]

[0009] In a first aspect of the present invention, the present invention is directed to an autonomous interconnection system and includes a first power conditioner having a first power supply terminal to which a first distributed power source including a chargeable and dischargeable storage means is connected, and an autonomous terminal connected to a load, and configured to be capable of autonomous operation in which the load is isolated from the power grid and power supplied from the first distributed power source is supplied to the load via the autonomous terminal; and a second power conditioner having a second power supply terminal to which a second distributed power source is connected and an interconnection terminal connected to the autonomous terminal and the load, and configured to control the output of the interconnection terminal in accordance with the voltage and frequency of the interconnection terminal, the first power conditioner having a detection means for detecting whether the storage means is chargeable or not, and a control means for controlling at least one of the voltage or frequency of the autonomous terminal, and when it is detected that the storage means is in a chargeable state, the control means changes the frequency of the autonomous terminal to outside the standard range of the grid interconnection regulations, thereby stopping the output of the second power conditioner.

[0010] According to the configuration of the first aspect, when the power storage means is in a non-chargeable state, the first power conditioner can stop the output of the second power conditioner without exchanging information with the second power conditioner. This makes it possible to avoid, for example, a situation in which discharged power from the second power conditioner continues to be supplied to the first power conditioner even when the power storage means is fully charged, causing a malfunction of the grid-connected system or stopping the power supply to the load. In other words, the grid-connected system of this aspect can achieve grid-connected operation using multiple power conditioners without exchanging information with the multiple power conditioners.

[0011] In the above aspect, the control means of the first power conditioner may change the frequency of the autonomous terminal to a first frequency that is outside the specification range of the grid interconnection regulations, and then change it to a second frequency that is lower than the first frequency and does not cause the second power conditioner to return to interconnection operation.

[0012] According to this configuration, the control means of the first power conditioner changes the frequency to a second frequency lower than the first frequency when the second power conditioner continues to be in a state where it does not return to interconnected operation, thereby minimizing the impact on the load.

[0013] In the above aspect, the detection means may be configured to acquire the charge amount of the storage means and detect the charge amount of the storage means, and the control means of the first power conditioner may execute a first step of determining that the storage means is in a non-chargeable state and changing the frequency of the self-sustaining terminal to a value outside a range of grid interconnection regulations when it is detected that the charge amount of the storage means acquired by the detection means has become equal to or greater than a predetermined first threshold, and a second step of returning the frequency of the self-sustaining terminal to a value within a specified range of the grid interconnection regulations after the first step when the charge amount of the storage means acquired by the detection means has become less than a predetermined second threshold that is smaller than the first threshold.

[0014] According to this configuration, when the power storage means of the first power conditioner becomes chargeable, the charging can be resumed, so that the power generated by the second power conditioner can be used effectively.

[0015] In a second aspect of the present invention, a power conditioner receives power supplied from a first distributed power source including a chargeable and dischargeable storage means and supplies the power to a load connected to an electric wire. The load is connected to a grid-connected power conditioner via the electric wire, the grid-connected power conditioner being configured to control the output power to the electric wire in accordance with the voltage and frequency of the electric wire. The power conditioner has a first power supply terminal to which the first distributed power source is connected and an independent terminal connected to the electric wire, and is configured to be capable of independent operation in which the load is disconnected from the power grid and the power supplied from the first distributed power source via the independent terminal is supplied to the load. The power conditioner is further configured to include a detection means for detecting whether the storage means is chargeable or not, and a control means for controlling at least one of the voltage or frequency of the independent terminal. When the control means detects that the storage means is in a chargeable state, the control means changes the frequency of the independent terminal to a value outside the specified range of grid interconnection regulations, thereby stopping the output of the grid-connected power conditioner.

