JP6330580B2 - Grid-connected inverter device - Google Patents

Description

  The present invention relates to a grid-connected inverter device linked to a commercial power system.

  Non-Patent Document 1 below discloses an example of this type of grid-connected inverter device. This grid-connected inverter device is interposed between the distributed power generation source and the commercial power system. In this grid-connected inverter device, the waveform distortion of the current waveform output from the grid-connected inverter device is kept low in order to prevent the power quality of the commercial power system from deteriorating due to the effect of output harmonic distortion due to switching. There is a request to want. In order to meet such a demand, as disclosed in Non-Patent Document 1, an LC filter circuit including a reactor and a capacitor is interposed between the inverter circuit and the commercial power system. The AC power output from the inverter circuit by the on / off control of the switching element can be smoothed by the LC filter circuit including the reactor and the capacitor and supplied to the commercial power system.

Journal of the Institute of Electrical Engineers of Japan. D, 130, 1, 2010, pp. 26-36

(Problems to be solved by the invention)
However, since the control as described above is performed using numerical values depending on the filter constant of the LC filter circuit (reactor inductance, capacitor capacitance, etc.), the filter constant of the LC filter circuit is accurately set when controlling the inverter circuit. Need to figure out. On the other hand, the filter constant varies depending on product variations, and it is difficult to accurately grasp the filter constant in advance. Therefore, when the filter constant cannot be accurately grasped, there is a problem that even if the LC filter circuit is used, the waveform distortion of the current waveform output from the grid interconnection inverter device cannot be kept low. Further, when the LC filter circuit is left in its fault state without being detected as having failed, an output current with a large waveform distortion of the current waveform is continuously supplied to the commercial power system. There is a fear.

  Therefore, the present invention has been made in view of the above points, and one of its purposes is to prevent the power quality of the commercial power system from being deteriorated in the grid-connected inverter device linked to the commercial power system. It is to provide an effective technique for doing this.

(Means for solving the problem)
In order to achieve the above object, a grid-connected inverter device according to the present invention is a device interposed between a distributed power generation source and a commercial power system, and includes an inverter circuit, an LC filter circuit, and a first current detection. A sensor, a second current detection sensor, and a control unit are provided. The inverter circuit converts output power at the time of power generation of the distributed power generation source into AC power and outputs the AC power. The LC filter circuit includes a reactor and a capacitor arranged in parallel with each other, and smoothes the AC power output from the inverter circuit and supplies it to the commercial power system. A first current detection sensor is provided in the output side region of the LC filter circuit, and a second current detection sensor is provided in the input side region of the LC filter circuit. The control unit controls the inverter circuit based on the current phase and the voltage phase in the LC filter circuit at the time of power generation by the distributed power generation source, and information on the current value detected by the first current detection sensor and the second current detection The filter constant of the LC filter circuit is calculated based on both of the information regarding the current value detected by the sensor.

  According to this grid-connected inverter device, the filter constant of the LC filter circuit during the control of the inverter circuit can be calculated with high accuracy, and the calculated filter constant can be reflected in the control of the inverter circuit. In this case, in the control of the inverter circuit, the calculated filter constant may be used as it is, or a filter constant corrected based on the calculated filter constant may be used. As a result, it becomes possible to suppress the waveform distortion of the current waveform output from the grid interconnection inverter device. Also, even when the inductance value changes due to output fluctuations of the distributed power source, etc., the inductance value is calculated in real time according to the control state of the inverter circuit, and the current is calculated based on the calculated inductance value. The inverter circuit can be appropriately controlled so as to keep the current distortion of the waveform low.

