JP2012019646A - Control device of power converter, and system interconnection inverter system using the control device - Google Patents

Abstract

Provided is a control device capable of preventing control interference by each power conversion device when switching between an individual control state and a collective control state.
When switching to an individual control state, control target voltages are set to voltage values V2 and V3, and generation of PWM signals P2 and P3 is started. When the voltage values V2 and V3 coincide with the target voltage value V1 ^* , a connecting device Is switched to an independent state, and the switching units 94 and 95 switch the control target voltage to V1 ^* , and then switch to the target voltage values V2 ^* and V3 ^* . When switching to the collective control state, the control target voltage is switched to V1 ^*, and when the V2 and V3 coincide with V1 ^* , the connecting device is switched to the parallel state, and then the control target voltage is switched to V2 and V3. The generation of the PWM signals P2 and P3 is stopped. Since all the power conversion devices perform the same control or only one power conversion device performs the control, no control interference occurs.
[Selection] Figure 2

Description

  The present invention relates to a control device that controls the operation of each power converter connected to a plurality of power supply devices, and a grid-connected inverter system using the 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 into AC power and supplies it to a power system. In addition, 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 source, 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. A device that controls the operation of the DC / DC converter (hereinafter referred to as “maximum power point tracking control”) has been developed.

  Moreover, what provided the some solar cell module and the some DC / DC converter, and changes the connection method of these solar cell modules and DC / DC converter according to the output electric power of a solar cell module is also developed. Yes.

  FIG. 7 is a diagram showing a grid-connected inverter system in which three solar cell modules and three DC / DC converters are provided. As shown in the figure, the grid-connected inverter system 100 is provided across connection lines that connect three solar cell modules 210, 220, and 230 and three DC / DC converters 410, 420, and 430, respectively. The connecting device 300 is provided. The connection device 300 includes a state in which the built-in electromagnetic contactor is closed and three connection lines are connected to each other (hereinafter referred to as “parallel state”), and a built-in electromagnetic contactor is opened to provide three connections. One of the states in which the lines are not connected to each other (hereinafter referred to as “independent state”).

  The control device 900 calculates the total value of the output power of the solar cell modules 210, 220, and 230 from the detection value of a sensor (not shown), and switches the connection device 300 and the DC / DC converter 410, based on the calculated total value. The operation of 420 and 430 is controlled. That is, when the total value is equal to or larger than the predetermined value, the connection device 300 is set to an independent state, and the operation of the DC / DC converters 410, 420, and 430 is controlled. Thereby, the maximum power point tracking control is performed on the output power of each of the solar cell modules 210, 220, and 230. Hereinafter, the control state is referred to as “individual control state”. On the other hand, when the total value is less than the predetermined value, in order to increase the conversion efficiency, the connection device 300 is placed in a parallel state and the operation of only one DC / DC converter (for example, the DC / DC converter 410) is controlled. (The other two DC / DC converters are not operated.) Thereby, the electric power output from the solar cell modules 210, 220, and 230 is batched, and the batched output power is subjected to maximum power point tracking control. Hereinafter, the control state is referred to as a “batch control state”.

JP 2001-268800 A

  However, in the grid-connected inverter system 100, there is a problem that when the individual control state and the collective control state are switched, a state in which the control by each DC / DC converter interferes with each other occurs.

The control device 900 changes from the collective control state to the individual control state when the total value of output power of the solar cell modules 210, 220, and 230 (hereinafter referred to as “total power value”) is equal to or greater than a predetermined value W ₀ . When the total power value becomes less than the predetermined value W ₀ , the individual control state is switched to the collective control state. Switching from the collective control state to the individual control state is performed by first starting the DC / DC converters 420 and 430 and then switching the connection device 300 from the parallel state to the independent state. Further, switching from the individual control state to the collective control state is performed by first switching the connection device 300 from the independent state to the parallel state, and then stopping the DC / DC converters 420 and 430.

  FIG. 8 is a time chart for explaining switching between the individual control state and the collective control state in the grid interconnection inverter system 100.

  FIG. 4A is a diagram showing the output power of the solar cell module from sunrise (time t = t0) to sunset (t = t7), the broken line indicates the total power value, and the solid line is DC / DC. The electric power input into the converter 410 is shown. At t = t1 to t2 and t = t5 to t6, the batch control state is established, and the output powers of the solar cell modules 210, 220, and 230 are collectively input to the DC / DC converter 410. Since DC / DC converters 420 and 430 are not in operation, no power is input. Therefore, the power value (solid line) input to the DC / DC converter 410 matches the total power value (broken line). From t = t3 to t4, the individual control state is set, and the output power of the solar cell modules 210, 220, and 230 is input to the DC / DC converters 410, 420, and 430, respectively. Also, at t = t2 to t3 and t4 to t5, there is a transient state between the collective control state and the individual control state, and the collective output power of the solar cell modules 210, 220, 230 is divided into the DC / DC converter 410, 420 and 430 are input. Therefore, at t = t2 to t5, the power value (solid line) input to the DC / DC converter 410 is about 1/3 of the total power value (broken line).

  FIG. 4B shows the operating state of the DC / DC converter 410, which is indicated as “ON” during operation and “OFF” during stop. The DC / DC converter 410 is activated when the grid-connected inverter system 100 becomes operable with the electric power generated by the solar cell modules 210, 220, and 230 (t = t1) and becomes inoperable. It stops at (t = t6).

FIG. 4C shows the operating state of the DC / DC converters 420 and 430, which are indicated as “ON” during operation and “OFF” during stop. The DC / DC converters 420 and 430 are activated when the total power value exceeds the predetermined value W ₀ (t = t2), and after the total power value becomes less than the predetermined value W ₀ (t = t5). It has stopped.

