JP2019126110A - Power control unit and control method of the same - Google Patents

Abstract

To improve use efficiency of power generated by a dispersed power supply while a rise of system voltage during a reverse power flow is suppressed.SOLUTION: A power control unit 20 for dispersed power supply, which is interconnected to a power system 1, comprises: an inverter circuit 25 for converting power supplied from the dispersed power supply 10 from DC into AC and outputting it; and a controller 50. The controller 50 calculates received power Pgrid of a power receiving point 3 of the power system 1 on the basis of power consumption Pload of a load L which is branch-connected to a power line 5 connecting the power system 1 and the power control unit 20, and output power Pinv of the inverter circuit 25, controls an operation power factor COSφ of the inverter circuit 25 to a setting value smaller than 1 when the power receiving point 3 is a reverse power flow, and controls the operation power factor COSφ of the inverter circuit 25 to a value larger than the setting value when the power receiving point 3 is a forward power flow.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a technology for controlling an operating power factor of an inverter circuit in a power control device of a distributed power supply connected to a power system.

  BACKGROUND ART In recent years, the introduction of distributed power sources represented by a photovoltaic (PV) system has been promoted from the viewpoint of reducing dependence on fossil fuels and environmental issues. The PV system is a power control device such as a power conditioner, and converts an electric power generated by a solar panel into a direct current to an alternating current using an inverter circuit and outputs the power. Moreover, when the amount of power generation exceeds the power consumption of the connected load, the power is sold by flowing back current to the grid power supply side as surplus power. As a prior art document regarding such a power control apparatus, there exists a thing of following patent document 1. FIG.

JP, 2017-127047, A

In order to enhance the utilization efficiency of the electric power generated by the distributed power source such as solar power generation, it is desirable to make the operating power factor of the inverter circuit close to 1. However, when selling power, the output of the distributed power supply reversely flows to the system power supply side and the system voltage may rise, so the operating power factor of the inverter circuit is set to It is requested by the electric power companies to keep the value smaller than
The present invention has been completed based on the above circumstances, and it is an object of the present invention to improve utilization efficiency of power generated by distributed power sources such as solar power generation while suppressing an increase in grid voltage during reverse flow. I assume.

  An electric power control apparatus for distributed power supply linked to a power system, the control apparatus comprising: an inverter circuit that converts electric power supplied from the distributed power supply from direct current to alternating current and outputting the same; The received power of the power receiving point of the power system is calculated based on the power consumption of the load branch-connected to the power line connecting the power system and the power control apparatus and the output power of the inverter circuit, When the power receiving point is reverse power flow, the operating power factor of the inverter circuit is controlled to a set value smaller than 1, and when the power receiving point is forward power, the operating power factor of the inverter circuit is higher than the set value. Also control to a large value.

  A control method of a power control apparatus for distributed power supply linked to a power system, which includes power consumption of the load and branch circuit connected to a power line connecting the power system and the power control apparatus, and an output of the inverter circuit An inverter circuit that calculates the received power of the power receiving point of the power system based on the power, and converts the power supplied from the distributed power source from direct current to alternating current when the power receiving point is reverse power flow The driving power factor of is controlled to a set value smaller than 1, and when the power receiving point is forward power, the driving power factor of the inverter circuit is controlled to a value larger than the set value.

  In this configuration, it is possible to improve the utilization efficiency of the power generated by the distributed power supply while suppressing the increase of the system voltage during reverse flow.

Block diagram of the solar power generation system according to the first embodiment Block diagram showing the electrical configuration of the power meter Explanation of power flow Block diagram showing the detailed structure of the control device Flow chart showing the flow of control of driving power factor Graph showing changes in received power and driving power factor Block diagram showing the flow of power to the load during forward flow Block diagram showing the flow of power to the load during reverse flow Block diagram showing another embodiment of the solar power generation system in the second embodiment Diagram showing transition conditions of discharge and discharge stop for power storage device Graph showing changes in received power and driving power factor

  An electric power control apparatus for distributed power supply linked to a power system, the control apparatus comprising: an inverter circuit that converts electric power supplied from the distributed power supply from direct current to alternating current and outputting the same; The received power of the power receiving point of the power system is calculated based on the power consumption of the load branch-connected to the power line connecting the power system and the power control apparatus and the output power of the inverter circuit, When the power receiving point is reverse power flow, the operating power factor of the inverter circuit is controlled to a set value smaller than 1, and when the power receiving point is forward power, the operating power factor of the inverter circuit is higher than the set value. Also control to a large value.

