JP7068675B2 - Power supply system - Google Patents

Description

Embodiments of the present invention relate to a power supply system.

In recent years, power generated by a distributed power source using renewable energy such as a photovoltaic power generation system (photovoltaic (PV) system) or a wind power generation system has been used as power supply to private equipment (load). .. At this time, the output power of the distributed power source is affected by the influence of the environment such as weather, and stable power supply cannot be expected. Therefore, it is common to use a secondary battery (storage battery) capable of charging and discharging together.

In such a power supply system using renewable energy, a local production for local consumption type independent power supply system that does not depend on the grid power supply from the power company has been devised (see, for example, Patent Document 1).

Japanese Patent No. 6189448

In a power supply system that is independent of the grid power supply and supplies power to the load using a distributed power supply and a storage battery, a plurality of distributed power supplies may be installed in order to cover the power supply of the load or depending on the application. In that case, it is not always possible to install a storage battery that matches the capacity of the distributed power source.

When there are multiple distributed power sources, in a system that supplies power to the load using the PCS connected to the distributed power source, if the PCS is a type of device that can only operate at rated operation, power is supplied according to the fluctuation of the load. There is a problem that fine control of wood grain is not possible. That is, when the PCS is only rated operation, it is ON or OFF (100% output or 0% output) operation, so that it is not possible to supply power less than the rating for one PCS.

In addition, in the case of a type of device having an output suppression function in which the output power is variable from 0 to 100%, the PCS has a characteristic that the response speed is slow, so that sudden load fluctuations and weather fluctuations occur. In a state of oversupply, the power generated by the distributed power supply is normally absorbed as the charging power of the storage battery, but if the capacity of the storage battery is smaller than the capacity of the distributed power supply, the storage battery is charged. There is a problem that the storage battery (to be exact, the power converter (PCS) provided in the storage battery or separately) trips when the power of the storage battery exceeds the permissible amount.

This embodiment has been proposed to solve the above-mentioned problems of the prior art. An object of the present embodiment is to provide a power supply system that avoids tripping of a storage battery in an independent power supply system including a distributed power source and a storage battery.

In order to achieve the above object, the power supply system of the embodiment has a plurality of distributed power sources that output DC power, and a plurality of distributed power sources that are connected to each of the plurality of distributed power sources and output predetermined power and are connected in parallel to each other. A first power converter, a second power converter connected in parallel with the plurality of first power converters and bidirectionally converting power into predetermined power, and a second power converter connected to the second power converter. A chargeable and dischargeable storage battery, a load supplied with power from the distributed power source and the storage battery at the time of discharge, an output power value of the first power converter, and an input / output power of the second power converter. One of the plurality of first power converters so as to maximize the power supplied to the load from the plurality of distributed power sources and the power value grasping means for measuring each of the value and the power supplied to the load. The required number of operating units of the first power converter is obtained from the power supplied to the load, the charge / discharge power of the storage battery, and the output power of the first power converter that has been rated and operated. The difference between the power supplied to the load and the charge / discharge power of the storage battery and the output power of the first power converter that has been rated and operated by operating the first power converter for the number of operating units is divided. The gist is to provide a control means for giving an output power value to the remaining first power converter in operation.

Further, the control means may preferentially operate the first power converter having a smaller number of operations among the plurality of first power converters.

Further, when the rated power capacity of the second power converter is smaller than the total rated power capacity of the plurality of first power converters, the control means is the power value grasping means of the second power converter. When the charging power larger than the rated power capacity of the second power converter is measured, or when the charging power having a value close to the rated power capacity of the second power converter is measured, the required required second is obtained. The number of operating units of one power converter may be reduced by one.

The system block diagram which shows the 1st Embodiment of this invention. The flowchart which shows the number control of PCS of 1st Embodiment of this invention. The flowchart which shows the number control of PCS of 2nd Embodiment of this invention.

(Structure of the first embodiment)
Hereinafter, the configuration of the first embodiment according to the present invention will be described with reference to FIG. FIG. 1 is a system configuration diagram showing a first embodiment of the present invention. In order to supply electric power to the load 1, the supply source is composed of a storage battery 2 which is a secondary battery such as a lithium ion battery that can be charged and discharged, and a solar cell 3 which is a distributed power source connected in parallel to the storage battery 2. ing. This is an embodiment assuming a case where a plurality of solar cells 3 are installed in order to secure a power supply for the load 1 when the scale of the load 1 is large. The number of solar cells 3 is composed of 5 in this embodiment, but it goes without saying that this number is an example. The distributed power source uses the solar cell 3 in the present embodiment, but is not limited to this, and uses a device that generates DC power by using renewable energy such as wind power generation and a chemical reaction such as hydrogen. It may be a fuel cell.

