Power conditioner and power grid operation system

Abstract

To ensure adequate power in an event of an abnormality.SOLUTION: A power conditioner includes a control circuit. The control circuit can switch a power control mode to either of a first mode for executing operation not on the basis of inertia force and a second mode for executing the operation on the basis of inertia force. The control circuit performs an output control according to a first rating in the first mode and performs an output control according to a second rating different from the first rating in the second mode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a power conditioner and a power system operation system. [Background technology]

[0002] Power generation equipment using natural energy such as solar power generation does not have a mechanism for converting rotation into electricity like a synchronous generator. For this reason, in asynchronous power sources such as solar and other renewable energy generation and storage systems, there are power conditioning systems (PCSs) such as virtual synchronous generators (VSGs) that incorporate controls that simulate the inertia of synchronous generators. In this PCS, there is a control method called grid forming control (GFM) inverter that operates like a voltage source, as opposed to the conventional grid following control (GFL) inverter that operates like a current source. VSG control, which supplies inertia, and GFM control, which behaves like a power supply voltage, contribute to grid stabilization.

[0003] Some synchronous generators used in thermal power generation etc. can withstand a current equivalent to 1.5 times the rated current for at least 30 seconds. In the event of a grid fault, the synchronous generator can supply a reactive current that exceeds the rated current, ensuring voltage during the fault. To detect a grid fault, a protective relay is operated by the fault current supplied by the synchronous generator. However, VSG and PCS that perform GFM control have the problem that they cannot pass a current that significantly exceeds the rated current. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Matevosyan, J.; Badrzadeh, B.; Prevost, T.; Quitmann, E.; Ramasubramanian, D.; Urdal, H.; Huang, SH; Vital, V.; O'Sullivan, J.; Quint, R, Grid-Forming Inverters: Are They the Key for High Renewable Penetration?, IEEE Power and Energy Magazine, Volume: 17, Issue: 6, Nov.-Dec. 2019. Summary of the Invention [Problem to be solved by the invention]

[0005] One embodiment provides a power conditioner and a power system operation system that ensures adequate power during an abnormality. [Means for solving the problem]

[0006] According to one embodiment, the power conditioner includes a control circuit that can switch a power control mode between a first mode in which an operation is not based on an inertial force and a second mode in which an operation is based on an inertial force, and in the first mode, the control circuit controls output according to a first rating, and in the second mode, the control circuit controls output according to a second rating different from the first rating. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating a schematic diagram of a PCS and a power system operation system according to an embodiment. [Diagram 2] 6 is a flowchart showing a part of the control of a PCS according to an embodiment. [Diagram 3] 6 is a flowchart showing a part of the control of a PCS according to an embodiment. [Figure 4]6 is a flowchart showing a part of the control of a PCS according to an embodiment. [Diagram 5] 6 is a flowchart showing a part of the control of a PCS according to an embodiment. [Figure 6] 6 is a flowchart showing a part of the control of a PCS according to an embodiment. [Figure 7] 6 is a flowchart showing a part of the control of a PCS according to an embodiment. [Figure 8] 6 is a flowchart showing a part of the control of a PCS according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments will be described with reference to the drawings. In this disclosure, the terms "above", "below" and similar comparison terms may be used, but these terms may be appropriately read as "higher", "lower", etc., to the extent that they are not inconsistent. The same is true in reverse, and the terms "higher" and "lower" may be read as "above" and "below".

[0009] 1 is a diagram illustrating an example of a power conditioner (hereinafter, referred to as PCS) and a power system operation system according to an embodiment. The PCS 4 includes a power conversion unit 10, a control unit 12, a display unit 14, an operation unit 16, and a communication unit 18. In a broad sense, the power system operation system 1 may include either a power system 2 including a microgrid 20 connected to the PCS 4, or a power storage device 3.

