JP3755769B2 - Grid-connected solar power generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a grid-connected solar power generation device that converts a solar cell output into AC power and connects to a commercial power distribution line of an electric power company for operation.
[0002]
[Prior art]
Although the grid-connected solar power generation device can recognize the amount of power obtained by solar power generation, there is no means for recognizing how this solar power generation can reduce carbon dioxide emissions from thermal power generation. It was.
[0003]
[Problems to be solved by the invention]
In the above-mentioned conventional technology, the user displays how much carbon dioxide generation is reduced compared to thermal power generation by the power generation of the solar power generation device, and recognizes how much it contributes to the reduction of carbon dioxide emissions. I can't.
[0004]
[Means for Solving the Problems]
The grid-connected solar power generation apparatus according to the present invention displays the carbon dioxide emission reduction amount regardless of the carbon atom weight ratio or the carbon dioxide molecular weight ratio. You can see at a glance how much it contributes to reducing carbon dioxide emissions, and strengthen awareness of global warming prevention.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a grid-connected solar power generation apparatus according to the present invention will be described below in detail with reference to the drawings.
[0006]
[Background Technology]
FIG. 1 is a block diagram showing a schematic configuration of a grid-connected photovoltaic power generation apparatus according to the background art. The grid-connected solar power generation device 1 is roughly composed of a solar cell array 2 and a grid-connected inverter 3. Reference numeral 4 denotes a distribution board in the house, 5 denotes various loads in the house, and 6 denotes a system power supply of the electric power company. The DC power generated by the solar cell array 2 is converted into AC power having the same quality as that of the system power supply 6 by the interconnection inverter 3, and the AC power is supplied to the load 5 through the distribution board 4 by the interconnection operation. The surplus power flows backward to the system power supply 6 via the distribution board 5. A group of minimum unit solar cells is referred to as a solar cell module. The solar cell modules 11 are connected in series to form a solar cell string 12, and a backflow prevention diode 13 is connected to each solar cell string 12. A plurality of serially connected bodies of the solar cell strings 12 and the backflow prevention diodes 13 are connected in parallel to constitute the solar cell array 2. The backflow prevention diode 13 is for preventing a current from flowing back from a higher voltage to a lower voltage due to variations in output voltage between the solar cell strings 12.
[0007]
The interconnected inverter 3 includes an inverter circuit 21 including a plurality of switching elements for performing PWM (pulse width modulation) and a filter for shaping a waveform, a control circuit 22 for controlling the inverter circuit 21, and a solar cell array. 2 and an inverter circuit 21 connected in series to detect the output current Ia of the solar cell array 2, and a DC current detector (shunt) 23, connected in series to the output side of the inverter circuit 21, and an inverter circuit 21 includes an alternating current detector (a shunt) 24 for detecting the output current Ib, a switch 25, a display unit 26, a manual switch 27, and the like.
[0008]
FIG. 2 is a block diagram showing a more specific configuration of the control circuit 22. The control circuit 22 converts the output current from the solar cell array 2 by resistance division to detect the output voltage Va of the solar cell array 2 and the output current from the inverter circuit 21 by resistance division. A voltage divider 32 that detects the output voltage Vb of the inverter circuit 21 by conversion, an A / D converter 33 that converts each of the four analog signals into digital signals, and an MPU (microprocessor unit) that executes arithmetic processing A central processing unit) 34 and a data input means 35. The MPU 34 has, as its function, voltage measuring means for measuring four voltage signals (output voltage Va, output current Ia, output voltage Vb, output current Ib of the inverter circuit 21) by the A / D converter 33. 41, data calculation processing means 42 for executing various calculations based on the measurement data, and data of specification values of the solar cell array 2 and the inverter circuit 21 required for output evaluation input from the data input means 35 are stored. In addition, a data storage means 43 for storing the data of the calculation result by the data calculation processing means 42, an inverter control means 44 for controlling the inverter circuit 21 based on the calculation result by the data calculation processing means 42, and a data calculation processing means 42 An abnormality specifying means 45 for specifying an abnormality based on a result calculated based on the four voltage signals; And a like display control means 46 for controlling to display on the display unit 26 by inputting a signal of the presence or absence of abnormality identifying means 45.
