JP5844869B1 - Abnormality detection device and power conditioner for grid interconnection relay - Google Patents

Abstract

To provide an abnormality detection device capable of accurately detecting an abnormality of a grid interconnection relay without increasing the cost of parts when a commercial system is powered off and starts independent operation. An abnormality detection device for a grid interconnection relay that sets an output voltage of a power conditioner when an abnormality is detected and sets a reference voltage for determining an abnormality of the grid interconnection relay And a first determination process for determining an abnormality of the grid connection relay based on the presence or absence of the output current of the power conditioner in a state in which the contact of the grid connection relay is controlled to open, and a grid connection relay In the state where the contact of the system is open controlled, the grid interconnection relay error is based on the magnitude relationship between the difference between the output voltage of the inverter and the commercial grid voltage and the value obtained by multiplying the reference voltage by a predetermined reliability factor. And an abnormality detection processing unit that executes a second determination process for performing the determination. [Selection] Figure 4

Description

  The present invention relates to an abnormality detection device for a grid interconnection relay and a power conditioner.

  A distributed DC power supply equipped with solar cells, fuel cells, etc. is composed of a power conditioner that converts frequency and voltage into AC power so that it can be used in conjunction with commercial systems. Yes.

  The power conditioner includes a DC / DC converter that adjusts a DC voltage generated by a solar cell, a fuel cell, or the like to a predetermined DC voltage value, and a DC / DC that converts DC power output from the DC / DC converter into AC power. An AC inverter and an LC filter that removes high frequency components from the output of the DC / AC inverter are provided.

  Power conditioners connected to solar cells, fuel cells, etc. are connected to the grid, and a ground fault or short circuit accident occurs, or planned power outages cause power transmission from the substation to the distribution lines. In order to prevent the influence on the operation of the division switch and to ensure the safety at the maintenance work of the distribution line, etc. in the stopped state, that is, the isolated operation state, the power conditioner control device is connected to the grid. The relay is opened and the distributed power source is disconnected from the distribution line.

  Then, the power conditioner relay is closed so as to be connected to the independent system separated from the commercial system by the control device of the power conditioner or to the independent independent system without being connected to the commercial system. Na converts from a distributed DC power supply to an AC power supply and supplies AC power to a self-supporting system.

  The inverter controller includes a current control block that controls the DC / AC inverter so that an AC current synchronized with the phase of the commercial system voltage is output from the DC / AC inverter when the system is connected, and is independent when disconnected. A voltage control block is provided to control the DC / AC inverter so that a voltage of a predetermined level legally output to the system is output. The legally prescribed voltage levels are stipulated in Article 26 of the Electricity Business Act and Article 44 of the Enforcement Regulations of the Act, and are intended for low voltage consumers, 101 ± 6V for standard voltage 100V and 200V for standard voltage. Voltage within 202 ± 20V.

  When performing a self-sustaining operation in which power is disconnected from the commercial system and supplied to the independent system, the contact points of the grid interconnection relay are normal without welding to prevent reverse charging and asynchronous charging to the commercial system. It is necessary to detect whether or not, and when the contact of the grid interconnection relay is welded, it is necessary to prevent the transition from the grid interconnection operation to the independent operation.

  Patent Document 1 includes a filter circuit that smoothes AC power from an inverter circuit, inverter circuit control means that controls the operation state of the inverter circuit, control means that controls connection or disconnection of a grid interconnection relay, , Connected between the filter circuit and the grid connection relay, for detecting the current flowing through the filter circuit, and for the grid connection when the inverter circuit is controlled to be stopped by the inverter circuit control means. There is disclosed a grid interconnection device having means for detecting an abnormality of the grid interconnection device based on the control state of the relay and the detection result of the current detection unit.

  The abnormality detection means determines whether or not the contact of the grid connection relay is welded based on whether or not reactive current is flowing from the commercial system to the capacitor of the filter circuit with the inverter circuit stopped. Is configured to do.

