Power supply system

A power supply system of an embodiment has a plurality of power conditioners, an acquisition device, and a search instruction generator. The power conditioners convert a form of electrical power generated by a plurality of electrical generators into a different form of electrical power. The acquisition device acquires a respective information regarding power output from each of the plurality of power conditioners. The search instruction generator generates and outputs an operating point search instruction to one or more power conditioners being lower in a ratio of output power with respect to a reference power by at least a prescribed degree than one or more different power conditioners, wherein the reference power is given, based on the maximum output power or rated power of the corresponding electrical generator, or based on the maximum output power or rated power of the power conditioner.

FIELD OF ART

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

BACKGROUND ART

Conventionally, a controller has been known in which an operating voltage at which the power of an electrical generator is maximum is determined as a voltage by a primary search operation, a search is performed by stepwise variation of the operating voltage with a primary operating voltage as a reference, and the operating voltage at which the electrical power is maximum is determined as a secondary search operating voltage. In this apparatus, because the operating voltage is searched for based on information of an electrical generator controlled by the apparatus itself, there has been a case in which it is not possible to appropriately set the search timing for the operating point.

PRIOR ART REFERENCES

Patent References

[Patent Reference 1] Japanese Patent Application Publication No. 2012-221151[Patent Reference 2] Japanese Patent Application Publication No. 2012-186263[Patent Reference 3] Japanese Patent Application Publication No. 2014-216507[Patent Reference 4] Japanese Patent Application Publication No. 2013-157595[Patent Reference 5] Japanese Patent Application Publication No. 2013-65797

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

The problem to be solved by the present invention is to provide a power supply system capable of more appropriately establishing the operating point search timing.

Means for Solving the Problem

A power supply system of an embodiment has a plurality of power conditioners, an acquisition device, and a search instruction generator. The power conditioners convert a form of electrical power generated by a plurality of electrical generators into a different form of electrical power. The acquisition device acquires a respective information regarding power output from each of the plurality of power conditioners. The search instruction generator makes reference to the respective information acquired by the acquisition device generates and outputs an operating point search instruction to one or more power conditioners being lower in a ratio of output power with respect to a reference power by at least a prescribed degree than one or more different power conditioners, the one or more different power conditioners and the one or more power conditioners being of the plurality of power conditioners, wherein the reference power is given, based on the maximum output power or rated power of the corresponding electrical generator, or based on the maximum output power or rated power of the power conditioner.

EMBODIMENTS

Power supply systems of embodiments are described below, with references made to the drawings.

First Embodiment

FIG. 1shows an example of the constitution of the power supply system1of the first embodiment. The power supply system1has the plurality of electrical generators10-1to10-8, and the power conditioners20-1and20-2. In the following, in the electrical generators10and the power conditioners20, unless a distinction is made, the hyphen (-) and the number following the hyphen in the reference symbol will be omitted. The power conditioners20-1and20-2are connected to a grid power source90. The power supply system1may have three or more power conditioners20.

The electrical generator10is, for example, a photovoltaic apparatus. The electrical generators10are electrically connected to a power conditioner20. For example, the electrical generators10-1and10-2and the electrical generators10-3and10-4are each connected in series. The series-connected electrical generators10-1and10-2(string) and the electrical generators10-3and10-4are connected with parallel with the power conditioner20-1. The electrical generators10convert sunlight energy to direct-current power, which is output to the power conditioners20. The electrical generator10, rather than a photovoltaic apparatus, may be another electrical generator of a type in which the output electrical power varies in accordance with the natural environment, such as wind-powered electrical generator or a geothermal electrical generator. In the following, the electrical generators10-1to10-4and the power conditioner20-1will be referred to as the electrical generating unit U-1and the electrical generators10-5to10-8and the power conditioner20-2will be referred to as the electrical generating unit U-2. In the following, unless a distinction is made between the electrical generating unit U-1and the electrical generating unit U-2they will be referred to simply as the electrical generating unit U. The electrical generators10-1to10-4are an example of “electrical generators corresponding” to the power conditioner20-1, and the electrical generators10-5to10-8are an example of “electrical generators corresponding” to the power conditioner20-2. A diode (not shown) may be connected in series with respect to series-connected electrical generators (a string), in which case the diode is connected in the direction outputting (allowing the flow of current) from the electrical generators to the power conditioner.

The grid power source90is, for example, an alternating-current power source supplied from an electrical power company. The grid power source is connected to, for example, a load using alternating current electrical power or, via a power conditioner of a type not shown inFIG. 1, a storage battery.

The power conditioner20, for example, may be a PCS (power conditioning system) that converts direct-current power generated by the electrical generator10to alternating-current power and outputs it to the grid power source90. In the first embodiment, the power conditioner20-1functions as a master apparatus, and the power conditioner20-2functions as a slave apparatus. In the following, the description will be of the power conditioner20-1, which is the master apparatus.

FIG. 2shows the functional constitution of the power conditioner20-1. The power conditioner20-1has a converter30, a controller40, and a communicator60.

The converter30, for example, has a non-illustrated DC (direct current)-to-DC converter, an inverter, and a driver or the like. The DC-DC converter converts the direct-current power input from the electrical generator10to direct-current electrical power of the desired current and voltage. The inverter has a plurality of switching elements and, by on-off controlling a switching element based on a gate control signal output from the driver, converts the direct-current electrical power converted by the DC-DC converter to alternating-current electrical power. The driver has a PWM (pulse width modulation) controller, a gate driver, or the like. The PWM controller, based on a signal input from the controller40, computes the on/off timing of the switching element. The PWM controller generates a PWM signal based on the computed on-off timing and outputs the PWM signal to the gate driver. The gate driver operates the switching element to turn in on and off based on the PWM signal generated by the PWM controller.

