阅读说明：本技术 接地检测器以及功率调节器 (Ground fault detector and power conditioner ) 是由 胜仓朋也 氏家智亲 木下雅博 于 2017-07-18 设计创作，主要内容包括：功率调节器具备：逆变器电路,将从正极输入端子与负极输入端子输入的直流电压转换为交流电压；分压电路,一端连接于正极输入端子,另一端连接于负极输入端子；以及接地检测器,被输入由分压电路分压后的电压作为输入电压信号,基于输入电压信号的电压的大小,对发生了接地这一情况进行检测。接地检测器在输入电压信号包含具有第一频率以上的频率的第一电压信号、并且第一电压信号相对于交流接地基准电位的偏差为交流接地检测电压以上时,发出交流接地检测信号。接地检测器也可以包括：频率滤波器,使第一电压信号通过；低通滤波器,使确定为比第一频率低的第二频率以下的第二电压信号通过；以及电压比较部,基于第一电压信号与第二电压信号发出交流接地检测信号以及直流接地检测信号。(The power conditioner is provided with: an inverter circuit that converts a direct-current voltage input from a positive input terminal and a negative input terminal into an alternating-current voltage; a voltage dividing circuit, one end of which is connected with the positive input terminal and the other end of which is connected with the negative input terminal; and a ground fault detector to which the voltage divided by the voltage dividing circuit is input as an input voltage signal, and which detects that a ground fault has occurred based on the magnitude of the voltage of the input voltage signal. The ground fault detector generates an alternating-current ground fault detection signal when the input voltage signal includes a first voltage signal having a frequency equal to or higher than a first frequency and a deviation of the first voltage signal from an alternating-current ground fault reference potential is equal to or higher than an alternating-current ground fault detection voltage. The ground fault detector may also include: a frequency filter passing the first voltage signal; a low-pass filter that passes a second voltage signal that is determined to be a second frequency lower than the first frequency or lower; and a voltage comparison unit that generates an alternating current ground detection signal and a direct current ground detection signal based on the first voltage signal and the second voltage signal.)

1. A power conditioner is provided with:

an inverter circuit that converts a direct-current voltage input via a positive input terminal and a negative input terminal into an alternating-current voltage;

a voltage divider circuit having one end connected to the positive input terminal and the other end connected to the negative input terminal; and

a ground fault detector to which the voltage divided by the voltage dividing circuit is input as an input voltage signal, and which detects that a ground fault has occurred based on a magnitude of the voltage of the input voltage signal,

the ground fault detector generates an alternating current ground fault detection signal when the input voltage signal includes a first voltage signal having a frequency equal to or higher than a predetermined first frequency and a deviation of the first voltage signal from a predetermined alternating current ground fault reference potential is equal to or higher than a predetermined alternating current ground fault detection voltage.

2. The power regulator of claim 1,

the ground fault detector includes:

a frequency filter to which the input voltage signal is input, which passes the first voltage signal, and which blocks a signal having a frequency lower than the first frequency;

a low-pass filter to which the input voltage signal is input, which passes a second voltage signal that is determined to be lower than the first frequency and lower than a second frequency, and which blocks a signal having a frequency higher than the second frequency; and

and a voltage comparison unit that generates the ac ground detection signal when a deviation of the first voltage signal from the ac ground reference potential is equal to or greater than the ac ground detection voltage, and generates the dc ground detection signal when a deviation of the second voltage signal from a predetermined dc ground reference potential is equal to or greater than a predetermined dc ground detection voltage.

3. The power regulator of claim 2,

the frequency filter blocks signals having a frequency higher than a third frequency determined to be higher than the first frequency.

4. The power conditioner of any one of claims 1 to 3,

the power conditioner includes at least one of a reporting unit that reports an ac ground in response to the ac ground detection signal, and a recording unit that records an occurrence history of the ac ground in response to the ac ground detection signal.

