Control device and control method

Abstract

This provides more reliable protection for three-phase AC generators in microgrids than conventional methods. [Solution] A control device (30) that controls a three-phase AC generator (20) in a microgrid (1) calculates an equivalent reverse-sequence current flowing into the generator (20) based on a measurement of a predetermined harmonic component of the current flowing into the generator (20), and performs a protective operation to protect the generator (20) based on the calculated equivalent reverse-sequence current.

Description

Technical Field

[0001] One aspect of the present invention relates to a control device for controlling a three-phase AC generator in a microgrid.

Background Art

[0002] Various technologies related to microgrids have been proposed. For example, the following Patent Document 1 discloses a technology aimed at preventing reverse power flow to a generator during autonomous operation of a microgrid.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of one aspect of the present invention is to more reliably protect a three-phase AC generator in a microgrid than before.

Means for Solving the Problems

[0005] A control device according to one aspect of the present invention is a control device for controlling a three-phase AC generator in a microgrid, which calculates an equivalent reverse-phase current flowing into the generator based on a measured value of a harmonic component of a predetermined order of the current flowing into the generator, and executes a protection operation for protecting the generator based on the calculated equivalent reverse-phase current.

[0006] A control method according to one aspect of the present invention is a control method for controlling a three-phase AC generator in a microgrid, comprising the steps of: calculating an equivalent reverse-sequence current flowing into the generator based on measured values ​​of a predetermined order harmonic component of the current flowing into the generator; and performing a protective operation to protect the generator based on the calculated equivalent reverse-sequence current. [Effects of the Invention]

[0007] According to one aspect of the present invention, a three-phase AC generator in a microgrid can be protected more reliably than in the conventional method. [Brief explanation of the drawing]

[0008] [Figure 1] This shows an example of a microgrid configuration in Embodiment 1. [Figure 2] Figure 1 illustrates a simplified equivalent circuit in which the inverter load and energy storage device in the microgrid are each represented as separate current sources. [Modes for carrying out the invention]

[0009] [Embodiment 1] The microgrid 1 in Embodiment 1 will be described below. For the sake of clarity, components having the same function as those described in Embodiment 1 will be denoted by the same reference numerals in subsequent embodiments, and their descriptions will not be repeated. For the sake of simplicity, explanations of known technical matters will also be omitted as appropriate.

[0010] In this specification, each component and each numerical value is, to the extent that it does not contradict the content, merely illustrative. Therefore, to the extent that it does not contradict the content, the positional and connection relationships of each component, for example, are not limited to the examples in each figure. In this specification, the term "connected" means "electrically connected" to the extent that it does not contradict the content.

[0011] (Example configuration of microgrid 1) Figure 1 shows an example configuration of microgrid 1. In Figure 1, a three-phase AC system is schematically shown in a single-line diagram. Microgrid 1 is connected to an external commercial power supply PW via a switch SW. The commercial power supply PW is, for example, the power supply of a power company. The commercial power supply PW supplies AC power at commercial frequency (e.g., 60Hz) to each part of the power system, including microgrid 1.

[0012] In the example shown in Figure 1, the microgrid 1 comprises a power storage device 10, a generator 20, and a control device 30. In the example shown in Figure 1, the power storage device 10, the generator 20, and the control device 30 are located inside the electrical equipment EE.

[0013] In addition, the microgrid 1 in the example of Figure 1 is equipped with one or more inverter loads LD. The inverter loads LD may be of any type, as long as they are loads that include an inverter. In this specification, an inverter means a device that converts direct current electricity to alternating current electricity. That is, the inverter may be any type of DC / AC converter.

[0014] Figure 1 illustrates two inverter loads LD. To distinguish between the two inverter loads LD, one inverter load LD will be denoted as inverter load LD-1, and the other inverter load LD will be denoted as inverter load LD-2.

[0015] Point P1 in Figure 1 is the connection point between inverter load LD-1 and the transmission line of microgrid 1. Point P2 is the connection point between inverter load LD-2 and the transmission line. Point P3 is the connection point between electrical equipment EE and the transmission line.

[0016] Switch SW is located at the connection point between microgrid 1 and commercial power supply PW. In the example in Figure 1, point P1 is the closest to switch SW among points P1 to P3. On the other hand, point P3 is the furthest from switch SW among points P1 to P3. Point P2 is located between points P1 and P3.