[0010] The control unit 12 executes control of the power system operation system 1. The control unit 12 controls, for example, the output power in the power system operation system 1. The control unit 12 includes, for example, a processing circuit (control circuit) and a memory circuit, which are not shown. When the processing circuit is a general-purpose circuit, the control unit 12 is specifically realized using the processing circuit, which is a hardware resource, for information processing by software. In this case, the memory circuit may store a program or the like that enables the processing circuit to realize information processing. That is, the operation of the control unit 12 in the present disclosure can be interpreted as the operation of a control circuit.

[0011] The power conversion unit 10 includes a DC / AC inverter 100 and a DC / DC converter 102, and converts and outputs electric power. The power conversion unit 10 is a device capable of executing, for example, a first operation of generating electric power to be output to the electric power system 2 not based on a pseudo inertial force, and a second operation of generating electric power to be output to the electric power system 2 based on the pseudo inertial force.

[0012] The DC / AC inverter 100 converts direct current into alternating current and outputs it. The DC / DC converter 102 converts the direct current into a voltage value and outputs it. By using these inverters and converters, the power conversion unit 10 can convert the power stored in the power storage device 3 based on renewable energy into alternating current and output it to the microgrid 20 of the power system 2 as needed. As another example, instead of the power storage device 3, a renewable energy power generation device such as a solar power generation device or a wind power generation device may be connected.

[0013] In this embodiment, the PCS 4 includes a control unit 12 and a power conversion unit 10. As another non-limiting example, the PCS 4 may include at least the control unit 12 and the DC / AC inverter 100 of the power conversion unit 10. In addition, as another non-limiting example, the PCS 4 may include a display unit 14, an operation unit 16, and a communication unit 18.

[0014] The control unit 12 controls switching of the operation of the power conversion unit 10 based on a command from a higher-level control unit based on the state of the power system. The control unit 12 controls the output from the power conversion unit 10 by switching at an appropriate timing between a first mode, which is a power control mode in which the power conversion unit 10 performs a first operation, and a second mode, which is a power control mode in which the power conversion unit 10 performs a second operation.

[0015] The first mode is a power control mode in which a first operation not based on inertia force is performed, and in which grid stabilization control is not performed in the power conversion unit 10. When the power conversion unit 10 is controlled in the first mode, the power conversion unit 10 performs control according to a current control method for controlling the output current, for example, GFL. In the first mode, the control unit 12 performs control such that the rating is the first rating.

[0016] The second mode is a power control mode in which a second operation based on inertia force is performed, and is a mode in which the power conversion unit 10 performs grid stabilization control. When the power conversion unit 10 performs control in the second mode, the power conversion unit 10 changes the rating of the PCS according to at least one of the voltage control methods for controlling the output voltage, for example, VGS control, GFM, Frequency-Watt control, Volt-Watt control, Volt-var control, and Dynamic Volt-var control. For example, in the second mode, the power conversion unit 10 may output power by a single control among the above, or may output power by control within a range of two or more non-conflicting controls, such as VGS control and GFM control. In the second mode, the control unit 12 performs control such that the rating is the second rating.

[0017] Here, Frequency - Watt control is frequency-active power control that changes the active power output according to the system frequency. Volt - Watt control is voltage-active power control. Volt - var control is voltage-reactive power control. Dynamic Volt - var control is dynamic reactive power support control. These pseudo-inertia generating controls are executed in the second mode.

[0018] As an example, the first rating indicates a higher power or current than the second rating. Preferably, the first rating is 1.5 times or more the second rating. More preferably, the first rating is a value higher than 1.5 times the second rating by a minimum value that ensures safety. This 1.5 times is an optimum value in Japan based on the standards of JIS C 4034-1:1999 and JEC-2100-2008, and in countries with different laws or standards, this multiplier may preferably be an optimum value based on the laws or standards of the country.

[0019] The display unit 14 is a user interface that allows the user to view the state of control in the control unit 12. The display unit 14 includes, for example, a display.