[0016] As in the first aspect, the power conditioner of the second aspect can stop the output of the grid-tied power conditioner without exchanging information with the grid-tied power conditioner when the power storage means is in a non-chargeable state. This makes it possible to avoid, for example, a malfunction caused by continuous input of discharged power from the grid-tied power conditioner even when the power storage means is fully charged, or a situation in which power supply to the load is stopped. [Effects of the Invention]

[0017] According to the present invention, it is possible to realize autonomous operation using a plurality of power conditioners without exchanging information between the plurality of power conditioners. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing the overall configuration of an autonomous interconnection system according to an embodiment. [Figure 2] Flowchart showing an example of the operation of an autonomous interconnected system [Figure 3] Timing chart showing an example of the operation of an autonomous interconnected system [Figure 4] Diagram to explain grid interconnection regulations [Figure 5] Timing chart showing another example of operation of an autonomous interconnected system DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the scope of application or use of the present invention.

[0020] FIG. 1 is a diagram showing an example of the configuration of an autonomous interconnection system according to an embodiment.

[0021] As shown in FIG. 1, the grid-connected system includes a first distributed power generation system 10 and a second distributed power generation system 20.

[0022] -The first distributed power system- The first distributed power system 10 includes a photovoltaic power generation means PV1, a power storage means BT such as a storage battery, and a first power conditioner PCS1. The photovoltaic power generation means PV1 and the power storage means BT are an example of a first distributed power source.

[0023] The first power conditioner PCS1 is configured to be capable of grid-connected operation and stand-alone operation.

[0024] In this disclosure, "grid-connected operation" refers to an operating state in which AC power supplied from the power grid is supplied to a load. Also, "grid-connected mode," which will be described later, is an operating mode in which the distributed power source is controlled to extract and output maximum power according to the voltage and frequency of the grid-connected terminal.

[0025] "Standalone operation" refers to the supply of power from a distributed power source to a load by disconnecting the load from the power grid when a power outage or other event occurs and the supply of power from the power grid is stopped. "Standalone mode," which will be described later, is an operating mode that enables charging and discharging via the standalone terminal during standalone operation.

[0026] The first power conditioner PCS1 is provided with an input terminal P11 to which the photovoltaic power generation means PV1 is connected, an input / output terminal P12 to which the power storage means BT is connected, and an independent terminal P13 to which the load 7 is connected. The input terminal P11 and the input / output terminal P12 are examples of a first power supply terminal.

[0027] When operating in the independent mode, the first power conditioner PCS1 is configured to determine the voltage and frequency of the independent terminal P13 based on the control of a control unit described later. In addition, in the independent mode, the first power conditioner PCS1 discharges the power input from the photovoltaic power generation means PV1 and / or the power storage means BT via the independent terminal P13, and charges the power input from the independent terminal P13 to the power storage means BT, in order to maintain the balance of power input and output to and from the independent terminal.

[0028] The first power conditioner PCS1 includes a detection means for detecting whether the power storage means BT is chargeable or not (chargeable / not chargeable), and a control means for controlling at least one of the voltage and frequency of the stand-alone terminal.

[0029] 1 shows a specific example of the configuration of the first power conditioner PCS1. However, the configuration of the first power conditioner PCS1 is not limited to the configuration shown in FIG.

[0030] In the example of FIG. 1, the first power conditioner PCS1 includes two DC / DC converters 11 and 12, a bidirectional DC / AC inverter 13 (hereinafter simply referred to as the “inverter 13”), and a control unit .

[0031] DC / DC converter 11 is connected to photovoltaic power generation means PV1 via input terminal P11. DC / DC converter 11 receives power generated by photovoltaic power generation means PV1, boosts or lowers the voltage depending on the generated voltage, and outputs the voltage to inverter 13 via DC bus 15. DC / DC converter 11 is configured to be able to control the amount of power extracted from photovoltaic power generation means PV1, and is configured to be able to perform maximum power point tracking control, for example. By performing this maximum power point tracking control, maximum power can be extracted from photovoltaic power generation means PV1. Note that a conventionally known configuration can be used for DC / DC converter 11, and therefore a detailed description of the circuit configuration will be omitted here.

