JP4253598B2 - Solar power generation system with power storage function - Google Patents

Description

  The present invention relates to a photovoltaic power generation system having a power storage function.

  In the solar power generation system shown in FIG. 3, in the daytime, the DC power generated by the solar cell 1 is stored in the power storage means 2 composed of a storage battery or the like, and the DC power is converted into AC power using the forward / reverse conversion device 3. Then, the power is connected to the commercial system 4 and the power is supplied to the load 5, and at night, the AC power from the commercial system 4 is converted into DC power using the forward / reverse conversion device 3, and the power is stored in the power storage means 2. It is configured to store electric power. In the figure, 6 to 8 are circuit breakers, 9 is a backflow prevention diode, and 10 is an integrated watt-hour meter.

  In the photovoltaic power generation system configured as described above, when the generated power of the solar cell 1 is smaller than the power consumption of the load 5, all the generated power is consumed by the load 5, and the shortage of the generated power is the commercial system. 4 is supplied.

However, when the generated power is larger than the power consumption of the load 5, surplus power is generated, and therefore, the surplus power is supplied to the commercial system 4 as reverse power flow.
Japanese Patent Laid-Open No. 11-018317 Japanese Patent No. 3239106 JP 2002-171694 A

In the above-described solar power generation system, means for supplying surplus power to the commercial grid 4 as reverse power flow has been adopted. However, in recent years, the reverse power flow has been reduced by the solar cell 1 due to the power charge of the power company. It is necessary to specify whether the generated power is obtained or the power obtained from the power storage means 2.
However, in the conventional solar power generation system, it is not possible to determine whether the reverse power flow is the power generated by the solar cell 1 or the power obtained from the power storage means 2, so the power rate is calculated. It was extremely difficult.

  The present invention has been made in view of the above circumstances, and makes it possible to clearly specify that the reverse power flow power is generated power from a solar cell, as well as power generation from the solar cell and charging of power storage means. It is an object of the present invention to provide a photovoltaic power generation system having a power storage function that increases the degree of freedom of discharge and increases the system efficiency and the product standardization degree.

In order to achieve the above object, the present invention provides an inverter that is connected between a solar cell and a commercial system and supplies AC power to a load, and an AC output terminal of the inverter and one end of the commercial system. Is connected, and the other end is connected to the power storage means for storing DC power, and the load current and the current from the power storage means flowing through the forward / reverse conversion apparatus are input, the latter current from the former current A differential amplifier for checking and judging not to increase, a judgment output of this amplifier, an output current and output voltage of the inverse conversion device, and a current flowing through the forward / reverse conversion device are supplied, and these are calculated to be forward- reverse with the inverse conversion device. An interconnection protection function unit that outputs an output for opening each other switch inserted in the current path of the conversion device, and an output of the interconnection protection function unit is given to control the inverse conversion device 1 control unit and the differential Amplifier of judgment output, and a second control unit which outputs of the load current and the interconnection protection unit has on the forward and reverse conversion device as an output the value performs calculation given respectively,
Photovoltaic power generation output control by the inverse conversion device controlled by the first control unit,
The forward / reverse conversion device controlled by the second control unit performs charge / discharge output control to the power storage unit independently at the same time .

  As described above, according to the present invention, the power storage means is separated from the circuit so that the energy source for generating the reverse flow power can be recognized only from the photovoltaic power generation, thereby clearly generating the reverse flow power. Can be identified from solar power. Moreover, according to this invention, the freedom degree of the electric power generation from a solar cell and the charge / discharge of an electric power storage means can be raised, and the improvement of system efficiency and a product standardization degree can be aimed at.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same parts as those in FIG. FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention. A chopper 11 is inserted in an electric circuit connecting a solar cell 1 and a forward / reverse conversion device 3 composed of a power conditioner.

  In addition, a switch 13 that is controlled to open and close by an operation of a reverse power relay 12 provided in the electric circuit of the commercial system 4 is inserted in an electric circuit between the forward / reverse converter 3 and the power storage unit 2 including a storage battery. . Reference numeral 14 denotes an electromagnetic switch.

  In the first embodiment configured as described above, the DC power generated by the solar cell 1 is supplied to the forward / reverse converter 3 via the chopper 11, and the switch 13 is also connected to the power storage means 2. Is supplied through. The switch 13 is normally closed. Moreover, since the DC voltage value fluctuates according to the discharge state of the power storage means 2, the chopper 11 is provided in order to take out the photovoltaic power generation output to the maximum according to the fluctuation.

