JP2020010567A - System-cooperative inverter device - Google Patents

Abstract

To achieve safe protection for a negative device, and reduce the number of components.SOLUTION: A system-cooperative inverter device 30 comprises: an input capacitor 32; an inverter 33; a filter circuit 34 formed by an inductor and an output capacitor; and a control circuit 40 that controls a switching operation of the inverter 33. The control circuit 40 has an abnormal detection part 50 that detects an abnormal state of an output voltage Vo of the filter circuit 34. The control circuit 40 makes the control of a storage electric charging of the output capacitor to be discharged to the input capacitor 32 via the inverter 33 when detecting a solo operation state separated from a power system 22 on the basis of a detection result of the abnormal detection part 50.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a system interconnection inverter device that is connected to an electric power system so as to be able to be interconnected and converts DC power (DC power) into AC power (AC power).

FIG. 4 is a configuration diagram showing a conventional single-phase system interconnection inverter device 10 described in Patent Documents 1 and 2, and the like.
The single-phase system interconnection inverter device 10 is a device that converts a DC input voltage Vin supplied from a DC power supply 1 into a single-phase AC output voltage Vo. For example, the single-phase system interconnection inverter device 10 is connected to a power system 2 that is a single-phase commercial power system. On the other hand, they are connected via a circuit breaker 3 and the like so as to be interconnected. The load device 4 is branched and connected to the output side of the system interconnection inverter device 10.

  The system interconnection inverter device 10 has a DC / DC converter 11 for converting a DC input voltage Vin into a predetermined DC voltage, and an input capacitor 12 for charge storage is connected in parallel to the output side. A DC / AC inverter 13 is connected to the input capacitor 12. The DC / AC inverter 13 is a circuit that performs an on / off operation of a voltage Vdc of the input capacitor 12 by a switching drive signal supplied from a control circuit (not shown), and outputs an AC inverter voltage Vinv and an inverter current Iinv. Four switch elements (for example, insulated gate bipolar transistors, hereinafter referred to as "IGBTs") 13a1, 13a2, 13b1, and 13b2 are configured by bridge connection. A filter circuit 14 is connected to an output side of the DC / AC inverter 13. The filter circuit 14 is a circuit that removes high-frequency components of the input inverter voltage Vinv and inverter current Iinv and outputs an output voltage Vo and an output current Io, and is configured by an LC circuit including an inductor 14a and an output capacitor 14b. . A switch 15 that is turned on / off by a control circuit (not shown) is connected to the output side of the filter circuit 14.

  In this type of single-phase system interconnection inverter device 10, a DC input voltage Vin supplied from a DC power supply 1 is converted into a predetermined DC voltage by a DC / DC converter 11 and stored in an input capacitor 12. The voltage Vdc stored in the input capacitor 12 is converted into an AC inverter voltage Vinv and an inverter current Iinv by a DC / AC inverter 13, and then a high frequency component is removed by a filter circuit 14. The AC output voltage Vo and the output current Io from which the high-frequency components have been removed are output to the load device 4 and the power system 2 via the switch 15. When a power failure or the like occurs in the power system 2, the circuit breaker 3 is turned off, the grid-connected inverter device 10 is disconnected from the power system 2 to be in an independent operation state, and the output voltage Vo of the grid-connected inverter device 10 and The output current Io is supplied to the load device 4.

FIG. 5 is a configuration diagram showing a conventional three-phase system interconnection inverter device 10A. In FIG. 5, the same elements as those of the conventional single-phase system interconnection inverter device 10 shown in FIG. 4 are denoted by the same reference numerals.
The three-phase system interconnection inverter device 10A in FIG. 5 is a device that is interconnected with a power system 2A that is a three-phase commercial power system. A three-phase circuit breaker 3A and a load device 4A are connected between the power system 2A and the system interconnection inverter device 10A.

  The three-phase system interconnection inverter device 10A includes a DC / DC converter 11 and an input capacitor 12 similar to those in FIG. 4, and a three-phase DC / AC inverter 13A, a filter circuit 14A, and a switch different from those in FIG. 15.

  The DC / AC inverter 13A is a circuit that performs an on / off operation of a voltage Vdc of the input capacitor 12 by a switching drive signal supplied from a control circuit (not shown), and outputs a three-phase AC inverter voltage Vinv and an inverter current Iinv. There are six switch elements (for example, IGBTs) 13a1 to 13a3 and 13b1 to 13b3 connected in a bridge. The filter circuit 14A is a circuit that removes high-frequency components of the input inverter voltage Vinv and inverter current Iinv and outputs three-phase output voltage Vo and output current Io, and includes three inductors 14a1 to 14a3 and three output capacitors. It is composed of LC circuits 14b1 to 14b3. The output side of the filter circuit 14A is connected to a three-phase switch 15A that is turned on / off by a control circuit (not shown).

  In such a three-phase system interconnection inverter device 10A, substantially the same operation as that of the single-phase system interconnection inverter device 10 is performed.

JP 2001-186664 A Japanese Patent No. 6173978 (Japanese Patent Application Laid-Open No. 2016-12971)

Supplementary edition of the Japan Electric Association, “Guidelines for interconnection to grid JEAC9701-2016”, March 2017

  6 (a) and 6 (b) are waveform diagrams illustrating an example of high-frequency voltage output during single operation for explaining the problem of the conventional three-phase system interconnection inverter device 10A of FIG. Further, FIGS. 7A and 7B are waveform diagrams showing an example of high-voltage output at the time of stand-alone operation for explaining the problem of the conventional three-phase system interconnection inverter device 10A of FIG. is there.

