JPH08130830A - Device for detecting independent operation of distributed power source - Google Patents

Abstract

PURPOSE: To surely detect the independent operation of a distributed power source with a simple circuit configuration by detecting the voltage fluctuation of a system at which disturbance is generated due to the cut off of the system by means of an independent operation detecting circuit based on the fluctuation of active power caused by a current control signal generated on the basis of a reference waveform signal. CONSTITUTION: A multiplying circuit 29 generates an output current command circuit S3 by multiplying the output of an output power command generating circuit 28 by the output of a reference waveform generating circuit 27. An AC device 30 detects the output current of a high-frequency inverter 13 which is full-wave rectified by means of a rectifier 16 and an adding circuit 31 adds the output current of the inverter 13 to the output current command signal S3 of the circuit 29. Then an output current control circuit 32 generates an output current control signal S4 and a pulse generating circuit 34 drives the inverter 13 based on the signal S4 . When a system is cut off, the fluctuation of active power caused by the control signal S4 appears in the fluctuation of the voltage Vs of the system due to the cut off and an independent operation detecting circuit detects the fluctuation of the voltage Vs .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an isolated operation detecting device for a distributed power source, and more specifically, it is used in a solar power generation system or the like in which a distributed power source including a solar cell and an inverter is connected to a system power source, and is used as a system disconnection. The present invention relates to a device for detecting the isolated operation of a distributed power source that detects the isolated operation of the inverter by the active method.

[0002]

2. Description of the Related Art For example, as shown in FIG. 3, in a solar power generation system, a distributed power source 3 including a solar cell 1 which is a DC power source and an inverter 2 which converts the DC power generated from the solar cell 1 into an alternating current is connected. Power is supplied to the load 6 from the solar cell 1 or the system power source 5 by connecting to the system power source 5 via the system switch 4.

[0003] Here, when a system power failure occurs due to a system disconnection due to construction, if the distributed power source 3 is still connected to the disconnection point A, the inverter 2 is operated independently to start the construction section. There is a risk of reverse charging to which the generated voltage from the dispersed power source 3 is applied, and there is a risk of electric shock to the construction worker.

Therefore, in order to prevent the electric shock accident, the islanding operation of the inverter 2 due to the grid disconnection is detected, the islanding operation of the inverter 2 is stopped based on the detection signal, and the grid interconnection switch 4 is turned on. It is necessary to open it and disconnect the distributed power source 3 from the system. In general, as a method of detecting the islanding operation of the inverter 2 due to the grid disconnection,
There are two types, passive and active.

[0005] A typical passive method is to detect a phase jump of the load voltage that occurs when the inverter 2 is operated independently due to the grid disconnection. On the other hand, in the completely balanced state in which the output power of the inverter 2 and the power consumption of the load 6 are equal, no change occurs in the system during disconnection, and therefore the passive method cannot detect. Therefore, in the active method, the output power of the inverter 2 is constantly fluctuated due to the occurrence of disturbance to destroy the perfectly balanced state, and the inverter 2 based on the grid disconnection is used.
Is detected by inducing voltage fluctuations or frequency fluctuations of the load voltage during islanding.

[0006]

By the way, the above-mentioned active-system inverter independent operation detection includes a frequency fluctuation method, a power fluctuation method, and a high-frequency voltage monitoring method, which will be described below. The frequency variation method is to detect a shift of the inverter output frequency by a feedback effect when the distribution line is stopped by shifting the phase of the system voltage input to the inverter control circuit by a certain amount [JP-A-3-256534]. Gazette]. Further, the power fluctuation method is to detect the power output from the inverter by vibrating it at a low frequency and breaking the balance [JP-A-3-23].
No. 9124]. Further, the high-frequency voltage monitoring method has a third, fifth, and fifth output voltage of the inverter when the load power consumption and the output power of the inverter are completely balanced.
The detection is made by increasing the seventh harmonic.

