JP5506642B2 - Inverter - Google Patents

Description

  The present invention relates to a power conditioner that converts DC power from a solar cell to generate AC power.

  As part of CO2 reduction aimed at preventing global warming, the spread of photovoltaic power generation systems is expanding. In a solar power generation system, solar light energy is converted into DC power by a solar cell module, DC power is converted into AC power by a power conditioner, and connected to a system power supply (commercial power supply). Can be used and sold to power companies.

  The power conditioner includes an inverter that converts DC power output from the solar cell module into AC power, a reactor for waveform improvement, and a transformer that converts AC voltage output from the inverter into a system voltage. The power conditioner needs to convert DC power generated in the solar cell module into AC with little loss, and is required to convert efficiently.

  Related conventional techniques include those described in Patent Document 1 and Patent Document 2. Patent Document 1 discloses MPPT (Maximum Power Point Tracking) control for efficiently converting electric power from a solar cell module. However, the power conditioner described in Patent Document 1 is not focused on output under natural conditions, and further efficiency improvement is expected.

  In addition, in the invention proposed by the present applicant (Japanese Patent Application No. 2009-124843), an amorphous transformer is used in order to increase the conversion efficiency below the rated output in consideration of the output under natural conditions. The power output from the inverter may contain harmonics and direct current components, and in such a case, measures are taken for either or both of the transformer and the inverter. In the proposed invention, the DC bias is countered by offsetting the current transformer that measures the inverter output current before operation.

  However, since the operation is complicated in the above, further simplification is desired. Moreover, as a countermeasure when DC magnetism is caused by a transformer made of a silicon steel plate, as shown in Patent Document 2, a gap of a magnetic insulator is interposed in a part of a magnetic circuit composed of an iron core. A Hall element is attached to the gap, and the magnetic flux density is directly measured from the Hall element to measure even a slight DC bias with high accuracy.

JP 2008-300745 A JP 05-175061 A

  However, it is extremely difficult to provide a magnetic insulator gap in the laminated part of the amorphous foil that constitutes the core of the amorphous transformer, and even if it is provided, the magnetic characteristics are deteriorated and the conversion efficiency of the solar cell module is improved. It becomes difficult. When the DC bias is actually caused continuously, the transformer will be abnormally heated, but conventionally there is no detection means and there is a risk of the transformer being deteriorated.

  In view of the above problems, an object of the present invention is to provide a high-efficiency power conditioner in which a DC bias is countered with a simple configuration in a power conditioner equipped with a transformer. Furthermore, it aims at providing the power conditioner which improved the maintainability with respect to the lifetime of a transformer by the heating at the time of abnormality occurrence.

To solve the above problems, the present invention converts DC power from the solar power generation module in a power conditioner that generates AC power is converted by the inverter, to the system voltage and transforms the converted AC voltage by the inverter An amorphous transformer, a temperature sensor fixed on the surface of the iron core of the amorphous transformer and detecting the temperature of the iron core, and detecting a DC bias in the amorphous transformer based on the temperature detected by the temperature sensor Thus, a control unit for controlling the operation of the inverter is provided.

  Further, in the power conditioner described above, the control unit controls to stop the operation of the inverter when the temperature sensor reaches a predetermined temperature and to restart the operation when the temperature decreases. And

In order to solve the above-mentioned problems, the present invention is a power conditioner for generating AC power by converting DC power from a photovoltaic power generation module with an inverter.
An amorphous transformer that transforms the alternating voltage converted by the inverter into a system voltage, a temperature sensor that detects an internal temperature of the amorphous transformer, and a temperature sensor that detects the internal temperature of the amorphous transformer. A control unit for controlling the operation is provided, and the control unit predicts the life of the transformer based on the detected internal temperature of the transformer.

  In the power conditioner described above, the control unit integrates the stop time or the number of stops of the inverter, and displays the life from a comparison between the integrated value and preset life data.

  According to the present invention, it is possible to take measures against direct current bias with a simple configuration. Furthermore, maintainability with respect to the life of the transformer due to heat generated when an abnormality occurs can be improved.