[0017] When there is no abnormality in the commercial power supply PW (hereinafter referred to as "normal operation"), the switch SW is in the ON (conducting) state. On the other hand, when an abnormality occurs in the commercial power supply PW (hereinafter referred to as "abnormal operation"), the switch SW is turned off, and the microgrid 1 is disconnected from the commercial power supply PW. Therefore, in the event of an abnormality, the microgrid 1 (particularly the energy storage device 10 and the generator 20) operates independently and supplies power to each load within the microgrid 1 (e.g., the inverter load LD in Figure 1).

[0018] In the example in Figure 1, the microgrid 1 comprises transformers TR1 and TR2. Transformers TR1 and TR2 may also be referred to as the first transformer and the second transformer, respectively. In the example in Figure 1, transformers TR1 and TR2 are located inside the electrical installation EE. The current sensor SR in Figure 1 will be described later. Point P4 is a branching point of the circuit within the electrical installation EE. Transformers TR1 and TR2 are connected in parallel to each other via point P4. Point P4 is connected to point P3.

[0019] Therefore, the primary sides of transformers TR1 and TR2 are connected to point P3 via point P4. The secondary side of transformer TR1 is connected to the energy storage device 10. For this reason, transformer TR1 may be referred to as a transformer for the energy storage device. The secondary side of transformer TR2 is connected to the generator 20. For this reason, transformer TR2 may be referred to as a transformer for the generator.

[0020] In the example in Figure 1, the rated voltages of the primary sides of transformers TR1 and TR2 are equal to the rated voltage of the power system including microgrid 1 (e.g., 6600V). The rated voltages of the secondary sides of transformers TR1 and TR2 are equal to the rated voltage of generator 20 (e.g., 440V).

[0021] The energy storage device 10 includes a battery 11 and an inverter 12. For example, the battery 11 discharges DC power. The inverter 12 then converts the DC power output from the battery 11 into AC power. This allows the energy storage device 10 to output AC power externally. For example, in the event of a malfunction, power is supplied from the energy storage device 10 to the power transmission lines of the microgrid 1 via the transformer TR1.

[0022] Battery 11 can also be charged with DC power. For example, under normal circumstances, battery 11 may be charged by power being supplied to the energy storage device 10 from the transmission lines of the microgrid 1 via transformer TR1. Therefore, the energy storage device 10 may have an AC / DC converter (not shown) that converts AC power to DC power.

[0023] The generator 20 can be any three-phase AC generator. Embodiment 1 illustrates the case where the generator 20 is an emergency generator. In the example in Figure 1, the generator 20 operates under the control of the control device 30. For example, in the event of a malfunction, power is supplied from the generator 20 to the power transmission line of the microgrid 1 via the transformer TR2. Therefore, for example, if the power output from the energy storage device 10 is insufficient during independent operation, the generator 20 can compensate for the power shortage.

[0024] (Consideration of harmonic currents) The inverter generates harmonic currents. Therefore, harmonic currents are output from each of the two inverter loads LD in Figure 1. As a result, harmonic currents flow from each of the two inverter loads LD to the generator 20. Also, as mentioned above, the energy storage device 10 includes an inverter 12. Therefore, for example, harmonic currents also flow from the energy storage device 10 to the generator 20.

[0025] As described above, the inverter load LD and the energy storage device 10 in the microgrid 1 can act as current sources. It is known that harmonic currents flowing into certain electrical equipment may adversely affect that equipment. For example, if a sufficiently large harmonic current flows into the generator 20, the rotor of the generator 20 may overheat.

[0026] Next, with reference to Figure 2, we will examine the harmonic currents in the microgrid 1 in more detail. Figure 2 illustrates a simplified equivalent circuit in which the inverter load LD and the energy storage device 10 in the microgrid 1 are each represented as separate current sources.

[0027] In Figure 2, current sources CS1 and CS2 correspond to inverter loads LD-1 and LD-2, respectively. Current source CS3 corresponds to the energy storage device 10. In the example in Figure 2, current sources CS1 to CS3 are connected in parallel.

[0028] In Figure 2, impedance ZS represents the impedance of the commercial power supply PW, and impedance ZG represents the impedance of the generator 20. In the example in Figure 2, impedances ZS and ZG are connected in parallel to each other. Impedances ZS and ZG are also connected in parallel to the current sources CS1 to CS3. Capacitor 40 in Figure 2 will be discussed later. First, let's explain the relationship between impedances ZS and ZG.

[0029] In Figure 2, the symbol 210 illustrates the flow of harmonic current under normal conditions. As shown in the example of symbol 210, under normal conditions, the harmonic currents flowing out from current sources CS1 to CS3 flow into impedances ZS and ZG.