  The generated power from the solar cell 1 and the combined DC power from the power storage means 2 are converted into AC power via the forward / reverse converter 3 and supplied to the load 5.

At this time, the output power of the forward / reverse conversion device 3 is obtained by multiplying the load current i _l and the alternating voltage Vs by the multiplication unit 31 to obtain the effective power, and inputs it to the calculation unit 32. The calculation unit 32 operates by setting a value with a gain less than 1.0 in order to prevent reverse flow due to calculation errors.

In this state, when the power consumption W _LOAD of the load 5 decreases and the output of the solar cell 1 (output of the chopper 11) W _PV exceeds (W _LOAD <W _PV ), surplus power is supplied to the power storage means 2 as a charging current. Flowing. For this reason, when this charging current is detected by the detector 33, the switch 13 is opened by a command from the command unit 34.

  Further, when the AC power becomes larger than the power consumption of the load 5 due to the malfunction of the control device 35, the reverse power flow is generated and the reverse power flow is supplied to the commercial system 4. Then, the reverse power relay 12 operates and the switch 13 is opened by the operation signal.

  With this configuration, since the reverse power relay 12 is operating while the reverse power flow is occurring, the power storage means 2 is disconnected from the circuit by opening the switch 13, and only the solar cell 1 is connected. Operation as an energy source is guaranteed.

  By opening the switch 13, the DC power from the power storage unit 2 is not supplied to the forward / reverse converter 3. As a result, if the reverse flow continues further, the opening of the switch 13 is continued, so that the reverse flow power to the commercial system 4 is only solar power generation by the solar cell 1 which is a natural energy source. Is identified. For this reason, it becomes possible to reliably calculate the electricity rate based on the reverse power flow.

  In the first embodiment, priority is given to the output of photovoltaic power generation in order to increase the total efficiency. That is, when there is an output from the solar power generation, the power storage means 2 is usually avoided (in the above description, the power storage means 2 is charged), and the solar power generation is performed at night. The power storage means 2 is charged from the commercial system 4 only when there is no output.

  However, in order to maintain the durability of the power storage means 2, it is necessary to fully charge the battery, and since it cannot be fully charged only at night, the power storage means 2 is charged even during the daytime when solar power output is present. Must. For this reason, in the first embodiment, there is a possibility that the total efficiency of the system is somewhat lowered.

  FIG. 2 is a schematic configuration diagram showing a second embodiment of the present invention. In the second embodiment, two inverters 3a and 3b are used as power conditioners. The device 3a is controlled so as to supply the photovoltaic power to the load 5 together with the power of the commercial system 4, and the forward / reverse conversion device 3b is controlled to be used for charging and discharging between the commercial power and the power storage means 2. Is done.

  The control operation is performed by the control unit 21a for the inverse conversion device 3a and the control unit 21b for the forward / reverse conversion device 3b.

Reference numeral 22 denotes an interconnection protection function unit for system interconnection. The interconnection protection function unit 22 includes an output current i _{p of} the reverse conversion device 3a, a current i _b flowing through the forward / reverse conversion device 3b, and a forward / reverse conversion device 3b. AC voltage Vs and the output of the differential amplifier 23 are supplied.

  The interconnection protection function unit 22 calculates the above current and voltage values to obtain a common function such as an active isolated operation detection control function and an overcurrent protection function, and sends a signal to the control units 21a and 21b for protection. The functions are shared.

The differential amplifier 23 compares the load current i ₁ and the current i _b flowing through the forward / reverse conversion device 3b, and checks that the latter current does not increase. Therefore, by setting the ratio of the differential amplifier 23 changes the ratio of the discharge current i _b from the load current i _l a power storage unit 2, for adjusting the positive and negative reversal point.

  A status signal (current difference, positive / negative signal) output from the differential amplifier 23 is supplied to the control unit 21 b and the interconnection protection function unit 22. The control unit 21b performs a load power calculation combining the input status signal and the power supply voltage, sends the value as an output command to the forward / reverse conversion device 3b, and is used to control the discharge power of the power storage means 2.