[0020] The operation unit 16 is a user interface that enables a user to give instructions to the control unit 12. The operation unit 16 includes, for example, a mouse, a keyboard, a touch panel, buttons, and the like.

[0021] The communication unit 18 is an interface for transmitting and receiving information in the control unit 12 .

[0022] Commands from a higher-level control unit may be input directly to the control unit 12 via the communication unit 18, or may be input by the user via the operation unit 16.

[0023] (First embodiment) FIG. 2 is a flowchart showing the process of the control unit 12 in the power system operation system 1 according to an embodiment.

[0024] The upper control system checks the power supply information, weather, accident occurrence, and other conditions, and transmits a request to the power system operation system 1 to use / not use inertial force and at least one of an active power command value and a reactive power command value to the control unit 12 (S10). The control unit 12 receives the request and command value from the upper control system. The upper control system may transmit this information to the control unit 12 via the communication unit 18 in Fig. 1, or the user may input this information to the control unit 12 via the operation unit 16.

[0025] The upper control system can also transmit only the above request or only the above command value to the control unit 12. The control unit 12 can also switch the mode and rating based on only the received request or only the command value by the following process.

[0026] The control unit 12 judges whether the request received from the higher-level control system is to control with inertia force or to control without inertia force (S20).

[0027] If the request is for no inertia force (S20: none), the control unit 12 sets the output from the PCS 4 to the first mode and controls it (S21). In this way, when the control unit 12 receives a request for no inertia force, it selects the first mode in which power system stabilization control is not performed.

[0028] If the request indicates that there is an inertial force (S20: YES), the control unit 12 sets the output from the PCS 4 to the second mode and controls it (S21). In this way, when the control unit 12 receives a request that there is an inertial force, it selects the second mode in which grid stabilization control is performed.

[0029] After setting the first mode / second mode, the control unit 12 notifies the upper control system of the presence or absence of inertial force and the output and rated values ​​(S23). The control unit 12 may also notify the upper control system of the current power control mode.

[0030] FIG. 3 is a flowchart showing the details of the first mode (S21) process of FIG.

[0031] When the control unit 12 determines to control in the first mode, the control unit 12 checks the current power control mode (S210). If the current power control mode is the first mode (control without inertia force) (S210: first mode), the control unit 12 maintains the control in the first mode (S211).

[0032] When the current power control mode is the second mode (control with inertia force) (S210: second mode), the control unit 12 transitions and switches the power control mode to the first mode (S212).

[0033] After transitioning to the first mode, the control unit 12 determines whether or not at least one of the active power command value and the reactive power command value is higher than the first rating (S213). In other words, it determines whether or not both the active power command value and the reactive power command value are equal to or lower than the first rating.

[0034] When both of the command values ​​are equal to or less than the first rated value (S213: YES), the control unit 12 performs control to output power / current with the command values ​​set to the rated value (S214).

[0035] When at least one of the command values ​​is higher than the first rating (S213: NO), the control unit 12 performs control to output power / current according to the first rating (S215).

[0036] In this way, when controlling in the first mode, the control unit 12 controls the power output in accordance with a rating that does not exceed the first rating.

[0037] FIG. 4 is a flowchart showing the details of the second mode (S22) process of FIG.

[0038] When the control unit 12 determines to perform control in the second mode, the control unit 12 checks the current power control mode (S220). If the current power control mode is the second mode (control with inertia force) (S220: second mode), the control unit 12 maintains the control in the second mode (S221).

[0039] When the current power control mode is the first mode (control without inertia force) (S220: first mode), the control unit 12 transitions and switches the power control mode to the second mode (S222).

[0040] After transitioning to the second mode, the control unit 12 determines whether or not at least one of the active power command value and the reactive power command value is higher than the second rating (S223). In other words, it determines whether or not both the active power command value and the reactive power command value are equal to or lower than the second rating.