[0030] However, in a typical power grid, the rated capacity of the commercial power supply PW is significantly larger than the rated capacity of the generator 20. Therefore, the impedance ZS is significantly smaller than the impedance ZG. Consequently, under normal conditions, most of the harmonic currents flowing out from the current sources CS1 to CS3 flow into impedance ZS.

[0031] In other words, under normal conditions, not much harmonic current flows into the impedance ZG. Therefore, under normal conditions, the harmonic current flowing from the inverter load LD and the energy storage device 10 to the generator 20 is not a significant problem.

[0032] In Figure 2, the symbol 220 illustrates the flow of harmonic current during an abnormal condition. The example of symbol 220 is paired with the example of symbol 210 described above. As described above, during an abnormal condition, the commercial power supply PW is disconnected from the microgrid 1. Therefore, as shown in the example of symbol 220, during an abnormal condition, the impedance ZS is disconnected from the current sources CS1 to CS3.

[0033] Therefore, in the event of an abnormality, unlike normal conditions, a significant portion of the harmonic currents flowing out from current sources CS1 to CS3 may flow into impedance ZG. For this reason, in the event of an abnormality, attention should be paid to the harmonic currents flowing from the inverter load LD and the energy storage device 10 to the generator 20.

[0034] Incidentally, in microgrid 1, a capacitor for phase adjustment may be provided, for example. Therefore, Figure 2 illustrates a case where capacitor 40 is connected in parallel to impedances ZS and ZG.

[0035] In a typical power grid, the rated capacity of the commercial power supply PW is sufficiently large compared to the rated capacity of capacitor 40. Therefore, the impedance ZS is sufficiently small compared to the impedance of capacitor 40. Consequently, under normal circumstances, not much harmonic current flows into capacitor 40.

[0036] On the other hand, in the event of a malfunction, a significant portion of the harmonic currents flowing out from the current sources CS1 to CS3 may flow into the capacitor 40. For this reason, in the event of a malfunction, attention should also be paid to the harmonic currents flowing into the capacitor 40 from the inverter load LD and the energy storage device 10.

[0037] Therefore, in order to protect each electrical device in the microgrid 1, it is desirable to quantitatively evaluate the effect of harmonic currents on each electrical device. Embodiment 1 describes the protection of the generator 20.

[0038] As an example, the effect of harmonic currents on the generator 20 can be quantitatively evaluated by the equivalent reverse-sequence current flowing into the generator 20. In this specification, the equivalent reverse-sequence current is defined as I 2eq This is how it is written. 2eq This is given by the following equation (1),

number

[0039] It is known that among the harmonic components, components of order that are multiples of 6 tend to affect the generator 20. And when ν is a multiple of 6, I ν This is given by equation (2) below, I ν =I ν-1 +I ν+1 …(2) It is known that it can be represented by [this].

[0040] However, measuring harmonic components of very high order is not easy. Therefore, as an example, in Embodiment 1, we consider ν in the range ν ≤ 13. First, by substituting ν = 6 into equation (2) above, I6 = I5 + I7 ... (3 - 1) is obtained. Next, by substituting ν = 12 into Equation (2), I 12 = I 11 + I 13 …(3-2) is obtained.

[0041] In the above Equation (1), focus on the terms of ν = 6 and ν = 12. Next, by substituting Equation (3-1) and Equation (3-2) into the said Equation (1), the following Equation (4),

Equation

[0042] As can be understood from the above explanations, in the microgrid 1, by obtaining the measured value of the harmonic component of a predetermined order of the current flowing into the generator 20 (the measured value of I ν ), it becomes possible to calculate I 2eq flowing into the generator 20 based on the said measured value.

[0043] Therefore, the microgrid 1 in the example of FIG. 1 includes a current sensor SR for detecting the said harmonic component. Thereby, in the microgrid 1, it becomes possible to calculate I 2eq in real time. The current sensor SR may be located on the path where the current flows from each of the above current sources (e.g., the inverter load LD and the power storage device 10) to the generator 20. In the example of FIG. 1, the current sensor SR is located between the point P4 and the transformer TR2 inside the electrical equipment EE.

[0044] The current sensor SR in Embodiment 1 detects I5 (5th harmonic component), I7 (7th harmonic component), I 11 (11th harmonic component), and I 13 (13th harmonic component) for at least one phase of the current flowing into the generator 20. In Embodiment 1, for the sake of clarity of explanation, the harmonic components in a certain one phase are described. As the current sensor SR, for example, a digital multimeter can be used.

