Power conversion system

Abstract

To provide a power conversion system that employs a different structure from those of conventional technologies.SOLUTION: A power conversion system 100 includes: a DC / DC converter 1 connected to a power storage device BT; and a PCS 4 to which first DC power (e.g., Ppv) is supplied from a renewable energy generating device RE. The DC / DC converter 1 outputs, as compensation power for the first DC power, second DC power to the PCS 4 by converting DC power supplied from the power storage device BT, and determines the second DC power based on power difference that is the difference between the first DC power and the maximum power point power of the renewable energy generating device RE.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] One aspect of the present invention relates to a power conversion system. [Background technology]

[0002] Patent Document 1 listed below discloses an example configuration of a power conversion system that converts DC power supplied from a renewable energy power generation device and another DC power supplied from a power storage device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-137293 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one aspect of the present invention is to provide a power conversion system having a different configuration from the conventional one. [Means for solving the problem]

[0005] In order to solve the above problems, a power conversion system according to one embodiment of the present invention includes a DC / DC converter connected to a power storage device, and a PCS supplied with first DC power from a renewable energy power generation device, wherein the DC / DC converter converts the DC power supplied from the power storage device to output a second DC power to the PCS as compensation power for the first DC power, and determines the second DC power based on a differential power which is a difference between the first DC power and a maximum power point power of the renewable energy power generation device. Effect of the Invention

[0006] According to one aspect of the present invention, it is possible to provide a power conversion system having a configuration different from that of the conventional one. [Brief description of the drawings]

[0007] [Figure 1] 1 shows a configuration example of a power conversion system according to a first embodiment. [Diagram 2] 3 shows an example of the configuration of a control unit in the DC converter of the first embodiment. [Diagram 3] 4 illustrates an example of how signal values ​​change over time in a power conversion system. [Figure 4] FIG. 13 is a diagram for explaining the correspondence relationship between Ppvmax and Ppcs. [Diagram 5] 1 shows an example of MPPT control in a power conversion system. [Figure 6] FIG. 1 is a diagram for explaining a tracking method in MPPT control. [Figure 7] Examples of Ts and Tp are given below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Embodiment 1] The power conversion system 100 of the first embodiment will be described below. For convenience of explanation, components having the same functions as those described in the first embodiment will be denoted by the same reference numerals in the following embodiments, and the explanations thereof will not be repeated. For the sake of brevity, the explanations of known technical matters will also be omitted as appropriate.

[0009] Each component, material, and numerical value described in this specification is merely an example unless otherwise inconsistent. Therefore, for example, the positional relationship and connection relationship of each component are not limited to the examples in each figure unless otherwise inconsistent. In addition, each figure is not necessarily illustrated according to scale. In this specification, the term "connected" means "electrically connected" unless otherwise inconsistent.

[0010] (One configuration example of the power conversion system 100) Fig. 1 shows a configuration example of a power conversion system 100. Fig. 1 shows a schematic diagram of the power conversion system 100 and its surrounding elements. As shown in Fig. 1, the power conversion system 100 includes a DC / DC converter 1 and a PCS (Power Conditioning System) 4. The power conversion system 100 may be connected to a commercial power system PW external to the power conversion system 100.

[0011] The DC / DC converter 1 is connected to a power storage device BT. The DC / DC converter 1 has a control unit 10 that controls its own power conversion operation. FIG. 2 shows an example of the configuration of the control unit 10. The control unit 10 will be described in detail later. The power storage device BT has a storage battery that stores or charges DC power. Therefore, the power storage device BT can supply DC power to the DC / DC converter 1.

[0012] In the example of FIG. 1, the PCS 4 is connected to a commercial grid PW. The PCS 4 converts DC power into AC power. As shown in FIG. 1, the PCS 4 is also connected to a renewable energy power generation device RE. The renewable energy power generation device RE may be any device capable of outputting DC power.

[0013] In this specification, the DC power output from the renewable energy power generation device RE is referred to as the first DC power. In the first embodiment, the renewable energy power generation device RE is a solar power generation device. For this reason, in FIG. 1, the DC power output from the renewable energy power generation device RE is written as Ppv. Ppv is an example of the first DC power.