The controller40has a DC current detector42, a DC voltage detector, a central controller46, a search instruction generator48, a local search instruction generator49, an operating point searcher50, a storage52, an AC current detector54, and an AC voltage detector56. Of these functional parts, the central controller46, the search instruction generator48, the local search instruction generator49, and the operating point searcher50may be implemented, for example, by a processor such as a CPU (central processing unit) executing a program. These functional parts may also be implemented by hardware such as an LSI (large-scale integration) device, an ASIC (application-specific integrated circuit), or an FPGA (field-programmable gate array).

The storage52may be implemented, for example, by a ROM (read-only memory), a RAM (random-access memory), an HD (hard-disk) drive, or a flash memory. The power conditioner20-2, which is the slave, can be constituted with the search instruction generator48omitted from the constitution shown inFIG. 2.

The DC current detector42detects the current value of the DC electrical power output from the electrical generator10. The DC voltage detector44detects the voltage value of the DC electrical power output from the electrical generator10. An estimated value of a DC voltage or a DC current based on other detection information, circuit information, and control information may be used in controlling the central controller46. Detection information is internal temperature, external temperature, external humidity, and position (GPS) information and the like. Circuit information is the main circuit information for converting from the direct current of the power conditioner20to alternating current and is information such as the voltage and current peculiar to the circuit. Control information is a control variable of the power conditioner20, for example, PI control integrator information (where I indicates integral) to be used in voltage control and current control.

The AC current detector54detects the current value of the AC electrical power output from the converter30. The AC voltage detector56detects the voltage value of the AC electrical power output from the converter30. The AC voltage value and AC current value estimated based on other detection information, circuit information, and control information may be used in control by the central controller46.

The central controller46integrally controls the various parts and controls the operational state (operating or stopped) of the converter30. The central controller46calculates the alternating current electrical power, based on the current value detected by the AC current detector54and the voltage value detected by the AC voltage detector56. The alternating current electrical power corresponds to the output power of the converter30.

The search instruction generator48references the output power of the converter30and generates and outputs an operating point search instruction with respect to a converter30, of the plurality of converters30, that outputs a power that is a prescribed degree lower than the other converters30. More specifically, the search instruction generator48generates and outputs an operating point search instruction with respect to a converter30that has an output power with a ratio to a reference power that is a prescribed degree lower than the other converters30. The reference power may be the maximum output power or the rated output power of the electrical generator10, or the maximum output power or rated output power of the converter30. The reference power may be the limit value of the output power or a command value applied to the power conditioner20.

The local search instruction generator49, regardless of the operating point search instruction based on the determination result of the search instruction generator48, varies the operating point and moves the operating point (search) in the direction in which the output power increases. Because the current and voltage values of the power output by the electrical generator10vary depending upon the amount of sunlight and the temperature, the local search instruction generator49performs processing to vary the operating point with the set first period and move the operating point in the direction in which the output power increases.

The operating point searcher50, based on a search instruction generated by the search instruction generator48or the search instruction generated by the local search instruction generator49, searches for the operating point. The operating point, for example, is the point for performing maximum power point tracking (MPPT). The operating point searcher50, for example, while varying the output current and voltage of the converter30within a pre-established range, determines the operating point (output current and output voltage) at which the power output by the electrical generator10or the converter30is maximum. The search processing for the operating point by an instruction of the local search instruction generator49may be simpler than the search processing for the operating point by an instruction of the search instruction generator48. For example, it may be ended when a local maximum value is determined, or may search over a narrow range.

The storage52has stored therein a program that is executed by the central controller46, the search instruction generator48, the local search instruction generator49, or the operating point searcher50. The storage52also has stored therein the reference power.

Wireless communication is performed between the communicator60of the power conditioner20-1and the communicator60of the power conditioner20-2. For example, between the communicators60, communication is performed using the low-power wireless 920-MHz band or 2.4-GHz band. The communicator60acquires information (electrical generation information) regarding the power output by each of the plurality of power conditioners20. Between power conditioners20, communication may be performed by power line communication or via a network NW, such as a LAN (local area network), in which case the power conditioner20has a communication interface that handles each of the forms of communication.

FIG. 3is a flowchart showing the flow of processing executed by the controller40. This processing is repeatedly executed, for example, with a pre-established second time period. The second time period is, for example, longer than the first period.

First, the search instruction generator48selects one power conditioner20from the other power conditioners20or from the central controller46, and acquires the output power thereof (step S100) via the communicator60. Next, the search instruction generator48acquires from the storage52the reference power of the converter30thereof (step S102). Next, the search instruction generator48calculates the electrical generation ratio by dividing the output power of the converter30acquired at step S100by the reference power acquired at step S102(step S104). The electrical generation ratio may be acquired from the power conditioner20rather than by calculation from the output power and the reference power.

The details of the reference power will now be described. The reference power differs between the case in which the power that is generatable by the electrical generator10is smaller than the maximum power or rated power of the converter30and the case in which the power that is generatable by the electrical generator10is larger than the maximum power or rated power of the converter30. The reference power, for example, is determined by the output characteristics of the power conditioner20, which are dependent on the output characteristics of the electrical generator10or the converter30.

