JP2014007909A - Power conversion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion apparatus which can safely stop a circuit element without breakage even when an error such as over-current and over-voltage occurs in a state where internal temperature of a housing is high.SOLUTION: A control circuit 13 which controls a converter 14 and an inverter 10 has heat generation suppressing protection means 20 which adjusts current flowing in a switching element 6 of the converter 14 and suppresses heat generation of a circuit element constituting the converter 14 when determining error occurrence on the basis of detection of over-current by a current detector 15 which detects supply current from a direct-current power supply 1 or detection of over-voltage by a voltage detector 16 which detects output voltage of the converter 14. The control circuit 13 also blocks power supply from the direct-current power supply 1 by operating a DC circuit breaker 2 in accordance with determination of the error occurrence.

Description

  The present invention relates to a power converter that converts DC power obtained from a DC power source, which is a constant current source such as a solar cell, into AC power, and more particularly to protection of an inverter device that links a distributed power source to a system. is there.

  As a conventional step-down power supply device, for example, as shown in FIG. 4, when an abnormality such as a short circuit failure occurs in the switching element 25 of the chopper circuit 29, the voltage of the output side filter capacitor 28 rises. Detection is performed by the circuit 30. When the detection voltage of the voltage detection circuit 30 exceeds a preset value set by the voltage monitoring circuit 31, the overvoltage suppression thyristor 34 is turned on by the ignition circuit 33. When the overvoltage suppression thyristor 34 is turned on, a short-circuit current flows from the high-voltage DC power source 21 via the input side filter reactor 23, the chopper output filter reactor 27, and the overvoltage suppression thyristor 34, and the output of the chopper circuit 29 (the output side filter capacitor 28) Suppresses the overvoltage of both-end voltage. Further, a method is proposed in which the auxiliary trip coil 39 of the high-speed circuit breaker 22 connected in series with the overvoltage suppression thyristor 34 is operated to turn off the high-speed circuit breaker 22 to stop and protect the power supply from the high-voltage DC power supply 21. (For example, see Patent Document 1 below).

  Further, as a conventional overcurrent protection circuit, for example, as shown in FIG. 5, when an overcurrent flows through the load 43 due to a short circuit failure in the load 43, the overcurrent is detected by a resistor 44, and pulse extension is performed. When the switching element 45 is turned on for a long time via the circuit 48, a large current flows from the power supply unit 41 to the overcurrent cutoff type circuit protection element 42 to melt it, and the power supply from the power supply unit 41 to the load 43 is supplied. A method of stopping and protecting has been proposed (see, for example, Patent Document 2 below).

Japanese Patent Laid-Open No. 3-150019 Japanese Patent Application Laid-Open No. 11-191921

  By the way, power converters in recent years are housed in a control panel or a box-shaped housing in order to improve safety, and are installed indoors or outdoors exposed to solar radiation. In addition, each circuit element constituting the power conversion device may be housed in a sealed state or in a completely sealed state to prevent short-circuit failures due to small animals, insects, dust, water droplets, etc. The ambient temperature of each circuit element in the control panel of the apparatus or the box-shaped housing may become a high temperature state.

  In the prior art described in Patent Document 1, when an abnormality is detected, the auxiliary trip coil 39 of the high speed circuit breaker 22 is energized and the high speed circuit breaker 22 is turned off. Is energized, and then there is an operation time (for example, several ms to several hundred ms) until the mechanical contact of the high-speed circuit breaker 22 is reliably turned off. During this operation time, the overvoltage continues to be applied to the output side filter capacitor 28 and the overvoltage suppression thyristor 34 is continuously on. Such a circuit element suddenly generates heat.

  In this case, if the ambient temperature is high as described above (for example, about 90 ° C.), there is a problem that the circuit elements are easily damaged by easily exceeding the allowable rising temperature range (operation guarantee temperature) of each circuit element. It was. In addition, when the output voltage of the chopper circuit 29 (the voltage across the output side filter capacitor 28) is very high (for example, DC48V or more), a high-speed operation incorporating a general trip coil operating voltage (for example, DC12, 24, 48V). Since there was no circuit breaker or a high voltage coil, there was a problem that the size was increased and the cost was increased.

  On the other hand, the conventional overcurrent protection circuit described in Patent Document 2 is a method of fusing the overcurrent interrupting circuit protection element 42 by turning on the switching element 45 for a long time in an abnormal state. There is a time (for example, several ms to several hundred ms) until the overcurrent cutoff circuit protection element 42 is melted. Since the switching element 45 is turned on for a long time until the fusing, the switching element 45 rapidly generates heat.

