JP2010178611A - System interconnection type photovoltaic power generating system with self-sustaining function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photovoltaic power generation system which is capable of interconnecting with a commercial power system mainly, supplies power to a load and achieves self-sustaining even when the commercial power system is not used by an accident and an emergency. <P>SOLUTION: The photovoltaic power generation system includes a solar cell 51, a storage battery 57 and an independent power generator 56 and is capable of interconnecting with the commercial power system 54. When the commercial power system 54 is not capable of being used by a blackout or the like, power supply to the load is possible by power by the solar cell 51, by power by the independent power generator 56, and by power stored in the storage battery 57 in advance. Power loss of the load is improved by being provided with a phase-advanced capacitor 62 and an auxiliary charge of midnight power to the storage battery 57 is possible by a charge and discharge control panel 58. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solar power generation system that generates power using sunlight, which is natural energy, and the generated power is normally consumed by a load, and surplus power is sold to commercial power. The present invention also relates to a photovoltaic power generation system that can be used as a backup power source in the event of a disaster or emergency where the commercial power system cannot be used due to a power failure or the like.

  Photovoltaic power generation does not generate carbon dioxide at the time of power generation, and has been spreading in recent years as one of measures for preventing global warming. Electricity is generated if there is solar radiation, but the generated electric power fluctuates due to changes in illuminance. Photovoltaic power generation generates power when there is solar radiation during the day, but the output decreases during cloudy weather or bad weather, and cannot be output at night. For this reason, when using the output of solar cells for facilities that always use electricity, it is necessary to use power from the commercial power system when the output of the solar cells decreases, and the elderly and disaster victims Is expected to spread self-sustained solar power generation systems that can use the power generated by solar cells to supply stable power to facilities loads even when the commercial power system fails. ing.

Conventional technology

A conventional photovoltaic power generation system that mainly combines a solar cell and a storage battery will be described. FIG. 1 is a schematic diagram showing a pattern of a power supply state of a photovoltaic power generation system including a conventional solar battery and storage battery.
In FIG. 1, (1) and (3) show the state of power supply in a system that does not have a linkage function with a commercial power system, and (1) shows that there is daytime solar radiation and power is obtained from a solar cell. (3) shows the power supply state to the storage battery and the load when the power supply from the solar battery cannot be obtained at night or the like.
Also, in FIG. 1, (2) and (4) show the power supply state in the case of a system having a function of linking with a commercial power system, and (2) shows solar radiation during the day and power from the solar cell. The power supply state when obtained, (4) shows the power supply state to the storage battery and the load when power cannot be obtained from the solar battery at night or the like.
In addition, in each figure of (1) to (4) in FIG. 1, an arrow (→) indicates the direction of power supply.

  As a structure of the apparatus of the solar power generation system shown in FIG. 1, it has the structure which interposed the current collection box and the control panel between the solar cell and the storage battery. Moreover, it is the structure through the inverter for converting a control panel and a direct current into an alternating current as a structure of the apparatus in the period from the storage battery to the electric power supply to load.

The conventional photovoltaic power generation system having the configuration shown in FIG. 1 is not intended for the case where the commercial power system cannot be used due to an earthquake or a typhoon disaster. When operating, there are the following problems.
In the photovoltaic power generation system having the configuration shown in FIG. 1, first, direct current power generated by a solar battery is charged in a storage battery. Since the direct current from the storage battery is converted to AC power by the inverter via the control panel after the necessary amount of charge is secured for the storage battery, the power is consumed when the storage battery is not fully charged or when the output of the solar battery is small Cannot be supplied to the load.
The present invention has been made in view of the above points, and provides a self-sustained solar power generation system that can supply power to a load even when a commercial AC system cannot be used due to a disaster or emergency. It is intended to do.