FIG. 4D shows the state of the connection device 300. After the total power value becomes equal to or higher than the predetermined value W ₀ and the DC / DC converters 420 and 430 are activated (t = t3), the connection device 300 is switched from the parallel state to the independent state, and the total power value is the predetermined value. When it becomes less than W ₀ (t = t4), the independent state is switched to the parallel state.

  As shown in the figure, when the individual control state and the collective control state are switched, the connection device 300 is in a parallel state and the DC / DC converters 420 and 430 are in operation (in the figure, t = t2 to t3 and t = t4 to t5). In this case, the DC / DC converters 410, 420, and 430 respectively perform maximum power point tracking control on the output power obtained by collecting the power output from the solar cell modules 210, 220, and 230. , 420 and 430 interfere with each other.

  Further, when the operation of the DC / DC converters 420 and 430 is stopped at t = t5 during the control interference, the power input to the DC / DC converter 410 increases rapidly, and the maximum power by the DC / DC converter 410 is increased. There is also a problem that the maximum power point that has been followed in the point following control changes suddenly.

  It should be noted that a separate inverter is connected for each DC / DC converter to control the operation of each DC / DC converter and simultaneously control the operation of each connected inverter, or a plurality of DC / DC converters instead of providing a DC / DC converter. In the case of providing a single inverter and controlling the operation of these inverters, the same problem occurs when the individual control state and the collective control state are switched.

  The present invention has been conceived under the circumstances described above, and provides a control device that can prevent control interference by each power conversion device when switching between an individual control state and a collective control state. That is the purpose.

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

  The control device for the power conversion device provided by the first aspect of the present invention includes a first power supply device, a first power conversion device connected to an output terminal of the first power supply device, and a second power supply device. An independent power source device, a second power conversion device connected to the output end of the second power source device, and an output end of the first power source device and an output end of the second power source device are not connected to each other. Applied to a grid-connected inverter system comprising a connection device that is in any state of a parallel state that connects a state and an output end of the first power supply device and an output end of the second power supply device, A control device that controls the operation of each of the power conversion devices so that the power output by the first power supply device and the second power supply device is maximized, and the connection device is in the parallel state. The first power converter and the second When operating the power converter, the control by the second power converter is not performed or the control target voltage of the first power converter is set as the control target voltage of the second power converter. It is characterized by that.

  The “power conversion device” generates output power required from input power. For example, an inverter that converts DC power into AC power, and DC / DC that converts DC power voltage. Includes a converter.

  In preferable embodiment of this invention, only the said 1st power converter device is drive | operated, and the said 1st power converter device and 2nd electric power are from the collective control state in which the said connection apparatus is the said parallel state. When the conversion device is operated and the connection device is switched to the individual control state in the independent state, the operation of the second power conversion device is started without performing the control by the second power conversion device. The control target voltage of the first power conversion apparatus after the output voltages of the first power supply apparatus and the second power supply apparatus connected in parallel become the control target voltage of the first power conversion apparatus. Is set as a control target voltage of the second power converter, the control by the second power converter is started, and the first power conversion is switched from the individual control state to the collective control state. The control target voltage of the second power converter is set as the control target voltage of the second power converter, and control is performed by the second power converter, and the output voltage of the second power supply device is the first power converter. After the control target voltage is reached, the control by the second power converter is stopped.

  In a preferred embodiment of the present invention, when switching from the collective control state to the individual control state, the output voltages of the first power supply device and the second power supply device connected in parallel are the first power. When the control target voltage of the conversion device is reached, the connection device is switched to the independent state.

  In a preferred embodiment of the present invention, when the individual control state is switched to the collective control state, when the output voltage of the second power supply device becomes the control target voltage of the first power conversion device. The connection device is switched to the parallel state.

  In a preferred embodiment of the present invention, when switching from the individual control state to the collective control state, the current flowing through the second power converter after the control by the second power converter is not performed. When becomes zero, the operation of the second power conversion device is stopped.

  In a preferred embodiment of the present invention, calculation means for calculating a total value of output power of the first power supply device and the second power supply device, and whether or not the total value is a predetermined value or more are determined. A discriminating unit, and when the discriminating unit discriminates that the total value is greater than or equal to the predetermined value when in the collective control state, the individual control state is switched from the collective control state to the individual control state. When the determination means determines that the total value is less than the predetermined value in the state, the individual control state is switched to the collective control state.

  In a preferred embodiment of the present invention, the first power converter and the second power converter each include a DC / DC converter.

  In preferable embodiment of this invention, the said 1st power converter device and the 2nd power converter device are provided with the inverter.

  In a preferred embodiment of the present invention, the first power supply device and the second power supply device include solar cells.

  The grid interconnection inverter system provided by the 2nd side surface of this invention is a said 1st power supply device, a said 1st power converter device, a said 2nd power supply device, and a said 2nd power converter device. And the control device provided by the first aspect of the present invention.

  According to the present invention, when the first power conversion device and the second power conversion device are operated when the connection device is in a parallel state, the control by the second power conversion device is not performed. The control target voltage of the first power converter is set as the control target voltage of the second power converter. Therefore, the first power conversion device and the second power conversion device do not perform different controls on the first power supply device and the second power supply device connected in parallel. Thereby, the interference of control by the 1st power converter and the 2nd power converter can be prevented.

  In addition, when switching from the individual control state to the collective control state, the second power conversion is performed when the current flowing through the second power conversion device becomes zero after the control by the second power conversion device is not performed. When stopping the operation of the device, the power input to the first power conversion device does not change due to the stop of the operation of the second power conversion device. Therefore, in the maximum power point tracking control by the first power converter, there is no problem that the maximum power point that has been tracked changes suddenly.

