JPH06153403A - System-connected power supply system - Google Patents

Abstract

PURPOSE:To supply power stably from a power converter even if the voltage of a commercial power source drops suddenly. CONSTITUTION:If the voltage of a commercial power source drops suddenly, comparators 811 and 812 and a differentiating circuit 815 detect it, and changes the PWM signal to control a power converter only by the time of a timer 16, and drops the output voltage of the power converter suddenly in proportion to the sudden decrease of the commercial power source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grid-connected power supply system for supplying commercial power supply power and AC power obtained by converting the output of a DC power generator by a power converter in parallel to an AC load. The present invention relates to a power supply system capable of avoiding a system down even when the power supply voltage is sharply reduced.

[0002]

2. Description of the Related Art In recent years, electric power obtained from a direct-current power supply device using a fuel cell, a solar cell, or the like and electric power obtained from a general commercial power supply have been spotlighted as a clean and highly efficient next-generation energy source. Power supply systems that are linked to each other and are operated actively are being studied.

In this system, it is possible to obtain the most effective electric energy when the DC generator is constantly operated at the rated output, and to realize highly efficient operation. In particular,
When a fuel cell is used in the DC power generation device, by maintaining operation at a constant rated output, it is possible to realize a highly efficient cogeneration system that can most effectively obtain electric and thermal energy.

FIG. 5 shows an example of a grid-coupling power supply system in consideration of such characteristics of a DC power generator. Reference numeral 1 is a commercial power source, 2 is a direct-current power generator including the above-described fuel cell or solar cell, 3 is a power converter such as an inverter that converts direct-current power obtained from the direct-current power generator 2 into alternating-current power, and 4 is this power This is a linking reactor for linking the output of the converter 3 with the output of the commercial power supply 1 to supply the AC load 5. Reference numeral 6 denotes a connection connection point between the output of the commercial power supply 1 and the output of the power conversion device 3. Reference numeral 7 is an overcurrent detection point 7 provided on the output side of the power conversion device 3, and when the overcurrent is detected here, the operation of the power conversion device 3 is stopped. Reference numeral 8 denotes a control circuit for controlling the power conversion device 3, which uses detection voltages at the output voltage detection point 9 of the commercial power supply 1 and the output voltage detection point 10 of the power conversion device 3 as signals for control. input.

As described above, the commercial power source 1 and the power converter 3
In the system in which the DC power generating device 2 that outputs via the power supply is used as an input power source to operate in cooperation with the load 5, a constant cut power is supplied from the DC power generating device 2 and the load fluctuation is supplied from the commercial power source 1 Is commonly used.

The reason for this is that since the load fluctuation followability of the DC generator 2 is slow, the output stability and reliability are higher when the DC generator 2 supplies constant power. Further, from the viewpoint of high efficiency operation of the fuel cell, it often takes the form of constant rated output operation.

FIG. 6 is a block diagram of a control circuit 8 for controlling the output voltage and the power factor of the power conversion device 3 to which the above-mentioned base cut power feeding method is applied. Here, a voltage obtained by rectifying the detection voltage at the output voltage detection point 9 of the commercial power supply 1 by the rectifier circuit 801 and a voltage obtained by rectifying the detection voltage at the output voltage detection point 10 of the power conversion device 3 by the rectification circuit 802 are compared. 8
The comparison is made at 03, and the difference is extracted.

Then, this difference is input to the reference sine wave amplitude commander 804 and converted into a sine wave having an amplitude corresponding to the difference, and the sine wave output of the amplitude commander 804 and the reference sine wave generator 805. A signal (sine wave signal) that is compared with the sine wave output by the comparator 806 (strictly, an additive calculation is performed) to determine the output voltage amplitude value of the power conversion device 3 (sine wave signal).
Is obtained. Further, the output voltage amplitude value signal and the phase command signal of the phase commander 807 are compared (strictly, arithmetic processing) by the comparator 808, the phase of the output voltage amplitude value signal is set, and the power factor of the load 5 is set. An output power amount value signal (a sine wave signal in which the amplitude and the phase amount are set) that gives a high power factor is determined.

The output electric energy value signal and the triangular wave signal from the carrier triangular wave generator 809 are compared by a comparator 810.
And a PWM (pulse width modulation) signal for controlling the power conversion device 3 is obtained here. Comparator 808
If the amplitude value of the output electric energy value signal output from is large, the pulse width of the PWM signal becomes large. And this P
If the pulse width of the WM signal is large, the power converter 3
The power conversion device 3 is controlled so that the output voltage of the power conversion device is high and is low when the output voltage is low.

FIG. 7 is a vector diagram of the coordinated power supply when controlled by the control circuit 8. (A) is a vector diagram when the output of the direct-current power generator 2 is maintained at a rated value and the linked operation is performed at a high power factor so that only the active power is supplied from the power converter 3.

