JP2014036550A - Power conditioner and power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conditioner and a power supply system therewith which supply power to a load while reliably preventing a reverse flow to a power system from a DC power source prohibited from producing a reverse flow.SOLUTION: A power conditioner 100 includes: a DC bus 10 for transmitting DC power supplied from a solar cell 50 permitted to produce a reverse flow to a power system 40; a bidirectional DC/AC converter 30 for bidirectionally converting power between the DC bus 10 and the power system 40; a DC bus 20 for transmitting DC power supplied from a power storage device 60 prohibited from producing a reverse flow to the power system 40; a feed section 36 for supplying power to a DC load 70 from the DC bus 20; and a unidirectionally conductive element 15 connected between the DC bus 10 and the DC bus 20 so as to conduct power from the DC bus 10 to the DC bus 20 but not to conduct power from the DC bus 20 to the DC bus 10.

Description

  The present invention relates to a power conditioner and a power supply system, and more particularly, to a power conditioner and a power supply system having a function of reversely flowing power generated by a DC power source to a power system.

  In recent years, with increasing awareness of global environmental problems, development of power supply systems that combine solar power generation and power storage using storage batteries has been underway. As a power conditioner used in this type of power supply system, a configuration having a nighttime storage battery charging function and a daytime storage battery discharging function in addition to a general photovoltaic power generation reverse power flow function has been proposed. (For example, refer nonpatent literature 1 and patent literature 1).

  However, in Japan, in consideration of the influence on the power system, it is not allowed to reversely flow the discharged power from the storage battery or the fuel cell to the power system. Therefore, in the above power conditioner, reverse power flow prevention control is performed to prevent reverse power flow from the storage battery to the power system.

  For example, in Non-Patent Document 1, when the power consumption of the load exceeds the generated power of the solar battery, the shortage of power is supplemented by the discharge power from the storage battery, and the discharge power from the storage battery does not flow into the power system. Discloses a configuration for performing reverse power flow prevention control for controlling discharge power.

  In Patent Document 1, a reverse power flow prevention circuit is provided between the connection point of the inverter circuit for the solar cell on the AC main power circuit and the AC distribution board, and the electric power output from the fuel cell and the secondary battery. However, a configuration is disclosed in which the AC distribution board is disconnected by the reverse power flow prevention circuit when the power consumed by the AC load and the DC load becomes equal to or higher.

JP 2011-15501 A

Yokoyama et al., "Development of a storage battery combined photovoltaic system" Power Solar System "", GS News Technical Report, June 2003, Vol. 62, No. 1

  However, according to the reverse power flow prevention control described in Non-Patent Document 1, the discharge power of the storage battery is set so that the power consumption of the load matches the total value of the generated power of the solar battery and the discharge power of the storage battery. By controlling, the power to be reversely flowed from the power conditioner to the power system is made zero or less. Therefore, the power from the solar battery cannot be reversely flowed while power is being supplied from the storage battery to the load.

  Moreover, in said patent document 1, since the alternating current distribution board is provided between the solar cell and the secondary battery, in order to supply the generated electric power of a solar cell to a secondary battery, the electric power generation of a solar cell It is necessary to convert electric power into an alternating voltage once by an inverter circuit and output it to an alternating current distribution board, and to convert the alternating voltage via this alternating current distribution board into a direct current voltage again by a power conversion circuit. Therefore, there is a problem that loss during power conversion increases.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to reliably prevent reverse power flow from a DC power source where reverse power flow is prohibited to a power system while preventing power from flowing to a load. To provide a power conditioner capable of supply and a power supply system including the same.

  In one aspect of the present invention, the power conditioner is coupled between the power system and the plurality of DC power sources and controls each power. The plurality of DC power sources include a first DC power source that allows reverse power flow to the power system and a second DC power source that prohibits reverse power flow to the power system. The power conditioner includes a first DC bus for transmitting DC power supplied from the first DC power source, and a power converter that performs bidirectional power conversion between the first DC bus and the power system. A second DC bus for transmitting DC power supplied from the second DC power source, a power supply unit for supplying power from the second DC bus to a DC load, and a first DC bus Connected between the first DC bus and the second DC bus so as to conduct power to the second DC bus while de-energizing power from the second DC bus to the first DC bus. And a unidirectional conducting element.

  Preferably, the unidirectional conducting element conducts power from the first DC bus to the second DC bus when the voltage of the first DC bus is greater than the voltage of the second DC bus, When the voltage of the DC bus becomes equal to or lower than the voltage of the second DC bus, power is made non-conductive from the first DC bus to the second DC bus.

  Preferably, the power conditioner further includes first power conversion control means for controlling power conversion in the power converter so that the voltage of the first DC bus is equal to or lower than the voltage of the second DC bus. .

