JP3142029B2 - Reverse charge detection circuit in distributed power supply equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reverse charge detection circuit for detecting a reverse charge state such as a power failure in a distributed power supply system in which a plurality of power supplies such as a solar power supply and a fuel cell power supply are distributed. About.

[0002]

2. Description of the Related Art FIG. 3 is a schematic view showing a distributed power supply system of this type, wherein 1 is a solar cell, 2 is an inverter, 3 is a contactor (contactor), 4 is a circuit breaker, 5 is a power system,
Reference numeral 6 denotes a general load, and Vs denotes a grid connection point voltage (detection value). That is, during the interconnection of the distributed arrangement type power supply, the circuit breaker 4
Is normally open (power failure state), the distributed power supply usually monitors the voltage Vs at the system interconnection point, and disconnects the power supply from the power supply system due to a voltage (V) abnormality or a frequency (F) abnormality.

[0003] However, when the generated power of the distributed power source and its load are matched, that is, when the power flow with the power system is very small, even if the system-side switch is opened, the distributed power source is opened. Maintains the operation based on the voltage output by itself and the output voltage of the distributed power source that is connected to the other at the interconnection point. At this time, the amplitude and frequency of the interconnection point voltage hardly fluctuate, and the system abnormality cannot be detected. Therefore, the power is continuously supplied to the load, and the voltage generated by the distributed power supply continues to be generated on the distributed power supply side of the circuit breaker. become. This is called a reverse charging state, and there is a risk that an unexpected situation such as an electric shock may be caused to the security and maintenance of the power system. As a method of detecting such a reverse charging state and quickly disconnecting the distributed power supply from the system, the following method has been proposed.

Before describing the conventional method, its control principle will be described. FIG. 4 shows the equivalent circuit of FIG.
FIG. 4 shows a current vector diagram. This is an example using a voltage-controlled inverter, 2 is an inverter (INV), 5 is a power system, 7 is a reactor (X), Vx is its terminal voltage, and Vi is
Denotes an inverter output voltage detection value, and Vs denotes a system interconnection point voltage detection value. As shown in FIG. 4, the inverter 2 sets the leading phase voltage V with respect to the grid connection point voltage Vs.
By outputting i, active power is supplied to the system side, and reactive power is adjusted by controlling amplitude. FIG. 4B shows a vector diagram when the power factor is 1. The voltage controlled inverter controls the output voltage waveform, and the output power control controls the output voltage phase,
This is performed by controlling the amplitude command. Note that the output voltage is always a sine wave.

FIG. 5 is a block diagram showing a control circuit of the voltage control type inverter. That is, the output of the voltage regulator (AVR) 9 that operates so that the operating voltage (detection value) Ed of the solar cell 1 matches the set value Ed ^* is given to the power regulator 10 as an output power command P ^*. Can be The power controller 10 determines that the output power P of the inverter 2 is equal to its command value and P
It operates so as to be equal to ^*, and outputs the phase difference command θ ^* of the inverter output voltage. The phase comparator (COM) 17 outputs θ, which is the result of comparison between the system voltage Vs and the reference sine wave voltage command of the inverter, and the phase adjuster 11 sets the value θ to be equal to the phase difference command θ ^*. It operates to generate a frequency command f ^* of the inverter voltage.

The frequency command f ^* is expressed by a voltage / frequency (V /
F) Converter 12, up / down counter (U / D) 1
3. A reference sine wave voltage command is provided by an input / output interface (I / O) 14, a ROM 15 for storing a sine wave signal, a digital / analog converter (D / A) 16, and the like. This command value is multiplied by a voltage amplitude command obtained as a result of the reactive power control by the voltage amplitude adjustment circuit 22 in the multiplier 18 to obtain an inverter output voltage command V
i ^* can be obtained. Then, this voltage command Vi ^*
Is input to the comparator 20 together with the carrier from the carrier generator 19, and the two are compared. The output from the comparator 20 is a gate signal generation circuit (PG) 2
1 to form a firing signal G for the switching element of the inverter. By firing or extinguishing each switching element of the inverter 2 with the firing signal G, the phase and amplitude of the sine wave output voltage can be controlled, and active power can be supplied to the system.