5. A ground fault detector is provided with:

a frequency filter to which an input voltage signal is input, which passes a first voltage signal having a frequency equal to or higher than a predetermined first frequency and blocks a signal having a frequency lower than the first frequency;

a low-pass filter to which the input voltage signal is input, which passes a second voltage signal determined to be a second frequency lower than the first frequency or lower, and which blocks a signal having a frequency higher than the second frequency; and

and a voltage comparison unit that generates an ac ground detection signal when a deviation of the first voltage signal from a predetermined ac ground reference potential is equal to or greater than a predetermined ac ground detection voltage, and generates a dc ground detection signal when a deviation of the second voltage signal from a predetermined dc ground reference potential is equal to or greater than a predetermined dc ground detection voltage.

Technical Field

The invention relates to a ground fault detector and a power conditioner.

Background

The power conditioner is provided with an inverter circuit. The dc voltage from the solar cell panel is input to the input side of the inverter circuit. When grounding occurs in a path from the solar cell panel to the input side of the inverter circuit, direct current grounding occurs. In order to detect the dc ground, a ground detector is provided on the input side of the inverter circuit. In this regard, as disclosed in, for example, japanese patent laid-open No. 2001-218474, a device for detecting the ground of a circuit including an inverter circuit is known.

The inverter circuit performs dc/ac conversion, and an ac current flows on the output side of the inverter circuit. Unlike dc grounding on the input side, ac grounding on the ac side occurs. Conventionally, as a ground fault detector for detecting an ac ground fault, a ground overvoltage relay (so-called OVGR) is provided on the output side of an inverter circuit of a power conditioner.

Disclosure of Invention

Problems to be solved by the invention

Conventionally, it is essential to provide a ground fault detector on the output side of the inverter circuit in order to accurately detect the ac ground fault. Therefore, there is a problem that the circuit configuration on the output side of the inverter circuit becomes complicated or the circuit installation space increases. The present inventors have conducted extensive studies and, as a result, have found a new device configuration capable of detecting an ac ground without using an OVGR on the output side of an inverter circuit.

The present invention has been made to solve the above-described problems, and an object thereof is to provide a ground fault detector and a power conditioner capable of detecting an ac ground fault by dividing the ac ground fault without using a ground fault detector on the output side of an inverter circuit.

Means for solving the problems

The power conditioner of the present invention comprises: an inverter circuit that converts a direct-current voltage input via a positive input terminal and a negative input terminal into an alternating-current voltage; a voltage divider circuit having one end connected to the positive input terminal and the other end connected to the negative input terminal; and a ground fault detector that receives the voltage divided by the voltage divider circuit as an input voltage signal and detects occurrence of a ground fault based on a magnitude of the voltage of the input voltage signal, wherein the ground fault detector generates an ac ground fault detection signal when the input voltage signal includes a first voltage signal having a frequency equal to or higher than a predetermined first frequency and a deviation of the first voltage signal from a predetermined ac ground reference potential pair is equal to or higher than a predetermined ac ground fault detection voltage.

The ground fault detector of the present invention comprises: a frequency filter to which an input voltage signal is input, which passes a first voltage signal having a frequency equal to or higher than a predetermined first frequency and blocks a signal having a frequency lower than the first frequency; a low-pass filter to which the input voltage signal is input, which passes a second voltage signal determined to be a second frequency lower than the first frequency or lower, and which blocks a signal having a frequency higher than the second frequency; and a voltage comparison unit that generates an ac ground detection signal when a deviation of the first voltage signal from a predetermined ac ground reference potential is equal to or greater than a predetermined ac ground detection voltage, and generates a dc ground detection signal when a deviation of the second voltage signal from a predetermined dc ground reference potential is equal to or greater than a predetermined dc ground detection voltage.

Effects of the invention

Since the ac ground waveform is transmitted from the output side to the input side in the inverter circuit, the ac ground waveform can be detected even with the input-side ground detector for dc ground detection. Since the voltage waveforms are different between the dc ground and the ac ground, the ac ground can be detected when a signal having a first frequency or higher is included by utilizing the difference in the waveforms. This allows the ac ground to be distinguished and detected by the ground detector on the input side of the inverter circuit.

