JP7259976B2 - Controller, system, control method and program - Google Patents

Description

The present invention relates to a control device, system, control method and program.

Conventionally, various control methods have been proposed in a power system in which power is transferred between a DC/DC converter connected to a DC power supply such as a solar power generation device and an inverter (see, for example, Patent Document 1). ).
Patent Document 1: JP-A-2014-171359 Patent Document 2: JP-A-2016-158434 Patent Document 3: JP-A-2016-220480

Problem to be solved

However, in the conventional technology, there is a possibility that an overvoltage may occur between the DC/DC converter and the inverter due to system failure or the like.

General disclosure

In order to solve the above problems, a first aspect of the present invention provides a control device. The control device includes a plurality of DC/DC converters respectively provided between a DC bus maintained at a reference voltage by transferring power to and from the inverter and a plurality of DC power sources supplying DC power to the DC bus. may comprise a first control unit that controls at least one of The control device may include a voltage measuring unit that measures the voltage of the DC bus. The first controller may reduce the output power of only some of the plurality of DC/DC converters when the voltage of the DC bus exceeds a threshold voltage higher than the reference voltage.

The first control unit may control one corresponding DC/DC converter among the plurality of DC/DC converters.

The control device may further include a changing unit that changes the threshold voltage over time.

The first control unit may reduce the output power of the corresponding DC/DC converter when the duration time during which the voltage of the DC bus exceeds the threshold voltage exceeds the upper limit time. The control device may further include a changing unit that changes the upper limit time over time.

In a second aspect of the invention, a system is provided. The system may include an inverter that receives power from and receives power from the DC bus to maintain the DC bus at a reference voltage. The system may include a plurality of DC/DC converters respectively provided between a DC bus and a plurality of DC power sources that supply DC power to the DC bus. The system may comprise a plurality of controllers according to the first aspect, each controlling a corresponding DC/DC converter among the plurality of DC/DC converters.

The plurality of controllers may stagger among the plurality of DC/DC converters to reduce the output power of each DC/DC converter when the voltage of the DC bus exceeds the threshold voltage.

The system may further include another controller having a second controller that controls the inverter. The second control unit may reduce the output power output from the inverter in response to receiving the output restriction command signal.

In the control device of the first aspect, the first control section may control each of the plurality of DC/DC converters.

When the voltage of the DC bus exceeds the threshold voltage, the first control unit may reduce the output power of each DC/DC converter with a time difference among the plurality of DC/DC converters.

The first controller may stepwise increase the number of DC/DC converters that reduce the output power among the plurality of DC/DC converters when the voltage of the DC bus exceeds the threshold voltage.

The first control unit reduces the output power of each DC/DC converter in an order according to the maximum output power of each DC power supply connected to each DC/DC converter when the voltage of the DC bus exceeds the threshold voltage. you can

The control device may further include a storage unit that stores different unique threshold voltages equal to or higher than the threshold voltage in association with each of the plurality of DC/DC converters. The first controller may reduce the output power of the DC/DC converter corresponding to the specific threshold voltage when the voltage of the DC bus exceeds the specific threshold voltage.

The control device may further include a storage unit that stores different unique upper limit times in association with each of the plurality of DC/DC converters. The first control unit may reduce the output power of the DC/DC converter corresponding to the specific upper limit time when the duration of the DC bus voltage exceeding the threshold voltage exceeds the specific upper limit time.

The first controller may reduce the output power of each DC/DC converter in random order when the voltage of the DC bus exceeds the threshold voltage.

In a third aspect of the invention, a system is provided. The system may include an inverter that receives power from and receives power from the DC bus to maintain the DC bus at a reference voltage. The system may comprise a plurality of DC/DC converters respectively provided between a DC bus and a plurality of DC power supplies supplying DC output to the DC bus. The system may comprise a controller of the first aspect that controls each of the plurality of DC/DC converters.

The control device may further include a second control section that controls the inverter. The second control unit may reduce the output power output from the inverter in response to receiving the output restriction command signal.

In the system of the second or third aspect, the second control section may determine the amount of current to flow through the inverter based on the target output power included in the command signal and the voltage of the DC bus.

The inverter may have multiple DC/DC converter circuits connected in parallel to the DC bus for each phase of the output. The inverter may comprise, for each phase of the output, a plurality of single-phase inverter circuits connected in series with each other on the output side, each powered by a corresponding DC/DC converter.

Each of the plurality of DC/DC converters may be detachably connected to at least one of the DC power supply and the DC bus.

At least some of the plurality of DC power sources may be photovoltaic power generation devices. A first control unit for controlling a DC/DC converter connected to a photovoltaic power generation device is further capable of controlling the photovoltaic power generation device, when the voltage of the DC bus is equal to or lower than a threshold voltage, and when the DC/DC In at least one of the cases where the output power of the converter is not reduced, MPPT control may be performed so that the maximum power is supplied from the photovoltaic power generation device.

When reducing the output power of some of the DC/DC converters, the first control unit may control the output power to a target value determined from the voltage of the DC bus.

When the output power of some of the DC/DC converters is reduced, the first control unit sets the target value of the reference output power of the DC/DC converters and the DC power supply connected to the DC/DC converters. The control for reducing the output power may be canceled when the power is equal to or higher than at least one of the reference output power.

In a fourth aspect of the invention, a control method is provided. The control method includes a plurality of DC/DC converters respectively provided between a DC bus maintained at a reference voltage by exchanging power with an inverter and a plurality of DC power supplies supplying DC power to the DC bus. may comprise a control stage for controlling at least one of The control method may comprise a voltage measurement step of measuring the voltage of the DC bus. The control phase may reduce the output power of only some of the plurality of DC/DC converters when the DC bus voltage exceeds a threshold voltage higher than the reference voltage.

In a fifth aspect of the invention, a program is provided. A program instructs a computer to provide a DC bus maintained at a reference voltage by transferring power to and from an inverter, and a plurality of DC power sources that supply DC power to the DC bus. A first controller may be implemented to control at least one of the DC converters. The program may cause the computer to implement a voltage measurement unit that measures the voltage of the DC bus. The first controller may reduce the output power of only some of the plurality of DC/DC converters when the voltage of the DC bus exceeds a threshold voltage higher than the reference voltage.

It should be noted that the above summary of the invention does not list all the necessary features of the invention. Subcombinations of these feature groups can also be inventions.

1 shows a power system 1 according to this embodiment. A DC/DC converter 3 is shown. Another DC/DC converter 3 is shown. Cell 25 is shown. The operation of the three-phase inverter 2 is shown. The operation of the control device 5 is shown. A power system 1A according to a first modified example is shown. A controller 7 is shown. The operation of the control device 7 is shown. The operation of the control device 5A is shown. The state transition diagram of the electric power system 1A is shown. A power system 1A according to a second modification is shown. The operation of the control device 5B is shown. An example computer 2200 is shown in which aspects of the present invention may be embodied in whole or in part.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential for the solution of the invention.

[1. power system 1]
FIG. 1 shows a power system 1 according to this embodiment. The power system 1 includes a three-phase inverter 2 and a plurality of DC/DC converters 3 each connected to a DC bus 10 , a DC power supply 4 connected to the DC/DC converters 3 , and a plurality of controllers 5 . A load (not shown) may be further connected to the DC bus 10 . A capacitor (not shown) may be provided between at least one of DC/DC converter 3 , three-phase inverter 2</b>A and load and DC bus 10 .

[1.1. three-phase inverter 2]
The three-phase inverter 2 is an example of an inverter, and performs power conversion between DC power and AC power (three-phase AC power in this embodiment). The three-phase inverter 2 maintains the DC bus 10 at the reference voltage by transferring electric power to and from the DC bus 10 . For example, the three-phase inverter 2 may be a PCS (Power Conditioning System), converts the DC power supplied from the DC bus 10 to DC/AC, outputs it from the AC wiring 15, and converts the AC power supplied from the AC wiring 15 into AC power. Power may be AC/DC converted and supplied to DC bus 10 . The three-phase inverter 2 may maintain the DC bus 10 at the reference voltage by changing the control conditions for such power conversion. A power system of 3.3k∨ or 6.6k∨ may be connected to the AC wiring 15, for example.

The three-phase inverter 2 may include a voltage measuring section 20, a second control section 21, and a single-phase inverter 22 for each of the U-phase, V-phase, and W-phase output phases.

Voltage measurement unit 20 measures the voltage of DC bus 10 . The voltage measurement section 20 may supply the measured voltage to the second control section 21 .

The second control unit 21 controls each single-phase inverter 22 with a control signal Ctrl_DC _/AC . For example, the second control section 21 may change the control conditions for each single-phase inverter 22 based on the voltage measured by the voltage measurement section 20 to maintain the voltage of the DC bus 10 at the reference voltage.

Each single-phase inverter 22 may be a so-called SST (Solid-State Transformer) inverter. For example, the single-phase inverter 22 may have three DC/DC converter circuits 23 and three single-phase inverter circuits 24 . However, the number of DC/DC converter circuits 23 and the number of single-phase inverter circuits 24 may be two, four or more, the same number, or a different number.