If the rated output power of the electrical generator10of the electrical generating unit U is smaller than the rated output power of the converter30, the reference power is determined by the output characteristics of the electrical generator10.FIG. 4shows an example of the output characteristics of an electrical generating unit U for the case in which the power that is generatable by the electrical generator10is smaller than the maximum power or rated power of the converter30. The drawing shows the output power during the times of the day that the electrical generating unit U is generating power over the period of one day. The example illustrated shows the case in which the prescribed irradiance energy at each time is imparted to the electrical generating unit U. The vertical axis represents the output power of the electrical generating unit U and the horizontal axis represents time. In this case, the reference power, for example, is established by the maximum output power or rated output power of the electrical generator10. The storage52includes a map, a function, or a table of data that returns the reference power of the electrical generator10.

However, if the rated output power of the electrical generator10of the electrical generating unit U is larger than the rated output power of the converter30, the reference power is determined by the output characteristics of the power conditioner20, which are dependent on the converter30.FIG. 5shows the output characteristics of the electrical generating unit U in the case in which the power that is generatable by the electrical generator10of the electrical generating unit U is larger than the power than the maximum power or rated power of the converter30. This drawing shows the output power during the times of the day that the electrical generating unit U is generating power over the period of one day. The example illustrated in this drawing shows the case in which the energy of a prescribed irradiance at each time is imparted to the electrical generating unit U. The vertical axis represents the output power of the electrical generating unit U and the horizontal axis represents time. The reference power, for example is established by the maximum output power or rated output power of the power conditioner20.

The electrical generation ratio determined at step S104is calculated by the search instruction generator48by dividing the output power of the electrical generating unit U by reference power (maximum output power or rated output power of the electrical generator10). The search instruction generator48, for example, references information stored in the storage52, derives the reference power of the electrical generator10, and calculates the electrical generation ratio by dividing the output power of the electrical generating unit U at that point in time by the reference power.

FIG. 6shows how the reference power Pref is established, based on the output characteristics of each electrical generating unit U. In this drawing, the premise is that each electrical generating unit U has the output characteristics shown inFIG. 4. The vertical axis represents the output power of the electrical generating unit U, and the horizontal axis represents time. This drawing shows the output power of the electrical generating unit U over one day. The trend curve L1shows the trend of output power of the electrical generating unit U1versus time. The trend curve L2shows the trend of the output power of the electrical generating unit U2versus time. The trend curve L3shows the trend of the output power of the electrical generating unit U3versus time. In the drawing, the maximum output powers of electrical generating units U1to U3are represented as Pref(U1), Pref(U2), and Pref(U3), respectively. The electrical generating unit U1, for example, because it faces Eastward, has a large electrical generation amount in the morning. The electrical generating unit U2, for example, because it faces Westward, has a large electrical generation amount in the afternoon. The electrical generating unit U3, for example, faces Southward and has a maximum output power that is larger than that of the electrical generating units U1and U2. In this case, the reference power Pref(U1) is established as the output power at the time at which the trend curve L1is the maximum value during one day. The reference power Pref(U2) is established as the output power at the time at which the trend curve L2is the maximum value during one day. The reference power Pref(U3) is established as the output power at the time at which the trend curve L3is the maximum value during one day.

The electrical generation ratio is determined based on the reference power Pref established for each of the electrical generating units U.FIG. 7shows an example of the power generation calculation method for the case in which the output characteristics differ between the power conditioners20. The Pref(U1), Pref(U2), and Pref(U3) of the electrical generating units U1, U2, and U3indicate the reference powers of the electrical generating units U1, U2, and U3, respectively. The search instruction generator48, for example, determines the electrical generation ratio of the electrical generating unit U1based on the reference power Pref(U1) and the output power of the electrical generating unit U1at that point in time. The search instruction generator48, for example, determines the electrical generation ratio of the electrical generating unit U2based on the reference power Pref(U2) and the output power of the electrical generating unit U2at that point in time. The search instruction generator48, for example, determines the electrical generation ratio of the electrical generating unit U3based on the reference power Pref(U3) and the output power of the electrical generating unit U3at that point in time.

Next, the search instruction generator48determines whether or not the electrical generation ratios of all the electrical generating unit U (for example, U1, U2, and U3) have been acquired (step S106) If the electrical generation ratios of all the electrical generating units U have not been acquired, return is made to the processing of step S100, the next power conditioner20is selected, and the output power thereof is acquired.

If the electrical generation ratios of all electrical generating units U have been acquired, the search instruction generator48compares the electrical generation ratios between electrical generating units U and determines whether or not there is an electrical generating unit U having an electrical generation ratio that is lower by at least a prescribed degree than the electrical generation ratio of the other electrical generating units U (step S108). For example, the search instruction generator48determines whether or not there is an electrical generating unit U among the electrical generating units U of which the electrical generation ratio was calculated having an electrical generation ratio that is at least a prescribed degree lower. “An electrical generation ratio that is at least a prescribed degree lower” is, for example, if the electrical generation ratios are taken as a data set, a deviation from a representative value of at least α standard deviations (σ), where α may be established arbitrarily in the range of approximately 1 to 3. The search instruction generator48may use a known method such as Smirnov-Grubbs to determine whether or not a calculated electrical generation ratio is an outlying value. If the determination is that the calculated electrical generation ratio is an outlying value, the search instruction generator48determines that the calculated electrical generation ratio is an electrical generation ratio that is the prescribed degree lower. As described above, although there are cases in which the output characteristics will differ between individual electrical generating units U, depending upon the installation location and direction, the search instruction generator48sets the threshold with respect to the deviation for determining an outlier so that it is not affected by a difference in output characteristics dependent upon the installation location or direction.

