JP2011188690A - Islanding detection device of inverter and method of detecting islanding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an islanding detection device which detects islanding of an inverter earlier, and also to provide a method of detecting the islanding. <P>SOLUTION: The islanding detection device includes: an abnormal-condition detection unit which is configured to detect an abnormal frequency f or frequency variation rate df/dt from the voltage of AC power output from an AC power system 8 and an inverter 2; a frequency detection unit 28 which detects the frequency f of an AC voltage output from the AC power system 8 and the inverter 2; a moving average means 29 for calculating the moving average fm from the frequency f detected by the frequency detection unit 28; a frequency deviation means 30 for operating the frequency deviation Δf from the frequency f and the moving average fm; a function means 31 for calculating the value of reactive power Q by the characteristic function of reactive power Q for the frequency deviation ▵f, according to the magnitude and polarity of the frequency deviation Δf, and output it; and a drive unit which controls output power of the inverter 2 by using the output of the function means 31 and stops the inverter 2 when abnormal-condition is detected from the abnormal-condition detection unit. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to isolated operation protection when an inverter is connected to a grid, and to an isolated operation detection device and an isolated operation detection method for an inverter.

  A configuration example of the isolated operation detection device is shown in FIG. 6 and the configuration, operation, and conditions will be described. As shown in FIG. 6, in a conventional inverter single-operation detection device, for example, DC power output from a DC power source 1 including a solar cell or a fuel cell is converted into AC power by an inverter bridge 2, and a reactor 3 A high frequency component by PWM (Pulse Width Modulation) control is removed by a filter comprising the capacitor 4 and supplied to the load 9 via the contactor 6.

On the other hand, the inverter bridge 2 operates in conjunction with AC power supplied from the AC power system 8 via the circuit breaker 7. The AC voltage of the AC power supplied to the load 9 is detected by the voltage detector 10 and supplied to a PLL (Phase-locked loop) circuit 22. The PLL circuit 22 inputs a signal V ₂₂ synchronized with the AC voltage phase to the phase shift circuit 23, and the sine wave signal V _s is input to the current reference circuit 12 through the sine wave circuit 26.

The amplifier 11 detects the voltage V of the DC power source 1 and inputs a signal V ₁₁ obtained by amplifying the difference compared with the voltage reference V ^* to the current reference circuit 12. The current reference circuit 12 inputs the product of the signal V ₁₁ and the signal V _s to the amplifier 13 as an alternating current reference I ^* . The amplifier 13 controls the AC current reference I ^* and the inverter output current detected by the current detector 5 to coincide with each other, and the PWM circuit 14 performs PWM control of the inverter bridge 2 via the drive circuit 15.

Meanwhile PLL circuit inverter bridge 2 by shifting the phase of the output signal V _s of the sine wave circuit 26 by the phase shift circuit 23 through the function generating circuit 24 detects the inverter frequency by the frequency detection circuit 25 from the output signal V ₂₂ of 22 Output reactive power (I × Vsin θ).

  The AC voltage detected by the voltage detector 10 is supplied to the voltage relay 17, the frequency relay 18, and the frequency change rate relay 27. The voltage relay 17 detects a voltage abnormality from the AC voltage supplied to the load 9. The frequency relay 18 detects a frequency abnormality from the AC voltage supplied to the load 9. The frequency change rate relay 27 detects an excessive frequency change rate (df / dt) from the AC voltage supplied to the load 9.

If an abnormality is detected, a signal notifying the abnormality is supplied to the drive circuit 15 via the abnormality detection circuit 19, and the drive circuit 15 stops the inverter drive and simultaneously opens the contactor 6 to completely invert the inverter. The bridge 2 is disconnected from the grid connection (see, for example, Patent Document 1 and Patent Document 2).
Japanese Patent No. 2790403 Japanese Patent No. 2796035

The isolated operation detection method as described above is called “slip mode frequency shift”. This operation principle will be described with reference to FIG. As shown in the inverter characteristics of FIG. 7, the function generating circuit 24 has a current phase that increases in the forward direction (advance reactive power) as the frequency (f) increases near the rated frequency f ₀ with respect to the inverter output frequency (f). It is a characteristic.

On the other hand, when the frequency (f) increases, the capacitor 9 increases the capacitor current and decreases the reactor current when the frequency (f) increases, so that the characteristic curve of the load 9 increases with increasing frequency (f) and absorbs reactive power. The load characteristic of FIG. 7 shows a characteristic curve when the load 9 is the rated frequency f ₀ and the power factor = 1. In this state, when the circuit breaker 7 is opened under the condition that the active power ΔP and the reactive power ΔQ flowing to the AC power system 8 are both zero, it takes a relatively long time to detect the isolated operation.