Means to solve the problem

  In order to solve the above problems, the present invention is a solar power generation system that can be linked to a commercial power system with a solar battery, a storage battery, and a private generator, and the commercial power system cannot be used due to a power failure or the like Is a solar power generation system that enables a self-sustained operation using electric power from a solar battery, electric power from a private generator, and electric power stored in advance in the storage battery, and the invention of claim 1 is directed to charging the storage battery. As a means, it is possible to charge both DC power from a solar cell and power obtained by converting an AC current from a commercial power system into a DC current. In addition, in the storage of electric power from the commercial power grid to the power storage location, the solar power generation system is characterized in that the power at midnight is stored in preference to the commercial power during the daytime.

  In the invention of claim 2, when the power factor of the power load is small, even when the same power is used, the current increases and the power loss also increases. In addition, in the case of receiving power supply from the commercial power system, if the power factor is small, the power charge is also expensive. Therefore, the photovoltaic power generation system is characterized by having a phase advance capacitor for improving these power losses.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing a schematic configuration example of the present invention. As shown in the figure, the photovoltaic power generation system of the present invention converts a direct current output from a solar battery 51, a storage battery 57, the solar battery, and the storage battery into an alternating current, and supplies the current to a load 55. Switches 59a and 59b for charging the storage location 57 with both the electric power from the solar battery and the electric power from the commercial power system 54. A charge / discharge control panel for controlling charging and discharging of the storage battery 57, and a sensor 61 for measuring the discharge / charge amount of the storage battery and a circuit 61 for calculating the charge / discharge amount using the measured value. 58 is provided. Moreover, the private generator 56 is provided as a backup of the AC system power supply when the commercial AC system 54 becomes unusable. Furthermore, a phase advance capacitor 62 is provided for improving the power factor and suppressing power loss when supplying a load to the power.

In the photovoltaic power generation system of the present invention, linked operation with a commercial power system is possible, and when the commercial power system becomes unusable due to a power failure or the like, independent operation is possible.
When there is solar radiation in the daytime, the direct current generated by the solar cell 51 is collected by the current collection box 52 and converted into alternating current by the inverter built in the linkage control panel 53 to the commercial power system 54. When surplus power is generated, the power can be reversed and sold. In addition, an interlock is provided to automatically block reverse power flow to prevent accidents.

(System configuration of linkage control panel)
The linkage control panel 53 is composed of a control unit that incorporates an inverter for converting a direct current into an alternating current, an insulating transformer, and a linkage protection relay. The inverter employs a self-excited voltage transistor PWM system current control system, the inverter main switching system employs a voltage type, and the control system employs a current control system. A magnet switch is built in the system side of the insulation transformer, and the inverter and the commercial power system are linked / cut off. The link protection relay installed in the control unit is a composite digital relay, and includes a UVR, OVR, UFR, OFR relay, as well as a timer for setting the restart time at the time of system power recovery. Yes. The settling value and settling time of each relay can be set arbitrarily.

(How to start and stop the inverter)
The inverter built in the linkage control panel 53 employs a method of automatically operating / stopping by monitoring the output of the solar cell. The stop is due to a built-in switch. For synchronization with the commercial power system, the parallel commercial power supply voltage is confirmed, an output in which the voltage, frequency, and phase are synchronized is generated, and then the built-in switch is opened to temporarily increase the current. The power factor is controlled based on the parallel commercial power supply voltage, and power factor 1 control is performed to supply current of the same phase. Automatic control is performed to maximize the solar cell output. Further, when the inverter output voltage rises, the phase advance operation is automatically performed and the output suppression control is performed. In addition, about the control power supply of an inverter, the electric power generated from a solar cell is used, and at the time of low solar radiation, it is converted into direct current from a commercial power system via a converter and backed up. The above control functions are built in as inverter control functions.
In the embodiment, when the open voltage of the solar cell exceeds the set value of the start voltage for 20 minutes, or when the start voltage exceeds 105% of the set value for 10 seconds, the inverter is operated, It is set to stop when the current becomes 5% or less of the rating and 20 minutes have passed. The start-up voltage is set to a value obtained by adding 10 V to a value obtained by 80% of the optimum voltage at 25 ° C. of the solar cell.