  In Patent Document 2, when the commercial system is operating normally, the DC / AC inverter circuit is controlled to be in a stopped state, and the grid connection relay is controlled to be in an open state. About the first grid connection relay and the second grid connection relay, the potential difference between the input side of the first grid connection relay and the output side of the second grid connection relay, By detecting the potential difference between the output side of one grid connection relay and the input side of the second grid connection relay with a photocoupler, etc., before the inverter circuit and the commercial system are linked, A grid interconnection device that detects whether the grid interconnection relay or the second grid interconnection relay is welded and activates an inverter circuit to perform a similar detection operation when a commercial power failure occurs Has been proposed.

JP 2008-35655 A JP 2011-135767 A

  However, the abnormality detection means of the grid interconnection device disclosed in Patent Document 1 is configured to detect the presence or absence of reactive current flowing from the commercial system to the filter circuit by stopping the inverter during grid interconnection or disconnection. In the case where the commercial system has a power failure and starts the self-sustained operation, there is a problem that an abnormality of the grid interconnection relay cannot be detected.

  In the grid interconnection device disclosed in Patent Document 2, the potential difference between the input side of the first grid interconnection relay and the output side of the second grid interconnection relay, and the first grid interconnection relay There is a problem in that separate circuit elements for detecting the potential difference between the output side and the input side of the second grid interconnection relay are required, increasing the component cost.

  Furthermore, because the power failure was detected based only on whether or not the voltage of the commercial system was within the proper range of operation regulations, there was a possibility of erroneous detection due to the effects of noise, and the DC / AC inverter circuit could be When detecting the abnormality of the grid interconnection relay by operating, there is a possibility of erroneous detection only by voltage fluctuation depending on the connection state of the load to the commercial system.

  In view of the above-described problems, the object of the present invention is to provide a grid interconnection that can accurately detect an abnormality in the grid interconnection relay without increasing the component cost when the commercial grid is powered down and starts independent operation. An abnormality detection device for a power relay and a power conditioner are provided.

  In order to achieve the above-mentioned object, the first characteristic configuration of the abnormality detection device for the grid interconnection relay according to the present invention is as described in claim 1 of the claims, via the grid interconnection relay. Incorporated into a power conditioner that can be switched between grid-connected operation linked to the commercial system and autonomous operation that supplies power to the autonomous system via a relay for autonomous system. A grid interconnection relay fault detection device for detecting faults in the grid relay, which sets an output voltage of the power conditioner at the time of fault detection, and a reference voltage for judging the fault of the grid grid relay In the state where the voltage setting process is set and the contact of the grid connection relay is controlled to open, the abnormality determination of the grid connection relay is performed based on the presence or absence of the output current of the power conditioner. A determination process, a difference between the output voltage of the power conditioner and a commercial grid voltage, and a value obtained by multiplying the reference voltage by a predetermined reliability coefficient in a state where the contact of the grid interconnection relay is controlled to be opened. There is an abnormality detection processing unit that executes a second determination process for determining an abnormality of the grid interconnection relay based on the magnitude relationship.

  When the output voltage set in the voltage setting process is output from the power conditioner while the contact of the grid connection relay is controlled to open, the first judgment process is executed and the output current of the power conditioner is checked. Is done. At this time, if a load is connected to the commercial system and the contact is conductive, a current flows through the load. Therefore, whether or not the contact is welded is determined based on the presence or absence of this current.

  In the case where a load is not connected to the commercial system, it is not possible to determine contact welding in the first determination process. Therefore, the second determination process is executed to check the output voltage of the power conditioner. At this time, the output voltage of the power conditioner and the commercial system voltage are detected, and the magnitude relationship between the difference between them and the value obtained by multiplying the reference voltage set in the voltage setting process by a predetermined reliability coefficient is determined. For example, if the contacts are not welded, the commercial system voltage is detected as 0V and the output voltage of the power conditioner is detected as 40V at the time of a power failure, and the reliability coefficient R = 0.5 (R is a positive number of R <1). For example, the magnitude relationship between the voltage difference 40V and the comparison value 20V (= 40 × 0.5) is determined. If the contacts are welded, the commercial system voltage is 40V and the power conditioner The output voltage is detected as 40 V, the magnitude relationship between the difference 0 V between these voltages and the comparison value 20 V (= 40 × 0.5) is determined, and it is determined whether or not the contacts are welded based on the result. The

  And since the circuit elements for detecting the output voltage, output current, and commercial system voltage of the power conditioner are originally circuit elements necessary for the control of the power conditioner, in order to determine the welding of the grid connection relay There is no need to prepare a separate sensor or circuit element.

