JP2010238010A - Converter control device, and system interconnection inverter system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system interconnection inverter system having a plurality of solar cell modules and DC/DC converters which copes with a change in the status of solar radiation to part of the solar cell modules after installation. <P>SOLUTION: The system interconnection inverter system includes a connection device for switching a parallel connection state of the plurality of solar cell modules, and a converter control device 9 includes a determination means 91 for determining whether or not each solar cell module is connected in parallel with the others. A PWM signal output means 92 is configured to output to the DC/DC converters connected to solar cell modules connected in parallel a PWM signal corresponding to the solar cell module group of solar cell modules connected in parallel, and to output to the DC/DC converters connected to solar cell modules that are not connected in parallel with any other solar cell modules PWM signals corresponding to the solar cell modules. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a converter control device that controls each DC / DC converter connected to each of a plurality of power supply devices, and a grid-connected inverter system using the converter control device.

  2. Description of the Related Art Conventionally, a grid-connected inverter system has been developed that converts DC power output from a DC power source such as a solar battery into AC power and supplies it to a commercial power system. In a grid-connected inverter system using a solar cell module in which a plurality of solar cells are connected in series as a DC power supply, a DC / DC converter is provided between the solar cell module and the inverter, so that the output power of the solar cell module is maximized. As described above, those that control the output voltage of the solar cell module have been developed.

  FIG. 8 is a diagram showing a grid-connected inverter system provided with three solar cell modules. In the figure, a state where the grid-connected inverter system 10 is linked to the commercial power grid 60 is shown. In this case, the inverter 50 has a voltage Vd between the DC / DC converters 410, 420, 430 and the inverter 50 (hereinafter referred to as “bus” as necessary) so that the output voltage matches the system voltage of the commercial power system 60. The voltage Vd ") is controlled to be constant. The grid-connected inverter system 10 includes three solar cell modules 210, 220, and 230, and DC / DC converters 410, 420, and 430 connected to them. Since the bus voltage Vd is constant, the DC / DC converters 410, 420, and 430 can control the output voltages V1, V2, and V3 of the solar cell modules 210, 220, and 230 to arbitrary voltages, respectively.

  The control device 90 outputs the output power PW1 (= V1 × I1) of the solar cell module 210 from the output current I1 of the solar cell module 210 detected by the current sensor 710 and the output voltage V1 of the solar cell module 210 detected by the voltage sensor 810. ) And the DC / DC converter 410 is controlled so that the output power PW1 is maximized. Thereby, the solar cell module 210 is controlled so that the output power PW1 becomes maximum. Similarly, the solar cell modules 220 and 230 are also controlled by the DC / DC converters 420 and 430 so that the output powers PW2 (= V2 × I2) and PW3 (= V3 × I3) become maximum. Thus, since the output power PW1, PW2, PW3 of the solar cell modules 210, 220, 230 is independently controlled to the maximum power, the grid-connected inverter system 10 can efficiently supply power.

JP 11-318042 A

  However, there is a problem when the output power PW1, PW2, PW3 of any of the solar cell modules 210, 220, 230 is extremely reduced due to a change in the solar radiation condition after the solar cell modules 210, 220, 230 are installed. Occurs. For example, after solar cell modules 210, 220, and 230 are installed on the roof of a house, a condominium is constructed nearby, so that solar radiation to solar cell modules 210 and 220 is reduced and output power PW1, PW2 is extremely low. When the voltage decreases, the output voltages V1 and V2 of the solar cell modules 210 and 220 may not satisfy the input voltage specification of the inverter 50. In addition, if there is a request to change only some modules to another company's or another company's performance after installing the solar cell, it is necessary to make a batch with the same manufacturer or performance due to the difference in performance There is.

  The present invention has been conceived under the circumstances described above, and when the solar radiation status of some solar cell modules changes after the solar cell module is installed, or some of the solar cell modules have different performance. An object of the present invention is to provide a grid-connected inverter system including a plurality of solar cell modules and a DC / DC converter that can cope with a change to a configured module group.

  In order to solve the above problems, the present invention takes the following technical means.

  The converter control device provided by the first aspect of the present invention is a grid-connected inverter system including a plurality of power supply devices and a DC / DC converter connected to each of the power supply devices. Converter controller for controlling a DC / DC converter, by comparing the input voltages of any two of the DC / DC converters, whether or not the power supply devices connected to them are connected in parallel And a DC / DC converter connected to the power supply device that is determined to be connected in parallel with any of the power supply devices by the determination device, in parallel with the determined power supply device. Outputs a PWM signal corresponding to a power supply group consisting of connected power supply apparatuses, and is parallel to any of the power supply apparatuses by the determination means. The connected DC / DC converter to the determined power supply not been continued, characterized by comprising a PWM signal output means for outputting a PWM signal corresponding to the discriminated power device.

  According to this configuration, the PWM signal corresponding to the power supply device group including the power supply devices connected in parallel is input to the DC / DC converter connected to these power supply devices and connected in parallel to the other power supply devices. A PWM signal corresponding to a power supply device that is not present is input to a DC / DC converter connected to the power supply device. Therefore, it is not necessary to switch the PWM signal generation method in accordance with the state of parallel connection of the power supply devices. Since the input voltage of the DC / DC converter that was originally input to generate the PWM signal is used to determine whether or not they are connected in parallel, the hardware configuration of the conventional converter control device should be used without change. Can do.

