JP2007014063A - Control method of photovoltaic power generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photovoltaic power generation system which can utilize energy generated from a solar cell effectively by preventing operation of a power converter from being stopped unnecessarily with waveform distortion caused by an extraneous impact. <P>SOLUTION: Period of the AC voltage of a commercial power system is determined by measuring the interval between zero-cross points in the AC voltage of a commercial power system from a photovoltaic power generator connected electrically with the commercial power system and performing interactive operation, and if the period of the AC voltage deviates from a predetermined range, operation of the photovoltaic power generator is stopped. In such a control method of a photovoltaic power generator, when such a case as the period between adjacent zero-cross points is not longer than one eighth of the period of commercial frequency is detected continuously, any one of a plurality of zero-cross points existing in a zero-cross point period detected continuously is regarded as an effective zero-cross point and the period of AC voltage is determined. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for controlling a solar power generation apparatus that converts DC power obtained from a DC power source of a solar battery into AC power, and is electrically connected to the solar battery, a commercial power system, and a load system to perform interconnection operation. It is about.

  A conventional solar power generation device will be described with reference to the drawings.

  FIG. 6 is a schematic configuration diagram of a solar power generation device in a conventional solar power generation system.

  As shown in FIG. 6, in recent years, the DC generated power photoelectrically converted by the solar cell 101 is converted into AC power by the power converter 102 and the converted AC power is supplied to the household load 105 connected thereto. Alternatively, a photovoltaic power generation apparatus 100 that puts power into the commercial power system 104 connected in the same manner and reversely flows through the transformer 103 has been put into practical use.

  Here, the power conversion device 102 orthogonally converts the input DC power into AC power and supplies power to the commercial power system 14 to the reverse power flow or the household load 15. The voltage phase is detected and AC conversion control is performed using PWM control (Pulse Width Modulation) technology or the like at a timing synchronized with the system frequency.

  Further, in the photovoltaic power generation apparatus 100, as described above, the system is connected to the commercial power system 104 and operates in synchronization with the system. However, when an abnormality such as a power failure occurs in the commercial power system 104, Therefore, if the voltage and frequency of the commercial power system 104 are detected by the detection unit 106 and each exceeds a predetermined range, the operation is stopped and the system is disconnected. To work.

  Here, the outline of the frequency detection in the detection unit 106 will be described as an example. The detection unit 106 detects the commercial system voltage having the waveform shown in FIG. 7A, and determines the point (zero cross point) at which the voltage becomes 0 (zero). Dividing into positive voltage and negative voltage areas as a reference, converting to rectangular waves shown in Fig. 7 (b), and measuring the frequency of the system by measuring one period (T) of this rectangular wave It is. Further, if the measured time exceeds a predetermined (t1) range with respect to one period of the commercial frequency (for example, 1/50 second or 1/60 second), it is determined that there is an abnormality. It is well known that phase changes can be detected by the same principle.

  In general, if isolated operation is continued during a power failure, the line in the power failure section becomes charged and there is a risk of electric shock from maintenance personnel. Therefore, a function is required to detect the isolated operation even in a load balance state. . Conventionally, a method of detecting a phase change rate or a frequency change rate of an AC output converted by a power converter, a method of detecting a single operation state by periodically changing reactive power or frequency, and the like have been proposed.

In addition, among them, a method for detecting an isolated operation even when the cycle of the system voltage fluctuates constantly has been proposed (see, for example, Patent Document 1).
JP 2001-286063 A

  However, in the conventional solar power generation apparatus described above, the operating state of the large equipment load 107 and the internal impedance of the transformer 103 connected to the same transformer 103 as shown in FIG. When the impedance due to the wiring from the circuit is high, the system voltage waveform may be disturbed as shown in FIG. 8, and in such an environment, frequency detection cannot be performed normally, leading to erroneous determination. There is. That is, there is a problem that even though there is no abnormality such as a power failure, it is determined that the frequency or phase has changed due to waveform distortion caused by an external influence, and the operation of the power converter is stopped. .