The search instruction generator48may group the electrical generating units U, for example in accordance with the trends in output characteristics, and determine whether or not, among the grouped electrical generating units U, there exists an electrical generating unit U having an electrical generation ratio that is at least a prescribed degree lower. The trends in the output characteristics are trends that classify, for example, into a type that generates a lot during the morning and a type that generates a lot during the afternoon. For example, the search instruction generator48groups the electrical generating units U into electrical generating units U that output the maximum power in the morning and electrical generating units U that output the maximum power in the afternoon. By grouping the electrical generating units U in accordance with the trends of their output characteristics, the search instruction generator48can control the occurrence of erroneous detection because of time-dependent differences in output characteristics and can more accurately detect abnormalities.

If no electrical generating unit U exists having an electrical generation ratio that is lower by a prescribed degree, the processing of this flowchart ends. If an electrical generating unit U exists having an electrical generation ratio that is lower by a prescribed degree, the search instruction generator48generates a search instruction signal (step S110). The search instruction signal gives an instruction to search for an operating point in a range that is set in the operating point searcher50. Details of this will be described later. Next, the search instruction generator48transmits the generated search instruction signal to the electrical generating unit U that was judged at step S108to have an electrical generation ratio that is lower by a prescribed degree (step S112). This ends the processing of this flowchart.

The reference power is not restricted to being the maximum output power of that electrical generating unit U, and may be the rated output power of the electrical generating unit U. The reference power, for example, may be the maximum output power or rated output power for each time at which there is the ideal sunlight, in which case the reference power is a value that varies with time.

FIG. 8is a flowchart showing the flow of processing executed when the power conditioner20receives a search instruction signal. First, the central processor46determines whether or not a search instruction signal has been received (step S150). If a search instruction signal has not been received, the routine of this flowchart is ended.

If a search instruction signal has been received, the operating point searcher50searches for an operating point in a set voltage range Vr (step S152).FIG. 9describes the operating point search executed by the operating point searcher50. The vertical axis represents the output power of the electrical generating unit U (electrical generator10), and the horizontal axis represents the output voltage of the electrical generator10. As shown in this drawing, a plurality of points appear at which the output power is large. This is the influence of a partial shadow in the sunlight on a sub-string connected in series within the electrical generator10. A sub-string has a plurality of solar cells that are series connected and a bypass diode to prevent the flow of a reverse current, connected in parallel with the series-connected solar cells. If there is a shadow on a part of a sub-string, because there is a circulated current in the bypass diode, a number of points appear at which the output voltage is large. In that case, there is the case in which a point Pc at which the output power is smaller than Pmax, at which the output voltage is maximum, is set as the operating point. When the search instruction signal is received, the operating point searcher50of the present embodiment searches for the operating point in the set voltage range Vr. As a result, the operating point searcher50can derive the point Pmax at which the output voltage is maximum.

Next, the central processor46operates the electrical generator10at the operating point found by the operating point searcher50(step S154). This ends the routine of this flowchart.

For example, in order to determine whether or not the current operating point enables the maximum output power, if the operating point is searched for with a prescribed time interval, there is a case in which a search for the operating point is done regardless of the current operating point being the operating point enabling the maximum output power. In this case, because some prescribed amount of time is required to perform an operating point search with respect to a prescribed voltage range, there have been cases in which the amount of electrical generation has decreased.

In contrast, the power conditioner20-1of the present embodiment transmits a search instruction signal to an electrical generating unit U having an electrical generation ratio that is lower by a prescribed degree. This, by the power conditioner20of the electrical generating unit U that has a low electrical generation ratio performing a search for the operating point with respect to a prescribed voltage range, the operating point enabling the maximum power output can be found. As a result, the power conditioner20-1can suppress a reduction in electrical generation amount caused by unnecessary operating point searching. The power conditioner20-1can also cause the electrical generator10to operate at an operating point having a higher electrical generation ratio.

In the present embodiment, although the power conditioner20-1functions as a master apparatus, and the power conditioner20-2functions as a slave apparatus, each of the power conditioner20-1and the power conditioner20-2may function as a master apparatus provided with a search instruction generator48. In that case, each of the power conditioner20-1and the power conditioner20-2compares the electrical generation ratio of the other power conditioner with its own electrical generation ratio and, if its own electrical generation ratio is low, causes its own local search instruction generator49to search for the operating point.

According to the above-described power supply system of the first embodiment, the search instruction generator48references the output power of the power conditioners20acquired by the communicator60, the AC current detector54and the AC voltage detector56and, with respect to a power conditioner20of the plurality of power conditioners20that has an output power that is a prescribed degree lower than the other power conditioners20, generates and outputs a search instruction to search for the operating point, thereby enabling more appropriate establishment of the timing of the search for the operating point.

Second Embodiment

The second embodiment will now be described. The points of difference from the first embodiment will be the focus of the description, and functions and the like that are in common with the first embodiment will be omitted. In the second embodiment, a monitoring apparatus100references the output power of the power conditioners20and, with respect to a power conditioner20that has an output power that is at least a prescribed degree lower than the other power conditioners20, an operating point search instruction is generated and output.

FIG. 10shows an example of the constitution of a power supply system1A of the second embodiment. The power supply system1A, in addition to an electrical generating unit U1A that includes electrical generators10-1A to10-4A and a power conditioner20-1A and an electrical generating unit U1A that includes electrical generators10-5A to10-8A and a power conditioner20-1A, has a monitoring apparatus100.

The monitoring apparatus100has, for example, a monitor-side communicator102, a network communicator104, a monitor-side search instruction generator106, a display108, and a monitor-side storage110. The monitor-side communicator102communicates with the communicator60of the power conditioners20via a network NW, such as a LAN. The network communicator104is a communication interface capable of connection to an external network NW.