  In a preferred embodiment of the present invention, when it is determined by the determination means that all the power supply devices are connected in parallel, it is determined that the power supply devices are in parallel, and none of the power supply devices are connected in parallel. When the determination means determines that the state is an independent state, the PWM signal output means determines that the determination means determines that the parallel state is present from all the power supply devices connected in parallel. PWM signals corresponding to the power supply device group to be output to all the DC / DC converters, and when the determination means determines the independent state, the PWM signal corresponding to each power supply device is supplied to the power supply device. Each is output to the connected DC / DC converter.

  In a preferred embodiment of the present invention, the PWM signal output means outputs a PWM signal for controlling the output power of each power supply device or each power supply device group to be maximum.

  According to this configuration, since the output power of each power supply device or each power supply device group is controlled to be maximized, the grid-connected inverter system can supply power efficiently.

  In a preferred embodiment of the present invention, when the difference between the input voltage of one DC / DC converter and the input voltage of the other DC / DC converter is equal to or less than a predetermined value, the discrimination means It is determined that the power supply device connected to the converter and the power supply device connected to the other DC / DC converter are connected in parallel, the input voltage of the one DC / DC converter and the other DC / DC converter When the difference between the input voltage and the input voltage is larger than the predetermined value, the power supply device connected to the one DC / DC converter and the power supply device connected to the other DC / DC converter are not connected in parallel. Determine.

  The grid-connected inverter system provided by the second aspect of the present invention is connected to a plurality of solar cell modules, a connection device for switching the state of parallel connection of the solar cell modules, and the solar cells, respectively. 5. A DC / DC converter, a converter control device according to claim 1, and an inverter that converts DC power output from the plurality of DC / DC converters into AC power.

  According to this structure, the state of the parallel connection of each said solar cell module can be switched by the said connection apparatus. Therefore, even if the solar radiation status of some solar cell modules has changed after installing each of the solar cell modules, or even when changing to a module group composed of solar cell modules with different performance, This can be handled by switching the state. Further, it is not necessary to switch the PWM signal generation method in accordance with the switching of the connection device.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

1 is a block diagram illustrating a grid-connected inverter system including a first embodiment of a converter control device according to the present invention. It is an example of a structure of the connection apparatus in 1st Embodiment. It is a block diagram which shows the structure of the control apparatus in 1st Embodiment. It is a flowchart for demonstrating the determination method of the state of a connection apparatus in 1st Embodiment. It is an example of a structure of the connection apparatus in 2nd Embodiment. It is a flowchart for demonstrating the determination method of the state of a connection apparatus in 2nd Embodiment. It is a flowchart for demonstrating the other determination method in 2nd Embodiment. It is a block diagram which shows the conventional grid connection inverter system.

  Embodiments of the present invention will be specifically described below with reference to the drawings.

  FIG. 1 is a block diagram showing a grid-connected inverter system provided with a first embodiment of a converter control device according to the present invention. The grid interconnection inverter system 1 converts the DC power output from the solar cell modules 21, 22 and 23 into AC power by the inverter 5 and outputs the AC power to the commercial power grid 6. As shown in the figure, the grid-connected inverter system 1 includes solar cell modules 21, 22, 23, a connection device 3, DC / DC converters 41, 42, 43, an inverter 5, a commercial power system 6, a current sensor 71, 72, 73, voltage sensors 81, 82, 83, and a control device 9 are provided. The solar cell modules 21, 22, and 23 are connected to DC / DC converters 41, 42, and 43, respectively, the DC / DC converters 41, 42, and 43 are connected to the inverter 5, and the inverter 5 is connected to the commercial power system 6. Yes.

  Each of the solar cell modules 21, 22, and 23 is formed by connecting a plurality of solar cells in series, and outputs direct-current power generated by the solar cell converting solar energy into electric energy. Generally, a solar cell module outputs different electric power depending on the number of solar cells connected in series and the solar radiation intensity received by the solar cell. Therefore, when installed in a place with a large area, the number of series solar cells can be increased, so that a large amount of power can be output. Moreover, even if it is installed in a place with good sunlight conditions, it can output a large amount of power. The solar cell modules 21, 22, and 23 have different numbers of solar cells in series and different solar radiation conditions depending on where they are installed, so that the output power differs.

  The connection device 3 is provided across three connection lines connecting the solar cell modules 21, 22, 23 and the DC / DC converters 41, 42, 43, respectively, and the three connection lines are connected to each other. And an independent state that is not connected. When the three connection lines are connected to each other, the solar cell modules 21, 22, and 23 are connected in parallel. Hereinafter, this state is referred to as a “parallel state”. The state in which the three connection lines are independent is referred to as an “independent state”.