When the breaker 7 is opened at the point of the rated frequency f ₀ where the active power is zero (ΔP = 0) and the reactive power is zero (ΔQ = 0), the load 9 absorbs in the frequency range higher than the rated frequency f _0. Since the advanced reactive power output from the inverter bridge 2 is slightly larger than the reactive power to be performed, the frequency (f) increases because the load 9 absorbs the advanced reactive power.

On the other hand, since the delayed reactive power output from the inverter bridge 2 is larger than the delayed reactive power absorbed by the load 9 in the range of the frequency (f) lower than the rated frequency f ₀ , the frequency of the load 9 ( f) decreases (reactor current increases).

  In such a process, the frequency (f) is accelerated and shifted by positive feedback. However, as shown in FIG. 8, the reactive power output from the inverter bridge 2 and the reactive power absorbed by the load 9 are equal. If the single operation is performed under the condition (the active power is also equal), the detection of the single operation of the inverter is delayed. FIG. 8 is a simulation waveform under the condition that the reactive power output from the inverter bridge 2 and the reactive power absorbed by the load 9 are equal (active power is also equal).

  Conventionally, for example, it is a grid connection rule that only needs to be detected in about 0.5 to 1.0 seconds after becoming an independent operation, but recently it is desired to detect in 0.1 seconds for protection coordination of the system. It became so. If the slope of the inverter characteristic is made steep while maintaining the reactive power or current phase angle characteristic of the inverter bridge 2 with respect to the frequency shown in FIG. 7 (if the crossing angle A between the inverter characteristic and the load characteristic is increased). The positive feedback is strong and the detection time is fast, but when the frequency changes by ± 1%, there is a limit of 95% or more in the power interconnection regulation, and there is a limit to shortening the time.

  The present invention has been made in view of these circumstances, and an object of the present invention is to provide an isolated operation detection device and an isolated operation detection method for detecting an isolated operation of an inverter earlier even in the above-described state. There is to do.

  An independent operation detection device for an inverter according to a first aspect of the present invention is an independent operation detection device for an inverter that converts DC power into AC power and operates in conjunction with an AC power system, the AC power system and An abnormality detector configured to detect an abnormality in frequency or frequency change rate from a voltage of AC power output from the inverter, and a frequency of the AC voltage output from the AC power system and the inverter. A frequency detecting unit; a moving average unit that calculates a moving average of the frequency from the frequency detected by the frequency detecting unit; a frequency deviation unit that calculates a frequency deviation from the frequency detected by the frequency detecting unit and the moving average; According to the characteristic function of the reactive power with respect to the frequency deviation, according to the magnitude and polarity of the frequency deviation, Function means for calculating and outputting the value of reactive power or phase angle so that the reactive power flows when the frequency deviation is positive, and the reactive reactive power flows when the frequency deviation is negative. And a drive unit that controls the output power output from the inverter using the output of the function means, and that stops the inverter when an abnormality is detected from the abnormality detection unit. It is a detection device.

  An independent operation detection device for an inverter according to a second aspect of the present invention is an independent operation detection device for an inverter that converts DC power into AC power and operates in conjunction with an AC power system. An abnormality detector configured to detect an abnormality in frequency or frequency change rate from a voltage of AC power output from the inverter, and a frequency of the AC voltage output from the AC power system and the inverter. A frequency detection unit, a moving average unit that calculates a moving average of the frequency from the frequency detected by the frequency detection unit, a frequency change rate unit that calculates a frequency change rate from the frequency detected by the frequency detection unit, and A frequency deviation means for calculating a frequency deviation from the frequency detected by the frequency detector and the moving average; When the sum of the frequency deviation and the frequency change rate is positive, the advance reactive power flows, and when the sum of the frequency deviation and the frequency change rate is negative, the delayed reactive power flows and the sum of the frequency deviation and the frequency change rate According to the characteristic function of the reactive power with respect to the function unit, the function unit comprising: calculating and outputting the value of the reactive power or the phase angle according to the magnitude and polarity of the sum of the frequency deviation and the frequency change rate; An isolated operation detection apparatus comprising: a drive unit that controls output power of the inverter using an output from a function unit and stops the inverter when an abnormality is notified from the abnormality detection unit.

  An independent operation detection method for an inverter according to a third aspect of the present invention is a method for detecting an independent operation of an inverter that converts DC power into AC power and operates in conjunction with an AC power system. The frequency of the AC voltage output from the inverter is detected, the moving average of the frequency is calculated from the detected frequency, the frequency deviation is calculated from the detected frequency and the moving average, and when the frequency deviation is positive When the reactive power flows, and when the frequency deviation is negative, the reactive power characteristic function with respect to the frequency deviation in which the delayed reactive power flows, the value of the reactive power or the phase angle is calculated according to the magnitude and polarity of the frequency deviation, Using the calculated reactive power or phase angle value to control the output power output from the inverter, the AC power system and From the voltage of the AC power output from the serial inverter detects whether a frequency or frequency change rate abnormality is isolated operation detecting method for stopping said inverter when the abnormality of the frequency or frequency change rate is detected.