  Preferably, the power conditioner includes second power conversion control means for controlling power conversion in the power conversion device so that a self-path current flowing through the power conversion device becomes a control target value, and second power conversion control. And adjusting means for adjusting the control target value so that the voltage of the first DC bus is equal to or lower than the voltage of the second DC bus during the execution of the means.

  Preferably, the unidirectional conducting element is a diode having an anode connected to the first DC bus and a cathode connected to the second DC bus.

  Preferably, the power conditioner has at least one first connection for electrically connecting the first DC power source to the first DC bus, and the second DC power source is connected to the second DC bus. And at least one second connection part for electrically connecting to.

  Preferably, the second DC power source is a rechargeable power storage device directly connected to the second DC bus via the second connection unit.

  Preferably, the power conditioner converts the direct current power from the first direct current power source into a voltage and outputs the first direct current power to the first direct current bus, and the direct current from the second direct current power source. A second voltage conversion unit for converting the voltage of the electric power to output to the second DC bus.

  In another aspect of the present invention, a power supply system includes a plurality of DC power sources, and a power conditioner coupled between the power system and the plurality of DC power sources and for controlling the respective power. The plurality of DC power sources include a first DC power source that allows reverse power flow to the power system and a second DC power source that prohibits reverse power flow to the power system. The power conditioner includes a first DC bus for transmitting DC power supplied from the first DC power source, and a power converter that performs bidirectional power conversion between the first DC bus and the power system. A second DC bus for transmitting DC power supplied from the second DC power source, a power supply unit for supplying power from the second DC bus to a DC load, and a first DC bus Connected between the first DC bus and the second DC bus so as to conduct power to the second DC bus while de-energizing power from the second DC bus to the first DC bus. And a unidirectional conducting element.

  According to the present invention, it is possible to supply power to a load while preventing a reverse power flow from a DC power source to which a reverse power flow to the power system is prohibited to the power system.

1 is a diagram schematically showing an overall configuration of a power supply system to which a power conditioner according to an embodiment of the present invention is applied. It is a figure which shows the remaining capacity-voltage curve of an electrical storage apparatus. It is a circuit diagram which shows the detailed structure of the bidirectional | two-way DC / AC converter in FIG. It is a figure which shows the control structure of the control part in FIG. It is the flowchart which showed the control processing procedure for implement | achieving self-path current control in the power conditioner by this Embodiment. It is a figure which shows schematically the structure of the power conditioner by the example of a change of this Embodiment. It is a figure which shows the structural example of the unidirectional conduction | electrical_connection element in the power conditioner by this Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a diagram schematically showing an overall configuration of a power supply system to which a power conditioner according to an embodiment of the present invention is applied.

  Referring to FIG. 1, the power supply system includes a solar battery 50 and a power storage device 60 that are DC power sources, and a power conditioner 100 coupled to these DC power sources and power system 40. Solar cell 50 is shown as a representative example of a “first DC power source” that allows reverse power flow to power system 40, and power storage device 60 is prohibited from reverse power flow to power system 40. It is shown as a representative example of the “second DC power source”.

  The power conditioner 100 is connected to the power system 40 and supplies power to the DC load 70. Specifically, the power conditioner 100 supplies power supplied from the solar cell 50, the power storage device 60 or the power system 40 to the DC load 70 via the DC buses 10 and 20. The DC load 70 is, for example, an electric device such as an air conditioner, a refrigerator, a washing machine, a television, a lighting device, or a personal computer used at home. Alternatively, it may be an electric device such as a computer, a copying machine or a facsimile used in an office, or an electric device such as a showcase or a lighting device used in a store.

  In the power supply system according to the present embodiment, a case where one solar cell 50, one power storage device 60, one power system 40, and one DC load 70 are provided will be described. It may be individual or plural.

  The power system 40 is typically a single-phase three-wire commercial AC power system. In the single-phase three-wire commercial AC power system, the neutral wire is grounded via a resistor, and AC200V is supplied using two wires other than the neutral wire (R-phase wire RL and T-phase wire TL). To do.

  The power storage device 60 is a rechargeable power storage element, and typically includes a secondary battery such as a lithium ion battery or a nickel metal hydride battery. The power storage device 60 is configured by connecting a plurality of battery cells in series, and has a rated voltage of 380 V as an example.

  The power conditioner 100 is configured to receive AC power from the power system 40 (purchase power) as described above, and to reversely flow (sell power) the power generated by the solar cell 50 to the power system 40. Has been. Specifically, the power conditioner 100 includes DC buses 10 and 20, a DC / DC converter 25, a bidirectional DC / AC converter 30, connection terminals 32 and 34, and a power supply terminal 36.