Drawings

Fig. 1 is a circuit block diagram showing an electric power system including a ground fault detector and a power conditioner according to an embodiment of the present invention.

Fig. 2 is a circuit block diagram of a ground fault detector of an embodiment of the present invention.

Fig. 3 is a waveform diagram for explaining an operation of the ground fault detector according to the embodiment of the present invention.

Fig. 4 is a waveform diagram for explaining an operation of the ground fault detector according to the embodiment of the present invention.

Fig. 5 is a circuit block diagram of a ground fault detector according to a modification of the embodiment of the present invention.

Detailed Description

Fig. 1 is a circuit block diagram showing a power system 1 including a ground fault detector 16 and a power conditioner 10 according to an embodiment of the present invention. In the embodiment, the power system 1 is a solar power generation system as an example. The power system 1 includes a solar cell panel 2 as a dc power supply, a stand 3 for fixing the solar cell panel 2, a connection box 4 interposed between the solar cell panel 2 and a power conditioner 10, the power conditioner 10 for converting dc power into ac power, and a main circuit inlet 20. The power system 1 is connected to system power sources 24 to 26 and a household electrical appliance load (not shown) via a main circuit lead-in board 20. The main circuit drawing board 20 is provided with a main circuit breaker 22.

The power conditioner 10 includes a positive input terminal 5a, a negative input terminal 5b, an inverter circuit 14, a voltage divider circuit 12, a ground fault detector 16, a reporting unit 17a, a recording unit 17b, and a circuit breaker 18. The inverter circuit 14 converts a dc voltage input via the positive input terminal 5a and the negative input terminal 5b into an ac voltage. The inverter circuit 14 is a three-phase inverter circuit having R, S, T three phases, and has three sets of arm circuits each including two semiconductor switching elements.

The voltage dividing circuit 12 is a series circuit of a resistor R1 and a resistor R2. One end of the voltage dividing circuit 12 is connected to the positive input terminal 5a, and the other end of the voltage dividing circuit 12 is connected to the negative input terminal 5 b. The connection point of the resistor R1 and the resistor R2 is grounded. The voltage at the connection point of the resistor R1 and the resistor R2 is the neutral point potential Vc.

The neutral point potential Vc is input to the ground detector 16 as an input voltage signal S0. The ground detector 16 detects that grounding has occurred based on the magnitude of the voltage of the input voltage signal S0. The ground fault detector 16 is connected to the reporting unit 17a, the recording unit 17b, and the breaker 18. Breaker 18 is disposed on the output side of inverter circuit 14. When the circuit breaker 18 is operated, the electrical connection of the power conditioner 10 with the main circuit drawing pad 20 is cut off. In fig. 1, a ground current path when dc grounding occurs is indicated by a broken line.

Fig. 2 is a circuit block diagram of ground fault detector 16 according to the embodiment of the present invention. The ground fault detector 16 includes a frequency filter 161, a low-pass filter 162, a voltage comparator 163, a dc ground fault detection terminal 165, and an ac ground fault detection terminal 166.

The frequency filter 161 is a band pass filter. The frequency filter 161 passes only signals having frequencies within a predetermined frequency range. That is, the frequency filter 161 can block the signal having the first frequency f₁₁A signal of a lower frequency and having a higher frequency f than the third frequency₁₂A high frequency signal. Thus, when the input voltage signal S0 is input to the frequency filter 161, the frequency filter 161 can be made to have only the first frequency f₁₁Above and a third frequency f₁₂The first voltage signal S1 of the following frequency passes. Third frequency f₁₂Is determined to be higher than the first frequency f₁₁High, specifically, the first frequency f may be set₁₁Set to 45 Hz, the third frequency f₁₂Set to 65 hz. Accordingly, only the signal having the frequency of 45 to 65 hz can be selectively passed, and therefore the electric signal having the frequency of 50 hz or 60 hz can be accurately extracted from the input voltage signal S0. In addition, the numerical value of the frequency is an example.