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

It is a block diagram which shows the grid connection inverter system provided with the control apparatus which concerns on this invention. It is a block diagram for demonstrating an example of the internal structure of the control apparatus which concerns on this invention. It is a flowchart for demonstrating the control state switching process (switching process of an individual control state and a collective control state) which the control apparatus which concerns on this invention performs. It is a time chart for demonstrating a control state switching process. It is a block diagram which shows the other grid connection inverter system provided with the control apparatus which concerns on this invention. It is a block diagram which shows the other grid connection inverter system provided with the control apparatus which concerns on this invention. It is a block diagram which shows the conventional grid connection inverter system. It is a time chart for demonstrating the control state switching process in 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 control device according to the present invention. The grid-connected 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 power system 6. As shown in the figure, the grid-connected inverter system 1 includes solar cell modules 21, 22, 23, connection device 3, DC / DC converters 41, 42, 43, inverter 5, current sensors 71, 72, 73, voltage Sensors 81, 82, 83 and a control device 9 are provided. Solar cell modules 21, 22, and 23 are connected to DC / DC converters 41, 42, and 43, DC / DC converters 41, 42, and 43 are connected to inverter 5, and inverter 5 is connected to power system 6. .

  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.

  The connection device 3 is provided across three connection lines that connect the solar cell modules 21, 22, and 23 and the DC / DC converters 41, 42, and 43, and receives a switching signal input from the control device 9. Based on this, either the parallel state in which the three connection lines are connected to each other, or the independent state in which the three connection lines are not connected to each other is obtained. In the parallel state, the solar cell modules 21, 22, and 23 are connected in parallel, and the electric power generated by the solar cell modules 21, 22, and 23 is bundled. In the independent state, the electric power generated by each solar cell module 21, 22, 23 is input to the DC / DC converters 41, 42, 43, respectively. In the present embodiment, the connection device 3 includes the electromagnetic contactor 31 provided between the connection line of the solar cell module 21 and the connection line of the solar cell module 22, and the connection line of the solar cell module 22 and the solar cell module. Although it is set as the structure provided with the electromagnetic contactor 32 provided between 22 connection lines, it is not restricted to this. Any configuration that can switch between the parallel state and the independent state may be used.

  The DC / DC converters 41, 42, and 43 are connected to the solar cell modules 21, 22, and 23, respectively, and a DC voltage that is input from each of the solar cell modules 21, 22, and 23 is input from the control device 9. Conversion is performed according to the PWM signals P1, P2, and P3 (in the individual control state). The DC / DC converters 41, 42, and 43 control the input voltage to a target voltage because the output voltage is fixed to a predetermined voltage Vd (hereinafter referred to as “bus voltage Vd” as necessary). be able to. Maximum power point tracking control is performed by controlling the input voltage to the target voltage and changing the target voltage so that the input power becomes maximum.

  In the collective control state, the DC / DC converter 41 receives a voltage input from the control device 9 from the solar cell modules 21, 22, 23 (hereinafter referred to as “solar cell module group”) connected in parallel. Conversion is performed according to the input PWM signal P1. Thereby, the DC / DC converter 41 performs maximum power point tracking control of the power input from the solar cell module group. In the collective control state, the operation of the DC / DC converters 42 and 43 is stopped.

  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 the AC voltage from which the switching frequency component has been removed by a low-pass filter (not shown) to the 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 power grid 6, the inverter 5 performs control to keep the bus voltage Vd constant.

  The current sensors 71, 72, and 73 are disposed on the input side of the DC / DC converters 41, 42, and 43, respectively, and detect currents that are input to 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 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, the currents detected by the current sensors 71, 72, 73 are the currents input to the DC / DC converters 41, 42, 43 among the currents input from the solar cell module group. 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 disposed on the input side of the DC / DC converters 41, 42, and 43, respectively, and detect voltages on the input side 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 voltages detected by the voltage sensors 81, 82, and 83 are voltages input from the solar cell module group. 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, 43 and the connection device 3. The control device 9 performs PWM based on 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. Signals P1, P2, P3 and a switching signal are generated. The control device 9 controls the DC / DC converters 41, 42, and 43 by inputting the PWM signals P1, P2, and P3, and controls the connection device 3 by inputting the switching signal.

Based on the total power value (total value of the output power of the solar cell modules 21, 22, 23) W calculated based on the current values I1, I2, I3 and the voltage values V1, V2, V3, the control device 9 The switching of the connection device 3 and the operation of the DC / DC converters 41, 42, 43 are controlled. That is, when the total power value W is equal to or greater than the predetermined value W ₀ , the connection device 3 is set to the independent state, and the operation of the DC / DC converters 41, 42, and 43 is controlled (individual control state). At this time, target voltage values V1 ^* , V2 ^* , and V3 ^* are set for maximum power point tracking control of the output power of each of the solar cell modules 21, 22, and 23, and the control device 9 controls the voltage values V1 and V2. , V3 generate PWM signals P1, P2, P3 so as to coincide with target voltage values V1 ^* , V2 ^* , V3 ^* , which are control target voltages, respectively, and output them to DC / DC converters 41, 42, 43, respectively. . On the other hand, when the total power value W is less than the predetermined value W ₀ , the connecting device 3 is set in a parallel state, and the operation of only the DC / DC converter 41 is controlled (collective control state). At this time, the target voltage value V1 ^* for maximum power point tracking control of the output power of the solar cell module group is set, and the control device 9 causes the PWM signal P1 so that the voltage value V1 matches the target voltage value V1 ^*. Is output to the DC / DC converter 41.

  In addition, the control device 9 switches the control target voltage during a transition in order to prevent the control by the DC / DC converters 41, 42, 43 from interfering with each other when switching between the individual control state and the collective control state.