  The DC bus 10 is a power line for transmitting DC power supplied from the solar cell 50 via the DC / DC converter 25, and corresponds to the “first DC bus” in the present invention. DC bus 10 includes a positive bus PL and a negative bus NL, which are a pair of power lines.

  The connection terminal 32 constitutes a “connection portion” for electrically connecting the solar cell 50 to the DC bus 10. By connecting the solar cell 50 to the connection terminal 32, the electric power generated by the solar cell 50 is supplied to the DC bus 10.

  The DC / DC converter 25 is connected between the solar cell 50 and the DC bus 10, converts the DC power received from the solar cell 50 into a voltage, and supplies it to the DC bus 10. Specifically, the DC / DC converter 25 performs control (maximum power tracking control) so that the maximum power can be acquired from the solar cell 50. Instead of the configuration in which the DC / DC converter 25 is provided inside the power conditioner 100, a solar power generation system including the solar cell 50 and the DC / DC converter 25 may be coupled to the connection terminal 32.

  Bidirectional DC / AC converter 30 is connected between DC bus 10 and power system 40. The bidirectional DC / AC converter 30 converts AC power received (purchased) from the power system 40 into DC power and supplies it to the DC bus 10. In addition, the bidirectional DC / AC converter 30 converts the DC power received from the DC bus 10, that is, the generated power of the solar cell 50 that has been voltage-converted by the DC / DC converter 25 into AC power to the power system 40. Reverse power flow.

  In FIG. 1, the current flowing through the bidirectional DC / AC converter 30 during power purchase is denoted as Ibuy, and the current flowing through the bidirectional DC / AC converter 30 during power sale (reverse power flow) is denoted as Icell. Further, the power supplied from the solar cell 50 to the DC bus 10 via the DC / DC converter 24 is expressed as Ppv, and the voltage of the DC bus 10 (corresponding to the DC side voltage of the bidirectional DC / AC converter 25). Is expressed as Vdc1.

  The DC bus 20 is a power line for transmitting power supplied from the power storage device 60, and corresponds to the “second DC bus” in the present invention. In the configuration shown in FIG. 1, power storage device 60 is “directly connected” to DC bus 20, and exchanges power with DC bus 20. Here, “directly connected” means that a power converter such as a DC / DC converter is not interposed between the DC bus 20 and the power storage device 60. Therefore, the voltage of DC bus 20 is substantially equal to the power supply voltage of power storage device 60. Hereinafter, the voltage of the DC bus 20 (corresponding to the power supply voltage of the power storage device 60) is denoted as Vdc2.

  FIG. 2 is a diagram illustrating a remaining capacity-voltage curve of the power storage device 60. In FIG. 2, the horizontal axis indicates the remaining capacity (SOC: State of Charge) (%) of the power storage device 60, and the vertical axis indicates the voltage (V) of the power storage device 60. The SOC is a percentage (0 to 100%) of the current remaining capacity with respect to the full charge capacity. Referring to FIG. 2, power storage device 60 is 340 V when empty (SOC is 0%), 360 V when SOC is 20%, and 380 V (rated voltage) when SOC is 50%. 400V when the SOC is 80%, and 420V when the SOC is fully charged (SOC is 100%).

  In the characteristics shown in FIG. 2, the voltage of the power storage device 60 has a wide range of SOC of 20% to 80% and a fluctuation range of 380 ± 20 V is suppressed. Thus, since the change in voltage is relatively stable with respect to the change in SOC, power storage device 60 has a high voltage stabilization capability. By controlling charging / discharging of power storage device 60 so that the SOC is maintained within the SOC range (for example, 20% to 80%) in which the voltage can be stabilized, power storage device 60 provides a stable voltage to DC bus 20. Can be supplied.

  The power supply terminal 36 constitutes a “power supply unit” for supplying power from the DC bus 20 to the DC load 70. By connecting the DC load 70 to the power supply terminal 36, DC power from the DC bus 20 is supplied to the DC load 70.

  The power conditioner 100 further includes a unidirectional conducting element 15 connected between the DC bus 10 and the DC bus 20. The unidirectional conducting element 15 is an element that conducts electric power from the DC bus 10 to the DC bus 20, while making electric power non-conducting from the DC bus 20 to the DC bus 10. The unidirectional conducting element 15 is typically composed of a diode D0 having an anode connected to the DC bus 10 and a cathode connected to the DC bus 20. The current flows only in the direction from the DC bus 10 to the DC bus 20 due to the rectifying action of the diode D0. Thereby, the electric power discharged from power storage device 60 is suppressed from flowing to DC bus 10 via DC bus 20.

