JP6526421B2 - Power control system - Google Patents

Description

  The present invention relates to a power control system including a plurality of power converters.

  BACKGROUND ART In recent years, photovoltaic power generation systems that operate grid-connected with a commercial power system and store a part of generated power in a storage device are increasing. In this solar power generation system, the generated power of the solar cell string can be reversely flowed to the commercial power system and sold to the power supply provider. In addition, when the amount of power generation of the solar cell string decreases, the power supplied to the power load system can be purchased from the commercial power system or discharged from the power storage device. Furthermore, the power purchased from the commercial power system can be stored in the storage device.

  As an example of prior art related to the present invention, Patent Document 1 discloses a large-scale power conversion system in which a plurality of solar cell panels are connected to a plurality of power conditioners via a switch. . In this power conversion system, when the amount of power generation decreases in the morning and evening and cloudy weather, the power conditioner operates by connecting each solar cell panel to a smaller number of power conditioners by switching the switches. Power conversion efficiency is prevented.

  Further, Patent Document 2 discloses a photovoltaic power generation system in which a solar cell string including a solar cell and a secondary cell connected in parallel is controlled by one power conditioner. In this solar power generation system, smoothing of output power and time shift can be performed at low cost by controlling the output power value of the power conditioner based on the output of the power conditioner and the detection result of the state of the secondary battery. It has been realized.

Patent No. 5300404 gazette Patent No. 5028049

  However, when each solar cell panel is connected to a plurality of power conditioners as in Patent Document 1, a plurality of switches corresponding to the number of solar cell panels are required, which increases the cost in constructing the system. . Furthermore, since the electrical connection between the solar cell panel and the power conditioner is disconnected once at the time of switching of the switch, the power generation of the solar cell panel can not be used during the switching period and is wasted. Further, even after the switching, the power supplied to the power conditioner and converted into power gradually rises and increases, so the power generated by the solar cell panel available during this rising period decreases. Therefore, there is a problem that the power generation loss of the solar cell panel increases as the number of times of switching the switching device increases, and the generated power of each solar cell panel can not be effectively used. Patent Document 2 does not mention such a problem.

  An object of the present invention is to improve the utilization efficiency of generated power in a power control system provided with a plurality of power conversion units in view of the above-mentioned situation.

  In order to achieve the above object, a power control system according to one aspect of the present invention includes a power generation device and a storage device connected to a first current path, a second current path connected to a power source, and a first current path. , And a conversion control unit that controls the power conversion operation of the plurality of power conversion units, and the output end of the power generation device is connected in parallel with the input / output end of the power storage device Be configured.

  In the power control system described above, when the power conversion operation is performed in all the power conversion units, the total power value of the first output power output from all the power conversion units is power conversion in some of the power conversion units A determination unit that determines whether or not the total power value of the second output power output from the partial power conversion unit is lower than or equal to at least one of a front stage and a rear stage of each of the power conversion units; The switching control unit further includes: a connection switching unit connected in series; and an opening / closing control unit that controls the opening / closing operation of the connection opening / closing unit based on the determination result of the determination unit. If it is determined that the total power value of the two output powers is equal to or less, the open operation is performed to the connection switching unit connected to at least one of the front stage and the rear stage of the remaining partial power converters among all the power converters. It may be configured to

  In the above power control system, the connection switching unit may be connected in series to both the front stage and the rear stage of each power conversion unit.

  The above power control system may further include a bidirectional voltage conversion unit provided between the power storage device and the first current path, and the conversion control unit may be configured to further control the voltage conversion operation of the bidirectional voltage conversion unit. .

  The power control system described above is provided between the first current path and each power conversion unit, and converts a plurality of voltage values of power input from the first current path into a rated voltage value of the power conversion portion. The conversion control unit may be configured to further control the voltage conversion operation of the plurality of voltage conversion units.

  In the above power control system, the power conversion unit may be configured to be capable of bi-directional power conversion between the first current path and the second current path.

  The above-described power control system may be configured to further include a plurality of insulating transformers provided between each power converter and the second current path.

  According to the present invention, it is possible to improve the utilization efficiency of generated power in a power control system including a plurality of power conversion units.

It is a block diagram showing an example of composition of a solar energy power generation system concerning a 1st embodiment. It is a graph which shows an example of the fluctuation | variation characteristic of the power conversion efficiency with respect to a power ratio. It is a flowchart for demonstrating an example of the switch process of a switch unit. It is a block diagram showing an example of composition of a solar energy power generation system concerning a 2nd embodiment. It is a block diagram showing an example of composition of a solar energy power generation system concerning a 3rd embodiment. It is a block diagram showing an example of composition of a wind power generation system. It is a block diagram which shows the other structural example of a solar energy power generation system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment
FIG. 1 is a block diagram showing a configuration example of a photovoltaic power generation system 100 according to the first embodiment. The solar power generation system 100 is a power control system electrically connected to the commercial power grid CS and the power load grid LS via, for example, a single-phase three-wire conductive path, and includes two solar cell strings 1a and 1b and a storage device. Grid-connected operation by 2 and the commercial power system CS is possible. Further, in the solar power generation system 100, the generated power is converted from direct current to alternating current, and reverse flow (output) to the commercial power grid CS via the second current path P2 to sell the power to the power company It has become possible.

  Each of the solar cell strings 1a and 1b is a power generation apparatus including a plurality of solar cell modules connected in series, receives solar light to generate electric power, and generates generated DC power through the backflow prevention devices 11a and 11b. It outputs to the electric circuit P1. In the following, DC power output from the solar cell strings 1a and 1b to the first current path P1 is referred to as generated power. The backflow prevention devices 11a and 11b are formed of circuits including rectifying elements such as diodes, for example, and prevent the reverse current from flowing in the solar cell strings 1a and 1b.

  The solar cell strings 1a and 1b and the power storage device 2 are connected to one end of the first current path P1, as shown in FIG. Furthermore, the output ends of the solar cell strings 1a and 1b are connected in parallel to the input and output ends of the power storage device 2 via the backflow prevention devices 11a and 11b. Therefore, the power generation of the solar cell strings 1a and 1b is controlled such that the operating point voltage thereof becomes the same voltage value as the input / output voltage (for example, 340 to 400 [V]) of the power storage device 2. In addition, the number of solar cell strings 1a and 1b provided in the solar energy power generation system 100 is not limited to the illustration of FIG. 1, One may be sufficient and three or more may be sufficient. The solar cell strings 1a and 1b may be configured to include one solar cell module.