[0045] The control device 30 controls various parts of the electrical equipment EE. Embodiment 1 describes the case where the control device 30 controls the generator 20. In the example in Figure 1, the control device 30 has a reverse-phase current calculation unit 31 and a determination unit 32.

[0046] The reverse-phase current calculation unit 31 calculates the above-mentioned I5, I7, I from the current sensor SR. 11 , and I 13 The reverse-phase current calculation unit 31 obtains the obtained I5, I7, I 11 , and I 13 Using this, according to equation (4) above, I 2eq Calculate.

[0047] In Embodiment 1, from the viewpoint of protecting the generator 20, 2eq A predetermined threshold is set for this. In this specification, the threshold is defined as I 2eq_th This is how it is written. 2eq_th This can be arbitrarily set by, for example, the designer of microgrid 1.

[0048] For example, I 2eq_th This may be set based on any technical standard concerning the protection of generators. Some technical standards specify the I for each type of generator. 2eq The upper limit (permissible value) is defined as the value obtained by multiplying the rated current of the generator by a predetermined coefficient (multiplier) α. In this specification, the rated current is defined as I rate This is written as, and the upper limit is I 2eq_max This is how it is written.

[0049] Therefore, in Embodiment 1, I 2eq_max teeth, I 2eq_max =α×I rate …(5) It can be expressed as follows. α may also be called the tolerance. α may be arbitrarily determined according to the technical standard. In Embodiment 1, α is defined such that 0 < α < 1. Embodiment 1 exemplifies the case where α = 0.15. In this case, I 2eq_maxThis is determined as 15% of the rated current of the generator 20.

[0050] And I 2eq_th is, I 2eq_max It may be set based on the above. For example, I 2eq_th is, I 2eq_max It may be determined as a value obtained by multiplying by a predetermined coefficient β. Therefore, in Embodiment 1, I 2eq_th This is given by equation (6) below, I 2eq_th =β×I 2eq_max …(6) It can be expressed as follows.

[0051] β may also be called the safety factor. β may be arbitrarily determined by the designer of microgrid 1. In Embodiment 1, β is set such that 0 < β < 1. By introducing this β, I 2eq_max I exceed 2eq However, the risk of it flowing into the generator 20 can be reduced more reliably. Embodiment 1 illustrates the case where β = 0.9. In this case, I 2eq_th is, I 2eq_max It is defined as the 90th percentile.

[0052] According to equations (5) and (6) above, I 2eq_th This is given by equation (7) below, I 2eq_th =α×β×I rate …(7) It can also be expressed as follows. In Embodiment 1, α × β = 0.135. Therefore, I 2eq_th This is determined as 13.5% of the rated current of the generator 20.

[0053] In Embodiment 1, the control device 30 calculates I 2eq Based on this, protective actions are performed to protect the generator 20. This ensures that in the microgrid 1, 2eq Based on this, the generator 20 can be protected in real time. The determination unit 32 determines whether or not to perform a protective operation. For example, the determination unit 32 determines I 2eq and I2eq_th Based on the comparison results, a decision may be made as to whether or not to perform a protective action.

[0054] In Embodiment 1, the determination unit 32 determines the I calculated by the reverse-phase current calculation unit 31. 2eq However, I 2eq_th Determine whether it exceeds the limit. 2eq I 2eq_th If the value exceeds this limit, the determination unit 32 performs a protective action to protect the generator 20.

[0055] Embodiment 1 illustrates a case where the protective action is an action that outputs a command to stop the generator 20. In Embodiment 1, the determination unit 32 is I 2eq I 2eq_th If it exceeds this value, the command is output to the generator 20. Therefore, I 2eq I 2eq_max Before reaching that point, the generator 20 can be stopped.

[0056] (Specific example) As an example, consider a case where the rated voltage of microgrid 1 is 6600V and the rated capacity of generator 20 is 135kVA. In this example, we will describe the current values ​​converted to 6600V.

[0057] First, by using equation (5) above, I 2eq_max Regarding this, see equation (8) below.

number

[0058] Therefore, the determination unit 32 in this example is I 2eq If the current exceeds 1.60A, a command to stop the generator 20 is output to the generator 20. In this example, 2eq Before reaching 1.77A, I 2eqThe generator 20 can be stopped when the current reaches 1.60A.