  As described above, the arrangement of the unidirectional conductive element 15 that allows power to pass only in the direction from the DC bus 10 to the DC bus 20 (does not pass power in the direction from the DC bus 20 to the DC bus 10) causes the storage of power. The discharge power of the device 60 can be blocked by hardware from flowing to the DC bus 10. Thereby, the control of the discharge power for preventing the reverse power flow from the power storage device 60 becomes unnecessary, and the reverse power flow from the power storage device 60 can be reliably prevented with a simple configuration.

  In addition, since the DC load 70 is configured to receive power from the DC bus 20, it is possible to continue supplying power to the DC load 70 while preventing reverse power flow from the power storage device 60.

(Configuration of bidirectional DC / AC converter)
As described above, the power conditioner 100 according to the present embodiment can cause the power generated by the solar cell 50 to flow backward to the power system 40 via the bidirectional DC / AC converter 30. Further, the power generated by the solar cell 50 can be supplied to the DC load 70 via the DC buses 10 and 20. Furthermore, the power storage device 60 can be charged using power obtained by subtracting the power supplied to the DC load 70 from the power generated by the solar battery 50.

  In addition, when an allowable value for power that can flow backward to the power system 40 is set by an electric power company or the like, the power conditioner 100 needs to control the power that flows backward so as not to exceed the allowable value. .

  Such interchange of the generated power of the solar cell 50 is performed by the bidirectional DC / AC converter 30. Hereinafter, the configuration of the bidirectional DC / AC converter 30 will be described.

FIG. 3 is a circuit diagram showing a detailed configuration of the bidirectional DC / AC converter 30 in FIG.
Referring to FIG. 3, bidirectional DC / AC converter 30 includes bidirectional inverter 300, interconnection reactors 310 and 312, DC voltage detection unit 330, AC voltage detection unit 332, and self-path current detection unit. 340 and a control unit 320.

  Bidirectional inverter 300 performs bidirectional power conversion between DC bus 10 and power system 40 in accordance with switching control signals S 1 to S 4 from control unit 320. Specifically, bidirectional inverter 300 includes transistors Q1 to Q4, which are switching elements, and diodes D1 to D4. Transistors Q1 and Q2 are connected in series between positive bus PL and negative bus NL constituting DC bus 10. An intermediate point between transistors Q1 and Q2 is connected to R-phase line RL. Interconnection reactor 310 is connected to R-phase line RL.

  Transistors Q3 and Q4 are connected in series between positive bus PL and negative bus NL. An intermediate point between transistors Q3 and Q4 is connected to T-phase line TL. Interconnection reactor 312 is connected to T-phase line TL.

  For example, IGBTs (Insulated Gate Bipolar Transistors) can be used as the transistors Q1 to Q4. Alternatively, a power switching element such as a power MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) may be used.

  DC voltage detection unit 330 is connected between positive bus PL and negative bus NL, and detects a voltage of DC power (voltage of DC bus 10) Vdc1 exchanged between DC bus 10 and bidirectional inverter 300. The detection result is output to the control unit 320. AC voltage detection unit 332 is connected between R-phase line RL and T-phase line TL, detects voltage Vac of AC power exchanged between bidirectional inverter 300 and power system 40, and the detection result Is output to the control unit 320.

  The own path current detection unit 340 is inserted in the T-phase line TL, detects the current value (own path current) Isell of AC power exchanged between the bidirectional inverter 300 and the power system 40, and the detection result Is output to the control unit 320. As described above, the self-path current includes the current Ibuy at the time of power purchase and the current Isel at the time of power sale (reverse power flow), but in the present embodiment, in the situation of reverse power flow to the power system 40. In order to explain the power conversion operation of the bidirectional DC / AC converter 30, the self-path current is denoted as “Isell”.

  Based on DC voltage Vdc1 received from DC voltage detection unit 330, AC voltage Vac received from AC voltage detection unit 332, and self-path current Isel received from self-path current detection unit 340, control unit 320 will be described later. In accordance with the control structure, switching control signals S1 to S4 for controlling on / off of the transistors Q1 to Q4 are generated, and the bidirectional inverter 300 is controlled.

FIG. 4 is a diagram showing a control structure of the control unit 320 in FIG.
Referring to FIG. 4, control unit 320 includes a control target value generation unit 400 and a switching control signal generation unit 410.