A plurality of power converters (PCS4a (first power converter)) are connected in a form corresponding to each of the plurality of solar cells 3, and the DC power generated by the solar cells 3 is converted into a predetermined power (depending on the load). Select a model that performs DC / DC conversion or DC / AC conversion). Here, the PCS4a uses a type of device that can be remotely operated / stopped and has an output suppression function in which the output power is variable from 0 to 100%.

A power converter (PCS4b (second power converter)) is also connected to the storage battery 2, and the PCS4b converts power in both directions in order to charge or discharge the storage battery 2. The PCS 4a and 4b are connected in parallel, and when the storage battery 2 is discharged, power is supplied to the load 1 together with the solar cell 3. When the storage battery 2 is charged, a part or all of the electric power generated by the solar cell 3 is charged. Here, the charging / discharging switching of the storage battery 2 is switched to discharging when the power supplied to the load 1 is insufficient, and switching to charging when the power is excessive.

Further, a power sensor 5 (power value grasping means) for measuring the power value is provided, the power sensor 5a measures the output power of each of the plurality of PCS4a, and the power sensor 5b measures the charge / discharge power of the storage battery 2. In this embodiment, it is installed on the load 1 side of the PCS4b. The power sensor 5c measures the power value supplied to the load 1. Here, in the present embodiment, the power sensors 5a and 5b are provided separately from the PCS4a and 4b, but as the power value grasping means, the output power may be directly detected from the PCS4a and 4b main body.

The power value detected by the power sensors 5a, 5b, and 5c is taken into the control device 6 (control means), and the control means 6 calculates the number of operating units to the PCS 4a, gives an operation / stop command, and sets the output power value. do. The control device 6 can be realized by using, for example, a PLC (Programmable Logical Controller), and the signal exchange with the power sensors 5a and 5b and the PCS4a is by a DC4 to 20 mA current signal or serial such as RS-485. Interface etc. can be used.

(Action and effect of the first embodiment)
Next, the number control of the PCS4a according to the first embodiment of the present invention will be described with reference to the flowchart of FIG. The operations and commands shown in the flowchart can be realized by constructing a program in the control device 6, for example. Here, the purpose of controlling the number of PCS4a is to maximize the power supplied from the solar cell 3 which is a distributed power source to the load 1.

In step S1 of FIG. 2, the output of the representative PCS4a is set to 100% (rated operation). The representative PCS4a may be fixed to any one of the plurality of PCS4a, or may be switched to which PCS4a becomes the representative PCS4a at an arbitrary timing. A 100% output command is given to the representative PCS4a, the generated power is measured by the power sensor 5a (X), and is input to the control device 6. Here, since the power generation source of the generated power is the solar cell 3, even if a command for 100% output is given to the representative PCS4a, the generated power is not fixedly determined depending on the weather and the time zone. Further, MPPT control (Maximum Power Point Tracking) may be executed in the PCS4a in order to obtain the maximum power generation.

In step S2, the generated power of the other PCS4a other than the representative PCS4a is measured by the power sensor 5a (Pi) and input to the control device 6.

In step S3, the sum of the electric power generated by the solar cell 3 is calculated by the formula.
(Y) = (X) + Σ (Pi) ・ ・ ・ (1)
Ask for. Here, (Y) is the total power generation power of the solar cell 3, (X) is the power generation power of the representative PCS4a, (Pi) is the individual power generation power of other PCS4a other than the representative PCS4a, and Σ (Pi) is. Others are the sum of the individual generated power of PCS4a.

In step S4, the charge / discharge power (CT) of the storage battery 2 is measured. (CT) has a positive value when the storage battery 2 is discharged and a negative value when the storage battery 2 is charged.

In step S5, the power consumed by the load 1 is measured (A) and input to the control device 6.

Next, in step S6, the number of operating PCS4a (B) is expressed by the formula.
(B) = (A) / (X) (rounded up to the nearest whole number) ... (2)
Ask for. By dividing the power consumption (A) of the load 1 by the generated power (X) of the representative PCS4a, the number of operating PCS4a to satisfy the power consumption of the load 1 can be obtained, and by rounding up the fractions below the quotient. This means that we are seeking the number of PCS4a in operation, which is one more (more accurately, less than one). Of course, the number of PCS4a in operation is limited by the number of installations, so if the power consumption of load 1 cannot be covered even if all PCS4a are operated at 100%, the storage battery 2 will supply insufficient power. Become.

In step S7, PCS4a is operated for the number of units obtained in step S6. At this time, if the PCS4a to be operated is preferentially operated from, for example, the PCS4a having a smaller number of operations, the effect that the number of activations of the PCS4a is equalized and the life is averaged can be obtained. Further, if the operation time is used as an index instead of the number of operations, the same effect can be obtained. On the contrary, if the operation is performed from the one with the largest number of operations or the one with the longest operation time, the lifespan will be reached in order, so that it is possible to obtain the effect of leveling the replacement and maintenance due to the lifespan of the PCS4a. Of course, the same applies when the PCS4a is stopped, and the same effect can be obtained by stopping the PCS4a from the one with the largest number of operations or the one with the shorter operation time. The number of operations and the operation time of the PCS 4a can be realized by integrating the count numbers with the control device 6.