The monitor-side search instruction generator106references the output power acquired from the power conditioners20and, of the plurality of power conditioners20, generates and outputs to a power conditioner20that has an output power that is at least a prescribed degree lower than the other power conditioners20an operating point search instruction.

The display108is a display device such as an LED digital display having a plurality of segments, and LCD (liquid crystal display), or an organic EL (electroluminescence) display. The display108displays the output power and the like acquired from each of the power conditioners20.

The monitor-side storage110stores a program that is executed by the monitor-side search instruction generator106. The monitor-side storage110also stores information of the reference power of each of the power conditioners20.

The power conditioners20-1A and20-2A of the present embodiment, with the exception of having the search instruction generators48, have the same constitutions as the power conditioner20-1of the first embodiment.

FIG. 11is a flowchart showing a variation example of the flow of processing executed by the monitoring apparatus100. In this processing, if a set time is reached and also the generated power is at least a threshold Th, a determination is made of whether or not there exists an electrical generating unit U having a low electrical generation ratio.

First, the monitor-side search instruction generator106determines whether or not the set time has been reached (step S200). If the set time has not been reached, the routine of this flowchart ends. If the set time has been reach, the monitor-side search instruction generator106determines whether or not the referenced generated power is at least the threshold Th (step S202). The referenced generated power can be the generated power of one of the electrical generating unit U1A and the electrical generating unit U2A, or can be the combined calculated generated power of both thereof.

FIG. 12describes the set time and the generated electrical power. The vertical axis represents power, and the horizontal axis represents the time t. In this drawing, GP indicates the generated power, and D indicates the power demand. For example, the period from1100to1300, in which the power demand is low during the day, is taken to be the set time in step S200. A power that is greater than the power demand is taken as the threshold Th. By doing this, even if the power conditioner20performs a search for the operating point, because there is a generated power margin, a decrease in the supply of power can be suppressed.

If the referenced generated power is below the threshold Th, the routine of the flowchart ends. If, however, the referenced generated power is at least the threshold Th, the monitor-side search instruction generator106, via the monitor-side communicator102, selects one power conditioner20from the other power conditioners20and acquires the output power thereof (step S204). Next, the monitor-side search instruction generator106acquires from the monitor-side storage110the reference power corresponding to that power conditioner20(step S206). Next, the monitor-side search instruction generator106divides the output power of the power conditioner20acquired at step S106by the reference power acquired at step S206to calculate the electrical generation ratio (step S208). Next, the monitor-side search instruction generator106determines whether or not the electrical generation ratios of all the electrical generating units U have been acquired (step S210). If the electrical generation ratios of all the electrical generating units U have not been acquired, return is made to the processing of step S204, and the next power conditioner20is selected, and the output power thereof is acquired.

If the electrical generation ratios of all the electrical generating units U have been acquired, the monitor-side search instruction generator106compares the electrical generation ratios between the electrical generating units U and determines whether or not there exists an electrical generating unit U having an electrical generation ratio that is at least the prescribed degree lower (step S212). If there is no electrical generating unit U having an electrical generation ratio that is at least the prescribed degree lower, the processing of the routine of this flowchart ends. If there is an electrical generating unit U having an electrical generation ratio that is at least the prescribed degree lower, the monitor-side search instruction generator106generates a search instruction signal (step S214). Next, the monitor-side search instruction generator106transmits the generated search instruction signal to the electrical generating unit having the low electrical generation ratio (step S216). This ends the processing of the routine of this flowchart this flowchart.

Although, in the present embodiment, in the case in which the set time has been reached and also the reference generated power is at least the threshold Th, a determination was made of whether or not there exists an electrical generating unit U with a low electrical generation ratio, if the set time has been reached or the referenced generated power is at least the threshold Th, the monitoring apparatus100may determine at a set interval whether or not there exists an electrical generating unit U having a low electrical generation ratio. If the set time has been reached, a signal for causing a search for the operating point in the set voltage range Vr is transmitted to the power conditioner20, and if the set has time has not been reached, a determination may be made of whether or not there exists an electrical generating unit having a low electrical generation ratio.

According to the above-described power supply system1A of the second embodiment, the monitoring apparatus100references the output power of the power conditioners20acquired by the monitor-side communicator102and, of the plurality of power conditioners20, generates and outputs an operating point search instruction to a power conditioner20that has an electrical generation ratio that is at least a prescribed degree lower than that of the other power conditioners, thereby enabling more appropriate establishment of the timing of the search for the operating point.

Third Embodiment

The third embodiment will now be described. The points of difference from the first embodiment will be the focus of the description, and functions and the like that are in common with the first embodiment will be omitted. In the third embodiment, the power conditioner20-1B and20-2B each having a plurality of converters30(not shown) is different from the first embodiment.

FIG. 13shows an example of the constitution of a power supply system1B of the third embodiment. The power supply system1B of the third embodiment has electrical generators10-1B to10-8B and power conditioners20-1B and20-2B. The electrical generators10-1B and10-2B,10-3B and10-4B,10-5B and106B, and10-7B and10-8B are each connected in series. In the following, two electrical generators10connected in series (as a string) will be called an electrical generator group.