  The control target value generation unit 400 sets the current target value Isel * of the self-path current Isel during power sale (reverse power flow) as the control target value of the bidirectional DC / AC converter 30. This current target value Isell * can be set in advance so as to have a different current value according to the date and time, for example, and stored in a storage unit (not shown). Alternatively, by performing communication between the power company or the like and the control unit 320, the output allowable power Pmax that is the maximum power that can be reversely flowed to the power system 40 is acquired, and set based on the acquired output allowable power Pmax. You may make it do. When the target current value Isel * is set based on the allowable output power Pmax, the target current value Isel * is set to a value obtained by dividing the allowable output power Pmax by the AC voltage Vac (Icell * = Pmax / Vac). .

  Control target value generation unit 400 further sets control lower limit value Vdc1 * of voltage Vdc1 of DC bus 10. The control lower limit value Vdc1 * is set to a voltage equal to or lower than the voltage Vdc2 of the DC bus 20 (Vdc1 * ≦ Vdc2). In the present embodiment, since power storage device 60 is directly connected to DC bus 20, voltage Vdc2 of DC bus 20 is 340V to 420V according to the SOC of power storage device 60 according to the characteristics of power storage device 60 shown in FIG. Varies with voltage range. Control target value generation section 400 sets control lower limit value Vdc1 * to 340 V, which is the lower limit value of this voltage range. Thus, when the power conversion operation in bidirectional inverter 300 is controlled so that voltage Vdc1 of DC bus 10 matches control lower limit value Vdc1 *, DC bus 10 and DC bus 10 can be connected regardless of fluctuations in voltage Vdc2 of DC bus 20. A relationship of Vdc1 ≦ Vdc2 is established with the DC bus 20.

  As described above, when the relationship Vdc1 ≦ Vdc2 is established between the DC bus 10 and the DC bus 20, the unidirectional conducting element 15 (FIG. 1) becomes non-conducting. The generated power of the solar cell 50 supplied to is not supplied to the DC bus 20 but is supplied to the bidirectional DC / AC converter 30. That is, all the power generated by the solar cell 50 can be reversed. According to this, it is possible to reversely flow (sell power) all the generated power of the solar cell 50 while driving the DC load 70 with the power from the power storage device 60.

  On the other hand, when the relationship of Vdc1> Vdc2 is established between the DC bus 10 and the DC bus 20 during the execution of the self-path current control according to the current target value Isell * described above, the unidirectional conduction is established. Element 15 conducts. Thereby, the electric power supplied from the solar cell 50 to the DC bus 10 via the DC / DC converter 25 can be supplied to the power storage device 60 and / or the DC load 70 via the DC bus 20.

  Here, in the power supply system shown in FIG. 1, the generated power Ppv of the solar cell 50 varies depending on weather conditions. Therefore, in the power conditioner 100, a situation may occur in which the generated power Ppv of the solar cell 50 is smaller than the allowable output power Pmax. In such a situation, if the control of the self-path current in accordance with the above-described current target value Isell * is continuously performed, the voltage Vdc1 of the DC bus 10 may decrease, and may fall below the control lower limit value Vdc1 *.

  The control target value generation unit 400 prevents the voltage Vdc1 of the DC bus 10 from being lowered by reducing the current target value Isel * when the voltage Vdc1 of the DC bus 10 falls below the control lower limit value Vdc1 * as described above. To do. The decrease in the current target value Isel * is based on the current target value Isell * (= Pmax / Vac) set based on the allowable output power Pmax, and the voltage Vdc1 of the DC bus 10 matches the control lower limit value Vdc1 *. Thus, the current target value Isell * is adjusted.

  Specifically, when the current target value Isell * is decreased, the power flowing backward to the power system 40 is decreased, so that the voltage Vdc1 of the DC bus 10 is increased. At this time, when the voltage Vdc1 of the DC bus 10 exceeds the voltage Vdc2 of the DC bus 20, the unidirectional conducting element 15 becomes conductive, so that the generated power Ppv of the solar cell 50 passes through the DC bus 20 and the power storage device 60 and / or Or there is a possibility of being supplied to the DC load 70. Therefore, in the present embodiment, the relationship of Vdc1 ≦ Vdc2 is established between the DC bus 10 and the DC bus 20 by making the voltage Vdc1 of the DC bus 10 coincide with the control lower limit value Vdc1 *. Thereby, when the generated power Ppv of the solar cell 50 becomes smaller than the allowable output power Pmax, all the generated power Ppv of the solar cell 50 can be reversely flowed.

  In this way, the control target value generation unit 400 sets the current target value Isell * set based on the allowable output power Pmax as an initial value according to the voltage Vdc1 of the DC bus 10 during the execution of the self-path current control. The current target value Isell * is adjusted. Then, control target value generation section 400 outputs adjusted current target value Isell * to switching control signal generation section 410.

  When the switching control signal generation unit 410 receives the current target value Isel * from the control signal generation unit 400, the switching control signal generation unit 410 generates the switching control signals S1 to S4 such that the self-path current Isel becomes the current target value Icell *, and is bidirectional. The inverter 300 is controlled.