  When the solar cell modules 21, 22, and 23 are installed, the connection device 3 is determined and set to be in a parallel state or an independent state. When each solar cell module 21, 22, 23 can output appropriate electric power and can be efficiently supplied with power by being controlled independently, the connecting device 3 is in an independent state. Is set as follows. On the other hand, when any one of the solar cell modules 21, 22, and 23 cannot output sufficient power alone, the connection device 3 is set to be in a parallel state. After setting the connection device 3 in an independent state and installing the solar cell modules 21, 22, 23, the solar radiation condition becomes worse and each solar cell module 21, 22, 23 can output sufficient power alone. When it disappears, the user can switch the connection apparatus 3 to a parallel state. On the contrary, after setting the connection device 3 in the parallel state and installing the solar cell modules 21, 22, 23, the solar radiation condition is improved and each solar cell module 21, 22, 23 may output appropriate power. When it becomes possible, the user can switch the connection device 3 to the independent state. Moreover, it can switch to an independent state also when changing into a module group which comprised a part with solar cell module from which performance differs.

  FIG. 2 shows an example of the configuration of the connection device 3, which includes two switches 31 and 32. The switches 31 and 32 are mechanical switches that can be switched on and off in conjunction with each other. When the switches 31 and 32 are on, the three connection lines are connected in parallel. When the switches 31 and 32 are off, the three connection lines are independent and independent. Become. The configuration of the connection device 3 is not limited to this. For example, an electronic switch such as a transistor may be provided instead of the mechanical switches 31 and 32, and the base voltage of the transistor may be switched to switch between the parallel state and the independent state.

  The DC / DC converters 41, 42, 43 are connected to the solar cell modules 21, 22, 23, respectively, and the DC voltage values V 1, V 2, V 3 input from the solar cell modules 21, 22, 23 are obtained. Each is converted into another voltage value. The DC / DC converters 41, 42, and 43 step up or step down the input DC voltage by turning on and off a switching element (not shown) according to the PWM signal input from the control device 9. The DC / DC converters 41, 42, 43 supply the inverter 5 with the bus voltage Vd that has been stepped up or stepped down. In the state where the grid-connected inverter system 1 is linked to the commercial power grid 6, the inverter 5 controls the bus voltage Vd so that the DC / DC converters 41, 42, 43 are respectively The input voltage, that is, the voltage output from each of the solar cell modules 21, 22, and 23 can be controlled.

  The inverter 5 converts the DC power input from the DC / DC converters 41, 42, and 43 into AC power by turning on and off a switching element (not shown). The inverter 5 outputs AC power from which switching noise has been removed by a low-pass filter (not shown) to the commercial power system 6. In FIG. 1, a control device that controls the power conversion operation of the inverter 5 is omitted. In a state where the grid-connected inverter system 1 is linked to the commercial power grid 6, the inverter 5 performs control to keep the bus voltage Vd constant.

  The current sensors 71, 72, 73 are connected in series to the input sides of the DC / DC converters 41, 42, 43, respectively, and detect currents input to the DC / DC converters 41, 42, 43, respectively. is there. In the independent state, the solar cell modules 21, 22, and 23 are connected only to the DC / DC converters 41, 42, and 43, respectively. Therefore, the currents detected by the current sensors 71, 72, and 73 are the solar cell modules. The output current is 21, 22, and 23. In the parallel state, currents detected by the current sensors 71, 72, 73 are DC / DC converters 41, 42, 42, respectively, among the output currents of the solar cell module group in which the solar cell modules 21, 22, 23 are connected in parallel. This is the current input to 43. The current sensors 71, 72 and 73 output the detected current values I 1, I 2 and I 3 to the control device 9.

  The voltage sensors 81, 82, and 83 are connected to the input sides of the DC / DC converters 41, 42, and 43, respectively, and detect voltages on the input sides of the DC / DC converters 41, 42, and 43, respectively. In the independent state, the solar cell modules 21, 22, and 23 are connected only to the DC / DC converters 41, 42, and 43, respectively. Therefore, the voltages detected by the voltage sensors 81, 82, and 83 are the solar cell modules. The output voltages are 21, 22, and 23. In the parallel state, the voltage detected by the voltage sensors 81, 82, 83 is the output voltage of the solar cell module group in which the solar cell modules 21, 22, 23 are connected in parallel. The voltage sensors 81, 82, 83 output voltage values V 1, V 2, V 3 of the detected voltages to the control device 9, respectively.

  The control device 9 controls the DC / DC converters 41, 42 and 43. The control device 9 generates PWM signals from the current values I1, I2, and I3 input from the current sensors 71, 72, and 73 and the voltage values V1, V2, and V3 input from the voltage sensors 81, 82, and 83, respectively. Then, the PWM signal is controlled by outputting it to the DC / DC converters 41, 42 and 43.

  FIG. 3 is a block diagram showing the configuration of the control device 9. The control device 9 includes a voltage comparison unit 91 and a PWM signal generation unit 92.

  The voltage comparison unit 91 compares the voltage values V1, V2, and V3 input from the voltage sensors 81, 82, and 83, respectively, and determines whether the connection device 3 is in a parallel state or an independent state. is there. The voltage comparison unit 91 outputs the determination result as a signal to the PWM signal generation unit. In the present embodiment, when the connection device 3 is in a parallel state, the voltages on the input side of the DC / DC converters 41, 42, and 43 are equal, and when the connection device 3 is in an independent state, the DC / DC converter 41 , 42 and 43 are used to determine the state of the connection device 3 by utilizing the different voltages on the input side.