  In this case, when the ambient temperature is in a high temperature state (for example, about 90 ° C.) as described above, there is a problem that the temperature of the switching element 45 exceeds the operation guarantee temperature and is damaged. Further, when the power supply unit 41 is a constant current source, even if the switching element 45 is turned on for a long time, the overcurrent interruption type circuit protection element 42 does not melt and cannot be protected, or the fusing time until fusing Therefore, even when the ambient temperature is not high, the limited allowable temperature rise range (operation guarantee temperature) of the switching element 45 is easily exceeded and damaged.

  As described above, in any of the prior arts described in Patent Documents 1 and 2, if an abnormality occurs when the ambient temperature of each circuit element is high, the circuit element can be safely stopped without causing damage. There is a problem that it is difficult.

  In addition, in the configuration of Patent Document 1 and Patent Document 2, when ambient temperature is high, in order to be able to stop safely without causing damage to the circuit elements when an abnormality occurs, for example, heat is generated during a protective operation. Although there is a possibility that it can be solved by attaching a heatsink to each circuit element or increasing the size of the heatsink, it is necessary to use a heatsink that is not necessary during normal normal operation, or excessively large heatsinks. Since it is necessary to increase the size, there is a problem of high cost.

  Further, both Patent Document 1 and Patent Document 2 are configured to always cut off the input when erroneous detection of overvoltage and overcurrent occurs. For this reason, for example, the current detector erroneously detects due to noise such as lightning surge, or an overcurrent (short circuit) occurs due to malfunction due to noise in the switching element. Even if an erroneous detection or malfunction occurs, the apparatus always stops and cannot continue to operate. Therefore, in such a case, conventionally, there is a problem that it is necessary to manually start again or to restart after exchanging circuit elements, which takes extra time.

  The present invention has been made to solve the above-described problem, and a converter having a voltage conversion switching element is connected to a DC power source via a DC switch, and the DC power after voltage conversion by this converter is connected. Are sequentially connected to each other, and are provided with a current detector for detecting a supply current from the DC power source and a voltage detector for detecting an output voltage of the converter. The following configuration is employed in a power conversion device including a control circuit that controls the operation of the converter and the inverter based on the detection output from the detector.

  That is, when the control circuit determines that an abnormality has occurred based on the detection of an overcurrent by the current detector or the detection of an overvoltage by the voltage detector, the power conversion device of the present invention provides a switching element for the converter. The control circuit includes a heat generation suppression / protection means that adjusts the current flowing through the circuit element to suppress the heat generation of the circuit elements constituting the converter, and the control circuit operates the DC switch in response to the determination of the occurrence of the abnormality. It is characterized by cutting off the power supply from.

  According to the power conversion device of the present invention, when the control circuit determines that an abnormality has occurred based on the detection of the overcurrent by the current detector or the detection of the overvoltage by the voltage detector, the heat generation suppression protection means is the switching element of the converter. The DC switch is operated by the control circuit to supply power from the DC power supply while maintaining the state where the circuit element is not damaged by adjusting the current flowing through the circuit and suppressing the heat generation of the circuit element constituting the converter. Since it is possible to shut off, circuit elements can be prevented from being damaged at low cost even when the temperature inside the casing is high, and the apparatus can be safely stopped when an abnormality occurs.

It is a block diagram of the power converter device in Embodiment 1 of this invention. It is a time chart used for operation | movement description of the power converter device. It is a block diagram of the power converter device in Embodiment 2 of this invention. It is a block diagram of the conventional step-down power supply device. It is a block diagram of the conventional overcurrent protection circuit.

Embodiment 1 FIG.
1 is a configuration diagram of a power conversion device according to Embodiment 1 of the present invention.

  The power conversion device according to the first embodiment is a system in which distributed power sources are linked to a system, and a DC power source of a constant current source having a maximum output voltage of 300 to 1000 V is provided on the input side of the power conversion device. A certain solar cell 1 is connected via a DC switch 2.

  In the DC switch 2, the positive and negative contacts 2a and 2b are turned on (closed) by manual operation to supply power to the power converter. The DC switch 2 incorporates a trip operation coil 3 in order to cut off and protect the power supply from the solar cell 1 when an abnormality occurs in the power converter, and a control circuit 13 to be described later. When the operation signal Sc is applied to the trip operation coil 3, the contacts 2a and 2b of the DC switch 2 are both turned off (opened).