In this embodiment, as an example, three DC/DC converter circuits 23 are connected in parallel to the DC bus 10, and each DC/DC converts the DC voltage from the DC bus 10 to the single-phase inverter circuit 24. supply. The three single-phase inverter circuits 24 are connected to the DC/DC converter 3 on the input side to receive power from the DC/DC converter 3, and are connected in series on the output side. Thereby, the single-phase inverter 22 adds the output voltages from the three single-phase inverter circuits 24 and outputs the sum.

In this embodiment, as an example, the DC/DC converter circuit 23 and the single-phase inverter circuit 24 may be in one-to-one correspondence, and each corresponding pair of the DC/DC converter circuit 23 and the single-phase inverter circuit 24 is A cell 25 may be formed. The U-phase, V-phase, and W-phase single-phase inverters 22 are connected to each other in a star connection (also referred to as Y connection), but may be connected in a delta connection (also referred to as Δ connection). Also, the three-phase inverter 2 and the DC bus 10 may be accommodated in a single housing to form a PCS (Power Conditioning System) device 11 . Such a PCS device 11 may be formed as a rack-mount type that can be installed so as to accommodate a plurality of DC/DC converters 3 .

[1.2. DC/DC converter 3]
A plurality of DC/DC converters 3 are respectively provided between a DC bus 10 and a plurality of DC power sources 4 , DC/DC-converts DC power from the DC power sources 4 , and supplies the DC power to the DC bus 10 . In this embodiment, as an example, the electric power system 1 is provided with three DC/DC converters 3 (also referred to as DC/DC converters 3a to 3c), but the number of DC/DC converters 3 may be two. , four or more. Each DC/DC converter 3 may be detachably connected to at least one of the DC power supply 4 and the DC bus 10 . Each DC/DC converter 3 may be connected to the DC bus 10 by being housed in a rack-mounted PCS device 11 .

[1.3. DC power supply 4]
A plurality of DC power supplies 4 supply DC power to the DC bus 10 . In this embodiment, as an example, the power system 1 is provided with three DC power sources 4 (also referred to as DC power sources 4a to 4c), which are the same number as the DC / DC converters 3, and each DC power source 4 corresponds to a single DC / DC DC power is supplied to the DC bus 10 via the converter 3 . Each DC power supply 4 may be a distributed power supply, and at least a part of the plurality of DC power supplies 4 may be a household solar power generation device that outputs several kW of power or a commercial solar power generation device that outputs several MW of power. good. In this embodiment, as an example, the DC power sources 4a and 4b are solar power generation devices, and the DC power source 4c is a storage battery.

[1.4. Control device 5]
A plurality of controllers 5 controls a plurality of DC/DC converters 3 . Each control device 5 has a voltage measurement section 50 , a first control section 51 and a change section 52 .

Voltage measurement unit 50 measures the voltage of DC bus 10 . The voltage measurement section 50 may supply the measured voltage to the first control section 51 .

The first control unit 51 selects at least one DC/DC converter 3 among the plurality of DC/DC converters 3 according to the control signal Ctrl_DC/ _DC. to control. The first control unit 51 reduces the output power of only some of the DC/DC converters 3 among the plurality of DC/DC converters 3 when the voltage of the DC bus 10 exceeds the threshold voltage. For example, the first controller 51 may reduce the output power of the corresponding DC/DC converter 3 .

The threshold voltage is a voltage higher than the reference voltage maintained by the three-phase inverter 2 and may be a voltage lower than the absolute maximum rated voltage. The voltage of the DC bus 10 is determined when a problem occurs in the electric power system 1, or when the load connected to the DC bus 10 or the capacity of the DC power supply 4c as a storage battery does not exceed the capacity of the DC power supplies 4a and 4b as the photovoltaic power generation device. It can be higher than the reference voltage when the power supply increases. The threshold voltage may differ between multiple controllers 5 .

In this case, when the voltage of the DC bus 10 exceeds the threshold voltage of each control device 5, the plurality of control devices 5 control the DC/DC converters 3 with time lags. This will reduce the output power. Further, when the voltage of the DC bus 10 exceeds the threshold voltage of each control device 5, the plurality of control devices 5 reduce the output power of the DC/DC converters 3 among the plurality of DC/DC converters 3 in stages. will increase to Note that the first controller 51 may stop the DC/DC converter 3 when the voltage of the DC bus 10 exceeds the absolute maximum rated voltage.

The changing unit 52 changes the threshold voltage in the first control unit 51 over time. As a result, the order of the threshold voltages changes over time among the plurality of control devices 5 . Moreover, even if the default threshold voltages are the same among the plurality of controllers 5, the threshold voltages of the plurality of controllers 5 are different.

The changing unit 52 may keep the threshold voltage higher than the reference voltage. The changing unit 52 may change the threshold voltage randomly or may change it periodically.

According to the power system 1 described above, when the voltage of the DC bus 10 exceeds the threshold voltage, the output power of some of the plurality of DC/DC converters 3 is reduced. Therefore, even if a problem occurs in the electric power system 1, or if the amount of power supplied from the DC power sources 4a and 4b as solar power generation devices exceeds the load of the DC bus 10 or the capacity of the DC power source 4c as a storage battery, Overvoltage can be prevented by suppressing the voltage of the DC bus 10 to the threshold voltage or less, and damage to the equipment can be prevented. In addition, the voltage of the DC bus 10 is maintained at the reference voltage by power exchange with the three-phase inverter 2, and when the threshold voltage is exceeded, the output power of some of the DC/DC converters 3 is reduced. Since the voltage of the DC bus 10 can be suppressed to the threshold voltage or less, unlike the case where the voltage of the DC bus 10 is controlled to the threshold voltage or less by controlling only the three-phase inverter 2, the voltage of the DC bus 10 is controlled by the control of the three-phase inverter 2 and the DC/DC bus 10. Control of the DC converter 3 can be distributed to facilitate the control. In addition, since the control of the voltage of the DC bus 10 can be divided into the control of the three-phase inverter 2 and the control of the DC/DC converter 3, the number of the DC/DC converters 3 and the DC power supplies 4 in the electric power system 1 can be reduced. The degree of freedom can be increased, and the number of DC/DC converters 3 and DC power supplies 4 can be increased or decreased without changing the control configuration of the three-phase inverter 2 . Moreover, when the voltage of the DC bus 10 exceeds the threshold voltage, the output power of only some of the DC/DC converters 3 is reduced, so that the operation of the power system 1 as a whole can be continued.

In addition, since each first control unit 51 controls any one corresponding DC/DC converter 3, regardless of how many other DC/DC converters 3 are provided in the electric power system 1, the corresponding DC /DC converter 3 can be controlled. Therefore, the number of DC/DC converters 3 can be arbitrarily increased or decreased.

In addition, since the threshold voltage of the first control unit 51 changes over time by the changing unit 52 of each control device 5, even if the default threshold voltages are the same among the plurality of control devices 5 provided in the electric power system 1, Even if there is, the threshold voltage can be made different between the other controllers 5 . Therefore, since the plurality of DC/DC converters 3 can be controlled based on individual threshold voltages, the output power of all the DC/DC converters 3 is reduced when the voltage of the DC bus 10 rises. can be prevented, and the operation of the power system 1 as a whole can be reliably continued. In addition, since the order of the threshold voltages can be changed over time among the plurality of control devices 5, when the voltage of the DC bus 10 repeatedly exceeds the threshold voltage, the output power is reduced. The bias of the DC/DC converter 3 can be prevented.

Further, when the voltage of the DC bus 10 exceeds the threshold voltage, the plurality of controllers 5 reduce the output power of each DC/DC converter 3 with a time difference among the plurality of DC/DC converters 3. When the voltage of the bus 10 rises, it is possible to prevent the output power of all the DC/DC converters 3 from being reduced, and to reliably continue the operation of the power system 1 as a whole.

Moreover, since at least some of the plurality of DC power sources 4 are photovoltaic power generation devices, the DC/DC converter 3 is stopped when the voltage of the DC bus 10 exceeds the threshold voltage due to an increase in the amount of power generated by photovoltaic power generation. can do.

Moreover, since each DC/DC converter 3 is detachably connected to at least one of the DC power supply 4 and the DC bus 10, the number of DC power supplies 4 connected to the DC bus 10 can be easily increased or decreased. .

Further, the three-phase inverter 2 includes a plurality of DC/DC converter circuits 23 connected in parallel to the DC bus 10 and a single-phase inverter circuit 24 connected in series with each other on the output side. , the output power can be increased compared to the case where only the single-phase inverter circuit 24 of .

[2. DC/DC converter 3]
FIG. 2 shows the DC/DC converter 3 . The DC/DC converters 3a, 3b connected to the DC power sources 4a, 4b, which are solar power generation devices, may be step-up choppers that boost the voltage supplied from the DC power sources 4a, 4b. The DC/DC converter 3 has a first positive terminal 31a and a first negative terminal 31b connected to the DC power supply 4, and a second positive terminal 32a and a second negative terminal 32b connected to the DC bus 10. , a diode 33 and a switching element 34 connected in series between the second positive terminal 32a and the second negative terminal 32b, and a smoothing circuit provided between the second positive terminal 32a and the second negative terminal 32b. A capacitor 36 and an inductor 37 provided between the first positive terminal 31 a and between the diode 33 and the switching element 34 are provided. The first negative terminal 31b may be connected to the second negative terminal 32b.