  In the grid-connected inverter device having the above configuration, the control unit sets a control inductance for the calculated inductance calculated for the reactor inductance among the filter constants of the LC filter circuit, and controls the inverter circuit using the set control inductance. Then, it is preferable to correct the control inductance in accordance with the current distortion rate of the current waveform output from the LC filter circuit. As a result, the current waveform can be prevented from being distorted due to problems such as oscillation of the output current that may occur when the calculated inductance is used as it is for controlling the inverter circuit. In addition, since the inductance of the reactor is automatically corrected when the inverter circuit is controlled, it is possible to reduce the load required for the inspection at the time of product shipment of the reactor. Further, since it is possible to use a product whose inductance value accuracy is not high, that is, an inexpensive product with large inductance variation, the cost of the grid-connected inverter device can be kept low.

  In the grid-connected inverter device having the above configuration, the control unit uses the provisional inductance that is provisionally determined when correcting the control inductance, and the current distortion rate of the current waveform output from the LC filter circuit converges to the minimum value. Until then, it is preferable that the control inductance used for control in the inverter circuit is gradually approximated to the calculated inductance from the provisional inductance by a predetermined correction value. Thereby, the control inductance can be corrected so that the current distortion of the current waveform can be kept low by a relatively simple process.

  In the grid-connected inverter device having the above configuration, the control unit calculates the combined impedance of the inverter circuit using the voltage value of the commercial power system and the current value detected by the first current detection sensor, and calculates the calculated combined impedance. It is preferable to detect a failure of the LC filter circuit (failure of at least one of the reactor and the capacitor) based on this. In this case, since the failure of the LC filter circuit can be detected at an early stage, it is possible to prevent the output current having a large current distortion of the current waveform from being continuously supplied to the commercial power system.

  As described above, according to the present invention, it is possible to prevent the power quality of the commercial power system from being deteriorated in the grid-connected inverter device linked to the commercial power system.

FIG. 1 is a diagram showing a schematic configuration of a grid interconnection inverter device 100 according to the present embodiment. 2 shows a sine wave W1 for the current value i1 measured by the first current detection sensor 123, a sine wave W2 for the voltage value _Vac , and a sine wave for the current value i2 measured by the second current detection sensor 124. It is a figure which shows W3, respectively. Figure 3 is a diagram showing an inductance correction processing routine according to the correction calculation inductance L _a control inductance L _c set for. Figure 4 is the inductance correction processing routine of FIG. 3 is a diagram for explaining a process to approach the control inductance L _c provisional inductance L steps from _s by a predetermined correction value to calculate inductance L _a. Figure 5 is a diagram for current distortion rate Thd of the current waveform by the correction of the control inductance L _c will be described how to converge to the minimum value r1.

  Hereinafter, an embodiment according to a “system interconnection inverter device” of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, grid-connected inverter device 100 of the present embodiment is interposed between one or a plurality of distributed power generation sources (DC power supplies) 10 and commercial power system 20. It is configured. As used herein, “distributed power generation source” refers to various small-scale power generation facilities that are dispersedly arranged adjacent to a power demand area for large-scale concentrated power generation by an electric power company or the like. Typically, a natural energy power source that outputs power generated using natural energy such as sunlight, wind power, and hydropower, a power source that outputs power by waste power generation or biomass power generation, and both power and exhaust heat are output. A cogeneration power generation source, a power source using a fuel cell that extracts power by an electrochemical reaction, and the like can be used as a distributed power generation source.

  The grid-connected inverter device 100 includes an inverter circuit 110, an LC filter circuit 120, and a control unit 130.

The inverter circuit 110 functions to convert DC power (voltage value: V _dc ), which is output power output during power generation of the distributed power generation source 10, into AC power and output it. This inverter circuit 110 corresponds to the “inverter circuit” of the present invention. For this purpose, the inverter circuit 110 includes four switching elements (IPM) S1, S2, S3, and S4, all connected to the control unit 130. The inverter circuit 110 outputs a sine wave current when these switching elements S <b> 1 to S <b> 4 are on / off controlled by a control signal from the control unit 130. The control unit 130 includes a known input device, arithmetic processing unit (CPU), storage device, output device, and the like. The control unit 130 corresponds to the “control unit” of the present invention.