  For this reason, there is a problem that the light energy cannot be fully utilized even though there is sunlight energy.

  In addition, if the system voltage waveform is disturbed as described above, the zero-cross point that is the reference for the sine wave waveform cannot be detected accurately, so that a phase shift from the voltage occurs in the control of the power converter, or the current waveform is disturbed. Thus, there is a problem that harmonics are generated or the operation is stopped.

It should be noted that the system voltage waveform should be stable without any disturbance, and it is a problem that the waveform disturbance is in a state of occurrence / continuation that causes the above-mentioned problems. In order to check the waveform disturbance, a dedicated measuring device is required, and there is a problem that it cannot be easily recognized.

  In order to solve the above-mentioned problem, the control means of the photovoltaic power generation apparatus of the present invention is provided between a photovoltaic power generation apparatus that is electrically connected to a commercial power system and performs interconnection operation, and between the zero cross points of the AC voltage of the commercial power system. By measuring the AC voltage cycle of the commercial power system, and when the cycle of the AC voltage is out of a predetermined range, the control of the photovoltaic power generation device is stopped In the method, a plurality of zero crossings existing within the continuously detected zero cross point period when a period between the zero cross points is continuously detected is 1/8 or less of a period of a commercial frequency. One of the points is regarded as an effective zero cross point, and the period of the AC voltage is obtained.

  Moreover, the control means of the other solar power generation apparatus of the present invention measures between the zero cross points of the AC voltage of the commercial power system from the solar power generation apparatus that is electrically connected to the commercial power system and performs the interconnection operation. The control method of the photovoltaic power generation apparatus is such that the operation of the photovoltaic power generation apparatus is stopped when the period of the alternating voltage of the commercial power system is obtained and the period of the alternating voltage is out of a predetermined range. When the period between the zero cross points is continuously detected as 1/8 or less of the period of the commercial frequency, the substantially middle point of the continuously detected zero cross point period is regarded as an effective zero cross point. Thus, the period of the AC voltage is obtained.

  Moreover, the control means of the other solar power generation apparatus of the present invention measures between the zero cross points of the AC voltage of the commercial power system from the solar power generation apparatus that is electrically connected to the commercial power system and performs the interconnection operation. The control method of the photovoltaic power generation apparatus is such that the operation of the photovoltaic power generation apparatus is stopped when the period of the alternating voltage of the commercial power system is obtained and the period of the alternating voltage is out of a predetermined range. When the period between the zero cross points is 1/8 or less of the commercial frequency period, 2n (n is a natural number, n = 1, 2, 3,...) The (n + 1) th zero cross point within the detected period is regarded as an effective zero cross point, and the period of the AC voltage is obtained.

  Moreover, the control means of the other photovoltaic power generation apparatus according to the present invention uses an average of the AC voltage periods obtained in a plurality of periods of the AC voltage of the commercial power system as the AC voltage period of the commercial power system. It is characterized by doing so.

  Furthermore, the control means of the other photovoltaic power generation apparatus of the present invention is provided with warning means for issuing a warning, and the period between the adjacent zero cross points is 1/8 or less of the period of the commercial frequency. In some cases, the solar power generation device issues a warning when it is continuously detected over a plurality of periods or when the frequency of detection within the same period is high.

  According to the control method of the photovoltaic power generation apparatus of the present invention, even when a distortion such as distortion occurs in the voltage waveform of the commercial power system, the apparatus is unnecessarily stopped without causing an erroneous determination that the system is abnormal. It is possible to prevent this. In addition, this leads to effective use of solar energy.

  Hereinafter, an embodiment of a photovoltaic power generation apparatus according to claim 1 of the present invention will be described in detail based on the drawings schematically shown.

  FIG. 1 is a schematic configuration diagram of a single photovoltaic power generation apparatus for schematically explaining an embodiment of the photovoltaic power generation apparatus according to the present invention, and FIG. 2 is an embodiment of the photovoltaic power generation apparatus according to the present invention. It is a schematic waveform diagram for explaining schematically.