  Power storage device 2 can be repeatedly stored and discharged, can store at least a portion of the power flowing through first current path P1, and discharges DC power corresponding to the stored amount wa into first current path P1. You can also. In addition, below, the electric power which flows through the 1st electricity supply path P1, and its electric power value are represented by Wp1. In the following, DC power input from the first current path P1 to the storage device 2 during storage is referred to as storage power, and DC current output from the storage device 2 to the first current path P1 during discharge is referred to as It is called discharge power. The configuration of power storage device 2 is not particularly limited, and may include, for example, a secondary battery such as a lithium secondary battery, a nickel hydrogen battery, a nickel cadmium battery, and a lead battery, or an electric double layer capacitor It may be Further, the number of power storage devices 2 is not limited to the example of FIG. 1 and may be plural.

  The commercial power grid CS is an external power source connected to one end of the second current path P2 via the third current path P3. A power meter M is provided in the third current path P3. The power meter M is a power detection unit that detects the direction in which power flows in the third current path P3 and the power value thereof, and outputs a detection signal indicating the detection result to the charge / discharge controller 4 described later. For example, when power flows from the solar power generation system 100 to the commercial power grid CS in the third electric path P3, the power meter M is that the solar power generation system 100 is selling power to the commercial power grid CS, and Detect the amount of power sold. In the case where power flows from the commercial power grid CS to the photovoltaic power generation system 100 and / or the power load grid LS in the third power path P3, the power meter M measures the photovoltaic power generation system 100 from the commercial power grid CS. Detect purchasing and power consumption.

  The power load system LS is connected between one end of the second current path P2 and the third current path. The power load system LS is, for example, a load device such as an electric appliance in a home or a facility device of a factory, and consumes the power supplied from the second current path P2 and / or the third current path P3.

  Next, between the other end of the first current path P1 and the other end of the second current path P2, the first component group Sa, 3a, Ta, and Sb, and the second component Sc, 3b, Tb. , And Sd are connected in parallel. The switch unit Sa of the first component group, the power conditioner 3a, the insulating transformer Ta, and the switch unit Sb are sequentially connected in series. Further, the switch unit Sc of the second component group, the power conditioner 3b, the insulating transformer Tb, and the switch unit Sd are also connected in series in order. Hereinafter, the power conditioners 3a and 3b will be referred to as PCS (Power Conditioning System) 3a and 3b. Further, each configuration of the PCS 3a and the transformer Ta is similar to that of the PCS 3b and the transformer Tb, respectively. Therefore, the description of the PCS 3b and the transformer Tb may be omitted below.

The switch units Sa to Sd are connection open / close sections that open / close the electrical connection between the first current path P1 and the second current path P2 based on an open / close signal described later output from the charge / discharge controller 4. Switch unit Sa, Sb is Ru are respectively connected in series upstream and downstream of PCS3a. The switch unit Sa switches the ON state (closed: conduction) / OFF state (open: cut) of the electrical connection between the first current paths P1 and the PCS 3a. The switch unit Sb switches the ON state (closed: conduction) / OFF state (open: cut) of the electrical connection between the transformer Ta and the second current path P2. The switch unit Sc, Sd is Ru are respectively connected in series upstream and downstream of PCS3b. The switch unit Sc switches the ON state (closed: conductive) / OFF state (open: disconnected) of the electrical connection between the first current path P1 and the PCS 3b. Switch unit Sd is the transformer T b and the 2 ON state of the electrical connection between the electric path P2 (closed: conductive) / OFF state: switch the (open cut). The switch units Sa to Sd open and close the electrical connection in accordance with the operation state of each of the PCSs 3a and 3b (in particular, bidirectional inverters 31a and 31b described later), thereby making each of the PCSs 3a and 3b It can be disconnected and reconnected individually.

  The PCS 3a is a power converter having a bidirectional inverter 31a. In addition, the PCS 3a includes a first power detection unit (not shown) for detecting the transmission direction and power value of power input / output on the switch unit Sa side of the bidirectional inverter 31a, and the transformer Ta side of the bidirectional inverter 31a. And a second power detection unit (not shown) for detecting the transmission direction and the power value of the power input and output.

  The bidirectional inverter 31a is a non-insulated bidirectional power conversion unit controlled by the charge and discharge controller 4 and performs bidirectional power conversion by PWM (Pulse Width Modulation) control or PAM (Pulse Amplitude Modulation) control. be able to. For example, the bidirectional inverter 31a can AC / DC convert AC power input from the transformer Ta into DC power and output the DC power to the first current path P1 via the switch unit Sa. In addition, the bidirectional inverter 31a converts DC power input from the first current path P1 through the switch unit Sa into AC power of AC frequency according to the power standard of the commercial power grid CS and the power load grid LS. It can also be converted and output to the transformer Ta. In the following, the bi-directional inverter 31a converts the power input from the switch unit Sa side and outputs it to the transformer Ta side as the power conversion in the forward conversion direction a, and the power conversion in the forward conversion direction a It is called forward conversion. Further, that the bidirectional inverter 31a converts the power input from the transformer Ta side and outputs it to the switch unit Sa side is the power conversion in the reverse conversion direction b, and the power conversion in the reverse conversion direction b is the reverse conversion Call.

  Here, fluctuation characteristics of the power conversion efficiency Ea of the bidirectional inverter 31a will be described. The power conversion efficiency Ea (= Woa / Wia) of the output power value Woa with respect to the input power value Wia in the bidirectional inverter 31a is the power ratio Ra of the input power value Wia with respect to the rated power value VAa even in the same power conversion operation. It fluctuates according to (= Wia / VAa). In particular, when the power ratio Ra becomes very low or very high, the power conversion efficiency Ea decreases. Hereinafter, the power conversion efficiency Ea with respect to the power ratio Ra will be expressed as Ea (Ra). FIG. 2 is a graph showing an example of the fluctuation characteristic of the power conversion efficiency Ea (Ra) with respect to the power ratio Ra. FIG. 2 shows the power conversion efficiency Ea (Ra) in the reverse conversion direction b of the bidirectional inverter 31a.