  As described in claim 2, the second characteristic configuration is the above-described first characteristic configuration, wherein the abnormality detection processing unit performs opening control of all the contacts of the grid interconnection relay. The first determination process and the second determination process are executed, and the first determination process and the second determination process are executed each time the closing control is independently performed for each contact.

  The number of contact points of the grid interconnection relay varies depending on whether the inverter output is single phase or three phase, and the first determination process and the second determination process described above depend on which contact is welded. Results are different. Therefore, after performing the opening control of all the contacts of the grid interconnection relay, the first determination process and the second determination process are executed, and when it is determined that the contacts are welded, it becomes clear that all the contacts are welded, The first determination process and the second determination process are executed each time when the closing control is performed independently for each contact, and when it is determined that the contacts are welded, it becomes clear that the contacts controlled to open are welded. .

  In the third feature configuration, as described in the third aspect, in addition to the first or second feature configuration described above, the abnormality detection processing unit may check whether or not a commercial system voltage exists before the voltage setting process. The voltage setting process is based on the result of the commercial system voltage determination process, and the voltage setting process is a reference for determining the output voltage of the power conditioner and the abnormality of the grid interconnection relay. The voltage is set to a different value.

  When the commercial system voltage is interrupted, the operation shifts to the self-sustained operation. However, the commercial system voltage may temporarily decrease and may be restored soon. In such a case, if the commercial grid connection relay is welded, an inconvenient situation such as an asynchronous input state occurs, and the power conditioner may be damaged. Therefore, commercial voltage determination processing is executed before voltage setting processing, and the output voltage of the power conditioner and the reference voltage for determining abnormality of the grid interconnection relay are set to different values according to the result. As a result, asynchronous charging and reverse charging can be avoided. For example, when a commercial system voltage is detected, a highly accurate contact can be obtained without causing damage to the power conditioner by setting the output voltage of the power conditioner to 0 V and the value of the commercial system voltage to a reference voltage. It becomes possible to perform the welding judgment.

  In the fourth feature configuration, as described in claim 4, in addition to the third feature configuration described above, the commercial system voltage determination processing is performed by the output voltage of the power conditioner set in the voltage setting processing. Based on the magnitude relationship between the value obtained by multiplying the set value by the predetermined reliability coefficient and the commercial system voltage, and the magnitude relationship between the value obtained by multiplying the independent system frequency by the predetermined reliability coefficient and the commercial system frequency. The point is that it is configured to determine the presence or absence of a voltage.

  By checking not only the commercial system voltage but also the commercial system frequency, it is possible to accurately determine the presence or absence of the commercial system voltage without causing erroneous determination due to noise or the like.

  The characteristic configuration of the power conditioner according to the present invention is that, as described in claim 5, the grid connection operation linked to the commercial system via the grid interconnection relay and the independent system via the independent grid relay A single-phase or three-phase power conditioner having a control device capable of switching between self-sustained operation to supply power, the grid interconnection relay having any one of the first to fourth characteristic configurations described above An abnormality detection device is incorporated in the control device.

  When the abnormality detection processing unit determines that the contact point of the grid connection relay is welded, it is possible to avoid the inconvenient situation of reverse charging and asynchronous charging to the commercial system by avoiding independent operation. Can be prevented.

  As described above, according to the present invention, when a commercial system starts a power failure and starts a self-sustained operation, the system connection relay can accurately detect the abnormality of the system connection relay without increasing the component cost. It is possible to provide an abnormality detection device and a power conditioner.