When the input voltage signal S is inputted to the low pass filter 162At 0, the low pass filter 162 blocks the signal having the second frequency f₂A high frequency signal. Thus, the low pass filter 162 can only have the second frequency f₂The second voltage signal S2 of the following frequency passes. Second frequency f₂Is determined to be higher than the first frequency f₁₁Low frequency. Second frequency f₂It may be 5 Hz or 1 Hz. This allows only a signal having a sufficiently low frequency to selectively pass therethrough, and therefore, it is possible to eliminate a frequency component due to the ac ground and detect only a voltage variation due to the dc ground. In addition, the numerical value of the frequency is an example.

The voltage comparing part 163 includes a first comparator 163a, an absolute value generating part 164, and a second comparator 163 b. The voltage comparing unit 163 compares the first voltage signal S1 and the second voltage signal S2 with an ac ground detection voltage V that is a predetermined voltage_ref1And direct current ground detection voltage V_ref2A comparison is made. Hereinafter, the ground fault detection operation of ground fault detector 16 will be described together with the configuration of voltage comparing unit 163, with reference to fig. 2 to 4. Fig. 3 and 4 are waveform diagrams for explaining the operation of ground fault detector 16 according to the embodiment of the present invention.

First, an ac ground detection operation will be described. When the voltage value of the first voltage signal S1 becomes the ac ground detection voltage V_ref1In the above case, the output signal of the first comparator 163a is at a high level. The high level signal is an ac ground detection signal SAC. Ac ground detection signal SAC is output to the outside of ground detector 16 via ac ground detection terminal 166.

In fig. 3, an ac ground waveform 30 is shown. In the case of the ac ground shown in fig. 3, the neutral point potential Vc periodically fluctuates. This variation is based on the voltage frequency on the output side of the inverter circuit 14. Since the system power sources 24 to 26 and the system interconnection system, which are commercial systems, are constructed, the inverter circuit 14 outputs a voltage of 50 hz or 60 hz. Therefore, the periodic variation in the neutral point potential Vc when the ac ground occurs has a frequency of 50 hz or 60 hz.

Due to input voltage when AC is groundedThe signal S0 has a frequency of 50 hz or 60 hz, so the input voltage signal S0 is blocked by the low-pass filter 162, while the input voltage signal S0 passes through the frequency filter 161 to become the first voltage signal S1. The first voltage signal S1 is compared with the AC ground detection voltage V by the first comparator 163a_ref1A comparison is made. In the first voltage signal S1 with respect to the AC ground reference potential V as shown in FIG. 3_C01Deviation A1 of (A) is AC ground detection voltage V_ref1In this case, the first comparator 163a sends the ac ground detection signal SAC. By differentiating and detecting the ac ground, it is possible to quickly determine that there is a fault on the output side of the inverter circuit 14.

Alternatively, as shown in fig. 3, the first voltage signal S1 may be set to the ac ground reference potential V_C01With + V as the ac ground detection voltage, a1_ref1The comparison is made, but not limited thereto. As a modification, the first voltage signal S1 may be set to the ac ground reference potential V_C01with-V of the deviation on the negative potential side of_ref1A comparison is made.

Next, a dc ground detection operation will be described. The absolute value generator 164 converts the voltage value of the second voltage signal S2 into an absolute value. When the absolute value of the second voltage signal S2 becomes the DC ground detection voltage V_ref2In the above case, the output signal of the second comparator 163b is at a high level. The high level signal is a dc ground detection signal SDC. The dc ground detection signal SDC is output to the outside of the ground detector 16 via the dc ground detection terminal 165.