The power conditioner20-1B and20-2B have a plurality of converters30. The converters30have a one-to-one correspondence with the electrical generator groups. For example, the DC current output by the electrical generator group of the electrical generators10-1B and10-2B is input to the input1n1of a converter30of the power conditioner20-1B. For example, the DC current output by the electrical generator group of the electrical generators10-3B and10-4B is input to the input1n2of the converter30that is different from the converter30corresponding to the input1n1of the power conditioner20-1B. The power conditioners20-1B and20-2B search for an operating point in units of electrical generator groups. The power conditioners20-1B and20-2B can, for electrical generator groups having output voltages that are different with respect to an operating point at which the output power of the electrical generator10is maximum, search for the operating point in accordance to each thereof. As a result, the power conditioner20-1B and20-2B can more appropriately establish the timing of the search for the operating points for each of the electrical generator groups.

The search instruction generator48references the output power of the converters30and, of the plurality of converters30, generates and outputs an operating point search instruction with respect to a converter30having an output power that is lower than the other converters30by a prescribed degree. The reference power is the rated output power of the converter30with respect to each input to which a DC current is input from an electrical generator group.

According to the above-described power conditioners20of the third embodiment, because the power conditioners20can, for electrical generator groups having output voltages that are different with respect to an operating point at which the output power of the electrical generator10is maximum, search for the operating point in accordance to each thereof, they can more appropriately establish the timing of the operating point search.

Fourth Embodiment

The fourth embodiment will now be described. The points of difference from the first embodiment will be the focus of the description, and functions and the like that are in common with the first embodiment will be omitted. In the fourth embodiment, a power conditioner20being provided for each string and an inverter (string inverter) that converts the DC power output from the electrical generators10included in a string to AC power are the differences from the first embodiment.

FIG. 14shows an example of the constitution of a power supply system1C of the fourth embodiment. The power supply system1C has electrical generators10-1C to10-4C and power conditioners20-1C and20-2C. The electrical generators10-1C and10-2C are connected in series, and the output terminals of the electrical generators10-1C and10-2C are connected to the power conditioner20-1C. The electrical generators10-3C and10-4C are connected in series, and the output terminals of the electrical generators10-3C and10-4C are connected to the power conditioner20-2C.

The converters30of the power conditioners20-1C and20-2C are string inverters that convert DC power to AC power. The string inverters search for the operating point and perform power conditioning for each of the series-connected electrical generators10-1C and10-2C and the series-connected electrical generators10-3C and10-4C.

According to the power conditioners20of the above-described fourth embodiment, because operating point searching and power conditioning are done for each group of series-connected electrical generators10, the timing of search for the operating point for each group of individual electrical generator10can be more appropriately established.

Fifth Embodiment

The fifth embodiment will now be described. The points of difference from the fourth embodiment will be the focus of the description, and functions and the like that are in common with the fourth embodiment will be omitted.FIG. 15shows an example of the constitution of a power supply system1D of the fifth embodiment. The power supply system1D has an electrical generator10-1D, a power conditioner20-1D that is electrically connected to the electrical generator10-1D, an electrical generator10-2D, and a power conditioner20-2D that is electrically connected to the electrical generator10-2D. The power conditioners20-1D and20-2D of the fifth embodiment are each paired with an electrical generator10, and these pairs operate in parallel. The power conditioners20-1D and20-2D are so-called micro-inverters, which convert the DC power output from the electrical generators10to AC power.

The monitor-side search instruction generator106of the monitoring apparatus100D acquires the output powers from the power conditioners20and generates and outputs an operating point search instruction with respect to a power conditioner20, of the plurality of power conditioners20, that has an output power that is lower than other power conditioners20by at least a prescribed degree.

According to the above-described power supply system1D of the fifth embodiment, because the monitoring apparatus100D determines whether there exists an electrical generating unit U having an electrical generation ratio lower than a set value, the processing burden on the power conditioner20can be reduced.

Sixth Embodiment

Next, the sixth embodiment will be described. The points of difference from the second embodiment will be the focus of the description, and functions and the like that are in common with the second embodiment will be omitted. In the sixth embodiment, the electrical generation controller120searches for the operating point of the electrical generator10.

FIG. 16shows an example of the constitution of a power supply system1E of the sixth embodiment. The power supply system1E has an electrical generator10-1E, an electrical generation controller120-1electrically connected to the electrical generator10-1E, an electrical generator10-2E, an electrical generation controller120-2electrically connected to the electrical generator10-2E, and a power conditioner20E electrically connected to the electrical generation controllers120-1and120-2. The power supply system1E also has a monitoring apparatus100E that communicates with the electrical generation controller120-1and the electrical generation controller120-2. In the following, unless there is a distinction made between the electrical generation controllers120-1and120-2, they will be referred to as the electrical generation controller120.

FIG. 17shows the functional constitution of the electrical generation controller120. The electrical generation controller120has a controller-side communicator122, a DC-DC converter124, and an electrical generation unit126. The controller-side communicator122, for example, communicates wirelessly with the monitor-side communicator102of the monitoring apparatus100. The DC-DC converter124converts DC power to DC power of a prescribed current and voltage, based on control by the electrical generation unit126, and outputs the result to the electrical generator10. The electrical generation unit126controls the DC-DC converter124and searches for the operating point.

The monitor-side search instruction generator106of the monitoring apparatus100E references the output power of the electrical generation controller120acquired by the monitor-side communicator102and generates and outputs an operating point search instruction to an electrical generation controller120, of a plurality of electrical generation controllers,120that has an output power that is a prescribed degree lower than that of the other electrical generation controllers120, thereby enabling more appropriate establishment of the timing of the operating point search.

FIG. 18shows an example of the constitution of the power supply system1E of a variation example of the sixth embodiment. As shown in the drawing, the electrical generation controllers120may transmit and receive data with the monitoring apparatus100via the power conditioner20.