  Even if the power conversion efficiency Ea (Ra) is the same reverse conversion operation as shown in FIG. 2, it starts to decrease when the power ratio Ra becomes less than the lower limit power ratio Ra1 (for example, 0.50), and the power ratio Ra decreases. Decrease rapidly according to the Then, when the power ratio Ra becomes equal to or less than the reactive power ratio Ra0 (for example, 0.05), the power ratio Ra becomes 0, and the power Woa output from the bidirectional inverter 31a by the inverse conversion becomes 0. Further, even if the power conversion efficiency Ea (Ra) exceeds the upper limit power ratio Ra2 (for example, 0.83), the power conversion efficiency Ea (Ra) is reduced according to the increase of the power ratio Ra even in the same reverse conversion operation. . The fluctuation characteristic of such power conversion efficiency Ea (Ra) is determined according to the specification of the bidirectional inverter 31a, the configuration of the internal circuit, and the like.

  Although the reactive power conversion rate Ra0, the lower limit power conversion rate Ra1, and the upper limit power conversion rate Ra2 in the bidirectional inverter 31b may differ, the fluctuation characteristic of the power conversion efficiency Eb of the bidirectional inverter 31b is the power conversion efficiency Ea. It is similar to the fluctuation characteristic of. Therefore, the description of the fluctuation characteristic of the bidirectional inverter 31b is omitted.

  Also, although the bidirectional inverter 31a is provided in parallel with the bidirectional inverter 31b, the distribution method of the power Wia, Wib respectively input from the first current path P1 or the second current path P2 to the bidirectional inverters 31a, 31b Is not particularly limited. Each input power Wia, Wib may be equally distributed, or may be distributed according to the ratio of the rated power values VAa, VAb of the bidirectional inverters 31a, 31b. This distribution can be variably set by control of the power conversion operation of each bidirectional inverter 31a, 31b.

  The insulating transformer Ta is an isolation transformer that generates and outputs power corresponding to the power input from one end at the other end. When the bidirectional inverter 31a performs forward conversion, the transformer Ta transforms AC power input from the second current path P2 via the switch unit Sb with a predetermined transformation ratio, and outputs the transformed power to the PCS 3a. When the bidirectional inverter 31a performs reverse conversion, the transformer Ta transforms the AC power output from the PCS 3a and outputs the AC power to the second current path P2 via the switch unit Sb. As described above, the transformer Ta prevents the power from flowing directly between the PCS 3a and the switch unit Sb, but indirectly electrically connects between the two.

  Next, the charge and discharge controller 4 will be described. The storage and discharge controller 4 is a power control device that performs power control of the solar power generation system 100, and includes a display unit 41, an input unit 42, a storage unit 43, and a control unit 44.

  The display unit 41 displays information on the solar power generation system 100 and the like on a display (not shown). The input unit 42 receives a user input, and outputs an input signal corresponding to the user input to the control unit 44.

  The storage unit 43 is a non-volatile storage medium which holds non-temporarily stored information without supplying power. The storage unit 43 stores control information, a program, and the like used in each component (particularly, the control unit 44) of the charge and discharge controller 4. In addition, storage unit 43 includes information on power storage device 2 (for example, storage capacity wc), information on switch units Sa to Sd, and information on PCSs 3a and 3b (for example, rated power values VAa and VAb of bidirectional inverters 31a and 31b, Also stored are rated voltage values, fluctuation characteristics of each power conversion efficiency Ea (Ra), Eb (Rb), and the like.

  The control unit 44 controls each component of the solar power generation system 100 using the control information, the program, and the like stored in the storage unit 43. The control unit 44 has a power monitoring unit 441, a power storage device monitoring unit 442, a conversion control unit 443, a determination unit 444, and an open / close control unit 445 as functional elements.

  The power monitoring unit 441 monitors the power flowing through the third current path P3. For example, based on the detection signal output from the power meter M, the power monitoring unit 441 detects the direction in which the power flows in the third current path P3, the power value thereof, and the like.

  The storage device monitoring unit 442 monitors the state of the storage device 2. For example, storage device monitoring unit 442 detects storage capacity wc of storage device 2, storage amount wa, and the like based on the status notification signal output from storage device 2.

  The conversion control unit 443 controls the bidirectional inverters 31a and 31b, and outputs a conversion control signal indicating control information such as the power conversion direction and the power conversion operation to the respective bidirectional inverters 31a and 31b. For example, conversion control unit 443 converts the power of each bidirectional inverter 31a, 31b based on the state of photovoltaic power generation system 100 (power sale / purchase, home power consumption, etc.), the state of power storage device 2, user input, etc. Take control. Furthermore, the conversion control unit 443 controls the power conversion control of the bidirectional inverters 31a and 31b based on the rated power values VAa and VAb of the bidirectional inverters 31 and the fluctuation characteristics of the power conversion efficiencies Ea (Ra) and Eb (Rb). Do it individually.

  The determination unit 444 is configured such that the total power value Wo1 of the first output power output from all the bidirectional inverters 31a and 31b is a part of both when the power conversion operation is performed by all the bidirectional inverters 31a and 31b. When the power conversion operation is performed by the direction inverter 31a, it is determined whether or not it is equal to or less than the total power value Wo2 of the second output power output from the part of the bidirectional inverters 31a. The total power value Wo1 of the first output power is output from the PCS 3a to the transformer Ta side and the PCS 3b to the transformer Tb side when the bidirectional inverters 31a and 31b respectively perform reverse conversion. Sum with the value of the Further, the total power value Wo1 of the first output power is output from the PCS 3a to the switch unit Sa side and from the PCS 3b to the switch unit Sc side when the bidirectional inverters 31a and 31b perform forward conversion, respectively. Sum with the value of the

  The open / close control unit 445 controls the switch units Sa to Sd. For example, the open / close control unit 445 outputs an open / close signal that instructs the switch units Sa to Sd to perform the opening operation or the closing operation based on the determination result of the determination unit 444. In response to the open / close signal, each of the switch units Sa to Sd disconnects or reconnects the electrical connection. When the switch units Sa and Sb are caused to open, the bidirectional inverter 31a (and the PCS 3a) can be electrically disconnected from the photovoltaic system 100 to cut off the power supply from the photovoltaic system 100 to the PCS 3a. When the switch units Sc and Sd are opened, the bidirectional inverter 31b (and the PCS 3b) may be electrically disconnected from the photovoltaic system 100 to cut off the power supply from the photovoltaic system 100 to the PCS 3b. it can.