Such detection of the isolated operation of the inverter is one of the most important items in terms of safety as a measure for preventing the isolated operation, and it is technically difficult, so that the safety and reliability of the inverter can be improved. In order to improve the above, the present situation is that a new means for detecting an isolated operation other than the above-mentioned three methods is required.

Therefore, the present invention has been proposed in view of the above-mentioned present situation, and an object of the present invention is to independently operate a distributed power source based on a new active method capable of detecting the independent operation of an inverter due to a grid disconnection. It is to provide a detection device.

[0009]

As technical means for achieving the above object, when the present invention is applied to a high frequency insulation type, the following constitutional requirements are provided.

That is, a small-capacity distributed power source in which a DC power source and a high-frequency inverter are coupled to a rectifier and a low-frequency inverter via a high-frequency insulation transformer is connected to a power system.
An independent operation detection device for a distributed power supply by an active method, which detects an isolated operation of an inverter by a grid disconnection from a fluctuation of a system voltage that appears due to disturbance occurrence based on active power fluctuation,

A PLL circuit for generating a phase reference signal synchronized with the system voltage and a reference waveform signal in which the amplitude of the full-wave rectified waveform is increased or decreased by a predetermined cycle at regular intervals based on the output of the PLL circuit. A reference waveform generation circuit, an output power command generation circuit that determines the output power of the inverter, a multiplication circuit that multiplies both outputs of the reference waveform generation circuit and the output power command generation circuit to generate an output current command signal, An adder circuit that adds the output of the multiplier circuit to the output current of the high-frequency inverter that is full-wave rectified by the rectifier, and an output current control circuit that outputs an output current control signal to the high-frequency inverter based on the output of the adder circuit, And an islanding operation detection circuit for detecting a fluctuation in the system voltage in which a fluctuation in active power based on the output current control signal appears due to a grid disconnection. And butterflies.

When the present invention is applied to the low frequency insulation type, it has the following constitutional requirements.

That is, a small-capacity distributed power source consisting of a DC power source and an inverter is connected to a power system via a low-frequency isolation transformer, so that the inverter can be operated independently by a grid disconnection.
An isolated operation detection device for a distributed power supply by an active method, which detects from fluctuations in system voltage that appear due to disturbance occurrence based on active power fluctuations,

A PLL circuit for generating a phase reference signal synchronized with the system voltage, and a reference waveform for generating a reference waveform signal in which the amplitude of the AC waveform is increased or decreased by a predetermined cycle at regular intervals based on the output of the PLL circuit. A generation circuit, an output power command generation circuit that determines the output power of the inverter, a multiplication circuit that multiplies both outputs of the reference waveform generation circuit and the output power command generation circuit to generate an output current command signal, and the multiplication thereof. An adder circuit for adding the output of the circuit to the alternating current output from the inverter, an output current control circuit for outputting an output current control signal to the inverter based on the output of the adder circuit, and an effective circuit based on the output current control signal. An isolated operation detection circuit for detecting a fluctuation in the system voltage in which the power fluctuation appears due to the grid disconnection.

[0015]

In the isolated operation detecting apparatus for the distributed power source according to the present invention, the output current control based on the reference waveform signal in which the amplitude of the full-wave rectified waveform or the AC waveform is increased / decreased by a predetermined cycle at a constant interval by the reference waveform generation circuit. A signal is generated, and a fluctuation in the system voltage, which is generated by the system parallel connection and causes disturbance caused by the fluctuation in active power due to the output current control signal, is detected by the islanding operation detection circuit. This makes it possible to realize reliable islanding operation detection with a simple circuit configuration.

[0016]

EXAMPLE An example in which the present invention is applied to a small-capacity home solar power generation system will be described with reference to FIGS.