[0014] 1, the power storage device BT and the renewable energy power generation device RE are illustrated as external components of the power conversion system 100. However, as will be apparent to those skilled in the art, at least one of the power storage device BT and the renewable energy power generation device RE may be an internal component of the power conversion system 100. Thus, for example, the power conversion system 100 may have the power storage device BT and the renewable energy power generation device RE.

[0015] The PCS 4 in the example of Fig. 1 is also connected to a DC / DC converter 1. The DC / DC converter 1 may output another DC power Pdd by converting the DC power supplied from the power storage device BT. The DC / DC converter 1 may output a second DC power to the PCS 4 as a compensation power for the first DC power (e.g., Ppv). Pdd is an example of the second DC power.

[0016] As is clear from the above description, when Pdd is positive, it indicates that the power storage device BT is discharging. On the other hand, when Pdd is negative, it indicates that DC power is being supplied from the DC / DC converter 1 to the power storage device BT (i.e., the power storage device BT is charging). Also, when Pdd is 0, it indicates that the power storage device BT is in a resting state.

[0017] In the example of Fig. 1, the PCS 4 is supplied with Ppv from the renewable energy power generation device RE and with Pdd from the DC / DC converter 1. In this specification, the DC power input to the PCS 4 is denoted as Ppcs. Ppcs is also referred to as PCS input power. In the example of Fig. 1, Ppcs is expressed as the sum of Ppv and Pdd. As an example, the PCS 4 may convert Ppcs into AC power of a predetermined commercial frequency.

[0018] 1, the power conversion system 100 may include a voltage sensor 91V and a current sensor 92A. The voltage sensor 91V detects a DC voltage Vpv output by the renewable energy power generation device RE. The current sensor 92A detects a DC current Ipv output by the renewable energy power generation device RE.

[0019] In the example of FIG. 1, the DC / DC converter 1 obtains Vpv from the voltage sensor 91V and obtains Ipv from the current sensor 92A (see also FIG. 2). The DC / DC converter 1 uses the obtained Vpv and Ipv to calculate: Ppv = Vpv × Ipv … (1) Ppv may be calculated as follows:

[0020] (Examples of Signal Values ​​in Power Conversion System 100) Fig. 3 shows an example of how each signal value changes over time in the power conversion system 100. In each graph in Fig. 3, the horizontal axis indicates time (t) and the vertical axis indicates the signal value. Reference numeral 310 in Fig. 3 shows an example of the change in Ppv over time.

[0021] Ppvmax in the reference numeral 310 indicates the maximum power point power of the renewable energy power generation device RE. As an example, in the power conversion system 100, Ppvmax may be determined by MPPT (Maximum Power Point Tracking) control. The MPPT control may be performed by the PCS 4. Ppvmax may also be expressed as an ideal value of the first DC power.

[0022] In the example of the first embodiment, Ppvmax is updated by executing MPPT control at predetermined time intervals. Therefore, until Ppvmax is updated, it has a constant value regardless of changes in environmental conditions (e.g., changes in the amount of solar radiation). In the example of Fig. 3, for the sake of simplicity, it is assumed that Ppvmax has a constant value over the entire time range.

[0023] Unlike Ppvmax, Ppv can change in real time in response to changes in environmental conditions. For example, if the amount of solar radiation decreases from the expected value, Ppv decreases with the decrease in the amount of solar radiation. In this case, Ppv becomes smaller than Ppvmax. In other words, the deviation between Ppvmax and Ppv becomes large.

[0024] Next, when the amount of solar radiation increases, Ppv increases with the increase in the amount of solar radiation. In other words, the difference between Ppvmax and Ppv becomes smaller. After that, when the amount of solar radiation recovers to the expected value, Ppv coincides with Ppvmax.

[0025] As described above, when a change in the amount of solar radiation occurs, a deviation may occur between Ppvmax and Ppv. Therefore, in the power conversion system 100, the DC / DC converter 1 outputs Pdd so as to compensate for the change in Ppv.

[0026] An example of the change in Pdd over time is shown at 320 in Fig. 3. As shown in Fig. 3, the DC / DC converter 1 may determine Pdd so as to compensate for the change in Ppv. For example, the DC / DC converter 1 may determine Pdd so as to maintain Ppcs at a constant value.