Circuit block diagram of a distributed power supply including a power conditioner Illustration of ON / OFF operation of grid interconnection relay when abnormality is detected Flowchart of commercial system voltage determination processing Flowchart showing abnormality detection method for grid interconnection relay Explanatory drawing of the 1st judgment processing

  Hereinafter, an abnormality detection apparatus and a power conditioner for a grid interconnection relay according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a solar power generation device 1 that is an example of a distributed power source. The solar power generation device 1 includes a solar battery panel SP and a power conditioner PCS to which the solar battery panel SP is connected. The DC power generated by the solar cell panel SP is supplied to the power conditioner PCS via a DC circuit breaker and a surge absorber (not shown).

The power conditioner PCS converts the DC voltage generated by the solar battery panel SP to a predetermined DC link voltage _Vdc and converts the boosted DC link voltage _Vdc into a predetermined AC voltage. A DC / AC inverter 3, an LC filter 4 for removing harmonics from the AC voltage output from the DC / AC inverter 3, a control device 5 for controlling the DC / DC converter 2 and the DC / AC inverter 3, and the like. Yes.

The AC power converted by the power conditioner PCS is configured to be connected to the commercial system 100 via the grid connection relay Ry1 so as to be able to supply power to the AC load R _uw, and is _disconnected from the commercial system 100 due to a power failure or the like. The power supply is connected to the self-supporting load R _sd via the self-supporting system relay Ry2. The contacts of the grid interconnection relay Ry1 are indicated by S _u and S _w , and the two contacts of the independent grid relay Ry2 are indicated by S _sd .

  The control device 5 of the power conditioner PCS includes a microcomputer and a peripheral circuit including an input / output element including a memory element and an AD conversion unit, and a converter control unit 5a that controls a boost switch of the DC / DC converter 2. And an inverter control unit 5b that controls a switch that constitutes a bridge of the DC / AC inverter 3, and an abnormality detection processing unit 5c that detects an abnormality of the grid interconnection relay Ry1. The inverter control unit 5b is configured to control the grid interconnection relay Ry1 or the independent grid relay Ry2 to cause the inverter 4 to perform grid grid operation or autonomous operation.

  The converter control unit 5a monitors the input voltage, input current, and output voltage to the DC / DC converter 2 and performs MPPT control to operate the solar panel SP at the maximum power point, and boosts it to a predetermined output voltage. Configured to control.

  The inverter control unit 5b includes a current control block that controls the output current of the inverter 3 so as to synchronize with the phase of the commercial system voltage during grid connection operation, and a voltage control that supplies AC power of a predetermined voltage to the independent system when disconnected. A block and functional blocks such as an isolated operation detection block for detecting whether or not the system is in an isolated operation state during grid interconnection operation are provided.

  The abnormality detection processing unit 5c detects whether or not the grid connection relay Ry1 is abnormal when shifting to the self-sustaining operation, and if it is detected that a contact welding abnormality has occurred in the grid connection relay Ry1, Is turned on and the independent operation control by the inverter control unit 5b is stopped, and functions as the abnormality detection device of the present invention.

A current transformer CT that detects the output current i _uw of the power conditioner PCS is provided downstream of the inductor L that constitutes the LC filter 4, and a current signal is input to the control device 5 via the interface circuit 6. Further, the voltage dividing circuit for voltage detection that detects the output voltage e _sd of the power conditioner PCS upstream autonomous systems relay Ry2, detects a commercial system voltage e _uw downstream system interconnection relay Ry1 min Each pressure circuit is provided. The output of each voltage dividing circuit is input to the AD conversion unit of the control device 5, and the commercial system frequency f _Grid and the independent system frequency f _sd are obtained from the values.

  When the generated power of the solar panel SP becomes a value that enables interconnection with the commercial system, the inverter control unit 5b closes the grid interconnection relay Ry1 and performs grid interconnection operation, and generates power from the solar panel SP. When the power is reduced or the isolated operation detection block detects that the power is in the isolated operation state, the grid interconnection relay Ry1 is opened and disconnected.