FIG. 3 shows another DC/DC converter 3. As shown in FIG. A DC/DC converter 3 connected to a DC power supply 4c, which is a storage battery, boosts the voltage supplied from the DC power supply 4c and supplies it to the DC bus 10, steps down the voltage supplied from the DC bus 10, and converts it into a DC power supply. 4c may be a bi-directional DC/DC converter. The DC/DC converter 3 may have a configuration in which the diode 33 in the DC/DC converter 3 shown in FIG. 2 is replaced with a switching element 35 .

[3. Cell 25 of single-phase inverter 22]
FIG. 4 shows cell 25 . The cell 25 has a positive terminal 251 a and a negative terminal 251 b connected to the DC bus 10 , AC output terminals 252 and 252 connected in series with the other cells 25 , and a DC/DC converter circuit 23 . , and a single-phase inverter circuit 24 .

The DC/DC converter circuit 23 may be an insulated converter, and in this embodiment, as an example, it is a full-bridge bidirectional DC/DC converter. The DC/DC converter circuit 23 includes a transformer 230, a smoothing capacitor 231 and a full bridge circuit 232 provided between a positive terminal 251a and a negative terminal 251b on the primary side of the transformer 230, and a full bridge circuit 232 on the secondary side of the transformer 230. and a full bridge circuit 234 provided between the positive wiring 233a and the negative wiring 233b. The full bridge circuit 232 may have switching elements 2321 and 2322 and switching elements 2323 and 2324 connected in series between the positive terminal 251a and the negative terminal 251b. and switching elements 2341 and 2342 and switching elements 2343 and 2344 connected in series between the negative wiring 233b and the negative wiring 233b. The primary coil 2301 of the transformer 230 is connected to the midpoint of the switching elements 2321 and 2322 and the midpoint of the switching elements 2323 and 2324, and the secondary coil 2302 is connected to the midpoint of the switching elements 2341 and 2342 and the midpoint of the switching elements 2343 and 2344. may be connected to the midpoint of The transformer 230 may operate at high frequencies of several tens of kHz (eg, 10 kHz to 90 kHz) and may be smaller than transformers for commercial power at 50 kHz or 60 kHz.

The single-phase inverter circuit 24 has a smoothing capacitor 240 and a full bridge circuit 241 provided in parallel between the positive wiring 233a and the negative wiring 233b. The full bridge circuit 241 may have switching elements 2411 and 2412 and switching elements 2413 and 2414 connected in series between the positive wiring 233a and the negative wiring 233b. A midpoint of the switching elements 2411 and 2412 and a midpoint of the switching elements 2413 and 2414 may be connected to the AC output terminals 252 and 252 .

When the AC output terminals 252, 252 of the cell 25 as described above are connected in series with the AC output terminals 252, 252 of the other cells 25, the voltage of the smoothing capacitor 240 is kept constant between the connected cells 25. need to keep. In this regard, in the electric power system 1 according to the present embodiment, the voltage of the DC bus 10 is maintained at the reference voltage by the three-phase inverter 2 as described above, and when the voltage of the DC bus 10 exceeds the threshold voltage, part of the Since the DC bus 10 is controlled below the threshold voltage by the control of the DC/DC converter 3, the voltage of the smoothing capacitor 240 can be reliably maintained constant.

[4. motion]
[4.1. Operation of three-phase inverter 2]
5 shows the operation of the three-phase inverter 2. FIG. The three-phase inverter 2 maintains the voltage of the DC bus 10 at the reference voltage by performing steps S11 to S15. At the start of this operation, the control of each single-phase inverter 22 may be continued by the second control section 21 of the three-phase inverter 2 .

In step S<b>11 , the voltage measurement section 20 measures the voltage of the DC bus 10 . As long as the voltage of DC bus 10 is measured, voltage measuring section 20 may measure the voltage across the input terminals of DC/DC converter circuit 23 in single-phase inverter 22 .

In step S13, the second control section 21 determines whether or not the measured voltage is the reference voltage. The reference voltage may be a single voltage value or a range of voltage values indicated by an upper limit value and a lower limit value. If it is determined that the measured voltage is the reference voltage (step S13; Yes), the process proceeds to step S11, and if it is determined that the measured voltage is not the reference voltage (step S13; No), the process proceeds to step S11. The process proceeds to step S15.

Then, in step S<b>15 , the second control unit 21 attempts to maintain the voltage of the DC bus 10 at the reference voltage by changing the control conditions of each single-phase inverter 22 . For example, the second control unit 21 increases the output of each single-phase inverter 22 when the measured voltage is higher than the reference voltage, and decreases the output of each single-phase inverter 22 when the measured voltage is lower than the reference voltage. Control conditions may be changed. After the process of step S15, the three-phase inverter 2 may shift the process to step S11.

[4.2. Operation of control device 5]
FIG. 6 shows the operation of the control device 5. As shown in FIG. The control device 5 maintains the voltage of the DC bus 10 below the threshold voltage by performing the processes of steps S21 to S25.

At the start of this operation, the control of the corresponding DC/DC converter 3 may be continued by the first control section 51 of the control device 5 . As an example, the control device 5 of the DC/DC converters 3a and 3b connected to the DC power sources 4a and 4b as solar power generation devices controls the DC power sources 4a and 4b so that the maximum power is supplied from the DC power sources 4a and 4b. MPPT (Maximum Power Point Tracking) control may be performed between As a result, the DC/DC converters 3 a and 3 b may DC/DC convert the DC power from the DC power sources 4 a and 4 b and supply the DC power to the DC bus 10 . In addition, the control device 5 of the DC/DC converter 3c connected to the DC power supply 4c as a storage battery responds to the voltage fluctuation of the DC bus 10 and supplies excess power from the DC power supplies 4a and 4b as the photovoltaic power generation device. The DC power supply 4c may be caused to charge when a sufficient amount is generated, and the DC power supply 4c may be caused to discharge when a shortage is generated.

Further, in this embodiment, as an example, the three-phase inverter 2 may perform the processing of steps S11 to S15 while the control device 5 performs the processing of steps S21 to S25. However, the three-phase inverter 2 may be stopped.

In step S<b>21 , the voltage measurement section 50 measures the voltage of the DC bus 10 . As long as the voltage of DC bus 10 is measured, voltage measuring section 50 may measure the voltage between the output terminals of DC/DC converter 3 .

In step S23, the first control unit 51 determines whether or not the measured voltage is equal to or lower than the threshold voltage. The threshold voltage may be a single voltage value. If it is determined that the measured voltage is equal to or lower than the threshold voltage (step S23; Yes), the process proceeds to step S21, and if it is determined that the measured voltage exceeds the threshold voltage (step S23; No), the process goes to step S25.

In step S<b>25 , the first control unit 51 reduces the output power of the corresponding DC/DC converter 3 . Reducing the output power may be to set the output power to zero, or may be to make the power smaller than the current output power.

Here, in this embodiment, as an example, the threshold voltages are different among the plurality of control devices 5 . Therefore, only some of the control devices 5 out of the plurality of control devices 5 perform the process of step S25, and as a result, only some of the DC/DC converters 3 reduce the output power.

Further, the electric power system 1 is provided with a plurality of controllers 5, which independently perform the processes of steps S21 to S25. Therefore, when the threshold voltage is randomly changed by the changing unit 52, the output power of each DC/DC converter 3 may be reduced in random order as the voltage of the DC bus 10 increases.

As an example in this embodiment, the operation of the control device 5 may be completed in step S25. Alternatively, the process may proceed from step S25 to step S21. In this case, when it is determined that the measured voltage exceeds the threshold voltage again in the process of step S23 (step S23; No), the first control unit 51 controls the corresponding DC/DC converter 3 in the process of step S25. may be further reduced. As an example, the first control unit 51 may reduce the output power of the DC/DC converter 3 by a predetermined power for each process of step S25. When the first control unit 51 has already set the output power of the DC/DC converter 3 to zero, the first control unit 51 may maintain the output power of the DC/DC converter 3 at zero in the process of step S25. . Further, when the DC power supply 4c as a storage battery is connected to the DC/DC converter 3, the first control unit 51 changes the output power of the DC/DC converter 3 to negative power (from the DC bus 10 to the DC/DC converter 3) to charge the DC power supply 4c. Further, when it is determined in the process of step S23 that the measured voltage is equal to or lower than the threshold voltage (step S23; Yes), the first control section 51 may restore the output power of the DC/DC converter 3. The threshold voltage for reducing the output power and the threshold voltage for restoring the output power may be the same voltage or different voltages so as to have hysteresis characteristics.

In the above embodiment, the control device 5 is described as a separate device from the corresponding DC/DC converter 3, but the control device 5 and the corresponding DC/DC converter 3 may be provided integrally. good.