  As shown in FIG. 1, a solar power generation apparatus 10 that performs grid connection operation converts a solar cell 11, DC power generated by the solar cell 11 into AC power, and converts the solar cell 11 into a commercial power system and a load system. Is connected to the commercial power system 14 and the household load 15, and in addition to the solar battery 11 and the power converter 12, the commercial power system 14 And a detection unit 16 that detects the voltage of the commercial power system.

  The detection unit 16 that detects the voltage connected to the commercial power system 14 may be installed in the power conversion apparatus 12, but may be installed in a place different from the power conversion apparatus 12.

  Here, the solar cell 11 is a solar cell module or a solar cell array in which a plurality of solar cell modules are collected, and DC power generated by the solar cell 11 is input to the power conversion device 12. As the solar cell 11, a polycrystalline silicon solar cell, a single crystal silicon solar cell, a thin film solar cell such as amorphous silicon, or the like is preferably used, and a solar cell module in which a plurality of solar cells are collected is further arranged in series and parallel. A solar cell array is generally used.

  The output of the solar cell 11 is input to the power conversion device 12. The power conversion device 12 orthogonally converts the input DC power into AC power using a PWM control technique or the like, and the commercial power system 14 is subjected to reverse power flow or Electric power is supplied to the household load 15.

  On the other hand, the detection unit 16 detects the voltage of the commercial power system 14 (that is, the output voltage of the power converter 12), classifies the voltage into a positive voltage and a negative voltage based on the zero cross point of the voltage, and converts the voltage into a rectangular wave. The frequency of the system is detected by measuring one period (period between two consecutive zero cross points) of this rectangular wave. Further, if this measured time exceeds a predetermined range (t1) with respect to one period of commercial frequency (1/50 second or 1/60 second), it is determined that there is an abnormality. That is, the frequency measurement is the same as the conventional method shown in FIG.

  However, in the control method of the photovoltaic power generation apparatus of the present invention, when the period between two adjacent zero cross points continuously detects a period between zero cross points that is 1/8 or less of the period of the commercial frequency during the measurement, The period of the AC voltage is determined by regarding any one of a plurality of zero cross points existing within a continuously detected zero cross point period as an effective zero cross point, and the period is within the predetermined range. If it is determined that the power conversion device 12 is normal, the power conversion device 12 continues to operate. If the power conversion device 12 is outside the predetermined range, the power conversion device 12 is determined to be abnormal, and the operation of the power conversion device 12 is stopped.

  Moreover, in the control method of the other solar power generation device of the present invention, when continuously detecting the case where the period between two adjacent zero cross points is 1/8 or less of the cycle of the commercial frequency, The period of the AC voltage is calculated by regarding the substantially intermediate point of the detected zero cross point period (for example, a point obtained by dividing the total of the periods by two) as an effective zero cross point, and the period is If it is within the predetermined range, it is determined that it is normal, and the power conversion device 12 continues to operate, and if it is outside the predetermined range, it is determined that it is abnormal, and the operation of the power conversion device 12 is stopped.

  Furthermore, in another method for controlling a photovoltaic power generator of the present invention, 2n cases where the period between the zero cross points is 1/8 or less of the period of the commercial frequency (n is a natural number, n = 1, 2, 3)) When continuously detected, the period of the AC voltage is determined by regarding the (n + 1) th zero-cross point within the continuously detected period as an effective zero-cross point, and the period Is determined to be normal if it is within the predetermined range, the power conversion device 12 continues to operate, and if it is outside the predetermined range, it is determined to be abnormal, and the operation of the power conversion device 12 is stopped. .

  The voltage waveform shown in FIG. 2 will be described in detail as an example. The detection unit 16 detects the voltage waveform of the commercial power system 14 shown in FIG. 2A and detects the voltage waveform from the zero cross point of FIG. 2B. Convert to square wave. The detection unit 16 measures one period of the rectangular wave and detects each of the rectangular wave periods T1, T2, and T3.