[0009]
The output characteristics of solar cells vary depending on the amount of solar radiation and cell temperature. That is, the maximum generated power increases as the amount of solar radiation increases, and the maximum generated power decreases as the cell temperature increases. The inverter circuit 21 in the interconnected inverter 3 is powered by the solar cell array 2 that is affected by variations in the amount of solar radiation and the cell temperature, and the inverter control means 44 in the control circuit 22 is operated by the data operation processing means 42. The solar cell maximum output point tracking method is adopted so as to extract the maximum generated power at each current value of the solar radiation amount and the cell temperature which fluctuate based on the above. This method is a control method for adjusting the operating point of the solar cell array 2 directly connected to the inverter circuit 21 to the maximum generated power by controlling the input impedance of the inverter circuit 21. FIG. 3 shows a load characteristic line that shows the maximum generated power point Pmax at which the output of the solar cell array becomes maximum on the output voltage-output current characteristic curve of the solar cell array determined by the amount of solar radiation and the cell temperature. Thus, the input impedance of the inverter circuit 21 is controlled. This will be specifically described with reference to FIG. When the interconnection inverter 3 is started, the output voltage Va of the solar cell array 2 is close to the open circuit voltage Voc, and the output current Ia hardly flows, so that the input impedance is large. Therefore, the input impedance is gradually decreased (the output voltage Va is decreased and the output current Ia is increased), and the operating point on the output voltage-output current characteristic is moved from the open voltage side toward the maximum generated power point Pmax. The maximum generated power point Pmax is tracked. The variable circuit of the input impedance is in the inverter circuit 21 and is controlled by the inverter control means 44.
[0010]
Using such input impedance control of the inverter circuit 21 by the inverter control means 44, the output performance of the solar cell array 2 is evaluated. That is, as an operation sequence that is automatically performed when the output of the inverter circuit 21 exceeds a predetermined value at a preset measurement interval (for example, once / month), once the interconnection operation is stopped, the arrow in FIG. As indicated by a, the input impedance of the inverter circuit 21 is gradually decreased from infinity, the operating voltage of the solar cell array 2 is changed within the input voltage range b of the inverter circuit 21, and the solar cell array 2 at that time Output voltage Va and output current Ia are measured by the voltage measuring means 41 in the control circuit 22, and the output power Pa (= Va × Ia) of the solar cell array 2 is calculated by the data calculation processing means 42, and the measured inverter circuit The maximum voltage value Va _[max] , the output power maximum value Pa _[max] , and the maximum current value Ia _[max] within the input voltage range b of 21 are obtained. I will. On the other hand, the electrical characteristics data at the time of rating of the solar cell array 2, that is, the solar radiation intensity of 1.0 kW / m ² , the open circuit voltage Voc, the short circuit current Isc, and the rated maximum output Pmax at the cell temperature of 25 ° C. This is set in the storage means 43. The data calculation processing means 42 has the three values Va _[max] , Pa _[max] , Ia _[max] obtained by the input impedance control and the three values Voc, Isc, Pmax read from the data storage means 43. Based on the above, the output performance evaluation for the rated specifications of the solar cell array 2 is performed as follows.
(1) Calculate the received solar radiation intensity Eo and solar cell operating temperature Tc (° C.) when Pa _[max] is measured.
[0011]
Eo = Ia _[max] / Isc ………………………………………………… ▲ 1 ▼
Further, the open-circuit voltage temperature coefficient of the solar cell array 2 is defined as Kv (V / ° C.),
Va _[max] = Voc− (25−Tc) · Kv · Voc
Tc = 25− (Voc−Va _[max] ) / (Kv · Voc) ……………… (2)
(2) The received solar radiation intensity of the rated maximum output Pmax of the solar cell array 2 is Eo, the solar cell operating temperature is Tc (° C.), and the maximum output power temperature coefficient of the solar cell array 2 is Kp (W / ° C.)
Pmax ′ = Eo · Pmax · {1− (25−Tc) · Kp} ……………… (3) As shown in (3), the theoretical maximum generated power Pmax ′ at the light receiving solar radiation intensity Eo and the operating temperature Tc is solar radiation. It can be calculated without using a meter or a thermometer.
(3) The ratio Rn between Pa _[max] and Pmax ′ is calculated.
[0012]
Rn = Pa _[max] / Pmax ′ …………………………………………… ▲ 4 ▼
By displaying the comparison result Rn as the output performance evaluation on the display unit 26 via the display control means 46, the performance of the solar cell array 2 with respect to the rated specification can be confirmed. In addition, the abnormality specifying unit 45 can determine whether the abnormality is normal or not, and display the result on the display unit 26, so that the performance of the solar cell array 2 with respect to the rated specification can be confirmed. For example, if 0.9 <Rn ≦ 1, the solar cell array output is normal. For example, if 0.7 <Rn ≦ 0.9, no inspection is required. For example, if Rn ≦ 0.7, the solar cell array output is Are displayed as abnormal.
[0013]
By measuring the above-mentioned ratio Rn at the above-mentioned interval and storing it as history data, the change over time with respect to the rated output of the solar cell array 2 after the installation of the solar power generation device 1 is clarified. Can do.