  In this configuration, since the operating power factor of the inverter circuit is controlled to a set value smaller than 1 during reverse power flow, it is possible to suppress an increase in system voltage of the electric power system. In order to control the operating power factor of the inverter circuit to a value larger than the set value during forward flow, increase the utilization efficiency of the power generated by the distributed power supply compared to the case where the operating power factor is maintained at the set value. Can do. In order to obtain the received power from the power consumption of the load and the output power of the inverter circuit, it is not necessary to provide dedicated instruments for measuring the received power.

  It is desirable that the control device decreases the operating power factor of the inverter circuit when the received power at the power receiving point decreases below a first threshold during forward flow. According to this configuration, since the operating power factor of the inverter circuit is lowered before the power flow at the power receiving point is switched from the forward power flow to the reverse power flow, it is possible to suppress an increase in the system voltage of the power system at the time of the reverse power flow.

  When the received power at the power receiving point is larger than a second threshold larger than the first threshold, it is preferable to increase the driving power factor of the inverter circuit. According to this configuration, when the received power is larger than the second threshold, the operating power factor of the inverter circuit is adjusted to be increased, so that the received power at the power receiving point can be suppressed. Further, the range between the first threshold and the second threshold is a control dead zone in which the adjustment of the driving power factor is not performed. By providing such a control dead zone, control hunting of the power control device can be suppressed.

  In the configuration having the power storage device in parallel with the dispersed power source, it is preferable that the control device discharges the power storage device at the time of forward flow, and stop the discharge of the power storage device at the time of reverse power flow. According to this configuration, by discharging the power storage device at the time of forward flow, received power can be suppressed, and energy stored in the power storage device can be effectively used. In addition, in the case of reverse power flow, selling the energy stored in the power storage device can be suppressed by stopping the discharge.

  The control device starts discharging the power storage device when the received power at the power receiving point is equal to or higher than the second threshold, the operating power factor of the inverter circuit is an upper limit value, and the power receiving at the power receiving point When the power is less than the second threshold, it is preferable to stop the discharge of the power storage device. In this configuration, at the time of transition from reverse flow to forward flow, discharge of the power storage device can be started early after transition to forward flow. Therefore, energy stored in the power storage device can be effectively used. In addition, at the time of transition from forward flow to reverse flow, discharge of the power storage device can be stopped before reverse flow.

First Embodiment
1. Description of Solar Power Generation System S FIG. 1 is a block diagram of a solar power generation system S.
A photovoltaic power generation (PV: Photo Voltaic) system S includes a photovoltaic power generation panel 10 and a power conditioner 20. The solar panel 10 is an example of the “distributed power supply” of the present invention, and the power conditioner 20 is an example of the “power control device” of the present invention.

  The power conditioner 20 includes a converter circuit 21, an electrolytic capacitor C1, an inverter circuit 25, a filter circuit 27, a relay 29, a control device 50, a DC voltage detection unit 31, an output current detection unit 33, and an output. A voltage detection unit 35 and a system voltage detection unit 36 are provided.

  The converter circuit 21 is connected to the photovoltaic panel 10. The converter circuit 21 boosts the output voltage (direct current) of the photovoltaic power generation panel 10 and outputs it. The electrolytic capacitor C <b> 1 is disposed in the link portion 23 located between the converter circuit 21 and the inverter circuit 25. The electrolytic capacitor C1 is provided to stabilize the voltage of the link unit 23.

  The electric power generated by the photovoltaic panel 10 is input to the link unit 23 via the converter circuit 21. As a result, the voltage Vdc of the link unit 23 is increased.

  The inverter circuit 25 is connected to the output side of the converter circuit 21, converts the input DC power into AC power, and outputs it. More specifically, power corresponding to a voltage increased at the link unit 23 by the power generation of the solar panel 10 is input to the inverter circuit 25. Therefore, the power corresponding to the voltage increased from the reference value is converted from direct current to alternating current and output from the inverter circuit 25.

  The inverter circuit 25 is connected via the relay 29 to the power system 1 using the system power supply 2 as an AC power supply. The electric power system may be that of the electric power company, or may be an independent electric power system made up of the independent operation output of the large-sized power conditioner. A load L is connected to a power line 5 connecting the inverter circuit 25 and the power system 1 via a branch line 4. Therefore, AC power can be supplied from the power conditioner 20 to the load L, which is a demand facility. Further, due to the balance between the output power Pinv of the inverter circuit 25 and the power consumption Pload of the load L (when Pinv> Pload), AC power can be supplied not only to the load L but also to the power system 1. . The power receiving point 3 is a supply point of power by the power system 1, and as shown in FIG. 1, is a boundary portion between the power system 1 and a premises provided with a load L which is a demand facility.