[0032] The DC / DC converter 12 is a bidirectional DC / DC converter, and is connected to the power storage means BT via an input / output terminal P12. The DC / DC converter 12 controls the charging and discharging of the power storage means BT based on a charge / discharge control signal received from the control unit 14. The discharged power of the power storage means BT is output to the inverter 13 via a DC bus 15. During charging, the power input to the DC / DC converter 12 via the DC bus 15 is charged into the power storage means BT. Note that the DC / DC converter 12 can have a conventionally known configuration, and therefore a detailed description of the circuit configuration will be omitted here.

[0033] Inverter 13 is a bidirectional inverter. During discharging, the output powers from DC / DC converters 11 and 12 are added together and input to inverter 13, where they are converted from DC to AC and output from self-sustaining terminal P13 or a grid-connection terminal (not shown) connected to the power grid. During charging, power input to the inverter from self-sustaining terminal P13 or the grid-connection terminal is converted from AC to DC and charged into power storage means BT via DC / DC converter 12. Note that a conventionally known configuration can be used for inverter 13, and therefore detailed description of the circuit configuration will be omitted here.

[0034] The control unit 14 is realized by a program stored in, for example, a microcomputer, and has a function of controlling each unit of the first power conditioner PCS 1. The control unit 14 also has a function of receiving and centrally managing various information such as various setting information set from the outside, a current value detected by a CT sensor (not shown) and / or the aforementioned power storage information acquired from the power storage means BT.

[0035] In this example, the control unit 14 has a function as a detection unit that detects whether the power storage unit is chargeable or not based on the information that it acquires and manages. For example, the information to be acquired includes information indicating that the maximum charging power (specification) of the power storage unit BT has been exceeded, information indicating the current amount of stored power in the power storage unit BT, and / or information indicating that the power storage unit BT is discharging. Then, based on this acquired information, the control unit 14 detects whether the power storage unit BT is chargeable or not. Note that the method for detecting whether the power storage unit BT is chargeable or not is not limited to the above method. For example, a dedicated sensor or the like may be provided, and the chargeable or not state may be detected based on input information from the sensor. Also, a configuration that realizes the function of the detection unit independently of the control unit 14 may be provided.

[0036] The control unit 14 also functions as a control means for setting the output of the first power conditioner PCS1, that is, the voltage and / or frequency of the self-sustaining terminal P13 and the grid-connected terminal (not shown).

[0037] For example, in a normal operating state (operation in the grid-connected mode), the control unit 14 sets the output of the first power conditioner PCS1 to a predetermined voltage and a predetermined frequency (e.g., 60.0 Hz) in accordance with the grid-connected regulations. Furthermore, for example, when the control unit 14 detects that the power storage means is in a non-chargeable state, it changes the frequency of the independent terminal P13 to outside the specified range of the grid-connected regulations. The frequency control of the independent terminal P13 by the control unit 14 will be described later with a specific example.

[0038] -The second distributed power system- The second distributed power system 20 includes a photovoltaic power generation means PV2 and a second power conditioner PCS2. The second power conditioner PCS2 is configured to be capable of grid-connected operation and is an example of a grid-connected power conditioner. The photovoltaic power generation means PV2 is an example of a second distributed power source.

[0039] The second power conditioner PCS2 is provided with an input terminal P21 to which the photovoltaic power generation means PV2 is connected, and an interconnection terminal P22 to which the load 7 is connected. The input terminal P21 is an example of a second power supply terminal.

[0040] 1 shows a specific example of the configuration of the second power conditioner PCS2. However, the configuration of the second power conditioner PCS2 is not limited to the configuration shown in FIG.

[0041] In the example of FIG. 2, the second power conditioner PCS2 includes a DC / DC converter 21, a DC / AC inverter 23 (hereinafter simply referred to as the “inverter 23”), and a control unit 24.

[0042] The DC / DC converter 21 is connected to the solar power generation means PV2 via an input terminal P21. The DC / DC converter 21 receives power generated by the solar power generation means PV2, boosts or lowers the voltage depending on the generated voltage, and outputs the voltage to the inverter 23 via a DC bus 25. The DC / DC converter 21 is configured to be able to control the amount of power extracted from the solar power generation means PV2, and is configured to be able to perform, for example, maximum power point tracking control. By performing this maximum power point tracking control, the maximum power can be extracted from the solar power generation means PV2. Note that the DC / DC converter 21 can have a conventionally known configuration, and therefore a detailed description of the circuit configuration will be omitted here.