  If such opening and closing control is performed, it is not necessary to provide a switch for selecting each of the solar cell strings 1a and 1b for selecting the PCS 3a and 3b connecting the respective solar cell strings 1a and 1b. The cost of building can be reduced. This effect is more pronounced as the number of solar cell strings 1a and 1b increases.

  In addition, unlike the above-mentioned opening / closing control, when the electrical connection is disconnected by only one of the switch units Sc and Sd, whether or not the power supply to the PCS 3b can be disconnected depends on the configuration of the electric circuit inside the PCS 3b. Depends on On the other hand, in the case of disconnecting the electrical connection in both of the switch units Sc and Sd as in the opening / closing control described above, the power supply from the photovoltaic system 100 to the PCS 3b is not performed regardless of the configuration of the electric circuit inside the PCS 3b. It can be cut off. Therefore, it is possible to prevent power consumption (for example, consumption of standby power at the time of shutdown) in the PCS 3 b, and to improve the overall utilization efficiency of the generated power viewed from the entire photovoltaic power generation system 100.

  In the photovoltaic power generation system 100 described above, the output ends of the solar cell strings 1 a and 1 b are connected in parallel to the input / output end of the power storage device 2. Therefore, depending on the connection state of each PCS 3a, 3b, the power conversion operation of the bidirectional inverters 31a, 31b, etc., the generated power of the solar cell strings 1a, 1b can not be used or the available power can be reduced. There is no Therefore, the utilization efficiency of the generated power of the solar cell strings 1a and 1b in the solar power generation system 100 including the plurality of bidirectional inverters 31a and 31b can be improved.

  For example, when at least one of each PCS 3a, 3b is disconnected from the photovoltaic power generation system 100, when the power conversion direction of the bidirectional inverters 31a, 31b is switched, and each input on the DC power side of the bidirectional inverters 31a, 31b. Consider the case where the power Wia and Wib decrease rapidly. Even in these cases, since the solar cell strings 1a and 1b are always connected to the power storage device 2, surplus power not input to each of the PCSs 3a and 3b is stored in the power storage device 2. Although this surplus power fluctuates greatly, it is possible to prevent fluctuation of the power flowing through the first current path P1 due to the storage and discharge of the power storage device 2. Therefore, it is possible to prevent the reduction of the available generated power of the solar cell strings 1a and 1b.

  Also, consider the case where at least one of the PCSs 3a and 3b is reconnected. Even in this case, of the generated power of the solar cell strings 1a and 1b, surplus power of the amount corresponding to the rise of each input power Wia and Wib of the bidirectional inverters 31a and 31b or each output power Woa and Wob Because the electricity is stored, it is not necessary to reduce the amount of power generation.

  Next, switching processing of the switch units Sa to Sd will be described. FIG. 3 is a flowchart illustrating an example of the switching process of the switch units Sa to Sd. In the process of FIG. 3, both of the bidirectional inverters 31a and 31b are set in the reverse conversion direction b. Further, the power conversion capability of the PCS 3a (bidirectional inverter 31a) is superior to that of the PCS 3b (bidirectional inverter 31b). Therefore, at the time of reverse conversion, power is preferentially supplied to the PCS 3a.

  First, the power ratio Ra of the bidirectional inverter 31a is calculated (S101), and it is determined whether the power ratio Ra is less than or equal to the lower limit threshold Rsa (S102). The lower limit threshold Rsa is used to determine whether the operation rate of the PCS 3a is close to zero. The lower limit threshold Rsa is set to, for example, not less than the reactive power ratio Ra0 and less than the lower limit power ratio Rs1 when the power conversion efficiency Ea (Ra) of the bidirectional inverter 31a is zero. In particular, the lower limit threshold Rsa may be set to the reactive power ratio Ra0. In this way, it can be accurately determined that the power conversion efficiency Ea (Ra0) in the reverse conversion direction b of the bidirectional inverter 31a becomes zero.

  When it is determined that Ra ≦ Rsa (YES in S102), the power conversion efficiency Ea (Ra) of the bidirectional inverter 31a is very low, and the PCS 3a is not almost operating. Also, in this case, the PCS 3b is also not operating at all. Therefore, the switch units Sa to Sd are switched to the OFF state (S103). By this process, the bidirectional inverters 31a and 31b (PCSs 3a and 3b) are electrically disconnected from the photovoltaic power generation system 100. Therefore, the power consumption of the PCSs 3a and 3b can be omitted. At this time, since the photovoltaic power generation system 100 can not convert power in the reverse conversion direction b, reverse power flow (selling) to the commercial power grid CS or self-consumption of power in the power load grid LS can not be performed. Therefore, the power generated by the solar cell strings 1 a and 1 b is stored in the storage device 2. Thereafter, when the switch units Sa and Sb are switched ON (YES in S104), power is supplied to the PCS 3a, and reverse conversion of the bidirectional inverter 31a is resumed. Note that the means by which the switch units Sa and Sb are switched ON in S104 is not particularly limited. The switch units Sa and Sb may be switched manually by the user, for example, or automatically when the power value Wp1 of the first current path P1 is equal to or higher than the power value (Rsa · VAa) corresponding to the lower threshold Rsa described above. It may be switched to Then, the process returns to S101.

When it is not determined that Ra ≦ Rsa (NO in S102), the power conversion efficiency Ea (Ra) of the bidirectional inverter 31a is not very low. In this case, it is determined whether or not the switch units Sc and Sd are ON (S105). When it is determined that it is ON (in the case of YES in S105), both of the bidirectional inverters 31a, 31b are electrically connected to the photovoltaic power generation system 100. Therefore, the power ratio Rb of the bidirectional inverter 31b is calculated (S106), and it is determined whether the PCSs 3a and 3b satisfy the condition of the following formula 1 (S107).
{VAa, Ra, Ea (Ra) + VAb, Rb, Eb (Rb)}
≦ {VAa · Ra + VAb · Rb} · Ea (Ra + Rb · VAb / VAa)
(Equation 1)

  That is, in S107, it is determined whether the first output power value Wo1 is less than or equal to the second output power value Wo2. Here, the first output power value Wo1 is a total power value of the first output power output from each bidirectional inverter 31a, 31b when the reverse conversion operation is performed in all the bidirectional inverters 31a, 31b, It is the value (Woa + Wob) of the electric power actually output from each bidirectional | two-way inverter 31a, 31b in the present time. The second output power value Wo2 is the total power value of the second output power output from the bidirectional inverter 31a when the reverse conversion operation is performed by only one bidirectional inverter 31a, and at this time, the bidirectional inverter is This is a virtual power value output only from 31a.