  A power meter 40 is installed at the branch line 4 to which the load L is connected. The power meter 40 is, for example, a smart meter. As illustrated in FIG. 2, the power meter 40 includes a current measurement unit 41 that measures the current Iload of the load L, a voltage measurement unit 43 that measures the voltage Vload of the branch line 4, an arithmetic processing unit 45, and a communication unit 47. , Storage unit 49.

  The arithmetic processing unit 45 calculates the power consumption (active power) Pload of the load L based on the current Iload and the voltage Vload. For example, the power consumption (active power) Pload of the load L can be obtained from the average value of the product of the instantaneous value of the current Iload of the load L and the instantaneous value of the voltage Vload of the branch line 4. The power meter 40 is connected to the network NW by the communication unit 47. The control device 50 of the power conditioner 20 includes the communication unit 51, and can receive data of the power consumption Pload of the load L from the power meter 40 via the network NW.

  The relay 29 is installed for interconnection with the power system 1. By closing the relay 29, the photovoltaic power generation system S can be connected to the power system 1. The filter circuit 27 is disposed between the inverter circuit 25 and the relay 29. The filter circuit 27 is composed of a reactor L1 and a capacitor C2, and removes harmonic components from the output of the inverter circuit 25.

  The DC voltage detection unit 31 detects the voltage Vdc of the link unit 23. The voltage Vdc of the link unit 23 detected by the DC voltage detection unit 31 is input to the control device 50.

  The output current detection unit 33 detects an output current Iinv of the inverter circuit 25. Specifically, as shown in FIG. 1, the output current detection unit 33 is located between the reactor L1 and the capacitor C2 of the filter circuit 27, and detects the current of the reactor L1. The output current Iinv of the inverter circuit 25 detected by the output current detection unit 33 is input to the control device 50.

  The output voltage detection unit 35 is connected to the output side of the filter circuit 27 and detects the output voltage Vinv of the inverter circuit 25 after removing the harmonic component. The output current Iinv of the inverter circuit 25 detected by the output current detection unit 33 and the output voltage Vinv of the inverter circuit 25 detected by the output voltage detection unit 35 are input to the control device 50.

  The grid voltage detection unit 36 is disposed on the power grid 1 side of the relay 29 and detects a grid voltage Vgrid of the power grid 1. The grid voltage Vgrid detected by the grid voltage detection unit 36 is input to the control device 50.

Based on output power Pinv [W] of inverter circuit 25 and power consumption Pload [W] of load L, control device 50 receives received power Pgrid at power receiving point 3 of power system 1 according to the following equation (1). Calculate [W] (see FIG. 3).
Pgrid = Pload-Pinv (1)

  Control device 50 determines the state of power flow (hereinafter simply referred to as power flow) from received power Pgrid, and controls operation power factor COSφ of inverter circuit 25.

  In the case of Pgrid> 0, it is a power flow (forward power flow) from the system power supply 2 to the power receiving point 3, and in the case of Pgrid <0, it is a power flow (reverse power flow) from the power receiving point 3 to the system power supply 2. In FIG. 1 and FIG. 3, forward flow is indicated by A1, and reverse flow is indicated by A2.

  The operating power factor COSφ is a ratio of the active power Pinv [W] to the apparent power Sinv [VA] output from the inverter circuit 25. The phase angle φ is an angle of the output current Iinv with respect to the output voltage Vinv of the inverter circuit 25.

  COS φ = Pinv / Sinv (2)

  FIG. 4 is a diagram showing a control block related to control of the driving power factor COSφ in the control device 50. Control device 50 includes output power calculation unit 53, PLL circuit 55, operating power factor command unit 57, reactive current command unit 59, reactive power control unit 61, DC voltage control unit 63, output current control unit 65, inverter current control unit 67, a PWM control unit 69 is provided.

  The output power calculation unit 53 calculates the output power (active power) Pinv and the reactive power Qinv of the inverter circuit 25 from the output current Iinv and the output voltage Vinv of the inverter circuit 25 detected by the output current detector 33 and the output voltage detector 35. Calculate

  The PLL circuit 55 calculates the phase angle θ of the system voltage Vgrid from the detection value of the system voltage Vgrid detected by the system voltage detection unit 36. The phase angle is 0 ≦ θ <360 °.