  Specifically, the switching control signal generation unit 410 is configured to include at least a proportional element (P) and an integral element (I), and the deviation of the self-path current Icell * with respect to the current target value Icell *. In response, an operation signal is generated. Then, when the switching control signal generation unit 410 generates a duty command that defines the on-duty of the transistors Q1 to Q4 of the bidirectional inverter 300 based on the operation signal, the switching control signal generation unit 410 compares the generated duty command with a carrier wave. The switching control signals S1 to S4 are generated.

  Note that the switching control signal generation unit 440 generates AC power (AC voltage Vac, AC current (self-current) transmitted and received between the power system 40 and the bidirectional DC / AC converter 30 in generating the switching control signals S1 to S4. Power factor correct control is executed for the path current (Isell). Specifically, the switching control signal generation unit 440 improves the power factor by correcting the waveform of the alternating current Icell so that the phase of the alternating current Icell matches the phase of the alternating voltage Vac.

  FIG. 5 is a flowchart showing a control processing procedure for realizing self-path current control in the power conditioner according to the present embodiment. The process according to the flowchart shown in FIG. 5 is executed by the control unit 320 at regular control cycles. Each step shown in FIG. 5 is realized by software processing and / or hardware processing by the control unit 320.

  Referring to FIG. 5, control unit 320 sets current target value Icell * of self-path current Isel in step S <b> 01. Specifically, control unit 320 sets current target value Isel * set based on output allowable power Pmax acquired by communication with an electric power company or the like as an initial value of current target value Icell *. Alternatively, the initial value of the current target value Isell * is set based on date / time information transmitted from a timer (not shown) by referring to information stored in the storage unit in advance.

  Control unit 320 sets control lower limit value Vdc1 * for voltage Vdc1 of DC bus 10 in step S02. As described above, control unit 320 sets control lower limit value Vdc1 * to the lower limit value (340 V) of the voltage range of DC bus 20.

  Next, the control unit 320 controls the bidirectional inverter 300 by generating the switching control signals S <b> 1 to S <b> 4 so that the self-path current Isel becomes the current target value Isel *. When the control unit 320 acquires the voltage Vdc1 of the DC bus 10 detected by the DC voltage detection unit 330 during the execution of the self-path current control, the control unit 320 acquires the acquired voltage Vdc1 of the DC bus 10 and the control lower limit value Vdc1 *. And the current target value Isell * is adjusted according to the comparison result.

  Specifically, in step S03, control unit 320 compares self-path current Isel detected by self-path current detection unit 340 with current target value Icell *. When the own path current Isel is smaller than the current target value Isel * (when YES is determined in step S03), the control unit 320 is based on the current deviation between the own path current Isel and the current target value Icell * in step S04. Switching control signals S1 to S4 are generated. By performing such control, the self-path current Isel increases.

  On the other hand, when the own path current Isel is equal to or larger than the current target value Isel * (when NO is determined in step S03), the control unit 320 performs a current deviation between the own path current Isel and the current target value Icell * in step S05. The switching control signals S1 to S4 based on the above are generated. By performing such control, the self-path current Isel increases.

  The control unit 320 obtains the voltage Vdc1 of the DC bus 10 from the DC voltage detection unit 330 during the execution of the current control shown in S03 to S05. Then, in step S06, control unit 320 determines whether or not voltage Vdc1 of DC bus 10 is equal to or higher than control lower limit value Vdc1 *. When the voltage Vdc1 of the DC bus 10 is smaller than the control lower limit value Vdc1 * (when NO is determined in step S06), the process proceeds to step S09 and the current target value Isel * is decreased so as to decrease the current target value Isel * by a predetermined amount ΔI. Adjust. This predetermined amount ΔI is determined in consideration of the control speed of current control in the bidirectional DC / AC converter 30. In bidirectional DC / AC converter 30, the power conversion operation is controlled according to the adjusted current target value Isell *, so that the power flowing backward to power system 40 is reduced and the voltage Vdc1 of DC bus 10 is increased. To do.

  On the other hand, when voltage Vdc1 of DC bus 10 is equal to or higher than control lower limit value Vdc1 (when YES is determined in step S06), control unit 320 further performs current target value Isel * in step S01 in step S07. It is determined whether or not the set initial value of Isell * is smaller. When the current target value Isel * is smaller than the initial value (when YES is determined in step S07), the control unit 320 sets the current target value Icell * as the return process for returning the current target value Isel * to the initial value. Increase by a quantitative ΔI.