When switching from the collective control state to the individual control state, the control device 9 sets the control target voltages of the DC / DC converters 42 and 43 as voltage values V2 and V3 input from the voltage sensors 82 and 83, respectively, and the DC / DC converter 42. , 43 is started. Since the control target voltage and the control amount are the same (the deviation is zero), the control device 9 is operating the DC / DC converters 42 and 43 but is not in control, and the DC / DC converters 42 and 43 Part of the current that has been flowing only to the DC / DC converter 41 until now flows. Since the voltage values V2 and V3 coincide with the voltage value V1, and the control target voltage of the voltage value V1 is the target voltage value V1 ^* , the voltage values V2 and V3 approach the target voltage value V1 ^* . When the voltage value V2 and the voltage value V3 coincide with the target voltage value V1 ^* , the control device 9 switches the control target voltage of the DC / DC converters 42 and 43 to the target voltage value V1 ^* to make the connection device 3 independent. Switch to state. Thereafter, the control device 9 switches the control target voltages of the DC / DC converters 42 and 43 to the target voltage values V2 ^* and V3 ^* , respectively, so that the DC / DC converters 41, 42, and 43 are solar cell modules 21 and 22, respectively. , 23 to perform the maximum power point tracking control of the output power (individual control state).

When switching from the individual control state to the collective control state, the control device 9 switches the control target voltage of the DC / DC converters 42 and 43 to the target voltage value V1 ^* . When the voltage value V2 and the voltage value V3 coincide with the target voltage value V1 ^* , the connection device 3 is switched to the parallel state. Thereafter, the control device 9 switches the control target voltages of the DC / DC converters 42 and 43 to the voltage values V2 and V3, respectively. Since the control target voltage and the control amount are the same (the deviation is zero), the control device 9 is operating the DC / DC converters 42 and 43 but is not in control, and the DC / DC converters 42 and 43 The flowing current decreases. When the current value I2 and the current value I3 become zero, the control device 9 stops the DC / DC converters 42 and 43. Thereafter, the control device 9 performs control so as to perform maximum power point tracking control of the output power of the solar cell module group only by the DC / DC converter 41 (collective control state).

  FIG. 2 is a block diagram showing an internal configuration of the control device 9. The control device 9 includes a total power calculation unit 91, a total power comparison unit 92, a switching determination unit 93, switching units 94 and 95, a current determination unit 96, PI control units 97a, 97b, and 97c, and a PWM signal generation unit 98a, 98b, 98c are provided.

  The total power calculation unit 91 uses 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. The total power (total power value) W output from the battery modules 21, 22, and 23 is calculated and output to the total power comparison unit 92. The total power calculation unit 91 calculates the power value W1 by multiplying the current value I1 and the voltage value V1, calculates the power value W2 by multiplying the current value I2 and the voltage value V2, and calculates the current value I3 and the voltage. The power value W3 is calculated by multiplying the value V3, and the total power value W (= I1 * V1 + I2 * V2 + I3 * V3) is calculated by adding the power values W1, W2, and W3. In the individual control state, the power values W1, W2, and W3 indicate the output power values of the solar cell modules 21, 22, and 23, respectively. On the other hand, in the collective control state, the power value W1 indicates the output power value of the solar cell module group, and the current values I2 and I3 are zero. Therefore, the power values W2 and W3 are also zero.

The total power comparison unit 92 compares the total power value W input from the total power calculation unit 91 with a predetermined value W ₀ set in advance, and compares the comparison results with a switching determination unit 93, switching units 94, 95, And output to the PWM signal generation circuits 98b and 98c. In the present embodiment, the total power comparing unit 92, the total power value W becomes high level in the case of more than the predetermined value W _0, and outputs a signal total power value W becomes low level when less than the predetermined value W ₀ . Note that the method of outputting the comparison result by the total power comparison unit 92 is not limited to this.

The switching determination unit 93 determines switching of the connection device 3 based on the input signal from the total power comparison unit 92, the voltage values V2 and V3 input from the voltage sensors 82 and 83, and the target voltage value V1 ^* , respectively. To do. That is, the switching determination unit 93 has a high level input signal from the total power comparison unit 92 (the total power value W is equal to or greater than the predetermined value W ₀ ), and the voltage value V2 and the voltage value V3 match the target voltage value V1 ^* . In this case, a switching signal for switching the connection device 3 from the parallel state to the independent state is output to the connection device 3. The switching signal is also output to the switching units 94 and 95. Further, the switching determination unit 93 has a low level input signal from the total power comparison unit 92 (the total power value W is less than the predetermined value W ₀ ), and the voltage value V2 and the voltage value V3 coincide with the target voltage value V1 ^* . In this case, a switching signal for switching the connection device 3 from the independent state to the parallel state is output to the connection device 3. The switching signal is also output to the switching units 94 and 95. In this embodiment, the switching determination unit 93 changes from the low level to the high level when the voltage value V2 and the voltage value V3 coincide with the target voltage value V1 ^* when the input signal from the total power comparison unit 92 is at the high level. If the voltage value V2 and the voltage value V3 coincide with the target voltage value V1 ^* when the input signal from the total power comparison unit 92 is at the low level, a signal that changes from the high level to the low level is output as the switching signal. The switching signal output by the switching determination unit 93 is not limited to this.

The switching unit 94 sets the control target voltage of the DC / DC converter 42 based on the signal input from the total power comparison unit 92 and the switching signal input from the switching determination unit 93 to the voltage value V2 input from the voltage sensor 82. The target voltage value V1 ^* and the target voltage value V2 ^* are switched. When the switching signal input from the switching determination unit 93 changes from the low level to the high level (that is, when the connection device 3 is switched from the parallel state to the independent state), the switching unit 94 switches the DC / DC converter 42. control target voltage switched from the voltage value V2 to the target voltage value V1 ^* and then switches from a predetermined time has elapsed after the target voltage value V1 ^* to the target voltage value V2 ^* of. Further, the switching unit 94 changes the DC / DC when the signal input from the total power comparison unit 92 changes from the high level to the low level (that is, when the total power value W becomes less than the predetermined value W ₀ ). When the control target voltage of the DC converter 42 is switched from the target voltage value V2 ^* to the target voltage value V1 ^* , and the switching signal input from the switching determination unit 93 changes from the high level to the low level (that is, the connection device 3 is independent). The control target voltage of the DC / DC converter 42 is switched from the target voltage value V1 ^* to the voltage value V2 after the elapse of a predetermined time from when the state is switched to the parallel state.