  When the inverter control unit 5b is disconnected due to a single operation state, and the generated power of the solar panel SP is a value sufficient for independent operation, the abnormality detection processing unit 5c is activated to connect to the grid. When the abnormality detection processing unit 5c determines that the grid interconnection relay Ry1 is normal, the relay Ry1 is closed and the autonomous operation is performed by the abnormality detection processing unit 5c. When it is determined that the interconnection relay Ry1 is abnormal, the DC / AC inverter 3 is stopped without closing the independent system relay Ry2.

  Hereinafter, an abnormality detection method for the grid interconnection relay executed by the abnormality detection processing unit 5c will be described. The abnormality detection processing executed by the abnormality detection processing unit 5c includes contact control processing for opening or closing the contact of the grid interconnection relay Ry1, commercial system voltage determination processing, voltage setting processing, and first determination. A process and a second determination process are included.

Abnormality detection processing unit 5c, executes a first determination process and the second determination process described below determines whether the contact is welded after opening controls all contacts S _u, S _w of the grid interconnection relay Ry1 while it is configured to execute a first determination process and the second determination process each time the closing control for each contact S _u or S _w.

When the first determination process and the second determination process are performed after opening control of all the contacts S _u and S _w of the grid interconnection relay Ry1, and as a result, it can be determined that all the contacts S _u and S _w are welded, It becomes clear that is welded. When it can be judged to be normal at this point, to perform a first determination process and the second determination process each time the closing control alone every one contact S _u or S _w. If it can be determined that they are welded to each other, it becomes clear that the contact whose opening is controlled at that time is welded.

FIG. 2 shows a control sequence for the grid interconnection relay Ry1. When the abnormality detection processing unit 5c is activated, all the contacts S _u, while opening control S _w, the contact S _u, performs first and second determination process is a check for S _w, then contact S _u closed for contacts S _u and closing control contact S _w after Configuration control and performs first and second determination process is a check for contact S _w, the further contact S _u the opening control to a predetermined delay time T _dly First and second determination processing, which is a check, is performed.

In this embodiment, each check time and delay time T _dly are 200 msec. Is set to Such an open / close control sequence for the grid interconnection relay Ry1 is the contact control processing step described above.

FIG. 3 shows a welding determination preparation flow of the grid interconnection relay that executes the commercial system voltage determination processing step and the voltage setting processing step described above. In the commercial system voltage determination processing step, when it is necessary to perform independent operation (S1), all the contacts of the grid interconnection relay Ry1 are controlled to open (S2), and the commercial system voltage e _uw is checked (S3). Based on the following [Equation 1], the presence or absence of the commercial system voltage is checked (S4).

Note that E ^* _{sd. rms} is a command value of the effective value of the output voltage during the self-sustaining operation, and x is a reliability coefficient set to a value in the range of 0 <x <1 in order to ensure the accuracy of determination. In this embodiment, x = 0.5 Is set to Further, the independent system frequency f _sd is set to the same value as the commercial system frequency f _Grid .

The commercial system voltage is measured for at least one cycle (20 msec. If the commercial system frequency is 50 Hz), the absolute value | e _uw | of the maximum instantaneous value is obtained, and the absolute value | e _uw | Voltage effective value command value E ^* _sd. The product of _rms and confidence factor x is compared. A plurality of periods may be measured and the average of the maximum values of each period may be obtained.

  Further, the commercial system frequency is compared with the product of the independent system frequency and the reliability coefficient x. The value of the reliability coefficient x is a coefficient for ensuring the reliability of judgment. The closer the value is to 1, the more easily affected by noise, but the more severe it can be judged. It becomes a bad judgment. Usually, an intermediate value of 0.5 is preferably used.