The LC filter circuit 120 smoothes the AC power output from the inverter circuit 110 (removes switching noise and harmonic current of the inverter circuit 110), and commercial power system of a predetermined AC voltage (voltage value: V _ac ). The mechanism which supplies to 20 is fulfilled. The LC filter circuit 120 corresponds to the “LC filter circuit” of the present invention. For this purpose, the LC filter circuit 120 includes a reactor 121 and a capacitor 122 arranged in parallel with each other. Reactor 121 is provided on an energization path between connection point P1 connecting switching element S3 and switching element S4 and connection point P2 on the commercial power system 20 side. In the LC filter circuit 120, a connection point P3 is provided between the connection point P1 and the connection point P2, and the connection point P4 that connects the switching element S1 and the switching element S2 and the connection point P5 on the commercial power system 20 side. A connection point P6 is provided therebetween. The capacitor 122 is provided between the connection point P3 and the connection point P6.

  Each LC filter circuit 120 is assigned a first current detection sensor 123 and a second current detection sensor 124 for detecting a current value. The first current detection sensor 123 is provided in an output side region (region between the connection point P3 and the connection point P2) located on the output side of the reactor 121 and the capacitor 122 in the LC filter circuit 120. The second current detection sensor 124 is provided in an input side region (region between the connection point P4 and the connection point P6) located on the input side of the reactor 121 and the capacitor 122 in the LC filter circuit 120. Information detected by these two current detection sensors 123 and 124 is transmitted to the control unit 130 for processing. Here, the first current detection sensor 123 and the second current detection sensor 124 correspond to the “first current detection sensor” and the “second current detection sensor” of the present invention, respectively.

  According to the grid-connected inverter device 100 having the above configuration, a failure detection process for detecting a failure of the LC filter circuit 120 (failure of at least one of the reactor 121 and the capacitor 122), and a filter constant (reactor) of the LC filter circuit 120 The LC calculation process for calculating the inductance L as the parameter 121 and the capacitance c) as the parameter of the capacitor 122 can be executed by the control unit 130.

(Fault detection processing)
When based on the grid interconnection regulations defined in the grid interconnection inverter device 100, the current distortion in the zero cross region of the current waveform is suppressed to a predetermined value or less, and the desired power factor (90 to 95%) of the AC power is satisfied. For this purpose, it is preferable to set the phase difference between the current value i1 detected by the first current detection sensor 123 and the voltage value _Vac of the commercial power system 20 to 0 ° as shown in FIG. Therefore, the control unit 130 causes the phase difference between the current phase of the sine wave W1 based on the current value i1 measured by the first current detection sensor 123 and the voltage phase of the sine wave W2 based on the voltage value _Vac to be 0 °. The switching elements S1 to S4 of the inverter circuit 110 can be turned on / off. During the on / off control, a phase difference θ is generated between the current phase of the sine wave W1 and the current phase of the sine wave W3 based on the current value i2 measured by the second current detection sensor 124. The control unit 130 can execute a failure detection process with reference to FIG. 3 based on the phase difference θ.

Here, when the output current from the LC filter circuit 120 is stable during the power generation of the distributed power generation source 10, the phase difference θ between the currents in the two current detection sensors 123 and 124 is determined by the detection value (current Value). More specifically, the time difference between the time when the current value detected by one current detection sensor 123 passes through the zero cross point and the time when the current value detected by the other current detection sensor 124 passes through the zero cross point is Δt, When the period of the current flowing through the LC filter circuit 120 is T, the phase difference θ is calculated by the following equation (1).

Furthermore, if the voltage value _Vac of the commercial power system 20 and the current value i1 detected by the first current detection sensor 123 are used, the combined impedance Y of the inverter circuit 110 is calculated by the following equation (2).