  Driving power factor command unit 57 determines a command value PFinv * of driving power factor COSφ of inverter circuit 25 based on received power Pgrid detected by external measuring instrument 40. Specifically, two thresholds X1 and X2 are set for the received power Pgrid.

  Then, when received power Pgrid is smaller than first threshold value X1, driving power factor command unit 57 decreases power factor command value PFinv *. When received power Pgrid is equal to or greater than second threshold value X2, power factor command value PFinv * is increased. The second threshold X2 is larger than the first threshold X1 (X2> X1), the second threshold X2 is 500 W as an example, and the first threshold X1 is 250 W as an example.

  The reactive power command unit 59 calculates the reactive power command value Qinv * of the inverter circuit 25 that should be output, according to the power factor command value PFinv * and the active power Pinv of the inverter circuit 25 currently being output. Specifically, the product of power factor command value PFinv * and active power Pinv is generated as reactive power command value Qinv *.

  Reactive power control unit 61 calculates a control amount PI (Proportional-Integral) so that reactive power Qinv of inverter circuit 25 converges on reactive power command value Qinv *. Then, the reactive current target value Iqinv * of the inverter circuit 25 is calculated and output from the control amount obtained by PI calculation.

  The DC voltage control unit 63 performs PI calculation of the control amount so that the DC voltage Vdc of the link unit 23 converges to the DC voltage command value Vdc *. Then, the effective current target value Ipinv * of the inverter circuit 25 is calculated and output from the control amount obtained by PI calculation. The DC voltage command value Vdc * is a predetermined fixed value.

  The output current control unit 65 calculates the upper limit of the current command value so that the output current Iinv of the inverter circuit 25 does not exceed the rating. Specifically, based on the rated current of inverter circuit 25 and power factor command value PFinv *, effective current upper limit value Iplim and reactive current upper limit value Iqlim are calculated.

  The inverter current control unit 67 performs PI operation on the control amount so that the output current Iinv of the inverter circuit 25 converges to the current command value Iinv * shown by the following equation (3), and outputs the inverter circuit to the PWM control unit 69 A duty ratio Dy for performing PWM control of 25 is output.

  Iinv * = Ipinv * × sin θ + Iqinv * × cos θ (3)

  The PWM control unit 69 performs PWM control of the inverter circuit 25 based on the duty ratio Dy input from the inverter current control unit 67. Specifically, each semiconductor switch (not shown) constituting the inverter circuit 25 is subjected to PWM control. Thus, the output current Iinv of the inverter circuit 25 is adjusted to the current command value Iinv *. From the above, it is possible to control the driving power factor COSφ of the inverter circuit 25 to the power factor command value PFinv * calculated by the driving power factor command unit 57.

  Further, the control unit 50 is provided with a memory 53. The memory 53 stores a program for controlling the operating power factor COSφ of the inverter circuit 25 and a program for controlling charging and discharging of the power storage device 100.

2. Control of Driving Power Factor COSφ FIG. 5 is a flowchart (S10 to S70) showing a flow of control (hereinafter, power factor control) of the driving power factor COSφ of the inverter circuit 25.

  Control device 50 first receives received power Pgrid [W] of power receiving point 3 based on output power Pinv [W] of inverter circuit 25 and consumed power Pload [W] of load L measured by power meter 40. Is calculated (S10).

  Next, the driving power factor command unit 57 of the control device 50 compares the received power Pgrid calculated in S10 with the second threshold X2 (S20). The second threshold X2 is, for example, 500 W.

  If received power Pgrid at power reception point 3 is equal to or greater than second threshold X2 (S20: YES), driving power factor command unit 57 determines whether the current value of driving power factor COSφ is smaller than 1.00 (S30).

  When the current value of driving power factor COSφ is smaller than 1.00, driving power factor command unit 57 generates power factor command value PFinv * that increases driving power factor COSφ by a predetermined amount Z. The predetermined amount Z is, for example, 0.01 (S40).

  When power factor command value PFinv * is generated, output current Iinv of inverter circuit 25 is adjusted to current command value Iinv * corresponding to power factor command value PFinv * by inverter current control unit 67 and PWM control unit 69. Thus, the operating power factor COSφ of the inverter circuit 25 is adjusted to a target value, that is, a value increased by a predetermined amount Z from the current value.