  An independent operation detection method for an inverter according to a fourth aspect of the present invention is a method for detecting an independent operation of an inverter that converts direct current power into alternating current power and operates in conjunction with an alternating current power system, the alternating current power system and The frequency of the alternating voltage output from the inverter is detected, the moving average of the frequency is calculated from the detected frequency, the frequency change rate is calculated from the detected frequency, and the frequency deviation is detected from the detected frequency and the moving average. When the sum of the frequency deviation and the frequency change rate is positive, advance reactive power flows, and when the sum of the frequency deviation and the frequency change rate is negative, the frequency deviation flows when delayed reactive power flows. And the reactive power characteristic function for the sum of the frequency change rate and the reactive power according to the magnitude and polarity of the sum of the frequency deviation and the frequency change rate. Alternatively, the phase angle value is calculated, the output power output from the inverter is controlled using the calculated reactive power or phase angle value, and the AC power system and the AC power voltage output from the inverter are controlled. From this, it is an isolated operation detection method that detects whether the frequency or the frequency change rate is abnormal and stops the inverter when the frequency or the frequency change rate is abnormal.

  ADVANTAGE OF THE INVENTION According to this invention, the isolated operation detection apparatus and isolated operation detection method which detect the isolated operation of an inverter earlier can be provided.

It is a figure for demonstrating one structural example of the independent operation detection apparatus of the inverter which concerns on 1st Embodiment of this invention. It is a figure which shows an example of an inverter characteristic (the reactive power or current phase angle with respect to frequency deviation (DELTA) f). It is a figure which shows an example of an inverter characteristic (the reactive power or current phase angle with respect to frequency deviation (DELTA) f). It is a figure which shows an example of an inverter characteristic (the reactive power or current phase angle with respect to frequency deviation (DELTA) f). It is a figure for demonstrating the example of 1 structure of the independent operation detection apparatus of the inverter which concerns on 2nd Embodiment of this invention. It is a figure which shows an example of the characteristic curve of the frequency of the moving average by a frequency and a phase angle, or a frequency and reactive power. It is a figure for demonstrating the example of 1 structure of the independent operation | movement detection apparatus of the inverter which concerns on 3rd Embodiment of this invention. It is a figure for demonstrating the example of 1 structure of the conventional isolated operation detection apparatus. It is a figure which shows an example of the inverter characteristic and load characteristic of the conventional independent operation detection apparatus. It is a figure for demonstrating an example of operation | movement of the conventional isolated operation detection apparatus.

  Hereinafter, an isolated operation detection device and an isolated operation detection method for an inverter according to an embodiment of the present invention will be described with reference to the drawings. An isolated operation detection device according to an embodiment is an isolated operation detection protection device for an inverter that converts direct current power output from a direct current power source into alternating current power and operates in conjunction with an alternating current system. The voltage phase, frequency, and moving average of the frequency are detected, the reference phase is obtained from the detected voltage phase, the current reference of the system current of the phase according to this reference phase is generated, and the output current of the inverter is controlled In addition, the reference phase is corrected in accordance with the difference between the frequency and the moving average of the frequency (frequency deviation), thereby detecting that the inverter is disconnected from the AC system and performing the protection operation at high speed. ing.

  As shown in FIG. 1, the inverter independent operation detection device according to the first embodiment of the present embodiment synchronizes the voltage phase of the output power of the AC power system and the inverter, and controls the output current to a predetermined current phase. The reactive power of the inverter output is controlled. Further, when the inverter is disconnected from the AC power system, the inverter is driven so that the reactive power of the inverter changes based on the frequency of the output voltage of the inverter.

  Furthermore, the characteristic curve of reactive power with respect to the frequency is moved so that the reactive power becomes almost zero following the normal frequency change (steady state) sufficiently, and the frequency is positively fed back to the fast frequency change (abnormal state). To control the direction to promote the change.

  The isolated operation detection device according to the present embodiment detects an isolated operation of the inverter bridge 2 that converts direct current power of a direct current power source 1 including, for example, a solar cell or a fuel cell into alternating current power. The AC power output from the inverter bridge 2 is removed of high frequency components by PWM control by a filter including a reactor 3 and a capacitor 4, and supplied to a load 9 via a contactor 6.