(Single operation detection function)
For the function of detecting an isolated operation in the inverter built in the linkage control panel 53, two methods, a passive method and an active method, are used. As for the passive method, if a constant phase jump is detected in the commercial power system, it is determined that the operation is independent, and the inverter gate block and the switch are opened. As a detection method, the cycle of each cycle of the system voltage is measured, and the phase jump with respect to the average phase of the previous 10 cycles is monitored. The settling value is 2 ° and the settling time is 0.17 seconds (60 Hz). When the phase change returns to the average phase within the settling time, it is not detected to prevent erroneous detection. In the active system, the reactive power is varied by periodically changing the frequency of the output current of the inverter, and the periodic change of the frequency of the system is extracted to detect the isolated operation. When the inverter is linked to the commercial power system, the frequency of the system voltage is equal to the commercial frequency, and there is no effect due to fluctuations in reactive power. A frequency change occurs. Therefore, the isolated operation is detected by monitoring this.

(Control method during linked operation)
The power supply to the load except the case of the self-sustaining operation of the photovoltaic power generation system of the present invention is intended only for the daytime, and the solar cell output is monitored at night, and is built in the inverter constituting the linkage control panel 53. The inverter is stopped by a switch (contactor) to cut off the input of DC power to the inverter. In addition, the DC power to the inverter is cut off in the same manner as described above even when the power from the solar battery is insufficient due to insufficient solar radiation in the daytime.

(Linkage protection function)
In the embodiment, since it is installed in a public facility, the power generation stoppage of the solar cell by the power generation device side circuit breaker is adopted, and the power supply from the commercial power system to the conventional load is prioritized.

(Start-up of private generator)
The private generator 56 is used as a means for supplying AC power to replace the commercial AC system when the commercial power system cannot be used due to an accident or emergency. The private generator opens the power generation point electromagnetic switch (OVGR, OVR, UVR, OFR, UFR) according to the command of the independent operation detection function, and at the same time stops the inverter and stops / disconnects the output of power generation by the solar cell. Controls to start.

(Automatic operation after power recovery)
When a power failure is not recognized after a power failure recovery (when stopped only by UVR) or after a stop due to single operation detection, the supply of power from the photovoltaic power system to the load side is resumed autonomously after timing. In addition, when entering the autonomous operation state after a power failure, even if the power is restored, it will not be linked unless the independent load line for the autonomous operation and the independent operation changeover switch of the inverter have returned to the associated state. It will be linked after being removed.

(Control power supply)
A storage battery backup DC power supply is used for the control power of the linkage control panel. Further, the relay and the general control such as measurement are improved as separate storage batteries.

(With or without reverse flow)
In this embodiment, since the system distribution line is a general high-voltage line, it is assumed that there is a high-pressure linked reverse power flow.

(Charge / discharge control of storage battery)
The charge / discharge control of the storage battery 54 is performed by the charge / discharge control panel 55.
The storage battery 54 can store both the alternating current generated by the commercial AC system 54 and the direct current generated by the solar battery 51 by means of two switchable switches (59a and 59b) controlled by the charge / discharge control panel 55. It has a structure.

(Supplementary charge and recovery charge of storage battery)
Next, the auxiliary charging and recovery charging method of the embodiment configured as described above will be described.

(About supplementary charging)
During the day, the power generated by the solar cell 51 is linked to the commercial power system 54 via the linkage control panel 53. However, the start / stop of the grid linked operation is usually performed depending on the solar radiation intensity. In particular, when the sunshine intensity during cloudy weather or rainy weather changes slightly, start / stop is repeated. For this reason, it is preferable that the auxiliary charging of the storage battery 54 is performed after the system linkage stop in a state where the start / stop state of the system linkage system does not repeatedly occur. After operation, the switch 59b can charge the electric power on the commercial power system 54 side to the power storage 57 via the charge / discharge control panel, and the supplementary charge can be set in the time zone of midnight power with low electricity charges. It is a thing.