FIGS. 6A and 6B show an example of high-frequency voltage output when the three-phase grid-connected inverter device 10A is operated independently under the advanced power factor output condition, and FIG. The waveform of the voltage Vo and the waveform (b) of FIG. 6 are the waveforms of the output current Io, and the horizontal axis represents time. 6 (a) and 6 (b) show the waveforms before the power system power outage, and the right side shows the waveforms after the power system power outage.
For example, when the three-phase grid-connected inverter device 10A enters the isolated operation state due to the power system blackout, the output current Io hardly flows in a substantially no-load state, but a high-frequency voltage is output. For this reason, the load device 4A is adversely affected, and it is necessary to take measures.

FIGS. 7A and 7B show examples of high-voltage output when the three-phase grid-connected inverter device 10A is in an independent operation state due to a power outage under light load conditions. ) Shows the waveform of the output voltage Vo, and FIG. 3B shows the waveform of the output current Io, with the horizontal axis representing time. 7 (a) and 7 (b) show the waveforms before the power system blackout, and the right sides show the waveforms after the power system blackout.
Even after the three-phase system interconnection inverter device 10A stops oscillating and operates in an isolated state, the high-voltage output state continues because the residual charges of the output capacitors 14b1 to 14b3 are not discharged.

The conventional three-phase system interconnection inverter device 10A of FIG. 5 has the following problems.
Under an unbalanced condition between the output power of the DC / AC inverter 13A and the power consumption of the load device 4A, when the power system 2A is out of power, for example, when the power consumption of the load device 4A is small, the grid-connected inverter device The output of the DC / AC inverter 13A may continue until the isolated operation of the 10A is detected. In such a case, as shown in the waveforms of the output voltage Vo and the output current Io on the right side of FIGS. 7A and 7B, the output power of the DC / AC inverter 13A is reduced by the output capacitors 14b1 to 14b1 in the filter circuit 14A. High voltage is generated at the output terminal by accumulating in the output terminal 14b3, which may damage the load device 4A. Further, under the condition of unbalance of reactive power, when the grid-connected inverter device 10A is in the isolated operation state separated from the power grid 2A, as shown in the waveform of the output voltage Vo on the right side of FIG. There is a possibility that high-frequency output voltage Vo is output from system inverter device 10A.

  According to the grid connection rule described in Non-Patent Document 1, the output of the leading power factor is obtained from the DC / AC inverter 13A in the grid connection inverter device 10A. Therefore, when the grid-connected inverter device 10A enters the isolated operation state, the risk of high-frequency voltage output increases as shown in the waveform of the output voltage Vo on the right side of FIG. When a high-frequency voltage is applied to a capacitor in the load device 4A, an excessive high-frequency current may flow through the capacitor and damage the load device 4A.

  In the technique of Patent Document 1, for safe operation, an overvoltage and an overcurrent in the grid-connected inverter device 10A are detected, the grid-connected inverter device 10A is stopped, and the electric charges of the output capacitors 14b1 to 14b3 are discharged by the discharge circuit. Is to be discharged. However, since a dedicated discharge circuit is required, there is a problem that the number of components of the grid-connected inverter device 10A increases and the device cost increases.

  A similar problem exists in the conventional single-phase system interconnection inverter device 10 shown in FIG.

  The system interconnection inverter device of the present invention, an input capacitor to which a DC input voltage is applied, is connected to the power system so as to be interconnected, and converts the DC voltage stored in the input capacitor into an AC voltage by switching. A filter circuit that has an inverter that outputs to the power system side, an inductor and an output capacitor, removes a harmonic component of the AC voltage output from the inverter, and outputs an AC output voltage, and switching of the inverter. And a control circuit for controlling the operation.

  The control circuit has an abnormality detection unit that detects an abnormal state of the output voltage, and based on a detection result of the abnormality detection unit, detects an isolated operation state that is disconnected from the power system. The stored charge is controlled to be discharged to the input capacitor via the inverter.

  According to the system interconnection inverter device of the present invention, for example, an output voltage is instantaneously detected using a three-phase AC vector operation, and an abnormal state of the output voltage is rapidly detected. When the isolated operation state of the interconnection inverter device is detected, the accumulated charge of the output capacitor is discharged to the input capacitor via the inverter. Therefore, safety protection for the load device can be performed. Further, since a dedicated discharge circuit for discharging the accumulated charge of the output capacitor is not required, the number of components can be reduced, and the cost of the device can be reduced.

FIG. 1 is a configuration diagram illustrating a three-phase system interconnection inverter device 30 according to a first embodiment of the present invention. FIG. 1 is a functional block diagram showing a configuration example of an abnormality detection unit 50 in FIG. Functional block diagram illustrating a configuration example of an abnormality detection unit 50A according to a second embodiment of the present invention. Configuration diagram showing a conventional single-phase system interconnection inverter device 10 Configuration diagram showing a conventional three-phase system interconnection inverter device 10A Waveform diagram showing an example of high-frequency voltage output when in isolated operation, for explaining the problem of the conventional three-phase system interconnection inverter device 10A. Waveform diagram showing an example of high-voltage output at the time of islanding operation for explaining the problem of the conventional three-phase system interconnection inverter device 10A.

  Embodiments of the present invention will become apparent from the following description of the preferred embodiments when read in light of the accompanying drawings. However, the drawings are for explanation only, and do not limit the scope of the present invention.