[0059] (Effects of Microgrid 1) As described above, the control device 30 in the microgrid 1 measures the measured values ​​of predetermined harmonic components (e.g., I5, I7, I) flowing into the generator 20. 11 , and I 13 The current sensor SR obtains the following value. The control device 30 then uses the measurement value obtained from the current sensor SR to determine the current value. 2eq Next, the control device 30 calculates the calculated I 2eq Based on this, protective actions are performed to protect the generator 20.

[0060] "I based on the measurement of harmonic components" 2eq "Calculation of" and "Calculated I 2eq Attempts to perform a series of processes for monitoring and controlling generators based on in real time have not been made in existing microgrids. For example, in the above-mentioned Patent Document 1, 2eq The harmonic components that form the basis of the calculation are not mentioned at all.

[0061] Therefore, the control device 30 makes it possible to protect the generator 20 in the microgrid 1 more reliably than before. For example, as described above, the control device 30 makes it possible to protect the generator 20 in the microgrid 1 more reliably than before. 2eq I 2eq_th If it exceeds this limit, protective action can be performed. 2eq I 2eq_max Before that happens, the generator 20 can be protected.

[0062] Incidentally, in microgrid 1, due to constraints such as the cost and installation space of the generator 20, a relatively small-capacity generator is often selected as the generator 20. For this reason, in microgrid 1, a larger-capacity energy storage device 10 is often selected than the capacity of the generator 20.

[0063] If the capacity of the energy storage device 10 is larger than the capacity of the generator 20, the harmonic currents flowing from the energy storage device 10 to the generator 20 can have a significant impact on the generator 20. For this reason, the generator 20 protection method described in Embodiment 1 is suitable for the microgrid 1.

[0064] [Embodiment 2] (1) In Embodiment 1, an example of a protective action was shown in which a command to stop the generator 20 is output. However, the protective action according to one aspect of the present invention is not limited to this example. As another example, the protective action may be an action that outputs information (alert information) indicating that there is a sign of an abnormality in the generator.

[0065] (2) Embodiment 1 illustrates a case in which the control device 30 outputs a command to the generator 20 to stop it. However, the control device 30 may output the command to a component other than the generator 20 (e.g., a protective relay not shown located upstream of the generator 20). In other words, the control device 30 may stop the generator 20 via that component.

[0066] (3) The protection operation according to one aspect of the present invention may be an operation that controls a device other than the generator 20. As described above, in the microgrid 1, the capacity of the energy storage device 10 is often larger than the capacity of the generator 20. For this reason, in the microgrid 1, harmonic currents flowing from the energy storage device 10 to the generator 20 can have a significant impact on the generator 20. For example, the protection operation may be an operation that outputs a command to control the operation of the energy storage device 10.

[0067] For example, the protective action may be an action that outputs a command to stop the operation of at least one component of the energy storage device 10. Therefore, for example, the control device 30 may output a command to the energy storage device 10 to stop the operation of the battery 11. Alternatively, the control device 30 may output a command to the energy storage device 10 to stop the operation of the inverter 12.

[0068] By stopping (setting to zero) the output of the energy storage device 10, the harmonic currents flowing from the energy storage device 10 to the generator 20 can be eliminated. As a result, in the event of a malfunction in the microgrid 1, the generator 20 can be protected while continuing to operate independently. In other words, power can be supplied from the generator 20 to each load in the microgrid 1 (e.g., inverter load LD in Figure 1) while protecting the generator 20.

[0069] As yet another example, the protective action may be an action that outputs a command to limit the output of the energy storage device 10 to a predetermined non-zero value. Therefore, the control device 30 may output such command to the energy storage device 10. This predetermined value may be set, for example, based on the capacity of the energy storage device 10 and the capacity of the generator 20.

[0070] By limiting the output of the energy storage device 10, the harmonic currents flowing from the energy storage device 10 to the generator 20 can be reduced. In this way, even in the event of a malfunction in the microgrid 1, it is possible to protect the generator 20 while allowing both the energy storage device 10 and the generator 20 to continue operating independently. In this case, power can be supplied to each load in the microgrid 1 from both the energy storage device 10 and the generator 20 while protecting the generator 20.

[0071] (4) The microgrid 1 may be provided with another current sensor that measures the harmonic components of the current flowing into the capacitor 40. In this case, the control device 30 can calculate the equivalent reverse-phase current flowing into the capacitor 40 based on the measurement value of the other current sensor. Therefore, the control device 30 can protect the capacitor 40 more reliably than in the conventional method.