  In the subsequent stage of the DC switch 2, a boost converter 14 that boosts the voltage of the solar cell 1, and a DC voltage (for example, DC 300 to 1000 V) boosted by the boost converter 14 is converted to an AC voltage (for example, AC 100 V, AC 200 V, AC 400 V). An inverter 10 is provided that converts and connects to an AC power source (system) 11.

  Here, the boost converter 14 includes an input capacitor 4, a reactor 5, a switching element 6, a diode 7, and first and second input capacitors 8 and 9 connected in series with each other for voltage smoothing after boosting. I have. Although two capacitors 8 and 9 are provided here, a single capacitor may be used as long as the withstand voltage can be secured. The inverter 10 may be either a three-phase output or a single-phase output.

  In addition, in order to control the power conversion device, the current detector 15 that detects the current supplied from the solar cell 1 and the voltage across the positive and negative voltages of the first and second input capacitors 8 and 9 are output from the boost converter 14. A voltage detector 16 for detecting the voltage is provided, and a control circuit power supply 12 and a control circuit 13 are provided. In this case, the control circuit power supply 12 is connected to both ends of the input capacitor 4 to take in power and generate a power supply (for example, +5 V, ± 15 V, etc.) necessary for the control circuit 13. In addition, the control circuit 13 generates power based on information on the current flowing through the switching element 6 of the boost converter 14, the detected current of the current detector 15, the detected voltage of the voltage detector 16, and the output current and output voltage of the inverter 10. It has a function of controlling the conversion device by a microcomputer or the like.

  In order to improve safety, the power conversion device having such a configuration is housed in a control panel or a box-shaped housing, etc. (not shown), and is installed indoors or outdoors exposed to sunlight. is there. In addition, in order to prevent short-circuit failures due to small animals, insects, dust, water droplets, etc., it is required to house each circuit element constituting the power converter in a sealed state or a completely sealed state. For this reason, the ambient temperature of the control panel of the power conversion device or the circuit elements inside the box-shaped housing may be in a high temperature state. As described above, in a state where the ambient temperature of each circuit element is high, an overcurrent flows due to a short circuit failure of the switching element 6 of the boost converter 14 or the switching element of the inverter 10, or from the AC power source (system) 11. Even when an abnormality such as overvoltage occurs due to power regeneration or malfunction of the control circuit 13, it is necessary to stop the circuit element safely without causing damage.

  Therefore, in the first embodiment of the present invention, in addition to the above configuration, a circuit element protection circuit 17 and a switching circuit 18 are provided between the control circuit 13 and the switching element 6 of the boost converter 14. In this case, when the current detector 15 detects an overcurrent (short circuit) or the voltage detector 16 detects an abnormality such as an overvoltage, the control circuit 13 operates the switching circuit 18 accordingly. The common contact C from which the gate signal is output is switched from the individual contact A side during normal operation to the individual contact B side connected to the circuit element protection circuit 17.

  Further, when the common contact C of the switching circuit 18 is switched to the individual contact B side, the circuit element protection circuit 17 divides, for example, a gate signal output from the control circuit 13 to the switching element 6 during a normal boosting operation. For example, a gate signal having a lower frequency than that in the normal boosting operation is output by turning the circuit.

  The switching circuit 18 and the circuit element protection circuit 17 adjust the current flowing through the switching element 6 of the boost converter 14 to suppress the heat generation of the circuit elements such as the reactor 5 and the switching element 6 constituting the boost converter 14. The heat generation suppressing and protecting means 20 in the scope of claims is configured.

  Next, the protection operation of each circuit element by the power conversion device having the above configuration will be described with reference to the time chart shown in FIG.

  When the detection current Id of the current detector 15 and the detection voltage Vd of the voltage detector 16 are normal, the control circuit 13 connects the common contact C of the switching circuit 18 to the individual contact A side during normal operation. Since the gate signal Sg having the frequency f1 (for example, 10 to 30 kHz) output from the control circuit 13 during the normal boosting operation is applied to the switching element 6, the voltage of the solar cell 1 is changed to a predetermined DC voltage (for example, the boosting converter 14). DC300-1000V).

  In this state, when an overvoltage occurs due to power regeneration from the AC power source (system) 11 or malfunction of the control circuit 13, the detected voltage Vd of the voltage detector 16 becomes larger than the reference value Vsh, resulting in an overvoltage. It is determined by the control circuit 13 (see FIG. 2A). Although not shown in FIG. 2, even when an overcurrent flows due to a short circuit failure of the switching element 6 of the boost converter 14 or the switching element of the inverter 10, the detection current Id of the current detector 15 is equal to the reference value Ish. The control circuit 13 determines that an overcurrent has occurred.