(Configuration of Embodiment 1)
FIG. 1 is a configuration diagram illustrating a three-phase system interconnection inverter device 30 according to the first embodiment of the present invention.
The three-phase system interconnection inverter device 30 is a device that converts a DC input voltage Vin supplied from the DC power supply 21 into a three-phase u, v, w AC output voltage Vo, and is, for example, a three-phase commercial power system. It is connected to a certain electric power system 22 via a three-phase circuit breaker 23 and the like so as to be interconnected. A three-phase load device 24 is branch-connected to the output side of the system interconnection inverter device 30.

  The grid interconnection inverter device 30 has a single-phase DC / DC converter 31 of a boost chopper type or the like that converts a DC input voltage Vin into a predetermined DC voltage under the control of a control unit (not shown). Input capacitors 32 are connected in parallel. A three-phase DC / AC inverter 33 is connected to the input capacitor 32. The three-phase DC / AC inverter 33 performs an on / off operation of the voltage Vdc of the input capacitor 32 by the switching drive signal S45 supplied from the control circuit 40, and outputs the three-phase u, v, w AC inverter voltage Vinv and the inverter. This is a circuit that outputs a current Iinv. The three-phase DC / AC inverter 33 is configured by bridging six switch elements (for example, IGBTs) 33a1 to 33a3, 33b1 to 33b3 that are turned on / off by a switching drive signal S45. A body diode 33c is connected to each of the IGBTs 33a1 to 33a3 and 33b1 to 33b3 in antiparallel.

  A three-phase filter circuit 34 is connected to the output side of the DC / AC inverter 33. The three-phase filter circuit 34 is a circuit that removes high-frequency components of the three-phase inverter voltage Vinv and the inverter current Iinv and outputs an output voltage Vo and an output current Io having a three-phase output frequency fo. The three-phase filter circuit 34 is composed of an LC circuit including three inductors 34a1 to 34a3 and three output capacitors 34b1 to 34b3. A three-phase filter such as a relay that is turned on / off by the control circuit 40 is provided on the output side. Switch 35 is connected.

  On the output sides of the inductors 34a1 and 34a3, current transformers (CT) for measuring the inverter current Iinv and outputting the measured current iinv and current measuring instruments 36a and 36b such as shunt resistors are attached. Further, on the output side of the filter circuit 34, an instrumentation transformer (VT) for measuring the output voltage Vo and outputting the measured voltages vo (= vu, vv, vw) of the three phases u, v, w, and a resistor divider are provided. A voltage measuring device 37 such as a circuit is attached. A control circuit 40 is connected to the output sides of the current measuring devices 36a and 36b and the voltage measuring device 37.

  The control circuit 40 generates a switching drive signal S45 for controlling the switching operation of the DC / AC inverter 33 based on the measurement current iinv and the measurement voltage vo, and furthermore, a control signal for turning on / off the switch 35. And the like.

  The control circuit 40 includes a current measurement unit 41 that converts the measurement current iinv into a current measurement value S41 of a digital signal, and a switching unit 42 that switches between an inverter current command CCa and a capacitor discharge current command CCb. A subtraction unit 43 is connected to the output sides of the unit 41 and the switching unit 42. The subtraction unit 43 subtracts the current measurement value S41 from the inverter current command CCa or the capacitor discharge current command CCb switched by the switching unit 42 and outputs a subtraction value S43. Is connected.

  The current control unit 44 performs feedback control such as proportional integral control on the subtraction value S43 and outputs a modulation control signal S44. A pulse width modulation control unit (hereinafter “PWM control unit”) is provided on the output side. .) 45 are connected. The PWM control unit 45 generates a switching drive signal S45 by performing pulse width modulation on the modulation control signal S44 with a carrier wave such as a triangular wave, and controls the IGBTs 33a1 to 33a3, 33b1 to 33b3 in the DC / AC inverter 33 by the switching drive signal S45. An on / off operation is performed.

  An abnormality detection unit 50 is connected to the output side of the voltage measuring device 37. The abnormality detection unit 50 detects an abnormal state of the output voltage Vo (for example, an abnormal state of the overvoltage or the output frequency fo) based on the measured voltage vo, outputs an abnormality detection result S50, and sets the input side of the switching unit 42 to: This is to switch from the inverter current command CCa side to the capacitor discharge current command CCb side. When the current measuring unit 41 including the switching unit 42, the subtracting unit 43, the current controlling unit 44, and the PWM controlling unit 45 detect the isolated operation state disconnected from the power system 22 based on the abnormality detection result S50, the output capacitor It has a function of discharging the accumulated charges of 34b1 to 34b3 to the input capacitor 32 via the DC / AC inverter 33.

  Although not shown, the control circuit 40 also has an isolated operation control unit and the like for detecting the isolated operation state of the grid interconnection inverter device 30 and turning off the switch 35. The control circuit 40 includes a processor having a central processing unit (CPU), an individual circuit, and the like.