  When it is determined that Formula 1 is satisfied (YES in S107), the first output power value Wo1 is equal to or less than the second output power value Wo2. Here, if Wo1 = Wo2, the reverse conversion operation is performed with only one of the bidirectional inverters 31a, and the power consumption in the PCS 3b can be saved if the PCS 3b is separated from the photovoltaic power generation system 100. In addition, if Wo1 <Wo2, the PCSs 3a and 3b to the second perform the reverse conversion operation in the case of performing the reverse conversion operation with only one of the bidirectional inverters 31a than when performing the reverse conversion operation with all the bidirectional inverters 31a and 31b. The power output to the conduction path P2 becomes high. That is, the overall power conversion efficiency of the reverse conversion viewed from the entire photovoltaic power generation system 100 is high. Therefore, the switch units Sa and Sb are turned on, but the switch units Sc and Sd are switched to the off state (S108). By this process, the electrical connection of the bidirectional inverter 31 a (PCS 3 a) to the photovoltaic system 100 is maintained, but the bidirectional inverter 31 b (PCS 3 b) is electrically disconnected from the photovoltaic system 100. Therefore, the power consumption of the PCS 3b can be omitted. Then, the process returns to S101.

  When it is not determined that the formula 1 is satisfied (NO in S107), the first output power value Wo1 becomes larger than the second output power value Wo2. Therefore, if the current power conversion operation (when the reverse conversion operation is performed by all the bidirectional inverters 31a and 31b) is continued, the PCS 3a, when the reverse conversion operation is performed by only one of the bidirectional inverters 31a, The power output from 3b to the second current path P2 is high. That is, the overall power conversion efficiency of the reverse conversion viewed from the entire photovoltaic power generation system 100 is high. Therefore, the switch units Sa to Sd are turned on (S109). By this process, the electrical connection of the bidirectional inverters 31a and 31b (PCSs 3a and 3b) to the photovoltaic power generation system 100 is maintained. Then, the process returns to S101.

Next, when S105 is NO (when it is not determined that the switch units Sc and Sd are ON), the bidirectional inverter 31a is electrically connected to the photovoltaic power generation system 100, but the bidirectional inverter 31b is Are electrically disconnected from the photovoltaic system 100. In this case, assuming that both the PCS 3a and 3b are electrically connected to the photovoltaic power generation system 100, it is determined whether the PCS 3a and 3b satisfy the condition of the following formula 2 (S110) ).
{Rm · Ea (Rm) + (Ra−Rm) · Eb ((Ra−Rm) · VAa / VAb)}
≦ Ra · Ea (Ra) (Equation 2)

  That is, in S110, it is determined whether the first output power value Wo1 is less than or equal to the second output power value Wo2. Here, the first output power value Wo1 is a total power value of the first output power output from each bidirectional inverter 31a, 31b when the reverse conversion operation is performed in all the bidirectional inverters 31a, 31b, At this moment, it is a value of virtual power output from each bidirectional inverter 31a, 31b. Further, the second output power value Wo2 is a total power value of the second output power output from the bidirectional inverter 31a when the reverse conversion operation is performed by only one bidirectional inverter 31a, and both of them are actually both at this time It is the value Woa of the electric power output from the direction inverter 31a.

  In Equation 2, the power ratio Rm is a value of the power ratio Ra of the bidirectional inverter 31a set when the switch units Sc and Sd are switched to the ON state to virtually operate the PCS 3b. The power ratio Rm is, for example, equal to or higher than the lower limit power ratio Ra1 at which the decrease of the power conversion efficiency Ea (Ra) is started according to the decrease of the power ratio Ra, and the power conversion efficiency Ea (Ra Is set to a value within the range not exceeding the upper limit power ratio Ra2 at which the decrease of.

  When it is determined that Formula 2 is satisfied (YES in S110), the first output power value Wo1 is equal to or less than the second output power value Wo2. Here, if Wo1 = Wo2, it is not necessary to cause all the bidirectional inverters 31a and 31b to perform the reverse conversion operation. Furthermore, power conversion in the PCS 3b can be saved if the reverse conversion operation is performed by only one bidirectional inverter 31a and the other PCS 3b is separated from the photovoltaic power generation system 100. Further, if Wo1 <Wo2, the case where the current power conversion operation (in the case where the reverse conversion operation is performed by only one bidirectional inverter 31a) is continued performs the reverse conversion operation in all the bidirectional inverters 31a and 31b Rather, the power output from the PCSs 3a and 3b to the second current path P2 is higher. That is, the overall power conversion efficiency of the reverse conversion viewed from the entire photovoltaic power generation system 100 is high. Therefore, the switch units Sa and Sb are turned on, and the switch units Sc and Sd are turned off (S108). By this process, the electrical connection of the bidirectional inverter 31a (PCS 3a) to the photovoltaic power generation system 100 is maintained. Furthermore, a state in which the bidirectional inverter 31 b (PCS 3 b) is electrically disconnected from the photovoltaic power generation system 100 is also maintained. Then, the process returns to S101.

  When it is not determined that the formula 2 is satisfied (NO in S110), the first output power value Wo1 becomes larger than the second output power value Wo2. Therefore, the electric power outputted from the PCS 3a, 3b to the second conduction path P2 in the reverse conversion operation in all the bidirectional inverters 31a, 31b is more than in the reverse conversion operation with only one bidirectional inverter 31a. Will be higher. That is, the overall power conversion efficiency of the reverse conversion viewed from the entire photovoltaic power generation system 100 is high. Therefore, the switch units Sa and Sb are turned on, and the switch units Sc and Sd are also switched on (S109). By this process, the electrical connection of bidirectional inverter 31 a (PCS 3 a) to photovoltaic power generation system 100 is maintained, and bidirectional inverter 31 b (PCS 3 b) is electrically reconnected to photovoltaic power generation system 100. Ru. Then, the process returns to S101.