[0043] The inverter 23 receives the output power from the DC / DC converter 21 as an input, converts it into AC current, and outputs it from the grid-connection terminal P22. Note that a conventionally known configuration can be used for the inverter 23, and therefore a detailed description of the circuit configuration will be omitted here.

[0044] The control unit 24 is realized by, for example, a program stored in a microcomputer, and has a function of controlling each unit of the second power conditioner PCS 2. The control unit 24 also has a function of receiving and centrally managing various information such as various setting information set from the outside and current values ​​detected by a CT sensor (not shown).

[0045] Specifically, the control unit 24 is configured to operate in a grid-connected mode during normal operation, and in the grid-connected mode, the control unit 24 controls the output (voltage and frequency) of the grid-connected terminal P22 according to the voltage and frequency of the grid-connected terminal P22 so that the output is within the standard range of the grid-connected regulations.

[0046] -Example of operation of an autonomous interconnected system (1)- Next, the operation of the autonomous interconnection system will be described with reference to FIGS.

[0047] (Step S11) In this example, the first power conditioner PCS1 and the second power conditioner PCS2 are powered on, and in step S11 (time t10 in FIG. 4), normal operation is performed without a power outage or the like. In other words, in step S11, the first power conditioner PCS1 and the second power conditioner PCS2 are operating in a grid-connected mode. In normal operation, AC power supplied from the power grid is supplied to the load 7.

[0048] (Step S12) In the next step S12, it is determined whether the power supply from the power grid has been cut off due to a power outage, etc. The specific method for determining this is not particularly limited, and any conventionally known method can be used.

[0049] In step S12, if the power supply from the power grid is not interrupted (NO in S12), normal operation continues. On the other hand, if the power supply from the power grid is interrupted due to a power outage or the like (YES in S12), the flow proceeds to step S13.

[0050] (Step S13) In step S13, the first power conditioner PCS1 shifts from the grid-connected mode to the independent mode and switches to independent operation (time t11 in FIG. 4). In other words, the first power conditioner PCS1 disconnects the load 7 from the power grid and supplies the power supplied from the first distributed power source (photovoltaic power generation means PV1 or power storage means BT) to the load 7 via the independent terminal P13. In other words, the first power conditioner PCS1 operates so that the power supplied to the load is not interrupted.

[0051] At time t12, the second power conditioner PCS2 starts up, and the voltage and frequency at the grid-connected terminal P22 become the same as when the power conditioner is grid-connected. Then, the second power conditioner PCS2 automatically resumes operation in the grid-connected mode. In this example, it is assumed that the power supplied from the second power conditioner PCS2 is greater than the power consumption of the load 7. Then, the differential power is input via the self-sustaining terminal P13, and charging of the power storage means BT begins. In FIG. 3, the third row from the top shows the charge amount R of the power storage means BT, and the charge amount R (initial value = R0) begins to increase from time t12.

[0052] (Step S14) In step 14, it is determined whether charging to the power storage means BT is possible or not. For example, if the power storage means BT is close to being fully charged or if the first power conditioner PCS1 is unable to draw the charging power input from the self-sustaining terminal P13 due to an abnormality or the like, it is determined that charging is not possible. In this example, the control unit 14 determines that charging is not possible when the charge amount of the power storage means BT exceeds a predetermined threshold Rt1. The predetermined threshold Rt1 can be set arbitrarily, for example, to a value that has a slight margin beyond full charge.

[0053] If it is determined in step S14 that charging is possible, the first power conditioner PCS1 and the second power conditioner PCS2 continue to operate in the grid-connected mode. Then, at time t13, when the charge amount of the power storage means BT exceeds the threshold value Rt1, the control unit 14 determines that the power storage means BT is in a charge-disabled state (determined as unchargeable in S14), and the flow proceeds to the next step S15.