The inverter bridge 2 is operated in conjunction with AC power supplied from the AC power system 8 via the circuit breaker 7. The AC voltage supplied to the load 9 is detected by the voltage detector 10 and supplied to the PLL circuit 22. The PLL circuit 22 inputs a signal V ₂₂ synchronized with the AC voltage phase to the phase shift circuit 23, and the sine wave signal V _s is input to the current reference circuit 12 through the sine wave circuit 26.

The amplifier 11 detects the voltage of the DC power source 1, compares it with the voltage reference V ^*, and inputs a signal V ₁₁ obtained by amplifying the difference to the current reference circuit 12. The current reference circuit 12 inputs the product of the signal V ₁₁ and the signal V _s to the amplifier 13 as an alternating current reference I ^* . The amplifier 13 controls the AC current reference I ^* and the output current of the inverter bridge 2 detected by the current detector 5 to coincide with each other, and the PWM circuit 14 performs PWM control of the inverter bridge 2 via the drive circuit 15.

On the other hand, the frequency f of the output voltage of the inverter bridge 2 is detected by the frequency detection circuit 28, and the phase of the output signal V _s of the sine wave circuit 26 is shifted by the phase shift circuit 23 via the function unit 100 to invalidate the output of the inverter. The power (I × Vsin θ) is controlled.

  In the present embodiment, the amplifier 11, the current reference circuit 12, the amplifier 13, the PWM circuit, the drive circuit 15, the PLL circuit 22, the phase shift circuit 23, and the sine wave circuit 26 output an output from the function unit 100 described later. It is a drive unit that controls the output power of the inverter bridge 2 and stops the inverter bridge 2 when an abnormality is notified from the abnormality detection unit.

The function unit 100 is supplied with the inverter frequency f output from the frequency detection circuit 28, calculates the moving average fm from the frequency f, and outputs it. The function unit 100 is supplied with the frequency f and the moving average fm. A phase shift frequency deviation circuit 30 that calculates a frequency deviation Δf based on a difference from the moving average fm, and an output signal (reactive power) by a function of the reactive power Q (or current phase angle θ) with respect to the frequency deviation Δf supplied with the frequency deviation Δf And a function circuit 31 for calculating Q or the value of the current phase angle θ. The signal V ₃₁ output from the function circuit 31 is supplied to the phase shift circuit 23.

  The AC voltage detected by the voltage detector 10 is supplied to the voltage relay 17, the frequency relay 18, and the frequency change rate relay 27. The voltage relay 17 detects a voltage abnormality from the AC voltage supplied to the load 9. The frequency relay 18 detects a frequency abnormality from the AC voltage supplied to the load 9. The frequency change rate relay 27 detects an excessive frequency change rate (df / dt) from the AC voltage supplied to the load 9.

  When an abnormality is detected, a signal for notifying the drive circuit 15 of the abnormality is supplied via the abnormality detection circuit 19, and the drive circuit 15 stops the inverter drive, and at the same time, a signal output from the abnormality detection circuit 19 Thus, the contactor 6 is opened to completely disconnect the inverter bridge 2 from the grid connection.

  In the isolated operation detection device according to the present embodiment, when the AC side of the inverter bridge 2 is disconnected from the AC power system, the frequency f on the AC power system 8 side slightly increases or decreases from the moving average fm of the frequency f. That is, if a value obtained by subtracting the moving average fm from the frequency f is defined as a frequency deviation Δf (f−fm = Δf), the frequency f is the sum of the moving average fm and the frequency deviation Δf (f = fm + Δf).

  In this case, the average time of the moving average fm is set longer than the isolated operation detection target time. In the present embodiment, the average time of the moving average fm is set to be five times or more the isolated operation detection target time. For example, when the isolated operation detection target time is set to 100 ms, the average time of the moving average fm is set to be five times or more of 100 ms, that is, 500 ms or more. The moving average fm is the average value of the frequency f detected in the average time, and when the average time is t, the moving average fm is the sum of the frequencies f detected during the average time t at the average time t. Divided value.

  In the isolated operation detection apparatus shown in FIG. 1, the frequency f of the AC power system is detected by the frequency detection circuit 28, the moving average fm of the frequency is calculated by the moving average circuit 29, and the frequency deviation Δf by the phase shift frequency deviation circuit 30. Is obtained from Δf≈f−fm, and is a function of the phase characteristic of the reactive power Q as shown in FIG. 2A, for example, by the function circuit 31, and the reactive power Q with respect to the frequency deviation Δf output from the frequency circuit 31 by the phase shift circuit 23. The phase is shifted based on (or the current phase angle θ). Based on the shifted phase, the sine wave circuit 26 outputs a sine wave Vs, and the current reference circuit 12 corrects the current phase angle θ of the alternating current output from the inverter bridge 2 of the current reference I *. In this manner, the current phase angle θ is corrected, and the reactive power Q of the inverter bridge 2 is controlled so as to have the phase characteristics shown in FIG. 2A.