Explanatory drawing of the whole structure of a solar power generation system. Explanatory drawing of the circuit of the power conditioner of this invention Example. Explanatory drawing of the partial load ratio and power generation amount of a solar power generation system. Explanatory drawing of the efficiency of a silicon steel plate transformer and an amorphous transformer. Explanatory drawing of the loss of a silicon steel plate transformer and an amorphous transformer. The perspective view of the amorphous transformer which attached the temperature sensor. Explanatory drawing of the lifetime curve of a transformer. The operation | movement flowchart of the power conditioner of this invention Example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  Example 1 of the present invention will be described. FIG. 1 shows a typical system configuration example of photovoltaic power generation. The DC output power generated by the photovoltaic power generation module 1 is once combined into a single connection box 3 via the DC power transmission unit 2 and converted into AC power by the power conditioner 4. The power is connected to the commercial system 6 via the AC power transmission unit 5.

  FIG. 2 is an explanatory diagram for explaining the internal configuration of the power conditioner 4 in the present embodiment. DC power generated by the plurality of solar power generation modules 1 is converted into AC power by the inverter unit 7. The converted AC power is shaped into a sine wave through the filter unit 8, transformed into a system voltage by the transformer 9, and supplied to the commercial power supply system 6. CT is an instrument current transformer that detects the output current of the inverter 7 and feeds it back to the control unit 21. PT is a meter transformer that detects the voltage of the commercial power supply system 6 and feeds it back to the control unit 21. 10 is the power condition. A cooling fan unit 11 for cooling the inside of the na 4 and a temperature measuring unit 11 for detecting the temperature in the power conditioner 4.

  The control unit 21 includes a PLC (programmable logic controller) and a control circuit for the inverter 7, and includes an inverter 7 drive / stop operation control function, a photovoltaic power generation PMMT (maximum power point tracking) function, and a display / monitor function. I have. Further, temperature information from a temperature sensor 18 provided in a transformer 9 described later is input.

  Next, the transformer 9 mounted on the power conditioner 4 in the present embodiment will be described. The transformer 9 has its own loss, and the greater this loss, the lower the conversion efficiency as the power conditioner 4, which hinders high efficiency.

  FIG. 3 shows an example (experiment) of annual accumulated power generation in each output band of the photovoltaic power generation system. According to this experiment, it can be seen that in the vicinity of the rated output band of 90 to 100%, only a small amount of power is generated annually, and that the power generation in the output band of 30% to 70% is the largest. In FIG. 3, the horizontal axis represents the ratio of the output of the photovoltaic power generation system when the rated output = 100%, and the vertical axis represents the amount of power generation (kWh). In this experiment, the generated power exceeded 12000 kWh in the output band of 30% to 70%, and the power generation amount was 2000 kWh in 90% to 100% close to the rated output. In this way, in solar power generation, the amount of power generation in the output band (partial load region) below the rated output is large, so if the load efficiency can be improved especially in this part, the power generation amount of the entire system will be increased. As a result, an efficient solar power generation system can be realized.

  Therefore, in this embodiment, an amorphous transformer is adopted. Thereby, the improvement in the above-mentioned partial load area | region is aimed at with respect to the transformer of the silicon steel plate employ | adopted as the conventional power conditioner.

  FIG. 4 shows an example of the characteristics of the silicon steel plate transformer and the amorphous transformer. The load factor on the horizontal axis corresponds to the output band in FIG. Reference numeral 14 indicated by a broken line indicates a conversion efficiency curve of the silicon steel sheet transformer, and the efficiency in a band with a small load factor is substantially the same as that at the rated output. On the other hand, in the case of the conversion efficiency curve 13 of the amorphous transformer indicated by the solid line, the conversion efficiency in the band where the load factor is small is higher than that at the rated output. The load factor is the ratio of the current output to the rated output (load factor 100%). The vertical axis shows the conversion efficiency of the transformer. In FIG. 4, it can be seen that when the load factor is around 40% to 50%, the efficiency of both transformers is about 98%, which is reversed.

  FIG. 5 shows an example of loss due to characteristics of a silicon steel plate transformer and an amorphous transformer. The horizontal axis shows the load factor. 15 indicated by a broken line indicates a loss curve with respect to the load factor of the silicon steel plate transformer, and 16 indicated by a solid line indicates a loss curve with respect to the load factor of the amorphous transformer. In FIG. 5, it can be seen that the loss of both transformers is reversed at a load factor of 40% to 50%. Moreover, it turns out that the loss in this case is about 500W.