[0072] [Examples of implementation using software] The function of the microgrid 1 (hereinafter referred to as the "device" for convenience) is a program that causes the device to function as a computer, and can be realized by a program that causes each control block of the device (in particular, each part included in the control device 30) to function as a computer.

[0073] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., memory) as hardware for executing the program. By executing the program using this control device and storage device, the functions described in each of the embodiments are realized.

[0074] The above program may be recorded on one or more computer-readable recording media, not temporary ones. These recording media may or may not be provided by the above device. In the latter case, the program may be supplied to the above device via any wired or wireless transmission medium.

[0075] Furthermore, some or all of the functions of each of the above control blocks can also be realized by logic circuits. For example, an integrated circuit in which logic circuits functioning as each of the above control blocks are formed is also included in one aspect of the present invention. In addition, it is also possible to realize the functions of each of the above control blocks by, for example, a quantum computer.

[0076] Each of the processes described in the above embodiments may be performed by AI (Artificial Intelligence). In this case, the AI ​​may operate on the control device described above, or it may operate on other devices (e.g., an edge computer or a cloud server).

[0077] 〔summary〕 A control device according to Embodiment 1 of the present invention is a control device for controlling a three-phase AC generator in a microgrid, which calculates an equivalent reverse-sequence current flowing into the generator based on a measurement of a predetermined order harmonic component of the current flowing into the generator, and performs a protective operation to protect the generator based on the calculated equivalent reverse-sequence current.

[0078] In the control device according to aspect 2 of the present invention, the protection operation may be performed when the calculated equivalent reverse-sequence current exceeds a threshold value in aspect 1.

[0079] In the control device according to embodiment 3 of the present invention, in embodiment 1 or 2, the protection operation may be an operation that outputs a command to stop the generator.

[0080] In the control device according to aspect 4 of the present invention, in any one of aspects 1 to 3, the microgrid may include an energy storage device connected in parallel with the generator, and the energy storage device may include a battery and an inverter.

[0081] In the control device according to aspect 5 of the present invention, in aspect 4, the capacity of the energy storage device may be larger than the capacity of the generator.

[0082] In the control device according to embodiment 6 of the present invention, in any one of embodiments 1 to 5, the microgrid may be equipped with an inverter load connected in parallel with the generator.

[0083] In any one of embodiments 1 to 6, the control device according to embodiment 7 of the present invention may calculate the equivalent inverse-sequence current based on measured values ​​of the 5th harmonic component, 7th harmonic component, 11th harmonic component, and 13th harmonic component of the current.

[0084] A control method according to aspect 8 of the present invention is a control method for controlling a three-phase AC generator in a microgrid, comprising the steps of: calculating an equivalent reverse-sequence current flowing into the generator based on measured values ​​of a predetermined order harmonic component of the current flowing into the generator; and performing a protective operation to protect the generator based on the calculated equivalent reverse-sequence current.

[0085] [Additional Notes] One aspect of the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of one aspect of the present invention. [Explanation of Symbols]

[0086] 1 Microgrid 10 Energy storage device 11 batteries 12 Inverters 20 Generators 30 Control device 31. Inverse-phase current calculation unit 32 Judgment section LD Inverter Load

Claims

1. A control device for controlling a three-phase AC generator in a microgrid, Based on the measured values ​​of the harmonic components of a predetermined order of the current flowing into the generator, the equivalent reverse-sequence current flowing into the generator is calculated. A control device that performs a protective action to protect the generator based on the calculated equivalent reverse-sequence current.

2. The control device according to claim 1, wherein the protection operation is performed when the calculated equivalent reverse-sequence current exceeds a threshold.

3. The control device according to claim 1, wherein the protection operation is an operation to output a command to stop the generator.

4. The microgrid includes an energy storage device connected in parallel to the generator, The control device according to claim 1, wherein the energy storage device comprises a battery and an inverter.

5. The control device according to claim 4, wherein the capacity of the energy storage device is larger than the capacity of the generator.

6. The control device according to claim 1, wherein the microgrid includes an inverter load connected in parallel with the generator.

7. The control device according to claim 1, which calculates the equivalent inverse-phase current based on measured values ​​of the 5th harmonic component, 7th harmonic component, 11th harmonic component, and 13th harmonic component of the current.

8. A control method for controlling a three-phase AC generator in a microgrid, The steps include: calculating the equivalent reverse-sequence current flowing into the generator based on the measured values ​​of the harmonic components of a predetermined order of the current flowing into the generator; A control method comprising the step of performing a protective action to protect the generator based on the calculated equivalent reverse-sequence current.

Images