  On the other hand, if the received power Pgrid at the power receiving point 3 is smaller than the second threshold X2 (S20: NO), the driving power factor command unit 57 compares the received power Pgrid with the first threshold X1 (S50). The first threshold X1 is, for example, 250 W.

  If received power Pgrid at power reception point 3 is smaller than first threshold X1 (S50: YES), driving power factor command unit 57 determines whether current driving power factor COSφ is smaller than set value Y (S60). The set value Y is, for example, 0.80.

  If the current driving power factor COSφ is larger than the set value Y, the driving power factor command unit 57 generates a power factor command value PFinv * that reduces the driving power factor COSφ by a predetermined amount Z. The predetermined amount Z is 0.01 as an example.

  When power factor command value PFinv * is generated, output current Iinv of inverter circuit 25 is adjusted by inverter current control unit 67 and PWM control unit 69 to current command value Iinv * corresponding to power factor command value PFinv *. Thus, the operating power factor COSφ of the inverter circuit 25 is adjusted to a target value, that is, a value reduced by a predetermined amount Z from the current value.

  In addition, when received power Pgrid is greater than first threshold X1 (S50: NO), or when operating power factor COSφ is less than or equal to the set value (Y = 0.80) (S60: NO), operating power factor of inverter circuit 25. COSφ is maintained at the current value.

  The above-described power factor control (S10 to S70) is repeatedly performed in a predetermined cycle during the output of the power conditioner 20. The process of calculating the received power Pgrid in S10 can be performed not only during the output of the power conditioner 20 but also while the power conditioner 20 is stopped. It is possible to monitor the current of 3.

  Next, a control example of the driving power factor COSφ of the inverter circuit 25 will be described. FIG. 6 is a graph showing temporal changes of the output power Pinv of the inverter circuit 25, the received power Pgrid of the power receiving point 3 and the operating power factor COSφ with load fluctuation. “B1 indicated by a broken line” in FIG. 6 indicates the power consumption Pload of the load L, “B2 indicated by a thick line” indicates the output power Pinv of the inverter circuit 25, “B3 indicated by an alternate long and short dash line” indicates the received power Pgrid of the power receiving point 3 Is shown.

  In FIG. 6, the load L starts to decrease from heavy load to light load at time t1. In the case of heavy load, as shown in FIG. 7, the power flow of the power receiving point 3 is forward power (Pgrid> 0), and power is supplied to the load L from both the photovoltaic system S and the power system 1. Ru.

  If the received power Pgrid of the power receiving point 3 is 500 W or more, the operating power factor COSφ of the inverter circuit 25 is 0.01 from the present value each time the power factor control (S10 to S70) shown in FIG. It is increased and continuously adjusted to the upper limit 1.00. Therefore, the operating power factor COSφ of the inverter circuit 25 is maintained at the upper limit value 1.00 during a heavy load period (period from start to t1) of the load L.

  From time t1 when the load L starts to decrease from a heavy load to a light load, the received power Pgrid of the power receiving point 3 decreases. Then, when all the power consumption Pload of the load L can be supplied only by the output of the solar power generation system S, the power flow of the power receiving point 3 becomes reverse power flow (Pgrid <0) as shown in FIG. Power is supplied from the power generation system S to the power system 1 as well as the load L.

  On the other hand, after time t2 when received power Pgrid at power receiving point 3 decreases and becomes smaller than the first threshold (X1 = 250 W), operating power factor COSφ of inverter circuit 25 is power factor control (S10 to S70 shown in FIG. 5). The value is continuously decreased by 0.01 and adjusted to the set value (Y = 0.80) each time the.

  Therefore, after time t3 when the power flow at power reception point 3 switches from forward power flow to reverse power flow, operating power factor COSφ of inverter circuit 25 is maintained at set value 0.80. Then, when the power consumption Pload of the load L becomes zero, all the output power Pinv of the inverter circuit 25 reversely flows and is supplied to the power system 1.

  As described above, since the operating power factor COSφ of the inverter circuit 25 is controlled to the set value 0.80 smaller than 1 at the time of reverse power flow (Pgrid <0), the system voltage Vgrid of the power system 1 is suppressed from rising. it can.

  Furthermore, when the load L increases from light load to heavy load, the received power Pgrid at the power receiving point 3 increases, and the power flow at the power receiving point 3 switches from reverse power flow to forward power flow. In the example of FIG. 6, it can be considered as a change (t4⇒t5) which traces time in reverse.