Next, a reverse charge detection method will be described.
Now, when a minute vibration of an appropriate cycle is given to the active power command of the inverter, the inverter controls the output power by changing the output voltage phase. The phase difference is an integral amount of the frequency change, and the phase change appears as a frequency change of the inverter output voltage. During interconnection with the grid, the inverter can easily output active power fluctuations because the power system absorbs all fluctuations in active power, and as a result, frequency fluctuations caused by the active power fluctuation command of the output voltage are temporary. It becomes something. Further, the power fluctuation hardly affects the power system, and the frequency fluctuation does not appear in the interconnection point voltage Vs.

However, after the system is cut off, the inverter output power can supply only a constant power determined by the load constant. Therefore, the inverter cannot output the active power variation ΔP corresponding to the active power variation command ΔP ^* ,
Further, the frequency is greatly changed. Since this frequency fluctuation occurs as a frequency fluctuation in the same cycle as the power fluctuation command ΔP ^* , the reverse charging state can be determined by detecting the amount of this frequency fluctuation accurately. FIG. 5 shows an embodiment based on such a viewpoint. Here, an active power fluctuation command generating unit that generates an active power fluctuation command ΔP ^* , and a frequency fluctuation component having the same cycle as the fluctuation command are detected. And a frequency fluctuation detecting unit for determining a reverse charging state.

That is, the former active power fluctuation command generation unit includes an oscillator (OSC) 23, a frequency divider 24, and an amplifier 25.
The clock signal generated from the OSC 23 is frequency-divided into a command cycle, and an active power fluctuation command ΔP ^* having an appropriate amplitude is generated via the amplifier 25. Then, the active power of the inverter is periodically changed by adding this signal to the active power command P ^* of the inverter. In the frequency fluctuation detecting unit, the system interconnection point voltage Vs is input to the frequency / voltage (F / V) converter 26, where it is converted into a voltage signal of a predetermined level. From this signal, the frequency component of the commercial cycle (DC component and ripple component during F / V conversion)
Is removed by a commercial frequency removing filter 27 composed of a DC filter, a notch filter, and the like, and a fluctuating frequency component is detected by a bandpass filter 28 that detects only a frequency fluctuating component having the same cycle as the active power fluctuation command. Then, the determination circuit 29 determines that the fluctuation amount has reached a predetermined level.
Is determined to be in the reverse charging state, a signal S for stopping the ignition of the inverter and opening the interconnection contactor 3 is generated.

Next, a case where a current control type inverter is used will be described. The current control type inverter controls its output current to be a sine wave current having the same phase as the system voltage. Regarding the active power control, the voltage control type controls the output voltage phase, whereas the current control type controls the current amplitude. FIG. 6 is a block diagram showing a control circuit of the current control type inverter. A voltage regulator (AVR) 9 that operates so that the operating voltage (detected value) Ed of the solar cell 1 matches the set value Ed ^* outputs an output power command P ^* . The command P ^* is an amplitude command of the output current command, which is a current command reference sine wave i _unit synchronized with the system voltage determined by the PLL circuit 31 in the multiplier 32.
And the output current command i ^{* of} the inverter.

The output current controller 33 operates to make the inverter output current detection value i equal to the command value i ^*, and the output thereof becomes the inverter output voltage command Vi ^* .
The voltage command Vi ^* is input to the comparator 20 together with the carrier from the carrier generator 19, and the two are compared. The output from the comparator 20 is distributed and shaped by a gate signal generation circuit (PG) 21 to become a firing signal G for the switching element of the inverter. By firing or extinguishing each switching element of the inverter 2 with the firing signal G, the amplitude of the output current is controlled. This is the control operation principle of the current control type inverter.