[0041] When both of the command values ​​are equal to or lower than the second rated value (S223: YES), the control unit 12 performs control to output power / current with the command values ​​set to the rated value (S224).

[0042] When at least one of the command values ​​is higher than the second rating (S223: NO), the control unit 12 performs control to output power / current according to the second rating (S225).

[0043] In order to execute more stable processing, the process of S222 may be executed after the process of S224 or the process of S225. In other words, the control unit 12 may set the rated value to a safe value, and then transition to the second mode to execute the grid stabilization control.

[0044] In this way, when controlling in the second mode, the control unit 12 controls the power output in accordance with a rating that does not exceed the second rating. As described above, the second rating may be, for example, a value that is 2 / 3 times or less of the first rating. By setting such a second rating, it becomes possible to fully withstand a current output that is 1.5 times the rated second rating in the second mode.

[0045] 2 to 4, when the control unit 12 receives a request to perform stabilization control while executing control in the first mode, the control unit 12 switches the power control mode from the first mode to the second mode. Similarly, when the control unit 12 receives a request not to perform stabilization control while executing control in the second mode, the control unit 12 switches the power control mode from the second mode to the first mode.

[0046] As shown in S23 of Fig. 2, the control unit 12 notifies the upper control system that the mode has been switched. In particular, when transitioning from the second mode to the first mode after an abnormality such as a system accident occurs (switching to the second mode), the control unit 12 notifies the upper control system that it has switched to the first mode, which is the normal operation mode. By making such a notification, when an abnormality occurs, the upper control system can promptly request the control unit 12 to switch control to the abnormal operation mode.

[0047] As described above, according to the present embodiment, a configuration can be achieved that can temporarily withstand a current exceeding the rated current in the second mode. The power system operation system 1 has a circuit configuration that can withstand, for example, a first rated output, which is about 1.5 times the second rated output, in the second mode. Therefore, even if an abnormality such as a system accident occurs, the power system operation system 1 can switch from the first mode, which is a normal control that does not use inertia force, to the second mode that uses inertia force, and can maintain an output equivalent to the first rated output that does not cause malfunctions such as element destruction.

[0048] Second Embodiment Fig. 5 is a flowchart showing a part of the control of the PCS 4 according to one embodiment. In addition to the configuration of Fig. 2, a comparison process between a command value and a predetermined threshold value is added. The processes with the same reference numerals as those in Fig. 2 are the same processes unless otherwise specified, and therefore the explanation will be omitted.

[0049] Before transitioning to the second mode, the control unit 12 compares the command value with a predetermined threshold value (S24). Here, the predetermined threshold value is a value lower than the first rating. The predetermined threshold value may be a value that satisfies, for example, (first rating)>1.5×(predetermined threshold value). Furthermore, the predetermined threshold value may be a value higher than the second rating value, or may be the same value as the second rating value.

[0050] If the command value is equal to or smaller than the predetermined threshold value (S24: YES), the control unit 12 sets the power control mode to the second mode (S22), as in the previous embodiment.

[0051] When the command value is higher than the predetermined threshold value (S24: NO), the control unit 12 sets the power control mode to the first mode in which the grid stabilization control is not performed.

[0052] The order of the processes in S20 and S24 may be reversed. The control unit 12 may compare the command value with the threshold value to set the first mode or select a state in which the mode is not limited, and when the mode is not limited, determine whether or not to perform the grid stabilization control.

[0053] By the above-described processing, in this embodiment, in the event of a system fault, it becomes possible to pass a current exceeding this predetermined threshold value up to the first rated current.

[0054] In this embodiment, the second rating and the predetermined threshold value can be set to the same value. In this case, in the processing of the second mode shown in FIG. 4, the processing of S223 and S225 can be omitted and the command value can be used as the rating for control. In the second mode, it is possible to realize system control in a safe state based on the command value without defining the second rating. That is, the processing of S22 in this embodiment may be the same as that in the first embodiment, or may be a processing without S223 and S225.