  FIG. 4 is a flowchart for explaining a method for determining whether the connection device 3 is in a parallel state or an independent state, which is performed in the voltage comparison unit 91. The determination may be performed every time the voltage values V1, V2, and V3 are input, or may be performed every day at a predetermined time. In order to be able to respond immediately to changes in the connection state, the determination interval may be shortened. In order to reduce the burden caused by the processing for determination, the determination interval may be increased.

First, voltage values V1, V2, and V3 are input (S1). It is determined whether or not the difference between the voltage value V1 and the voltage value V2 is equal to or less than a predetermined voltage value ΔV (S2). The predetermined voltage value ΔV is a value set in advance to eliminate measurement errors of the voltage sensors 81, 82, and 83. If the difference between the two voltage values is equal to or smaller than this value, the two are the same voltage. It is set so that it can be determined. When the predetermined voltage value ΔV is set to an excessively small value, even if the voltage is the same, it is determined that the voltage is not the same due to the measurement error of the voltage sensor. Since it is determined that there is, an appropriate value should be set by experiment.

  When the difference between the voltage value V1 and the voltage value V2 is equal to or less than the predetermined voltage value ΔV (S2: YES), that is, when it is determined that the voltage value V1 and the voltage value V2 are the same voltage, the voltage value V2 It is determined whether or not the difference between the voltage value V3 and the voltage value V3 is equal to or less than a predetermined voltage value ΔV (S3). Even in the parallel state, the voltage value V1 and the voltage value V2 may accidentally become the same voltage. Therefore, the voltage value V2 and the voltage value V3 are compared.

When the difference between the voltage value V2 and the voltage value V3 is equal to or less than the predetermined voltage value ΔV (S3: YES), that is, when it is determined that the voltage value V2 and the voltage value V3 are the same voltage, the voltage value V3 It is determined whether or not the difference between the voltage value V1 and the voltage value V1 is equal to or less than a predetermined voltage value ΔV (S4). When the voltage value V1 and the voltage value V2 are the same voltage, and the voltage value V2 and the voltage value V3 are the same voltage, it is normally considered that the voltage values V1, V2, and V3 are also the same voltage. However, for example, V2 = V1 +
When ΔV and V3 = V2 + ΔV, V3 = V1 + 2ΔV, and the voltage value V3 and the voltage value V1 may not be the same voltage. Therefore, as a precaution, the voltage value V3 and the voltage value V1 are also compared.

  When the difference between the voltage value V3 and the voltage value V1 is equal to or less than the predetermined voltage value ΔV (S4: YES), that is, when it is determined that the voltage value V3 and the voltage value V1 are the same voltage, It is determined that there is a signal, and a signal indicating the parallel state is output to the PWM signal generator (S5).

  When the difference between the voltage value V1 and the voltage value V2 is not less than or equal to the predetermined voltage value ΔV (S2: NO), when the difference between the voltage value V2 and the voltage value V3 is not less than or equal to the predetermined voltage value ΔV (S3: NO), Alternatively, when the difference between the voltage value V3 and the voltage value V1 is not equal to or less than the predetermined voltage value ΔV (S4: NO), it is determined that the state is independent and a signal indicating that the state is independent is output to the PWM signal generation unit 92. (S6).

  Note that if the difference between the voltage value V2 and the voltage value V3 is equal to or smaller than the predetermined voltage value ΔV in step S3, it may be determined that the state is independent, and step S4 may be omitted and the process may proceed to step S5. Further, when the difference between the voltage value V1 and the voltage value V2 is equal to or smaller than the predetermined voltage value ΔV in step S2, it is determined that the state is independent, and the process proceeds to step S5 while omitting steps S3 and S4. .

Note that the comparison method of the voltage values V1, V2, and V3 is not limited to this, and it may be determined by another method whether the state is a parallel state or an independent state. For example, an average value V ′ of the voltage values V1, V2, and V3 is calculated, and when the differences between the voltage values V1, V2, V3, and V ′ are all equal to or less than a predetermined value, the parallel state is determined. It may be.

  Returning to FIG. 3, the PWM signal generation unit 92 includes voltage values V1, V2, and V3 input from the voltage sensors 81, 82, and 83, and current values I1, I2 input from the current sensors 71, 72, and 73, respectively. , I3 and the determination signal input from the voltage comparison unit 91, the PWM signals P1, P2, P3 are generated.

  When the determination signal is a signal indicating an independent state, the PWM signal generation unit 92 generates PWM signals to be input to the DC / DC converters 41, 42, and 43, respectively. That is, the output power value PW1 (= V1 × I1) of the solar cell module 21 is calculated from the voltage value V1 input from the voltage sensor 81 and the current value I1 input from the current sensor 71, and the output power value PW1 is maximized. The PWM signal P1 for controlling to be generated is generated. Since the control for maximizing the output power value is known as so-called maximum power tracking control, the description thereof is omitted. Similarly, control is performed so that the output power value PW2 (= V2 × I2) of the solar cell module 22 calculated from the voltage value V2 input from the voltage sensor 82 and the current value I2 input from the current sensor 72 is maximized. Output signal value PW3 (= V3 × I3) of the solar cell module 23 generated from the voltage value V3 input from the voltage sensor 83 and the current value I3 input from the current sensor 73. ) Is generated to maximize the PWM signal P3.