FIG. 2 is a functional block diagram illustrating a configuration example of the abnormality detection unit 50 in FIG.
The abnormality detection unit 50 has a function of outputting an abnormality detection result S50 indicating an abnormal state of the output voltage Vo (for example, an abnormal state of overvoltage), and includes a vector voltage detection unit 51. On the output side of the vector voltage detection unit 51, a filter 52, an upper limit value excess detection unit 53, and a predetermined time continuation detection unit 54 are connected in cascade (cascade connection). Further, the upper limit value or lower limit value excess detecting unit 55 for inputting the duty ratio DR of the switching drive signal S45 and the absolute value voi of the measured voltage instantaneous value which is the instantaneous value of the measured voltage vo are input to the abnormality detecting unit 50. An upper limit value excess detection section 57 is provided. The output side of the upper limit value or lower limit value excess detection section 55 is connected to a predetermined time continuation detection section 56. The output side of the upper limit value excess detection section 57 is also connected to the predetermined time continuation detection section 58. An OR section (hereinafter, referred to as an “OR section”) 59 is connected to the output side of the three predetermined time continuation detecting sections 54, 56, 58.

・・・（１） The vector voltage detection unit 51 performs a vector operation on the measured voltage vo of the output voltage Vo measured by the voltage measuring device 37 to instantly calculate the AC voltage amplitude vd, and the three-phase / two-phase voltage conversion unit 51a And an AC voltage amplitude calculator 51b. The three-phase / two-phase voltage converter 51a converts the measured voltages vo (= vu, vv, vw) of the three phases u, v, w into the measured voltages vα of the two phases α, β by the vector operation of the following equation (1). , Vβ, and outputs the result to the AC voltage amplitude calculator 51b.

... (1)

The AC voltage amplitude calculator 51b calculates the AC voltage amplitude vd instantaneously from the measured voltages vα and vβ according to the following equation (2), and outputs the AC voltage amplitude vd to the filter 52.
vd = √ (vα ² + vβ ² ) (2)

  The filter 52 smoothes the AC voltage amplitude vd and outputs the AC voltage amplitude vd to the upper limit value excess detection unit 53. When detecting that the smoothed AC voltage amplitude S52 has exceeded the upper limit threshold value, the upper limit value excess detection section 53 outputs the upper limit value excess detection result S53 to the continuation detection section 54 for a predetermined time. When detecting that the upper limit value excess detection result S53 has continued for a predetermined time or more, the predetermined time continuation detection section 54 outputs the predetermined time continuation detection result S54 to the OR section 59.

  When detecting that the duty ratio DR of the switching drive signal S45 has exceeded a predetermined upper limit or lower limit, the upper limit or lower limit excess detector 55 continuously detects the upper limit or lower limit excess detection result S55 for a predetermined time. This is output to the unit 56. Upon detecting that the upper limit value or lower limit value excess detection result S55 has continued for a predetermined time or more, the predetermined time continuation detection unit 56 outputs the predetermined time continuation detection result S56 to the OR unit 59.

  When detecting that the absolute value (= | measured voltage instantaneous value |) voi of the measured voltage instantaneous value exceeds the predetermined upper limit value, the upper limit value excess detection unit 57 continuously detects the upper limit value excess detection result S57 for a predetermined time. This is output to the unit 58. When detecting that the upper limit value excess detection result S57 has continued for a predetermined time or more, the predetermined time continuation detection unit 58 outputs the predetermined time continuation detection result S58 to the OR unit 59.

  The OR unit 59 calculates the logical sum of the three predetermined time continuation detection results S54, S55, and S56, and when any one of the results is input, converts the abnormality detection result S50 indicating the abnormal state of the output voltage Vo into the abnormality detection result S50 in FIG. This is given to the switching unit 42.

(Normal operation of the first embodiment)
In the case of the normal operation, the system interconnection inverter device 30 in FIG. 1 has the circuit breaker 23 and the switch 35 turned on, and is interconnected with the power system 22. The input side of the switching unit 42 is connected to the inverter current command CCa side, and the target inverter current command CCa input to the switching unit 42 is input to the subtraction unit 43.

  The DC input voltage Vin supplied from the DC power supply 1 is converted into a predetermined DC voltage by the DC / DC converter 31, and the charge of the DC voltage is stored in the input capacitor 32. The DC voltage Vdc stored in the input capacitor 32 is converted into a three-phase inverter voltage Vinv and an inverter current Iinv by the switching operation of the IGBTs 33a1 to 33a3 and 33b1 to 33b3 in the DC / AC inverter 33. From the converted three-phase inverter voltage Vinv and inverter current Iinv, high-frequency components are removed by inductors 34a1 to 34a3 and output capacitors 34b1 to 34b3 in the filter circuit 34, and an output voltage Vo having a three-phase output frequency fo is generated. Is done. The output voltage Vo having the three-phase output frequency fo from which the high-frequency component has been removed is output to the load device 24 via the switch 35.

  The inverter current Iinv is measured by the current measuring devices 36a and 36b, and the measured current iinv output from the current measuring devices 36a and 36b is converted by the current measuring unit 41 into a current measurement value S41 of a digital signal, and the subtraction unit 43 Sent to The subtractor 43 subtracts the measured current value S41 from the input inverter current command CCa, and sends the subtracted value S43 to the current controller 44. The current control unit 44 generates a modulation control signal S44 by performing a feedback control such as a proportional-integral control in order to reduce the input subtraction value S43, and supplies the modulation control signal S44 to the PWM control unit 45. The PWM control unit 45 generates a switching drive signal S45 by performing pulse width modulation on the modulation control signal S44 with a carrier wave such as a triangular wave, and controls the IGBTs 33a1 to 33a3, 33b1 to 33b3 in the DC / AC inverter 33 by the switching drive signal S45. On / off operation. Thus, the inverter current Iinv flowing through the inductors 34a1 to 34a3 is maintained at a current value that matches the inverter current command CCa.