[0054] (Step S15) In step S15, the control unit 14 changes the frequency of the independent terminal P13 to a value outside the range specified by the grid interconnection regulations, thereby stopping the output of the second power conditioner PCS2. The processes in steps S14 and S15 are an example of a first step.

[0055] Specifically, for example, the control unit 14 changes the frequency of the independent terminal P13 outside the standard range with respect to the protection coordination of the system connection regulations (system connection rules) shown in FIG. 5. For example, the control unit 14 sets the frequency f of the independent terminal P13 to a frequency f1 that is about 1 Hz higher than the upper limit frequency (for example, 61 Hz) for continuous operation, and sets the duration tx (tx = t14 - t13) longer than the specified time (0.06 seconds). At this time, for example, the control unit 14 sets the slope of the change in the frequency f of the independent terminal P13 to +2 Hz.

[0056] In the second power conditioner PCS2, when it is detected that the frequency of the connection terminal P22 is out of the specification, the control unit 24 stops the output of the inverter 23 (time t14). The frequency f1 is an example of the first frequency.

[0057] Furthermore, for the purpose of continuously stopping the second power conditioner PCS2, after changing the frequency f of the independent terminal P13 to the frequency f1, the control unit 14 changes the frequency f to a frequency f2 (f2 < f1) at which the second power conditioner PCS2 does not perform a return operation. The frequency f2 can be arbitrarily set. For example, it is set to "f2 = specified rated upper limit value + ΔF". For example, the second power conditioner PCS2 is configured not to perform an interconnection operation (so-called return operation) when it is greater than ΔF (for example, ΔF = 0.1 Hz) higher than the specified rated frequency value. The frequency f2 is an example of the second frequency.

[0058] (Step S16) In step S16, it is determined whether the second power conditioner PCS2 is in a state where it can discharge. Whether it is possible to discharge can be determined, for example, based on whether the power storage means BT can store the discharged power of the second power conditioner PCS2 or whether the discharged power of the second power conditioner PCS2 is consumed by a load. Specifically, the control unit 14 can determine whether it is possible to discharge based on, for example, the bus voltage. For example, if the bus voltage drops, the control unit 14 determines that there is a power supply shortage and increases the supply amount, and if the bus voltage rises, it determines that there is an oversupply and decreases the supply amount. The same applies to the second power conditioner PCS2. In this example, the control unit 14 of the first power conditioner PCS1 determines that the second power conditioner PCS2 is in a state where it can discharge when the charge amount of the power storage means BT is less than a predetermined threshold Rt2, and the flow proceeds to the next step S17.

[0059] (Step S17) In step S17, the control unit 14 of the first power conditioner PCS1 returns the frequency of the independent terminal P13 to within the standard range of the grid interconnection regulations (time t15).

[0060] When the frequency of the grid-connection terminal P22 returns to within the specified range of the grid-connection regulations, the control unit 24 transitions to operation in the grid-connection mode based on the detection result of the frequency of the grid-connection terminal P22, and resumes output of the inverter 23 (time t15). Then, in the first power conditioner PCS1, charging of the power storage means BT is resumed. In this way, when the power storage means BT becomes chargeable, charging can be resumed, so that the power generated by the second power conditioner PCS2 can be effectively utilized. The processing in steps S16 and S17 is an example of the second step.

[0061] Then, the operations from step S14 to step S17 are repeated until the power grid is restored.

[0062] As described above, according to this embodiment, when the control unit 14 detects that the amount of stored power in the power storage unit BT is in a state where the power storage unit cannot be charged, the control unit 14 changes the frequency f of the isolated terminal P13 to fall outside the range specified in the grid interconnection regulations, thereby stopping the output of the second power conditioner PCS2. This makes it possible to achieve isolated operation using multiple power conditioners PCS1 and PCS2 without exchanging information between the first power conditioner PCS1 and the second power conditioner PCS2. In other words, the isolated grid interconnection system of the present disclosure is characterized in that it is not necessary to add a new function to the second power conditioner PSC2, and it is sufficient to simply add the first power conditioner PSC1 to an existing system.