As described above, both the voltage control type and the current control type have a stable opposing voltage of the power system during the system interconnection.
The active power is controlled by changing the phase of the output voltage with respect to the opposing voltage. That is, a change in the active power command in the voltage-controlled inverter directly acts as a phase control operation of the output voltage. The interconnection point voltage after system interruption is the voltage output by the inverter,
Here, the inverter performs a control operation to change the voltage phase,
That is, a frequency variation occurs. Therefore,
By detecting this frequency variation, it is possible to determine reverse charging.

On the other hand, a change in the active power command in the current control type inverter affects the amplitude of the current command, and the output voltage changes by the PI adjustment operation of the current regulator in response to the change in the current command amplitude. Therefore, after the system is cut off, the current control type inverter changes the amplitude of the output current in phase with the interconnection point voltage generated by the inverter itself. Therefore, the active power can output a variation ΔP according to the command value. Therefore, no frequency fluctuation accompanying the power fluctuation command appears, and it is difficult to detect reverse charging even if a frequency fluctuation detection circuit including the F / V 26, the commercial frequency elimination filter 27, the bandpass filter 28, and the determination circuit 29 is provided. That is to say.

[0014]

As described in detail above, when the reverse charging detection method as described with reference to FIG. 5 is applied to a system using a current control type inverter, the frequency of the interconnection point voltage due to the fluctuation of the active power command is changed. Since no fluctuation occurs, there is a problem that it is difficult to detect reverse charging. Therefore, an object of the present invention is to make it possible to detect reverse charging by detecting a frequency variation even in a device using a current control type inverter.

[0015]

According to the present invention, a plurality of distributed power supplies including a solar power supply and a fuel cell power supply, and a plurality of distributed power supplies including a solar power supply and a fuel cell power supply. And a current control type power converter that controls the output current command value so as to apply a phase change to the output current command value at a constant cycle in a distributed arrangement type power supply apparatus operated in connection with the power system. Means for detecting a frequency fluctuation component by removing a commercial frequency component from an interconnection point voltage; and applying the phase fluctuation to the frequency fluctuation component.
Judge whether the period is the same as the phase fluctuation given by the means
Determining means for determining the reverse charging state based on the output from the determining means.

[0016]

By adding the current phase change command to the phase command value of the current phase adjusting circuit, the output current phase command of the inverter is minutely changed at a constant cycle. During interconnection, the phase of the output current with respect to the system voltage fluctuates at regular intervals, but the fluctuation of the inverter output voltage with this change has little effect on the power system, and this effect appears on the interconnection point voltage. Absent. Further, since the phase of the current command changes after the system is cut off, the output voltage phase change operation, that is, the frequency fluctuation appears at the interconnection point in synchronization with the fluctuation of the current command by the above-described control operation. Therefore, by detecting this frequency variation, it is possible to accurately detect reverse charging.

[0017]

FIG. 1 is a block diagram showing an embodiment of the present invention. As can be seen from the figure, this embodiment is characterized in that the current command is given a periodic variation, and the frequency variation detection circuit and the like are the same as the conventional one. For this reason,
The configuration of the output current phase adjustment circuit 30 in FIG.
As shown in FIG. That is, the output from the oscillator 23 is converted by the frequency divider 24 and the amplifier 25 into a minute fluctuation signal Δφ having a constant period. Then, this signal is given to the output current phase adjusting circuit 30 as a phase change command. As shown in FIG. 2, the output current phase adjustment circuit 30 detects the phase difference between the output current reference value i _unit and the system voltage Vs by using the phase difference detection circuit 3.
4, and the phase difference is used as a frequency variation command signal Δf of an output current reference value for adjusting only the frequency variation of the reference signal by a phase adjuster 35 for controlling the phase difference to be equal to the phase variation command Δφ. .