For example, when the DC input voltage Vin of the DC power supply 21 fluctuates and the output power of the grid-connected inverter device 30 becomes larger than the supply power of the power system 22, the output power of the grid-connected inverter device 30 is transmitted to the load device 24. The power is supplied to the power system 22 (reverse power flow). On the other hand, when the output power of the grid interconnection inverter device 30 becomes smaller than the power supplied to the power system 22, the power supplied from the power system 22 is supplied to the load device 24. When the power consumption of the load device 24 increases, the output power of the grid-connected inverter device 30 and the supply power of the power system 22 are supplied to the load device 24.
When the power circuit 22 turns off the circuit breaker 23 due to a power failure or the like, the power supply from the power system 22 to the load device 24 is stopped, and the grid interconnection inverter device 30 shifts to the isolated operation state.

(Operation of the first embodiment at the time of isolated operation)
For example, in FIG. 1, when the circuit breaker 23 is turned off due to a power outage of the power system 22 and the system interconnection inverter device 30 shifts to the isolated operation state, when the output voltage Vo is in an overvoltage abnormal state, The output voltage Vo is measured by the voltage measurement device 37, and the measurement voltage vo output from the voltage measurement device 37 is input to the vector voltage detection unit 51 in the abnormality detection unit 50 in FIG.

  In the vector voltage detection unit 51, the three-phase / two-phase voltage conversion unit 51a performs the vector operation of the expression (1) on the input measurement voltage vo, and the measurement voltage vo (= vu) of the three-phase u, v, w , Vv, vw) are converted into two-phase α, β measurement voltages vα, vβ and output to the AC voltage amplitude calculation unit 51b. The AC voltage amplitude calculator 51b calculates the AC voltage amplitude vd instantaneously by performing the calculation of the equation (2) based on the converted two-phase α, β measurement voltages vα, vβ.

  From the calculated AC voltage amplitude vd, a smoothed AC voltage amplitude S52 is generated by digital processing of the filter 52 or the like, and is output to the upper limit value excess detection unit 53. The upper limit value excess detection unit 53 monitors whether or not the input AC voltage amplitude S52 has exceeded the upper limit value threshold, and when detecting that the input AC voltage amplitude S52 has exceeded the upper limit threshold value, determines the upper limit value excess detection result S53. Output to the time continuation detection unit 54. The predetermined time continuation detecting section 54 monitors whether the upper limit value excess detection result S53 has continued for a predetermined time or more, and outputs the predetermined time continuation detection result S54 to the OR section 59 when detecting that the upper limit value excess detection result S53 has continued for a predetermined time or more. I do. When receiving the detection result S54 for the continuation of the predetermined time, the OR unit 59 outputs an abnormality detection result S50 indicating that the output voltage Vo is in an overvoltage abnormal state. At this time, the isolated operation detection unit (not shown) in the control circuit 40 in FIG. 1 detects the isolated operation state of the grid-connected inverter device 30, and then the switch 35 is turned off.

  On the basis of the abnormality detection result S50 output from the OR unit 59, the input side of the switching unit 42 in FIG. 1 switches to the capacitor discharge current command CCb side, and the capacitor discharge current command CCb is input to the switching unit 42 and sent to the subtraction unit 43. Can be The subtractor 43 subtracts the measured current value S41 from the capacitor discharge current command CCb, and sends the subtracted value S43 to the current controller 44.

  The current control unit 44 performs a feedback control such as a proportional integral control on the subtraction value S43, generates a modulation control signal S44, and outputs the modulation control signal S44 to the PWM control unit 45. The PWM control unit 45 generates a switching drive signal S45 by pulse width modulating the modulation control signal S44 with a carrier wave such as a triangular wave. By this switching drive signal S45, the IGBTs 33a1 to 33a3, 33b1 to 33b3 in the DC / AC inverter 33 enter the regenerative operation mode.

  Then, the accumulated charges of the output capacitors 34b1 to 34b3 are boosted to the voltage Vdc by the switching operation of the IGBTs 33a1 to 33a3 and 33b1 to 33b3 through the inductors 34a1 to 34a3, and are discharged to the input capacitor 32. As a result, generation of a high voltage at the output terminal of the grid interconnection inverter device 30 is suppressed.

  Further, the abnormality detection unit 50 in FIG. 2 monitors the overvoltage state based on the duty ratio DR of the switching drive signal S45 and the absolute value of the measured voltage instantaneous value (= | measured voltage instantaneous value |) voi.

  For example, the upper limit value or lower limit value excess detection unit 55 in the abnormality detection unit 50 determines that the duty ratio DR of the switching drive signal S45 for controlling the switching operation of the DC / AC inverter 33 exceeds a predetermined upper limit value or lower limit value. It monitors whether or not it has exceeded a predetermined upper limit value or lower limit value, and outputs an upper limit value or lower limit value excess detection result S55 to the continuation detection unit 56 for a predetermined time. The predetermined time continuation detecting section 56 monitors whether or not the upper limit value or lower limit value excess detection result S55 has continued for a predetermined time or more. Output to When receiving the detection result S56 for the continuation of the predetermined time, the OR unit 59 gives the detection result S50 to the switching unit 42 in FIG.