[0063] Furthermore, the control unit 14 changes the frequency f of the independent terminal P13 to a frequency f2 that is lower than the frequency f1 so as to maintain the state in which the second power conditioner PCS2 does not return to the interconnected operation. This makes it possible to minimize the impact on the load 7.

[0064] Furthermore, in addition to the operation of the grid interconnection regulations, by setting the frequency before the recovery of the second power conditioner PCS2, it is possible to secure the discharge operation time of the power storage means BT of the first power conditioner PCS1. As a result, the power storage means BT reaches a discharged state, and the second power conditioner PCS2 can supply power to the power storage means BT without causing chattering after the recovery of operation.

[0065] -Example of operation of an autonomous interconnected system (2)- Next, another example of the operation of the autonomous interconnection system will be described with reference to Fig. 2 and Fig. 5. Here, the differences from "Operation Example (1) of the Autonomous Interconnection System" (hereinafter simply referred to as "Operation Example 1") will be mainly described. Specifically, in this operation example, the overall processing flow is the same as in Fig. 2. However, the method of determining whether charging is possible or not in step S14 and the method of adjusting the output frequency in step S15 are different from those in Operation Example 1.

[0066] For convenience of explanation, in FIG. 5, elements common to or corresponding to those in FIG. 3 may be given the same reference numerals and explanations thereof may be omitted.

[0067] (Step S14) In this example, in step 14, it is determined whether charging to the power storage means BT is possible or not based on the bus voltage Vb of the DC bus 15. Specifically, as in operation example 1, the charge amount R (initial value=R0) starts to increase from time t12. Thereafter, when the charge amount R of the power storage means BT reaches a fully charged state R3, the bus voltage Vb starts to increase (time t33). In this example, the control unit 14 determines that charging is not possible when the bus voltage Vb exceeds a predetermined threshold Vt. The predetermined threshold Vt can be set arbitrarily.

[0068] If it is determined in step S14 that charging is possible, the first power conditioner PCS1 and the second power conditioner PCS2 continue to operate in the grid-connected mode. Then, at time t34, when the bus voltage Vb exceeds the threshold value Vt, the control unit 14 determines that the power storage means BT is in a charge-disabled state (determined as unchargeable in S14), and the flow proceeds to the next step S15.

[0069] (Step S15) In this example, similar to Operation Example 1, the control unit 14 changes the frequency of the isolated terminal P13 to fall outside the specified range of the grid interconnection regulations, but the direction of the change is different. Specifically, the control unit 14 sets the frequency f of the isolated terminal P13 to a frequency f3 that is approximately 1 Hz lower than the lower limit frequency for continued operation (e.g., 60 Hz), and sets the duration tx (tx=t14-t34) to be longer than the specified time (0.06 seconds). In this case, for example, the control unit 14 sets the slope of the change in the frequency f of the isolated terminal P13 to -2 Hz.

[0070] When the second power conditioner PCS2 detects that the frequency at the grid-connection terminal P22 is out of regulation, the control unit 24 stops the output of the inverter 23 (time t14).

[0071] Furthermore, in order to keep the second power conditioner PCS2 stopped, the control unit 14 changes the frequency f of the self-sustaining terminal P13 to a frequency f3, and then to a frequency f4 at which the second power conditioner PCS2 does not perform a recovery operation. Here, the frequency f4 is a frequency that deviates less from the grid interconnection specification than the frequency f3. The frequency f4 can be set arbitrarily, for example, to "f4 = specified rated upper limit value + ΔF." As in the first operational example, for example, the second power conditioner PCS2 is set not to perform an interconnection operation (so-called recovery operation) when the specified rated frequency value is greater than ΔF (for example, ΔF = 0.1 Hz).

[0072] In this example as well, when the control unit 14 detects that the amount of stored power in the power storage means BT is in a state where the power storage means cannot be charged, it changes the frequency f of the stand-alone terminal P13 to fall outside the standard range of the grid interconnection regulations and stops the output of the second power conditioner PCS2. This makes it possible to realize stand-alone operation using multiple power conditioners without exchanging information between the first power conditioner PCS1 and the second power conditioner PCS2.