  When such an abnormality such as overcurrent or overvoltage occurs (time t1 in FIG. 2), the control circuit 13 operates the switching circuit 18 in accordance with this and sets the common contact C to the individual contact A side during normal operation. To the individual contact B side connected to the circuit element protection circuit 17 (see FIG. 2B). As a result, the circuit element protection circuit 17 divides the gate signal output from the control circuit 13 to the switching element 6 during the normal boosting operation, and the frequency f1 during the normal boosting operation (for example, 10). The gate signal Sg having a frequency f2 (for example, about 1 to several kHz) lower than (about 30 kHz) is output (see FIG. 2C). At this time, the control circuit 13 outputs an operation signal Sc for opening the contacts 2a and 2b to the trip operation coil 3 of the DC switch 2 (see FIG. 2 (e)).

  In this case, the frequency f2 and on-time (on-duty) of the gate signal Sg output from the circuit element protection circuit 17 are set so that the contact 2a and 2b are reliably operated by operating the trip operation coil 3 of the DC switch 2 from the control circuit 13. And the maximum ambient temperature at the place where the circuit elements such as the reactor 5 and the switching element 6 are arranged in the control panel or the box-shaped housing. These are set in advance so as not to exceed the allowable rise temperature range (operation guarantee temperature) Tmax of the reactor 5 and the switching element 6.

  Thus, even when the internal temperature of the casing of the power conversion device is in a high temperature state (for example, about 90 ° C.) when an abnormality occurs, the switching element 6 has a frequency lower than the frequency f1 of the normal boost converter 14. By operating at f2, the heat generated by the current flowing from the solar cell 1 to the switching element 6 via the reactor 5 constituting the boost converter 14 is adjusted, and the allowable temperature rise range of the reactor 5 and the switching element 6 (operation guarantee) Temperature) Tmax can be suppressed so as not to exceed (see FIG. 2D).

  Thus, the mechanical contact is reliably turned off by operating the trip operation coil 3 of the DC switch 2 from the control circuit 13 while maintaining the state where the circuit element of the power converter is not damaged by the overvoltage or overcurrent. When an operation time (for example, several ms to several hundred ms) elapses, the trip operation coil 3 operates to turn off (open) the contacts 2a and 2b (time t2 in FIG. 2). Stops.

  As described above, the power conversion device according to the first embodiment safely stops without damaging each circuit element even when an abnormality such as overvoltage or overcurrent is detected when the temperature inside the housing is high. Therefore, it is not necessary to provide an extra heat radiator that is not necessary during normal normal operation, or it is not necessary to excessively increase the size of the heat radiator, thereby providing a low-cost power conversion device. it can. Moreover, even if it is a case where a high voltage and constant current source like the solar cell 1 is used as DC power supply, the power converter device which can be stopped safely without damaging a circuit element can be provided.

  In the above description, when an abnormality such as overvoltage or overcurrent is detected, the pulse-like gate signal Sg given to the switching element 6 is converted to a frequency f2 lower than the frequency f1 output during the normal boosting operation. However, if it is certain that the allowable rise temperature range (operation guaranteed temperature) Tmax of the reactor 5 and the switching element 6 will not be exceeded, the gate signal Sg is not pulsed, and the switching element 6 It is also possible to set in advance as a signal that continuously turns on.

Embodiment 2. FIG.
FIG. 3 is a configuration diagram of the power conversion device according to the second embodiment of the present invention, and components corresponding to or corresponding to those of the first embodiment shown in FIG.

In the power conversion device according to the second embodiment, when an abnormality such as an overcurrent or an overvoltage occurs, the control circuit 13 operates the switching circuit 18 in response to the abnormality to cause the common contact C to operate as the individual contact A during normal operation. The point of switching from the side to the individual contact B side connected to the circuit element protection circuit 17 is the same as in the first embodiment. A feature of the second embodiment is that it includes a time measuring circuit 19 that outputs a time-up signal when a predetermined time elapses after being started by the control circuit 13 at the same time when the switching circuit 18 is switched.
Since the other configuration is basically the same as that of the first embodiment shown in FIG. 1, detailed description thereof is omitted here.