Also, although the number of DC power sources 4 and DC/DC converters 3 is the same, the numbers may not be the same. For example, the DC power supplies 4 may be fewer than the DC/DC converters 3 and each DC power supply 4 may be connected to a plurality of corresponding DC/DC converters, or the DC power supplies 4 may be more numerous than the DC/DC converters 3. There may be a plurality of corresponding DC power sources 4 connected to each DC/DC converter 3 .

Further, although the control device 5 has been described as having the changing unit 52 , the changing unit 52 may not be provided if the fixed threshold voltages are different among the plurality of control devices 5 .

Further, although the first control unit 51 is described as reducing the output power of the DC/DC converter 3 corresponding to the first control unit 51 when the voltage of the DC bus 10 exceeds the threshold voltage, the DC bus 10 voltage exceeds the threshold voltage exceeds the upper limit time, the output power of the DC/DC converter 3 corresponding to the first control unit 51 may be reduced. In this case, the control device 5 may further include a changing unit that changes the upper limit time over time. As a result, the upper limit time can be made different between the other control devices 5 provided in the electric power system 1, so that the plurality of DC/DC converters 3 can be controlled based on individual upper limit times. Therefore, when the voltage of DC bus 10 rises, the output power of all DC/DC converters 3 can be prevented from being reduced, and the operation of power system 1 as a whole can be reliably continued.

[5. First modification]
[5.1. power system 1A]
FIG. 7 shows a power system 1A according to a first modified example. Power system 1A may comprise three-phase inverter 2A, controller 5A and controller 7 .

Three-phase inverter 2A is externally connected to control device 7 . The three-phase inverter 2A is controlled by a control signal Ctrl_DC _/AC supplied from the controller 7. FIG.

The control device 5A has a first control section 51A.
51 A of 1st control parts control the DC/DC converter 3a connected to the DC power supply 4a as a solar power generation device. The first controller 51A may further control the DC power supply 4a. The first control unit 51A may perform MPPT control so that the maximum power is supplied from the DC power supply 4a when the voltage of the DC bus 10 is equal to or lower than the threshold voltage.

In addition, the first control unit 51A controls some of the DC/DC converters 3 (the corresponding DC/DC converter 3a in this modification) when the voltage of the DC bus 10 exceeds the threshold voltage. ), the output power may be controlled to a target value determined from the voltage of the DC bus 10 . Details of the target value will be described later.

The control device 7 has a voltage measurement section 70 and a second control section 71 .
Voltage measurement unit 70 measures the voltage of DC bus 10 . The voltage measurement section 70 may supply the measured voltage to the second control section 71 .

The second control section 71 controls at least one single-phase inverter 22 with a control signal Ctrl_DC _/AC . As an example in this modification, the second control unit 71 may control each single-phase inverter 22 . The second control section 71 may change the control conditions of each single-phase inverter 22 based on the voltage measured by the voltage measurement section 70 to maintain the voltage of the DC bus 10 at the reference voltage. In addition, the second control unit 71 may reduce the output power output from the single-phase inverter 22 in response to receiving the output restriction command signal. The output limit command signal may be continuously supplied from the operator or an external device when the output power from the three-phase inverter 2A is greater than the output limit power. The output limit power may be the rated power of the three-phase inverter 2A, or may be the upper limit value of the power output to the AC wiring 15 from the three-phase inverter 2A. The output restriction command signal may be supplied to the second control unit 71 when the power consumption of the load connected to the DC bus 10 increases.

According to the electric power system 1A described above, when the voltage of the DC bus 10 is equal to or lower than the threshold voltage, the DC power supply 4a as the photovoltaic power generation device is MPPT-controlled. Therefore, it is necessary to reduce the output power of the DC/DC converter 3a. If not, the output power of the photovoltaic power generation device and, in turn, the output power of the DC/DC converter 3a can be maximized.

Further, when the output power of the DC/DC converter 3 is reduced, the output power of the DC/DC converter 3 is reduced based on the target value determined from the voltage of the DC bus 10. can be reliably maintained at the reference voltage.

In addition, since the output power output from the single-phase inverter 22 is reduced in response to the second control unit 71 receiving the output restriction command signal, the single-phase inverter 22 It is possible to prevent the output power from being maintained. Further, by reducing the output power from the single-phase inverter 22, the voltage drop of the DC bus 10 can be prevented accordingly. In accordance with this, the output power of the DC/DC converter 3 is kept high by MPPT control or the like, so that the voltage of the DC bus 10 can be increased, and then the output power of the DC/DC converter 3 is reduced. Thus, the voltage of the DC bus 10 can be maintained. Therefore, the voltage of the DC bus 10 can be reliably maintained at the reference voltage without communication between the control device 7 and the control device 5A.

[5.2. Control device 7]
FIG. 8 shows the control device 7 . The second control section 71 of the control device 7 has a voltage control section 710 , an output limit current calculation section 711 , an adjustment section 712 and a switching section 713 .

The voltage control section 710 controls each single-phase inverter 22 in the same manner as the second control section 21 in the above-described embodiment. For example, the voltage control section 710 may change the control condition of each single-phase inverter 22 based on the voltage measured by the voltage measurement section 70 to maintain the voltage of the DC bus 10 at the reference voltage. The voltage control section 710 may supply the control signal Ctrl_DC _/AC to each single-phase inverter 22 via the switching section 713 .

The output limit current calculator 711 determines the current to be supplied to each single-phase inverter 22 when limiting the output power of the single-phase inverter 22 . In response to receiving the command signal for limiting the output, the output limit current calculator 711 instructs the amount of current to flow through the single-phase inverter 22 based on the target output power included in the command signal and the voltage of the DC bus 10. value may be determined. For example, the output limit current calculation unit 711 divides the target output power (W) by the voltage measured by the voltage measurement unit 70, that is, the voltage (V) of the DC bus 10 to calculate the command value of the current amount (I). good. The output limit current calculation unit 711 may supply the calculated command value of the current amount to the adjustment unit 712 .

The adjustment unit 712 corrects the current amount command value supplied from the output limit current calculation unit 711 according to the shortage of the voltage of the DC bus 10 (the voltage measured by the voltage measurement unit 70 in this modification) with respect to the reference voltage. to control each single-phase inverter 22 . The adjustment unit 712 generates the control signal Ctrl_DC _/AC so that a current corresponding to the corrected command value flows through the single-phase inverter 22, and switches the control signal Ctrl_DC _/AC to each single phase through the switching unit 713. It may be supplied to the inverter 22 .

The switching unit 713 supplies the control signal Ctrl_DC _/AC output from either one of the voltage control unit 710 and the adjustment unit 712 to each single-phase inverter 22 . The switching unit 713 supplies the control signal Ctrl_DC _/AC from the adjusting unit 712 to each single-phase inverter 22 when receiving the command signal for limiting the output, and when not receiving the command signal, the voltage control unit A control signal Ctrl_DC _/AC from 710 may be provided to each single phase inverter 22 .

According to the control device 7 described above, the amount of current flowing through the single-phase inverter 22 is determined based on the target output power included in the output restriction command signal and the voltage of the DC bus 10. Output power can be output from the single-phase inverter 22 .

[5.3. motion]
[5.3(1). Operation of control device 7]
9 shows the operation of the control device 7. FIG. The control device 7 controls the output voltage of the single-phase inverter 22 and the voltage of the DC bus 10 by performing the processes of steps S51 to S67. Note that the control of each single-phase inverter 22 by the control device 7 may be continued at the start of this operation.

In step S51, the voltage measurement unit 70 measures the voltage of the DC bus 10 in the same manner as in step S11 described above.

In step S53, the switching unit 713 determines whether or not an output restriction command signal has been received. The output limit command signal may be supplied to the control device 7 when the output power from the three-phase inverter 2A is greater than the output limit power. If it is determined in step S53 that the output restriction command signal has not been received (step S53; No), the process proceeds to step S55. If it is determined in step S53 that an output restriction command signal has been received (step S53; Yes), the process proceeds to step S61.

In step S55, the switching unit 713 selects the voltage control unit 710 as the output source of the control signal Ctrl_DC _/AC . Alternatively, the switching unit 713 may enable the voltage control unit 710 and disable the adjustment unit 712 in step S55.

In step S57, voltage control section 710 determines whether or not the measured voltage is the reference voltage in the same manner as in step S13 described above. If it is determined that the measured voltage is the reference voltage (step S57; Yes), the process proceeds to step S51, and if it is determined that the measured voltage is not the reference voltage (step S57; No), step S59. processing shifts to

Then, in step S59, the voltage control unit 710 attempts to maintain the voltage of the DC bus 10 at the reference voltage by changing the control conditions of each single-phase inverter 22 in the same manner as in step S15 described above. After the process of step S59, the process may proceed to step S51.

In this modification, the control is performed so that the voltage of the DC bus 10 is maintained by the processing of steps S55 to S59. Also called the state of

In step S61, the switching unit 713 selects the adjusting unit 712 as the output source of the control signal Ctrl_DC _/AC . Alternatively, the switching unit 713 may disable the voltage control unit 710 and enable the adjustment unit 712 in step S61.

