JPS62210893A - Power converter - Google Patents

Abstract

PURPOSE:To complete the switching of a power source in a specified time without supplying excessive current flow, by arranging a frequency correction circuit and a phase coincidence detecting circuit, and by switching the power source after phases coincide with each other in switching the power source. CONSTITUTION:By a 49Hz detecting circuit 17, it is detected that there is specified difference between the frequency of the output AC of a power converter 2 and the frequency of an AC power source. From a frequency correction circuit 16, the output of frequency correction signal is generated so that the phase of the output AC of the power converter 2 may be made to coincide with the phase of an AC power source 1 during the working of a frequency reference fixing circuit 19 keeping the output frequency of the power converter 2 constant. By a phase coincidence detecting circuit 15, it is detected that the phase and frequency of the output AC of the power converter 2, and the phase and frequency of the AC power source 1 are set in a specified range, and a switch 42 is turned ON, and a switch 41 is turned OFF, and the switching of the power source is completed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is a variable frequency power converter and an AC power supply that is independent of the variable frequency and wave number power converter. The present invention relates to a variable frequency power conversion device with an improved operating method used when switching between two power sources in an AC load. .

(Prior Art) The configuration shown in FIG. 4 shows a case where a switching device 4 switches between a variable frequency power converter 2 and an AC power source 1 independent of this power converter as a power source for an AC load 3. It is a diagram. In the conventional example shown in the figure, although the sequence is not shown, the AC load 3 is once disconnected from the power converter 2 and then switched to the AC power source 1 after a predetermined period of time. However, this method has problems with overcurrent flowing through the AC load 3 and sudden load fluctuations during switching. Another method is to match the output phase of the power converter 2 with the power phase of the AC power source 1 to switch the power source.

As shown in FIG. 5, this conventional example includes a variable frequency power converter 2 and an AC power supply 1 independent of the power converter 2.
In the AC load 3 having ``the power converter 2
and a first switch 4 provided between the AC load 3 and the AC load 3.
1. Consists of a second switch 42 provided between the AC power supply 1 and the AC load 3. Only the frequency control of the power conversion device 2 is shown in FIG. 4, but it generally includes a speed setter 11, an input limiting circuit 12 that sets acceleration/deceleration time, an oscillator 13 that converts a frequency reference into a pulse signal,
A frequency dividing circuit 14 that divides the output signal of the oscillator 13 into 1/6, for example, and a phase that detects that the output AC phase of the power conversion device 2 and the phase of the commercial power supply 12 are a predetermined phase difference. It is composed of several output circuits 15 and a phase detection circuit 18 that detects the phase of the AC power supply 1.

In this configuration, when switching from the power converter 2 to the AC power source 1, the speed setter 11 is set to the AC power frequency, and the power converter 2 is accelerated or decelerated to the AC power frequency as determined by the input limiting circuit 12. Accelerates with time. After accelerating to the AC power frequency, the phase detection circuit 1
The frequency reference is delicately increased or decreased by the frequency correction circuit 16 so that the phase of the AC power source 1 detected by the AC power converter 8 and the output AC phase of the power converter 2 fall within a predetermined phase difference.

The output AC phase of the power conversion device 2 is combined with the phase of the AC power source 1 by the output signal of the frequency correction circuit 16, and the phase-number configuration circuit 15 confirms that the phase difference is within a predetermined value. A power supply switching signal is output to the second switch 42. The second switch 42 is turned on by this power supply switching signal, and a parallel running period occurs in which the power converter 2 and the AC power supply 1 are connected in parallel, and the answer back of the second switch 42 turns on the first switch 41. It is opened and power switching is completed.

(Problems to be Solved by the Invention) The above-mentioned power supply switching has the same drawbacks.

(2) Stable power supply switching was not possible since it took time from when the output phase of the variable frequency power converter 2 and the AC power supply phase were synchronized until the first switch 41 or the second switch 42 was turned on. In order to switch within a fixed time, it is necessary to turn on the power with a certain phase difference, and an excessive current flows through the AC load 3 and the power converter 2.

■If the AC power frequency is fo, the output frequency of the power converter is fl, and the difference between the AC power frequency and the output frequency of the power converter is fc, then the relationship is fc=f--fl...■ .

In this case, the maximum time T for detecting that the phase with the AC power supply frequency has become in-phase can be determined from the relationship T = 1/f c . As can be seen from Equation 0, the smaller the difference fc between the two power supply frequencies, the longer the phase-number output time. Therefore, in conventional power converters, the output frequency of the power converter is increased to the AC power supply frequency, and then the frequency is slightly changed to detect phase matching, so the difference fc between the two frequencies becomes minimal, and the phase -
It took a very long time to produce several pieces.

Therefore, an object of the present invention is to provide a power conversion device with improved reliability that can complete the switching within a predetermined time without passing an excessive current to the AC load etc. when switching between two independent AC power sources. There is a particular thing.

[Structure of the invention]

(Means for Solving the Problems) The above object of the invention is achieved by a power conversion device having the following configuration.