[0055] Fig. 6 is a flow chart showing another example of the process according to this embodiment. The control unit 12 may perform the same mode selection process as in Fig. 2, and before entering the process of the second mode, may compare the command value with a threshold value in S226 to select whether to switch to the first mode, maintain the first mode, or transition to the second mode. In this case as well, by appropriately setting the predetermined threshold value, the output in the second mode will not exceed the first rated output, so the processes of S223 and S225 may not be necessary. Of course, the processes of S223 and S225 are not excluded, and these processes may be executed.

[0056] (Third embodiment) Fig. 7 is a flowchart showing a part of the control of the PCS according to one embodiment. In this embodiment, when the control unit 12 receives a request to transition from the first mode to the second mode from a higher-level control system, the control unit 12 updates the second rating based on the received command value and then transitions to the second mode. The predetermined threshold value is a value smaller than the first rating.

[0057] When the control unit 12 receives a request for power system stabilization control in the process of Fig. 2, it executes the process of S22 shown in Fig. 7. When the control unit 12 determines that the mode is the first mode (S220: first mode), it compares the command value with a predetermined threshold value (S226).

[0058] If the command value is equal to or smaller than the predetermined threshold value (S226: YES), the control unit 12 sets the command value to the rated value (S227) and transitions to the second mode (S222).

[0059] If the command value is higher than the predetermined threshold value, the control unit 12 sets a value equal to or lower than the predetermined threshold value as the rated value (S228), and transitions to the second mode (S222).

[0060] According to this embodiment, when performing grid stabilization control, the PCS can set a rated current that allows safe operation. For example, by setting the predetermined threshold to 2 / 3 of the first rated current, the PCS can be configured to withstand a current output 1.5 times the rated current in the second mode.

[0061] (Fourth embodiment) Fig. 8 is a flow chart showing a part of the control of the PCS according to one embodiment. In this embodiment, when the control unit 12 receives a request to transition from the first mode to the second mode from a higher-level control system, the control unit 12 executes a process including a case where the mode is not transitioned to the second mode according to the received command value. The predetermined threshold value is the same as in each of the above-mentioned embodiments.

[0062] When the control unit 12 receives a request to transition to the second mode and the current mode is the first mode (S220: first mode), the control unit 12 compares the command value with a predetermined threshold value (S226). If the command value is less than or equal to the threshold value (S226: YES), the control unit 12 executes a process according to any one of the above-described embodiments (e.g., S227).

[0063] If the command value is higher than the predetermined threshold value (S226: NO), the control unit 12 maintains the first mode regardless of an instruction from the higher-level control system (S229).

[0064] According to the present embodiment as well, in the case of operation using the power system stabilization control, safe operation can be performed by appropriately selecting the first mode and the second mode.

[0065] In each of the above embodiments, the power conversion unit 10 in FIG. 1 receives at least one of virtual synchronous control (VGS control) and grid formation control (GFM) instructions from the control unit 12 from a higher-level control system, and performs power conversion based on the instructions from the control unit 12.

[0066] (Implementation example) A plurality of PCSs according to the above-described embodiments may be connected to the same upper control system. The upper control system may be provided corresponding to the microgrid 20 of Fig. 1, for example. In this case, the PCSs may have different ratings.

[0067] The upper control system can also control the allocation of active power command values ​​to each PCS based on the different ratings of the multiple PCSs depending on the presence or absence of a system support function, i.e., switching between the first and second modes, or other system switching functions.

[0068] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0069] 1: Power system operation system, 10: Power conversion section, 100: DC / AC inverter, 102: DC / DC converter, 12: Control section, 14: Display section, 16: Operation section, 18: Communications Department, 2: Power system, 3: Energy storage device; 4: PCS

Claims

1. A control circuit is provided, The control circuit includes: The power control mode can be switched between a first mode in which an operation is not based on inertia force and a second mode in which an operation is based on inertia force; In the first mode, output control is performed according to a first rating; In the second mode, the output is controlled according to a second rating different from the first rating; the first mode is a current control method for controlling an output current; the second mode is a voltage control method for controlling an output voltage; the first rating is greater than the second rating; Power conditioner.