[0027] Therefore, the DC / DC converter 1 in the first embodiment calculates a differential power, which is the difference between the first DC power and the maximum power point power of the renewable energy power generation device. In this specification, the differential power is represented as Pi. In the first embodiment, the DC / DC converter 1 calculates a differential power between the first DC power and the maximum power point power of the renewable energy power generation device. In this specification, the differential power is represented as Pi. Pi = Ppv - Ppvmax … (2) Pi is calculated as follows. Pi may be used as an index value indicating the degree of deviation between Ppvmax and Ppv.

[0028] As is clear from the above description of Ppvmax and Ppv, Pi takes a 0 or a negative value. Reference numeral 320 shows an example of Pi calculated by the DC / DC converter 1. In the first embodiment, a case is illustrated in which the DC / DC converter 1 calculates Pi for each predetermined sampling period. Therefore, Pi in the example of reference numeral 320 is a signal whose value changes discretely for each sampling period.

[0029] The DC / DC converter 1 may determine Pdd based on Pi. For example, the DC / DC converter 1 may increase Pdd as Pi decreases. This allows Pdd to be increased when Ppv decreases. On the other hand, the DC / DC converter 1 may decrease Pdd as Pi increases. This allows Pdd to be decreased when Ppv increases.

[0030] Furthermore, when Pi=0, DC / DC converter 1 may set Pdd to 0. This is because when Ppv is equal to Ppvmax, there is no need to supply compensation power from DC / DC converter 1 to PCS 4.

[0031] In the figure 320, Pdd is shown as a smooth signal for the sake of clarity. However, the DC / DC converter 1 in the first embodiment actually calculates Pi and Pdd for each sampling period. Therefore, it should be noted that Pdd is actually a signal whose value changes discretely for each sampling period. This also applies to Pdd_c described below, and Ppcs and Ppcs_c described below.

[0032] Pdd_c at reference numeral 320 indicates an example of the second DC power supplied from the DC / DC converter 1 to the PCS 4 by the conventional method. An example of the processing of the conventional method will be described later. As indicated by reference numeral 320, according to a method according to an aspect of the present invention (hereinafter also referred to as the present method), a steady state in which the second DC power is maintained at 0 is reached earlier than in the conventional method. In other words, according to the present method, the responsiveness of the DC / DC converter 1 to changes in Ppv can be improved compared to the conventional method. An example of the processing of the present method will also be described later.

[0033] Also, as shown by reference numeral 320, according to the present method, the time during which the second DC power has a negative value is shorter than that of the conventional method. Therefore, according to the present method, unnecessary charging operation in the power storage device BT is less likely to occur than that of the conventional method. Also, according to the present method, unnecessary discharging operation in the power storage device BT is less likely to occur than that of the conventional method. The notations Pdd0 and Pdd1 in reference numeral 320 will be described later.

[0034] Reference numeral 330 in Fig. 3 shows an example of a change over time in Ppcs. Ppcs in reference numeral 330 corresponds to Pdd in reference numeral 320. In reference numeral 330, for reference, Ppv equivalent to the example of reference numeral 310 is represented by a dotted line. Furthermore, Ppcs_c in reference numeral 330 corresponds to Pdd_c in reference numeral 320. That is, Ppcs_c in reference numeral 330 represents the PCS input power generated when DC / DC converter 1 is operated by the conventional method in power conversion system 100.

[0035] As shown by reference numeral 330, the method of the present invention reaches a steady state in which the PCS input power is maintained at a constant value earlier than the conventional method. This also shows that the method of the present invention can improve the responsiveness of the DC / DC converter 1 to changes in Ppv compared to the conventional method.

[0036] Fig. 4 is a diagram for explaining the correspondence relationship between Ppvmax and Ppcs. Unlike the example of Fig. 3, Fig. 4 illustrates a case where Ppvmax changes over time. Reference numeral 410 illustrates an example of the waveforms of Ppvmax and Ppcs. Due to the change in Pdd described above, Ppcs changes so as to follow the change in Ppvmax.

[0037] Reference numeral 420 shows an enlarged view of region RG in reference numeral 410. The DC / DC converter 1 in the first embodiment updates Pdd so that the amount of change in Pdd per sampling period falls within a predetermined range (specifically, within ±Pm). Pm will be described later. Therefore, as shown by reference numeral 420, Ppcs also changes so that the amount of change per sampling period falls within a predetermined amount.