  Here, the synthetic impedance Y of the inverter circuit 110 can be calculated by substituting the calculation result of the equation (1) into the equation (2). On the other hand, the normal operating range Y ′ of the combined impedance Y when both the reactor 121 and the capacitor 122 are normal can be set in advance. For example, the design value of the inductance L of the reactor 121 is 4 [mH], the design value of the capacitance c of the capacitor 122 is 7.8 [μF], and each variation including variation due to aging etc. is ± 20%. In this case, the normal operating range Y ′ of the combined impedance can be set to a value of −509 to −388 [Ω], for example.

  Therefore, by comparing the calculated combined impedance Y with the normal operation range Y ′, it is possible to determine whether or not the LC filter circuit 120 has failed (occurrence of deterioration, disconnection, short circuit, etc.). Specifically, when the combined impedance Y continuously deviates from the normal operating range Y ′ for a predetermined time (for example, 30 seconds) or longer, it is determined that at least one of the reactor 121 and the capacitor 122 has failed. Can do. This determination may be performed automatically by the control unit 130 or may be performed by the operator comparing the calculation result of the combined impedance Y with the normal operating range Y ′. When the control unit 130 automatically determines the failure of the LC filter circuit 120, the determination result is output from the output device in an output form such as display output, sound output, print output, or the like. In this case, since the failure of the LC filter circuit 120 can be detected at an early stage, it is possible to prevent the output current having a large current distortion of the current waveform from being continuously supplied to the commercial power system 20.

(LC calculation process)
The current value ic in the capacitor 122 is a value obtained by subtracting the current value i1 detected by the first current detection sensor 123 from the current value i2 detected by the second current detection sensor 124 (= i2-i1). Furthermore, if the following expression (3), which is a relational expression among the current value ic in the capacitor 122, the capacitance c of the capacitor 122, the angular frequency ω, and the voltage V _ac of the commercial power system 20, is used, The capacitance c is calculated (estimated) by the following equation (4).

Further, if the following equation (5), which is a relational expression among the inductance L of the reactor 121, the capacitance c of the capacitor 122, the angular frequency ω, and the combined impedance Y of the inverter circuit 110, is used, the inductance L of the reactor 121 is obtained. Is calculated (estimated) by the following equation (6).

Here, the inductance L of the reactor 121 is a parameter required for correction of the current distortion of the current waveform, and calculating the inductance L, the calculated inductance (hereinafter, also referred to as "calculated inductance") duty corresponding to the L _a By controlling the switching elements S1 to S4 of the inverter circuit 110 on and off using the ratio, it is possible to obtain a desired current waveform in which the current distortion of the current waveform is kept low.

On the other hand, the inductance L are those constantly changing, inductance for controlling the calculation inductance L _a of the inverter circuit 110 as it is (hereinafter, also referred to as "control inductance") when used as L _c, the output current is oscillated It is assumed that the current waveform is distorted due to problems such as the above. Therefore, in the present invention, the control unit 130, by using an inductance correction process routine as shown in FIG. 3, instead of using the control of the inverter circuit 110 to calculate inductance L _a directly as a control inductance L _c, is calculated preferable to gradually correcting the control inductance L _c set for the inductance L _a.

Specifically, performing the actual control of the inverter circuit 110 while correcting the control inductance L _c set for calculating the inductance L _a calculated by LC calculation process described above. At this time, by using a correction term (= V _dc / L _c × α (preset constant)), the duty ratio Duty when the corrected control inductance L _c is used is calculated by the following equation (7). can do. In the following equation (7), the output voltage target value is V _ref , the control value based on the difference between the output voltage target value and the output voltage value (calculated value from the output current) is V _PI, and the correction is made by the control inductance L _c . Let the voltage value be _VL .

Then, the switching elements S1 to S4 of the inverter circuit 110 are on / off controlled with the duty ratio calculated by the equation (7), and the control inductance _Lc is updated based on the current value i1 and the current value i2 measured during the control ( give feedback).