  As described above, according to the present embodiment, the power control system 100 includes the power generation devices 1a and 1b and the power storage device 2 connected to the first current path P1, and the second current path P2 and the first current path connected to the power source CS. A plurality of power conversion units 31a and 31b connected in parallel with the current path P1, and a conversion control unit 443 for controlling the power conversion operation of the plurality of power conversion units 31a and 31b; The output end of 1 b is connected in parallel to the input / output end of power storage device 2.

  According to this configuration, the electrical connection between the power generation devices 1a and 1b and the storage device 2 is not caused by changes in the operating state of the power conversion units 31a and 31b (for example, switching of power conversion direction, increase or decrease of power conversion amount, etc.) Is maintained. Therefore, in any of the power conversion units 31a and 31b, for example, electrical separation from the solar power generation system 100, switching of the power conversion direction, or power conversion amount in the reverse conversion direction b (or input power value Even if changes such as Wia and Wib) occur, surplus power generated at that time can be stored in the storage device 2. Therefore, the power generated by the power generation devices 1a and 1b can be supplied to the power conversion units 31a and 31b and / or the power storage device 2 without waste. Therefore, the utilization efficiency of the generated power in the power control system 100 including the plurality of power conversion units 31a and 31b can be improved.

  Further, in the power control system 100 described above, when the power conversion operation is performed in all the power conversion units 31a and 31b, the total power value Wo1 of the first output power output from all the power conversion units 31a and 31b is A determination unit 444 that determines whether or not the total power value Wo2 of the second output power output from the partial power conversion unit 31a is lower than or equal to the total power value Wo2 of the second output power output from the partial power conversion unit 31a. And opening / closing control units for controlling the opening / closing operations of the connection switching units Sa to Sd based on the determination results of the connection switching units Sa to Sd connected in series to the front stage and the rear stage of the power conversion units 31a and 31b and the determination unit 444 And the open / close control unit 445 determines that the total power value Wo1 of the first output power is equal to or less than the total power value Wo2 of the second output power. Our house Rino connecting opening portion Sc preceding and connected downstream to at least one of a portion of the power conversion unit 31b, is configured to cause the opening operation to Sd.

  According to this configuration, the total power value Wo1 of the first output power in the case where the power conversion operation is performed in all the power conversion units 31a and 31b is in the case where the power conversion operation is performed in some of the power conversion units 31a. When it is determined that the total power value Wo2 of the second output power is equal to or less than the remaining part of the power conversion unit 31b can be disconnected from the power control system 100 and the power supply can be cut off. Therefore, power consumption (for example, consumption of standby power at the time of stop) of the remaining part of the power conversion unit 31b can be prevented to improve the overall utilization efficiency of the generated power as viewed from the entire power control system 100. it can.

  Further, in the power control system 100 described above, the connection switching units Sa to Sd are connected in series to both the front stage and the rear stage of each of the power conversion units 31a and 31b. According to this configuration, the power conversion units 31a and 31b can be electrically disconnected from the power control system 100. Therefore, power supply from the power control system 100 to the power conversion units 31a and 31b can be cut off regardless of the configuration of the electric circuits in the power conversion units 31a and 31b.

  In the above power control system 100, the power conversion units 31a and 31b are configured to be capable of bi-directional power conversion between the first current path P1 and the second current path P2. According to this configuration, a part of the generated power and / or the discharged power of the storage device 2 can be converted and output from the first current path P1 to the second current path P2. Furthermore, the electric power supplied from the electric power source can be converted into electric power and output from the second electric path P2 to the first electric path P1 to be stored in the power storage device 2.

  The power control system 100 further includes a plurality of insulating transformers Ta and Tb provided between the power conversion units 31a and 31b and the second current path P2, respectively. According to this configuration, by providing the insulating transformers Ta and Tb between the power conversion units 31a and 31b and the second conduction path P2, power does not flow directly between the two, but there is no problem between the two. Electrical connection can be maintained indirectly.

Second Embodiment
Next, a second embodiment will be described. In the second embodiment, the bi-directional DC / DC converter 21 is provided at the front stage of the power storage device 2. Other than this, the second embodiment is the same as the first embodiment. Below, the structure different from 1st Embodiment is demonstrated. The same components as those in the first embodiment may be denoted by the same reference numerals, and the description thereof may be omitted.

  FIG. 4 is a block diagram showing a configuration example of a photovoltaic power generation system 100 according to the second embodiment. As shown in FIG. 4, one side of the bi-directional DC / DC converter 21 is connected to the storage device 2 and the other side is connected to one end of the first current path P1. The output ends of the solar cell strings 1a and 1b are connected in parallel to the input / output end of the DC / DC converter 21 on the first electric path P1 side via the backflow prevention devices 11a and 11b.

  Bidirectional DC / DC converter 21 is a bidirectional voltage conversion unit controlled by conversion control unit 443, and controls the storage and discharge of power storage device 2 based on the control signal output from storage and discharge controller 4. Bidirectional DC / DC converter 21 supplies at least a part of the current flowing through first electric path P1 to storage device 2 as storage power, or causes storage device 2 to output discharge power to first electric path P1. .

  According to the configuration of FIG. 4, by controlling the power conversion direction of bi-directional DC / DC converter 21, storage / discharge of power storage device 2 can be switched. Therefore, the timing for storing the generated power and the timing for discharging the storage device 2 can be set more freely, so the power control of the solar power generation system 100 can be performed more precisely.

  Further, the power generation of the solar cell strings 1a and 1b is controlled such that the operating point voltage thereof becomes equal to the potential on the first conduction path P1 side of the bidirectional DC / DC converter 21. Therefore, since the operating point voltage of the solar cell strings 1a and 1b can be controlled to a value different from the input / output voltage of the storage device 2, the storage device 2 of various specifications can be connected to the solar power generation system 100. Further, by controlling the power conversion operation of bi-directional DC / DC converter 21, it is possible to control the operating point voltage of solar cell strings 1a and 1b such as maximum power point tracking (MPPT) control, for example. Therefore, it is possible to improve or improve the utilization efficiency of the generated power by suppressing or preventing a decrease in the generated power of the solar cell strings 1a and 1b.