2. said first rating being equal to or greater than 1.5 times said second rating; The power conditioner according to claim 1.

3. In the first mode, the control circuit switching the power control mode from the first mode to the second mode when a request to perform an action based on the inertial force is received; The power conditioner according to claim 1 or 2.

4. In the second mode, the control circuit switching the power control mode from the second mode to the first mode when a request to perform an operation not based on the inertial force is received; A power conditioner according to any one of claims 1 to 3.

5. The control circuit includes: when the power control mode is switched from the second mode to the first mode, notifying the switching; The power conditioner according to claim 4.

6. The control circuit includes: receiving at least one of an active power command value and a reactive power command value; A power conditioner according to any one of claims 1 to 5.

7. In the first mode, the control circuit When the command value is higher than the first rating, the output is controlled according to the first rating; When the command value is equal to or less than the first rated value, output control is performed in accordance with the command value. The power conditioner according to claim 6.

8. In the second mode, the control circuit When the command value is higher than the second rating, output control is performed according to the second rating; When the command value is equal to or less than the second rated value, output control is performed in accordance with the command value. The power conditioner according to claim 6 or 7.

9. A control circuit is provided, The predetermined threshold value is set to a value lower than the first rating, The control circuit includes: The power control mode can be switched between a first mode in which an operation is not based on inertia force and a second mode in which an operation is based on inertia force; Receive at least one of an active power command value and a reactive power command value; In the first mode, output control is performed according to the first rating; When the command value is higher than the predetermined threshold value, the power control mode is changed to the first mode. the first mode is a current control method for controlling an output current; the second mode is a voltage control method for controlling an output voltage, and is a mode for controlling an output according to a second rating; the first rating is greater than the second rating; Power conditioner.

10. A control circuit is provided, The predetermined threshold value is set to a value lower than the first rating, The control circuit includes: The power control mode can be switched between a first mode in which an operation is not based on inertia force and a second mode in which an operation is based on inertia force; Receive at least one of an active power command value and a reactive power command value; In the first mode, Controlling the output in accordance with the first rating; when receiving a request to perform an operation based on an inertial force and the command value higher than the predetermined threshold, a value equal to or lower than the predetermined threshold is set as a second rating; switching the power control mode to the second mode in which output control is performed in accordance with the second rating; the first mode is a current control method for controlling an output current; the second mode is a voltage control method for controlling an output voltage; the first rating is greater than the second rating; Power conditioner.

11. A control circuit is provided, The predetermined threshold value is set to a value lower than the first rating, The control circuit includes: The power control mode can be switched between a first mode in which an operation is not based on inertia force and a second mode in which an operation is based on inertia force; Receive at least one of an active power command value and a reactive power command value; In the first mode, output control is performed according to the first rating; when a request to perform an operation based on an inertial force and the command value is higher than the predetermined threshold value are received in the first mode, the power control mode is not switched to the second mode; the first mode is a current control method for controlling an output current; the second mode is a voltage control method for controlling an output voltage, and is a mode for controlling an output according to a second rating; the first rating is greater than the second rating; Power conditioner.

12. A power conversion unit is further provided, The control circuit includes: outputting a signal for driving the power conversion unit in accordance with at least one of instructions of virtual synchronous control or grid formation type control from a higher level control system; The power conversion unit is converting power based on the signal received from the control circuit; A power conditioner according to any one of claims 1 to 11.

13. One or more power conditioners, including at least one power conditioner according to any one of claims 1 to 12; A host control unit; Equipped with The upper control unit is Controlling the distribution of active power command values ​​according to the different ratings of the one or more power conditioners depending on the presence or absence of a grid support function; Power system operation system.

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