  In the inductance correction processing routine shown in FIG. 3, first, in step S101, it is determined whether or not the distributed power generation source 10 is generating power and a predetermined time (for example, 60 seconds) has elapsed after the start of power generation. That is, in this step S101, it is determined whether or not the output current from the LC filter circuit 120 is stable. If the condition in step S101 is not satisfied (No in step S101), the process returns to step S101 after 1 second in step S107, and if the condition in step S101 is satisfied (Yes in step S101), the process proceeds to step S102.

In step S102, it is determined whether or not the calculated inductance L _a exceeds a value obtained by adding a preset correction value a to the provisional inductance L _s tentatively determined. In this case, the initial control inductance L _c can be given as the provisional inductance L _s (typically, the design value of the inductance L of the reactor 121). The correction value a is a correction width (adjustment width) when correcting the control inductance L _c (the provisional inductance L _{s in the} initial state). At this time, the control unit 130, the current distortion rate Thd1 current waveform output from the LC filter circuit 120 when actually controlling the inverter circuit 110 at a duty ratio corresponding to the calculated inductance L _a, a known frequency analysis It can be obtained by using. In this case, the calculated inductance L _a can be on-off controlled switching elements S1~S4 of the inverter circuit 110 at a duty ratio that is calculated by applying the equation (7). If the calculated inductance L _a exceeds the value obtained by adding the correction value a to the provisional inductance L _s (Yes in Step S102), the process proceeds to Step S103, and if not (No in Step S102), the process proceeds to Step S103a.

In step S103, sets the value of the correction value a is added to the provisional inductance _{L s} to the control inductance _{L c.} Control unit 130, the current distortion rate Thd2 current waveform output from the LC filter circuit 120 when actually controlling the inverter circuit 110 at a duty ratio corresponding to the control inductance L _c, using known frequency analysis Can be obtained by: In this case, the switching elements S1 to S4 of the inverter circuit 110 may be on / off controlled with a duty ratio calculated by applying the control inductance _Lc to the equation (7). Determining Thereafter, in step S104, whether the second current distortion rate Thd1 corresponding to the calculated inductance _{L a} later waiting exceeds the current distortion Thd2 corresponding to the control inductance _{L c.} If the current distortion rate Thd1 exceeds the current distortion rate Thd2 (Yes in step S104), the process proceeds to step S105. If the current distortion rate Thd1 is equal to or less than the current distortion rate Thd2 (No in step S104), the process proceeds to step S106.

In step S105, the provisional inductance L _s is set in step S103 based on the determination that the direction of control is correct because the current distortion rate is reduced by the update of the control inductance L _c and the state of the current waveform is improved. The updated control inductance _Lc is updated. After executing step S105, the process returns to step S101 after waiting for 1 second in step S107. In contrast, in step S106, based on the determination that incorrect orientation of the control for the condition of high becomes current waveform current distortion rate is deteriorated by updating the control inductance L _c, the control inductance L _c back to the provisional inductance L _s before the correction value a is added. After executing step S106, the process returns to step S101 after waiting for 1 second in step S107.

In particular, when satisfying the condition of step S102, the processing of steps S103 and S105 are repeated, as shown in the left illustration region of FIG. 4, the control inductance L _c are each correction value a from the provisional inductance L _s stage Thus, the correction value a is repeatedly added to the provisional inductance L _s so as to approach the calculated inductance L _a (correction value addition processing). In the process of repeating this correction value addition process, for example, the timing of the addition process when the determination result in step S104 is switched from “Yes” to “No” (the current distortion rate that has continued to decrease so far turns upward). Current distortion rate converges to the minimum value in the vicinity. For example, as shown in FIG. 5, the current distortion rate Thd gradually decreases from r3 by repeating this correction value addition process, and finally reaches the minimum value when the control inductance L _c increases to L _c (r1). converges to r1. The correction value adding process is a process to approximate the control inductance L _c to current distortion rate Thd converges to the minimum value r1 provisionally inductance L _s from the correction value a by stepwise increasing by calculating the inductance L _a.