  As a result, the input side of the switching unit 42 is switched to the capacitor discharge current command CCb side, and the IGBTs 33a1 to 33a3 and 33b1 to 33b3 are operated by the operations of the subtraction unit 43, the current control unit 44, and the PWM control unit 45, as described above. Mode. Then, the charges accumulated in the output capacitors 34b1 to 34b3 are boosted to the voltage Vdc by the switching operations of the IGBTs 33a1 to 33a3 and 33b1 to 33b3 through the inductors 34a1 to 34a3, and are discharged to the input capacitor 32. As a result, generation of a high voltage at the output terminal of the grid interconnection inverter device 30 is suppressed.

  2 detects whether the absolute value voi of the instantaneous value of the measured voltage vo measured by the voltage measuring device 37 has exceeded a predetermined upper limit value. When it is detected that the predetermined upper limit value has been exceeded, the upper limit value excess detection result S57 is output to the predetermined time continuation detection unit 58. The predetermined time continuation detecting section 58 monitors whether the upper limit value excess detection result S57 has continued for a predetermined time or more, and outputs the predetermined time continuation detection result S58 to the OR section 59 when detecting that the upper limit value excess detection result S57 has continued for a predetermined time or more. . When the OR unit 59 receives the detection result S58 for a predetermined period of time, the OR unit 59 gives the abnormality detection result S50 to the switching unit 42 in FIG.

  As a result, similarly to the above, the input side of the switching unit 42 is switched to the capacitor discharge current command CCb side, and the electric charges accumulated in the output capacitors 34b1 to 34b3 are passed through the inductors 34a1 to 34a3 to the IGBTs 33a1 to 33a3 and 33b1 to 33b3. By the switching operation, the voltage is raised to the voltage Vdc and discharged to the input capacitor 32. As a result, generation of a high voltage at the output terminal of the grid interconnection inverter device 30 is suppressed.

(Effect of Embodiment 1)
According to the grid interconnection inverter device 30 of the first embodiment, the following effects (a) and (b) are obtained.

(A) As described in the above problem, in the conventional system interconnection inverter device 10A of FIG. 5, under the unbalance condition between the output power of the DC / AC inverter 13A and the power consumption of the load device 4A, the power system 2A During a power outage, for example, when the power consumption of the load device 4A is small, the DC / AC inverter 13A may continue to output until the isolated operation of the grid interconnection inverter device 10A is detected. In such a case, as shown in the waveform of the output voltage Vo on the right side of FIG. 7A, the output power of the DC / AC inverter 13A is accumulated in the output capacitors 14b1 to 14b3 in the filter circuit 14A and becomes high at the output terminal. Voltage may be generated, and the load device 4A may be damaged.
On the other hand, in the system interconnection inverter device 30 according to the first embodiment, the abnormality detection unit 50 detects an abnormal state of the overvoltage in the output voltage Vo at a high speed (for example, several ms). When the isolated operation state of the system interconnection inverter device 30 is detected, the accumulated charges in the output capacitors 34b1 to 34b3 are discharged from the DC / AC inverter 33 in the regenerative operation mode to the input capacitor 32 through the inductors 34a1 to 34a3. I have to. As a result, generation of high voltage in the grid-connected inverter device 30 can be suppressed, and the load device 24 can be safely protected.

  (B) Since a dedicated discharge circuit for discharging the accumulated charges in the output capacitors 34b1 to 34b3 is not required unlike the related art, the number of components can be reduced, and the cost of the apparatus can be reduced.

(Configuration of Second Embodiment)
FIG. 3 is a functional block diagram illustrating a configuration example of the abnormality detection unit 50A according to the second embodiment of the present invention. Elements common to the abnormality detection unit 50 illustrated in FIG. 2 of the first embodiment are denoted by the same reference numerals. ing.

  The abnormality detection unit 50A of the second embodiment includes the vector voltage detection unit 51, the filter 52, the upper limit excess detection unit 53, the predetermined time continuation detection unit 54, the upper limit or lower limit excess detection unit of the first embodiment (not shown). 55, a predetermined time continuation detection unit 56, an upper limit excess detection unit 57, a predetermined time continuation detection unit 58, and the OR unit 59 of the first embodiment, the following configuration is added.

  The abnormality detection unit 50A according to the second embodiment includes an instantaneous phase detection unit 61 connected to the output side of the voltage measuring device 37. The output side of the instantaneous phase detection unit 61 includes a delay unit 62 and a subtraction unit 63. It is connected. Further, on the output side of the subtraction unit 63, an instantaneous frequency calculation processing unit 64, a low-pass filter 65, and a predetermined time continuation detection unit 66 are connected in cascade. An OR unit 59 is connected to the output side of the predetermined time continuation detection unit 66.

The instantaneous phase detector 61 calculates the AC voltage phase angle θ (n) by performing a vector operation of the measured voltages vo of the three phases u, v, and w. The three-phase / two-phase voltage converter 61a and the AC It comprises a voltage phase angle calculator 61b. The three-phase / two-phase voltage converter 61a performs the vector operation of the equation (1), and converts the measured voltages vo (= vu, vv, vw) of the three phases u, v, w into the measured voltages vα of the two phases α, β. , Vβ, and an AC voltage phase angle calculator 61b is connected to the output side. The AC voltage phase angle calculation unit 61b calculates the AC voltage phase angle θ (n) from the converted measurement voltages vα and vβ by the following equation (3). The subtraction unit 63 is connected.
θ (n) = tan ⁻¹ (vα / vβ) (3)