For example, when the commercial system voltage | e _uw | is 0 V, the command value E ^* _{sd. When rms} is 40 V and x = 0.5, [Equation 1] is as follows.
| E _uw | = 0 <0.5 × 40 = 20
f _Grid = 0 <0.5 × 50 = 25

For example, when the commercial system voltage | e _uw | is 141 V, the output voltage command value E ^* _{sd. When rms} is 40 V and x = 0.5, [Equation 1] is as follows.
| E _uw | = 141> 0.5 × 40 = 20
f _Grid = 50> 0.5 × 50 = 25

  That is, in step S4, it is determined that there is a commercial system voltage when both of the two formulas [Equation 1] are established, and it is determined that there is no commercial system voltage when neither is established. Steps S3 and S4 described above are predetermined for the magnitude relationship between the value obtained by multiplying the output voltage setting value of the power conditioner set in the voltage setting processing step by a predetermined reliability coefficient and the commercial grid voltage, and for the independent grid frequency. This is a commercial system voltage determination processing step for determining the presence or absence of the commercial system voltage based on the magnitude relationship between the value multiplied by the reliability coefficient and the commercial system frequency.

  By checking not only the commercial system voltage but also the commercial system frequency, it is possible to accurately determine the presence or absence of the commercial system voltage without causing erroneous determination due to noise or the like.

If it is determined in the commercial system voltage determination processing step that there is a commercial system voltage, the reference value E _{chk for} determining contact welding is determined as the effective value E _{uw. The} delay time T _chk for determining the difference between the inverter output voltage and the commercial grid voltage is set to the reciprocal of the commercial grid frequency (S5). If it is determined that there is no commercial system voltage, the command value of the output voltage of the power conditioner 3 at the time of detecting an abnormality is set (S6), and the reference value E _{chk for} determining the welding of the contact is set in the independent operation. The effective value E _sd.rms of the output voltage is set, and the delay time T _chk at this time is set to the reciprocal of the independent system frequency (S7). That is, when it is determined that there is a commercial system voltage, the power conditioner 3 is stopped and the output voltage becomes 0V. Steps S5 to S7 described above are voltage setting processing steps.

The above-described output voltage command value e ^* _sd is expressed by the following [ _Equation 2].

Here, E ^* _sd.rms is the command value of the effective value of the output voltage, and θ _sd is the phase angle of the output voltage. The value of E ^* _sd.rms = 40V is a command value at the time of abnormality detection processing for the grid interconnection relay, and the command value after normality determination is E ^* _sd.rms = 100V.

  That is, before the voltage setting process step, the commercial system voltage determination process step for determining the presence or absence of the commercial system voltage is executed. Based on the result of the commercial system voltage determination process step, the output voltage of the power conditioner is determined in the voltage setting process step. In addition, the reference voltage for determining the abnormality of the grid interconnection relay is set to a different value.

  When the commercial system voltage is interrupted, the operation shifts to the self-sustained operation. However, the commercial system voltage may temporarily decrease and may be restored soon. In such a case, if the grid connection relay is welded, an inconvenient situation such as reaching an asynchronous input state occurs, and the power conditioner may be damaged.

  Therefore, commercial voltage determination processing is executed before voltage setting processing, and the output voltage of the power conditioner and the reference voltage for determining abnormality of the grid interconnection relay are set to different values according to the result. Therefore, it is possible to accurately determine the abnormality of the grid interconnection relay and to avoid asynchronous charging and reverse charging.

  For example, when a commercial system voltage is detected, a highly accurate contact can be obtained without causing damage to the power conditioner by setting the output voltage of the power conditioner to 0 V and the value of the commercial system voltage to a reference voltage. It becomes possible to perform the welding judgment.

  FIG. 4 shows a welding determination flow of the grid interconnection relay. When the self-sustained operation is started (S11), the above-described contact control processing step is executed (S12), and based on the presence / absence of the output current of the power conditioner with the contact of the grid interconnection relay being controlled to open. The first determination process for determining abnormality of the grid interconnection relay Ry1 (S13, S17), and the output voltage of the power conditioner and the commercial grid voltage in the state where the contact of the grid interconnection relay Ry1 is controlled to open And a second determination process (S14, S15, S16, S17) for determining abnormality of the grid interconnection relay based on the magnitude relationship between the difference between the reference voltage and a value obtained by multiplying the reference voltage by a predetermined reliability coefficient, The contact control process step S12 is repeated until the first determination process and the second determination process are completed for all the contacts (S18).