[0038] Therefore, the rate of change of Ppcs may be smaller than the rate of change of Ppvmax. For example, when Ppvmax decreases, Ppcs also decreases. However, due to the difference in the rate of change described above, the difference between Ppvmax and Ppcs becomes significant over time. On the other hand, when Ppvmax starts to increase, the difference between Ppvmax and Ppcs decreases over time. And when Ppvmax exceeds Ppcs, Ppcs starts to increase.

[0039] (Example of MPPT control in power conversion system 100) Fig. 5 shows an example of MPPT control in the power conversion system 100. Fig. 5 illustrates a case where MPPT control is performed by the PCS 4. Fig. 5 shows a PV (power-voltage) characteristic curve of the renewable energy power generation device RE. In the graph of Fig. 5, the horizontal axis indicates voltage (V) and the vertical axis indicates power (P). In this specification, the amount of change in P and the amount of change in V during one sampling period in MPPT control are denoted as ΔP and ΔV, respectively.

[0040] Fig. 5 illustrates an example in which the operating point on the PV characteristic curve moves from point A to point G by MPPT control. Point A in the example of Fig. 5 is the start point of tracking in MPPT control. On the other hand, point G is the maximum power point (i.e., the end point of tracking) determined as a result of tracking.

[0041] In Fig. 5, for example, a tracking path from point A to the next operating point, point B, is represented as path ab. Therefore, path fg represents a tracking path from point F to the next operating point G. Point F in the example of Fig. 5 is the operating point immediately before the end point.

[0042] In Fig. 5, for example, ΔP in path ab is expressed as ΔPab. In the example of Fig. 5, a constant power shift is used, which is a method of searching for the maximum power point by changing P by a constant value for each sampling period. Therefore, in the example of Fig. 5, ΔPab = ΔPbc = ΔPcd = ΔPde = ΔPef > 0. Thus, in the example of Fig. 5, P increases by a constant value with time from point A to point F.

[0043] On the other hand, in the example of Fig. 5, ΔPfg=0. In a constant power shift, when moving from one operating point to the next, if ΔP does not change, the next operating point is determined as the maximum power point. Therefore, in the example of Fig. 5, point G is determined as the maximum power point. Thus, in the example of Fig. 5, the value of P at point G is determined as Ppvmax.

[0044] Fig. 6 is a diagram for explaining a tracking method in MPPT control. Reference numeral 610 in Fig. 6 indicates an example of a constant power shift. As described above, in a constant power shift, ΔPab=ΔPbc=ΔPcd=ΔPde=ΔPef>0, while ΔPfg=0. Note that, as is clear from Fig. 5, in a constant power shift, ΔV is not necessarily constant.

[0045] Reference numeral 620 in FIG. 6 indicates an example of a constant voltage shift. The constant voltage shift is a method of searching for a maximum power point by changing V by a constant value for each sampling period. Therefore, in the constant voltage shift, ΔV is constant. In one aspect of the present invention, the point G, which is the maximum power point, may be determined by the constant voltage shift. In the constant voltage shift, when moving from one operating point to the next operating point, if ΔP does not change, the next operating point is determined as the maximum power point.

[0046] As shown by reference numeral 620, ΔP in the constant voltage shift is not necessarily constant. In the example of reference numeral 620, ΔPab>ΔPbc>ΔPcd>ΔPde>ΔPef>0. Reference numeral 620 illustrates a case where point G is determined as the maximum power point by the constant voltage shift. Therefore, in the example of reference numeral 620, ΔPfg=0.

[0047] (Example of processing in conventional methods) For comparison with the present method, an example of processing in a conventional method will be described. In the conventional method, a DC / DC converter: (Conditional expression A)Ppcs0>Ppv+Pm …(3) (Conditional expression B)Ppv>Ppcs0+Pm …(4) It is determined which of the following is satisfied. In equations (3) and (4), Ppcs0 represents Ppcs in the current sampling period.