  Here, the detection unit 16 starts from measurement (1), and performs measurement (2), measurement (3), and measurement in sequence. However, the measurement frequency is 1 in the period of the commercial frequency as in measurement (2) and measurement (3). If there are consecutive periods of / 8 or less, only the middle zero cross point is valid. Similarly, measurement between measurement (4), measurement (5), measurement (6) and zero cross point is performed, and if there is a period of 1/8 or less, zero cross point invalidation processing is performed.

  Thereby, the waveform of FIG. 2B is converted into a waveform as shown in FIG.

  That is, in FIG. 2, each of the periods T1, T2, and T3 includes a period that is 1/8 or less of the period of the commercial frequency ((2), (3), (5), (6) in FIG. 2B). Therefore, the intermediate zero crossing point between (2)-(3) and (5)-(6) is made valid, and the period of (1)-(5) is regarded as Ta, and the measurement value is judged. Is what you do.

  In the case of FIG. 3, since the cycle Ta of the added AC voltage is within the range of t1, it is determined that it is in the normal range, and the power converter 12 continues to operate. Even when distortion such as distortion occurs in the voltage waveform of the commercial power system, it is possible to prevent the apparatus from being stopped unnecessarily without causing erroneous determination that the system is abnormal.

  Here, the nullification process is performed when the period of the zero cross point is 1/8 or less of the period of the commercial frequency, but this is a distribution line or a column with respect to the impedance of the system (usually 0.38Ω + 0.45mH in the 200V system). It is within the range that can be assumed from the conditions of the upper transformer, and anything beyond this range is not preferable for continuing grid interconnection, such as an abnormality caused by the power converter itself.

  In addition, this invention is not limited to the above-mentioned form, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention, such as the measuring method of a detection period.

  Further, in the present invention, since the zero cross point period of a period of 1/8 or less of the period of the commercial frequency is targeted, it does not affect the above-described prior art single operation detection, and the phase of the system is In the case of a sudden change or the like, it is surely disconnected from the commercial power system by the conventional isolated operation detection function.

  Next, an embodiment of the photovoltaic power generation apparatus according to claim 2 of the present invention will be described with reference to FIG.

  Embodiments of the apparatus configuration and operation in the present invention are the same as those described above. However, when the measured value of the detected frequency period includes a period of 1/8 or less of the commercial frequency period, the determination is performed. An average of a plurality of frequency cycles is taken and used as a reference point for AC conversion by PWM control. In the example in FIG. 4, the average of the three periods of Ta, Tb, and Tc is taken to obtain T ′, which is used as the reference point for the next PWM conversion. This makes it possible to estimate the frequency and voltage phase when the frequency fluctuation in the normal state is small, to eliminate the phase difference from the generated current waveform as much as possible, and to prevent unnecessary operation stop It is.

  In the present invention, the averaging of the three cycles of the waveform has been described as an example. However, if the period is too long, it takes a processing time, and during that time, malfunction may occur and the effect may be impaired. It is desirable to carry out in a period of about five cycles.

  Next, an embodiment of the photovoltaic power generation apparatus according to claim 3 of the present invention will be described with reference to FIG.

  The apparatus configuration in the present invention has a warning generator 17 as shown in FIG. 5 and the embodiment of the operation is the same as that described above, but in the measured value of the period of the detected frequency, 1/8 or less of the period of the commercial frequency. If the period is included, it is detected continuously over a plurality of periods, or when it is determined that the frequency of detection within the same period is high, the warning generating unit 17 issues an alarm or warning display, etc. is there.

  As described above, the disturbance of the system voltage waveform is not desirable, and should be stable without any disturbance. Therefore, it is possible to recognize that a disturbance has occurred in the system voltage waveform, and measures such as improvement of the system impedance and removal of disturbance factors can be achieved.