  That is, the reactive power of the output power of the inverter bridge 2 or the current phase angle of the inverter bridge 2 proceeds according to the reactive power characteristic function shown in FIG. 2A when the frequency deviation Δf is positive (+). When the deviation Δf is negative (−), the delay reactive power is controlled to flow.

  As described above, when the frequency deviation Δf increases (+), the reactive power is advanced and positive feedback is applied to further increase the frequency f. When the frequency deviation Δf decreases (−), a delayed reactive power is supplied, and the frequency f is rapidly shifted by applying positive feedback so as to further decrease the frequency f.

  As described above, when the current phase characteristic with respect to the frequency f changes by ± 1% with respect to the rated frequency, it is specified that the power factor is 95% or more, so the upper limit value of the slope of the phase characteristic curve Is limited, and the speed of the frequency shift is limited. On the other hand, when the isolated operation detection device and the isolated operation detection method shown in FIG. 1 are used, the current phase angle is almost zero and the power factor is close to 1 in the steady state. As a result, the slope of the characteristic function of the output reactive power or current phase angle can be abruptly increased.

  Here, if 100 ms is set as the target (target time) as the isolated operation detection time, the frequency f is shifted by about 40 to 80 ms, and the remaining one cycle 20 ms is set as a time for confirming that the frequency f has changed. Is possible.

  Therefore, if the moving average time of the frequency f is about 500 ms, the frequency change between 40 and 80 ms can be suppressed to about 1/10 with the moving average fm of the frequency f, and the power factor in the steady state is almost 1. can do. As a result, the gain of the positive feedback can be increased, so that high-speed frequency shift is possible, high power factor performance is maintained during steady state, and high-speed islanding detection of about 100 ms can be realized. .

  That is, in the isolated operation detection device and the isolated operation detection method of the inverter according to the present embodiment, the frequency deviation Δf (f−fm = Δf), which is the difference between the frequency f and the moving average fm, is steadily applied. Since f−fm≈0, there is no need to consider the current phase angle θ in the steady state, so the slope of the characteristic function of the current phase angle θ (or reactive power Q) with respect to the frequency deviation Δf is abruptly (large). Then, the gain of the positive feedback action is increased to shift the frequency f at high speed.

  When the frequency f shifts, a frequency abnormality is detected by the frequency relay 18 from the output of the voltage detector 10, and an excessive frequency change rate (df / dt) is detected by the frequency change rate relay 27.

  As described above, when the frequency change rate (df / dt) or the addition value of several times of the frequency change rate (df / dt) is detected, the gate of the drive element (not shown) of the inverter bridge 2 is When the frequency f is excessively high, the frequency f is excessively low, the voltage of the inverter bridge 2 is excessively high, and / or the voltage of the inverter bridge 2 is excessively low, the inverter circuit 2 is connected to the inverter bridge 2 via the abnormality detecting circuit 19 And the interconnection circuit breaker (contactor 6) between the AC power system 8 and the AC power system 8 are opened.

  That is, the voltage relay 17, the frequency relay 18, the frequency change rate relay 27, and the abnormality detection circuit 19 are configured to generate a voltage, a frequency f, or a frequency change rate df from the AC power voltage output from the AC power system 8 and the inverter bridge 2. It is an abnormality detection part comprised so that abnormality of / dt might be detected.

  As a result, the isolated operation detection device and the isolated operation detection method for an inverter according to the present embodiment can speed up the isolated operation detection protection of the inverter. Since the inverter bridge 2 can be stopped by the drive gate, it can be stopped in about 10 μs as soon as an abnormality is detected.

  Next, an independent operation detection device and an independent operation detection method for an inverter according to a second embodiment of the present invention will be described below with reference to the drawings. Note that, in the following description, the same components as those in the isolated operation detection device and the isolated operation detection method according to the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  In the isolated operation detection device according to the present embodiment, a loop that controls active power and reactive power of AC power output from the inverter bridge 2 is configured, and when the inverter bridge 2 is disconnected from the AC power system 8, the inverter bridge Based on the frequency of the output voltage of 2, the inverter bridge is driven so that the reactive power changes.

  In addition, the characteristic curve of reactive power with respect to the frequency is moved so that the reactive power becomes almost zero following the normal frequency change (steady state) sufficiently, and the frequency is positively fed back to the fast frequency change (abnormal state). The inverter bridge 2 is controlled in a direction that promotes the change.