  As described above, according to the present embodiment, the power control system 100 further includes the bidirectional voltage conversion unit 21 provided between the power storage device 2 and the first conduction path P1 and the power generation devices 1a and 1b. Are configured to further control the voltage conversion operation of the bidirectional voltage conversion unit 21.

  According to this configuration, switching of storage / discharge of the power storage device 2 can be set more freely by the bidirectional voltage conversion unit 21, and therefore power control of the power control system 100 can be performed more precisely. Furthermore, the output voltage of the power generation devices 1a and 1b can be controlled by the bidirectional voltage conversion unit 21.

Third Embodiment
Next, a third embodiment will be described. In the third embodiment, a bidirectional DC / DC converter 32a is provided between the first current path P1 and the bidirectional inverter 31a in the PCS 3a. Further, in the PCS 3 b, a bidirectional DC / DC converter 32 b is provided between the first current path P 1 and the bidirectional inverter 31 b. Except for these, the second embodiment is the same as the first embodiment. Below, the structure different from 1st Embodiment is demonstrated. The same components as those in the first embodiment may be denoted by the same reference numerals, and the description thereof may be omitted.

  FIG. 5 is a block diagram showing a configuration example of a solar power generation system 100 according to the third embodiment. As shown in FIG. 5, the PCS 3a further includes a bidirectional DC / DC converter 32a, and the PCS 3b further includes a bidirectional DC / DC converter 32b. The configuration of the bi-directional DC / DC converter 32b is the same as that of the bi-directional DC / DC converter 32a, and thus the description thereof will be omitted below.

  The bidirectional DC / DC converter 32a is a bidirectional voltage conversion unit controlled by the conversion control unit 443 and performs DC / DC conversion of electric power between the first current path P1 and the bidirectional inverter 31a. The power conversion direction and power conversion operation of the bidirectional DC / DC converter 32 a are set based on the control signal output from the charge and discharge controller 4. For example, when performing power conversion operation in the forward conversion direction a, bidirectional DC / DC converter 32a converts the DC power output from bidirectional inverter 31a into DC power having the same voltage value as the input / output voltage of power storage device 2. And output to the first current path P1. In addition, when performing the power conversion operation in the reverse conversion direction b, the bidirectional DC / DC converter 32a converts the voltage value of DC power input from the first current path P1 into the rated voltage value of the bidirectional inverter 31a. , And output to the bidirectional inverter 31a.

  According to the configuration of FIG. 5, even if the voltage value of the DC power Wp1 flowing through the first current path P1 is different from the rated voltage value of the bidirectional inverter 31a, by transforming with the bidirectional DC / DC converter 32a, Both can be electrically connected. Therefore, the PCS 3a can transform the output power Woa of the bidirectional inverter 31a to the same voltage value as the DC power Wp1 in the case of the forward conversion direction a and output it to the first conduction path P1. Can transform the voltage value of the DC power Wp1 to the rated voltage value and input it to the bidirectional inverter 31a. Therefore, even if the specifications of the solar cell strings 1a and 1b and the storage device 2 are different from the specifications of the PCS 3a (particularly, the bidirectional inverter 31a), both can be connected.

  As described above, according to the present embodiment, the power control system 100 is provided between the first current path P1 and the power conversion units 31a and 31b, and converts the voltage value of the power input from the first current path P1 into power. The plurality of voltage conversion units 32a and 32b that perform voltage conversion to rated voltage values of the units 31a and 31b are further provided, and the conversion control unit 443 is configured to further control the voltage conversion operation of the plurality of voltage conversion units 32a and 32b.

  According to this configuration, it is possible to transform the voltage value of each input power Wia and Wib of the power conversion units 31a and 31b into the rated voltage value by the voltage conversion units 32a and 32b. Therefore, even if the specifications of the power generation devices 1a and 1b and the power storage device 2 are different from the specifications of the power conversion units 31a and 31b, both can be connected.

  The embodiments of the present invention have been described above. It is to be understood by those skilled in the art that the above-described embodiment is an exemplification, and that various modifications can be made to the respective constituent elements and combinations of the respective processes, and they are within the scope of the present invention.

  For example, in the first to third embodiments described above, the solar cell strings 1a and 1b are used for the power generation device, but the present invention is not limited to this example. At least a part of the power generation device may be a power generation device that performs power generation using renewable energy other than solar light (natural energy generation such as wind power, water power, geothermal energy, biomass, solar heat, waste power generation, etc.). For example, as shown in FIG. 6, the wind power generation system 100 may use the wind power generation devices 1a and 1b as the power generation device. In this case, the wind power generators 1a and 1b are connected to the first current path P1 via the AD / DC converters 12a and 12b.

  Moreover, although the alternating current power source like commercial power grid CS is connected to the solar energy power generation system 100 in the above-mentioned 1st-3rd embodiment, this invention is not limited to this illustration. Instead of the commercial power grid CS, a DC power source may be connected to the solar power generation system 100. In this case, each of the PCSs 3a and 3b is configured to have a DC / DC converter or a bidirectional DC / DC converter instead of the bidirectional inverters 31a and 31b.

  In the first to third embodiments described above, series circuits connected in parallel between the first current path P1 and the second current path P2 (for example, the first component group Sa, 3a, Ta, Sb, and Although the number of two components Sc, 3b, Tb, Sd) is two, the present invention is not limited to this example. The number of the series circuits may be three or more. Furthermore, when the number of series circuits connected in parallel is three or more, switching of disconnection / reconnection of the series circuit to the photovoltaic power generation system 100 may be controlled by collectively setting a plurality of series circuits. FIG. 7 is a block diagram showing another configuration example of the solar power generation system 100. As shown in FIG. In FIG. 7, four series circuits are connected in parallel between the other end of the first conduction path P1 and the other end of the second conduction path P2. Specifically, the first component group Sa, 3a, Ta, and Sb, the second component Sc, 3b, Tb, and Sd, and the third component group Se, 3c, Tc, and Sf, The fourth components Sg, 3d, Td, and Sh are connected in parallel. In FIG. 7, for example, switching control of disconnection / reconnection of the third and fourth components with respect to the solar power generation system 100 may be performed collectively. That is, when the third and fourth components are separated from the photovoltaic power generation system 100, the switch units Se to Sh may be collectively switched to the OFF state (opening operation). Furthermore, when the third and fourth components are reconnected to the solar power generation system 100, the switch units Se to Sh may be collectively switched to the ON state (closing operation). Alternatively, switching control of disconnection / reconnection of the second to fourth components to the photovoltaic power generation system 100 may be performed collectively. That is, when the second to fourth components are separated from the solar power generation system 100, the switch units Sc to Sh may be collectively switched to the OFF state (opening operation). Furthermore, when the second to fourth components are reconnected to the solar power generation system 100, the switch units Sc to Sh may be collectively switched to the ON state (closing operation).