  As the interconnection protection function unit 22, the electromagnetic switches 14 and 24 are opened by an overcurrent monitoring or control stop command from the solar cell 1 or the power storage unit 2, or an active control command for detecting an independent operation (Variable amount setting such as reactive power) is sent, the opening condition of the electromagnetic switch 24 is confirmed, and the opening command is sent when established. In addition, as the interconnection protection function, common management and control related to the grid interconnection of the reverse conversion device 3a and the forward / reverse conversion device 3b, such as protection control and connection protection control amount setting, are performed.

  In the second embodiment, since the reverse conversion device 3a and the forward / reverse conversion device 3b are independent of each other, one reverse conversion device 3a performs the photovoltaic power generation output control, and the other forward / reverse conversion device 3b uses the power storage means 2. It becomes possible to independently perform charge / discharge output control to the same time.

  Thus, in the second embodiment, a standard inverter for photovoltaic power generation can be applied as the reverse conversion device 3a, and a standard inverter for battery (power storage means) charging can be applied as the forward / reverse conversion device 3b, so that mass production and cost merit can be obtained.

  In the second form of the above configuration, when there is a solar power generation output by the solar cell 1 during the day, the output is supplied to the load 5 through the reverse transformation device 3a and the forward / reverse conversion device 3b from the power storage means 2 as well. And supplied to the load 5.

  At this time, the output from the power storage means 2 always compares the load power with the power stored in the power storage means 2 so that the power storage means 2 does not supply more than the load power. That is, reverse power flow from the power storage means 2 is prevented from occurring.

  Here, a few supplements will be made regarding reverse power flow and electricity rate measurement. The electric power from the photovoltaic power generation output may be measured as a generated power during reverse power flow, but when the power charged in the power storage means 2 from the commercial system is flowing in reverse power, It is not preferable to weigh.

  Therefore, the situation is confirmed, the output from the power storage means 2 is stopped, and the power charge is measured. For this reason, the following two steps are performed as means for preventing an error in power charge measurement by opening the electromagnetic switch 24 inserted in the electric path of the forward / reverse conversion device 3b.

(A) when the difference between the current from the load current and the power storage unit 2 is no longer positive (i.e., when the power of the power storage unit 2 from the load power is increased), it opens the electromagnetic switch 24 ( It opens when the discharge from the power storage means exceeds the load current).

  (B) In the state where the electromagnetic switch 14 is OFF, when the power supply current to the commercial system 4 becomes negative (reverse power flow), the electromagnetic switch 24 is opened.

  The first form is suitable when the plan system and capacity are small, and when cost is a priority. The second form is suitable when both the photovoltaic power generation and the power storage means have a large power capacity. That is, in the second embodiment, by installing the inverse conversion device 3a and the forward / reverse conversion device 3b separately, (1) cost merit by applying the standard unit, (2) freedom of control, and (3) from sunlight The advantage of power priority acquisition is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram which shows 1st Embodiment of this invention. The schematic block diagram which shows 2nd Embodiment of this invention. The schematic block diagram of the conventional solar power generation system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Solar cell 2 ... Electric power storage means 3, 3b ... Forward / reverse conversion device 3a ... Reverse conversion device 4 ... Commercial system 5 ... Load 11 ... Chopper 12 ... Reverse power relay 13 ... Switch 14, 24 ... Electromagnetic switch 21a, 21b ... Control part 22 ... Interconnection protection function part 23 ... Differential amplifier

Claims (1)

An inverse converter connected between the solar cell and the commercial system and supplying AC power to the load;
A forward / reverse conversion device in which one end is connected to the AC output end of this reverse conversion device and a commercial system, and the other end is connected to power storage means for storing DC power;
A load amplifier and a differential amplifier that receives and inputs the current from the power storage means that flows through the forward / reverse converter and checks that the latter current does not become larger than the former current, and
The judgment output of this amplifier, the output current and output voltage of the reverse conversion device, and the current flowing through the forward / reverse conversion device are supplied, and these are calculated to be separately opened and closed inserted in the current paths of the reverse conversion device and the forward / reverse conversion device An interconnection protection function unit that sends out output to open the device,
A first control unit that receives the output of the interconnection protection function unit and controls the inverse conversion device;
A determination output of the differential amplifier, a load current and an output of the interconnection protection function unit are respectively given, and a calculation is performed, and a second control unit which gives the value to the forward / reverse conversion device as an output;
Photovoltaic power generation output control by the inverse conversion device controlled by the first control unit,
A photovoltaic power generation system having a power storage function, wherein the forward / reverse conversion device controlled by the second control unit independently performs charge / discharge output control to the power storage means at the same time .

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