[0048] Next, when conditional formula A is satisfied, the DC / DC converter satisfies the following formula (5): Pdd = Ppcs0 - Ppcs1 - Pm ... (5) Determine Pdd according to

[0049] On the other hand, when conditional formula B is satisfied, the DC / DC converter satisfies the following formula (6): Pdd = Ppcs0 - Ppcs1 + Pm ... (6) Determine Pdd according to

[0050] In formulas (5) and (6), Ppcs1 represents Ppcs in the previous sampling period. Also, Pm represents the upper limit of the amount of change in Pdd for each sampling period. As is clear from formulas (5) and (6), in the conventional method, Pdd changes by Pm or -Pm as a result of one sampling.

[0051] As described above, in the conventional method, according to conditional expressions A to B for Ppv, one of Expression (5) or Expression (6) is selected as the formula for determining Pdd. That is, in the conventional method, the formula for determining Pdd is switched according to Ppv. Therefore, for example, when the process of determining which of conditional expression A or conditional expression B is satisfied is not executed quickly, Pdd cannot quickly follow Ppv. Thus, in the conventional method, there is room for improvement in the responsiveness of the DC / DC converter.

[0052] (Example of the process in the present method) In the present method, the DC / DC converter 1 calculates Pi according to the above-described Expression (2). Next, the DC / DC converter 1 calculates Ts according to the following Expression (7), Ts = Pi / Pm …(7) and calculates Tp according to the following Expression (8), Tp = Pi / (Ppv0 - Ppv1) …(8) In Expression (8), Ppv0 represents Ppv in the current sampling period, and Ppv1 represents Ppv in the previous sampling period.

[0053] In this specification, Pdd in the current sampling period is denoted as Pdd0, and Pdd in the previous sampling period is denoted as Pdd1. The notations “Pdd0(K)” and “Pdd1(K)” at reference numeral 320 in FIG. 3 described above indicate Pdd0 and Pdd1 in the K-th sampling period, respectively. Similarly, the notations “Pdd0(L)” and “Pdd1(K)” indicate Pdd and Pdd1 in the L-th sampling period, respectively. K and L are arbitrary integers that satisfy K < L.

[0054] Ts given by Expression (7) is an index value corresponding to the time considered necessary to compensate for Pi when the change amount of Pdd for each sampling period is maintained at Pm. On the other hand, Tp given by Expression (8) is an index value corresponding to the time considered necessary to reach Pi when the change amount of the most recent Ppv is maintained.

[0055] Therefore, the DC / DC converter 1 may determine Pdd in the next sampling period based on the comparison result between Ts and Tp. For example, the DC / DC converter 1 (Conditional expression C) Ts > Tp …(9) may determine whether it is satisfied. Then, the DC / DC converter 1 may change the method for determining Pdd according to whether the conditional expression C is satisfied.

[0056] When the conditional expression C is satisfied, for example, the recovery of Ppv is rapid, and it is considered that appropriate power compensation for the PCS4 can be achieved without setting the change amount of Pdd for each sampling period to the maximum value Pm. Therefore, for example, when the conditional expression C is satisfied, the DC / DC converter 1 may determine the absolute value of the difference between Pdd and Pdd0 in the next sampling period to be a value smaller than Pm.

[0057] On the other hand, when the conditional expression C is not satisfied, for example, the recovery of Ppv is not so rapid, and it is considered preferable to set the change amount of Pdd for each sampling period to the maximum value Pm in order to perform appropriate power compensation for the PCS4. Therefore, for example, when the conditional expression C is not satisfied, the DC / DC converter 1 may determine the absolute value of the difference between Pdd and Pdd0 in the next sampling period to be a value equal to Pm.

[0058] FIG. 7 shows examples of Ts and Tp. In FIG. 7, the case where the Nth sampling and the Mth sampling are performed is illustrated. N and M are arbitrary integers satisfying N < M. In FIG. 7, for example, Ts and Tp in the Nth sampling period are denoted as Ts(N) and Tp(N), respectively. Also, Ppv0(N) - Ppv1(N) in the Nth sampling period is denoted as L(N).

[0059] In FIG. 7, the case where Ppv recovers and reaches Ppvmax, and then the steady state of Ppv is maintained is illustrated. In the example of FIG. 7, Ts(N)<Tp(N)であり、かつ、Ts(M)> Tp(M). In this way, whether or not conditional formula C is satisfied may differ depending on, for example, the change trend of Ppv (more specifically, the time rate of change of Ppv).