The commercial frequency signal f is added to the frequency variation command signal Δf, and the frequency command f ^* of the output current reference sine wave is added ^.
And This command value is obtained by the V / F 12 using the frequency command f.
^The clock signal will be in accordance with ^* . This clock signal is U
/ D13, I / O14, sine wave ROM 15, and D / A
Although the _unit becomes a sine wave i _unit by 16 or the like, since the frequency fluctuation command is added, the i _unit becomes a sine wave signal whose phase has fluctuated with respect to the interconnection point voltage. The current amplitude command output from the i _unit and the DC voltage controller 9 is
Multiplied by the output current command i ^{* of the} inverter
Becomes

The output current of the inverter fluctuates during system interconnection, but there is almost no effect on the power system, and the voltage frequency at the interconnection point is stable. On the other hand, after the system is cut off, the interconnection point voltage becomes the voltage generated by itself,
The phase difference between the interconnection point voltage and the output current has a fixed relationship determined by the load. Inverter to output <br/> Erareru current given by the current phase change command, changing the frequency of the output voltage. However, since the phase relationship between the interconnection point voltage and the actual output current is fixed, a commanded current phase cannot be generated, and the inverter further greatly changes the frequency of the output voltage. For this reason, as in the case where the active power command is changed by the voltage-controlled inverter, the F / V2
6. This frequency fluctuation can be detected by the frequency fluctuation detecting circuit including the commercial frequency removing filter 27, the band-pass filter 28, and the determining circuit 29, and the state of reverse charging can be determined.

[0020]

According to the present invention, an output current command phase changing circuit is added to periodically change the output current phase of the inverter. Therefore, there is an advantage that it is possible to accurately detect the frequency fluctuation of the same cycle as that of the above, and to detect the reverse charging state.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a specific example of the output current phase adjustment circuit of FIG. 1;

FIG. 3 is a schematic diagram showing a general distributed arrangement type power supply system.

FIG. 4 is an explanatory diagram for explaining an equivalent circuit of FIG. 3 and voltage and current vectors.

FIG. 5 is a configuration diagram showing a conventional example of a control circuit using a voltage control type inverter.

FIG. 6 is a configuration showing a conventional example of a control circuit using a current control type inverter.

[Explanation of symbols]

1. Solar cell, 2. Inverter, 3. Contactor, 4.
Circuit breaker, 5: Electric power system, 6: General load, 7: Reactor, 8: Current transformer (CT), 9: Voltage regulator (AVR),
10: power regulator, 11: phase regulator, 12: voltage / frequency converter (V / F), 13: up / down counter (U / D), 14: input / output interface (I / O),
15 ROM, 16 Digital / analog converter (D
/ A), 17: phase comparator, 18, 32: multiplier, 19
... Carrier generator, 20 ... Comparator, 21 ... Gate signal generation circuit, 22 ... Voltage amplitude adjustment circuit, 23 ... Oscillator (OSC), 24 ... Divider, 25 ... Amplifier, 26 ... Frequency / voltage converter (F / V), 27: commercial frequency rejection filter, 28: band-pass filter, 29: discrimination circuit, 3
0: output current phase adjusting circuit, 31: PLL circuit, 33:
Current adjuster, 34: phase difference detector, 35: phase adjuster.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-71428 (JP, A) JP-A-3-256534 (JP, A) JP-A-3-78440 (JP, A) JP-A-4- 229024 (JP, A) JP-A-63-237327 (JP, A) Patent 2672712 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02J 3/38

Claims (1)

(57) [Claims] 1. A power supply comprising: a plurality of distributed power supplies including a solar power supply and a fuel cell power supply; and a current control type power converter for controlling an output current of the power supplies to a desired value. In a distributed-type power supply system that is connected to a power system, a phase fluctuation applying means for applying a phase fluctuation at a fixed cycle to the output current command value, and a commercial frequency component from the interconnection point voltage.
Detecting means for removing frequency components and detecting frequency fluctuation components ,
The frequency variation component is the phase variation given by the phase variation applying means.
And a determination means for determining whether the cycle is the same as the
A reverse charge detection circuit in a distributed arrangement type power supply, wherein a reverse charge state is determined based on an output from the determination means.