  As shown in FIG. 3, in the isolated operation detection device according to the present embodiment, the inverter bridge 2 is a three-phase bridge. Reactors 3a, 3b, and 3c are connected to the AC side of inverter bridge 2, and reactors 3a, 3b, and 3c are delta-connected to filter capacitors 4a, 4b, and 4c. The current detectors 5 a and 5 b are connected to the two phases of the inverter bridge 2 and detect the output current of the inverter bridge 2.

The PQ detection circuit 35 calculates active power P and reactive power Q from the output current of the inverter bridge 2 and the voltage of the load 9. The amplifier 11 detects the voltage of the DC power source 1 and outputs an active power reference P * which is compared and amplified with the voltage reference V * to the amplifier 13a. The active power reference P * and active power P output from the amplifier 11 are amplified by the amplifier 13a, and the signal _V13a is input to the three-phase converter 34.

The output of the function circuit 31 is input to the reactive power reference circuit 33, and an error between the reactive power reference Q * output from the reactive power reference circuit 33 and the reactive power Q of the inverter bridge 2 detected by the PQ detection circuit 35 is amplified by an amplifier 13b. Is amplified and output as a signal _V13b . The signal V _13b is input to the PWM circuit 14 via the three-phase converter 34, the output current of the inverter bridge 2 is controlled by the PWM circuit 14 via the drive circuit 15, and the active power P output from the inverter bridge 2 and Reactive power Q is controlled.

  In this embodiment, the amplifier 11, the amplifier 13 a, the amplifier 13 b, the PWM circuit 14, the reactive power reference circuit 33, the three-phase conversion circuit 34, the PQ detection circuit 35, and the drive circuit 15 use the output from the function unit 100. The drive unit controls the active power P and the reactive power Q of the output power of the inverter bridge 2 and stops the inverter bridge 2 when an abnormality is notified from the abnormality detection unit.

  As described above, when the inverter bridge 2 has a single phase as shown in FIG. 1, the reactive power Q is changed by changing the current phase to detect the single operation of the inverter bridge 2 at a high speed. When the inverter bridge 2 has a three-phase structure as shown in FIG. 6, the reactive power Q output from the inverter bridge 2 is directly controlled to detect the single operation of the inverter bridge 2 at high speed.

  As shown in FIG. 3, the isolated operation detection device for an inverter according to this embodiment has the same configuration as that of the isolated operation detection device according to the first embodiment shown in FIG. That is, according to the isolated operation detection device and the isolated operation detection method of the inverter according to this embodiment, the frequency deviation Δf (f−), which is the difference between the frequency f and the moving average fm, as in the case of the first embodiment described above. At fm = Δf), since f−fm≈0 in a steady state, there is no need to consider the power factor with respect to the frequency deviation Δf. Therefore, the slope of the characteristic function of the reactive power Q with respect to the frequency deviation Δf is suddenly increased (largely). ) To increase the gain of the positive feedback action and shift the frequency f at high speed.

  Then, an abnormality is detected by the voltage relay 17 from the output of the voltage detector 10, a frequency abnormality is detected by the frequency relay 18, an excessive frequency change rate (df / dt) is detected by the frequency change rate relay 27, and an abnormality is detected. Inverter drive is stopped by the drive circuit 15 via the circuit 19 (the gate of the drive element is cut off), and the interconnection breaker (contactor 6) is opened to completely disconnect the inverter bridge 2 from the grid interconnection. . As a result, the isolated operation detection device and the isolated operation detection method for an inverter according to the present embodiment can speed up the isolated operation detection protection of the inverter.

  Next, an independent operation detection device and an independent operation detection method for an inverter according to a third embodiment of the present invention will be described with reference to the drawings. In addition, about the structure similar to the independent operation apparatus and independent operation detection method of the inverter which concerns on the above-mentioned 1st Embodiment and 2nd Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The isolated operation detection device according to the present embodiment has a sum (Δf + k) of the frequency deviation Δf and the value obtained by multiplying the frequency change rate df / dt by a coefficient according to the characteristic function of the reactive power of the inverter bridge 2 or the current phase angle of the inverter bridge 2. The reactive power or the current phase angle is controlled in accordance with the magnitude and polarity of (xdf / dt). In the case shown in FIG. 5, the coefficient k is 1. The value of the coefficient k can be appropriately changed according to the characteristics of the inverter bridge 2.

  As shown in FIG. 5, in this embodiment, the function unit 100 further includes a frequency change rate circuit 50 that calculates a frequency change rate df / dt from the frequency f output from the frequency detection circuit 28, and a phase shift frequency deviation. An addition circuit 51 that adds the frequency deviation Δf output from the circuit 30 and the frequency change rate df / dt is further provided. The sum of the frequency deviation Δf and the frequency change rate df / dt output from the adder circuit 51 is supplied to the function circuit 31.