[0060] Unlike conventional methods, the present method allows Pdd to be flexibly set according to the change trend of Ppv. For example, when Ppv is expected to recover quickly, the present method allows the change amount of Pdd to be adjusted before Ppv increases.

[0061] As described above, the DC / DC converter 1 can provide a power conversion system 100 having a configuration different from the conventional one. Furthermore, the present technique can improve the responsiveness of the DC / DC converter compared to the conventional technique.

[0062] (One configuration example of the control unit 10) An example of the configuration of the control unit 10 in the DC / DC converter 1 will be described with reference to Fig. 2. The control unit 10 in the example of Fig. 2 is configured to be able to execute the method of the present invention. The control unit 10 may be communicably connected to the renewable energy power generation unit RE and the PCS 4 so as to be able to acquire various data from the renewable energy power generation unit RE and the PCS 4. The control unit 10 determines an output command value of the DC / DC converter 1 in the next sampling period with respect to the output value of the DC / DC converter 1 in the current sampling period.

[0063] In the following description, a case where the current sampling period is the Nth sampling period will be exemplified. Therefore, in the following description, the output value of DC / DC converter 1 in the current sampling period will be denoted as Pdd(N), and the output command value of DC / DC converter 1 in the next sampling period will be denoted as Pdd(N+1).

[0064] 2 includes a product calculation unit 11, addition and subtraction calculation units 12A-12E, delay elements 13A-13C, a power calculation unit 14, a time calculation unit 15, a selector 16, and an output unit 17. Below, the main operations of each unit of control unit 10 will be described. In this specification, addition and subtraction calculation units 12A-12E will be collectively referred to as addition and subtraction calculation unit 12, and delay elements 13A-13C will be collectively referred to as delay element 13.

[0065] The product calculation unit 11 obtains Vpv from the voltage sensor 91V and Ipv from the current sensor 92A. The product calculation unit 11 calculates Ppv according to the above-mentioned formula (1). The addition and subtraction calculation unit 12 performs a predetermined addition or subtraction calculation on the two signals input thereto, and outputs the calculation result. The delay element 13 holds the signal input thereto for one sampling period, and then outputs the signal. That is, the delay element 13 can delay a predetermined signal by one sampling period.

[0066] The power calculation unit 14 calculates each power as described above. For example, the power calculation unit 14 calculates Pi according to the above-mentioned formula (2). The time calculation unit 15 calculates each time as described above. For example, the time calculation unit 15 calculates Ts and Tp according to the above-mentioned formulas (7) to (8) based on the calculation results of the power calculation unit 14.

[0067] The selector 16 executes each selection process in the DC / DC converter 1. For example, the selector 16 determines whether or not the above-mentioned conditional formula C is satisfied for Ts and Tp calculated by the time calculation unit 15.

[0068] The output unit 17 determines its own output value Pdd(N+1) by performing a predetermined addition or subtraction operation on Pdd(N) based on the determination result of the selector 16. The output unit 17 outputs the determined Pdd(N+1) to the outside of the control unit 10 as an output command value of the DC / DC converter 1 in the next sampling period.

[0069] [Embodiment 2] The renewable energy power generation device RE according to an embodiment of the present invention may be any device capable of generating DC power from natural energy, and is not limited to a solar power generation device. For example, the renewable energy power generation device RE may be a wind power generation device. The output of the wind power generation device may vary depending on, for example, wind conditions. As will be clear to those skilled in the art, MPPT control is also applicable to wind power generation devices. Therefore, for example, the maximum power point power of the wind power generation device may be determined by the PCS4.

[0070] In addition, as is clear to those skilled in the art, the method of determining the maximum power point power in one aspect of the present invention is not limited to MPPT control. Therefore, the renewable energy power generation device RE according to one aspect of the present invention may be a device that can generate DC power and can determine the maximum power point power by any method.

[0071] [Software implementation example] The functions of the power conversion system 100 (hereinafter referred to as the "device" for convenience) can be realized by a program for causing a computer to function as the device, and a program for causing a computer to function as each control block of the device (particularly each part included in the control unit 10).

[0072] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program to realize each function described in each of the above embodiments.

[0073] The program may be non-transitory and may be recorded in one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be provided to the device via any wired or wireless transmission medium.