As shown in FIG. 1, this solar power generation system uses a solar cell 11 that generates direct current power by solar radiation from sunlight, and a direct current power generated by the solar cell 11 by a switching operation by a switching element 12. Therefore, a high-frequency inverter 13 for converting into a high-frequency AC voltage, a rectifier 16 coupled to the high-frequency inverter 13 via a high-frequency insulating transformer 14, and a diode 15 for converting the high-frequency AC voltage into DC power again, and the rectifier 16 are provided. Connected via the reactor 17 for the filter,
Low frequency inverter 1 for converting the DC power into an AC voltage by the switching operation of the switching element 18.
It has a distributed power source 20 composed of 9 and 9. The low frequency inverter 19 of the distributed power source 20 is connected to the electric power system 22 via the system interconnection switch 21. In the figure, 23 is a load to which electric power is supplied from the distributed power source 20 or the electric power system 22.

The isolated operation detecting apparatus for the distributed power source 20 applied to this solar power generation system includes a control unit 24 having the following circuit configuration.

The control unit 24 is detected by the transformer 25.
Phase reference signal S synchronized with the system voltage Vs₁ Generate
Based on the PLL circuit 26 and the output of the PLL circuit 26
The amplitude of the full-wave rectified waveform at regular intervals for a predetermined number of cycles
The reference waveform signal S that has been increased or decreased ₂ Reference waveform generation to generate
Determine the output power of the circuit 27 and the high frequency inverter 13.
Output power command generation circuit 28 to determine the reference waveform generation
Multiply both outputs of the circuit 27 and the output power command generation circuit 28
Output current command signal S₃ And a multiplication circuit 29 for generating
The output of the multiplication circuit 29 of is detected by the current transformer 30,
High frequency inverter full-wave rectified by the rectifier 16
Adder circuit 31 for adding to the output current of 13 and its addition times
Output current control signal S based on the output of path 31_Four The high frequency
An output current control circuit 32 for outputting to the inverter 13,
Output current control signal S_Four Active power fluctuation based on
Independent operation for detecting fluctuations in the system voltage Vs appearing in series
And a roll detection circuit 33.

Reference numeral 34 is a pulse generation circuit for driving the high frequency inverter 13 based on the output current control signal S ₄ output from the output current control circuit 32, and 35 is the P
It is a pulse generation circuit that drives the low-frequency inverter 19 based on the output of the LL circuit 26.

Further, the reference waveform generating circuit 27 specifically stores data Da to Dc for generating the reference waveform signal S _{2 in} which the amplitude of the full-wave rectified waveform is increased / decreased by a predetermined cycle at regular intervals. The three ROMs 36a to 36c and the changeover switch 37 [having contacts a, b, and c] for switching among the respective ROMs 36a to 36c are incorporated. The data Da to Dc stored in the ROMs 36a to 36c are full-wave rectified waveform data of the same phase, and the amplitudes of the data Da to Dc have the following relationship.

│Da│ = K₁× | Db | | Dc | = K₂× | Db |₁ And K₂ Is a variable constant, for example, K
₁ = 1.1, K₂ = 0.9, this K₁ And K₂ Tonohira
The average value is set to 1. Also, the switching
Operating time N of switch 37₁ And N₂ Is variable and the disturbance
Operating time N of the changeover switch 37 for generating
₂ Is, for example, 1/2 cycle, and the minimum required disturbance
And the time that can be generated. On the other hand, switch
Operating time N of switch 37₁ Is the isolated operation detection time and
Number of system voltage fluctuations N during islanding _D In the setting value of [below]
It is decided based on.

Next, the operation of detecting the isolated operation by the control unit 24 of the isolated operation detecting apparatus having the above-mentioned configuration will be described with reference to the waveform diagram of FIG.

First, the transformer 25 detects the system voltage Vs [see (a) in the figure] and outputs the phase reference signal S ₁ [see (b) in the figure] synchronized with the system voltage Vs to the PLL circuit 26.
Generate with. The phase reference signal S ₁ is output from the PLL circuit 26 to the islanding operation detection circuit 33 as a detection synchronization signal, and the reference waveform generation circuit 27 causes the PLL circuit 2 to operate.
On the basis of the phase reference signal S ₁ output from the signal generator 6, a reference waveform signal S ₂ [see (g) in the figure] is generated in which the amplitude of the full-wave rectified waveform is increased or decreased by a predetermined cycle at regular intervals.