In step S<b>63 , the output limit current calculator 711 determines a command value for the amount of current to flow through the single-phase inverter 22 based on the target output power included in the command signal and the measured voltage of the DC bus 10 . The amount of current flowing through the single-phase inverter 22 may be the amount of DC current flowing from the DC bus 10 to the single-phase inverter 22, or the amount of AC current output from the single-phase inverter 22 (an effective value as an example). .

In step S65, the adjustment unit 712 corrects the current amount command value according to the shortage of the measured voltage with respect to the reference voltage. For example, the adjustment unit 712 may make the command value of the current amount smaller than the original value as the insufficient voltage increases. As a result, the output from the single-phase inverter 22 is reduced compared to the case where the designated value of the current amount is not reduced, and the drop in the voltage of the DC bus 10 is suppressed. The adjustment unit 712 may perform PI control on the current amount command value. As a result, the current amount command value is corrected so that the current flowing through the single-phase inverter 22 does not oscillate. When there is no shortage of voltage, that is, when the measured voltage is equal to or higher than the reference voltage, the adjustment unit 712 does not need to correct the current amount command value.

In step S67, the adjustment unit 712 limits the current flowing through each single-phase inverter 22 to the corrected command value by changing the control condition of each single-phase inverter 22 based on the corrected command value. Limit the output from the phase inverter 22 . As a result, the power output from the single-phase inverter 22 and, in turn, the three-phase inverter 2A is reduced, the voltage drop of the DC bus 10 is alleviated, and the voltage of the DC bus 10 increases according to the power supply from the DC/DC converter 3. Rise. The output power from the three-phase inverter 2A may be smaller than the output limit power. The process may proceed to step S51 after the process of step S67.

In this modification, since the AC output from the three-phase inverter 2A is restricted by the processing of steps S61 to S67, the state of the control device 7 when performing the processing of steps S61 to S67 is changed to the AC output restriction state. Also called

[5.3(2). Operation of control device 5A]
FIG. 10 shows the operation of the control device 5A. The control device 5A controls the output power of the DC/DC converter 3 and the voltage of the DC bus 10 by performing steps S71 to S87. At the start of this operation, the control of the corresponding DC/DC converter 3a may be continued by the first control section 51A of the control device 5A. Further, in this modified example, as an example, the control device 7 may perform the processing of steps S51 to S67 while the control device 5A performs the processing of steps S71 to S87. However, the control device 7 may be stopped.

In step S71, the voltage measurement unit 50 measures the voltage of the DC bus 10 in the same manner as in step S21 described above.

In step S73, the first control unit 51A determines whether or not the measured voltage is equal to or lower than the threshold voltage in the same manner as in step S23 described above. If it is determined that the measured voltage is equal to or lower than the threshold voltage (step S73; Yes), the process proceeds to step S75, and if it is determined that the measured voltage exceeds the threshold voltage (step S75; No), step The process moves to S81.

In step S<b>75 , the first control unit 51</b>A performs MPPT control so that the maximum power is supplied from the DC power supply 4 a that is the photovoltaic power generation device to the DC/DC converter 3 a and the DC bus 10 . This causes the voltage of the DC bus 10 to rise. After the process of step S75, the process may proceed to step S71.

In this modification, the DC power supply 4a is MPPT-controlled by the processes of steps S71 to S75, so the state of the control device 5A when the processes of steps S71 to S75 are performed is also referred to as the MPPT state.

In step S<b>81 , the first control unit 51</b>A controls the output power of the DC/DC converter 3 a to a target value determined from the measured voltage of the DC bus 10 . The target value may be determined from the measured voltage of DC bus 10 and the reference voltage used by second control section 71 .

For example, the target value may be determined to be smaller than the target value determined in the previous step S81 when the measured voltage is greater than the reference voltage, and when the measured voltage is less than the reference voltage, A value larger than the target value determined in the previous step S81 may be determined. The fluctuation range of the target value each time the process of step S81 is performed may be proportional to the magnitude of the difference between the measured voltage and the reference voltage, or may be constant regardless of the magnitude of the difference.

The target value when the process of step S81 is performed for the first time, that is, the initial value of the target value, may be power smaller than the output power when MPPT control is performed. As a result, the output power of the DC/DC converter 3a is reduced below the output power obtained by the process of step S75. Similarly, each target value when the process of step S81 is repeatedly performed may be power smaller than the output power when MPPT control is performed.

Note that if the measured voltage is equal to the reference voltage, the target value may be the same as in the previous step S81. Further, when the amount of solar radiation temporarily decreases and the power generation amount of the DC power supply 4a, that is, the photovoltaic power generation device decreases, the output power of the DC/DC converter 3a may fall below the target value.

The target value may be calculated by the first controller 51A. Alternatively, the target value may be supplied to the first controller 51A from outside the controller 5A. The target value does not necessarily have to be determined from the reference voltage used by second control section 71 and the measured voltage of DC bus 10 . For example, the target value may be determined from the threshold voltage used by the first control unit 51A in the process of step S73 and the measured voltage, or may be determined from another voltage different from each of the reference voltage and the threshold voltage, and the measured voltage. voltage.

In step S83, the voltage measurement unit 50 measures the voltage of the DC bus 10 in the same manner as in step S21 described above.

In step S85, the first control unit 51A determines whether or not the target value is greater than or equal to the reference output power of the DC/DC converter 3a. The reference output power of the DC/DC converter 3a is, as an example in this modified example, the rated output power that allows the DC/DC converter 3a to be stably used in terms of design, but the DC/DC converter 3a can temporarily output It may be the maximum output power. If it is determined in step S85 that the target value is not equal to or greater than the reference output power (step S85; No), the process proceeds to step S87. If it is determined in step S85 that the target value is greater than or equal to the reference output power (step S85; Yes), the process proceeds to step S71. As a result, the control for reducing the output power of the DC/DC converter 3a by the process of step S81 is canceled.

In step S87, the first control unit 51A determines whether or not the target value is greater than or equal to the reference output power of the DC power supply 4a connected to the DC/DC converter 3a. In this modified example, the reference output power of the DC power supply 4a is, as an example, the rated output power that allows the DC power supply 4a to be stably used in terms of design, but may be the maximum output power that the DC power supply 4a can temporarily output. After the process of step S87, the process may proceed to step S81. If it is determined in step S87 that the target value is not equal to or greater than the reference output power (step S87; No), the process proceeds to step S81. If it is determined in step S87 that the target value is greater than or equal to the reference output power (step S87; Yes), the process proceeds to step S71. As a result, the control for reducing the output power of the DC/DC converter 3a by the process of step S81 is canceled.

Note that only one of the processes of steps S85 and S87 may be performed.
In this modification, since the output power from the DC/DC converter 3a is limited by the processing of steps S81 to S87, the state of the control device 5A when the processing of steps S81 to S87 is performed is also referred to as the state of DC output limitation. called.

According to the above operation, when the output power of the DC/DC converter 3a is reduced in the processing of step S81, the voltage of the DC bus 10 is increased by the processing of steps S51 to S67 by the second control unit 71. As a result, the target value of the output power of the DC/DC converter 3a determined from the voltage of the DC bus 10 is the difference between the reference output power of the DC/DC converter 3a and the reference output power of the DC power supply 4a connected thereto. When at least one of the powers is reached or higher, the control for reducing the output power is canceled. Therefore, it is possible to appropriately switch the control when the output power need not be reduced.

Further, once the measured voltage of the DC bus 10 exceeds the threshold voltage and the control device 5A enters the DC output limiting state, the control device 5A enters the MPPT state according to the target value of the output power determined from the measured voltage. Therefore, the state transition of the control device 5A can be linked with the voltage control of the DC bus 10 by the control device 7 without communication between the control devices 5A and 7 . In addition, since the control device 5A enters the MPPT state not according to the measured voltage itself but according to the target value of the output power determined from the measured voltage, frequent state transitions of the control device 5A can be prevented. .

[5.3(3). State transition table of power system 1A]
FIG. 11 shows a state transition diagram of the power system 1A.

In the electric power system 1A, when the control device 5A is MPPT and the control device 7 is in a state (S0) in which the DC bus voltage is maintained, an output restriction command signal is supplied, that is, the AC output from the three-phase inverter 2A is restricted. When the electric power is exceeded, the control device 5A enters the MPPT state and the control device 7 enters the AC output limited state (S1).

In the electric power system 1A, when the measured voltage of the DC bus voltage becomes higher than the threshold voltage in a state (S1) in which the control device 5A is MPPT and the control device 7 is restricting the AC output, the control device 5A restricts the DC output. In addition, the control device 7 enters the AC output limitation state (S2).

In the electric power system 1A, the target value of the DC output power from the DC/DC converter 3a is greater than or equal to the reference output power when the control device 5A limits the DC output and the control device 7 limits the AC output (S2). Then, the control device 5A enters the MPPT state and the control device 7 enters the AC output limiting state (S3).