In fig. 4, an N-phase dc-ground waveform 31 and a P-phase dc-ground waveform 32 are shown. In the case of dc-grounding as shown in fig. 4, the neutral point potential Vc varies only unilaterally on the P side or the N side. In the case of dc-grounding, a waveform having only one peak or valley appears in the neutral point potential Vc, and the neutral point potential Vc does not repeat periodic fluctuations.

When dc-grounding occurs, since the input voltage signal S0 has only a sufficiently low frequency, the input voltage signal S0 passes through the low pass filter 162 to become the second voltage signal S2,on the other hand, the input voltage signal S0 is blocked by the frequency filter 161. The second voltage signal S2, after being converted into an absolute value, is then compared with the dc ground by the second comparator 163b to detect the voltage V_ref2A comparison is made. As shown in fig. 4, the second voltage signal S2 is at a reference potential V with respect to the dc ground reference potential_C02The deviation A2 is the DC ground detection voltage V_ref2In this case, the second comparator 163b outputs the dc ground detection signal SDC. By differentiating and detecting the dc ground, it can be quickly determined that there is a fault on the input side of the inverter circuit 14.

When both the dc ground and the ac ground occur, the low frequency component of the input voltage signal S0 passes through the low pass filter 162 to become the second voltage signal S2, while the high frequency component of the input voltage signal S0 passes through the frequency filter 161 to become the first voltage signal S1. Thus, since the ac ground detection and the dc ground detection are independently operated, both the ac ground detection signal SAC and the dc ground detection signal SDC can be output.

In the first embodiment, the neutral point potential Vc of the voltage divider circuit 12 is set to the ground potential. Since the ground is detected based on the voltage variation from the neutral point potential Vc, the ac ground reference potential V_C01And a DC ground reference potential V_C02Set to zero volts. AC ground reference potential V_C01And AC ground detection voltage V_ref1Can be predetermined as a value for accurately detecting the AC ground, the DC ground reference potential V_C02And direct current ground detection voltage V_ref2Can be predetermined as a value for accurately detecting the direct current ground. The detection conditions of the dc ground and the ac ground may be common to each other or different from each other. AC ground reference potential V_C01And a DC ground reference potential V_C02The same potential may be set, specifically, both potentials may be set to zero volts. Or, the AC ground reference potential V is set_C01And a DC ground reference potential V_C02One of them is set to be higher than the other and the two are set to different potentials. AC ground detection voltage V_ref1Detecting the voltage V with DC ground_ref2The voltage values may be the same, or may be different from each other by making one higher than the other.

Since the ac ground waveform is transmitted from the output side to the input side of the inverter circuit 14, the ac ground waveform is also input to the ground detector 16 provided on the input side of the inverter circuit 14. Since the voltage waveforms are different between the dc ground and the ac ground, according to the embodiment, the first frequency f can be included by utilizing the difference in the waveforms₁₁The ac ground is detected when the signal has the above frequency. This allows the ac ground to be detected while being discriminated by the ground detector 16 on the input side of the inverter circuit 14. The ac ground can be distinguished and detected without using the OVGR on the output side of the inverter circuit 14. Furthermore, since ground fault detector 16 of the embodiment generates dc ground fault detection signal SDC and ac ground fault detection signal SAC, it is possible to distinguish between generation of only dc ground, generation of only ac ground, and generation of both of dc ground and ac ground.

The reporting unit 17a reports ac ground in response to the ac ground detection signal SAC and reports dc ground in response to the dc ground detection signal SDC. When both ac grounding and dc grounding occur, both ac grounding and dc grounding can be reported. The recording unit 17b records a grounding occurrence history in response to the ac grounding detection signal SAC and the dc grounding detection signal SDC. The recording unit 17b can record the waveform of the input voltage signal S0 when at least one of the dc ground and the ac ground is generated in the readable recording medium. By removing the readable recording medium from the recording unit 17b, the external electronic computer can read the ground waveform. When ground fault detector 16 generates at least one of dc ground fault detection signal SDC and ac ground fault detection signal SAC, circuit breaker 18 trips.