[0014]
Further, in the data calculation processing means 42, when the voltage is changed from the open circuit voltage of the solar cell array to the lowest input voltage of the inverter circuit 21 through the optimum operating point, the ratio dI / dV of the current change with respect to the voltage change is large. → Normal when transitioning to small, and transition from large → small → large → small (this corresponds to a dent in the output voltage-output current characteristic curve) and abnormal (solar cell array Light reception failure, output abnormality), and may be displayed on the display unit 26, respectively.
[0015]
Further, as indicated by an arrow a in FIG. 5, the input impedance of the inverter circuit 21 is gradually decreased from infinity, and the operating voltage of the solar cell array 2 is changed within the input voltage range b of the inverter circuit 21 to When measuring the output voltage Va and the output current Ia of the battery array 2, a plurality of sets of Va and Ia are acquired with a constant voltage change width, and the corresponding data are stored in the data storage means 43, These numerical data may be displayed on the display unit 26 as a table by the above operation. Alternatively, if each value is plotted and displayed with the X-axis direction as the output voltage and the Y-axis direction as the output current, the output voltage-output current characteristic curve of the solar cell array 2 can be easily obtained.
[0016]
The time required for the series of measurements is as short as a few minutes. After a series of measurements is completed, the solar power generation device 1 returns to the grid operation.
[0017]
In the above description, the measurement is automatically repeated at a predetermined measurement interval. However, the above measurement operation may be performed when the user or the inspector operates the manual switch 27 as necessary. .
[0018]
Assume that the output performance evaluation of the inverter circuit 21 is performed based on the ratio of input / output power of the inverter circuit 21 (power conversion efficiency). When the power conversion efficiency is 1/3 or more of the rating, the power conversion efficiency η of the inverter circuit 21 is
η = (Ib · Vb) / (Ia · Va) ………………………………… ▲ 5 ▼
Calculated by Therefore, the power conversion efficiency can be calculated without using a wattmeter and without consuming running costs. Storing the initial power conversion efficiency η ₀ at the time of installation of the photovoltaic power generation apparatus 1 in the data storage means 43 as a reference, comparing the power conversion efficiency η according to the equation (5) for each measurement with η ₀ , and By displaying the transition, the output performance of the inverter circuit 21 can be evaluated.
[0019]
Embodiment
The embodiment relates to the interconnection inverter 3 shown in FIG. 1 and the remote controller 7 corresponding thereto. FIG. 6 is a front view of the remote controller 7. In FIG. 6, 51 is a display unit composed of 7 segment LEDs, 52 is a W display LED that is lit when displaying an instantaneous value of the power generation amount (watts), and 53 is lit when displaying an integrated power amount within a certain period. Periodic integrated power amount display LED, 54 is a total integrated power amount display LED that is lit when displaying the integrated power amount from the installation of the device to the present, and 55 is a CO light that is lit when displaying the carbon dioxide emission reduction amount ₂ emission reduction LED, 56 LED is showing an LED, 58 is shutdown state sec LED, 57 which lights showing the interconnected operation operating state when the display of seconds elapsed time from Fukuden during a power outage , 59 is an LED indicating a self-sustained operation state when the load 5 is operated only by the electric power from the grid inverter 3 without receiving power supply from the grid power source 6, and 61 is the operation of the grid inverter 3 An operation / stop button for instructing stop, 62 is an environmental contribution monitor button for displaying carbon dioxide emission reduction, 63 is a display switching button for switching between period integrated power display and total integrated power display, Reference numeral 64 denotes an integrated electric energy reset button for resetting and clearing the stored period integrated electric energy. According to the literature “Consideration of CO ₂ emission intensity of photovoltaic power generation system” (published by Chemical Industry Association) and “Global warming impact analysis of power generation plant” (published by Central Research Institute of Electric Power Industry 1991), carbon dioxide (CO ₂ ) Emissions in terms of carbon are 0.196 kg-C / kWh per kWh for petroleum thermal power generation (kg-C represents the mass in terms of carbon). On the other hand, in the case of crystalline solar cells, the amount of CO ₂ emitted when manufacturing system equipment such as solar cells is used for 20 years, and the value divided by the amount of power generated for 20 years is emitted by solar power generation. Amount. The value is 0.017 kg-C / kWh in terms of carbon. A value obtained by subtracting the solar power generation from the oil thermal power generation, that is, 0.196−0.017 = 0.179 kg−C / kWh is the CO ₂ emission reduction amount (carbon conversion) per kWh. The DC power generated by the solar cell array 2 is converted into AC power by the inverter circuit 21 of the interconnection inverter 3 and is connected to the grid power supply 6. The generated electric power is referred to as AkWh. When the environmental contribution monitor button 62 is pressed, the CO ₂ emission reduction LED 55 is turned on, and the 7-segment LED of the remote controller 7 includes 0.179 × Akg-C / kWh as CO ₂ emission reduction (carbon conversion). It is displayed on the display unit 51. When the molecular weight of carbon dioxide is converted, the value in terms of carbon may be multiplied by the molecular weight ratio 44/12 of CO ₂ / C to display 0.656 × Akg-C / kWh. Note that the display unit 51 is not limited to a 7-segment LED, and may be a liquid crystal display, a plasma display, a fluorescent tube display, or the like. In addition, the carbon dioxide emission reduction amount by the carbon atom weight ratio and the carbon dioxide emission reduction amount by the carbon dioxide molecular weight ratio may be displayed at the same time, or may be configured to display alternately. Good. When switching the display, the display is switched every time the display switching button 63 is pressed. The above numerical values are provisionally determined, and the calculation method may be the same even if the numerical values are changed. With the display as described above, it is possible to make the user recognize how much it contributes to the reduction of carbon dioxide emissions.