(Amount of electricity discharged from the battery)
During the self-sustained operation, the charging current and the discharging current are detected by the sensor 60 provided in the storage battery circuit, and the signal is sequentially output to the charge / discharge amount measuring circuit 61. Next, the discharge charge amount measurement circuit 61 measures the integrated values of the charge current and discharge current signals output from the sensor 60, calculates the total discharge electricity amount from this, and calculates the charge amount and charge pressure of recovery charge ( Fixed value) is determined. Next, the determined value is output as a signal to the charging / discharging control panel 58, and then the switches 59a, 59b are switched so that the charging / discharging control panel 58 performs charging based on the charging amount and the charging pressure. Recovery charging is performed by connecting to the commercial power system side.

(About recovery charge)
The recovery charging is performed after the autonomous operation. While daily supplementary charging is performed during the midnight power hours on the commercial power system 58 side, recovery charging will be able to respond quickly to an accident in the commercial power system due to the next disaster / emergency, etc. This is done before the linked operation with the commercial system. At that time, when there is an output from the solar battery, the storage battery is charged with DC power from the solar battery by the switch 59a, and when there is no output from the solar battery, the AC current of the commercial power system 54 is converted into direct current by the switch 59b. 57 recovery charge.

(Phase advance capacitor)
A method of improving the power factor using the phase advance capacitor 62 will be described.
When the power factor of the power load is small, the current increases and the power loss increases even when the same power is used. In addition, in the case of receiving power supply from the commercial power system, if the power factor is small, the power charge is also expensive. Therefore, a phase advance capacitor is installed to improve these power losses. If the power factor is improved by the phase advance capacitor, the current can be reduced for the same power, and the loss can be reduced by reducing the current. In addition, the electricity rate when using commercial power can be reduced by improving the power factor.

(Example of combination method of solar power generation, wind power generation and hydropower generation)
Next, the structural example at the time of combining the solar power generation system shown by this invention with wind power generation and hydropower generation is demonstrated.

FIG. 3 shows a solar cell, a wind power generator, and a power collection method using a hydroelectric generator when a wind power generation facility and a hydroelectric generation facility are combined with the solar power generation system shown in the present invention. The current collection box 63 has a structure for collecting direct currents generated by the solar cells 64, the wind power generators 65a and 65b, and the hydroelectric power generators 66a and 66b. FIG. 3 shows a method of collecting current when two wind power generators and two hydro power generators are combined. However, even if a plurality of wind power generators and hydroelectric power generators are appropriately added, no problem.
In the solar power generation system of the present invention, as described above, a plurality of wind power generators and hydroelectric power generators are added to increase the power output to enable power supply to the load.

(Example of power distribution to the facility)
Fig. 4 shows the situation between the commercial power system and the linkage control panel when two substations are installed in the facility in order to reduce power transmission loss in the facility when power consumption (load) facilities exist widely. The arrangement of electrical equipment is shown. The high-voltage commercial power system 71 is transformed into a low voltage by two substations 73a and 73b so that power can be supplied to the loads 75a and 75b, respectively, and a phase advance capacitor 74a is provided for each substation. 74b and private power generators 76a and 76b when the commercial power system cannot be used due to an accident or the like. As shown in this figure, even if power is supplied to a wide facility by converting high-voltage commercial power to a low voltage with multiple substations and supplying power to each load, Loss can be reduced.

The invention's effect

  The photovoltaic power generation system of the present invention enables the following.

(About linked operation)
This is a photovoltaic power generation system that enables function-linked operation while utilizing the function having an interlock with the commercial power system, and enables reverse power flow to the commercial power system. Therefore, the consumption of commercial power can be significantly reduced, and surplus power can be sold to commercial power. Therefore, the power cost of a facility that uses the system can be reduced.

(Regarding autonomous operation)
A storage battery and a private generator are provided, and charging of the storage battery has a structure in which both commercial AC power and solar battery DC power can be charged. Therefore, even if the commercial power system cannot be used due to a disaster or emergency during nighttime when the solar battery output is lost, rainy or overcast, etc., it can be operated stably and continuously, and power can be supplied to the load in the facility. . In addition, after the return to the commercial power system, it can respond to the next disaster / emergency, etc., so it is possible to recharge the storage battery with either commercial AC power or solar battery DC power, and the reliability as a backup power source is significantly improved. To do. In addition, the cost can be reduced by preferentially replenishing late-night commercial power with a low electricity bill with priority.