  In this embodiment, an amorphous transformer having a loss of 500 W or less when a transformation operation is performed at a load factor of 40% or less is adopted. Therefore, the amorphous transformer can reduce loss at a low load factor (low output). Therefore, as described above, in solar power generation, low output power generation increases, so that the loss at this time can be reduced, and as a result, a power conditioner that contributes to an efficient solar power generation system can be realized. .

  Thus, when selecting a transformer as a power conditioner from the difference in efficiency when adopting each transformer of silicon steel plate and amorphous transformer, by installing an amorphous transformer, partial load A highly efficient power conditioner can be provided.

  However, in order to use an amorphous transformer, it must be a transformer that can withstand DC bias and harmonics. In the case of an amorphous transformer, since it is known that it has higher resistance to harmonics than that of a silicon steel-iron transformer, it is sufficient to take measures against direct current bias. The DC bias is a phenomenon that occurs when the DC component is superimposed on the output current of the inverter, and is balanced by generating the DC component from the exciting current of the transformer core. At this time, the loss of the transformer core increases abnormally, and the heat generation increases to impair the life of the equipment. Further, when left in a heat generation state, the temperature of the entire power conditioner 4 is also raised, which affects the life of the built-in equipment.

  In the case of a silicon steel plate transformer, it is possible to withstand DC bias on the transformer side by performing a process (such as forming a gap in the iron core) that increases the resistance to DC bias. However, the loss is increased, which is not preferable. In the case of an amorphous transformer, due to the thickness (thinness) of the amorphous foil material, it is difficult to process the transformer so that it can withstand DC bias.

  The DC bias is thought to be caused by an abnormality in the current transformer CT (Current Transformer) used for control by the inverter and the magnetization due to the inrush current of the transformer, and the frequency is low. Therefore, in the present embodiment, an amorphous transformer is used while detecting the DC bias and stopping the temporary operation to secure the power conditioner 4.

  When DC magnetism occurs, the iron core loss increases and the iron core generates heat abnormally. In this embodiment, a temperature sensor is attached to the iron core of the amorphous transformer, and DC magnetism is detected when the iron core temperature rises abnormally. I am doing so. As the temperature sensor, one that measures the iron core temperature or one that measures the iron core temperature and operates at a high temperature is provided. In FIG. 6, 17 is a wound iron core formed by winding a number of amorphous foils, 17 a is a winding wound around the wound iron core 17, and 18 is a temperature sensor fixed to the outer surface above the wound iron core 17. is there.

  The temperature information of the temperature sensor 18 is input to the control unit 21 as shown in FIG. 2, and the control unit 21 controls the operation of the inverter 3 based on the temperature information. A specific control operation is shown in FIG. After the start of operation of step (S) 100, when the occurrence of DC bias continues continuously, the amorphous iron core 17 generates heat, and when the surface of the iron core reaches a preset abnormal temperature, the abnormal temperature is detected in S200 as a temperature sensor. 18 is detected, and the controller 21 stops the operation of the inverter 7 in S300. Then, after cooling by the cooling fan part 10 etc. by S500, it returns to S100 and a driving | operation is restarted. When the operation is resumed, there is no DC bias and normal operation is performed.

  In this way, it is possible to take measures against DC demagnetization with a simple configuration of detecting the surface temperature of the amorphous iron core and temporarily stopping the operation of the inverter. An amorphous transformer can be used in an efficient state without the need for a structure that can withstand DC bias.

  A second embodiment of the present invention will be described. Also in the power conditioner of the present embodiment, an amorphous transformer is mounted as in the first embodiment. As described in the first embodiment, the conversion (transformation) efficiency can be increased particularly when the amorphous transformer is used in a power conditioner for photovoltaic power generation.

  If a transformer is used, continuous operation is possible at the beginning of the occurrence of DC magnetism, but if the DC magnetism continues, the iron core will gradually rise in temperature and become abnormally hot, which may impair the life of the equipment. . Also in this embodiment, the temperature of the iron core 17 of the amorphous transformer is measured by the sensor 18, and the control unit 21 is controlled to temporarily stop the operation of the inverter 7 at an abnormally high temperature.