  The function circuit 31 calculates a function of the reactive power Q (or current phase angle θ) with respect to the sum of the frequency deviation Δf and the frequency change rate df / dt. The frequency change rate df / dt is added to the frequency deviation Δf by the adder circuit 51 and the calculated reactive power value or current phase angle value is input to the phase shift circuit 23 or the reactive power reference circuit 33 via the function circuit 31. Thus, the differential element of the frequency f can be added to the reactive power control, so that the isolated operation can be detected earlier.

  As described above, according to the isolated operation detection apparatus and the isolated operation detection method for inverters according to the first and second embodiments, the frequency deviation Δf is obtained from the frequency deviation Δf obtained by f−fm = Δf. When positive, the advance reactive power is controlled in the advance direction. Control is performed so that the delayed reactive power increases when the frequency deviation Δf is negative.

  Further, according to the isolated operation detection device and the isolated operation detection method of the inverter according to the third embodiment, the frequency deviation rate df / dt is added to the frequency deviation Δf signal, and the frequency deviation Δf and the frequency change rate df are added. The reactive power Q (or current phase angle θ) is controlled by the sum (Δf + k × df / dt) of the coefficient times / dt. Thus, it is possible to provide an isolated operation detection device and an isolated operation detection method for an inverter that can detect an isolated operation at a high power factor in a steady state and at a high speed.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. For example, in the first embodiment and the second embodiment, the characteristics of the frequency deviation Δf and the current phase angle θ of the output current (or the frequency deviation Δf and the reactive power Q) are as shown in FIGS. 2B and 2C. Various modifications can be made. In FIG. 2B and FIG. 2C, the slope of the characteristic function of the reactive power Q (or current phase angle θ) differs depending on whether the absolute value of the frequency deviation Δf is less than or equal to a predetermined value. Yes.

  In FIG. 2B, when the absolute value of the frequency deviation Δf is equal to or less than a predetermined value, the slope of the characteristic function of the reactive power Q (or current phase angle θ) is larger than when the absolute value of the frequency deviation Δf is greater than the predetermined value. In FIG. 2C, when the absolute value of the frequency deviation Δf is equal to or smaller than a predetermined value, the slope of the characteristic function of the reactive power Q (or current phase angle θ) is smaller than when the absolute value is larger than the predetermined value. Further, the characteristic function of the reactive power Q (or the current phase angle θ) may be a linear function or a curvilinear function. Thus, by changing the slope of the characteristic function of the reactive power Q (or current phase angle θ) according to the magnitude of the frequency deviation Δf, it is devised so that the single operation of the inverter can be detected most quickly and reliably. be able to.

  In the above embodiment, the characteristic function of the reactive power Q or the current phase angle θ with respect to the frequency deviation Δf (f−fm = Δf) is used. For example, as shown in FIG. The characteristic function of (or frequency f and reactive power Q) is changed to a characteristic curve of moving average fm, and the current phase angle θ (or reactive power Q) is changed with respect to the short-time frequency f. The effect similar to the isolated operation detection apparatus and isolated operation detection method which concerns on 3rd Embodiment can be acquired.

  In addition, the frequency f and the frequency change rate df / dt are measured every cycle of the AC power supplied from the AC power system 8, but are measured every half cycle in order to achieve higher speed. It can also be devised.

  In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  fm: frequency moving average, Δf: frequency deviation, Q: reactive power, θ: current phase angle (power factor angle), P: active power, P: active power reference, Q: reactive power reference, 1: DC power supply, 2 ... Inverter bridge (inverter) 3, 3a, 3b, 3c ... Reactor 4, 4a, 4b, 4c ... Capacitor 5, 5a, 5b ... Current detector, 6 ... Contactor, 7 ... Breaker, 8 ... AC Power system, 9 ... load, 10 ... voltage detector, 11 ... amplifier, 12 ... current reference circuit, 13, 13a, 13b ... amplifier, 14 ... PWM circuit, 15 ... drive unit, 17 ... voltage relay, 18 ... frequency relay , 19: Abnormality detection circuit, 22: PLL circuit, 23: Phase shift circuit, 26: Sine wave circuit, 27 ... Frequency change rate relay, 28 ... Frequency detection circuit, 29 ... Moving average circuit, 30 ... Frequency deviation for phase shift circuit, DESCRIPTION OF SYMBOLS 31 ... Function circuit, 33 ... Reactive power reference circuit, 34 ... Three-phase converter, 35 ... PQ detection circuit, 50 ... Frequency change rate circuit, 51 ... Adder circuit, 100 ... Function part

Claims (7)