Fig. 5 is a circuit block diagram of ground fault detector 116 according to a modification of the embodiment of the present invention. The ground detector 116 does not include the low-pass filter 162, and includes a ground detection terminal 265 instead of the dc ground detection terminal 165. Since there is no low-pass filter 162, the input voltage signal S0 is input to the voltage comparing section 163 as it is. The absolute value generator 164 inputs the absolute value of the input voltage signal S0 to the second comparator 163 b.

First, when the dc ground occurs, the absolute value of the dc ground waveform of fig. 4 is input to the second comparator 163b in the ground detector 116. Therefore, even if the ground detector 116 is used, the dc ground can be detected by the voltage comparison in the second comparator 163b as in the ground detector 16. In this case, the ground detector 116 outputs a ground detection signal SX from the ground detection terminal 265. Further, since the frequency filter 161 is provided, the ac ground detection signal SAC is not output.

On the other hand, when the ac ground occurs, the ac ground waveform 30 of fig. 3 is input to the first comparator 163a through the frequency filter 161 in the ground detector 116. As a result, ac ground is detected and ac ground detection signal SAC is output from ac ground detection terminal 166. Since the ground fault detector 116 does not include the low-pass filter 162, the ac ground waveform 30 is converted by the absolute value generator 164 and then input to the second comparator 163 b. As a result, even when the ac ground occurs, the ground detection signal SX is output from the ground detection terminal 265.

In the ground fault detector 116 described above, when at least one of the ac ground and the dc ground is detected based on the magnitude of the voltage of the input voltage signal S0, a ground fault detection signal SX is output. Further, it is possible to distinguish between the ac ground and the dc ground according to the presence or absence of the ac ground detection signal SAC.

In the circuit configuration of fig. 2 and 5, the P-phase dc ground waveform 32 and the N-phase dc ground waveform 31 are identical to the dc ground detection voltage V by providing the absolute value generator 164_ref2The comparison is performed, but is not necessarily limited thereto. As a modification, the voltage fluctuation to the negative side may be compared with-V shown in FIG. 3 without taking the absolute value_ref2And (6) comparison. As a further modification, the P-phase ground and the N-phase ground may be detected by discriminating between positive and negative voltages, or the difference between the P-phase ground and the N-phase may be reported by the reporting unit 17a or recorded by the recording unit 17 b. Also can be used forThe DC ground detection side judges not only the absolute value but also the polarity, thereby more accurately determining which wiring of the P phase and the N phase has a fault.

Description of the reference numerals

1 power system, 2 solar cell panel, 3 stands, 4 junction box, 5a positive input terminal, 5b negative input terminal, 10 power regulator, 12 voltage divider circuit, 14 inverter circuit, 16, 116 ground fault detector, 17a report section, 17b recording section, 18 circuit breaker, 20 main circuit lead-in board, 22 main circuit breaker, 24-26 system power supply, 30 ac ground waveform, 31 phase dc ground waveform, 32 phase dc ground waveform, 161 frequency filter, 162 low pass filter, 163 voltage comparison section, 163a first comparator, 163b second comparator, 164 absolute value generation section, 165 dc ground fault detection terminal, 166 ac ground fault detection terminal, 265 ground fault detection terminal, a1, a2 deviation, f₁₁First frequency, f₁₂Third frequency, f₂A second frequency, an R1 resistor, an R2 resistor, an S0 input voltage signal, an S1 first voltage signal, an S2 second voltage signal, a SAC AC ground detect signal, a SDC DC ground detect signal, an SX ground detect signal, a Vc neutral potential, a V1 resistor, a S2 resistor, a S0 input voltage signal, a S1 first voltage signal, a S2 second voltage signal, a SAC AC ground detect signal, a_C01AC ground reference potential, V_C02DC ground reference potential, V_ref1AC ground detection voltage, V_ref2The voltage is detected dc-ground.