  After time t5 when received power Pgrid becomes larger than the second threshold (X2 = 500 W), driving power factor COSφ of inverter circuit 25 is continuously increased and adjusted by 0.01 by control device 50, and the upper limit is set value 0.80 It changes to the value 1.00. Then, the operating power factor COSφ of the inverter circuit 25 is maintained at the upper limit value 1.00 while the power receiving point 3 is a forward flow and the period during which the received power Pgrid is larger than the second threshold value X2.

  Since the active power Pinv output from the inverter circuit 25 is increased by increasing the operating power factor COSφ at the time of forward flow, received power Pgrid supplied from the power system 1 to the receiving point 3 can be suppressed.

  Further, the control device 50 compares the received power Pgrid of the power receiving point 3 with the second threshold (X2> X1) to increase the operating power factor COSφ of the inverter circuit 25.

  As described above, two thresholds X1 and X2 are provided as the threshold X for adjusting the operating power factor COSφ of the inverter circuit 25. A range (250 W to 500 W) between the two threshold values X1 and X2 is a control dead zone in which the adjustment of the driving power factor COSφ is not performed. The control hunting of the inverter circuit 25 can be suppressed by providing the control dead zone.

5. Description of Effects In the present configuration, at the time of reverse power flow, the operating power factor COSφ of the inverter circuit 25 is controlled to the set value Y smaller than 1, so that the system voltage Vgrid of the power system 1 can be suppressed from rising. Further, during forward flow, the photovoltaic power generation panel 10 is compared to the case where the operating power factor COSφ is maintained at the set value Y in order to control the operating power factor COSφ of the inverter circuit 25 to a value larger than the set value Y. It is possible to improve the utilization efficiency of the generated power. Further, in the present configuration, since the received power Pgrid is obtained from the power consumption Pload of the load L and the output power Pinv of the inverter circuit 25, it is not necessary to provide dedicated instruments for measuring the received power Pgrid.

Second Embodiment
The photovoltaic power generation system S of Embodiment 1 has a configuration including the photovoltaic power generation panel 10 and the power conditioner 20.

  The solar power generation system S1 of the second embodiment has a storage device 100 added to the solar power generation system S of the first embodiment. As shown in FIG. 9, the solar power generation system S1 includes a solar power generation panel 10, a power storage device 100, and a power conditioner 200.

  Power conditioner 200 differs in the number of converter circuits 21 from power conditioner 20 of the first embodiment, and links converter circuit 21A for a photovoltaic power generation panel and converter circuit 21B for power storage device 100. It is provided in parallel to the unit 23.

  The photovoltaic panel 10 and the storage device 100 are connected in parallel to the link 23 of the power conditioner 200 via the converter circuits 21A and 21B as shown in FIG.

  Power storage device 100 is, for example, a secondary battery or a capacitor. Power storage device 100 is a device for storing surplus power of photovoltaic power generation panel 10.

  As shown in FIG. 10, control unit 50 of solar power generation system S1 starts discharging of power storage device 100 when received power Pgrid is 500 W or more of second threshold X2. Then, if the driving power factor COSφ is 1.0 and the received power Pgrid is less than 500 W of the second threshold X2, the discharge of the power storage device 100 is stopped.

  FIG. 11 is an operation control example of the power conditioner 200, and is a graph showing changes in the received power Pgrid and the driving power factor COSφ at the time of power generation of the photovoltaic panel 10 such as during the daytime. “B1 indicated by a broken line” in FIG. 11 indicates the power consumption Pload of the load L, “B2 indicated by a thick line” indicates the output power Pinv of the inverter circuit 25, “B3 indicated by an alternate long and short dash line” indicates the received power Pgrid of the power receiving point 3 Is shown. Moreover, in FIG. 11, PV is a solar power generation panel output, and BT is an electrical storage apparatus output.

  Since the period from start to time t1 is forward flow with heavy load, the driving power factor COSφ of the inverter circuit 25 is controlled by the control device 50 to 1 which is the upper limit value. In addition, since received power Pgrid is larger than 500 W during a period until time t1, control device 50 controls power storage device 100 in the output state via converter circuit 21B (discharge). Therefore, power conditioner 200 is in an output state in which solar power generation panel 10 and power storage device 100 are used in combination during a period from start to time t1. The output of both the photovoltaic panel 10 and the storage device 100 is 2.5 kW, and the total output is 5 kW.

  Due to the load fluctuation, the received power Pgrid starts to decrease after time t1. At time ta when received power Pgrid falls below 500 W of second threshold X2, control device 50 sends a command to converter circuit 21B to stop the discharge.