An independent operation detection device for an inverter that converts DC power to AC power and operates in conjunction with an AC power system,
A voltage detector for detecting an AC voltage output from the AC power system and the inverter;
An abnormality detector configured to detect an abnormality in frequency or frequency change rate from the voltage of the AC power output from the AC power system and the inverter;
A frequency detector for detecting the frequency of the AC voltage output from the AC power system and the inverter;
Moving average means for calculating a moving average of the frequency from the frequency detected by the frequency detector;
A frequency deviation means for calculating a frequency deviation from the frequency detected by the frequency detector and the moving average;
According to the magnitude and polarity of the frequency deviation, the reactive power with respect to the frequency deviation or the characteristic function of the current phase angle causes the advanced reactive power to flow when the frequency deviation is positive, and the delayed reactive power when the frequency deviation is negative. Function means for calculating and outputting the value of reactive power or current phase angle so that
An isolated operation detection device comprising: a drive unit that controls output power output from the inverter using the output of the function means and stops the inverter when an abnormality is detected from the abnormality detection unit. The inverter includes a three-phase bridge,
The drive unit is configured to control the active power and reactive power of the output power of the inverter using the output from the function unit, and to stop the inverter when an abnormality is notified from the abnormality detection unit. The isolated operation detection device according to claim 1. An independent operation detection device for an inverter that converts DC power to AC power and operates in conjunction with an AC power system,
A voltage detector for detecting an AC voltage output from the AC power system and the inverter;
An abnormality detector configured to detect an abnormality in frequency or frequency change rate from the voltage of the AC power output from the AC power system and the inverter;
A frequency detector for detecting the frequency of the AC voltage output from the AC power system and the inverter;
Moving average means for calculating a moving average of the frequency from the frequency detected by the frequency detector;
A frequency change rate means for calculating a frequency change rate from the frequency detected by the frequency detector;
A frequency deviation means for calculating a frequency deviation from the frequency detected by the frequency detector and the moving average;
When the sum of the frequency deviation and the frequency change rate is positive, the reactive power flows, and when the sum of the frequency deviation and the frequency change rate is negative, the delayed reactive power flows. According to the characteristic function of reactive power or current phase angle with respect to the sum, function means for calculating and outputting the value of reactive power or current phase angle according to the magnitude and polarity of the sum of the frequency deviation and the frequency change rate;
An isolated operation detection device comprising: a drive unit that controls output power of the inverter using an output from the function unit and stops the inverter when an abnormality is notified from the abnormality detection unit. A contactor is provided between the inverter and a load to which AC power is supplied from the inverter,
The islanding operation detection device according to any one of claims 1 to 3, wherein the contactor opens when an abnormality is detected by the abnormality detection unit. The moving average means is a means for calculating, as the moving average, an average value in an average time of the frequency detected by the frequency detection unit,
4. The isolated operation detection device according to claim 1, wherein the average time is set to five times or more of a target time for detecting the isolated operation of the inverter. An independent operation detection method for an inverter that converts DC power to AC power and operates in conjunction with an AC power system,
Detect the frequency of the AC voltage output from the AC power system and the inverter,
Calculate the moving average of the frequency from the detected frequency,
Calculate the frequency deviation from the detected frequency and the moving average,
When the frequency deviation is positive, the reactive power flows forward, and when the frequency deviation is negative, the delayed reactive power flows. The reactive power with respect to the frequency deviation has a characteristic function according to the magnitude and polarity of the frequency deviation or Calculate the phase angle value,
Control the output power output from the inverter using the calculated reactive power or phase angle value,
From the voltage of the AC power output from the AC power system and the inverter, it is detected whether the frequency or frequency change rate is abnormal,
An isolated operation detection method for stopping the inverter when an abnormality in frequency or frequency change rate is detected. An independent operation detection method for an inverter that converts DC power to AC power and operates in conjunction with an AC power system,
Detect the frequency of the AC voltage output from the AC power system and the inverter,
Calculate the moving average of the frequency from the detected frequency,
Calculate the frequency change rate from the detected frequency,
Calculate the frequency deviation from the detected frequency and the moving average,
The reactive power flows when the sum of the frequency deviation and the frequency change rate is positive, and the reactive power flows when the sum of the frequency deviation and the frequency change rate is negative. By the reactive power characteristic function with respect to the sum of the rate, the value of the reactive power or phase angle is calculated according to the magnitude and polarity of the sum of the frequency deviation and the frequency change rate,
Control the output power output from the inverter using the calculated reactive power or phase angle value,
From the voltage of the AC power output from the AC power system and the inverter, it is detected whether the frequency or frequency change rate is abnormal,
An isolated operation detection method for stopping the inverter when an abnormality in frequency or frequency change rate is detected.

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