The switching unit 95 sets the control target voltage of the DC / DC converter 43 to the voltage value V3 input from the voltage sensor 83 based on the signal input from the total power comparison unit 92 and the switching signal input from the switching determination unit 93. The target voltage value V1 ^* and the target voltage value V3 ^* are switched. When the switching signal input from the switching determination unit 93 changes from the low level to the high level, the switching unit 95 switches the control target voltage of the DC / DC converter 43 from the voltage value V3 to the target voltage value V1 ^* , and then switching from the target voltage value V1 ^* to the target voltage value V3 ^* after a predetermined time has elapsed. The switching unit 95 changes the control target voltage of the DC / DC converter 43 from the target voltage value V3 ^* to the target voltage value V1 ^* when the signal input from the total power comparison unit 92 changes from high level to low level ^. The control target voltage of the DC / DC converter 43 is switched from the target voltage value V1 ^* to the voltage value V3 after a predetermined time has elapsed since the switching signal input from the switching determination unit 93 has changed from the high level to the low level. .

  The current determination unit 96 determines whether or not the current values I2 and I3 respectively input from the current sensors 72 and 73 have become zero, and outputs the determination result to the PWM signal generation units 98b and 98c. . In the present embodiment, the current determination unit 96 outputs a signal that is at a high level when the current values I2 and I3 are both zero, and at a low level in other cases. The signal output from the current determination unit 96 is not limited to this. In addition, the current determination unit 96 outputs a signal that is high when the current value I2 is zero to the PWM signal generation unit 98b, and the signal that is high when the current value I3 is zero is the PWM signal generation unit 98c. May be output.

The PI control unit 97a performs PI control based on the deviation between the voltage value V1 input from the voltage sensor 81 and the target voltage value V1 ^*, and outputs a correction value to the PWM signal generation unit 98a. The PI control unit 97b performs PI control based on the deviation between the voltage value V2 input from the voltage sensor 82 and the control target voltage input from the switching unit 94, and outputs a correction value to the PWM signal generation unit 98b. It is. The PI control unit 97c performs PI control based on the deviation between the voltage value V3 input from the voltage sensor 83 and the control target voltage input from the switching unit 95, and outputs a correction value to the PWM signal generation unit 98c. It is.

  The PWM signal generation unit 98a generates the PWM signal P1 based on the correction value input from the PI control unit 97a and outputs the PWM signal P1 to the DC / DC converter 41. The PWM signal generation unit 98a compares a command value signal based on the correction value input from the PI control unit 97a with a carrier signal (for example, a triangular wave signal) having a predetermined frequency (for example, 4 kHz) generated internally. Thus, the PWM signal P1 is generated. Note that the method of generating the PWM signal is not limited to this. Although not shown, the PWM signal generator 98a starts generating the PWM signal P1 when the grid-connected inverter system 1 becomes operable with the electric power generated by the solar cell modules 21, 22, and 23. When the operation becomes impossible, the generation of the PWM signal P1 is stopped. The DC / DC converter 41 is operated only while the PWM signal P1 is input.

The PWM signal generation unit 98b generates the PWM signal P2 based on the correction value input from the PI control unit 97b and outputs the PWM signal P2 to the DC / DC converter 42. The method of generating the PWM signal is the same as that of the PWM signal generating unit 98a. Further, (i.e. if, the total power value W is equal to or greater than a predetermined value W ₀₎ PWM signal generating unit 98b, when the signal input from the total power comparing unit 92 is changed from the low level to the high level PWM Generation of the signal P2 is started, and generation of the PWM signal P2 when the signal input from the current determination unit 96 changes from low level to high level (that is, when both the current values I2 and I3 become zero). To stop.

  The PWM signal generator 98 c generates a PWM signal P 3 based on the correction value input from the PI controller 97 c and outputs the PWM signal P 3 to the DC / DC converter 43. The method of generating the PWM signal is the same as that of the PWM signal generating unit 98a. The PWM signal generation unit 98c starts generating the PWM signal P3 when the signal input from the total power comparison unit 92 changes from low level to high level, and the signal input from the current determination unit 96 is low. When the level changes from the high level, the generation of the PWM signal P3 is stopped.

  Note that the control device 9 may be realized as an analog circuit or a digital circuit. Further, the processing performed by each unit may be designed by a program, and the computer may function as the control device 9 by executing the program. The program may be recorded on a recording medium and read by a computer.

  Next, the switching process between the individual control state and the collective control state (hereinafter referred to as “control state switching process”) by the control device 9 will be described with reference to FIGS. 3 and 4.

  FIG. 3 is a flowchart for explaining a control state switching process performed by the control device 9. This process is performed at a predetermined timing.

First, the total power value W is equal to or a predetermined value W ₀ or more is determined (S1). When W ≧ W ₀ (S1: YES), it is determined whether or not the individual control state is set (S2). In the individual control state (S2: YES), it is not necessary to switch the control state, so the control state switching process is terminated. On the other hand, in the collective control state (S2: NO), the processing of steps S3 to S8 is performed in order to switch to the individual control state.

  In step S3, the operation of the DC / DC converters 42 and 43 is started (S3). Specifically, the PWM signal generation units 98b and 98c start generating the PWM signals P2 and P3, and output the generated PWM signals P2 and P3 to the DC / DC converters 42 and 43, respectively. The DC / DC converters 42 and 43 start operation when the input of the PWM signals P2 and P3 is started. Since the control target voltages of the DC / DC converters 42 and 43 at this time are the voltage values V2 and V3 input from the voltage sensors 82 and 83, respectively, the DC / DC converters 42 and 43 perform control. It is driven without.

Next, it is determined whether or not the voltage values V2 and V3 input from the voltage sensors 82 and 83 respectively match the target voltage value V1 ^* (S4). If they do not match (S4: NO), the process returns to step S4 and is determined again. That is, the determination is continued until they match. If they match (S4: YES), the control target voltage of the DC / DC converters 42 and 43 is switched from the voltage values V2 and V3 to the target voltage value V1 ^* (S5). Further, the connection device 3 is switched from the parallel state to the independent state (S6). Specifically, a switching signal for switching the connection device 3 from the parallel state to the independent state is output.

Next, it is determined whether or not a predetermined time has elapsed (S7). If it has not elapsed (S7: NO), the process returns to step S7 and the determination is continued until a predetermined time has elapsed. When the time has elapsed (S7: YES), the control target voltages of the DC / DC converters 42 and 43 are switched from the target voltage value V1 ^* to the target voltage values V2 ^* and V3 ^* , respectively (S8), and the control state switching process is completed. The

For W <W ₀ in step S1 (S1: NO), whether or not the collective control state is determined (S9). In the collective control state (S9: YES), there is no need to switch the control state, and the control state switching process is terminated. On the other hand, in the case of the individual control state (S9: NO), processing of steps S10 to S16 is performed in order to switch to the collective control state.

In step S10, the control target voltages of the DC / DC converters 42 and 43 are switched from the target voltage values V2 ^* and V3 ^* to the target voltage value V1 ^* (S10). Next, it is determined whether or not the voltage values V2 and V3 input from the voltage sensors 82 and 83 respectively match the target voltage value V1 ^* (S11). If they do not match (S11: NO), the process returns to step S11 and is determined again. That is, the determination is continued until they match. If they match (S11: YES), the connection device 3 is switched from the independent state to the parallel state (S12). Specifically, a switching signal for switching the connection device 3 from the independent state to the parallel state is output.

Next, it is determined whether or not a predetermined time has elapsed (S13). If it has not elapsed (S13: NO), the process returns to step S13, and the determination is continued until a predetermined time has elapsed. When the time has elapsed (S13: YES), the control target voltages of the DC / DC converters 42 and 43 are switched from the target voltage value V1 ^* to the voltage values V2 and V3, respectively (S14).

  Next, it is determined whether or not the current values I2 and I3 respectively input from the current sensors 72 and 73 have become zero (S15). When at least one is not zero (S15: NO), it returns to step S15 and is discriminated again. That is, discrimination is continued until both become zero. When both become zero (S15: YES), the operation of the DC / DC converters 42 and 43 is stopped (S16), and the control state switching process is ended. Specifically, the operation of the DC / DC converters 42 and 43 is stopped when the PWM signal generation units 98b and 98c stop generating the PWM signals P2 and P3. The DC / DC converters 42 and 43 stop operating when the input of the PWM signals P2 and P3 is stopped.

  FIG. 4 is a time chart for explaining the control state switching process. FIG. 5A is a diagram showing the output power of the solar cell module from sunrise (time t = t0) to sunset (t = t11), the broken line indicates the total power value W, and the solid line is DC / The electric power input into the DC converter 41 is shown. FIG. 2B shows the operating state of the DC / DC converter 41, and FIG. 2C shows the operating state of the DC / DC converters 42 and 43. Both are indicated as “ON” during operation and “OFF” during stoppage. FIG. 4D shows switching of the control target voltage of the DC / DC converter 42, and FIG. 4E shows the voltage value of the input voltage of the DC / DC converter 42 (that is, the voltage value detected by the voltage sensor 82) V2. (Hereinafter referred to as “input voltage value V2”). The switching of the control target voltage and the input voltage value of the DC / DC converter 43 are the same. FIG. 5F shows the state of the connection device 3.

  After the sunrise (time t = t0), when the grid-connected inverter system 1 becomes operable with the power generated by the solar cell modules 21, 22, and 23 (t = t1), the DC / DC converter 41 is activated. (Refer to FIG. 2B). Note that the connection device 3 is in a parallel state by switching from the previous individual control state to the collective control state (for example, switching before sunset of the previous day). After the DC / DC converter 41 is activated, until the DC / DC converters 42 and 43 are activated (t = t1 to t2), the output power of the solar cell modules 21, 22, and 23 is collected and the DC / DC converter 41 is activated. It is a collective control state controlled by.

When the total power value (DC / DC converter power is input to 41) W is turned by more than a predetermined value W ₀ increases (t = t2), DC / DC converter 43 is activated (FIG. (See (c)). The control target voltage of the DC / DC converter 42 at this time is the voltage value V2 input from the voltage sensor 82 (see FIG. 4D). After that, when the input voltage value V2 of the DC / DC converter 42 matches the target voltage value V1 ^* (see (e) t = t3 in the same figure), the connecting device 3 is switched from the parallel state to the independent state (the same figure). (Refer to (f)), the control target voltage of the DC / DC converter 42 is switched from the voltage value V2 to the target voltage value V1 ^* (see (d) in the figure). Thereafter, after a predetermined time has elapsed (t = t4), the control target voltage of the DC / DC converter 42 is switched from the target voltage value V1 ^* to the target voltage value V2 ^* (see FIG. 4D). Thereby, it will be in the individual control state where the output electric power of each solar cell module 21,22,23 is controlled by DC / DC converter 41,42,43, respectively.

When the total power value W decreases near sunset and becomes less than the predetermined value W ₀ (t = t6), the control target voltage of the DC / DC converter 42 changes from the target voltage value V2 ^* to the target voltage value V1 ^*. (See FIG. 4D). After that, when the input voltage value V2 of the DC / DC converter 42 coincides with the target voltage value V1 ^* (see (e) t = t7 in the figure), the connecting device 3 is switched from the independent state to the parallel state ( (See (f) in the figure). Thereafter, after a lapse of a predetermined time (t = t8), the control target voltage of the DC / DC converter 42 is switched from the target voltage value V1 ^* to the voltage value V2 (see FIG. 4D). As a result, the input current values I2 and I3 of the DC / DC converters 42 and 43 are reduced, so that the power input to the DC / DC converters 42 and 43 is reduced ((a) t = t8 to t9). reference). When both of the input current values I2 and I3 become zero (t = t9), the DC / DC converters 42 and 43 are stopped (see (c) in the figure).

  Thereafter, when the grid-connected inverter system 1 becomes inoperable with the electric power generated by the solar cell modules 21, 22, and 23 (t = t10), the DC / DC converter 41 is stopped ((b) in FIG. )reference). From the time when the DC / DC converters 42 and 43 are stopped to the time when the DC / DC converter 41 is stopped (t = t9 to t10), the output power of the solar cell modules 21, 22, and 23 is collected and the DC / DC converter is collected. 41 is a collective control state controlled at 41.

In this embodiment, a transient state when switching from the collective control state to the individual control state (t = t2 to t4 in FIG. 4), and a transient state when switching from the individual control state to the collective control state (t in FIG. 4). The control target voltage of the DC / DC converter 42 at t6 to t9) is set to the voltage value V2 or the target voltage value V1 ^* input from the voltage sensor 82 (see FIG. 4D). While the control target voltage is set to the target voltage value V1 ^* , the DC / DC converter 42 performs the same control as the DC / DC converter 41. Further, while the control target voltage is set to the voltage value V2, the DC / DC converter 42 is not controlling. Therefore, interference of control by the DC / DC converter 41 and the DC / DC converter 42 does not occur. Further, since the control target voltage of the DC / DC converter 43 at the time of transition is the voltage value V3 or the target voltage value V1 ^* input from the voltage sensor 83, the DC / DC converter 43, the DC / DC converter 41, and the DC / Interference of control by the DC converter 42 does not occur. Thereby, the control interference by each DC / DC converter when switching between the individual control state and the collective control state can be prevented.

In this embodiment, the control target voltage of the DC / DC converters 42 and 43 is switched from the target voltage value V1 ^* to the voltage values V2 and V3, and the input current values I2 and I3 of the DC / DC converters 42 and 43 are changed. The operation of the DC / DC converters 42 and 43 is stopped after both become zero. Therefore, the power input to the DC / DC converter 41 does not change when the DC / DC converters 42 and 43 are stopped. Therefore, there is no problem that the maximum power point that is tracked in the maximum power point tracking control by the DC / DC converter 41 changes suddenly.

In the above embodiment, when the input voltage value V2 of the DC / DC converter 42 matches the target voltage value V1 ^* (see FIG. 4 (e) t = t3), the connecting device 3 is independent from the parallel state. (See (f) in the figure) and the control target voltage of the DC / DC converter 42 is switched from the voltage value V2 to the target voltage value V1 ^* (see (d) in the figure). Not limited. Switching the timing to separate state of the connection device 3, and switching timing of the target voltage value V1 ^* of the control target voltage of the DC / DC converter 42, respectively, match the input voltage value V2 is the target voltage value V1 ^* The time from when the control target voltage is switched to the target voltage value V2 ^* (t = t3 to t4) may be used. Further, after the timing of switching the connection device 3 to the independent state, the control target voltage of the DC / DC converter 42 is directly changed from the voltage value V2 to the target voltage value V2 ^* (without switching to the target voltage value V1 ^* ). You may make it switch.

Further, in the above embodiment, when the input voltage value V2 of the DC / DC converter 42 matches the target voltage value V1 ^* (see FIG. 4 (e) t = t7), the connecting device 3 is changed from the independent state to the parallel state. However, the present invention is not limited to this case. The switching timing of the connection device 3 to the parallel state is set to the time from when the input voltage value V2 matches the target voltage value V1 ^* to when the control target voltage is switched to the voltage value V2 (t = t7 to t8). Good. Further, the timing for switching the control target voltage from the target voltage value V1 ^* to the voltage value V2 may be after the input voltage value V2 coincides with the target voltage value V1 ^* (t = t7).

  In the above embodiment, the case where the operation of the DC / DC converter 42 is stopped when the input current value I2 becomes zero (t = t9) (see (c) in the figure) has been described. Not limited to. The timing for stopping the DC / DC converter 42 may be after the input current value I2 becomes zero (t = t9). In addition, even when the timing at which the DC / DC converter 42 is stopped is before the input current value I2 becomes zero, it is possible to prevent the control interference when switching from the individual control state to the collective control state. .

In the above embodiment, the threshold value for switching between the individual control state and the collective control state is set to one predetermined value W ₀ , but is not limited thereto. For example, a threshold value W ₁ for switching from the collective control state to the individual control state and a threshold value W ₂ (W ₁ > W ₂ ) for switching from the individual control state to the collective control state are set, and hysteresis is set. By providing, chattering may be suppressed. Further, the present invention is not limited to the case where the total power value is compared with the threshold value, and the output power of one solar cell module (for example, the solar cell module 21) may be compared with the threshold value.

  In the said embodiment, although the case where there were three solar cell modules and DC / DC converters was demonstrated, it is not restricted to this. The present invention can be applied to the case where the number of solar cell modules and DC / DC converters is two or four or more. Further, the present invention can be applied even when the individual control state and the collective control state are switched in stages. For example, in the grid-connected inverter system 1 shown in FIG. 1, when the total power value becomes equal to or higher than a first predetermined value, the DC / DC converter 43 is activated to open the electromagnetic contactor 32, and then the solar cell When the DC / DC converter 42 is activated to open the electromagnetic contactor 31 when the total value of the output power of the module 21 and the output power of the solar cell module 22 exceeds the second predetermined value (the solar cell module 21 When the total value of the output power and the output power of the solar cell module 22 becomes less than the second predetermined value, the electromagnetic contactor 31 is closed and the DC / DC converter 42 is stopped, and then the total power value is the first value. The present invention can be applied even when the electromagnetic contactor 32 is closed and the DC / DC converter 43 is stopped when it becomes less than the predetermined value.

  In the above embodiment, the case where the power output from the three DC / DC converters 41, 42, 43 is input to one inverter 5 is described, but the present invention is not limited to this. For example, as shown in FIG. 5, when three inverters 51, 52, 53 are provided and the power output from each DC / DC converter 41, 42, 43 is input to the inverters 51, 52, 53, respectively. The present invention can be applied. In this case, the inverters 52 and 53 are also started when the DC / DC converters 42 and 43 are started, and the operation of the inverters 52 and 53 is also stopped when the operation of the DC / DC converters 42 and 43 is stopped. do it. In the grid-connected inverter system 1 ′ shown in FIG. 5, the control device 9 also serves as a control device for the inverters 51, 52, and 53. Further, in FIG. 5, description of the current sensors 71, 72, 73 and the voltage sensors 81, 82, 83 is omitted.

  Further, as shown in FIG. 6, three inverters 51, 52, 53 are provided without providing the DC / DC converters 41, 42, 43, and the solar cell modules 21, 22, 22 are provided by the inverters 51, 52, 53. The present invention can also be applied to a case where the output power of 23 is subjected to maximum power point tracking control. In this case, the PWM signals P1, P2, and P3 generated by the control device 9 may be input to the inverters 51, 52, and 53 for control. In the grid-connected inverter system 1 ″ shown in FIG. 6, a transformer 10 for voltage conversion is provided instead of the DC / DC converter. In FIG. 6, current sensors 71, 72, 73 and voltage sensors 81, 82, 83 are not shown.

  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 power 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 control device of the power conversion 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 Solar cell module (first power supply)
22, 23 Solar cell module (second power supply)
3 connection device 41 DC / DC converter (first power conversion device)
42, 43 DC / DC converter (second power converter)
DESCRIPTION OF SYMBOLS 5 Inverter 6 Electric power system 71,72,73 Current sensor 81,82,83 Voltage sensor 9 Control apparatus 91 Total electric power calculation part (calculation means)
92 Total power comparator (discriminating means)
93 switching determination unit 94,95 switching unit 96 current determination unit 97a, 97b, 97c PI control unit 98a, 98b, 98c PWM signal generation unit

Claims (10)

A first power converter, a first power converter connected to the output end of the first power supply, a second power supply, and a second connected to the output end of the second power supply. The power converter, the output end of the first power supply device and the output end of the second power supply device are not connected to each other, and the output end of the first power supply device and the second power supply device The present invention is applied to a grid-connected inverter system including a connection device that connects the output terminals to each other in any of the parallel states, and the power output by the first power supply device and the second power supply device is maximized. A control device for controlling the operation of each of the power converters,
When operating the first power converter and the second power converter when the connecting device is in the parallel state, the control by the second power converter is not performed, or the first A control device, wherein a control target voltage of one power conversion device is set as a control target voltage of the second power conversion device. From the collective control state in which only the first power conversion device is operated and the connection device is in the parallel state, the first power conversion device and the second power conversion device are operated, and the connection device is When switching to the individual control state in the independent state, the operation of the second power conversion device is started without performing control by the second power conversion device, and the first connected in parallel After the output voltage of the power supply device and the second power supply device becomes the control target voltage of the first power conversion device, the control target voltage of the first power conversion device is controlled by the second power conversion device. Set as a target voltage and start control by the second power converter,
When switching from the individual control state to the collective control state, a control target voltage of the first power conversion device is set as a control target voltage of the second power conversion device, and control is performed by the second power conversion device. And after the output voltage of the second power supply device reaches the control target voltage of the first power converter, the control by the second power converter is stopped.
The control device according to claim 1.   When switching from the collective control state to the individual control state, when the output voltages of the first power supply device and the second power supply device connected in parallel become the control target voltage of the first power conversion device The control device according to claim 2, wherein the connection device is switched to the independent state.   When switching from the individual control state to the collective control state, when the output voltage of the second power supply device becomes the control target voltage of the first power converter, the connection device is switched to the parallel state. The control device according to claim 2 or 3.   When switching from the individual control state to the collective control state, when the current flowing through the second power converter becomes zero after the control by the second power converter is not performed, the first The control device according to any one of claims 2 to 4, wherein operation of the power converter 2 is stopped. Calculating means for calculating a total value of output power of the first power supply device and the second power supply device;
Determining means for determining whether the total value is equal to or greater than a predetermined value;
Further comprising
When the total value is determined to be greater than or equal to the predetermined value by the determination unit in the collective control state, the determination unit switches from the collective control state to the individual control state, and the determination unit is in the individual control state. When the total value is determined to be less than the predetermined value by switching from the individual control state to the collective control state,
The control device according to claim 2.   The control device according to claim 1, wherein each of the first power conversion device and the second power conversion device includes a DC / DC converter.   The control device according to claim 1, wherein each of the first power conversion device and the second power conversion device includes an inverter.   The control device according to claim 1, wherein each of the first power supply device and the second power supply device includes a solar battery.   The first power supply device, the first power conversion device, the second power supply device, the second power conversion device, the connection device, and the connection device according to any one of claims 1 to 9. Grid-connected inverter system comprising a control device.

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