  On the other hand, when current target value Isell * is equal to the initial value (when NO is determined in step S07), control unit 320 returns the process to step S03 without performing the return process described above.

  By performing the processing shown in steps S06 to S08, when the voltage Vdc1 of the DC bus 10 becomes lower than the control lower limit value Vdc1 * during execution of the self-path current control, the current target value Icell * is decreased. As a result, the voltage Vdc1 of the DC bus 10 increases. When the voltage Vdc1 of the DC bus 10 reaches the control lower limit value Vdc1 *, the current target value Isell * is increased to return to the initial value. In addition, when the voltage Vdc1 falls below the control lower limit value Vdc1 * by increasing the current target value Isell *, the current target value Isell * is decreased again. Thus, the voltage Vdc1 is made to coincide with the control lower limit value Vdc1 * by increasing or decreasing the current target value Isell * with respect to the initial value according to the voltage Vdc1 of the DC bus 10.

  As described above, according to the power conditioner according to the present embodiment, the reverse power flow from the power storage device 60 is hardened by the unidirectional conduction element 15 (diode D0) connected between the DC bus 10 and the DC bus 20. It is possible to continue supplying power from the DC bus 20 to the DC load 70 while blocking the power.

  Further, in the configuration in which the reverse power flow prevention control is performed as described in Patent Documents 1 and 2 described above, a control delay occurs when the load suddenly changes, and the reverse power flow from the power storage device can be reliably prevented. There is a risk of disappearing. On the other hand, according to the power conditioner according to the present embodiment, the reverse power flow from the power storage device is blocked by hardware, so that the reverse power flow from the power storage device can be reliably prevented.

  Furthermore, according to the power conditioner according to the present embodiment, the relationship of Vdc1 ≦ Vdc2 is established between the DC bus 10 and the DC bus 20 by the power conversion operation in the bidirectional DC / AC converter 30. The direction conducting element 15 can be made non-conducting. Thereby, all the power generated by the solar cell 50 supplied to the DC bus 10 can be made to flow backward.

(Configuration example of the inverter)
In the above-described embodiment, the solar cell 50 is shown as a “first DC power source” in which reverse power flow to the power system 40 is allowed, and “second DC” is prohibited from reverse power flow to the power system 40. Although the power storage device 60 is shown as the “power source”, these DC power sources are not limited to the above example. For example, the “first DC power source” includes a wind power generator. The “second direct current power source” includes a fuel cell.

  In the above-described embodiment, the example in which the power storage device 60 that is the “second DC power source” is directly connected to the DC bus 20 has been described, but DC / DC conversion is performed between the power storage device 60 and the DC bus 20. The present invention can also be applied to a configuration (see FIG. 5) in which devices are connected.

  Furthermore, in the above-described embodiment, an example in which one “first DC power source” and one “second DC power source” are provided is shown. However, as shown in FIG. Similar effects can be obtained.

  FIG. 6 is a diagram schematically showing a configuration of a power conditioner according to a modification of the present embodiment.

  Referring to FIG. 6, a power conditioner 110 according to this modification is a plurality of (for example, two) DC / DC converters connected in parallel to DC bus 10 in power conditioner 100 shown in FIG. 1. 25 and a plurality of (for example, two) DC / DC converters 35 connected in parallel to the DC bus 20.

  Since configurations of DC / DC converter 25, bidirectional DC / AC converter 30, and unidirectional conducting element 15 are the same as those in FIG. 1, detailed description will not be repeated. Each of the plurality of DC / DC converters 35 performs bidirectional voltage conversion between the corresponding power storage device 60 and the DC bus 20. Similar to FIG. 1, the individual power storage devices 60 may be directly connected to the DC bus 20 without the DC / DC converter 35.

  Also in the configuration shown in FIG. 6, the reverse power flow from the plurality of power storage devices 60 can be blocked by hardware by the unidirectional conduction element 15 (diode D0) connected between the DC bus 10 and the DC bus 20. . Further, by controlling power conversion in the bidirectional DC / AC converter 30 so that the voltage Vdc1 of the DC bus 10 is lower than the voltage Vdc2 of the DC bus 20, a plurality of power storage devices are provided for the DC load 70. While supplying electric power from 60, all the generated electric power of the plurality of solar cells 50 can be reversely flowed to the electric power system 40. Furthermore, when an allowable value is set for the electric power that flows backward to the power system 40 by an electric power company or the like, the electric power generated by the plurality of solar cells 50 may be reversely flowed within a range not exceeding the allowable value. it can.

(Configuration of unidirectional conducting element)
In the above-described embodiment, an example in which the diode D0 having the anode connected to the DC bus 10 and the cathode connected to the DC bus 20 is used as the unidirectional conducting element 15 is shown in FIG. Alternatively, a configuration using a switch SW configured to be able to electrically connect and disconnect the DC bus 10 and the DC bus 20 may be employed.