Power conversion device that generates variable frequency alternating current as an output 2. An AC power source 1 independent of the power converter, an AC load 3 driven by the power converter 2 or the AC power source 1, and a first AC power source provided between the power converter 2 and the AC load 3. In a system in which a main circuit section is configured by a switch (41) and a second switch (42) provided between the AC power source 1 and the AC load 3, the power conversion device 2 serves as a power source for the AC load 3. from the AC power source 1
8. In order to switch to the opposite direction, a first means (phase detection circuit 18) for detecting the phase of the AC power source 1 has a predetermined value for at least the frequency of the output AC of the power converter 2 with respect to at least the frequency of the AC power source 1. a second means for detecting that there is a difference by the value (49Hz detection circuit 17); and a third means (for frequency reference Fixed circuit 19) Fourth means (frequency correction circuit) for outputting a frequency correction signal so as to match the phase of the output AC of the power converter 2 with the phase of the AC power supply 1 while the frequency reference fixed circuit 19 is in operation. 16) During operation, this frequency correction circuit 16 detects that the output AC phase of the power converter 2 and the phase of the AC power source 1 match within a predetermined phase difference, and adjusts the output from the power converter 2 to the AC power source 1. The present invention is characterized in that it includes a fifth means (phase/number configuration circuit 15) for instructing switching of the power supply to or vice versa. What is the 49Hz detection circuit?

For example, if the AC power source is 50Hz, the predetermined frequency difference is IH
z, it becomes 49Hz, and this value is especially 49Hz.
It is clear that there is no reason why it has to be 9Hz.

(Function) The present invention detects by the 49Hz detection circuit 17 that at least the frequency of the output AC of the power converter 2 differs from at least the frequency of the AC power source 1 by a predetermined value, and a frequency reference fixing circuit 19 that keeps the output frequency constant; a frequency correction circuit 16 that outputs a frequency correction signal so that the phase of the output AC of the power converter 2 matches the phase of the AC power source 1 while this circuit is in operation; A phase-number configuration circuit 15 detects that the phase and frequency of the output AC of the power converter 2 and the phase and frequency of the AC power source 1 are within predetermined values based on the output signal of the frequency correction circuit 16; The power conversion device 2 characterized by having the following can realize stable and reliable power supply switching within a predetermined time.

(Example) An embodiment of the invention will be described with reference to FIG.

A power converter 2 that generates a variable frequency, an AC power source 1 independent of the power converter 2, an AC load 3 driven by the power converter 2 or the AC power source, and a power converter 2 and the AC power source. It consists of a first switch 41 provided between the load 3 and a second switch 42 provided between the AC power source 1 and the AC load 3. The control circuit also includes a speed setter 11 that provides a speed reference to the power converter 2, and an input limiting circuit 12 that provides a constant slope to the speed reference provided by the speed setting device 11, and an output signal of the input limiting circuit 12. an oscillator 13 that converts into a pulse signal;
A frequency divider circuit 14 divides the output of the oscillator 13 into, for example, 176, and a phase-number circuit detects that the output AC phase of the power converter 2 and the phase of the AC power supply 1 are within a predetermined phase difference. an output circuit 15, a phase detection circuit 18 for detecting the phase of the AC power supply 1, and a 49Hz detection circuit for detecting that the frequency of the output AC of the power converter 2 differs from the frequency of the AC power supply 1 by a predetermined value. Circuit 17. A frequency reference fixing circuit 19 instructs to maintain the output signal level of the input limiting circuit 12 according to the detection signal of the frequency difference detection circuit 17, and a phase of the output AC of the power converter 2 while the frequency reference fixing circuit 19 is in operation. and a frequency correction circuit 16 that outputs a frequency correction signal so that the frequency matches the phase and frequency of the AC power source 1.

The 49Hz detection circuit 17 detects that the frequency of the output AC of the power converter 2 differs from the frequency of the AC power source by a predetermined value, and then frequency-corrects the output phase of the power converter 2 and the phase of the AC power source 1. Compare by circuit 16,
A frequency correction signal corresponding to the phase difference is output. Further, the output signal of the 491 (z detection circuit 17) is input to the frequency reference fixing circuit 19, and the output signal level of the input limiting circuit 12 is fixed by this frequency reference fixing circuit 19. Frequency correction circuit 16
The oscillator 13 adds the frequency correction signal which is the output signal of
Enter.