  When the determination signal is a signal indicating a parallel state, the PWM signal generation unit 92 generates a common PWM signal to be output to the DC / DC converters 41, 42, and 43. That is, the PWM signal P for controlling to maximize the output power value PWs of the solar cell module group in which the solar cell modules 21, 22 and 23 are connected in parallel is generated. The output power value PWs of the solar cell module group is the total current value I (= I1 + I2 + I3) of the voltage value V1 input from the voltage sensor 81 and the current values I1, I2, and I3 input from the current sensors 71, 72, and 73. Is calculated from The PWM signal generation unit 92 outputs the PWM signal P to the DC / DC converters 41, 42, and 43 as PWM signals P1, P2, and P3, respectively.

  Next, the operation of the grid interconnection inverter system 1 will be described.

  In the present embodiment, the solar cell modules 21, 22, and 23 can be easily switched between the parallel state and the independent state by the connection device 3. Therefore, even if the solar radiation status of some solar cell modules has changed after installing the solar cell modules 21, 22, 23, or even when changing to a module group composed of solar cell modules with different performance, This can be handled by switching between the parallel state and the independent state.

  In the present embodiment, the control device 9 determines the connection state of the solar cell modules 21, 22, and 23 based on the voltage values V1, V2, and V3 input from the voltage sensors 81, 82, and 83, and responds accordingly. Generate and output a PWM signal. Therefore, there is no need to switch the PWM signal generation method when the connection device 3 is switched. Since the connection state is determined only by arithmetic processing using the input voltages of the DC / DC converters 41, 42, and 43 that are originally input to generate the PWM signal, the hardware configuration of the conventional control device is changed. It can be used without doing.

  In the first embodiment, the connection device 3 includes a parallel state in which all the solar cell modules 21, 22, and 23 are connected in parallel and an independent state in which none of the solar cell modules 21, 22, and 23 are connected in parallel. The case of switching was explained. A second embodiment in which the connection device 3 can connect any two of the solar cell modules 21, 22, 23 in parallel will be described below.

  The block diagram of the grid connection inverter system provided with 2nd Embodiment of the converter control apparatus which concerns on this invention becomes the same as that of FIG. In the present embodiment, the configuration of the connection device 3 and the control performed by the control device 9 are different from those in the first embodiment.

  FIG. 5 shows an example of the configuration of the connection device 3 ′ according to the present embodiment, which includes three switches 31 ′, 32 ′, and 33 ′. The switches 31 ', 32', and 33 'can be individually switched on and off. When only the switch 31 'is on, the solar cell module 21 and the solar cell module 22 are connected in parallel, and the solar cell module 23 is in a single state. When only the switch 32 ′ is on, the solar cell module 22 and the solar cell module 23 are connected in parallel, and the solar cell module 21 is in a single state. When only the switch 33 ′ is on, the solar cell module 21 and the solar cell module 23 are connected in parallel, and the solar cell module 22 is in a single state. When any two or more of the switches 31 ′, 32 ′, and 33 ′ are on, the solar cell modules 21, 22, and 23 are in a parallel state, and when all of the switches 31 ′, 32 ′, and 33 ′ are off, Become independent. The configuration of the connection device 3 is not limited to this. For example, a transistor may be provided in place of the switches 31 ′, 32 ′, and 33 ′, and switching between on and off may be performed by switching the base voltage of the transistor.

  The block diagram of the control device 9 in the present embodiment is the same as FIG. However, the control performed by the control device 9 is different from that of the first embodiment. The voltage comparison unit 91 compares the voltage values V1, V2, and V3 input from the voltage sensors 81, 82, and 83, respectively, and determines the connection state of the connection device 3 '.

  FIG. 6 is a flowchart for explaining a method for determining the connection state of the connection device 3 ′ performed by the voltage comparison unit 91. The timing of the determination may be set as appropriate.

  First, voltage values V1, V2, and V3 are input (S11). It is determined whether or not the difference between the voltage value V1 and the voltage value V2 is equal to or less than a predetermined voltage value ΔV (S12). The predetermined voltage value ΔV is a value set in advance based on measurement errors of the voltage sensors 81, 82, and 83, and an appropriate value is set by experiment.

  When the difference between the voltage value V1 and the voltage value V2 is equal to or smaller than the predetermined voltage value ΔV (S12: YES), it is determined whether or not the difference between the voltage value V2 and the voltage value V3 is equal to or smaller than the predetermined voltage value ΔV. (S13). When the difference between the voltage value V2 and the voltage value V3 is equal to or smaller than the predetermined voltage value ΔV (S13: YES), it is determined whether or not the difference between the voltage value V3 and the voltage value V1 is equal to or smaller than the predetermined voltage value ΔV. (S14). When the difference between the voltage value V3 and the voltage value V1 is equal to or less than the predetermined voltage value ΔV (S14: YES), since all the voltage values are the same, it is determined that they are in the parallel state, and a signal indicating that they are in the parallel state It is output to the PWM signal generator 92 (S15).

  In step S14, when the difference between the voltage value V3 and the voltage value V1 is not less than or equal to the predetermined voltage value ΔV (S14: NO), the process returns to step S11. That is, when the voltage value V1 and the voltage value V2 are the same voltage, and the voltage value V2 and the voltage value V3 are the same voltage, but the voltage value V3 and the voltage value V1 are different, the detected voltage value is suspicious. Therefore, the voltage values V1, V2, and V3 are input again to perform determination processing.