On the other hand, it is determined in step S103a, calculated inductance L _a is whether below the value correction value a is subtracted from the provisional inductance L _s. If the calculated inductance L _a falls below the value obtained by subtracting the correction value a from the provisional inductance L _s (Yes in step S103a), the process proceeds to step S103b. If not (No in step S103a), 1 second is determined in step S107. After waiting, the process returns to step S101. In step S103b, after the correction value a from the provisional inductance _{L s} is set to subtract the values in the control inductance _{L c,} it proceeds to step S104 described above.

In particular, when satisfying the condition of step S103a, the process in step S103b and step S105 are repeated, as shown on the right-hand side regions illustrated in FIG. 4, step control inductance _{L c} are each correction value a from the provisional inductance _{L s} manner as to approach the calculated inductance L _a, the correction value a is repeatedly subtracted from the provisional inductance L _s (correction value subtraction process). In the process of repeating the correction value subtraction process, for example, the timing of the subtraction process when the determination result in step S104 is switched from “Yes” to “No” (the current distortion rate that has continued to decrease until then turns upward). Current distortion rate converges to the minimum value in the vicinity. For example, as shown in FIG. 5, by repeating this correction value subtraction process, the current distortion rate Thd gradually decreases from r2, and finally reaches the minimum value when the control inductance L _c decreases to L _c (r1). converges to r1. The correction value subtraction process is a process to approximate the control inductance L _c to current distortion rate Thd converges to the minimum value r1 provisionally inductance L _s from the correction value a by stepwise reduced by calculating the inductance L _a.

In the above-described inductance correction processing routine, whether the correction value addition processing in step S103 is executed according to the value of the calculated inductance L _a relative to the relative value of the temporary inductance L _s and the correction value a (temporary inductance L _s Whether the provisional inductance L _s is brought close to the calculated inductance L _a while adding the correction value a), or whether the correction value subtraction process in step S103b is executed (subtracting the correction value a from the provisional inductance L _s interim inductance L _s or closer to calculate the inductance L _a) is determined.

Specifically, for example calculating the inductance _{L a} is 4.5 [mH], provisional inductance _{L s} is 4 [mH], when the correction value is 0.1 [mH], the steps in the first routine proceeds from S102 to step S103, the control inductance _{L c} by the correction value addition process in step S103 is set to 4.1 (= 4 + 0.1) [ mH]. Thereafter, when satisfying the condition of step S104, the control inductance _{L c} is 4.2 in the second routine (= 4.1 + 0.1) is set to [mH], 4.3 in the third routine (= 4.2 + 0.1) [mH]. Similarly, for example, when the calculated inductance L _a is 3.5 [mH], the provisional inductance L _s is 4 [mH], and the correction value is 0.1 [mH], the first routine starts from step S103a. proceeds to step S103b, the control inductance _{L c} by the correction value subtraction process in step S103b is set to 3.9 (= 4-0.1) [mH] . Thereafter, when the condition of step S104 is satisfied, the control inductance L _c is set to 3.8 (= 3.9−0.1) [mH] in the second routine, and 3 in the third routine. .78 (= 3.8−0.1) [mH]. As a result, in any case, it can be carried out gradually closer Such correction current distortion rate is calculated inductance L _a control inductance L _c to minimize 4.5 [mH]. In this case, the final corrected control inductance L _c are calculated inductance may be addressed in a match for the L _a, or calculated inductance L _a may have a slight deviation between.