With respect to the output voltage Va from the commercial power source 1,
By advancing the phase of the output voltage Vb of the power conversion device 3 by φ, a voltage difference Vc is generated at both ends of the linking reactor 4. By the voltage Vc of the reactor 4 for linkage,
A current Ic whose phase difference is delayed by π / 2 from the voltage Vc
Flows.

As described above, in order to set the output power factor of the power converter 3 to 1, the electric power is adjusted so that the output current Ic of the power converter 3 and the voltage Va of the commercial power supply 1 are in phase. The operation is performed by adjusting the voltage Vb and the phase φ of the converter 3. This adjustment is performed by the control circuit 8 described above.

[0013]

However, the commercial power source 1
Supplies power to other AC loads and is not always stable. Therefore, for example, when the power of another AC load suddenly increases, the voltage Va of the commercial power supply 1 is increased.
May drop sharply.

When the voltage Va sharply decreases, the voltage Vc of the linking reactor 4 rapidly increases and its current Ic rapidly increases as shown in FIG. 7B. As a result, when an overcurrent is detected at the overcurrent detection point 7, the power conversion device 3
Will make an emergency stop.

As described above, depending on how the voltage Va of the commercial power source 1 is lowered, the high power factor power feeding of the power converter 3 cannot be maintained, and the power converter is used to protect the DC power generator 2 and the power converter 3. The device 3 makes an emergency stop.

That is, the amplitude commander 804 of the control circuit 8
Needs to perform the averaging processing of the differential signal from the comparator 803 once, and also the averaging processing of the comparator 808 for comparing with the output of the phase commander 807. Therefore, it becomes impossible to follow the rapid decrease in the commercial voltage, and the power conversion device 3 must be stopped by the overcurrent detection system having a fast response. As described above, when the power is supplied to the load in cooperation with the commercial power source, the DC generator 2 is conventionally used.
There was a drawback that power could not be stably supplied from the side.

The object of the present invention is to remedy such a drawback, and when the voltage of the commercial power supply sharply decreases, the output voltage of the power converter is tracked proportionally before the overpower cutoff. Even if the voltage of the commercial power supply suddenly decreases, it is possible to maintain high-efficiency operation.
An object of the present invention is to provide a grid-coupling power supply system capable of stably supplying power from a power conversion device.

[0018]

To this end, the present invention is obtained from a commercial power supply while converting the output of a DC power generator into AC power by a power converter and supplying it to an AC load via a linking reactor. Supply power to the AC load,
An output voltage amplitude value signal corresponding to the difference between the output voltage of the power converter and the voltage of the commercial power supply is obtained, and an output power amount value signal obtained by shifting the output voltage amplitude value signal by a predetermined phase is obtained, and the output power is obtained. In the grid-coupling power supply system that controls the output voltage of the power conversion device by the quantity value signal, a differentiation circuit that detects a sudden decrease in the voltage of the commercial power source is provided, and the differentiation pulse obtained from the differentiation circuit causes the differentiation pulse to be output for a predetermined time. The level of the output electric energy value signal is changed to decrease the output voltage of the power conversion device for the predetermined time.

[0019]

According to the present invention, even if the commercial power supply voltage suddenly decreases, the output voltage of the power converter instantaneously decreases in proportion to the change of the commercial voltage, so that the operation is performed without stopping due to overcurrent. Is maintained and the power factor is also maintained at a high power factor.

[0020]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a block diagram of a control circuit 80 of the system-linked power supply system of the embodiment. That is, in this embodiment, the control circuit 80 is used in place of the control circuit 8 shown in FIGS. In this control circuit 80, the same parts as those in the conventional control circuit 8 are designated by the same reference numerals.

Reference numeral 811 denotes a rectifier circuit for rectifying the detection voltage at the output voltage detection point 9 of the commercial power source 1, and 812 denotes the power conversion device 3.
Rectifier circuit that rectifies the detection voltage at the output voltage detection point 10 of
Reference numeral 813 is a comparator for comparing the rectified outputs of both rectifier circuits 811 and 812. Further, 814 is a filter for removing the ripple component included in the comparison output, 815 is a differentiating circuit for differentiating the output of the filter 814, 816 is activated when a differential pulse output from the differentiating circuit 815 is input, and is started for a predetermined time. A timer that outputs a voltage of a predetermined level, 8
A comparator 17 compares the output voltage of the timer 816 with the voltage of the output electric energy value signal (sine wave signal) output from the comparator 808, and sends the signal of the comparison result to the comparator 810 for PWM signal formation. Is.

In the control circuit 80, the commercial power supply voltage detection point 9 is provided on the output side of the comparator 808 as in the conventional case.
With the amplitude value corresponding to the difference between the voltage Va and the voltage Vb at the output voltage detection point 10 of the power conversion device 3, the output power amount value signal of the phase amount set by the phase commander 807 is obtained. For example, if the difference is large, the level of the output electric energy value signal becomes large.