In the reference waveform generating circuit 27, each R
Based on the data Da to Dc stored in the OMs 36a to 36c, the reference waveform signal S ₂ is generated by the switching operation of the changeover switch 37 [see FIG. That is, first, the changeover switch 37 [contact is b] is set to N.
Connected to ROM 36b for _one cycle and the data D
b [See (c) in the figure] is taken out, and then the changeover switch 37 [contact is a] for N ₂ cycles of the ROM 3
6a, take out the data Da [see (d) in the same figure], and change the switch 37 [contact c] to N.
Connected to ROM36c for ₂ cycles and the data D
c Take out [See Figure (e)]. By repeating this operation, the reference waveform generating circuit 27 outputs the reference waveform signal S ₂ (see FIG. 9 (g)) in which the amplitude of the full-wave rectified waveform is increased / decreased by a predetermined cycle at regular intervals.

On the other hand, the output power command generation circuit 28 determines the output power of the high frequency inverter 13, and the outputs of the output power command generation circuit 28 and the reference waveform generation circuit 27 are multiplied by the multiplication circuit 29 and output. A current command signal S ₃ [see (h) in the figure] is generated. Here, the output current of the high-frequency inverter 13 which is full-wave rectified by the rectifier 16 is detected by the current transformer 30, and the output current is converted into the output current command signal S ₃ output from the multiplication circuit 29 by the adder circuit 31. to add. The output current control signal S ₄ is output based on the output of the adder circuit 31.
The pulse generator 34 drives the high frequency inverter 13 based on the output current control signal S ₄ . At this time, the system current Io detected by the current transformer 38 [see (i) in the figure] flows through the system.

Here, if the system is in a normal state, the disturbance due to the active power fluctuation due to the output current control signal S ₄ is absorbed by the power system 22 and does not appear in the system voltage Vs, but the system is solved. When lined up [A in FIG. 4A], the active power fluctuation based on the output current control signal S ₄ appears as a fluctuation in the system voltage Vs [see FIG. 3A] due to the systematic unparalleling. This fluctuation of the system voltage Vs is detected by the islanding operation detection circuit 33, and its detection signal S ₅ [(j) in the same figure]
As a gate block signal.
To stop the high frequency inverter 13.

In the detection of the islanding operation, the operation of the changeover switch 37 is performed due to the constraint that the inverter 13 must be stopped when a predetermined time, for example, 0.5 to 1.0 seconds has elapsed from the occurrence of the disconnection of the system. The times N ₁ and N ₂ and the number of times of system voltage fluctuation N _D are, for example, N ₁ = 15 cycles,
It is sufficient to set N ₂ = 1 cycle and N _D = 3 times.

In the above embodiment, the reference waveform generating circuit 2
7 includes three ROMs 36a to 36c, and each ROM
Description when switching data stored Da to DC to 36a~36c selected by the switching operation of the switch 37 generates a reference waveform signal S ₂ which is increased or decreased by a predetermined cycle the amplitude of the full-wave rectified waveform at regular intervals However, in addition to this, one ROM is built in, and the ROM
It is also possible to store the reference waveform signal S _{2 in} which the amplitude of the full-wave rectified waveform is increased or decreased by a predetermined cycle at regular intervals as it is as data.

In the above, the case where the invention is applied to a solar power generation system equipped with a high frequency insulation type inverter has been described, but the present invention is not limited to this, and a solar power generation system equipped with a low frequency insulation type inverter. It can also be applied to a system, in which case the photovoltaic power generation system has a configuration in which a small-capacity distributed power source consisting of a DC power source and an inverter is connected to the power system via a low-frequency isolation transformer, and the reference waveform In the generator circuit, an output current control signal is generated based on a reference waveform signal in which the amplitude of an AC waveform (a full-wave rectified waveform in the high frequency insulation type of the above-mentioned embodiment) is increased or decreased by a predetermined cycle at regular intervals.