In step S8, the other output setting values of PCS4a are expressed in the formula.
(C) = [(A)-(X)] / [(B) -1] ... (3)
And other output setting values are given to PCS4a. This is because the numerator "-(X)" and the denominator "-1" exclude the representative PCS4a. By doing so, the number of operating PCS4a calculated by the equation (2) was one more, but by giving the output set value (C) to the other PCS4a in proportion, the power consumption of the load 1 was consumed. It will be possible to supply power equivalent to. In addition, since the PCS4a is not 100% operated and has a surplus capacity, there is an effect that it can follow some load fluctuations and power generation fluctuations due to weather changes.

By returning to step S1 and repeatedly executing steps S1 to S8, the number of PCS4a to be operated is determined according to the power consumption of the load 1 and the generated power of the distributed power 3, and the power supplied from the solar cell 3 to the load 1 is maximum. Can be controlled so as to become.

(Second embodiment)
Hereinafter, a second embodiment according to the present invention will be described. Since the configuration is the same as that of the first embodiment, the description thereof will be omitted, and the actions and effects will be described with reference to FIG.

FIG. 3 is a flowchart showing the number control of PCS4a according to the second embodiment of the present invention. In particular, it shows the control of the number of PCS4a when the power exceeding the rating of the PCS4b is input when the storage battery 2 is charged (excessive input to the PCS4b). P2 is added, and this difference will be described. If an excessive input is made to the PCS4b, the device protection function (interlock function) is activated and the PCS4b trips (forced stop).

The detection of the PCS4b excessive input is detected when the power sensor 5b shows a value equal to or higher than the rating of the PCS4b (step P1). In this embodiment, since there are positive and negative values between charging and discharging, it is preferable to make a determination based on an absolute value.

When the PCS4b excessive input is detected, the operation number of the PCS4a is reduced by one in step P2, so that the PCS4b excessive input state can be eliminated. That is, since the number of operating PCS4a is originally calculated by rounding up the decimal point in step S6, the power is reduced by the amount corresponding to the number after the decimal point, and as a result, the PCS4b excessive input is eliminated. This can also be realized by the control device 6, and since the PLC, which is the realization means, has a very high control cycle, it can be realized within about several tens to several hundreds of msec after detecting the PCS4b excessive input. If the processing is not in time, the PCS4b excessive input may be replaced with the case where a value close to the rating of the PCS4b is input when the storage battery 2 is charged. By doing so, there is time to spare, so that the charging power can be reliably reduced before the PCS4b trips. This has the effect of avoiding trips of PCS4b due to excessive input of PCS4b.

In step P2, the operation of reducing the number of operating PCS4a by one is calculated, but the number of operating PCS4a may be reduced by more than one according to the magnitude of the excessive input power of PCS4b.

Depending on the model of the PCS, when an excessive input occurs, the PCS is forcibly stopped by the interlock function. In that case, a manual return operation is required and the burden on the operator is heavy. Since trips can be avoided, the manual return operation of the operator becomes unnecessary, and the burden on the operator can be reduced.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Load 2 ... System power supply 3 ... Solar cells 4a, 4b ... PCS
5a, 5b, 5c ... Power sensor 6 ... Control device

Claims (3)

With multiple distributed power sources that output DC power,
A plurality of first power converters connected to each of the plurality of distributed power sources, output predetermined power, and connected in parallel with each other.
A second power converter that is connected in parallel with the plurality of first power converters and converts power into predetermined power in both directions.
A rechargeable and dischargeable storage battery connected to the second power converter,
The load supplied with power from the distributed power source and the storage battery at the time of discharge, and
A power value grasping means for measuring each of the output power value of the first power converter, the input / output power value of the second power converter, and the power supplied to the load.
One of the plurality of first power converters is operated in a rated manner so that the power supplied from the plurality of distributed power sources to the load is maximized, and the power supplied to the load and the charge / discharge power of the storage battery are used. The required number of operating units of the first power converter is obtained from the output power of the first power converter that has been rated and operated, and the first power converter corresponding to the required number of operating units is operated and supplied to the load. Output power to the remaining operating first power converter by prorating the difference between the power and the charge / discharge power of the storage battery and the output power of the first power converter that has been rated and operated. A power supply system with a control means that gives a value. The power supply system according to claim 1, wherein the control means preferentially operates the first power converter having a smaller number of operations among the plurality of first power converters. When the rated power capacity of the second power converter is smaller than the total rated power capacity of the plurality of first power converters.
The control means is used when the power value grasping means of the second power converter measures a charging power larger than the rated power capacity of the second power converter, or the rated power capacity of the second power converter. The power supply system according to claim 1 or 2, wherein the number of operating units of the required first power converter is reduced by one when the charging power having a value close to is measured.

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