  In this embodiment, when the abnormal temperature information from the sensor 18 is input to the control unit 21, the number of occurrences of the abnormal temperature is integrated by the control unit 21, and the lifetime corresponding to the lifetime data preset in the control unit 21. The number of times and the integrated value are compared, and the remaining life is displayed by the difference. Therefore, it is possible to replace the device before reaching the device life, and it is expected that the maintainability is improved.

  A specific control operation is shown in FIG. After the start of operation in step (S) 100, the amorphous iron core 17 generates heat if the occurrence of DC bias is continued. When the surface of the iron core reaches a preset abnormal temperature, this abnormal temperature is determined in S200, and the control unit 21 stops and controls the operation of the inverter 7 in S300. At the same time, the control unit 21 adds the current stop to the previous stop count and stores it. In S400, the control unit 21 determines whether the integrated value is a specified value (number of times close to the life), and if the specified number has been reached, the remaining life period is displayed in S600. If not, after cooling is performed by the cooling fan unit 10 or the like in S500, the operation is resumed by returning to S100. When the operation is resumed, there is no DC bias and normal operation is performed.

  FIG. 7 shows the relationship between the temperature and life of the transformer. In the case of normal (normal) operation, the device life is determined by the life curve 19. However, when abnormal temperatures occur frequently, the device life is shifted and shortened as shown by the life curve 20. Therefore, the shift amount (specified value) due to the number of occurrences of abnormality is set and stored in the control unit 21 in advance, and the remaining life period of the transformer 9 is calculated (predicted) when the accumulated number of occurrences of abnormality approaches the specified value. Display on the control unit 21. This display makes it possible to replace the transformer before destruction and provide a power conditioner with excellent maintainability.

  In the power conditioner 4, there are a capacitor, a wiring cable, and the like constituting the filter 8 that are considered to have a limited life other than the transformer. When the abnormal temperature generation time is short, the life is not seriously affected. However, when the abnormal temperature is continued for a certain time, the influence cannot be ignored. Similarly, capacitors, wiring cables, etc. are also effective because the life curve shifts and the equipment life is shortened by the amount of abnormal temperature.

  As described above, in this embodiment, it is possible to provide a power conditioner with excellent maintainability by predicting the life of the transformer used in the photovoltaic power generation system.

DESCRIPTION OF SYMBOLS 1 ... Solar power generation module part 2 ... DC power transmission part 3 ... Connection box part
4 ... Power conditioner section
5 ... AC power transmission section
6 ... Commercial power system
7… Inverter part
8 ... Filter section
9 ... Transformer (amorphous transformer)
10 ... Cooling fan
11 ... Temperature measurement unit
12 ... 10kW solar power generation system annual cumulative power generation by output band
13 ... Amorphous transformer conversion efficiency
14 ... Silicon steel plate transformer conversion efficiency
15 ... Silicon steel plate transformer loss
16 ... Amorphous transformer loss
17 ... Amorphous transformer core 18 ... Temperature sensor 19 ... Normal transformer life curve 20 ... Transformer life curve 21 when an abnormality occurs ... Control section.

Claims (4)

In a power conditioner that generates AC power by converting DC power from a photovoltaic power generation module with an inverter,
An amorphous transformer that transforms the AC voltage converted by the inverter into a system voltage, a temperature sensor that is fixed to the surface of the iron core of the amorphous transformer and detects the temperature of the iron core, and is detected by the temperature sensor A power conditioner comprising: a control unit that controls the operation of the inverter by detecting a direct-current bias in the amorphous transformer based on the temperature that is set. 2. The power conditioner according to claim 1, wherein the control unit controls the operation of the inverter to stop when the temperature sensor reaches a predetermined temperature and to restart the operation when the temperature decreases. A power conditioner. In a power conditioner that generates AC power by converting DC power from a photovoltaic power generation module with an inverter,
An amorphous transformer that transforms the alternating voltage converted by the inverter into a system voltage, a temperature sensor that detects an internal temperature of the amorphous transformer, and a temperature sensor that detects the internal temperature of the amorphous transformer. It has a control unit that controls the operation,
The control unit predicts the life of the transformer based on the detected internal temperature of the transformer . 4. The power conditioner according to claim 3, wherein the control unit accumulates the stop time or the number of stops of the inverter and displays a life from a comparison between the accumulated value and preset life data. 5. Na.

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