In the electric power system 1A, when the control device 5A is MPPT and the control device 7 is in the state of AC output limitation (S3), the output limitation command signal is not supplied, that is, the AC output from the three-phase inverter 2A is limited. If it is below the electric power, the control device 5A becomes MPPT and the control device 7 becomes the state (S0) in which the DC bus voltage is maintained.

Here, among the above states (S0 to S3), when the control device 5A is MPPT and the control device 7 is AC output limited (S1, S3), the control device 5A and the control device 7 are connected to the DC bus 10 voltage control is not performed. Therefore, in this state, if the power supplied from the DC/DC converter 3a to the DC bus 10 falls below the power supplied from the DC bus 10 to the three-phase inverter 2A, the voltage of the DC bus 10 will decrease. In this case, the controller 5A cannot increase the power supplied from the DC/DC converter 3a, whereas the controller 7 can reduce the power supplied to the three-phase inverter 2A. Therefore, in this modification, as an example, the control device 7 in step S63 may decrease the command value for the amount of current to be supplied to the single-phase inverter 22 as the measured voltage of the DC bus 10 is lower. As a result, the voltage drop of the DC bus 10 is prevented.

In the above-described first modification, the control device 5A performs the processing of steps S71 to 75 and the processing of steps S81 to S87, respectively. good too.

In addition, when the target value is equal to or higher than the reference output power of the DC/DC converter 3a (step S85; Yes), or when the target value is the reference output power of the DC power supply 4a connected to the DC/DC converter 3a, the first control unit 51A When the measured voltage of the DC bus 10 is equal to or higher than the output power (step S87; Yes), MPPT control is performed when the measured voltage is equal to or lower than the threshold voltage (step S75; Yes). MPPT control may be performed without determining whether or not the following conditions are satisfied. As an example, when the determination result of step S85 or step S87 is Yes, the first control unit 51A may proceed to the process of step S73 after performing the MPPT control.

Further, although the control device 5A has been described as controlling the DC/DC converter 3a connected to the DC power supply 4a as the solar power generation device, the DC/DC converter 3c connected to the DC power supply 4c as the storage battery is controlled. You may The control device 5A connected to the DC/DC converter 3c may set the target value of the output power of the DC/DC converter 3c to positive or negative power in the process of step S81 according to the voltage fluctuation of the DC bus 10. FIG. Regarding the positive and negative power described here, the power flow that supplies power from the DC power supply 4c as a storage battery to the DC bus 10 may be positive, and the power flow that supplies power from the DC bus 10 to the DC power supply 4c as a storage battery may be positive. can be negative. As a result, the DC power supply 4 c appropriately charges and discharges according to the voltage of the DC bus 10 .

[6. Second modification]
[6.1. power system 1B]
FIG. 12 shows a power system 1B according to a second modification. The power system 1B comprises a three-phase inverter 2B, and the three-phase inverter 2B may have a controller 5B. In addition to voltage measuring section 20 and second control section 21, control device 5B may include storage section 55 and first control section 51B.

The storage unit 55 stores different unique threshold voltages equal to or higher than the threshold voltage in association with each of the plurality of DC/DC converters 3 . Each intrinsic threshold voltage may be a voltage lower than the absolute maximum rated voltage.

The first control unit 51B controls each of the plurality of DC/DC converters 3 with a control signal Ctrl_DC _/DC . The first control unit 51B may reduce the output power of only some of the DC/DC converters 3 among the plurality of DC/DC converters 3 when the voltage of the DC bus 10 exceeds the threshold voltage. When the voltage of the DC bus 10 exceeds the threshold voltage, the first control unit 51B may reduce the output power of each DC/DC converter 3 with a time difference among the plurality of DC/DC converters 3 . Further, when the voltage of the DC bus 10 exceeds the threshold voltage, the first control unit 51B gradually increases the number of the DC/DC converters 3 that reduce the output power among the plurality of DC/DC converters 3. good. For example, when the voltage of the DC bus 10 exceeds any specific threshold voltage, the first control unit 51B may reduce the output power of the DC/DC converter 3 corresponding to the specific threshold voltage. When the voltage of the DC bus 10 exceeds the absolute maximum rated voltage, the first controller 51B may stop each DC/DC converter 3 .

According to the electric power system 1B described above, since the first control unit 51B controls each of the plurality of DC/DC converters 3, the first control unit 51 controls only a part of the plurality of DC/DC converters 3. Unlike the case of the embodiment, control can be performed while adjusting the output power among the plurality of DC/DC converters 3 .

Further, when the voltage of the DC bus 10 exceeds the threshold voltage, the number of the DC/DC converters 3 whose output power is reduced among the plurality of DC/DC converters 3 is gradually increased. The voltage can be reliably suppressed below the threshold voltage.

Further, when the voltage of the DC bus 10 exceeds the threshold voltage, the output power of each DC/DC converter 3 is reduced with a time difference among the plurality of DC/DC converters 3, so that the voltage of the DC bus 10 When it rises, it is possible to prevent the output power of all the DC/DC converters 3 from being reduced, and to reliably continue the operation of the power system 1B as a whole.

In addition, separate peculiar threshold voltages are stored in association with each of the plurality of DC/DC converters 3, and when the voltage of the DC bus 10 exceeds one of the peculiar threshold voltages, the DC voltage corresponding to the peculiar threshold voltage Since the output power of the /DC converter 3 is reduced, it is possible to prevent the output power of all the DC/DC converters 3 from being reduced when the voltage of the DC bus 10 rises. operation can be reliably continued.

[6.2. motion]
FIG. 13 shows the operation of the control device 5B. Control device 5B maintains the voltage of DC bus 10 at the reference voltage by performing the processes of steps S31 to S41. At the start of this operation, the control of each single-phase inverter 22 may be continued by the second control section 21 . Also, the control of the corresponding DC/DC converter 3 may be continued by the first control unit 51B. As an example, the first control unit 51B performs MPPT (Maximum Power Point Tracking) control with the DC power sources 4a and 4b so that the maximum power is supplied from the DC power sources 4a and 4b as the solar power generation device. good. In addition, in response to voltage fluctuations of the DC bus 10, the first control unit 51B controls the DC power supply 4c as a storage battery when there is a surplus in the amount of power supplied from the DC power supplies 4a and 4b as solar power generation devices. Charging may be performed, and when a shortage occurs, the DC power supply 4c may be caused to discharge.

In step S<b>31 , the voltage measurement section 20 measures the voltage of the DC bus 10 .

In step S33, the second control section 21 determines whether or not the measured voltage is the reference voltage in the same manner as in step S13 described above. If it is determined that the measured voltage is the reference voltage (step S33; Yes), the process proceeds to step S31, and if it is determined that the measured voltage is not the reference voltage (step S33; No), the process proceeds to step S31. The process proceeds to step S35.

In step S35, the second control unit 21 attempts to maintain the voltage of the DC bus 10 at the reference voltage by changing the control conditions of each single-phase inverter 22 in the same manner as in step S15 described above.

In step S<b>37 , the voltage measurement section 20 measures the voltage of the DC bus 10 .

In step S39, the first control unit 51B determines whether or not the measured voltage exceeds any specific threshold voltage. If it is determined that the measured voltage exceeds any specific threshold voltage (step S39; Yes), the process proceeds to step S41, and if it is determined that the measured voltage does not exceed the specific threshold voltage (step S39; No), the process proceeds to step S31.

Each unique threshold voltage may be a single voltage value. Here, as an example in this embodiment, the characteristic threshold voltage of the DC/DC converter 3 is set according to the maximum output power of the DC power supply 4 connected to the DC/DC converter 3. The inherent threshold voltage of the DC/DC converter 3 is set to be higher (or lower) in descending order of the maximum output power of the DC power supply 4 .

In step S41, the first controller 51B reduces the output power of the DC/DC converter 3 corresponding to the characteristic threshold voltage below the measured voltage. For example, the first control unit 51B may make the output power lower than the current power. As a result, the output power of only some of the DC/DC converters 3 among the plurality of DC/DC converters 3 is reduced. After completing the process of step S41, the process may proceed to step S31.

Here, in this embodiment, as an example, the intrinsic threshold voltage of the DC/DC converter 3 is set according to the order of the maximum output power of the connected DC power supply 4 . Therefore, when the processing of steps S39 to S41 is repeated, the output power of each DC/DC converter 3 is reduced in the order according to the maximum output power of each DC power supply 4 connected to each DC/DC converter 3. be.

According to the above operation, when the voltage of the DC bus 10 exceeds the threshold voltage, the output power of each DC/DC converter 3 is reduced in the order according to the maximum output power of each DC power supply 4 connected. Therefore, when the output power of each DC/DC converter 3 is reduced in descending order of the maximum output power of the DC power supply 4, the amount of power supplied from the plurality of DC/DC converters 3 to the DC bus 10 is immediately increased. Since the voltage can be reduced, the voltage of the DC bus can be reliably suppressed to the threshold voltage or less, and the safety can be improved. Further, when the output power of each DC/DC converter 3 is reduced in ascending order of the maximum output power of the DC power supply 4, the amount of power supplied from the plurality of DC/DC converters 3 to the DC bus 10 is gradually increased. Therefore, the output power of the power system 1 as a whole can be kept high.