  In step S13, if the difference between the voltage value V2 and the voltage value V3 is not equal to or less than the predetermined voltage value ΔV (S13: NO), whether or not the difference between the voltage value V3 and the voltage value V1 is equal to or less than the predetermined voltage value ΔV. Is determined (S16). When the difference between the voltage value V3 and the voltage value V1 is equal to or less than the predetermined voltage value ΔV (S16: YES), the process returns to step S11. That is, if the voltage value V1 and the voltage value V2 are the same voltage, and the voltage value V3 and the voltage value V1 are the same voltage, but the voltage value V2 and the voltage value V3 are different, the detected voltage value is suspicious. Therefore, the voltage values V1, V2, and V3 are input again to perform the determination process. When the difference between the voltage value V3 and the voltage value V1 is not less than or equal to the predetermined voltage value ΔV (S16: NO), only the switch 31 ′ is turned on and the solar cell module 21 and the solar cell module 22 are connected in parallel. A signal to that effect is output to the PWM signal generator 92 (S17).

  In step S12, if the difference between the voltage value V1 and the voltage value V2 is not equal to or less than the predetermined voltage value ΔV (S12: NO), whether or not the difference between the voltage value V2 and the voltage value V3 is equal to or less than the predetermined voltage value ΔV. Is determined (S18). When the difference between the voltage value V2 and the voltage value V3 is equal to or smaller than the predetermined voltage value ΔV (S18: YES), it is determined whether or not the difference between the voltage value V3 and the voltage value V1 is equal to or smaller than the predetermined voltage value ΔV. (S19). When the difference between the voltage value V3 and the voltage value V1 is equal to or less than the predetermined voltage value ΔV (S19: YES), the process returns to step S11. That is, when the voltage value V2 and the voltage value V3 are the same voltage, and the voltage value V3 and the voltage value V1 are the same voltage, but the voltage value V1 and the voltage value V2 are different, the detected voltage value is suspicious. Therefore, the voltage values V1, V2, and V3 are input again to perform the determination process. When the difference between the voltage value V3 and the voltage value V1 is not less than or equal to the predetermined voltage value ΔV (S19: NO), only the switch 32 ′ is turned on, and the solar cell module 22 and the solar cell module 23 are connected in parallel. A signal to that effect is output to the PWM signal generator 92 (S20).

  In step S18, if the difference between the voltage value V2 and the voltage value V3 is not equal to or less than the predetermined voltage value ΔV (S18: NO), whether or not the difference between the voltage value V3 and the voltage value V1 is equal to or less than the predetermined voltage value ΔV. Is determined (S21). When the difference between the voltage value V3 and the voltage value V1 is equal to or less than the predetermined voltage value ΔV (S21: YES), only the switch 33 ′ is turned on and the solar cell module 23 and the solar cell module 21 are connected in parallel. Is output to the PWM signal generator 92 (S22). If the difference between the voltage value V3 and the voltage value V1 is not less than or equal to the predetermined voltage value ΔV (S21: NO), all the voltage values are different, so it is determined that the state is independent, and a signal indicating that the state is independent is PWM. The signal is output to the signal generator 92 (S23).

  Note that the method of comparing the voltage values V1, V2, and V3 is not limited to this, and other methods may be used for comparison and determination.

  FIG. 7 is a flowchart for explaining another determination method. This determination method is a simplification of the determination method shown in the flowchart of FIG. The flowchart shown in the figure is obtained by removing steps S14, S16, and S19 from the flowchart shown in FIG.

  In the flowchart shown in the figure, if the difference between the voltage value V2 and the voltage value V3 is equal to or smaller than the predetermined voltage value ΔV in step S13 (S13: YES), the process proceeds to step S15. If the voltage value V1 and the voltage value V2 are the same voltage and the voltage value V2 and the voltage value V3 are the same voltage, the voltage value V3 and the voltage value V1 need not be compared and are in a parallel state. This is because it can be estimated. If the difference between the voltage value V2 and the voltage value V3 is not less than or equal to the predetermined voltage value ΔV in step S13 (S13: NO), the process proceeds to step S17. This is because if the voltage value V1 and the voltage value V2 are the same voltage and the voltage value V2 and the voltage value V3 are different, it can be estimated that the voltage value V3 and the voltage value V1 are different without being compared. is there. Similarly, if the difference between the voltage value V2 and the voltage value V3 is equal to or less than the predetermined voltage value ΔV in step S18 (S18: YES), it can be estimated that the voltage value V3 and the voltage value V1 are different, so step S19 Is going on.

  The PWM signal generation unit 92 of the control device 9 in this embodiment differs from the first embodiment in generating PWM signals P1, P2, and P3 based on the determination signal input from the voltage comparison unit 91. When the determination signal is a signal indicating the parallel state (see step S15 in FIG. 6) and when the determination signal is a signal indicating the independent state (see step S23 in FIG. 6), it is the same as in the first embodiment. I will omit it.