  It should be noted that in the continuous period including a period of 1/8 or less of the period of the commercial frequency in the present invention, it is desirable that it is about several minutes to several tens of minutes, and the frequency is about 1/2 or more of the whole, The present invention is not limited to the above-described embodiment, and various changes and the like can be made without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic apparatus block diagram for demonstrating typically the embodiment of the solar power generation device which concerns on this invention. (A), (b) is a schematic wave form diagram for demonstrating embodiment of the solar power generation device which concerns on this invention, (a) is a waveform of a commercial power grid, (b) is after detection It is a waveform. It is a schematic waveform diagram for demonstrating typically the embodiment of the solar power generation device concerning the present invention. It is a schematic waveform diagram for demonstrating typically the embodiment of the other solar power generation device which concerns on this invention. It is a schematic apparatus block diagram for demonstrating typically the embodiment of the other solar power generation device which concerns on this invention. It is a schematic block diagram in the conventional solar power generation device. (A), (b) is a schematic waveform diagram for demonstrating typically the embodiment of the conventional solar power generation device, (a) is a waveform of a commercial power grid, (b) is a waveform after detection. It is. It is a schematic wave form diagram for demonstrating typically the embodiment of the conventional solar power generation device.

Explanation of symbols

10: Solar power generation device 11: Solar cell 12: Power conversion device 13: Transformer 14: Commercial power system 15: Home load 16: Detection unit 17: Warning generation unit 100: Solar power generation device 101: Solar cell 102: Power converter 103: Transformer 104: Commercial power system 105: Household load 106: Detection unit 107: Equipment load

Claims (5)

A cycle of the AC voltage of the commercial power system is obtained by measuring a zero-cross point of the AC voltage of the commercial power system from a photovoltaic power generation apparatus that is electrically connected to the commercial power system and performs interconnection operation. When the voltage cycle deviates from a predetermined range, the photovoltaic power generation device control method is configured to stop the operation of the photovoltaic power generation device, wherein a period between adjacent zero cross points is a commercial frequency cycle. When continuously detecting a case of 1/8 or less, the AC voltage is regarded as one of a plurality of zero cross points existing within the continuously detected zero cross point period as a valid zero cross point. A method for controlling a photovoltaic power generation apparatus, characterized in that the period of the solar power generation is obtained. A cycle of the AC voltage of the commercial power system is obtained by measuring a zero-cross point of the AC voltage of the commercial power system from a photovoltaic power generation apparatus that is electrically connected to the commercial power system and performs interconnection operation. When the voltage cycle deviates from a predetermined range, the photovoltaic power generation device control method is configured to stop the operation of the photovoltaic power generation device, wherein a period between adjacent zero cross points is a commercial frequency cycle. When continuously detecting a case of 1/8 or less, the period of the AC voltage is obtained by regarding a substantially middle point of the continuously detected zero cross point period as an effective zero cross point. The control method of the solar power generation device. A cycle of the AC voltage of the commercial power system is obtained by measuring a zero-cross point of the AC voltage of the commercial power system from a photovoltaic power generation apparatus that is electrically connected to the commercial power system and performs interconnection operation. When the voltage cycle deviates from a predetermined range, the photovoltaic power generation device control method is configured to stop the operation of the photovoltaic power generation device, wherein a period between adjacent zero cross points is a commercial frequency cycle. When 2n cases (n is a natural number, n = 1, 2, 3,...) Are continuously detected when the number is 1/8 or less, the (n + 1) -th zero cross in the continuously detected period. A method for controlling a photovoltaic power generation apparatus, wherein a point is regarded as an effective zero cross point and the period of the AC voltage is obtained. 4. The AC voltage cycle of the commercial power system is defined as an average of the AC voltage cycles respectively obtained in a plurality of cycles of the AC voltage of the commercial power system. 5. The control method of the solar power generation device of description. The solar power generation device includes warning means for issuing a warning, and when the period between the adjacent zero cross points is 1/8 or less of the cycle of the commercial frequency, it is continuously detected over a plurality of cycles, or the same The method for controlling a solar power generation device according to any one of claims 1 to 4, wherein the solar power generation device issues a warning when a detection frequency within a cycle is high.

Images