In the second modification, the storage unit 55 stores different unique threshold voltages in association with each of the plurality of DC/DC converters 3, and the first control unit 51B controls the voltage of the DC bus 10. exceeds the specific threshold voltage, the output power of the DC/DC converter 3 corresponding to the specific threshold voltage is reduced. Instead of this, each of the plurality of DC/DC converters 3 is associated with a different unique upper limit time and stored in the storage unit 55, and the first control unit 51B controls the continuation time when the voltage of the DC bus 10 exceeds the threshold voltage. When the time exceeds any specific upper limit time, the output power of the DC/DC converter 3 corresponding to the specific upper limit time may be reduced. As a result, the upper limit time can be made different between the other control devices 5 provided in the electric power system 1, so that the plurality of DC/DC converters 3 can be controlled based on individual upper limit times. Therefore, when the voltage of the DC bus 10 rises, the output power of all the DC/DC converters 3 can be prevented from being reduced, and the operation of the power system 1 as a whole can be reliably continued. The specific upper limit time of each DC/DC converter 3 may be set, for example, according to the order according to the maximum output power of the connected DC power supply 4 .

Also, the first control unit 51B is described as reducing the output power of each DC/DC converter 3 in the order according to the maximum output power of the DC power supply 4 when the voltage of the DC bus 10 exceeds the threshold voltage. , the output power of each DC/DC converter 3 may be reduced in a random order, or a history of reducing the output power of each DC/DC converter 3 may be stored, and the number of times the output power is reduced may be stored. Alternatively, the DC/DC converter 3 with a smaller amount may be preferentially targeted for reduction. Even in these cases, when the voltage of the DC bus 10 rises, the output power of all the DC/DC converters 3 is prevented from being reduced, and the operation of the power system 1 as a whole is reliably continued. be able to.

Further, although it has been described that the control device 5B has the second control section 21 and the storage section 55, it may not have at least one of them. If the control device 5B does not have the second control section 21, the second control section 21 may be provided outside the control device 5B. If the control device 5B does not have the storage unit 55, the control device 5B may reduce the output power of each DC/DC converter 3 in a random order as described above, or the rack-mount type PCS device. The output power of each DC/DC converter 3 may be reduced in the order according to the connection position of each DC/DC converter 3 with respect to 11 .

Further, although the control device 5B has been described as having the second control section 21, it may have the second control section 71 in the above-described first modification. In this case, the control device 5B may perform the processes of steps S71 to S87 instead of the processes of steps S31 to S35. Further, although the control device 5B has been described as having the first control section 51B, it may have the first control section 51A in the above-described first modification. In this case, if it is determined in step S39 that the measured voltage does not exceed any specific threshold voltage (step S39; No), the controller 5B controls the DC/DC converter corresponding to the specific threshold voltage greater than the measured voltage. MPPT control may be performed for 3a and 3b. In addition, when it is determined that the measured voltage exceeds any of the eigenthreshold voltages in step S39 (step S39; Yes), the control device 5B controls the DC/DC converter 3 corresponding to the eigenthreshold voltage below the measurement voltage. may be processed in steps S81 to S87.

[7. Other Modifications]
In the above embodiments and modifications, power systems 1, 1A, and 1B are described as including three-phase inverters 2 having single-phase inverters 22 for each of the U-phase, V-phase, and W-phase. It may have only the single-phase inverter 22 , only the DC/DC converter circuit 23 , or only the single-phase inverter circuit 24 . Moreover, although the three-phase inverter 2 has been described as having a single single-phase inverter 22 for each phase, it may have a plurality of single-phase inverters 22 connected in series or in parallel.

Further, although the single-phase inverter 22 has been described as a full-bridge inverter circuit having the full-bridge circuit 241, it may be a half-bridge inverter circuit having a half-bridge circuit.

Moreover, although the electric power systems 1, 1A, and 1B have been described as including the DC power supply 4, they may be externally connected to the DC power supply 4 without including the DC power supply 4. FIG.

Additionally, various embodiments of the invention may be described with reference to flowchart illustrations and block diagrams, where blocks represent (1) steps in a process in which operations are performed or (2) roles that perform operations. may represent a section of equipment that has Certain steps and sections may be implemented by dedicated circuitry, programmable circuitry provided with computer readable instructions stored on a computer readable medium, and/or processor provided with computer readable instructions stored on a computer readable medium. you can Dedicated circuitry may include digital and/or analog hardware circuitry, and may include integrated circuits (ICs) and/or discrete circuitry. Programmable circuits include logic AND, logic OR, logic XOR, logic NAND, logic NOR, and other logic operations, memory elements such as flip-flops, registers, field programmable gate arrays (FPGAs), programmable logic arrays (PLAs), etc. and the like.

Computer-readable media may include any tangible device capable of storing instructions to be executed by a suitable device, such that computer-readable media having instructions stored thereon may be designated in flowcharts or block diagrams. It will comprise an article of manufacture containing instructions that can be executed to create means for performing the operations described above. Examples of computer-readable media may include electronic storage media, magnetic storage media, optical storage media, electromagnetic storage media, semiconductor storage media, and the like. More specific examples of computer readable media include floppy disks, diskettes, hard disks, random access memory (RAM), read only memory (ROM), erasable programmable read only memory (EPROM or flash memory), Electrically Erasable Programmable Read Only Memory (EEPROM), Static Random Access Memory (SRAM), Compact Disc Read Only Memory (CD-ROM), Digital Versatile Disc (DVD), Blu-ray (RTM) Disc, Memory Stick, Integration Circuit cards and the like may be included.

The computer readable instructions may be assembler instructions, Instruction Set Architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state setting data, or object oriented programming such as Smalltalk, JAVA, C++, etc. language, and any combination of one or more programming languages, including conventional procedural programming languages, such as the "C" programming language or similar programming languages. good.

Computer readable instructions may be transferred to a processor or programmable circuitry of a general purpose computer, special purpose computer, or other programmable data processing apparatus, either locally or over a wide area network (WAN), such as a local area network (LAN), the Internet, or the like. ) and may be executed to create means for performing the operations specified in the flowcharts or block diagrams. Examples of processors include computer processors, processing units, microprocessors, digital signal processors, controllers, microcontrollers, and the like.

FIG. 14 illustrates an example computer 2200 in which aspects of the invention may be implemented in whole or in part. Programs installed on the computer 2200 may cause the computer 2200 to function as one or more sections of an operation or apparatus associated with an apparatus according to embodiments of the invention, or may Sections may be executed and/or computer 2200 may be caused to execute processes or steps of such processes according to embodiments of the present invention. Such programs may be executed by CPU 2212 to cause computer 2200 to perform certain operations associated with some or all of the blocks in the flowcharts and block diagrams described herein.

Computer 2200 according to this embodiment includes CPU 2212 , RAM 2214 , graphics controller 2216 , and display device 2218 , which are interconnected by host controller 2210 . Computer 2200 also includes input/output units such as communication interface 2222, hard disk drive 2224, DVD-ROM drive 2226, and IC card drive, which are connected to host controller 2210 via input/output controller 2220. there is The computer also includes legacy input/output units such as ROM 2230 and keyboard 2242 , which are connected to input/output controller 2220 through input/output chip 2240 .

CPU 2212 operates according to programs stored in ROM 2230 and RAM 2214, thereby controlling each unit. Graphics controller 2216 retrieves image data generated by CPU 2212 into itself, such as a frame buffer provided in RAM 2214 , and causes the image data to be displayed on display device 2218 .

Communication interface 2222 communicates with other electronic devices over a network. Hard disk drive 2224 stores programs and data used by CPU 2212 within computer 2200 . DVD-ROM drive 2226 reads programs or data from DVD-ROM 2201 and provides programs or data to hard disk drive 2224 via RAM 2214 . The IC card drive reads programs and data from IC cards and/or writes programs and data to IC cards.

ROM 2230 stores therein programs that are dependent on the hardware of computer 2200, such as a boot program that is executed by computer 2200 upon activation. Input/output chip 2240 may also connect various input/output units to input/output controller 2220 via parallel ports, serial ports, keyboard ports, mouse ports, and the like.

A program is provided by a computer-readable medium such as a DVD-ROM 2201 or an IC card. The program is read from a computer-readable medium, installed in hard disk drive 2224 , RAM 2214 , or ROM 2230 , which are also examples of computer-readable medium, and executed by CPU 2212 . The information processing described within these programs is read by computer 2200 to provide coordination between the programs and the various types of hardware resources described above. An apparatus or method may be configured by implementing the manipulation or processing of information in accordance with the use of computer 2200 .

For example, when communication is performed between the computer 2200 and an external device, the CPU 2212 executes a communication program loaded in the RAM 2214 and sends communication processing to the communication interface 2222 based on the processing described in the communication program. you can command. The communication interface 2222 reads transmission data stored in a transmission buffer processing area provided in a recording medium such as the RAM 2214, the hard disk drive 2224, the DVD-ROM 2201, or an IC card under the control of the CPU 2212, and transmits the read transmission data. Data is transmitted to the network, or received data received from the network is written to a receive buffer processing area or the like provided on the recording medium.