According to the inductance correction processing routine, it is possible to suppress the current distortion to the desired level by correcting the control inductance L _c as current distortion does not increase in the zero-crossing region of the current waveform. In particular, by approaching the control inductance L _c provisional inductance L _s from the correction value a by stepwise calculated inductance L _a, the control inductance L _c as current distortion of the current waveform is kept low by a relatively simple process It can be corrected. In this case, since the inductance L of the reactor 121 is automatically corrected when the inverter circuit 110 is controlled, the load required for the inspection of the reactor 121 at the time of product shipment can be reduced. In addition, since it is possible to use a product whose inductance value accuracy is not high, that is, an inexpensive product with a large inductance variation, the cost of the grid-connected inverter device 100 can be kept low. In addition, the amount of power generated by the distributed power generation source 10 using solar light or wind power is likely to fluctuate due to the influence of natural conditions, etc., but the inductance value changes due to the output fluctuation from the distributed power generation source 10. Even in such a case, the inductance value is calculated in real time according to the control state of the inverter circuit 110, and the inverter circuit 110 is appropriately controlled so as to suppress the current distortion of the current waveform based on the calculated inductance value. it can.

  The present invention is not limited to the above exemplary embodiment, and various applications and modifications are possible. For example, each of the following embodiments to which the above embodiment is applied can be implemented.

In the above embodiment has been described with regard to a case of correcting the calculated inductance L _a further inductance correction process routine calculated by LC calculation process, in the present invention, as it is calculated inductance L _a without executing the inductance correction processing routine You may use for control of the inverter circuit 110. FIG.

The inductance correction process routine of the above embodiment has been described with regard to the form of current distortion factor of the current waveform output from the LC filter circuit 120 corrects the control inductance L _c to converge to a minimum, in the present invention, It includes this form, various forms of correcting the control inductance L _c in accordance with the current distortion of the current waveform output from the LC filter circuit 120 are included. For example, it is possible to adopt a form in which the control inductance L _c is corrected until the current distortion rate itself of the current waveform reaches a specified value, or until the change amount or change rate of the current distortion rate reaches a specified value.

The inductance correction process routine of the above embodiments, the correction logic to correct so as to approach the control inductance L _c used for controlling the inverter circuit 110 to the provisional inductance L steps from _s by a predetermined correction value a to calculate inductance L _a Although described, in the present invention, a correction logic different from this correction logic can be adopted. For example, as the control inductance L _c approaches the calculated inductance L _a, or as current distortion of the current waveform is reduced, can also be modified to reduce the correction value a.

  In the failure detection process of the above-described embodiment, the case where it is determined whether or not the LC filter circuit 120 has failed based on the comparison result between the calculated combined impedance Y and the normal operation range Y ′ has been described. Then, determination logic for determining whether or not the LC filter circuit 120 is out of order based on a comparison result between the calculated combined impedance Y and a predetermined specified value may be employed.

  In the above embodiment, the case where both the failure detection process and the LC calculation process are executed by the control unit 130 has been described. However, in the present invention, any of the failure detection process and the LC calculation process is performed by the control unit 130. Only one of these processes may be executed.

  When based on description of said embodiment and various modifications, this invention can take the following each aspects (aspect).

In the present invention,
"An inverter circuit that converts the output power at the time of power generation of the distributed power generation source into AC power and outputs it,
An LC filter circuit including a reactor and a capacitor arranged in parallel, and smoothing AC power output from the inverter circuit and supplying the AC power to a commercial power system;
In a grid interconnection inverter device comprising:
The inverter circuit is controlled based on the current phase and the voltage phase in the LC filter circuit during power generation of the distributed power generation source, and information on the current value flowing in the output side region of the LC filter circuit and the LC filter circuit A method for controlling a grid-connected inverter device, comprising: calculating a filter constant of the LC filter circuit based on both information relating to a current value flowing through the input side region of the LC filter circuit. "
The mode (mode 1) can be adopted.
According to this aspect 1, the filter constant of the LC filter circuit during the control of the inverter circuit can be calculated with high accuracy, and the calculated filter constant can be reflected in the control of the inverter circuit.