  The output of power storage device 100 decreases after time ta and becomes zero at time tb. Therefore, after time tb, the power conditioner 200 shifts to a single output state by the photovoltaic panel 10, and has an output of 2.5 kW, which is half of the initial output. On the other hand, received power Pgrid further decreases from 500 W after time tb when output of power storage device 100 is stopped.

  Control device 50 sends a command to inverter circuit 25 to reduce operating power factor COSφ at time tc when received power Pgrid falls below 250 W of first threshold value X1.

  Thus, the driving power factor COSφ of the inverter circuit 25 is adjusted to decrease from the upper limit value “1”. Then, after time td when the power flow at the power receiving point changes from the forward direction to the reverse power flow, the driving power factor COSφ of the inverter circuit 25 is adjusted to the set value (Y = 0.80).

  Thereafter, when the load L increases from light load to heavy load, the received power Pgrid increases, and the power flow at the power receiving point 3 switches from reverse power flow to forward power flow. In the example of FIG. 11, it can be considered as a change (te⇒tf) in which time is traced in reverse.

  Control device 50 sends a command to start discharging to converter circuit 21B at time tf when received power Pgrid is 500 W or more. Therefore, after time tf when received power Pgrid reaches 500 W or more after transition from reverse power flow to forward power flow, power conditioner 200 is in an output state in which photovoltaic power generation panel 10 and power storage device 100 are used in combination.

  In addition, after time tf when the received power Pgrid is 500 W or more, the control device 50 continuously adjusts the operating power factor COSφ of the inverter circuit 25 in increments of 0.01. As a result, after the shift from the reverse flow to the forward flow, the operating power factor COSφ of the inverter circuit 25 changes from the set value 0.80 to the upper limit 1.00, and is maintained at the upper limit 1.00.

  As described above, when received power Pgrid reaches 500 W or more, control device 50 starts discharging of power storage device 100. Further, control device 50 stops the discharge of power storage device 100 when received power Pgrid is less than 500 W in a state where driving power factor COSφ is controlled to “1” which is the upper limit value. By doing this, it is possible to discharge power storage device 100 only in the case of forward power flow (Pgrid> 0), and in the case of reverse power flow (Pgrid <0), it is possible to stop the discharge.

  Further, received power Pgrid when power storage device 100 starts discharging is 500 W, which is second threshold value X2 for increasing operating power factor COSφ from set value 0.8. Therefore, after the transition from the reverse flow to the forward flow, power storage device 100 starts discharging at the same time as control for increasing operating power factor COSφ from set value 0.8 is started. From the above, compared to the case where discharge is started after waiting for adjustment of operating power factor COSφ to the upper limit value “1” (when discharge is started at time tg), discharge of power storage device 100 is performed. You can start early. Therefore, received power Pgrid can be suppressed, and energy stored in power storage device 100 can be effectively used.

Other Embodiments
The present invention is not limited to the embodiments described above with reference to the drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) In the first and second embodiments, the photovoltaic power generation panel 10 is shown as an example of the distributed power supply. The distributed power source is a general term for small-scale power generation equipment generally distributed and disposed adjacent to a demand place, and includes, for example, a wind power generator, a biomass power generator and the like in addition to the solar power generator 10. In the case of an AC power generator such as a wind power generator or a biomass power generator, the output of the power generator is rectified by a rectifier and converted to direct current, and then connected to the link unit 23. It is good to make it the system which converts to electric power.

  (2) In the first and second embodiments, the power conditioner 20 for PV is shown as an example of the power control apparatus. The power control device may have at least a configuration including the inverter circuit 25 and the control device 50, and the converter circuit 21, the electrolytic capacitor C1, the link unit 23, the filter circuit 27, the relay 29, and the like may be omitted. When the data of the grid voltage Vgrid can be obtained from an external measuring instrument or the like, the grid voltage detection unit 36 can be eliminated.

  (3) In the first and second embodiments, the set value Y of the driving power factor COSφ at the time of reverse power flow is set to 0.80. The set value Y may be a value smaller than 1 and may be a numerical value other than 0.80. In addition, the increase or decrease of the driving power factor COSφ is not limited to 0.01 increments, but may be another adjustment range such as 0.02 increments.