In addition, the CPU 2212 causes the RAM 2214 to read all or necessary portions of files or databases stored in external recording media such as a hard disk drive 2224, a DVD-ROM drive 2226 (DVD-ROM 2201), an IC card, etc. Various types of processing may be performed on the data in RAM 2214 . CPU 2212 then writes back the processed data to the external recording medium.

Various types of information, such as various types of programs, data, tables, and databases, may be stored on recording media and subjected to information processing. CPU 2212 performs various types of operations on data read from RAM 2214, information processing, conditional decision making, conditional branching, unconditional branching, and information retrieval, as specified throughout this disclosure and by instruction sequences of programs. Various types of processing may be performed, including /replace, etc., and the results written back to RAM 2214 . In addition, the CPU 2212 may search for information in a file in a recording medium, a database, or the like. For example, if a plurality of entries each having an attribute value of a first attribute associated with an attribute value of a second attribute are stored in the recording medium, the CPU 2212 determines that the attribute value of the first attribute is specified. search the plurality of entries for an entry that matches the condition, read the attribute value of the second attribute stored in the entry, and thereby associate it with the first attribute that satisfies the predetermined condition. an attribute value of the second attribute obtained.

The programs or software modules described above may be stored in a computer readable medium on or near computer 2200 . Also, a recording medium such as a hard disk or RAM provided in a server system connected to a dedicated communication network or the Internet can be used as a computer-readable medium, thereby providing the program to the computer 2200 via the network. do.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the description of the scope of the claims that forms with such modifications or improvements can also be included in the technical scope of the present invention.

The execution order of each process such as actions, procedures, steps, and stages in devices, systems, programs, and methods shown in claims, specifications, and drawings is etc., and it should be noted that they can be implemented in any order unless the output of a previous process is used in a later process. Regarding the operation flow in the claims, specification, and drawings, even if explanations are made using "first," "next," etc. for the sake of convenience, it means that it is essential to carry out in this order. isn't it.

REFERENCE SIGNS LIST 1 electric power system 2 three-phase inverter 3 DC/DC converter 4 DC power supply 5 control device 10 DC bus 11 device 20 voltage measurement unit 21 second control unit 22 single-phase inverter 23 DC/DC Converter circuit 24 Single-phase inverter circuit 25 Cell 31 First positive terminal 32 Second positive terminal 33 Diode 34 Switching element 35 Switching element 36 Smoothing capacitor 37 Inductor 50 Voltage measuring unit 51 First control unit 52 Change unit 55 Storage unit 230 Transformer 231 Smoothing capacitor 232 Full bridge circuit 233 Positive wiring 234 Full bridge circuit 240 Smoothing capacitor 241 Full bridge circuit 251 Positive terminal 252 AC output terminal, 2200 computer, 2201 DVD-ROM, 2210 host controller, 2212 CPU, 2214 RAM, 2216 graphic controller, 2218 display device, 2220 input/output controller, 2222 communication interface, 2224 hard disk drive, 2226 DVD-ROM drive, 2230 ROM, 2240 Input/output chip, 2242 Keyboard, 2301 Primary coil, 2302 Secondary coil, 2321 Switching element, 2322 Switching element, 2323 Switching element, 2324 Switching element, 2341 Switching element, 2342 Switching element, 2343 Switching element, 2344 Switching element 2411 Switching element 2412 Switching element 2413 Switching element 2414 Switching element

Claims (16)

a controller,
Among a plurality of DC/DC converters respectively provided between a DC bus maintained at a reference voltage by exchanging power with an inverter and a plurality of DC power sources supplying DC power to the DC bus, corresponding A first control unit that controls any one DC / DC converter to
a voltage measuring unit that measures the voltage of the DC bus;
with
The first control unit is
reducing the output power of the corresponding DC/DC converter when the duration of the DC bus voltage exceeding the threshold voltage higher than the reference voltage exceeds the upper limit time;
The controller is
The control device further includes a changing unit that changes the upper limit time over time . 2. The control device according to claim 1, further comprising a changing unit that changes the threshold voltage over time. an inverter that maintains the DC bus at a reference voltage by transferring power to and from the DC bus;
a plurality of DC/DC converters respectively provided between the DC bus and a plurality of DC power sources that supply DC power to the DC bus;
A plurality of control devices according to claim 1 or 2 , each controlling a corresponding one of the plurality of DC/DC converters;
A system with When the voltage of the DC bus exceeds the threshold voltage, the plurality of control devices reduce the output power of each DC/DC converter with a time lag among the plurality of DC/DC converters.
4. The system of claim 3 . Further comprising another control device having a second control unit that controls the inverter,
The second control unit reduces the output power output from the inverter in response to receiving an output restriction command signal.
5. A system according to claim 3 or 4 . Control each of a plurality of DC/DC converters provided between a DC bus maintained at a reference voltage by transferring power to and from an inverter and a plurality of DC power supplies that supply DC power to the DC bus. a first control unit that
a voltage measuring unit that measures the voltage of the DC bus;
a storage unit that stores different unique upper limit times in association with each of the plurality of DC/DC converters;
with
When the duration of the voltage of the DC bus exceeding a threshold voltage higher than the reference voltage exceeds any of the peculiar upper time limits, the first control unit controls the DC/DC A controller that reduces the output power of the converter . an inverter that maintains the DC bus at a reference voltage by transferring power to and from the DC bus;
a plurality of DC/DC converters respectively provided between the DC bus and a plurality of DC power supplies that supply DC outputs to the DC bus;
7. The control device according to claim 6 , which controls each of the plurality of DC/DC converters;
A system with The control device is
further comprising a second control unit that controls the inverter,
The second control unit reduces the output power output from the inverter in response to receiving an output restriction command signal.
8. The system of claim 7 . 9. The system according to claim 5, wherein said second control unit determines the amount of current to be supplied to said inverter based on the target output power included in said command signal and the voltage of said DC bus. At least part of the plurality of DC power sources are solar power generation devices,
The first control unit that controls the DC/DC converter connected to the photovoltaic power generation device can further control the photovoltaic power generation device, and when the voltage of the DC bus is equal to or lower than the threshold voltage, and , in at least one case where the output power of the DC/DC converter is not reduced, perform MPPT control so that the maximum power is supplied from the photovoltaic power generation device;
System according to any one of claims 3 to 5, 8 and 9 . 9. From claims 3 to 5 and 8, wherein, when reducing the output power of the DC /DC converter, the first control unit controls the output power to a target value determined from the voltage of the DC bus. 11. The system according to any one of clause 10 . When the output power of the DC/DC converter is reduced, the first control unit determines that the target value is the reference output power of the DC/DC converter and the DC power supply connected to the DC/DC converter. 12. The system according to claim 11 , wherein the control for reducing the output power is canceled in accordance with at least one power of the reference output power of . A control method comprising:
Among a plurality of DC/DC converters respectively provided between a DC bus maintained at a reference voltage by exchanging power with an inverter and a plurality of DC power sources supplying DC power to the DC bus, corresponding a control stage for controlling any one DC/DC converter that
a voltage measuring step of measuring the voltage of the DC bus;
with
In the control stage,
reducing the output power of the corresponding DC/DC converter when the duration of the DC bus voltage exceeding the threshold voltage higher than the reference voltage exceeds the upper limit time;
The control method is
A control method further comprising changing the upper limit time over time . Control each of a plurality of DC/DC converters provided between a DC bus maintained at a reference voltage by transferring power to and from an inverter and a plurality of DC power supplies that supply DC power to the DC bus. a control step to
a voltage measuring step of measuring the voltage of the DC bus;
a storage step that stores different unique upper limit times in association with each of the plurality of DC/DC converters;
with
In the control step , when the duration of the voltage of the DC bus exceeding a threshold voltage higher than the reference voltage exceeds any of the specific upper time limits, the DC/DC converter corresponding to the specific upper limit time period. A control method that reduces the output power . to the computer,
Among a plurality of DC/DC converters respectively provided between a DC bus maintained at a reference voltage by exchanging power with an inverter and a plurality of DC power sources supplying DC power to the DC bus, corresponding A first control unit that controls any one DC / DC converter to
and a voltage measuring unit that measures the voltage of the DC bus,
The first control unit is
reducing the output power of the corresponding DC/DC converter when the duration of the DC bus voltage exceeding the threshold voltage higher than the reference voltage exceeds the upper limit time;
to the computer;
A program that further implements a changing unit that changes the upper limit time over time . to the computer,
Control each of a plurality of DC/DC converters provided between a DC bus maintained at a reference voltage by transferring power to and from an inverter and a plurality of DC power supplies that supply DC power to the DC bus. a first control unit that
a voltage measuring unit that measures the voltage of the DC bus ;
a storage unit that stores different unique upper limit times in association with each of the plurality of DC/DC converters;
to realize
When the duration of the voltage of the DC bus exceeding a threshold voltage higher than the reference voltage exceeds any of the peculiar upper time limits, the first control unit controls the DC/DC Program to reduce the output power of the converter .

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