(Regarding phase advance capacitor)
When supplying power to the load, a phase advance capacitor is provided on the load side. Therefore, it is possible to reduce power loss when using electric power, and it is possible to efficiently use electric energy as well as cost reduction when using commercial power.

  Since it is possible to construct a system that combines not only electricity from solar cells but also electricity from natural energy such as hydroelectric power generation and wind power generation facilities, it is easy to construct a system that can benefit from the sale of electricity and carbon dioxide emissions trading. It becomes possible.

(About carbon dioxide reduction)
In recent years, global warming due to carbon dioxide has become a social problem, and the realization of a low-carbon society for that purpose is required. The example of the amount of carbon dioxide reduction by the solar power generation system of the said invention is as follows. For example, assuming that the power output by natural energy such as solar cells is 500 kW, the amount of generated power per day is 500 kW × 9.0 h / day = 4,500 kWh / day, and the amount of generated power per year is 4,500 kWh / day × 365 days / year = 1,642,500 kWh / year. Therefore, the annual reduction amount of carbon dioxide is 0.555 kg / kWh × 1,642,500 kWh / year = 911,587 kg / year = 910 tons / year.

(Reduction of power loss and reduction of carbon dioxide by phase-advancing capacitor)
Further, by providing a phase advance capacitor on the load side, the power factor is improved from 85% to 100% and the power loss is reduced by 15%. For example, when the power used is 200 kW, 200 kW × 15% × 24 h / day The power loss of 720 kWh / day and 720 kWh / day × 365 days = 262,800 kWh / year per year is reduced, and this is converted to annual carbon dioxide, 0.555 kg / kWh × 262 800 kWh / year = 145,854 kg / year = 145 tons / year.

  Therefore, when the solar power generation system of the present invention in the example shown above is used, when the amount of carbon dioxide reduction by natural energy such as sunlight and the amount of carbon dioxide reduction by the phase advance capacitor are combined, about 1,000 tons of dioxide Carbon can be reduced.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications may be made within the scope of the technical claims described in the claims and the specification and drawings. Deformation is possible.

The figure which shows the electric power supply form in the photovoltaic power generation system of the conventional method Example of photovoltaic power generation system in the present invention Current collection method using combined power generation facilities How to distribute power to the facility Link protection block diagram Sequence during autonomous operation

51 Solar cell 52 Current collection box 53 Linkage control panel (linkage inverter)
54 Commercial AC System 55 Load 56 Private Generator 57 Storage Battery 58 Charge / Discharge Control Panel 59a Switch 59b when Connected to DC Power Supply Side Switch 60 when Connected to AC Power Supply Side Sensor 61 for Measuring Charging Current and Discharge Current Charge / discharge measurement circuit 62 Phase advance capacitor 63 Current collection box 64 Solar cell 65a Wind power generator 1
65b Wind turbine generator 2
66a Hydroelectric power generator 1
66b Hydroelectric generator 2
71 Link control panel (Link inverter)
72 Commercial AC System 73a Substation Equipment 1
73b Substation equipment 2
74a Phase advance capacitor 1
74b Phase advance capacitor 2
75a Load 1
75b Load 2

Claims (2)

  A photovoltaic power generation system capable of linking operation with a photovoltaic power generation facility, a power storage facility, and a commercial power system equipped with a private power generator. Can be operated independently from the output power from the power generator and the power generated by the private generator. When charging the storage battery, both the power from the solar battery and the power from the commercial AC system can be charged, giving priority to the power from the commercial power system at midnight. A solar power generation system characterized by being able to store electricity.   A photovoltaic power generation system capable of linked operation with a photovoltaic power generation facility, a power storage facility, and a commercial power system equipped with a private generator, and having a phase advance capacitor for power factor improvement in supplying power to the load The photovoltaic power generation system according to claim 1.

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