When the output voltage set in the voltage setting process is output from the power conditioner while the contact of the grid connection relay Ry1 is controlled to open, the first determination process is executed and the output current of the power conditioner is Checked. At this time, if the load R _uw (see FIG. 1) is connected to the commercial system and the contacts S _u and _Sw are conducted, a current flows through the load R _uw , so the contacts are welded based on the presence or absence of this current. It is determined whether or not there is. Note that the state in which the contacts of the grid interconnection relay Ry1 are controlled to open means that all the contacts are controlled to open corresponding to the above-described contact control processing step, and any one contact is controlled to close. It means that the other contact is controlled to be opened.

As shown in FIG. 5, specifically, the output current i _uw of the power conditioner PCS measured at a predetermined sampling period T _s is _{equal to} or more than the threshold value I _uw.chk continuously for at least three times. When the condition that the value increases every time is satisfied (S13, NG), it is determined that the contact of the grid interconnection relay Ry1 is welded, and the error flag storage area set in the memory element is stored. A flag is set (S17). When the error flag is set, an abnormality display is turned on on the display panel of the inverter PCS. In the present embodiment, the threshold I _uw.chk = 15 A, the sampling period T _s = 50 μsec. (Corresponding to the switching cycle of the DC / AC inverter).

In step S13, a state in which the condition that the output current i _uw of the power conditioner PCS is _{equal to} or greater than the threshold value I _uw.chk for at least three consecutive times and the value increases every measurement is not satisfied for a predetermined time (for example, When several cycles continue, it is determined that the current cannot be detected because the load R _uw is not connected, and the second determination process is executed after a predetermined delay time (S14).

In the second determination process, the effective value of the output voltage of the power conditioner PCS and the commercial system voltage is measured during the delay time, and the absolute value | E _{sd. rms-} E _u. A magnitude relationship between _rms | and a value obtained by multiplying the reference voltage E _chk set in the voltage setting processing step by a predetermined reliability coefficient x is determined (S15).

For example, if the contacts are not welded, the commercial system voltage is detected as 0 V and the output voltage of the power conditioner is detected as 40 V when the commercial system is interrupted. Therefore, the reliability coefficient R = 0.5 (R is R <1 (Positive number), the absolute value of the difference | E _{sd. rms-} E _{u. The} comparison value 20V (= 40 × 0.5) is smaller than _rms | = 40V, but if the contacts are welded, the commercial system voltage is detected as 40V, and the output voltage of the power conditioner is detected as 40V. Absolute value | E _{sd. rms-} E _{u. The} comparison value 20V (= 40 × 0.5) increases with respect to _rms | = 0V.

For example, if the contacts are not welded, the commercial system voltage is detected as 100 V and the output voltage of the power conditioner is detected as 0 V. Therefore, the reliability coefficient is R = 0.5 (R is a positive number of R <1). The absolute value of the difference | E _{sd. rms-} E _{u. The} comparison value 50V (= 100 × 0.5) is smaller than _rms | = 100V, but if the contacts are welded, the commercial system voltage is detected as 100V, and the output voltage of the power conditioner is detected as 100V. Absolute value | E _{sd. rms-} E _{u. The} comparison value 50V (= 100 × 0.5) increases with respect to _rms | = 0V.

In step S15, the absolute value of the difference | E _{sd. rms-} E _{u. If} it is determined that the value obtained by multiplying the reference voltage E _chk by the reliability coefficient x is larger than the _rms |, it is determined that the contact of the grid interconnection relay Ry1 is welded, and the value is set in the memory element. A flag is set in the error flag storage area (S17), and the absolute value of the difference | E _{sd. rms-} E _{u. If} it is determined that the value obtained by multiplying the reference voltage E _chk by the reliability coefficient x is smaller than the _rms |, it is determined that the grid interconnection relay Ry1 is normal, and the error flag set in the memory element is stored. The area flag is reset (S16).