[0020]
When the interconnection inverter 3 is normal, the W display LED 52 is turned on. When the output control function is activated when the voltage of the grid power supply 6 exceeds the set value defined in the grid operation discussion when the grid inverter 3 is in the grid operation, the solar power generation apparatus 1 is continuously operated. When the output power is suppressed and controlled by the temperature rise caused by the W, the W display LED 52 is blinked. Thereby, a normal state and an output suppression state can be distinguished and notified to a user or an inspector. Further, by changing the blinking interval of the W display LED 52, the voltage of the system power supply 6 exceeds the set value specified in the grid operation discussion and the output control function is activated, and due to the continuous operation of the photovoltaic power generator 1. You may comprise so that it may distinguish from the case where output electric power is restrained and controlled by the temperature rise. Further, a buzzer is provided so that the buzzer does not operate when the interconnection inverter 3 is normal, and the voltage of the system power supply 6 is negotiated when the interconnection inverter 3 is in the interconnection operation state. When the output control function is activated exceeding the set value specified in, and when the output power is controlled to be suppressed due to the temperature rise caused by the continuous operation of the photovoltaic power generator 1, the buzzer is sounded. Also good. In this case, by changing the oscillation frequency of the buzzer, the voltage of the system power supply 6 exceeds the set value specified in the grid operation discussion, and the output control function is activated, and it is caused by the continuous operation of the photovoltaic power generator 1. You may comprise so that it may distinguish from the case where output electric power is restrained and controlled by the temperature rise.
[0021]
【The invention's effect】
According to the present invention, since the carbon dioxide emission reduction amount is displayed regardless of the carbon atom weight ratio or the carbon dioxide molecular weight ratio, how much carbon dioxide emission reduction is contributed by the grid-connected solar power generation device. You can see at a glance whether or not to strengthen global awareness.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a grid-connected photovoltaic power generation apparatus according to the background art of the present invention. FIG. 2 is a block diagram showing a specific configuration of an inverter circuit control circuit in the background art. FIG. 3 is a characteristic diagram showing the output voltage-output current characteristics of the solar cell array for the background technology. FIG. 4 is an explanatory diagram showing the output operating point of the solar cell array for the background technology. Explanatory drawing of the maximum voltage value in the input voltage range of the inverter circuit obtained by the impedance control with respect to the output voltage, the maximum value of the output power, and the maximum current value FIG. 6 is a front view showing the external appearance of the remote controller for the interconnected inverter in the embodiment Figure [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Grid connection type solar power generation device, 2 ... Solar cell array, 3 ... Connection inverter, 4 ... Distribution board, 5 ... Load, 6 ... System power supply, 7 ... Remote controller, 11 ... Solar cell module, 12 ... Solar cell string, 13 ... Backflow prevention diode, 21 ... Inverter circuit, 22 ... Control circuit, 23 ... DC current detector, 24 ... AC current detector, 26 …… Display, 51 …… Display, 52 …… W display LED, 55 …… CO ₂ emission reduction LED, 62 …… Environmental contribution monitor button

Claims (1)

A grid connection having a control circuit for controlling an inverter circuit for converting a DC output of the solar cell array into an AC output based on an output current and an output voltage of the solar cell array so that the output of the solar cell array becomes a maximum generated power. Assuming that the same amount of power generated by the solar cell array in the solar power generation system is generated by oil-fired power generation, the amount of carbon dioxide reduction by solar power generation is calculated compared to oil-fired power generation. A grid-connected photovoltaic power generator configured to display.

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