In the present invention,
“A control method of the grid interconnection inverter device according to aspect 1,
A control inductance is set for the calculated inductance calculated for the inductance of the reactor among the filter constants of the LC filter circuit, and output from the LC filter circuit when the inverter circuit is controlled using the set control inductance A control method for a grid-connected inverter device, comprising a step of correcting the control inductance according to a current distortion rate of a current waveform to be performed. "
The mode (mode 2) can be adopted.
According to this aspect 2, it is possible to prevent the current waveform from being distorted due to a problem such as oscillation of the output current that may occur when the calculated inductance is directly used for controlling the inverter circuit.

In the present invention,
“A control method of the grid interconnection inverter device according to aspect 2,
In the step of correcting the calculated inductance, the provisional inductance determined provisionally is used, and the control inductance is determined from the provisional inductance until the current distortion rate of the current waveform output from the LC filter circuit converges to a minimum value. A method for controlling a grid-connected inverter device, which gradually approaches the calculated inductance step by step. "
The mode (mode 3) can be employed.
According to this aspect 3, it is possible to correct the control inductance so that the current distortion of the current waveform is kept low by a relatively simple process.

In the present invention,
“A control method for a grid interconnection inverter device according to any one of the first to third aspects,
A combined impedance of the inverter circuit is calculated using a voltage value of the commercial power system and a current value detected by the first current detection sensor, and a failure of the LC filter circuit is detected based on the calculated combined impedance A method for controlling a grid-connected inverter device, comprising the step of: "
The aspect (Aspect 4) can be adopted.
According to this aspect 4, since the failure of the LC filter circuit can be detected at an early stage, it is possible to prevent the output current with a large current distortion of the current waveform from being continuously supplied to the commercial power system.

  DESCRIPTION OF SYMBOLS 10 ... Distributed power generation source, 20 ... Commercial power system, 100 ... Grid connection inverter apparatus, 110 ... Inverter circuit, 120 ... LC filter circuit, 121 ... Reactor, 122 ... Capacitor, 123 ... First current detection sensor, 124 ... 2nd current detection sensor, 130 ... control part, S1, S2, S3, S4 ... switching element

Claims (4)

A grid-connected inverter device interposed between a distributed power generation source and a commercial power system,
An inverter circuit that converts the output power during power generation of the distributed power generation source into AC power and outputs the AC power;
An LC filter circuit including a reactor and a capacitor arranged in parallel with each other, and smoothing AC power output from the inverter circuit and supplying the AC power to the commercial power system;
A first current detection sensor provided in an output side region of the LC filter circuit;
A second current detection sensor provided in the input side region of the LC filter circuit;
The inverter circuit is controlled based on a current phase and a voltage phase in the LC filter circuit during power generation of the distributed power generation source, and information on a current value detected by the first current detection sensor and the second current A control unit that calculates a filter constant of the LC filter circuit based on both information on the current value detected by the detection sensor;
A grid interconnection inverter device. The grid-connected inverter device according to claim 1,
The control unit sets a control inductance with respect to the calculated inductance calculated for the inductance of the reactor among the filter constants of the LC filter circuit, and controls the inverter circuit using the set control inductance. A grid-connected inverter device that corrects the control inductance in accordance with a current distortion rate of a current waveform output from an LC filter circuit. A grid interconnection inverter device according to claim 2,
The control unit uses the provisional inductance provisionally determined when correcting the control inductance, and the control inductance is used until the current distortion rate of the current waveform output from the LC filter circuit converges to a minimum value. A grid-connected inverter device that gradually approaches the calculated inductance from a provisional inductance by a predetermined correction value. It is a grid connection inverter apparatus as described in any one of Claims 1-3,
The control unit calculates a combined impedance of the inverter circuit using a voltage value of the commercial power system and a current value detected by the first current detection sensor, and the LC filter based on the calculated combined impedance A grid-connected inverter device that detects circuit failures.

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