The delay time T _chk is set to 3 periods (n = 3) of the commercial system frequency or the independent system frequency, and the effective value is calculated based on the sampling value during at least 3 periods. The delay time T _chk only _needs to be set to a plurality of periods, and is not limited to three periods.

  Since the circuit elements for detecting the output voltage, output current, and commercial system voltage of the power conditioner PCS are originally circuit elements necessary for controlling the power conditioner PCS, in order to determine the welding of the grid interconnection relay Ry2. There is no need to prepare a separate sensor or circuit element.

In the abnormality detection method for the grid interconnection relay according to the present invention, the grid interconnection relay contact is reliably welded regardless of whether or not the AC load R _uw is connected and whether or not the commercial grid voltage is present. Whether or not there is an abnormality can be detected.

In the embodiment described above, the present invention has been described by taking the case where the output of the power conditioner PCS is a single phase as an example. However, the present invention has a three-phase output of the power conditioner PCS, and the grid interconnection relay Ry1. This is also applicable to the case where the contacts are composed of three contacts S _u , S _v , and S _w .

  The above embodiment is merely an example of an abnormality detection method and a power conditioner for a grid interconnection relay according to the present invention, and the technical scope of the present invention is not limited by the description, and the operational effects of the present invention Needless to say, the specific control algorithm can be changed and designed as appropriate as long as the above is achieved.

1: distributed power supply 2: DC / DC converter 3: DC / AC inverter 4: LC filter 5: control device 5a: converter control unit 5b: inverter control unit 5c: abnormality detection processing unit PCS: power conditioner Ry1: system connection System relay Ry2: independent system relays S _u , S _w : contacts

Claims (5)

Built in a power conditioner that can be switched to either grid-connected operation linked to the commercial system via the grid-connected relay or autonomous operation that supplies power to the independent system via the independent-system relay. A grid connection relay abnormality detection device that detects a grid connection relay abnormality when switching to operation,
A voltage setting process for setting an output voltage of the power conditioner at the time of abnormality detection and setting a reference voltage for abnormality determination of the grid interconnection relay;
A first determination process for determining an abnormality of the grid interconnection relay based on the presence or absence of an output current of the power conditioner in a state in which the contact of the grid interconnection relay is controlled to open;
Based on the magnitude relationship between the difference between the output voltage of the power conditioner and the commercial grid voltage and the value obtained by multiplying the reference voltage by a predetermined reliability coefficient in a state where the contact of the grid interconnection relay is controlled to open. Second determination processing for determining abnormality of the grid interconnection relay;
The abnormality detection apparatus of the grid connection relay provided with the abnormality detection process part which performs.   The abnormality detection processing unit performs the first determination process and the second determination process after opening all the contacts of the grid interconnection relay, and performs the first closing control for each contact. The abnormality detection device for a grid interconnection relay according to claim 1, wherein the abnormality detection device is configured to execute a first determination process and a second determination process.   The abnormality detection processing unit executes a commercial system voltage determination process for determining the presence or absence of a commercial system voltage before the voltage setting process, and the voltage setting process is performed based on a result of the commercial system voltage determination process. The abnormality detection device for a grid connection relay according to claim 1 or 2, wherein the output voltage of the conditioner and a reference voltage for determining abnormality of the grid connection relay are set to different values.   In the commercial system voltage determination process, a value obtained by multiplying the output voltage setting value of the power conditioner set in the voltage setting process by a predetermined reliability coefficient, the magnitude relationship between the commercial system voltage, and the independent system frequency are predetermined. The abnormality detection device for a grid interconnection relay according to claim 3, configured to determine the presence or absence of a commercial grid voltage based on a magnitude relationship between a value obtained by multiplying the reliability coefficient by the commercial grid frequency. Single-phase or three-phase equipped with a control device capable of switching between grid-connected operation linked to the commercial system via the grid-connected relay and independent operation supplying power to the independent system via the independent-system relay It is a power conditioner of
A power conditioner in which the abnormality detection device for a grid interconnection relay according to any one of claims 1 to 4 is incorporated in the control device.

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