According to the above-described power supply system1E, because the electrical generation controller120controls the electrical generators10, the constitution of the power conditioner20can be made simpler.

Seventh Embodiment

Next, the seventh embodiment will be described. The points of difference from the second embodiment will be the focus of the description, and functions and the like that are in common with the second embodiment will be omitted. In the present embodiment, a monitoring apparatus100F and a plurality of power supply systems1F-1to1F-n (not shown) are connected to a network NW. In the following, unless a distinction is made between the power supply systems1F-1to1F-n, the will be referred to as a power supply system1F.

FIG. 19shows an example of the constitution of a power supply system1F of the seventh embodiment. In the present embodiment, the power supply system1F has a position identifier130. The position identifier130, for example, receives radio signals from a plurality of GPS (Global Positioning System) satellites. The position identifier130, based on the received radio signals, identifies its own position by performing a position-finding computation. The position identifier130transmits its own position to the monitoring apparatus100F via the network NW.

The monitor-side search instruction generator106of the monitoring apparatus100, based on the acquired position information, acquires, via the network NW, the output power of the power conditioners20belonging to a power supply system1F that is different from the control target installed in the vicinity of the acquired position. The relationship of correspondence between the plurality of power supply systems1F and the position information is stored, for example, in the storage52. The relationship of correspondence between the plurality of power supply systems1F and the position information is acquired from a host apparatus connected to the network NW. The monitor-side search instruction generator106, for example via a network NW, acquires the output power of an electrical generating unit U of the control target power supply system1F and power supply system1F different from the control target. The monitor-side search instruction generator106calculates the electrical generation ratio, based on the output power acquired from the power supply system1F and the reference power of the electrical generator10or power conditioner20of the electrical generating unit U. The monitor-side search instruction generator106compares the calculated electrical generation ratios and determines whether or not there exists an electrical generating unit U having an electrical generation ratio lower by a prescribed degree. If a power supply system1F exists having an electrical generation ratio lower by a prescribed degree, the monitor-side search instruction generator106generates and outputs an operating point search instruction to the power conditioner20of the electrical generating unit U that has an electrical generation ratio lower by the prescribed degree.

According to the above-described power supply system1F of the seventh embodiment, based on the acquired position information, the electrical generation ratio of a power supply system1F installed in the vicinity of the control target power supply system1F and the electrical generation ratio of the control target power supply system1F are compared and a determination is made of whether or not there exists an electrical generating unit U having an electrical generation ratio that is lower by a prescribed degree. This enables the power supply system1F to more appropriately establish the timing of a search for the operating point.

Eighth Embodiment

Next, the eight embodiment will be described. The points of difference from the first embodiment will be the focus of the description, and functions and the like that are in common with the first embodiment will be omitted. In the first embodiment, if the electrical generation ratios of all of the electrical generating units U have been acquired, the search instruction generator48compares the electrical generation ratios of the electrical generating units U and determines whether or not an electrical generating unit U having an electrical generation ratio that is lower by a prescribed degree exists. In contrast, in the eighth embodiment, in the power supply system1, if there is a mixture of power conditioners20for which the reference power is the maximum output power or rated output power of the electrical generator10and power conditioners20for which the reference power is the maximum output power or rated output power of the converter30, the search instruction generator48compares the electrical generation ratios between electrical generating units U, excluding electrical generating units U that satisfy a prescribed condition (for example, those electrical generating units U having the output characteristics of the converter30taken as the reference power and having an electrical generation ratio of 100%) and determines whether or not there exists an electrical generating unit U having an electrical generation ratio that is lower by a prescribed degree.

The power supply system1of the present embodiment has a plurality of electrical generating units U. In the electrical generating units U, for example, a power conditioner20and an electrical generator10are paired. Of the electrical generating units U, the reference power of the power conditioner20included in at least one electrical generating unit U is the maximum output power or rated output power of the electrical generator10, and the reference power of the power conditioner20included in at least one electrical generating unit U is the maximum output power or rated output power of the converter30. The storage52of the present embodiment has stored therein as reference power information the type of reference power of each of the electrical generating units U, associated therewith. The type of the reference power is information of whether the maximum output power or rated output power of the electrical generator10or the maximum output power or rated output power of the converter30.

FIG. 20is a flowchart showing the flow of processing executed by the controller40of the eighth embodiment. This processing is executed repeatedly, for example with a pre-established second period. The second time period is, for example, longer than the first period.

First, the search instruction generator48selects one power conditioner20from the other power conditioners20or from the central controller46and acquires the output power thereof (step S300) via the communicator60. Next, the search instruction generator48acquires from the storage52the reference power of the converter30thereof (step S302). next, the search instruction generator48acquires from the storage52the type of reference power corresponding to that converter30(step S304). Next, the search instruction generator48calculates the electrical generation ratio by dividing the output power of the converter30acquired at step S300by the reference power acquired at step S302(step S306).

Next, the search instruction generator48determines whether or not the electrical generation ratios of all electrical generating units U have been acquired (step S308). If the electrical generation ratios of all the electrical generating units U have been not acquired, return is made to step S300, the next power conditioner20is selected, and the output power thereof is acquired.

If the electrical generation ratios of all the electrical generating units U have been acquired, the search instruction generator48excludes electrical generating units U that have an electrical generation ratio of 100% from among electrical generating units U that have the maximum output power or rated output power (output characteristics) of the converter30as the reference power (step S310). This excludes from monitoring the “electrical generating units U that have an electrical generation ratio of 100%.” In this processing, “electrical generating units U that have an electrical generation ratio of 100%,” may, for example, be replaced by “electrical generating units U that have an electrical generation ratio of 99.5% or greater.” Next, the search instruction generator48compares the electrical generation ratios between the electrical generating units U that were not excluded at step S310, and determines whether or not there exists an electrical generating unit U having an electrical generation ratio that is at least a prescribed degree lower (step S312).