  Specifically, referring to FIG. 7, switch SW is connected between DC bus 10 and DC bus 20, and ON / OFF is controlled according to control signal CNT from bidirectional DC / AC converter 30. The In bidirectional DC / AC converter 30, control unit 320 (FIG. 3) uses voltage Vdc2 of DC bus 20 detected by DC voltage detection unit 16 and DC bus Vdc1 detected by DC voltage detection unit 330. Compare. When voltage Vdc1 ≧ voltage Vdc2, control unit 320 generates control signal CNT for turning on switch SW. On the other hand, when voltage Vdc2 <voltage Vdc1, control unit 320 generates control signal CNT for turning off switch SW. As a result, a rectifying action is realized in which power is passed only in the direction from the DC bus 10 to the DC bus 20 (power is not passed in the direction from the DC bus 20 to the DC bus 10).

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  10, 20 DC bus, 15 unidirectional conducting element, 25, 35 DC / DC converter, 30 bidirectional DC / AC converter, 32, 34 connection terminal, 36 feeding terminal, 40 power system, 50 solar cell, 60 power storage Apparatus, 70 DC load, 100, 110 power conditioner, 300 bidirectional inverter, 310, 312 interconnection reactor, 320 control unit, 16, 330 DC voltage detection unit, 332 AC voltage detection unit, 340 own path current detection unit, 400 control target value generation unit, 410 switching control signal generation unit, D0 to D4 diode, Q1 to Q4 transistor, SW switch.

Claims (9)

A power conditioner that is coupled between a power system and a plurality of DC power sources and controls each power,
The plurality of DC power sources are:
A first DC power source that allows reverse power flow to the power system;
A second DC power source that is prohibited from reverse power flow to the power system,
A first DC bus for transmitting DC power supplied from the first DC power source;
A power converter that performs bidirectional power conversion between the first DC bus and the power system;
A second DC bus for transmitting DC power supplied from the second DC power source;
A power feeding unit for supplying power to the DC load from the second DC bus;
The first DC bus so that power is conducted from the first DC bus to the second DC bus while power is turned off from the second DC bus to the first DC bus. And a unidirectional conducting element connected between the second DC buses.   The unidirectional conducting element conducts power from the first DC bus to the second DC bus when the voltage of the first DC bus is larger than the voltage of the second DC bus, The power supply is configured to be non-conductive from the first DC bus to the second DC bus when the voltage of the first DC bus is equal to or lower than the voltage of the second DC bus. The power conditioner described in 1.   3. The power conversion apparatus according to claim 2, further comprising a first power conversion control unit configured to control power conversion in the power converter so that a voltage of the first DC bus is equal to or lower than a voltage of the second DC bus. The listed inverter. Second power conversion control means for controlling power conversion in the power conversion device so that a self-path current flowing in the power conversion device becomes a control target value;
Adjusting means for adjusting the control target value so that the voltage of the first DC bus is equal to or lower than the voltage of the second DC bus during the execution of the second power conversion control means; The power conditioner of Claim 2 or 3 provided.   5. The device according to claim 1, wherein the unidirectional conducting element is a diode having an anode connected to the first DC bus and a cathode connected to the second DC bus. 6. Inverter. At least one first connection for electrically connecting the first DC power source to the first DC bus;
The power conditioner according to claim 1, further comprising at least one second connection portion for electrically connecting the second DC power source to the second DC bus.   7. The power conditioner according to claim 6, wherein the second DC power source is a rechargeable power storage device directly connected to the second DC bus via the second connection unit. A first voltage converter for converting the voltage of the DC power from the first DC power source and outputting the voltage to the first DC bus;
8. The apparatus according to claim 1, further comprising: a second voltage conversion unit configured to convert the DC power from the second DC power source into a voltage and output the second DC power to the second DC bus. Power conditioner. A plurality of DC power sources;
A power conditioner coupled between a power system and the plurality of DC power sources and controlling each power; and
The plurality of DC power sources are:
A first DC power source that allows reverse power flow to the power system;
A second DC power source that is prohibited from reverse power flow to the power system,
The inverter is
A first DC bus for transmitting DC power supplied from the first DC power source;
A power converter that performs bidirectional power conversion between the first DC bus and the power system;
A second DC bus for transmitting DC power supplied from the second DC power source;
A power feeding unit for supplying power to the DC load from the second DC bus;
The first DC bus so that power is conducted from the first DC bus to the second DC bus while power is turned off from the second DC bus to the first DC bus. And a unidirectional conducting element connected between the second DC buses.

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