When the determination signal is a signal indicating that the solar cell module 21 and the solar cell module 22 are connected in parallel (see step S17 in FIG. 6), the PWM signal generation unit 92 includes the DC / DC converter 41, The common PWM signal P output to 42 and the PWM signal P3 output to the DC / DC converter 43 are generated. PWM signal P is a PWM signal for the solar cell module 21 and 22 is controlled so as to maximize the output power value PW ₁₂ parallel-connected solar cell modules. Output power value PW ₁₂ of the solar battery module group is calculated from the total current value I of the current value I1, I2 input from the voltage value V1 and the current sensor 71, 72 is inputted from the voltage sensor 81 (= I1 + I2) , PW ₁₂ = V1 × (I1 + I2). The PWM signal generation unit 92 outputs the PWM signal P to the DC / DC converters 41 and 42 as PWM signals P1 and P2, respectively. The PWM signal P3 maximizes the output power value PW3 (= V3 × I3) of the solar cell module 23 calculated from the voltage value V3 input from the voltage sensor 83 and the current value I3 input from the current sensor 73. It is a PWM signal for controlling to do. The PWM signal generation unit 92 outputs the PWM signal P3 to the DC / DC converter 43.

When the determination signal is a signal indicating that the solar cell module 22 and the solar cell module 23 are connected in parallel (see step S20 in FIG. 6), the PWM signal generation unit 92 includes the DC / DC converter 42, A common PWM signal P to be output to 43 and a PWM signal P1 to be output to the DC / DC converter 41 are generated. PWM signal P is a PWM signal for controlling so as to maximize the output power value PW ₂₃ of the solar cell module group and the solar cell modules 22 and 23 are connected in parallel. Output power value PW ₂₃ of the solar battery module group is calculated from the total current value I of the voltage value V2 and the current value I2, I3 (= I2 + I3 ), a _{PW 23 = V2 × (I2 +} I3). The PWM signal generation unit 92 outputs the PWM signal P to the DC / DC converters 42 and 43 as PWM signals P2 and P3, respectively. The PWM signal P1 is a PWM signal for controlling the output power value PW1 (= V1 × I1) of the solar cell module 21 calculated from the voltage value V1 and the current value I1 to be maximum. The PWM signal generation unit 92 outputs the PWM signal P1 to the DC / DC converter 41.

When the determination signal is a signal indicating that the solar cell module 23 and the solar cell module 21 are connected in parallel (see step S22 in FIG. 6), the PWM signal generation unit 92 includes the DC / DC converter 43, The common PWM signal P output to 41 and the PWM signal P2 output to the DC / DC converter 42 are generated. The PWM signal P is a PWM signal for controlling the output power value PW ₃₁ of the solar cell module group in which the solar cell modules 23 and 21 are connected in parallel to the maximum. The output power value PW ₃₁ of the solar cell module group is calculated from the total current value I (= I3 + I1) of the voltage value V3 and the current values I3 and I1, and is PW ₃₁ = V3 × (I3 + I1). The PWM signal generation unit 92 outputs the PWM signal P to the DC / DC converters 43 and 41 as PWM signals P3 and P1, respectively. The PWM signal P2 is a PWM signal for controlling the output power value PW2 (= V2 × I2) of the solar cell module 22 calculated from the voltage value V2 and the current value I2 to be maximized. The PWM signal generation unit 92 outputs the PWM signal P2 to the DC / DC converter 42.

  In the present embodiment, the connection state of the solar cell modules 21, 22, and 23 can be easily switched to various states by the connection device 3 '. Therefore, even if the solar radiation status of some solar cell modules has changed after installing the solar cell modules 21, 22, 23, or even when changing to a module group composed of solar cell modules with different performance, This can be dealt with by switching the parallel connection state.

  In the present embodiment, the control device 9 determines the connection state of the solar cell modules 21, 22, and 23 based on the voltage values V1, V2, and V3 input from the voltage sensors 81, 82, and 83, and responds accordingly. Generate and output a PWM signal. Therefore, it is not necessary to switch the PWM signal generation method when the connection device 3 ′ is switched. Since the connection state is determined only by arithmetic processing using the input voltages of the DC / DC converters 41, 42, and 43 that are originally input to generate the PWM signal, the hardware configuration of the conventional control device is changed. It can be used without doing.

  In the above embodiment, the PWM signal for controlling the output power of the solar cell modules connected in parallel is generated based on the current value obtained by adding the current values input to the DC / DC converters. However, you may make it produce | generate based on the electric current value input into one of DC / DC converters. This is because each DC / DC converter is controlled by a common PWM signal, so that the current value input to each DC / DC converter is proportional to the output current value of the solar cell module group.

  Moreover, in the said embodiment, although the same PWM signal P is output to the DC / DC converter connected to each solar cell module connected in parallel, it is not restricted to this. For example, in order to balance control so that there is no bias in the current input to each DC / DC converter, a PWM signal obtained by changing the PWM signal P based on the difference in input current is output. Also good.

  Moreover, in the said embodiment, although the case where there were three solar cell modules was demonstrated, it is not restricted to this. The present invention can be applied to the case where there are two solar cell modules or four or more solar cell modules.

  Moreover, although the said embodiment demonstrated the case where a connection apparatus was switched artificially when the change of a solar radiation situation arose after installing a solar cell module, it is not restricted to this. For example, when the connection state of the solar cell module is changed according to the change in solar radiation intensity with time, the connection state may be switched based on a detection value of a solar radiation intensity meter or a timer.