  (4) In the first and second embodiments, two threshold values X1 and X2 are set for received power Pgrid of power receiving point 3, and when received power Pgrid is smaller than first threshold X1, power factor command value PFinv * is decreased. By doing this, the driving power factor COSφ at the time of reverse power flow (Pgrid <0) is lowered to a set value (Y = 0.80). In addition, when received power Pgrid is larger than second threshold value X2, operating power factor COSφ at forward power flow (Pgrid> 0) is higher than the set value (Y = 0.80) by increasing power factor command value PFinv *. It was a big value.

  In addition to the above, the driving power factor COSφ may be adjusted by the following method. Based on whether the received power Pgrid at the power receiving point 3 is positive or negative, it is determined whether the power flow at the power receiving point 3 is a forward power flow or a reverse power flow. At the time of reverse power flow (Pgrid <0), the driving power factor COSφ is controlled to the set value (Y = 0.80). On the other hand, at the time of forward power flow (Pgrid> 0), the driving power factor COSφ at forward power flow (Pgrid> 0) is controlled to a value larger than the set value (Y = 0.80). In addition, similarly, it is also possible to control discharge and stop of discharge of power storage device 100 according to the state of the power flow at power reception point 3 (forward power flow or reverse power flow).

  (5) In the first and second embodiments, although an example in which the load L branched and connected to the power line 5 is single is shown, the load L may be plural. When there are a plurality of loads L, the received power Pgrid [W] of the power receiving point 3 may be calculated from the total power consumption Pload [W] of the multiple loads L and the output power Pinv [W] of the inverter circuit 25. Also, another power conditioner may be connected to the power line 5 together with the load L. When another power conditioner is connected together with the load L, the received power Pgrid of the power receiving point can be set by using the other power conditioner as a negative load according to the following equation (a).

Pgrid = (Pload-Pinv2) -Pinv1 (a)
Pinv1 is the output power of the inverter circuit 25 of the power conditioner 20 to be controlled, Pinv2 is the output power of the inverter circuit of another power conditioner connected to the power line 5.

DESCRIPTION OF SYMBOLS 1 ... Power system 2 ... System power supply 3 ... Receiving point 10 ... Photovoltaic panel (an example of "distributed power supply" of this invention)
20 ... Power conditioner (an example of the "power control device" of the present invention)
21 ... converter circuit 25 ... inverter circuit 27 ... filter circuit 29 ... relay 40 ... power meter 50 ... control device 100 ... storage device X1, X2 ... first threshold , Second threshold

Claims (6)

A power control apparatus for distributed power supply interconnected with a power system, comprising:
An inverter circuit that converts power supplied from a distributed power source from direct current to alternating current and outputs the converted power;
A controller, and
The controller is
Based on the power consumption of a load branch-connected to a power line connecting the power system and the power control apparatus and the output power of the inverter circuit, the received power of the power receiving point of the power system is calculated.
If the power receiving point is reverse power flow, control the operating power factor of the inverter circuit to a set value smaller than 1;
The power control device controls the operating power factor of the inverter circuit to a value larger than the set value when the power reception point is forward flow. The power control apparatus according to claim 1,
The controller is
A power control apparatus, which reduces the operating power factor of the inverter circuit when the received power at the power receiving point falls below a first threshold during forward flow. The power control apparatus according to claim 2,
The power control device, wherein the operating power factor of the inverter circuit is increased when the received power at the power receiving point is greater than a second threshold that is greater than the first threshold. The power control apparatus according to any one of claims 1 to 3, wherein
In a configuration having a power storage device in parallel with the distributed power supply,
The controller is
A power control apparatus, which discharges the power storage device at the time of forward flow, and stops the discharge of the power storage device at the time of reverse power flow. The power control apparatus according to claim 4,
The controller is
When the received power at the power receiving point is equal to or greater than a second threshold that increases the operating power factor of the inverter circuit, discharging of the power storage device is started,
The electric power control apparatus which stops discharge of the said electrical storage apparatus, when the driving power factor of the said inverter circuit is upper limit, and the received electric power of the said receiving point is less than the said 2nd threshold value. A control method of a power control apparatus for distributed power supply interconnected with a power system, comprising:
Based on the power consumption of the load branch-connected to the power line connecting the power system and the power control device and the output power of the inverter circuit of the power control device, the received power of the power receiving point of the power system is calculated ,
When the power receiving point is reverse power flow,
Converting the power supplied from the distributed power source from direct current to alternating current to control the operating power factor of the inverter circuit to a set value smaller than 1;
When the power receiving point is forward flow,
The control method of the electric power control apparatus which controls the driving power factor of the said inverter circuit to a bigger value than the said setting value.

Images