  In the second embodiment, overvoltage or overcurrent has occurred, for example, the detection voltage Vd of the voltage detector 16 is greater than the reference value Vsh, or the detection current Id of the current detector 15 is greater than the reference value Ish. If the control circuit 13 determines that the gate signal Sg is applied to the switching element 6 by the circuit element protection circuit 17 by operating the switching circuit 18 as in the case of the first embodiment. Is switched to the low frequency f2 so that the heat generated by the current flowing from the solar cell 1 through the reactor 5 to the switching element 6 does not exceed the allowable rise temperature range (operation guaranteed temperature) Tmax.

  In parallel with this operation, the control circuit 13 starts the time measurement by activating the time measurement circuit 19 simultaneously with the switching operation of the switching circuit 18. Then, when a time-up signal is output from the time measuring circuit 19 after a predetermined time has elapsed, the control circuit 13 continuously detects overvoltage or overcurrent by the voltage detector 16 or the current detector 15. Therefore, it is determined that the power converter inherent abnormality has occurred, and the operation signal Sc is output to the DC switch 2. As a result, the trip operation coil 3 operates to turn off (open) the contacts 2a and 2b, and the operation of the power converter is stopped.

  On the other hand, the control circuit 13 detects an overvoltage or an overcurrent by the voltage detector 16 or the current detector 15 until a time-up signal is output from the time measuring circuit 19 after a predetermined time has elapsed. When the power converter is lost, the current detector 15 erroneously detects due to noise such as a lightning surge, or an overcurrent is generated due to malfunction due to noise in the switching element 6 of the boost converter 14. It is determined that a temporary misdetection or malfunction has occurred, and the contact point 2a, 2b of the trip operation coil 3 is maintained on (closed) without outputting the operation signal Sc to the DC switch 2. At the same time, the switching circuit 18 is operated to switch the common contact C again to the individual contact A side during normal operation.

  Therefore, the gate signal Sg given to the switching element 6 is restored from the low frequency f2 to the high frequency f1 during the boost operation of the normal boost converter 14, so that the boost converter 14 becomes a normal boost operation. As a result, the circuit element is damaged even when a state that is not an original abnormality of the power converter occurs, such as an erroneous detection of the current detector 15 due to noise such as a lightning surge or an overcurrent due to a malfunction of the inverter 10. It is possible to continue the operation safely without doing.

  The present invention is not limited to the configuration of the first and second embodiments described above, and the configurations of the first and second embodiments may be combined as appropriate without departing from the spirit of the present invention. The configuration of the first and second embodiments can be modified or omitted.

  For example, although the case where the solar cell 1 serving as a constant current source is used as the DC power source is described here, the DC power source is not limited to this, and for example, a DC power source such as a battery or an AC / DC converter is used as the DC power source. It is also applicable to Although the case where the boost converter 14 is provided as a power conversion device has been described here, the present invention can also be applied to a configuration provided with a step-down converter. Furthermore, although the current detector 15 is provided on the negative side of the solar cell 1, it may be provided on the positive side.

1 solar cell (DC power supply), 2 DC switch, 3 trip operation coil,
4 input capacitors, 5 reactors, 6 switching elements, 7 diodes,
8, 9 First and second input capacitors, 10 inverters, 11 AC power supply (system),
12 power supply for control circuit, 13 control circuit, 14 boost converter, 15 current detector,
16 voltage detector, 17 circuit element protection circuit, 18 switching circuit, 19 time measurement circuit,
20 Heat generation suppression protection means.

Claims (2)

A converter having a switching element for voltage conversion is connected to the DC power source via a DC switch, and an inverter for converting DC power after voltage conversion into AC power is sequentially connected by this converter, and the DC power source A current detector that detects the supply current from the power supply and a voltage detector that detects the output voltage of the converter, and controls the operation of the converter and the inverter based on the detection output from the current detector and the voltage detector. In the power conversion device including the control circuit to
When the control circuit determines that an abnormality has occurred based on the detection of an overcurrent by the current detector or the detection of an overvoltage by the voltage detector, the current flowing through the switching element of the converter is adjusted to In addition to heat generation suppression protection means for suppressing heat generation of the circuit elements that constitute the circuit element, the control circuit operates the DC switch according to the determination of the occurrence of the abnormality to cut off the power supply from the DC power supply. A power converter. When the control circuit determines that an abnormality has occurred based on the detection of an overcurrent by the current detector or the detection of an overvoltage by the voltage detector, a time measurement circuit that is activated in response to this and measures a certain time The control circuit does not operate the DC switch when the time measurement circuit determines that the occurrence of the abnormality has been canceled before the fixed time has elapsed and the time is up, and 2. The power conversion device according to claim 1, wherein adjustment of a current flowing through the switching element of the converter is canceled.

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