[0074] In addition, some or all of the functions of each of the control blocks can be realized by a logic circuit. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present invention. In addition, the functions of each of the control blocks can be realized by, for example, a quantum computer.

[0075] Furthermore, each process described in each of the above embodiments may be executed by AI (Artificial Intelligence). In this case, the AI ​​may be executed by the control device or another device (for example, an edge computer or a cloud server).

[0076] 〔summary〕 A power conversion system according to a first aspect of the present invention includes a DC / DC converter connected to a power storage device, and a PCS supplied with first DC power from a renewable energy power generation device, and the DC / DC converter converts the DC power supplied from the power storage device to output a second DC power to the PCS as compensation power for the first DC power, and determines the second DC power based on a differential power which is the difference between the first DC power and a maximum power point power of the renewable energy power generation device.

[0077] In a power conversion system according to a second aspect of the present invention, in the first aspect, when the differential power is represented as Pi, an upper limit value of the amount of change in the second DC power per sampling period of the DC / DC converter is represented as Pm, the first DC power in a current sampling period is represented as Ppv0, and the first DC power in a previous sampling period is represented as Ppv1, the DC / DC converter has the following: Ts=Pi / Pm Calculate Ts given as Tp = Pi / (Ppv0-Ppv1) T may be calculated as The second DC power in the next sampling period may be determined based on a result of comparing Ts with Tp.

[0078] In a power conversion system according to aspect 3 of the present invention, in aspect 2, the DC / DC converter may determine an absolute value of a difference between the second DC power in the next sampling period and the second DC power in the current sampling period to a value smaller than Pm when Ts>Tp.

[0079] In a power conversion system according to aspect 4 of the present invention, in aspect 2 or 3, the DC / DC converter may determine the absolute value of the difference between the second DC power in the next sampling period and the second DC power in the current sampling period to be equal to Pm when Ts>Tp is not satisfied.

[0080] In the power conversion system according to a fifth aspect of the present invention, in any one of the first to fourth aspects, the renewable energy power generation device may be a solar power generation device.

[0081] In the power conversion system according to a sixth aspect of the present invention, in any one of the first to fifth aspects, the PCS may determine the maximum power point power by MPPT control.

[0082] The power conversion system according to a seventh aspect of the present invention is any one of the first to sixth aspects, and may further include the power storage device and the renewable energy power generation device.

[0083] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0084] 1 DC / DC Converter 4 PCS 10 Control section 100 Power Conversion System ST power storage device RE Renewable energy power generation equipment (solar power generation equipment) PPV 1st DC power Ppvmax Maximum power point power Pdd 2nd DC power Pi differential power

Claims

1. A DC / DC converter connected to the power storage device; A PCS to which the first DC power is supplied from a renewable energy power generation device, The DC / DC converter is converting the DC power supplied from the power storage device to output a second DC power as a compensation power for the first DC power to the PCS; A power conversion system that determines the second DC power based on a differential power that is a difference between the first DC power and a maximum power point power of the renewable energy power generation device.

2. The differential power is represented as Pi, An upper limit value of a change amount of the second DC power per sampling period of the DC / DC converter is represented as Pm, The first DC power in the current sampling period is represented as Ppv0, When the first DC power in the previous sampling period is represented as Ppv1, The DC / DC converter is Ts = Pi / Pm Calculate Ts given as Tp=Pi / (Ppv0-Ppv1) Calculate Tp given as 2. The power conversion system according to claim 1, wherein the second DC power in the next sampling period is determined based on a result of comparing Ts with Tp.

3. 3. The power conversion system according to claim 2, wherein when Ts>Tp, the DC / DC converter determines an absolute value of a difference between the second DC power in the next sampling period and the second DC power in the current sampling period to be a value smaller than Pm.

4. 3. The power conversion system according to claim 2, wherein, when Ts>Tp is not satisfied, the DC / DC converter determines an absolute value of a difference between the second DC power in the next sampling period and the second DC power in the current sampling period to be equal to Pm.

5. The power conversion system according to claim 1 , wherein the renewable energy power generation device is a solar power generation device.

6. The power conversion system of claim 1 , wherein the PCS determines the maximum power point power by MPPT control.

7. The power conversion system according to claim 1 , further comprising the power storage device and the renewable energy power generation device.

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