If there is no electrical generating unit U having an electrical generation ratio that is lower by a prescribed degree, the processing of this flowchart ends. If there exists an electrical generating unit U having an electrical generation ratio that is lower by a prescribed degree, the search instruction generator48generates a search instruction signal (step S314). Next, the search instruction generator48transmits the generated search instruction signal to the electrical generating unit U that was judged to have an electrical generation ratio lower by a prescribed degree (step S316). This ends the processing of this flowchart.

FIG. 21describes an excluded electrical generating unit U. In the drawing, the vertical axis represents the electrical generation ratio (%), and the horizontal axis represents time (t). The trend curve L4shows the output characteristics of an electrical generating unit U when the power that is generatable by the electrical generator10of the electrical generating unit U is lower than the maximum power or rated power of the converter30. The trend curve L5shows the output characteristics of the electrical generating unit U when the power that is generatable by the electrical generator10of the electrical generating unit U is greater than the power than the maximum output power or rated power the converter30. In this case, the reference power is established, for example, by the maximum output power or rated output power of the power conditioner20.

As shown in the drawing, during the time D the electrical generation ratio of the trend curve L5is 100%. In this time period, an electrical generating unit U corresponding to the trend curve L5is excluded from monitoring. This is because, if there is a case where there is a spread between the power by the electrical generator10included in an electrical generating unit U corresponding to the trend curve L5and the power converted by the converter30of the power conditioner20, making it impossible to determine with good accuracy whether or not the electrical generation ratio of an electrical generating unit U corresponding to the trend curve L5is low. As described below, this is also to remove it from being compared with the other electrical generating units U.

Consider the case in which the power that is generatable by the electrical generator10eliminates the processing (the processing of the above-described step S310) to exclude an electrical generating unit U that can output a power large than the converter30and also has an electrical generation ratio of 100%. In this case, because the reference power is the maximum output power or rated output power of the converter30, the power actually output by the electrical generator10might be greater than the reference power. If an electrical generating unit U in which there is a spread between the power output by the electrical generator10and the power output by the converter30, is made a target of comparison with other electrical generating units U, it could be impossible to judge with good accuracy whether or not there exists an electrical generating unit U having a low electrical generation ratio.

In contrast, in the present embodiment, by excluding electrical generating units U having a electrical generation ratio of 100%, electrical generating units U in which a spread does not occur between the power output by the electrical generator10and the power output by the converter30are taken as targets for comparison with other electrical generating units U. This enables the power supply system1to determine with accuracy whether or not there exists an electrical generating unit U having a low electrical generation ratio.

More specifically, the search instruction generator48, for example, derives a representative value from all the electrical generation ratios, compares the representative value with the electrical generation ratio of the target electrical generating unit U and, if there is an abnormality in the electrical generating unit U, unless an electrical generating unit U having an electrical generation ratio of 100% is excluded, there is a case in which the representative value differs from the case in which the electrical generation ratio actually output by the electrical generator10is taken into account. In the present embodiment, because only the electrical generation ratio derived from the power actually output by the electrical generator10, it is possible to determine with better accuracy whether or not there exists an electrical generating unit U having a low electrical generation ratio.

If the reference power is the maximum output power or rated output power of the electrical generator10, the electrical generator10might output a power that exceeds the maximum output power or rated output power, in which case the electrical generators10of other electrical generating units U operate in the same environment (for example, luminance and temperature). If the maximum output power or rated output power of the power conditioner20is greater than power output by the electrical generator10, the power output by the electrical generator10is output without limiting. For that reason, the power supply system1can determine with good accuracy whether or not there exists an electrical generating unit U having a low electrical generation ratio, without excluding electrical generating units U having an electrical generation ratio of 100% or greater than 100%.

According to the above-described eighth embodiment, the search instruction generator48, by excluding electrical generating units U satisfying a prescribed condition in determining whether or not there is an electrical generating unit U having an electrical generation ratio that is lower by a prescribed degree, a more accurate determination can be made of whether or not there exists an electrical generating unit U with a low electrical generation ratio.

The constitutions of the first to the eighth embodiments described above may be arbitrarily combined. For example, in the power supply system1, of the power conditioners20-1A and20-1B (various central inverters), the power conditioner20-1C (string inverter), the power conditioner20-1D (micro-inverter), and the electrical generation controller120(power optimizer or the like), different power-changing apparatuses may be combined for use.

According to at least one above-described embodiment, by having a plurality of power conditioners (20,30,120) that convert a form of electrical power generated by a plurality of electrical generators into a different form of electrical power; an acquisition device that acquires a respective information regarding power output from each of the plurality of power conditioners; a search instruction generator that makes reference to the respective information acquired by the acquisition device generates and outputs an operating point search instruction to one or more power conditioners being lower in a ratio of output power with respect to a reference power by at least a prescribed degree than one or more different power conditioners, the one or more different power conditioners and the one or more power conditioners being of the plurality of power conditioners, wherein the reference power is given, based on the maximum output power or rated power of the corresponding electrical generator, or based on the maximum output power or rated power of the power conditioner, the timing of search for an operating point can be established more appropriately. Although the reference power is made the rated power or the maximum output power, it may be based on a difference index. For example, it may be a power in the NOCT (nominal operation condition temperature).