The delay unit 62 delays the AC voltage phase angle θ (n) by one sampling period (z ⁻¹ , where z is a z conversion operator), and subtracts the delayed AC voltage phase angle θ (n−1). This is output to the unit 63. The subtraction unit 63 subtracts the delayed AC voltage phase angle θ (n−1) from the AC voltage phase angle θ (n) to obtain a phase angle change Δθ (n). The instantaneous frequency calculation processing unit 64 is connected. The instantaneous frequency calculation processing unit 64 calculates the instantaneous frequency fi based on the phase angle variation Δθ (n) of the sampling period (1 / fs) according to the following equation (4). 65 are connected.
fi = Δθ (n) × (fs / 2π) (4)
Where fs: sampling frequency

The low-pass filter 65 removes high-frequency components of the instantaneous frequency fi. For example, when performing digital processing, if an input signal is x (n) and an output signal is y (n), the following equation (5) is obtained. , Its output signal y (n) can be calculated.
y (n) = (1−k) × y (n−1) + k × x (n) (5)
Note that k is a filter constant. The configuration of the low-pass filter 65 is not limited to the arithmetic expression of Expression (5), and various configurations can be adopted. The output side of the low-pass filter 65 is connected to a continuation detection unit 66 for a predetermined time.

  The predetermined time continuation detection unit 66 monitors whether or not the instantaneous frequency file from which the high-frequency component has been removed exceeds a predetermined upper and lower limit value and this upper and lower limit excess state continues for a predetermined time or more, and has continued for a predetermined time or more. When this is detected, a detection result S66 indicating an abnormal state of the output voltage Vo (for example, an abnormal state of the output frequency fo) is output to the OR unit 59. The OR unit 59 outputs an abnormality detection result S50 corresponding to the detection result S66 indicating the abnormal state of the output frequency fo, and is provided to the switching unit 42 in FIG.

(Operation of Embodiment 2)
When the output voltage Vo of the three phases u, v, w in FIG. 1 is measured by the voltage measuring device 37 in the abnormality detection unit 50A of FIG. 3, the measurement voltage vo (= vu, v) of the three phases u, v, w vv, vw) are input to the three-phase / two-phase converter 61a in the instantaneous phase detector 61. The three-phase / two-phase conversion unit 61a performs a vector operation of the measurement voltage vo (= vu, vv, vw) of the three-phase u, v, w according to Expression (1), and measures the three-phase u, v, w. The voltage vo is converted into two-phase measured voltages vα and vβ, and the measured voltages vα and vβ are output to the AC voltage phase angle calculator 61b. The AC voltage phase angle calculation unit 61b calculates the AC voltage phase angle θ (n) from the converted measurement voltages vα and vβ by Expression (3), and converts the AC voltage phase angle θ (n) to the delay unit 62. And output to the subtraction unit 63.

The delay unit 62 delays the AC voltage phase angle θ (n) by one sampling period (z ⁻¹ ), and outputs the delayed AC voltage phase angle θ (n−1) to the subtraction unit 63. The subtractor 63 subtracts the delayed AC voltage phase angle θ (n−1) from the AC voltage phase angle θ (n) to obtain a phase angle change Δθ (n), and the phase angle change Δθ (n). ) Is output to the instantaneous frequency calculation processing section 64. The instantaneous frequency calculation processing unit 64 calculates the instantaneous frequency fi from the phase angle change amount Δθ (n) according to equation (4), and outputs the instantaneous frequency fi to the low-pass filter 65.

  The low-pass filter 65 removes the high-frequency component of the instantaneous frequency fi from Expression (5) and the like, and outputs the removed instantaneous frequency fi to the continuous time detection unit 66 for a predetermined time. The predetermined time continuation detection unit 66 monitors whether or not the instantaneous frequency file from which the high-frequency component has been removed exceeds a predetermined upper and lower limit value and this upper and lower limit excess state continues for a predetermined time or more, and has continued for a predetermined time or more. When this is detected, a detection result S66 indicating an abnormal state of the output frequency fo is output to the OR unit 59. Then, an abnormality detection result S50 corresponding to the detection result S66 indicating the abnormal state of the output frequency fo is output from the OR unit 59, and is provided to the switching unit 42 in FIG.

  Then, as in the first embodiment, the input side of the switching unit 42 is switched to the capacitor discharge current command CCb side, and the IGBTs 33a1 to 33a3, 33b1 to 33b3 are regenerated by the operations of the subtraction unit 43, the current control unit 44, and the PWM control unit 45. The operation mode is set. Then, the charges accumulated in the output capacitors 34b1 to 34b3 are boosted to the voltage Vdc by the switching operation of the IGBTs 33a1 to 33a3 and 33b1 to 33b3 through the inductors 34a1 to 34a3, and are discharged to the input capacitor 32. Thereby, generation of a high voltage at the output terminal of the grid interconnection inverter device 30 is suppressed.

(Effect of Embodiment 2)
According to the grid interconnection inverter device 30 of the second embodiment, the following effects (1) to (3) are obtained.

(1) In the conventional grid-connected inverter device 10A, when the grid-connected inverter device 10A is in the isolated operation state separated from the power system 2A under the unbalanced condition of the reactive power, the output on the right side of FIG. As shown in the waveform of the voltage Vo, the DC / AC inverter 13A may output a high-frequency voltage.
On the other hand, in the grid-connected inverter device 30 according to the second embodiment, the abnormal frequency state of the output voltage Vo is detected at a high speed (for example, several milliseconds), and the grid-connected inverter device 30 is stopped. The device 24 can be safely protected. Since the high voltage may be generated simultaneously with the high-frequency output, the inverter current command CCa may be changed to the capacitor discharge current for the regenerative operation before the system interconnection inverter device 30 is stopped in the same manner as in the voltage abnormality detection. By switching to the command CCb, the residual charges of the output capacitors 34b1 to 34b3 are discharged to the input capacitor 32 through the DC / AC inverter 33, whereby the high voltage of the residual charges can be suppressed, and the load device 24 can be safely protected.