Further, the present invention can be applied to a solar power generation system using a solar cell as a direct current power source, and other direct current power sources include, for example, a fuel cell.

[0032]

According to the present invention, it is possible to provide a new active-system isolated-operation detecting means with a simple circuit configuration, which detects from the fluctuation of the system voltage appearing due to the disturbance occurrence based on the fluctuation of active power. One new means will be added to the detection of isolated operation, which is generally considered technically difficult, and it will be easier to realize more reliable detection of isolated operation of the inverter during grid disconnection. , Safety and reliability are greatly improved.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a control unit of a solar power generation system and an islanding operation detection device for explaining an embodiment of the present invention.

FIG. 2 is a waveform diagram showing output waveforms of each constituent circuit in FIG.

FIG. 3 is a block diagram showing a schematic configuration of a solar power generation system.

[Explanation of symbols]

11 DC Power Supply [Solar Cell] 13 High Frequency Inverter 14 High Frequency Insulation Transformer 16 Rectifier 19 Low Frequency Inverter 20 Distributed Power Source 22 Power System 26 PLL Circuit 27 Reference Waveform Generation Circuit 28 Output Power Command Generation Circuit 29 Multiplying Circuit 31 Addition Circuit 32 Output Current Control Circuit 33 Single operation detection circuit Vs System voltage S ₁ Phase reference signal S ₂ Reference waveform signal S ₃ Output current command signal S ₄ Output current control signal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H01L 31/04 H02J 3/06 9470-5G H02M 7/48 R 9181-5H M 9181-5H

Claims (2)

[Claims] 1. A small-capacity distributed power source in which a DC power source and a high-frequency inverter are coupled to a rectifier and a low-frequency inverter via a high-frequency insulation transformer is connected to a power system to enable independent operation of the inverter by a grid disconnection. A distributed power source isolated operation detection device by an active method for detecting from fluctuations of a system voltage that appears due to disturbance occurrence based on power fluctuations, wherein a PLL circuit that generates a phase reference signal in synchronization with the system voltage, and the PLL circuit A reference waveform generating circuit that generates a reference waveform signal in which the amplitude of the full-wave rectified waveform is increased or decreased by a predetermined cycle at regular intervals based on the output; an output power command generating circuit that determines the output power of the inverter; The multiplication circuit that multiplies both outputs of the reference waveform generation circuit and the output power command generation circuit to generate the output current command signal, and the output of the multiplication circuit An adder circuit that adds to the output current of the high-frequency inverter that is full-wave rectified by a rectifier, an output current control circuit that outputs an output current control signal to the high-frequency inverter based on the output of the adder circuit, and an output current control signal that is based on the output current control signal. An isolated operation detection device for a distributed power supply, comprising: an isolated operation detection circuit that detects a change in the system voltage in which active power fluctuation appears due to the grid disconnection. 2. A small-capacity distributed power source consisting of a DC power source and an inverter is connected to a power system via a low-frequency isolation transformer, and the independent operation of the inverter by the grid disconnection is realized by the disturbance occurrence based on the active power fluctuation. An isolated operation detector for a distributed power supply by an active method that detects from fluctuations in the system voltage that is output, and a PLL circuit that generates a phase reference signal that is synchronized with the system voltage, and an AC waveform based on the output of the PLL circuit. A reference waveform generation circuit that generates a reference waveform signal whose amplitude is increased or decreased by a predetermined cycle at a constant interval, an output power command generation circuit that determines the output power of the inverter, the reference waveform generation circuit, and an output power command generation circuit. A multiplying circuit for generating an output current command signal by multiplying both outputs of the above and adding the output of the multiplying circuit to the alternating current output from the inverter. An adder circuit, an output current control circuit that outputs an output current control signal to an inverter based on the output of the adder circuit, and a fluctuation of a system voltage in which active power fluctuation based on the output current control signal appears by a grid disconnection. An isolated operation detection device for a distributed power source, comprising: an isolated operation detection circuit for detecting.