The frequency correction circuit 16 first uses the detection signal of the 49Hz detection circuit 17 to confirm that the phase of the primary AC power source 1 and the output AC phase of the power conversion device 2 have a predetermined phase difference during this 49Hz operation. , and then compares this phase difference instantaneously and outputs a frequency correction signal so as to minimize the difference. In this way, the frequency correction circuit 16 corrects the output frequency of the power converter 2 based on the instantaneous phase difference. As a result, the frequency correction circuit at each point in time becomes a so-called proportional-integral system, so that a difference appears in its response due to the initial phase difference. Therefore, if correction is started with the best phase difference, switching can be performed in a short time. Figure 2 shows frequency correction circuit 1.
6 shows the detailed circuit of No. 6. Phase difference detector 161 and correction signal output device 162. The input resistance R of this correction signal generator 162
1, a feedback proportional resistor R2, and an integrating capacitor C. The output AC waveform el of the power converter 2 and the AC power waveform ec of the AC power source 1 are input as input signals to the frequency correction circuit 16, and the phase difference detector 161 calculates the phase of the AC power waveform ec and the output AC waveform ei. In comparison, if the output AC waveform e1 has a delayed phase with respect to the AC power waveform e0, the output frequency of the power converter 2 is increased, and the output AC waveform e with respect to the AC power waveform ee.
When 1 is a leading phase, a phase correction amount e1 is outputted in a direction to decrease the output frequency of the power converter 2 according to the amount of phase difference at that time. In response to this phase correction amount e, the response of the correction signal output device 162 configured as a proportional-integral system differs depending on the phase correction amount e1. Therefore, if correction is started with the best phase difference, switching between the power conversion device 2 and the AC power supply 1 can be performed in a short time. Furthermore, when the frequency of the output AC of the power converter 2 reaches the frequency of the AC power source 1 as a result of the above-mentioned control, the phase of the output AC of the power converter 2 and the phase of the AC power source 1 match. become. At this time, the phase coincidence is detected by the phase coincidence detection circuit 15,
This detection signal closes the switch 42 provided between the AC power supply 1 and the AC load 3, and the AC power supply 1 and the power converter 2 are connected in parallel. A switch 41 provided in between is opened to complete the power supply switching.

A second embodiment of the invention will be described using FIG. 3. The difference in this figure from FIG. 1 is that the 49Hz detection circuit 17
The point is that a phase difference detection circuit 21 is provided in the middle of receiving the detection signal and operating the frequency correction circuit 16.

The phase difference detection circuit 21 detects that the phase of the AC output of the power conversion device 2 has become a predetermined phase with respect to the AC power supply 1, and generates a signal for operating the frequency correction circuit 16.

In this way, the frequency correction circuit 1 starts from a place with a predetermined phase.
6 is operated, this means that, for example, in the case of a correction circuit that amplifies and outputs an error, its initial value is always determined to be a constant value, and the frequency correction signal output from the frequency correction circuit 16 is the most vibrating. Moreover, it is possible to imagine a path that follows the target phase in the shortest possible time.

Therefore, the effect of the embodiment shown in FIG. 1 can be further emphasized.

Although the above embodiment has been described with the 1-phase coincidence detection circuit 15 provided, the target phase can be added after a predetermined period of time after the frequency correction circuit 16 operates. It is also clear that effective circuits can be realized.

〔Effect of the invention〕

As described above, in the power converter according to the present invention, the power converter can switch between the AC power source and the independent AC power supply in a short time, and can perform stable switching without flowing excessive current to the AC load and the power converter. is realized. This makes it possible to switch between the power converter and the AC power source even in a load such as a boiler where fluctuations in air volume have a large effect on the machine, allowing the power converter to be used most effectively. Therefore, it is possible to provide a power conversion device that can be used in an energy-saving variable speed drive system with improved reliability and excellent economic efficiency.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a detailed diagram of the frequency correction circuit of FIG. 1, FIG. 3 is a block diagram showing another embodiment of the present invention, and FIG. A system diagram using a power conversion device to which the present invention is applied, FIG. 5 is a block diagram showing a conventional example. 1... AC power supply, 2... Power conversion device. 3...AC load, 4...Switching device. 11... Speed setting device, 12... Input limiting circuit. 13... Oscillator, 14... Frequency dividing circuit. 15... Phase-number configuration circuit, 16... Frequency correction circuit. 17...49Hz detection circuit, 18...phase detection circuit. 19... Frequency fixed circuit, 20... Pulse amplifier circuit. 21... Phase difference detection circuit, 161... Phase difference detector. 162...Correction signal output device. Agent Patent Attorney Noriyuki Chika Yudo Hirofumi Mitsumata Figure 2

Claims (1)

[Claims] A power conversion device that generates alternating current with a variable frequency as an output, an AC power source independent of the power conversion device, an AC load driven by the power conversion device or the AC power source, and a connection between the power conversion device and the AC load. In a configuration including at least a first switch provided between the AC power source and the AC load, the AC power source is connected to the AC power source from the power converter as a power source for the AC load, or vice versa. a first means for detecting the phase of the AC power supply and a frequency reference of the power converter,
a second means for detecting that there is a predetermined frequency difference with respect to the frequency of the AC power source; a third means for instructing the power converter to maintain a frequency standard according to a detection signal of the second means; a fourth means for outputting a frequency correction signal so as to match the phase of the output AC of the power converter with the phase of the AC power source while the third means is in operation; Fifth means for detecting that the output AC phase of the power conversion device and the phase of the AC power source match within a predetermined phase difference, and instructing switching of the power source from the power conversion device to the AC power source or vice versa. A power conversion device characterized by comprising: