JP2014128164A - Power conditioner and photovoltaic power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photovoltaic power generation system with an energy storage function, configured so that DC power output in a reverse direction by a bidirectional inverter is supplied to a power storage section through a built-in converter without necessity for addition of a complicated additional circuit to a power conditioner.SOLUTION: A built-in converter 8 of a power conditioner 3 is comprised of a non-insulation type step-up chopper circuit, and the power conditioner includes switch means 16 such as a relay for shortening a step-up diode 13 thereof and is configured to control the operation of the switch means 16, interlocking with a control mode of a bidirectional inverter.

Description

  The present invention relates to a power conditioner that can be suitably used in a power generation system in which a storage battery is connected in parallel to a solar power generation panel, and a solar power generation system including the power conditioner.

  This type of conventional power conditioner is a non-insulated DC / DC for boosting and stabilizing DC generated power supplied from a photovoltaic power generation panel, for example, as disclosed in Patent Document 1 below. The converter includes a DC / AC inverter that converts the DC power output from the converter into AC power linked to the system power and outputs the AC power. Moreover, in the power conditioner described in Patent Document 1, a power storage unit is connected to a DC link portion between the converter and the inverter. This power storage unit includes a storage battery and a charge / discharge controller (bidirectional converter) for charging / discharging the storage battery, and can charge the storage battery with surplus power generated by the photovoltaic power generation panel and Power can be supplied from the storage battery when there is a shortage (such as at night).

  The voltage of the DC link unit is preferably controlled so as to be a predetermined target voltage calculated based on the maximum voltage of the system power in order to stabilize the output power of the inverter. -It is generally known that it is preferable to perform maximum power point tracking control as input / output control of a power conditioner based on current characteristics (VI characteristics). The voltage corresponding to the maximum power point of the output of the photovoltaic panel becomes the input voltage of the converter, and accordingly, the fluctuation range of the output voltage of the converter is expanded.

  As a converter that can avoid such a problem, for example, Patent Document 2 discloses a first boost converter that boosts and outputs the generated power of a photovoltaic power generation panel while performing maximum power point tracking control, and the first booster. A configuration is disclosed in which a second boost converter that further boosts the DC power output from the converter and outputs it to an inverter is provided, and a storage battery is connected between the first and second boost converters. In the power generation system described in Patent Document 2, the first boost converter can perform input / output control so that the output power of the photovoltaic power generation panel is maximized, and can charge the storage battery using the surplus generated power. is there. In addition, when the power load is large, the second boost converter can control the DC link voltage to the optimum voltage while supplying power from the storage battery in addition to the generated power, stabilizing the output power of the inverter Is intended. In Example 8 of Patent Document 2 (see the paragraph numbers 0035 and 0036 of the specification and FIG. 10), the second boost converter is configured as a bidirectional converter using a half bridge, and a capacitor that configures the DC link unit is provided. By using a small-capacity film capacitor, when the household electrical appliance connected to the AC output is a load that generates regenerative power such as a motor, the input voltage of the inverter does not exceed the withstand voltage of the switching elements that constitute the inverter. (That is, based on the voltage across the film capacitor), a configuration is disclosed in which the regenerative power generated can be regenerated in the storage battery by turning on the high-side switching element of the half bridge.

JP 2012-161190 A JP 2003-67065 A JP 2009-33800 A

  On the other hand, in recent years, to cope with the problem of tight power supply during the daytime, nighttime electricity charges have been set to be cheaper to distribute power demand at nighttime, and such nighttime electricity is stored and used during the daytime. Various power storage systems that can be used have been developed. For example, in Patent Document 3, an inverter is configured by an H bridge circuit (voltage-type bridge inverter), and commercial grid power (AC power) is used by using the H bridge circuit and an LC filter provided on the output side thereof. Has been disclosed in which a switching element of an H-bridge circuit is controlled so as to perform a conversion operation in a reverse direction to DC power, and a storage battery is charged using DC power obtained by converting such commercial grid power. The inverter described in Patent Document 3 is mainly related to battery charging of a plug-in hybrid vehicle, and is considered to have been developed to solve an important problem in the automobile industry such as miniaturization and weight reduction of the vehicle.

  On the other hand, in the solar power generation system described in Patent Document 2 installed in a house, miniaturization and weight reduction are not required as much as an automobile, and users who desire a power storage system that stores night commercial power On the other hand, a dedicated power storage unit was provided separately from the solar power generation system.

  However, as solar power generation systems become more widespread, more advanced functions and diversification are required, and the power generation function of conventional solar power generation systems is also being demanded. A step-up chopper circuit is preferably used as the DC / DC converter built in the conditioner. Due to the presence of the step-up diode of the step-up chopper circuit, current cannot flow in the reverse direction, and the storage battery is charged with commercial power. In order to achieve this, it is necessary to provide a separate AC / DC converter for charging, resulting in a complicated circuit configuration and increased cost.

  In addition, even if the inverter of the power generation system described in Patent Document 2 is operated as in the technique described in Patent Document 3, regenerative power is regenerated in the storage battery so as not to exceed the withstand voltage of the switching elements constituting the inverter. In addition, since the switching element on the high side of the half bridge of the second boost converter is controlled to be turned on / off based on the voltage across the film capacitor, commercial power is converted back to DC power by an inverter. At this time, it is not guaranteed that the switching element of the boost converter is turned on.

  Therefore, the present invention provides a power conditioner that converts DC power from a power source formed by connecting a photovoltaic power generation unit and a power storage unit in parallel to AC power connected to the grid without providing a complicated additional circuit. It aims at making the storage battery connected to the input side of the power conditioner chargeable using system electric power.

  In order to achieve the above object, the present invention takes the following technical means.

  That is, the present invention provides a boost chopper circuit for boosting DC power input from a power source formed by connecting a solar power generation unit and a power storage unit in parallel to a predetermined voltage corresponding to the maximum voltage of the system power, and the boost A voltage source bridge inverter for converting the DC power boosted by the chopper circuit into AC power linked to the system power and outputting it to the system side, and a controller for controlling the boost chopper circuit and the inverter, A step-up chopper circuit includes: Switch means for opening and closing the short circuit by control from the control unit, and the inverter is a bidirectional inverter. In addition, as a control mode of the inverter by the control unit, a power output control mode for converting the DC power boosted by the boost chopper circuit into AC power linked to the system power by the inverter and outputting the AC power to the system side; A charge control mode is provided in which system power supplied from the side is converted to DC power by the inverter and supplied to the power storage unit, and the control unit is configured to always close the short circuit in the charge control mode. It is comprised so that it may control (claim 1).

  According to the power conditioner of the present invention, since the boost chopper circuit as a DC / DC converter is built in and the power storage unit is connected to the input side (solar power generation unit side), the output side of the boost chopper circuit The voltage can be stabilized. On the other hand, since the voltage on the input side of the step-up chopper circuit fluctuates relatively greatly depending on the power generation state in the photovoltaic power generation unit, the power storage unit is connected to the storage battery via a charge / discharge controller mainly composed of a bidirectional DC / DC converter. As the configuration connected to the input side of the converter, it is preferable to widen the allowable voltage range of the input / output part of the charge / discharge controller, so that the voltage across the storage battery can be kept low, and the internal impedance is kept low. It is also possible to reduce the loss. In charge control mode, the DC current can flow in the reverse direction through the boost rectifier of the boost chopper circuit by closing the short circuit, and the DC current flows with the boost reactor magnetically saturated. At this time, since the high frequency switching of the switching element is not performed, there is almost no power loss due to switching, and the system power can be efficiently supplied to the power storage unit to be charged. In addition, since a complicated additional circuit is not required, it can be a simple configuration while having a power storage unit charging function using system power, and can be shared with a power generation system that does not have a power storage unit. Can be configured.

  In the power conditioner of the present invention, the control unit may be configured to acquire information related to a charging state of the power storage unit and switch the control mode based on the information (claim). 2). According to this, for example, the information regarding the charging state is acquired by communication with the control unit of the power storage unit, and the charging control mode can be ended when the charging state is reached. The present invention is not particularly limited as to what timing and conditions are used for switching control.

  Moreover, this invention is a photovoltaic power generation system provided with the said power conditioner, the said photovoltaic power generation part, and the said electrical storage part, Comprising: The said photovoltaic power generation part is a plurality of photovoltaic power generation panels, and this plurality A boosting junction box that boosts the power generation output of the photovoltaic power generation panel by collecting, and the boosting junction box has an input / output power control function by maximum power point tracking control, The input / output unit of the power storage unit is connected (Claim 3).

  According to the photovoltaic power generation system of the present invention, the voltage range of the input / output unit of the power storage unit is set to a predetermined value such as 280 to 320 V, for example, by connecting the power storage unit in parallel to the connection portion between the booster junction box and the power conditioner. By controlling the switching elements constituting the inverter so that the voltage of the DC output power to the power storage unit side in the charge control mode of the inverter is also in the above voltage range, the conventional power storage It becomes possible to charge the power storage unit using the system power with the charge / discharge circuit configuration of the unit.

  In the photovoltaic power generation system of the present invention, the power storage unit includes a storage battery and charge / discharge control means for controlling charge / discharge of the storage battery, the charge / discharge control means and the control unit of the power conditioner, Are communicably connected (claim 4). According to this, it is possible to supply information related to the current control mode to the charge / discharge control means of the power storage unit, and to perform charge / discharge control according to the control mode quickly and accurately, and the charge / discharge control means Thus, it is possible to supply information related to the charging state to the control unit of the power conditioner so that the control mode can be accurately switched according to the charging state.

  As described above, according to the power conditioner of the first aspect of the present invention, the step-up chopper circuit as the DC / DC converter is incorporated, and the power storage unit is connected to the input side (the photovoltaic power generation unit side). Therefore, the voltage on the output side of the boost chopper circuit can be stabilized. On the other hand, since the voltage on the input side of the step-up chopper circuit fluctuates relatively greatly depending on the power generation state in the photovoltaic power generation unit, the power storage unit is connected to the storage battery via a charge / discharge controller mainly composed of a bidirectional DC / DC converter. As the configuration connected to the input side of the converter, it is preferable to widen the allowable voltage range of the input / output part of the charge / discharge controller, so that the voltage across the storage battery can be kept low, and the internal impedance is kept low. It is also possible to reduce the loss. In charge control mode, the DC current can flow in the reverse direction through the boost rectifier of the boost chopper circuit by closing the short circuit, and the DC current flows with the boost reactor magnetically saturated. At this time, since the high frequency switching of the switching element is not performed, there is almost no power loss due to switching, and the system power can be efficiently supplied to the power storage unit to be charged. In addition, since a complicated additional circuit is not required, it can be a simple configuration while having a power storage unit charging function using system power, and can be shared with a power generation system that does not have a power storage unit. Can be configured.

  Further, according to the power conditioner according to claim 2 of the present invention, for example, the information on the charging state is acquired through communication with the control means of the power storage unit, and the charging control mode is terminated when the charging state is reached. can do.

  Moreover, according to the photovoltaic power generation system according to claim 3 of the present invention, the voltage range of the input / output unit of the power storage unit can be set, for example, by connecting the power storage unit in parallel to the connection unit between the step-up connection box and the power conditioner. The switching elements constituting the inverter are controlled so that the voltage range of 280 to 320 V or the like can be set to a predetermined voltage range such as 280 to 320 V and the voltage of the DC output power to the power storage unit side in the charging control mode of the inverter is also in the voltage range Thus, it is possible to charge the power storage unit using the system power with the conventional charge / discharge circuit configuration of the power storage unit.

  Moreover, according to the photovoltaic power generation system according to claim 4 of the present invention, the information on the current control mode is supplied to the charge / discharge control means of the power storage unit, and the charge / discharge control corresponding to the control mode is quickly and accurately performed. In addition to being able to be performed, information related to the charging state is supplied from the charging / discharging control means to the control unit of the power conditioner, so that the control mode can be switched appropriately according to the charging state.

It is a schematic block block diagram of the solar energy power generation system containing the power conditioner which concerns on one Embodiment of this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 shows a photovoltaic power generation system with a power storage function according to an embodiment of the present invention. The power generation system includes a power source formed by connecting a solar power generation unit 1 and a power storage unit 2 in parallel, and the power source. It is mainly composed of a power conditioner 3 that converts the supplied DC power into AC power linked to commercial power and outputs the AC power.

  The solar power generation unit 1 includes a solar power generation panel 4 and a booster connection box 5. A plurality of photovoltaic power generation panels 4 are installed on the roof of a building, and the outputs of the plurality of photovoltaic power generation panels 4 are aggregated and boosted by a booster connection box 5 and output to the power conditioner 3 side. The step-up junction box 5 includes a DC / DC converter composed of a step-up chopper circuit and a control circuit (not shown) for controlling a switching element of the step-up chopper, and the generated power of the photovoltaic power generation panel 4 is reduced to, for example, about It is controlled by the control circuit so as to boost the voltage to 280V to 320V and output it. The control circuit is configured to perform maximum power point tracking control (MPPT control) so that the output voltage of the photovoltaic power generation panel 4 becomes a voltage corresponding to the maximum power point in the VI characteristic of the solar cell. be able to. In addition, although the maximum power point tracking control may be performed in the control unit of the power conditioner 3 to be described later, the control unit of the power conditioner 3 is equipped with the maximum power point tracking control function in the boosting junction box 5. General-purpose input / output power control only needs to be performed, and it is not necessary to change the control mode depending on whether the power source is a storage battery or a solar battery, thereby simplifying the control configuration and enhancing the versatility of the power conditioner 3 There is a merit that you can.

  The power storage unit 2 includes a storage battery 6 and a charge / discharge controller 7 that controls charging / discharging of the storage battery 6, and an input / output unit of the charge / discharge controller 7 is connected to a connection part between the step-up connection box 5 and the converter 3. In the charging operation, DC power is input from the input / output unit, and the charge / discharge controller 7 steps down the voltage and supplies it to the storage battery 6, and in the discharging operation, the power required for the storage battery 6 is output. Thus, the voltage of the storage battery 6 is boosted and output to the input / output unit. The charge / discharge controller 7 also has a function of prohibiting input / output of the storage battery 6. Such a charge / discharge controller 7 can be mainly constituted by a bidirectional DC / DC converter constituted by a half-bridge circuit and the like, and a control circuit (charge / discharge control means) for controlling a switching element of the converter, The control circuit also has a function of detecting the state of charge of the storage battery 6. The charge / discharge controller 7 can also be controlled by a control circuit built in the step-up connection box or a control unit built in the power conditioner 3.

  The power conditioner 3 includes a DC / DC converter 8 including a boost chopper circuit for boosting DC power input from a power source to a predetermined voltage (for example, 380 V) corresponding to the maximum voltage of the system power, and boosting by the converter 8 A voltage source bridge inverter 9 (DC / AC inverter) for converting the direct current power into AC power connected to the system power and outputting it to the system side, and an LC low-pass filter provided on the output side of the inverter 9 10 and a control unit 11 that controls the converter 8 and the inverter 9. The control unit is mainly configured by a microcomputer, and each control function is implemented as a control program, but may be configured by a dedicated circuit corresponding to each control function.

  The step-up chopper circuit constituting the converter 8 includes a step-up reactor 12, a step-up rectifier 13 that prevents backflow of current during step-up operation to the step-up reactor 12, and an IGBT or the like that controls stored energy of the step-up reactor 12. An element 17 and a smoothing capacitor 15 constituting a DC link unit provided on the cathode side of the rectifier 13 are provided. The control unit 11 performs input / output power control of the converter 8 by PWM control of the switching element 17. It is configured as follows.

  Further, a short circuit 14 for short-circuiting the anode side and the cathode side of the rectifier 13 is provided, and a switch means 16 for opening and closing the short circuit 14 is provided. Is configured to do. As the switch means 16, a relay with almost no power loss can be preferably used, but an appropriate semiconductor switching element such as IGBT or FET may be used. It is also possible to realize the functions of the rectifier 13 and the switch means 16 with a single semiconductor device.

  The inverter 9 functions as a bidirectional inverter. When power is output to the system, the DC power from the DC link unit is converted into AC power by PWM control or PAM control. Is converted into a sine wave and output to the system side. On the other hand, when the storage battery is charged with system power, the coil of the low-pass filter 10 functions as a boosting reactor, and the switching element such as an IGBT that constitutes an inverter bridge so as to function as a boosting circuit by the coil and the inverter bridge (H bridge). Is to control. The inverter 9 in the present embodiment is a full-bridge voltage source bridge inverter, and controls the output current by performing so-called voltage source current control (current mode control).

  More specifically, as a control mode of the inverter 9 by the control unit 11, the inverter 9 converts the DC power boosted by the converter 8 into AC power linked to the system power by the inverter 9 and outputs it to the system side. There are a power output control mode for controlling the switching element and a charge control mode for controlling the switching element of the inverter 9 so that the system power supplied from the system side is rectified and boosted to DC power by the inverter 9 and supplied to the power storage unit 2. Is provided. Further, the control unit 11 controls the switch means 16 so as to always close the short circuit 14 in the charge control mode, while controlling the switch means 16 so as to always open the short circuit 14 in the power output control mode. The switching element 17 is always turned off.

  Note that the voltage of the DC link unit 15 in the charge control mode may be lower than the voltage of the DC link unit 15 when the generated power is output. That is, in the generated power output control mode, the target voltage of the DC link unit 15 is determined based on a value obtained by adding a margin to the maximum value of the system voltage. On the other hand, in the charge control mode, the storage battery 6 only needs to be charged via the charge / discharge controller 7, and even if a voltage difference occurs to some extent, the charge / discharge controller 7 can handle it. Each constant such as is designed with priority given to the efficiency in the power output control mode, and the voltage value that can be efficiently converted from the system power using such a circuit is set as the target voltage of the DC link unit 15 in the charge control mode. it can.

  The DC power output from the inverter 9 toward the power storage unit 2 in the charge control mode is supplied to the power storage unit 2 through the short circuit 14 and the step-up reactor 12 of the converter 8 with almost no power loss. Used for charging. As described above, according to the power conditioner 3 of the present embodiment, although the boost chopper circuit 8 is built in, a separate AC is provided by passing through the boost chopper circuit 8 during reverse power conversion from the system. The storage battery 6 can be charged using system power without providing a DC converter, and the cost can be reduced by simplifying the circuit configuration.

Further, the control unit 11 of the converter 3 is communicatively connected to the charge / discharge controller 7 of the power storage unit 2 and transmits / receives various information detected or calculated by the control unit 11 and the charge / discharge controller 7 to each other, and is exemplified below. Various operation controls can be performed.
1. When peak power consumption is cut during the daytime using late-night power (a) If the amount of power generation is greater than the power consumption, the control unit 11 of the power conditioner 3 sends the charge / discharge controller 7 to the output prohibition from the power storage unit 2 The power is supplied from the photovoltaic power generation panel 4 while the output from the power storage unit 2 is turned off, and the surplus power is used for selling power or charging the storage battery 6. Moreover, if it will be in a full charge state, the charge by the charge / discharge controller 7 will be stopped, and all surplus electric power will be sold.
(B) If the power generation amount is smaller than the power consumption, the control unit 11 of the power conditioner 3 controls the charge / discharge controller 7 to discharge and output the stored power, and the power is also supplied from the power storage unit 2. Control to reduce electricity as much as possible.
(C) When the operation of the power conditioner 3 is stopped due to a power failure or the like, the charge / discharge controller 7 autonomously determines that the operation of the power conditioner 3 is stopped by detecting that communication is impossible, and uses the generated power to store the battery. To charge. Even during a power failure, the step-up junction box 5 can be configured to operate with the generated power, and the charge / discharge controller 7 can be configured to operate with the stored power of the storage battery 6. The storage battery 6 can be charged using electric power. Moreover, if it will be in a full charge state, the charge by the charge / discharge controller 7 will be stopped, and the boost output control by a boost connection box will also be stopped.
(D) In the time zone when the output of the photovoltaic power generation panel 4 is stopped at night but the power consumption is large, the control unit 11 of the power conditioner 3 performs command control to discharge and output the stored power to the charge / discharge controller 7, The power consumption is supplied from the storage battery 6 and only the shortage is purchased from the commercial power system.
(E) At the midnight charge time zone, the power conditioner 3 switches to the charge control mode, closes the switch means 16 of the short circuit 14, and instructs the charge / discharge controller 7 to perform a charging operation. It should be noted that the charging time zone can be controlled by the timer function on the power conditioner 3 side so as to correspond to the contract status of each home. When the full charge state is reached, the charge / discharge controller 7 stops charging and transmits a command signal instructing the controller 11 to be fully charged, and the control unit 11 receiving the command signal switches the charge control mode. Stop and switch to the power output control mode, or stop the operation of the power conditioner 3 until a predetermined time (for example, end time of midnight power time zone, sunrise time, etc.).

2. When a storage battery is used for autonomous operation during a power failure (a) During autonomous operation, the storage battery is discharged according to the amount of power generation.

  As described above, according to the power generation system according to the present embodiment, since the power storage unit 2 is arranged on the DC power side, the power conditioner 3 and the power storage unit 7 share the DC-AC conversion circuit at the time of charging and discharging. In addition, AC / DC conversion is not required when charging from the solar power generation unit 1, so that there is no loss. Further, in the event of a power failure, the autonomous operation function of the power conditioner 3 can be stably operated with the assistance from the power storage unit 2. In addition, since the charging / discharging timing of the power storage unit 2 is controlled on the power conditioner 3 side, adjustment of which power is supplied to the load in accordance with the power storage amount of the storage battery 6 or the power generation amount of the solar power generation panel 4 Becomes easier. Furthermore, since the charging / discharging timing of the power storage unit 2 is controlled by the timer function on the power conditioner 3 side, peak cut of power consumption during the daytime can be performed using midnight power.

  The present invention is not limited to the above-described embodiment, and the design can be changed as appropriate.

DESCRIPTION OF SYMBOLS 1 Solar power generation part 2 Power storage part 3 Power conditioner 4 Solar power generation panel 5 Boosting connection box 6 Storage battery 7 Charge / discharge controller (charge / discharge control means)
8 Converter (Boost chopper circuit)
9 Inverter 11 Control unit 12 Boosting reactor 13 Boosting rectifier

Claims (4)

A boost chopper circuit for boosting DC power input from a power source formed by connecting a photovoltaic power generation unit and a power storage unit in parallel to a predetermined voltage corresponding to the maximum voltage of the system power, and boosted by the boost chopper circuit A voltage source bridge inverter for converting DC power into AC power linked to system power and outputting it to the system side, and a boost chopper circuit and a control unit for controlling the inverter. In a power conditioner having a reactor and a boosting rectifier that prevents backflow of current during boosting operation to the boosting reactor,
A short circuit that short-circuits the anode side and the cathode side of the rectifier; and switch means that opens and closes the short circuit under control from the control unit, wherein the inverter is a bidirectional inverter, and the control unit As an inverter control mode, a power output control mode in which DC power boosted by a boost chopper circuit is converted into AC power linked to system power by the inverter and output to the system side, and system power supplied from the system side Is provided with a charge control mode in which the inverter is converted into DC power and supplied to the power storage unit, and the control unit is configured to control the switch means so as to always close the short circuit in the charge control mode. A power conditioner characterized by   The power conditioner according to claim 1, wherein the control unit is configured to acquire information related to a charging state of the power storage unit and switch the control mode based on the information. Na.   A photovoltaic power generation system comprising the power conditioner according to claim 1, the photovoltaic power generation unit, and the power storage unit, wherein the photovoltaic power generation unit includes a plurality of photovoltaic power generation panels, A step-up connection box that collects and boosts the power generation outputs of a plurality of photovoltaic power generation panels, and the step-up connection box has an input / output power control function by maximum power point tracking control; A photovoltaic power generation system, wherein an input / output unit of the power storage unit is connected.   4. The photovoltaic power generation system according to claim 3, wherein the power storage unit includes a storage battery and charge / discharge control means for controlling charge / discharge of the storage battery, and controls the charge / discharge control means and the power conditioner. The photovoltaic power generation system characterized by being connected so that communication is possible.

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