[0073] In addition, the control unit 14 changes the frequency f of the independent terminal P13 to frequency f4 to maintain the state in which the second power conditioner PCS2 does not return to interconnected operation, thereby preventing any impact on the load. [Industrial Applicability]

[0074] The present invention is extremely useful because it enables autonomous operation using multiple power conditioners without the need for mutual information communication. Furthermore, it is extremely useful because it is possible to simply add a first power conditioner to an existing device (system) without the need to add functions to a second power conditioner. [Explanation of symbols]

[0075] 14 Control unit (electricity storage information acquisition means, control means) BT Power Storage Means (First Distributed Power Source) P11 Input terminal (first power supply terminal) P12 Input / Output terminal (first power supply terminal) P13 Self-standing terminal P21 Input terminal (second power supply terminal) P22 Grid connection terminal PCS1 First inverter PCS2 Secondary inverter PV1 Photovoltaic power generation means (first distributed power source) PV2 Photovoltaic power generation means (second distributed power source) f1 frequency (first frequency)

Claims

1. a first power conditioner having a first power supply terminal to which a first distributed power source including a chargeable and dischargeable storage means is connected, and an independent terminal to which a load is connected, the first power conditioner being configured to be capable of independent operation in which the load is disconnected from the power grid and power supplied from the first distributed power source is supplied to the load via the independent terminal; a second power conditioner having a second power supply terminal to which a second distributed power source is connected and a grid-connection terminal connected to the self-sustaining terminal and the load, the second power conditioner being configured to control an output of the grid-connection terminal in accordance with a voltage and a frequency of the grid-connection terminal; The first power conditioner includes: a detection means for detecting whether or not the storage means is chargeable; a control means for controlling at least one of the voltage and frequency of the independent terminal; When it is detected that the storage means is in a non-chargeable state, the control means changes the frequency of the independent terminal to outside a standard range of a grid interconnection provision to stop the output of the second power conditioner, and after changing the frequency of the independent terminal to a first frequency that is outside the standard range of the grid interconnection provision, changes it to a second frequency that has a smaller deviation from the grid interconnection provision than the first frequency and at which the second power conditioner does not perform an interconnection operation. Autonomous interconnected system.

2. the detection means is configured to acquire the charge amount of the power storage means and detect the charge amount of the power storage means; The control means of the first power conditioner a first step of determining that the storage means is in a non-chargeable state when it is detected that the charge amount of the storage means acquired by the detection means has reached a predetermined first threshold value or more, and changing the frequency of the stand-alone terminal to a value outside a range specified for grid interconnection; After the first step, when the charge amount of the power storage means acquired by the detection means becomes less than a predetermined second threshold value which is smaller than the first threshold value, a second step is executed in which the frequency of the stand-alone terminal is returned to within a standard range of the grid interconnection regulations. The autonomous interconnected system according to claim 1 .

3. A power conditioner that receives power supplied from a first distributed power source including a chargeable and dischargeable power storage means and supplies the power to a load connected to an electric line, a grid-tied power conditioner configured to control output power to the power line according to a voltage and a frequency of the power line is connected to the load via the power line; The power conditioner comprises: the power supply system has a first power supply terminal to which the first distributed power source is connected and an independent terminal to which the electric wire is connected, and is configured to be capable of independent operation in which the load is isolated from the power grid and power supplied from the first distributed power source via the independent terminal is supplied to the load; a detection means for detecting whether or not the storage means is chargeable; a control means for controlling at least one of the voltage and frequency of the independent terminal; When it is detected that the storage means is in a non-chargeable state, the control means changes the frequency of the independent terminal to outside a standard range of a grid interconnection regulation to stop the output of the grid-connected power conditioner, and after changing the frequency of the independent terminal to a first frequency that is outside the standard range of the grid interconnection regulation, changes it to a second frequency that has a smaller deviation from the grid interconnection regulation than the first frequency and at which the grid-connected power conditioner does not perform an interconnection operation. Power conditioner.

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