  Further, in the first to third embodiments described above, connection switching units (switch units Sa to Sd) are respectively provided on both the front and rear stages of the bidirectional inverters 31a and 31b, but the present invention is not limited to this example. It is not limited. The connection switching unit may be connected in series to at least one of the front stage and the rear stage of the bidirectional inverters 31a and 31b. In this case, the connection switching unit is connected to a position where the power supply can be cut off depending on the configuration of the electric circuit inside the bidirectional inverters 31a and 31b (and the PCSs 3a and 3b). In this way, the bidirectional inverters 31a and 31b are disconnected from the photovoltaic power generation system 100 by the opening operation of the connection switching units Sa to Sd connected to at least one of the former stage and the latter stage, and the power supply is cut off. Therefore, the power consumption (for example, consumption of standby power at the time of stop) of the bidirectional inverters 31a and 31b separated from the photovoltaic power generation system 100 is prevented, and an overall generation power as viewed from the photovoltaic power generation system 100 as a whole. Utilization efficiency can be improved.

  Moreover, in the above-mentioned 1st-3rd embodiment, although bidirectional | two-way inverter 31a, 31b is non-insulation type, this invention is not limited to this illustration. At least a part of the bidirectional inverters 31a and 31b may be an insulating type. In this case, the configuration in which the insulating transformers Ta and Tb are connected in series can be omitted.

  In the first to third embodiments described above, the switch unit Sa is connected to the front stage of the PCS 3a and the insulating transformer Ta and the switch unit Sb are connected to the rear stage, but the present invention is limited to this example. I will not. The PCS 3a may include at least one of the switch units Sa and Sb and the insulating transformer Ta. For example, if the PCS 3a is an insulated PCS including a transformer Ta, the transformer Ta may not be provided. The other PCS 3b may also include at least one of the switch units Sc and Sd and the insulating transformer Tb. For example, if the PCS 3 b is an insulation type PCS that includes a transformer Tb, the transformer Tb may not be provided.

  In the first to third embodiments described above, at least a part or all of the functional components of the control unit 44 are realized by physical components (for example, an electric circuit, an element, a device, etc.) It may be

  Moreover, in the above-mentioned 1st-3rd embodiment, although PCS3a, 3b has bidirectional | two-way inverter 31a, 31b, this invention is not limited to this illustration. When the power supplied from the power source exemplified in the commercial power grid CS is not stored in the storage device 2, at least a part of each of the PCSs 3a and 3b converts an inverter (power conversion unit) that converts power in the reverse conversion direction b. You may have. In the third embodiment, the PCSs 3a and 3b include the bidirectional DC / DC converters 32a and 32b, but the present invention is not limited to this example. When each of the PCSs 3a and 3b includes an inverter that performs power conversion in the reverse conversion direction b, a DC / DC converter (voltage conversion unit) that performs voltage conversion in the reverse conversion direction b instead of the bidirectional DC / DC converters 32a and 32b. May be provided.

100 solar power generation system, wind power generation system 1a, 1b solar battery string, wind power generation device 11a, 11b backflow prevention device 12a, 12b AD / DC converter 2 storage device 21 bidirectional DC / DC converter 3a, 3b power conditioner (PCS )
31a, 31b Bidirectional Inverters 32a, 32b Bidirectional DC / DC Converter 4 Storage / Discharge Controller 41 Display Unit 42 Input Unit 43 Storage Unit 44 Control Unit 441 Power Monitoring Unit 442 Power Storage Device Monitoring Unit 443 Conversion Control Unit 444 Determination Unit 445 Switching Control Section Sa to Sd Switch unit Ta, Tb Transformer P1 to P3 1st to 3rd current path M watt hour meter CS commercial power grid LS power load grid

Claims (5)

A power generation device and a power storage device connected to the first current path;
A plurality of power conversion units connected in parallel between a second conduction path connected to an electric power source and the first conduction path;
A conversion control unit that controls power conversion operations of the plurality of power conversion units;
A connection switching unit connected in series to at least one of a front stage and a rear stage of each of the power conversion units;
An opening / closing control unit that controls the opening / closing operation of the connection opening / closing unit;
Equipped with
An output end of the power generation device is connected in parallel with an input / output end of the power storage device ;
The switching control unit is configured such that a first total power value, which is a sum of power values of first output powers output from the respective power conversion units when the power conversion operation is performed in all the power conversion units, The sum of the power values of the second output powers output from the part of the power conversion units when the power conversion operation is performed in part of the power conversion units of all the power conversion units; If it is less than 2 total power value,
The connection switching unit connected to at least one of the front stage and the rear stage of the part of the power converters among all the power converters is caused to perform a closing operation;
The remaining portion of the power conversion unit upstream and downstream of the power control system Ru is the opening operation the connection opening and closing section connected to at least one of of all the power conversion unit. The connecting opening section, the power control system of claim 1 connected in series to both the upstream and downstream of the power conversion unit of each. It further comprises a bidirectional voltage conversion unit provided between the power storage device and the first current path and the power generation device,
The power control system of claim 1 or claim 2 wherein the conversion control unit further controls the voltage conversion operation of the bidirectional voltage converter. Respectively provided between the first electric path and the power conversion unit of each said plurality of voltage conversion units to the voltage converting the voltage value of power input from the first electric path in the rated voltage value of the power converter unit And further
The power control system according to any one of claims 1 to 3 , wherein the conversion control unit further controls voltage conversion operations of the plurality of voltage conversion units. The power control system according to any one of claims 1 to 4, further comprising a plurality of insulating transformers provided between each of the power conversion units and the second current path.

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