  Moreover, although the said embodiment demonstrated the case where a power supply device was a solar cell module, it is not restricted to this. For example, the power supply device may be a fuel cell, or a device that converts AC power generated by a wind power generator, a hydroelectric generator such as a water turbine, a geothermal power generator, a wave power generator, etc. into DC power and outputs it. It may be. The present invention is particularly effective in a power supply apparatus in which the amount of power generation varies depending on conditions that cannot be artificially changed, such as natural conditions.

  The converter control device and the grid-connected inverter system according to the present invention are not limited to the above-described embodiments. The specific configuration of each part of the converter control device and the grid-connected inverter system according to the present invention can be varied in design in various ways.

1 Grid-connected inverter system 21, 22, 23 Solar cell module (power supply device)
3 connection device 41, 42, 43 DC / DC converter 5 inverter 6 commercial power system 71, 72, 73 current sensor 81, 82, 83 voltage sensor 9 control device (converter control device)
91 Voltage comparison unit (discriminating means, judging means)
92 PWM signal generator (PWM signal output means)

Claims (5)

A plurality of power supply devices; a plurality of DC / DC converters respectively connected to output terminals of the plurality of power supply devices; and the plurality of power supply devices and the plurality of DC / DC converters. Connecting means for setting one of a connection state in which the output ends of the plurality of output ends are not connected to each other and a connection state in which at least two output ends are connected among the plurality of output ends; and a plurality of DC / DC converters The plurality of DC / DC are connected to all output terminals and applied to a grid-connected inverter system including an inverter that converts DC power output from these DC / DC converters into AC power and outputs the AC power to the grid. A converter control device for controlling drive of a converter,
A determination means for determining whether or not output terminals of the power supply devices connected to the two DC / DC converters are connected to each other by comparing input voltages of any two of the DC / DC converters;
The plurality of DC / DC converters connected to the power supply devices that are determined to be connected to each other by the determining means include a plurality of power supply devices that are connected to each other. For a DC / DC converter that outputs a PWM signal generated based on output efficiency and is connected to a power supply device that is determined by the determining means that the output terminal is not connected to any of the other output terminals. PWM signal output means for outputting a PWM signal generated based on the determined output efficiency of the power supply device;
A converter control device comprising: When the determination means determines that all the output terminals of the plurality of power supply devices are connected to each other, the plurality of power supply devices are determined to be in a parallel state, and each output terminal of the plurality of power supply devices is determined. Is further provided with determination means for determining that the plurality of power supply devices are in an independent state when it is determined that none of them is connected to another output terminal,
When the determination means determines that the parallel state is present, the PWM signal output means outputs all the PWM signals generated based on the output efficiency of a power supply group consisting of all power supply apparatuses connected in parallel. A DC / DC converter connected to the power supply device that outputs to the DC / DC converter and generates a PWM signal based on the output efficiency of each power supply device when the determination means determines the independent state. Output to
The converter control device according to claim 1.   The PWM signal output means has a maximum power output from the power supply device to the DC / DC converter to which any one of the plurality of power supply devices is connected among the plurality of DC / DC converters. A plurality of DC / DC converters to which a plurality of power supply devices whose output ends are connected to each other are connected among the plurality of DC / DC converters. The converter control device according to claim 1 or 2, wherein a PWM signal for controlling the power as the power device group output from the power devices to be maximized is output.   When the difference between the input voltage of one DC / DC converter and the input voltage of the other DC / DC converter is equal to or less than a predetermined value, the determination means outputs the output of the power supply device connected to the one DC / DC converter. It is determined that the end and the output end of the power supply device connected to the other DC / DC converter are connected to each other, and the input voltage of the one DC / DC converter and the input voltage of the other DC / DC converter are determined. Is larger than the predetermined value, the output terminal of the power supply device connected to the one DC / DC converter and the output terminal of the power supply device connected to the other DC / DC converter are mutually connected. The converter control device according to claim 1, wherein the converter control device is determined not to be performed. A plurality of power supply devices; a plurality of DC / DC converters respectively connected to output terminals of the plurality of power supply devices; and the plurality of power supply devices and the plurality of DC / DC converters. Connecting means for setting one of a connection state in which the output ends of the plurality of output ends are not connected to each other and a connection state in which at least two output ends are connected among the plurality of output ends; and a plurality of DC / DC converters Converter control means for controlling drive, inverters connected to all output terminals of the plurality of DC / DC converters, converting DC power output from these DC / DC converters into AC power and outputting the AC power to the system, A grid interconnection inverter system comprising:
The converter control means includes
A determination means for determining whether or not output terminals of the power supply devices connected to the two DC / DC converters are connected to each other by comparing input voltages of any two of the DC / DC converters;
The plurality of DC / DC converters connected to the power supply devices that are determined to be connected to each other by the determining means include a plurality of power supply devices that are connected to each other. For a DC / DC converter that outputs a PWM signal generated based on output efficiency and is connected to a power supply device that is determined by the determining means that the output terminal is not connected to any of the other output terminals. PWM signal output means for outputting a PWM signal generated based on the determined output efficiency of the power supply device;
A grid-connected inverter system comprising:

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