(2) In the conventional system interconnection inverter device 10A, the output of the leading power factor is obtained from the DC / AC inverter 13A according to the system interconnection rule described in Non-Patent Document 1. Therefore, when the grid-connected inverter device 10A enters the isolated operation state, the risk of high-frequency voltage output increases as shown in the waveform of the output voltage Vo on the right side of FIG. When a high-frequency voltage is applied to a capacitor in the load device 4A, an excessive high-frequency current may flow through the capacitor and damage the load device 4A.
On the other hand, in the system interconnection inverter device 30 of the second embodiment, under the condition that the output of the leading power factor is required from the DC / AC inverter 33 according to the system interconnection rule, the system interconnection inverter device 30 is used. Even if the unit 30 enters the isolated operation state, it is possible to detect a frequency abnormality at a high speed and stop the operation, so that there is no risk of a high-frequency voltage output. Therefore, for example, the high frequency voltage is not applied to the capacitor in the load device 24 and an excessive high frequency current does not flow, and the load device 24 can be prevented from being damaged.

  (3) Similar to the effect of the first embodiment, since a dedicated discharge circuit for discharging the accumulated charges of the output capacitors 34b1 to 34b3 is not required, the number of components can be reduced, and the cost of the apparatus can be reduced.

(Modification of Examples 1 and 2)
The present invention is not limited to the first and second embodiments, and various usage forms and modifications are possible. For example, there are the following (i) to (iii) as the use forms and modified examples.

(I) The control circuit 40 may be changed to a configuration other than that illustrated. For example, the abnormality detection unit 50A of the second embodiment has an abnormality detection function of the output frequency fo in addition to the abnormality detection function of the output voltage Vo of the abnormality detection unit 50 of the first embodiment. Only the fo abnormality detection function may be provided. Thereby, substantially the same effects as in the second embodiment can be obtained.
(Ii) The power conversion unit in the three-phase system interconnection inverter device 30 in FIG. 1 may be changed to a configuration other than that illustrated. For example, the DC / AC inverter 33 may be configured by other switching elements such as MOS field effect transistors (MOSFETs), SiC transistors, and GaN transistors other than the IGBTs 33a1 to 33a3 and 33b1 to 33b3.
(Iii) FIG. 1 shows a three-phase system interconnection inverter device 30, but the present invention can also be applied to a conventional single-phase system interconnection inverter device 10 as shown in FIG.

Reference Signs List 22 power system 24 load device 30 system interconnection inverter device 32 input capacitor 33 DC / AC inverter 34 filter circuit 34a1 to 34a3 inductor 34b1 to 34b3 output capacitor 40 control circuit 42 switching unit 43, 63 subtraction unit 44 current control unit 45 PWM control Unit 50, 50A abnormality detection unit 51 vector voltage detection unit 52 filter 53, 57 upper limit excess detection unit 54, 56, 58, 66 predetermined time continuation detection unit 55 upper limit or lower limit excess detection unit 59 OR circuit 61 instantaneous phase detection Unit 62 delay unit 64 instantaneous frequency calculation processing unit 65 low-pass filter

Claims (5)

An input capacitor to which a DC input voltage is applied;
An inverter that is connected to the power system so as to be interconnected, converts a DC voltage stored in the input capacitor into an AC voltage, and outputs the AC voltage to the power system side;
A filter circuit that has an inductor and an output capacitor, and that removes a harmonic component of the AC voltage output from the inverter and outputs an AC output voltage;
A control circuit for controlling a switching operation of the inverter;
With
The control circuit includes:
An abnormality detection unit that detects an abnormal state of the output voltage,
Based on the detection result of the abnormality detection unit, when detecting an isolated operation state disconnected from the power system, control to discharge the accumulated charge of the output capacitor to the input capacitor via the inverter,
A system interconnection inverter device having a configuration. The output voltage is a three-phase AC voltage,
The abnormality detection unit,
The three-phase AC voltage vector operation is performed to calculate the AC voltage amplitude instantaneously, and when the AC voltage amplitude is equal to or more than a threshold and continues for a predetermined time or more, the abnormal state of the three-phase AC voltage is detected. The system interconnection inverter device according to claim 1, wherein The abnormality detection unit,
The system interconnection inverter device according to claim 1, wherein the abnormal state of the output voltage is detected when a state in which the instantaneous value of the output voltage exceeds the overvoltage upper limit value continues for a predetermined time or more. The abnormality detection unit,
2. The abnormal state of the output voltage is detected when a state in which a duty ratio of a switching drive signal for controlling the switching operation exceeds a predetermined upper limit value or a lower limit value continues for a predetermined time or more. The grid-connected inverter device as described. The output voltage is a three-phase AC voltage,
The abnormality detection unit,
A vector operation of the three-phase AC voltage is performed to calculate an AC voltage phase angle, an instantaneous frequency is calculated based on a change in the AC voltage phase angle during a sampling period, and the instantaneous frequency exceeds a predetermined upper and lower limit for a predetermined time. 2. The system interconnection inverter device according to claim 1, wherein the abnormal state of the three-phase AC voltage is detected when the continuation is continued.

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