On the other hand, when the difference between the voltages Va and Vb is large, the difference obtained by the comparator 813 also becomes large. Then, this difference is subjected to ripple removal in the filter 814 (this prevents the malfunction of the differentiating circuit 815).
Although it is input to the differentiating circuit 815, if there is no large change in the difference, the large differentiating pulse is not output from the differentiating circuit 815 and the timer 816 is not started. Therefore, the comparator 817 allows the output power amount value signal input from the comparator 808 to pass through to the output side as it is, and the comparator 810
Then, the control operation similar to the conventional one is performed.

However, when a new load is connected to the load connected to the commercial power source 1 and a sudden load increase occurs, the voltage Va of the commercial power source 1 sharply decreases. As a result, the differential voltage obtained by the comparator 813 rapidly increases, and the differentiating circuit 815 generates a large-differential pulse. Therefore, as shown in FIG. 2, the timer 816 is activated and the timer time (time until the control circuit 80 can perform follow-up control, generally 200 to 40).
0 ms), the predetermined voltage is output from the timer 816 to the comparator 81.
7 is applied as a comparison reference value.

Therefore, the output power value signal 808a (see FIG. 3) output from the comparator 808 is output to the timer 81.
The output signal of 6 is output by the comparator 817 as the signal 817.
P obtained by the comparator 810 by leveling down like a
The pulse width of the WM signal changes from a large value as shown in FIG. 3B to a small value as shown in FIG. Therefore, the output voltage Vb of the power conversion device 3 decreases.

FIG. 4 is a diagram showing a vector change due to a change in the commercial voltage Va during that time. When the voltage Va of the commercial power source 1 suddenly decreases from the steady state shown in (a), the electric power is changed as shown in (b). The output voltage Vb of the converter 3 is the control circuit 80.
The power factor is maintained instantaneously by being controlled by, and the power factor is maintained, and the current Ic is prevented from rapidly increasing.

As a result, even if the commercial power supply voltage Va sharply decreases, the vector state becomes as shown in FIG. 5B for a very short time and the current Ic increases, but the overcurrent detection operation is performed. Previously, the vector state changed to the state shown in FIG. 4B, and the current Ic suddenly decreased suddenly. Therefore, the power conversion device 3 does not stop due to overcurrent, and it is possible to continue the power supply while efficiently using the electric energy from the DC power generation device 2.

[0028]

As described above, according to the present invention, when the output from the DC power generator is converted into AC power by the power converter and the output of the commercial power source are linked to supply to the AC load, Even if the power supply voltage suddenly decreases, the output voltage of the power conversion device instantaneously decreases in proportion to the change in the commercial voltage, and the power conversion device can continue high-efficiency operation.

Therefore, even when the commercial power supply voltage drops sharply, the power converter does not stop due to overcurrent, and the DC generator can supply power to the AC load at a stable output all the time, thus constructing a highly reliable power supply system. The feature is that the energy obtained from the DC generator can be effectively used.

[Brief description of drawings]

FIG. 1 is a block diagram of a control circuit of an embodiment of a system-linked power supply system of the present invention.

FIG. 2 is an explanatory diagram of the operation of a timer of the control circuit.

FIG. 3 is an explanatory diagram of PWM signal generation of the control circuit.

FIG. 4 is a voltage / current vector diagram in a normal state (a) and an abnormal state (b) of the system-linked power supply system of the present invention.

FIG. 5 is a block diagram of a general grid-linked power supply system.

FIG. 6 is a block diagram of a conventional control circuit.

FIG. 7 is a voltage / current vector diagram of a conventional system-linked power supply system at a normal time (a) and at an abnormal time (b).

[Explanation of symbols]

1: Commercial power source, 2: DC power generator, 3: Power converter,
4: Reactor for linkage, 5: AC load, 6: Connection connection point, 7: Overcurrent detection point, 8, 80: Control circuit, 9: Commercial power supply voltage detection point, 10: Power converter output voltage detection point,
801, 802: rectifier circuit, 803: comparator, 804:
Reference control sine wave width command device, 805: Reference sine wave generator, 8
06: comparator, 807: phase commander, 808: comparator,
809: Carrier triangular wave generator, 810: Comparator, 81
1, 812: rectifying circuit, 813: comparator, 814: filter, 815: differentiating circuit, 816: timer, 817: comparator.

Claims (1)

[Claims] 1. A power converter converts the output of a DC power generator into AC power and supplies the AC power to an AC load via a linking reactor, while supplying power obtained from a commercial power source to the AC load to supply the power. An output voltage amplitude value signal corresponding to the difference between the output voltage of the converter and the commercial power supply voltage is obtained, an output power amount value signal obtained by shifting the output voltage amplitude value signal by a predetermined phase is obtained, and the output power amount value is obtained. In a grid-coupling power supply system that controls the output voltage of the power converter by a signal, a differentiation circuit that detects a sudden decrease in the voltage of the commercial power supply is provided,
A differential pulse obtained from the differentiating circuit changes the level of the output electric energy value signal for a predetermined time so as to reduce the output voltage of the power conversion device for the predetermined time. Power supply system.